CN101292389B - Lithium secondary battery and nonaqueous electrolyte used therein - Google Patents

Abstract

The present invention provides a lithium secondary battery comprising a positive electrode and a negative electrode having specific compositions and physical properties, and a nonaqueous electrolytic solution containing at least one compound selected from the group consisting of the following substances in an amount of 10ppm or more, the substances including: a cyclic siloxane compound represented by formula , a fluorosilane compound represented by formula (2), a compound represented by formula (3), a compound having an S-F bond in the molecule, a nitrate, a nitrite, a monofluorophosphate, a difluorophosphate, an acetate, and a propionate. The lithium secondary battery has high capacity, long service life, and high output power. In the formula , R¹And R²Is an organic group having 1 to 12 carbon atoms, and n is an integer of 3 to 10; in the formula , R³～R⁵Is an organic group having 1 to 12 carbon atoms, x is an integer of 1 to 3, p, q and r are each an integer of 0 to 3, and 1. ltoreq. p + q + r. ltoreq.3; in the formula , R⁶～R⁸Is an organic group having 1 to 12 carbon atoms, and A is a group consisting of H, C, N, O, F, S, Si and/or P.

Description

Lithium secondary battery and non-aqueous electrolyte used therein

technical field

The present invention relates to a lithium secondary battery and a non-aqueous electrolytic solution used therein, more specifically, to a non-aqueous electrolytic solution for a lithium secondary battery containing specific components, and a non-aqueous electrolytic solution having a specific composition and physical properties capable of occluding and releasing lithium. positive and negative electrodes, and particularly lithium secondary batteries excellent in low-temperature discharge characteristics and high in capacity, long life, and high output, and nonaqueous electrolytic solutions used therein.

Background technique

In recent years, along with the miniaturization of electronic equipment, the demand for higher capacity of secondary batteries has been increasing, and lithium secondary batteries with higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries have attracted attention.

Since lithium secondary batteries are high-capacity secondary batteries, they can be used in various applications, but they are mainly used in relatively small batteries such as mobile phones, and their application to large batteries such as automobiles is expected to expand in the future. In particular, output is required for large batteries, but simply enlarging conventional small batteries is not sufficient in terms of performance. In addition, various methods of improving battery materials for increasing output have been proposed (for example, refer to Patent Documents 1 to 25, Non-Patent Document 1, etc.). However, sufficient output cannot be obtained yet, and further improvement is demanded.

Patent Document 1: JP-A-2005-071749

Patent Document 2: JP-A-2005-123180

Patent Document 3: JP-A-2001-206722

Patent Document 4: JP-A-2003-267732

Patent Document 5: JP-A-2001-015108

Patent Document 6: WO2003/34518 Publication

Patent Document 7: JP-A-11-067270

Patent Document 8: JP-A-61-168512

Patent Document 9: JP-A-6-275263

Patent Document 10: JP-A-2000-340232

Patent Document 11: JP-A-2005-235397

Patent Document 12: Japanese Unexamined Patent Publication No. 11-031509

Patent Document 13: JP-A-3-055770

Patent Document 14: JP-A-2004-071458

Patent Document 15: JP-A-2004-087459

Patent Document 16: Japanese Unexamined Patent Application Publication No. H10-270074

Patent Document 17: JP-A-2002-075440

Patent Document 18: Japanese Unexamined Patent Application Publication No. H10-270075

Patent Document 19: JP-A-8-045545

Patent Document 20: JP-A-2001-006729

Patent Document 21: Japanese Unexamined Patent Publication No. 10-050342

Patent Document 22: Japanese Unexamined Patent Publication No. 9-106835

Patent Document 23: JP-A-2000-058116

Patent Document 24: JP-A-2001-015158

Patent Document 25: JP-A-2005-306619

Non-Patent Document 1: J. Electrochem.soc., 145, L1 (1998)

Contents of the invention

The problem to be solved by the invention

The present invention has been made in view of such background technology, and an object of the present invention is to provide a lithium secondary battery with high capacity, long life, and high output even when it is made larger.

Solution to the problem

The inventors of the present invention conducted intensive studies on the above-mentioned subject, and as a result found that a high-capacity, long-term The present invention has been accomplished by providing a long-life and high-output lithium secondary battery.

That is, the present invention provides a lithium secondary battery comprising at least: an electrode group formed by sandwiching a porous membrane separator between a positive electrode and a negative electrode; non-aqueous electrolytes, and they are housed in battery casings, wherein,

The positive electrode and the negative electrode respectively form an active material layer on the current collector, and the active material layer contains an active material capable of absorbing and releasing lithium ions;

The non-aqueous electrolyte contains at least one compound selected from the following substances, and its content in all non-aqueous electrolytes is more than 10ppm, and the substances include:

A cyclic siloxane compound represented by the following general formula (1),

[chemical formula 1]

[In the general formula (1), R ¹ and R ² may be the same or different, and represent an organic group with 1 to 12 carbon atoms, and n represents an integer of 3 to 10. ]

A fluorosilane compound represented by the following general formula (2),

[chemical formula 2]

SiF _x R ³ _p R ⁴ _q R ⁵ _r (2)

[In the general formula (2), R ³ to R ⁵ may be the same or different, and represent an organic group with 1 to 12 carbon atoms, x represents an integer of 1 to 3, and p, q and r represent 0 to 3, respectively. Integer, and 1≤p+q+r≤3. ]

A compound represented by the following general formula (3),

[chemical formula 3]

[In the general formula (3), R ⁶ to R ⁸ may be the same or different, and represent an organic group with 1 to 12 carbon atoms, and A represents an organic group composed of H, C, N, O, F, S, Si and/or The group formed by P. ],as well as

Compounds with S-F bonds in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates and propionates;

And, the positive electrode is any positive electrode selected from the following positive electrode [1] to positive electrode [5]:

Positive electrode [1]: a positive electrode comprising a positive electrode active material containing manganese;

Positive electrode [2]: a positive electrode comprising a positive electrode active material having a composition represented by the following composition formula (4),

Li _x Ni _(1-yz) Co _y M _z O ₂ composition formula (4)

[In the composition formula (4), M represents at least one element selected from Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, x represents a number satisfying 0<x≤1.2, and y represents a number satisfying 0.05≤y≤0.5, and z represents a number satisfying 0.01≤z≤0.5. ];

Positive electrode [3]: a positive electrode comprising any positive electrode active material selected from the following (a) to (d),

(a) A positive electrode active material having a BET specific surface area of 0.4m ² /g to 2m ² /g

(b) Positive active material having an average primary particle size of 0.1 μm to 2 μm

(c) A positive electrode active material having a median diameter _d50 of 1 μm to 20 μm

(d) a positive electrode active material with a tap density of 1.3g/cm ³ to 2.7g/cm ³ ;

Positive electrode [4]: A positive electrode that satisfies any one of the following conditions (e) to (f),

(e) A positive electrode made by forming a positive electrode active material layer containing a positive electrode active material, a conductive material and a binder on a current collector, wherein the content of the conductive material in the positive electrode active material layer is 6% by mass to 20% by mass range

(f) A positive electrode produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector, wherein the density of the positive electrode active material layer is in the range of 1.7 g/cm ³ to 3.5 g/cm ³

(g) a positive electrode made by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on the current collector, wherein the ratio of the thickness of the positive electrode active material layer to the current collector (one period before injecting the nonaqueous electrolyte solution) The thickness of the side active material layer)/(the thickness of the current collector) is 1.6 to 20;

Positive electrode [5]: A positive electrode containing two or more positive electrode active materials with different compositions.

In addition, the present invention provides a lithium secondary battery comprising at least: an electrode group formed by sandwiching a porous film separator between a positive electrode and a negative electrode; non-aqueous electrolytes, and they are housed in battery casings, wherein,

The positive electrode and the negative electrode respectively form an active material layer on the current collector, and the active material layer contains an active material capable of absorbing and releasing lithium ions;

The non-aqueous electrolytic solution contains at least one compound selected from the following substances, and its content in all non-aqueous electrolytic solutions is more than 10 ppm, and the substance includes: the cyclic silicon oxide represented by the above general formula (1) alkane compounds, fluorosilane compounds represented by the above general formula (2), compounds represented by the above general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, Acetate and propionate;

And, the negative electrode is any negative electrode selected from the following negative electrodes [1] to negative electrodes [10]:

Negative electrode [1]: a negative electrode containing two or more carbonaceous substances with different crystallinity as the negative electrode active material;

Negative pole [2]: the negative pole that contains amorphous carbonaceous as negative electrode active material, and the interplanar spacing (d002) of (002) plane of described amorphous carbonaceous by wide-angle X-ray diffractometry is more than 0.337nm, crystallite size ( Lc) is less than 80nm, and the Raman R value defined by the ratio of the peak intensity at 1360cm ^-1 to the peak intensity at 1580cm ^-1 measured by argon ion laser Raman spectroscopy is 0.2 or more;

Negative electrode [3]: a negative electrode containing a metal oxide as the negative electrode active material, and the metal oxide contains titanium capable of occluding and releasing lithium;

Negative electrode [4]: a negative electrode containing carbonaceous material as the negative electrode active material, the circularity of the carbonaceous material is above 0.85, and the O/C value of the surface functional group is 0-0.01;

Negative electrode [5]: a negative electrode containing a hetero-orientation carbon composite as the anode active material, and the hetero-orientation carbon composite contains two or more carbonaceous substances with different orientations;

Negative electrode [6]: a negative electrode containing graphitic carbon particles as the negative electrode active material, the circularity of the graphitic carbon particles is 0.85 or more, and the interplanar distance (d002) of the (002) plane measured by wide-angle X-ray diffraction method is low At 0.337nm, the Raman R value defined by the ratio of the peak intensity at 1360cm ^-1 to the peak intensity at 1580cm ^-1 measured by argon ion laser Raman spectroscopy is 0.12-0.8;

Negative electrode [7]: a negative electrode containing the following multi-element-containing negative electrode active material (C') as the negative electrode active material, the multi-element-containing negative electrode active material (C') containing , Bi, In, Mg, Ga, Cd, Ag, Si, B, Au, Pt, Pd, and Sb lithium storage metal (A') and/or lithium storage alloy (B'), and contains C and/or N as element Z;

Negative electrode [8]: a negative electrode containing two or more negative electrode active materials with different properties as the negative electrode active material;

Negative electrode [9]: Containing a negative electrode active material with a tap density of 0.1 g/cm ³ or more and a pore volume equivalent to particles in the range of 0.01 μm to 1 μm in diameter measured by a mercury porosimeter of 0.01 mL/g or more negative electrode;

Negative pole [10]: when charged to 60% of the nominal capacity of the negative pole, the reaction resistance produced by the opposite battery of the negative pole is a negative pole below 500Ω.

In addition, the present invention provides a lithium secondary battery comprising at least: an electrode group formed by sandwiching a positive electrode and a negative electrode with a porous membrane separator; and a non-aqueous solvent containing a lithium salt. water electrolyte, and they are contained in the battery casing, wherein,

The positive electrode and the negative electrode respectively form an active material layer on the current collector, and the active material layer contains an active material capable of absorbing and releasing lithium ions;

The non-aqueous electrolytic solution contains at least one compound selected from the following substances, and its content in all non-aqueous electrolytic solutions is more than 10 ppm, and the substance includes: the cyclic silicon oxide represented by the above general formula (1) alkane compounds, fluorosilane compounds represented by the above general formula (2), compounds represented by the above general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, Acetate and propionate;

And, the non-aqueous electrolyte is an electrolyte that satisfies any condition selected from the following electrolyte [1] to electrolyte [9]:

Electrolyte [1]: The nonaqueous solvent constituting the electrolyte is a mixed solvent containing at least ethylene carbonate, and the ratio of ethylene carbonate to the total amount of nonaqueous solvent is 1% by volume to 25% by volume;

Electrolyte [2]: The nonaqueous solvent constituting the electrolyte contains at least one asymmetric chain carbonate, and the proportion of the asymmetric chain carbonate in all nonaqueous solvents is 5% to 90% by volume %;

Electrolyte [3]: the non-aqueous solvent constituting the electrolyte contains at least one chain carboxylate;

Electrolyte [4]: The non-aqueous solvent constituting the electrolyte contains a solvent with a flash point above 70°C, and its content is above 60% by volume of all non-aqueous solvents;

Electrolyte [5]: containing LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and/or lithium bis(oxalato)borate as the lithium salt constituting the electrolyte;

Electrolyte [6]: The lithium salt constituting the electrolyte is a fluorine-containing lithium salt, and contains 10 ppm to 300 ppm of hydrogen fluoride (HF) in all non-aqueous electrolytes;

Electrolyte [7]: the electrolyte contains vinylene carbonate, and the content of the vinylene carbonate is in the range of 0.001% by mass to 3% by mass of the total mass of the electrolyte;

Electrolyte [8]: The electrolyte also contains compounds selected from the following general formula (4), heterocyclic compounds containing nitrogen and/or sulfur, cyclic carboxylates, and fluorine-containing cyclic carbonates. at least one compound, the content of which is in the range of 0.001% by mass to 5% by mass in the entire non-aqueous electrolyte solution,

[chemical formula 4]

[In general formula (4), R ⁹ to R ¹² may be the same or different, and represent a group composed of at least one element selected from H, C, N, O, F, S, and P. ];

Electrolyte solution [9]: The electrolyte solution also contains an overcharge preventing agent.

Among the above-mentioned secondary batteries, a secondary battery having any one of properties selected from the following (1) to (3) is particularly preferred,

(1) The area ratio of the total electrode area of the positive electrode to the surface area of the case of the secondary battery is 20 times or more;

(2) The DC resistance component of the secondary battery is below 20 milliohms (mΩ);

(3) The battery element housed in one battery case of the secondary battery has a capacitance of 3 ampere hours (Ah) or more.

In addition, the present invention provides a lithium secondary battery comprising at least: an electrode group formed by sandwiching a positive electrode and a negative electrode with a porous membrane separator; and a non-aqueous solvent containing a lithium salt. water electrolyte, and they are contained in the battery casing, wherein,

The positive electrode and the negative electrode respectively form an active material layer on the current collector, and the active material layer contains an active material capable of absorbing and releasing lithium ions;

The non-aqueous electrolytic solution contains at least one compound selected from the following substances, and its content in all non-aqueous electrolytic solutions is more than 10 ppm, and the substance includes: the cyclic silicon oxide represented by the above general formula (1) alkane compounds, fluorosilane compounds represented by the above general formula (2), compounds represented by the above general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, Acetate and propionate;

And, the secondary battery has any one of properties selected from the following structure [1] to structure [6]:

Structure [1]: the area ratio of the sum of the electrode areas of the positive electrode to the surface area of the case of the secondary battery is 20 times or more;

Structure [2]: The DC resistance component of the secondary battery is below 20 milliohms (mΩ);

Structure [3]: The battery element housed in one battery case of the secondary battery has a capacitance of 3 ampere hours (Ah) or more;

Structure [4]: The current collectors of the positive and negative electrodes of the secondary battery are respectively made of metal materials, and the metal materials of the current collectors and the conductors for taking the current to the outside are welded by slot welding, high Welding by any method of frequency welding or ultrasonic welding;

Structure [5]: the casing of the secondary battery is made of aluminum or aluminum alloy;

Structure [6]: The case material forming the above-mentioned battery case of the secondary battery is a case material in which at least a part of the inner surface side of the battery includes a sheet formed using a thermoplastic resin, and while housing the battery pack, The battery pack can also be sealed by heat-sealing the thermoplastic resin layers to each other.

In addition, the present invention also provides a non-aqueous electrolytic solution for a secondary battery, the non-aqueous electrolytic solution at least includes a non-aqueous solvent and a lithium salt, wherein,

The non-aqueous electrolytic solution contains at least one compound selected from the following substances, and its content in all non-aqueous electrolytic solutions is more than 10 ppm, and the substance includes: the cyclic silicon oxide represented by the above general formula (1) alkane compounds, fluorosilane compounds represented by the above general formula (2), compounds represented by the above general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, Acetate and propionate;

And, the non-aqueous electrolytic solution satisfies any condition selected from the following electrolytic solutions [1] to electrolytic solutions [9]:

Electrolyte [1]: The nonaqueous solvent constituting the electrolyte is a mixed solvent containing at least ethylene carbonate, and the ratio of ethylene carbonate to the total amount of nonaqueous solvent is 1% by volume to 25% by volume;

Electrolyte [2]: The nonaqueous solvent constituting the electrolyte contains at least one asymmetric chain carbonate, and the proportion of the asymmetric chain carbonate in all nonaqueous solvents is 5% to 90% by volume %;

Electrolyte [3]: the non-aqueous solvent constituting the electrolyte contains at least one chain carboxylate;

Electrolyte [4]: The non-aqueous solvent constituting the electrolyte contains a solvent with a flash point of 70°C or higher, and its content is more than 60% by volume of the total non-aqueous solvent;

Electrolyte [5]: containing LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and/or lithium bis(oxalato)borate as the lithium salt constituting the electrolyte;

Electrolyte [6]: The lithium salt constituting the electrolyte is a fluorine-containing lithium salt, and contains 10 ppm to 300 ppm of hydrogen fluoride (HF) in all non-aqueous electrolytes;

Electrolyte [7]: the electrolyte contains vinylene carbonate, and the content of the vinylene carbonate is in the range of 0.001% by mass to 3% by mass of the total mass of the electrolyte;

Electrolyte solution [8]: the electrolyte solution also contains at least A compound whose content in the entire non-aqueous electrolyte is in the range of 0.001% by mass to 5% by mass;

Electrolyte solution [9]: The electrolyte solution also contains an overcharge preventing agent.

The effect of the invention

According to the present invention, it is possible to provide a lithium secondary battery particularly excellent in low-temperature discharge characteristics, and various aspects of the invention to be described later can exhibit, for example, the following effects.

Positive pole [1]:

According to the present invention, since a long life and high output can be obtained with less expensive materials, it is possible to provide a lithium secondary battery particularly suitable for large batteries such as automobiles.

Positive electrode [2]:

According to the present invention, it is possible to provide a high-capacity, long-life, and high-output lithium secondary battery, and also provide a lithium secondary battery particularly suitable for large batteries such as automobiles.

Positive electrode [3]:

According to the present invention, a long-life and high-output lithium secondary battery can be obtained, and therefore, a lithium secondary battery particularly suitable for large batteries such as automobile applications can be provided.

Positive pole [4]:

According to the present invention, since a high-output lithium secondary battery can be obtained, it is possible to provide a lithium secondary battery particularly suitable for a large battery such as an automobile.

Positive electrode [5]:

According to the present invention, it is possible to obtain a lithium secondary battery with high capacity, long life, high output, and suppression of reduction in battery capacity and output due to repeated charge and discharge of the battery (excellent in repeated charge and discharge characteristics (cycle characteristics)) , and therefore it is possible to provide a lithium secondary battery which is particularly suitable for a large battery such as an automobile application.

Negative pole [1]:

According to the present invention, it is possible to provide a lithium secondary battery particularly suitable as a large-scale battery, which can maintain the effect of improving the cycle characteristics, and can maintain high output characteristics from the beginning to the end of the cycle at the same time, even after charging and discharging cycles. After the final degradation, the output characteristics under high power can also be maintained.

Negative pole [2]:

According to the present invention, it is possible to provide a lithium secondary battery having excellent short-time high current density charge and discharge characteristics.

Negative pole [3]:

According to the present invention, it is possible to provide a lithium secondary battery that has a small output resistance and can utilize energy efficiently.

Negative pole [4]:

According to the present invention, a lithium secondary battery having improved high-temperature storage resistance at a low depth of charge can be provided.

Negative electrode [5]:

According to the present invention, it is possible to provide a lithium secondary battery capable of maintaining good performance even when charging and discharging are repeated for a long time at a low depth of charge.

Negative electrode [6]:

According to the present invention, it is possible to provide a lithium secondary battery that recovers output quickly from a low output state at low temperature.

Negative electrode [7]:

According to the present invention, it is possible to provide a lithium secondary battery having a large capacity even when it is made larger and having good charge acceptance.

Negative electrode [8]:

According to the present invention, a lithium secondary battery having excellent cycle characteristics and low-temperature output can be provided.

Negative pole [9] [10]:

According to the present invention, it is possible to provide a lithium secondary battery that has a large cycle retention rate when the battery is made larger, and can achieve a good battery life, and can achieve high output even after a charge-discharge cycle test, or both. .

Electrolyte[1]:

According to the present invention, the low-temperature characteristics of the non-aqueous electrolyte secondary battery can be greatly improved, and more specifically, the low-temperature characteristics can be improved without deteriorating the cycle characteristics and storage characteristics.

Electrolyte [2]:

According to the present invention, it is possible to provide a non-aqueous electrolytic solution for a secondary battery in which both cycle characteristics and low-temperature characteristics are greatly improved, and a secondary battery using the non-aqueous electrolytic solution excellent in the above-mentioned performances.

Electrolyte [3]:

According to the present invention, it is possible to provide a non-aqueous electrolytic solution for a secondary battery and a secondary battery in which low-temperature output characteristics are greatly improved.

Electrolyte [4]:

According to the present invention, the following non-aqueous electrolytic solution for secondary battery and secondary battery can be provided: although the non-aqueous electrolytic solution for secondary battery is due to the evaporation of solvent, salt is precipitated, or the flash point is lowered, and the internal The composition of the electrolyte solution has few problems when a large amount of low-viscosity solvent is contained, such as that the pressure is easy to rise, but it can still maintain high low-temperature characteristics and output characteristics.

Electrolyte [5]:

According to the present invention, it is possible to provide a non-aqueous electrolytic solution for a secondary battery and a secondary battery that have greatly improved output characteristics and are excellent in high-temperature storage characteristics and cycle characteristics.

Electrolyte [6]:

According to the present invention, it is possible to provide a non-aqueous electrolytic solution for secondary batteries that is excellent in high-temperature storage characteristics and cycle characteristics, and that has greatly improved output characteristics.

Electrolyte [7]:

According to the present invention, it is possible to provide a secondary battery in which both cycle characteristics and low-temperature characteristics are greatly improved.

Electrolyte [8]:

According to the present invention, it is possible to provide a non-aqueous electrolytic solution for a secondary battery and a secondary battery that have greatly improved low-temperature discharge characteristics and are excellent in high-temperature storage characteristics and cycle characteristics.

Electrolyte [9]:

According to the present invention, it is possible to provide a secondary battery that satisfies both high rate characteristics and safety during overcharge.

Structure [1]～[5]:

According to the present invention, a lithium secondary battery with high capacity, long life, high output, and high safety during overcharge can be obtained. Therefore, a lithium secondary battery particularly suitable for large batteries such as automobiles can be provided.

Structure [6]:

According to the present invention, a high-capacity, long-life, high-output lithium secondary battery with low gas generation and high safety even when overcharged can be obtained. Therefore, it is possible to provide a lithium secondary battery that is particularly suitable for, for example, a large battery such as an automobile application. Lithium secondary battery.

Detailed ways

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of embodiments of the present invention, and the present invention is not limited to these specific contents unless the gist thereof is exceeded.

The lithium secondary battery of the present invention at least includes: an electrode group formed by sandwiching a porous membrane separator between the positive electrode and the negative electrode, and a non-aqueous electrolytic solution formed by containing lithium salt in a non-aqueous solvent, and they are contained in the battery enclosure, in which,

The positive electrode and the negative electrode respectively form an active material layer on the current collector, and the active material layer contains an active material capable of absorbing and releasing lithium ions;

The non-aqueous electrolytic solution contains at least one compound selected from the following substances (hereinafter referred to as "specific compounds"), and its content in all non-aqueous electrolytic solutions is more than 10ppm, and the substances include: the above-mentioned Cyclic siloxane compounds represented by the general formula (1), fluorosilane compounds represented by the above general formula (2), compounds represented by the above general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites , monofluorophosphate, difluorophosphate, acetate and propionate;

Also, the positive electrode, negative electrode, electrolyte solution or battery structure satisfies specific conditions.

Next, the lithium secondary battery of the present invention will be described in more detail.

<positive pole>

Next, the positive electrode used in the lithium secondary battery of the present invention will be described.

The positive electrode used in the present invention is not particularly limited as long as it forms an active material layer containing an active material capable of occluding and releasing lithium ions. The positive electrode is preferably selected from the following positive electrodes [1] to positive electrodes [5]. Any positive pole of :

Positive electrode [1]: a positive electrode comprising a positive electrode active material containing manganese;

Positive electrode [2]: a positive electrode comprising a positive electrode active material having a composition represented by the following composition formula (4),

Li _x Ni _(1-yz) Co _y M _z O ₂ composition formula (4)

[In the composition formula (4), M represents at least one element selected from Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, x represents a number satisfying 0<x≤1.2, and y represents a number satisfying 0.05<y≤0.5, and z represents a number satisfying 0.01≤z≤0.5. ];

Positive electrode [3]: a positive electrode comprising any positive electrode active material selected from the following (a) to (d),

(a) A positive electrode active material having a BET specific surface area of 0.4m ² /g to 2m ² /g

(b) Positive active material having an average primary particle size of 0.1 μm to 2 μm

(c) A positive electrode active material having a median diameter _d50 of 1 μm to 20 μm

(d) a positive electrode active material with a tap density of 1.3g/cm ³ to 2.7g/cm ³ ;

Positive electrode [4]: A positive electrode that satisfies any one of the following conditions (e) to (f),

(e) The positive electrode is a positive electrode made by forming a positive electrode active material layer containing a positive electrode active material, a conductive material and a binding agent on a current collector, wherein the content of the conductive material in the positive electrode active material layer is 6% by mass to 20% by mass range

(f) The positive electrode is a positive electrode produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector, wherein the density of the positive electrode active material layer is 1.7 g/cm ³ to 3.5 g/cm ³ range

(g) The positive electrode is a positive electrode made by forming a positive electrode active material layer containing a positive electrode active material and a binder on the current collector, wherein the ratio of the thickness of the positive electrode active material layer to the current collector (injection of the non-aqueous electrolyte The value of the thickness of the active material layer on one side)/(the thickness of the current collector) is in the range of 1.6 to 20;

Positive electrode [5]: A positive electrode containing two or more positive electrode active materials with different compositions.

Next, first, a positive electrode generally used in the lithium secondary battery of the present invention will be described.

[Positive electrode active material]

The positive electrode active material generally used in the positive electrode will be described below.

[[composition]]

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. A substance containing lithium and at least one transition metal is preferable, and examples thereof include lithium-transition metal composite oxides and lithium-containing transition metal phosphate compounds.

As the transition metal of the lithium-transition metal composite oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable, and specific examples include lithium-cobalt composite oxides such as LiCoO ₂ and lithium-cobalt composite oxides such as LiNiO ₂ . - Nickel composite oxides; LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO ₃ and other lithium-manganese composite oxides; Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg , Ga, Zr, Si, and other metals instead of a part of the transition metal atoms forming the main body of these lithium-transition metal composite oxides. Specific examples of alternative substances include LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O ₄ etc.

The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples include LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Iron phosphate such as LiFeP ₂ O ₇ ; Cobalt phosphate such as LiCoPO ₄ ; Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and others A metal is used instead of a part of the transition metal atoms forming the main body of these transition metal phosphate compounds containing lithium, and the like.

[[Cladding]]

In addition, it is preferable that a substance having a composition different from that of the positive electrode active material of the core adheres to the surface of these positive electrode active materials. Examples of substances adhering to the surface (hereinafter simply referred to as "surface adhering substances") include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide. ; Lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, aluminum sulfate and other sulfates; lithium carbonate, calcium carbonate, magnesium carbonate and other carbonates.

These surface attachment substances can be attached to the surface of the positive electrode active material by the following methods, which include: for example, dissolving or suspending the surface attachment substances in a solvent, then impregnating them into the positive electrode active material and drying them; making the surface A method in which the attachment substance precursor is dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and then reacted by heating or the like; a method in which the surface attachment substance is added to the positive electrode active material precursor and simultaneously sintered, etc.

As the amount of surface-attached substances, its lower limit is preferably more than 0.1ppm, more preferably more than 1ppm, more preferably more than 10ppm with respect to the positive electrode active material by mass; its upper limit is preferably less than 20%, more preferably less than 10% , and more preferably 5% or less. The oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material can be inhibited by the surface attachment substance, thereby improving the battery life, but when the amount of attachment is too small, the effect cannot be fully exhibited, and when it is too much, due to hindering the entry and exit of lithium ions, Therefore, the impedance sometimes increases.

[[shape]]

The particle shape of the positive electrode active material in the present invention can use block shape, polyhedron shape, spherical shape, ellipsoidal shape, plate shape, needle shape, columnar shape etc. used in the past, among them, preferred primary particle aggregates and forms secondary particle, and the two The shape of the secondary particles is spherical or ellipsoidal. In general, the active material in the electrode expands and shrinks as the electrochemical element is charged and discharged, and thus degradation of the active material due to this stress, such as destruction of the active material or interruption of the conductive path, tends to occur. Therefore, it is preferable to agglomerate primary particles to form secondary particles rather than single-particle active material with only primary particles, because the formation of secondary particles can relieve the stress of expansion and contraction, thereby preventing deterioration. In addition, spherical or ellipsoidal particles are preferred over plate-like equiaxially oriented particles, because spherical or ellipsoidal particles have less orientation during electrode molding and less expansion and contraction of the electrode during charging and discharging, and in It is also easy to mix uniformly with the conductive agent when making electrodes.

[[Tap Density]]

The tap density of the positive electrode active material is usually 1.3 g/cm ³ or higher, preferably 1.5 g/cm ³ or higher, more preferably 1.6 g/cm ³ or higher, and most preferably 1.7 g/cm ³ or higher. If the tap density of the positive electrode active material is lower than the above-mentioned lower limit, then when forming the positive electrode active material layer, the amount of dispersion medium required increases, and the necessary amount of conductive material or binder increases simultaneously, and the positive electrode active material is in the positive electrode active material layer. The filling rate of the battery is restricted, and the battery capacity is sometimes restricted. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. Generally speaking, the larger the tap density is, the more preferable, there is no special upper limit, but if the tap density is too large, the diffusion of lithium ions in the positive electrode active material layer with the non-aqueous electrolyte as the medium becomes a factor determining the speed, and the negative The element Z used in the negative electrode active material of the negative electrode [7] of the lithium secondary battery of the present invention is contained in the lithium occlusion material (F), and the occlusion metal (A) and/or lithium occlusion alloy (B') and The mass ratio of the carbonaceous substance (E') is usually 20/80 or more, preferably 50/50 or more, more preferably 80/20 or more, particularly preferably 90/10 or more, and preferably 99.9/0.1 or less, more preferably 99/1 or less, particularly preferably 98/2 or less. If it exceeds the above range, the effect of having the carbonaceous substance (E') may not be obtained, and if it is below the above range, the effect of increasing the capacity per unit mass may become small. Preferably, the occlusion metal (A) and/or lithium occlusion alloy (B′) is 20% by mass or more relative to the total element Z external lithium occlusion substance (F).

Since the charge characteristics tend to decrease in some cases, the tap density is usually 2.9 g/cm ³ or less, preferably 2.7 g/cm ³ or less, more preferably 2.5 g/cm ³ or less.

In the present invention, the tap density is defined as follows: the sample is dropped into a 20 cm ³ tapping container (tapping cell) through a sieve with an aperture of 300 μm. Tap densor manufactured by the company was vibrated 1000 times with a stroke length of 10 mm, and the density obtained from the volume at that time and the weight of the sample was taken as the tap density.

[[Median particle size d ₅₀ ]]

The median diameter _d50 of the particles of the positive electrode active material (when the primary particles are aggregated to form secondary particles, the secondary particle diameter) is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and most preferably 0.1 μm or more. 3 μm or more, and its upper limit is usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, most preferably 15 μm or less. If the median particle diameter _d50 is lower than the above-mentioned lower limit, a product with a high tap density may not be obtained, and if it exceeds the upper limit, since the diffusion of lithium in the particles takes time, the performance of the battery may sometimes decrease, or the resulting battery may be damaged. Streaks and other problems occur when the active material and conductive agent or binder are slurried in a solvent and then coated into a film. Here, by mixing two or more positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of producing the positive electrode can be further improved.

In addition, the median diameter _d50 in the present invention can be measured using a known laser diffraction/scattering type particle size distribution analyzer. LA-920 manufactured by HORIBA was used as a particle size distribution meter, and as a dispersion medium used in the measurement, 0.1 mass % sodium hexametaphosphate aqueous solution was used, ultrasonic dispersion was carried out for 5 minutes, and the measurement refractive index was set to 1.24 for measurement.

[[average primary particle size]]

When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.08 μm or more, most preferably 0.1 μm or more, and usually 3 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and most preferably 0.6 μm or less. When the average primary particle size exceeds the above upper limit, it is difficult to form spherical secondary particles, which adversely affects the powder fillability, or the specific surface area is greatly reduced, and therefore battery performance such as output characteristics may decrease. On the contrary, if the average primary particle diameter is less than the above-mentioned lower limit, problems such as poor charge-discharge reversibility may occur due to incomplete crystallization.

In addition, the primary particle size can be measured by observation using a scanning electron microscope (SEM). Specifically, it is obtained by the following method: in a photograph with a magnification of 10,000 times, for any 50 primary particles, the longest value of the slice generated by the left and right boundary lines of the primary particles on a straight line in the horizontal direction is obtained, and the maximum value is obtained. average value.

[[BET specific surface area]]

The BET specific surface area of the positive electrode active material provided for the lithium secondary battery of the present invention is usually 0.2 m ² /g or more, preferably 0.3 m ² /g or more, more preferably 0.4 m ² /g or more, and the upper limit is usually 4.0 m ² /g or less, preferably 2.5 m ² /g or less, more preferably 1.5 m ² /g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to decrease, and if the BET specific surface area is larger than this range, it is difficult to increase the tap density, and problems may easily occur in coating properties when forming a positive electrode active material.

The BET specific surface area is defined as the following value: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 150°C for 30 minutes under nitrogen flow, and then adjusted to the nitrogen relative The value measured by the nitrogen adsorption BET 1-point method using the gas flow method for a nitrogen-helium mixed gas with a relative pressure value of 0.3 at atmospheric pressure.

[[Manufacturing method]]

As a method for producing the positive electrode active material, a common method for producing an inorganic compound is used. In particular, when producing a spherical or ellipsoidal active material, various methods can be considered, for example, the following method can be cited: a transition metal raw material such as a transition metal nitrate, a transition metal sulfate, and a raw material of other elements used as needed Dissolve or pulverize and disperse in solvents such as water, adjust the pH while stirring, make and obtain spherical precursors, dry them as needed, add Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and sinter at high temperature to form A method of obtaining an active material; dissolving or pulverizing raw materials of transition metals such as transition metal nitrates, transition metal sulfates, transition metal hydroxides, transition metal oxides, and other elements used as needed in a solvent such as water , and then dry it by spray dryer to form a spherical or ellipsoidal precursor, and then add Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ to it, and sinter at a high temperature to obtain an active material. ; and transition metal raw materials such as transition metal nitrates, transition metal sulfates, transition metal hydroxides, transition metal oxides and Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ and other elements used as required A method in which the substance is dissolved or pulverized and dispersed in a solvent such as water, and then dried and shaped by a spray dryer to form a spherical or ellipsoidal precursor, and then sintered at a high temperature to obtain an active material.

[Structure of positive electrode]

Next, the structure of the positive electrode used in the present invention will be described.

[[Electrode structure and fabrication method]]

The positive electrode used in the lithium secondary battery of the present invention is produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be performed according to a usual method. That is, the positive electrode active material and the binder, as well as the conductive material and thickener used as required, are dry mixed, made into a sheet, and then the obtained sheet is pressed and bonded on the positive electrode collector, or the These materials are dissolved or dispersed in a liquid medium to form a slurry, and then the slurry is coated on the positive electrode collector and dried, thereby forming a positive electrode active material layer on the current collector, thereby obtaining a positive electrode. .

In the present invention, the content of the positive electrode active material in the positive electrode active material layer is usually 10% by mass or more, preferably 30% by mass or more, particularly preferably 50% by mass or more. In addition, the upper limit thereof is usually 99.9% by mass or less, preferably 99% by mass or less. When the content of the positive electrode active material powder in the positive electrode active material layer is too low, the capacitance may become insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient. In addition, one type of positive electrode active material may be used alone, or two or more positive electrode active materials having different compositions or different powder properties may be used in combination in any combination and ratio.

[[Compaction]]

In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably compacted using a manual press, a roll press, or the like. The lower limit of the density of the positive electrode active material layer is preferably 1 g/cm ^or more, more preferably 1.5 g/cm ^or more, even more preferably 2 g/cm ^or more, and the upper limit is preferably 4 g/cm ^or less, more preferably 3.5 g /cm ³ or less, more preferably 3 g/cm ³ or less. If this range is exceeded, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector/active material interface decreases, and in particular, the charge-discharge characteristics at high current densities sometimes decrease. Moreover, if it is less than this range, the electrical conductivity between active materials will fall, and battery impedance may increase.

[[Conductive Material]]

As the conductive material, known conductive materials can be used arbitrarily. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. One of these substances may be used alone, or two or more of them may be used in any combination and ratio.

The use ratio of the conductive material in the positive electrode active material layer is usually more than 0.01% by weight, preferably more than 0.1% by weight, more preferably more than 1% by weight, and the upper limit is usually less than 50% by weight, preferably less than 30% by weight, more preferably Preferably it is 15% by weight or less. If the content is less than this range, the conductivity may be insufficient. On the contrary, if the content is higher than the range, the battery capacity may decrease.

[[Binder]]

The binder used in the production of the positive electrode active material layer is not particularly limited. When using the coating method, any material can be dissolved or dispersed in the liquid medium used in the production of the electrode. As a specific example, Polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose and other resin polymers; SBR (styrene-butadiene rubber ), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber and other rubber-like polymers; styrene-butadiene-styrene block copolymer Or its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or its addition Thermoplastic elastomeric polymers such as hydrogen compounds; soft resinous polymers such as syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer, etc. ; Polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymer and other fluorine polymers; ion conductivity with alkali metal ions (especially lithium ions) Polymer composition, etc. In addition, these substances may be used individually by 1 type, and may be used combining 2 or more types by arbitrary combinations and ratios.

The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60% by mass or less, more preferably Preferably it is 40% by mass or less, most preferably 10% by mass or less. If the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained, the mechanical strength of the positive electrode is insufficient, and battery performance such as cycle characteristics deteriorates. On the other hand, if the ratio of the binder is too high, it sometimes leads to a decrease in battery capacity or conductivity.

[[liquid medium]]

The liquid medium used to form the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, conductive agent, binder and, if necessary, a thickener. Aqueous solvents and organic solvents can be used. any of the solvents.

As an aqueous medium, water, the mixed solvent of alcohol, and water, etc. are mentioned, for example. Examples of organic solvents include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. ; Methyl acetate, methyl acrylate and other esters; Diethylenetriamine, N, N-dimethylaminopropylamine and other amines; Diethyl ether, propylene oxide, tetrahydrofuran (THF) and other ethers; N-methyl Amides such as pyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphonamide and dimethyl sulfoxide, etc.

In particular, when using an aqueous solvent, it is preferable to form a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). Thickeners are generally used to adjust the viscosity of slurry. The thickener is not particularly limited, and specifically, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and their salt etc. These may be used individually by 1 type, and may combine and use 2 or more types by arbitrary combinations and ratios. In addition, when adding a thickener, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is usually 5% by mass or less, preferably 3% by mass or less, more preferably in the range of 2% by mass or less. If it is less than this range, coatability may fall remarkably. On the other hand, if this range is exceeded, the proportion of the active material in the positive electrode active material layer decreases, which may cause problems such as a decrease in battery capacity or an increase in impedance between positive electrode active materials.

[[Collector]]

The material of the positive electrode current collector is not particularly limited, and known materials can be used arbitrarily. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Among them, metal materials are preferable, and aluminum is particularly preferable.

As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, metal film, expanded alloy (Ekispand Metal), perforated metal, foamed metal, etc.; Below, carbon plates, carbon thin films, carbon cylinders, etc. are mentioned. Among these, metal thin films are preferable. In addition, the film can also be properly formed into a network. The thickness of the film is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than this range, the required strength as a current collector may be insufficient. On the contrary, when the film is thicker than this range, the handleability may be impaired.

The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, and (the thickness of the active material layer on the side before injecting the nonaqueous electrolyte)/(thickness of the current collector) is preferably 150 or less, more preferably 20 or less , is most preferably 10 or less, and its lower limit is preferably 0.1 or more, more preferably 0.4 or more, and most preferably 1 or more. If this range is exceeded, the current collector may generate heat due to Joule heat during high current density charge and discharge. If it is less than this range, the volume ratio of the current collector to the positive electrode active material may increase and the capacity of the battery may decrease.

[[Electrode Area]]

When using the nonaqueous electrolytic solution of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery case from the viewpoint of high output and improved stability at high temperature. Specifically, the total electrode area of the above-mentioned positive electrode is preferably 15 times or more, more preferably 40 times or more, in terms of area ratio with respect to the surface area of the casing of the secondary battery. The outer surface area of the housing refers to the total area of the housing part filled with the power generating elements except the protruding part of the terminal calculated from the dimensions of length, width and thickness in the case of a square shape with a bottom. In the case of a bottomed cylindrical shape, it is a geometrical surface area obtained by approximating the housing portion filled with the power generating element except for the protruding portion of the terminal as a cylinder. The sum of the electrode areas of the so-called positive pole is combined with the composite material layer (composite material) that contains the negative active material. ) The geometric surface area of the positive electrode cladding material layer facing each other refers to the sum of the areas of the respective surfaces in the structure in which the positive electrode cladding material layer is formed on both sides of the current collector foil.

[[Discharge capacity]]

When using the non-aqueous electrolytic solution for secondary batteries of the present invention, if the capacitance (capacity when the battery is discharged from a fully charged state to a discharged state) of the battery elements contained in the battery case of one secondary battery is 3 If the ampere-hour (Ah) or more is greater, the effect of improving the low-temperature discharge characteristics becomes greater, which is preferable.

Therefore, the positive plate is preferably designed to have a discharge capacity of not less than 3 ampere hours (Ah) and less than 20 Ah, more preferably not less than 4 Ah and less than 10 Ah, when fully charged. If it is less than 3Ah, when a large current is taken out, the voltage drop due to the electrode reaction impedance becomes large, and the power efficiency may deteriorate. When it is above 20Ah, although the electrode reaction impedance becomes smaller and the power efficiency becomes better, the temperature distribution caused by the internal heating of the battery during pulse charging and discharging is large, and the durability of repeated charging and discharging is poor. When intense heat is generated, the heat release efficiency also deteriorates, and the internal pressure rises to cause the purge valve to operate (valve operation), and the possibility of the battery contents to be ejected violently to the outside (rupture) may increase.

[[Thickness of positive plate]]

The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the lower limit of the thickness of the cladding material layer after subtracting the thickness of the metal foil of the core material on one side of the current collector is preferably 10 μm or more, More preferably, it is 20 μm, and the upper limit thereof is preferably 200 μm or less, more preferably 100 μm or less.

<positive pole[1]>

Next, the positive electrode [1] "positive electrode containing a positive electrode active material containing manganese" used in the lithium secondary battery of the present invention will be described.

[Positive electrode active material of positive electrode [1]]

Next, the positive electrode active material used in the positive electrode [1] will be described.

[[composition]]

The positive electrode active material contains a transition metal capable of electrochemically occluding and releasing lithium ions. In the present invention, a positive electrode active material containing manganese is used as at least a part of the transition metal. It is preferable to further contain lithium, and it is more preferable to contain a composite oxide of lithium and manganese.

The manganese-containing positive electrode active material is not particularly limited, but is preferably a positive electrode active material having a composition represented by the following composition formula (5).

Li _x Mn _(1-y) M ¹ _y O ₂ composition formula (5)

[In the composition formula (5), ^M1 represents at least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (5), M ¹ is particularly preferably Ni, Co, and Fe, and x is particularly preferably 0.2≤x≤1.15, and y is particularly preferably 0.1≤y≤0.7. As a specific example of the substance having the composition represented by composition formula (5), LiMn _0.5 Ni _0.5 O ₂ is mentioned, for example.

In addition, a positive electrode active material in which M ¹ is Ni and has a composition represented by the following composition formula (6) is particularly preferable.

Li _x Mn _(1-yz) Ni ¹ _y M ² _z O ₂ composition formula (6)

[In the composition formula (6), M represents at ^least one element selected from Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents a number satisfying 0<x≤1.2, y represents the number satisfying 0.05≤y≤0.8, and z represents the number satisfying 0.01≤z≤0.5].

In the composition formula (6), ^M2 is particularly preferably Co, Al, Fe, Mg, x is particularly preferably 0.2≤x≤1.15, y is particularly preferably 0.1≤y≤0.7, z is particularly preferably 0.1≤z≤0.7, y+z Particular preference is given to 0.2≦y+z≦0.7. Specific examples of the substance having a composition represented by the composition formula (6) include, for example, LiMn _0.33 Ni _0.33 Co _0.33 O ₂ and the like.

As the positive electrode active material containing manganese, a positive electrode active material having a composition represented by the following composition formula (7) is preferable.

Li _x Mn _(2-y) M ³ _y O ₄ composition formula (7)

[In the composition formula (7), M represents at ^least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (7), M ³ is particularly preferably Ni, Co, Al, and Mg, and x is particularly preferably 0.05≤x≤1.15, and y is particularly preferably 0.1≤y≤0.7. Specific examples of the substance having the composition represented by the composition formula (7) include, for example, LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O ₄ , and the like.

[[Cladding]]

In addition, it is preferable to use a positive electrode active material having a composition different from that of the above-mentioned manganese-containing positive electrode active material adhered to the surface of the positive electrode active material. The type, method of adhesion, amount of adhesion, etc. of the surface adhesion substance are the same as above.

[[shape]]

The particle shape of the positive electrode active material is the same as above.

[[Tap Density]]

The tap density of this positive electrode active material is the same as above.

[[Median particle size d ₅₀ ]]

The median diameter d ₅₀ (the diameter of the secondary particle when the primary particles are aggregated to form secondary particles) of the particles of the positive electrode active material is the same as above.

[[average primary particle size]]

When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is the same as described above.

[[BET specific surface area]]

The BET specific surface area of the positive electrode active material is the same as above.

[[Manufacturing method]]

As a method for producing the positive electrode active material, a common method for producing an inorganic compound is used. In particular, when producing a spherical or ellipsoidal active material, various methods can be considered. For example, the following method can be cited: dissolving or pulverizing raw materials of manganese such as manganese nitrate and manganese sulfate and other elements used as needed in In a solvent such as water, adjust the pH while stirring, prepare and obtain a spherical precursor, dry it if necessary, add a Li source such as LiOH, Li ₂ CO ₃ , LiNO _{3 ,} and sinter at a high temperature to obtain an active material. Dissolve or pulverize manganese raw materials such as manganese nitrate, manganese sulfate, manganese oxide, basic manganese hydroxide, and other elements used as needed in solvents such as water, and then dry them into shape with a spray dryer, etc. , making a spherical or ellipsoidal precursor, then adding Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ to it, and sintering at a high temperature to obtain an active material; and manganese nitrate, manganese sulfate, manganese oxide, Manganese raw materials such as basic manganese hydroxide, Li sources such as LiOH, Li ₂ CO ₃ , and LiNO ₃ , and raw materials of other elements used as needed are dissolved or pulverized in a solvent such as water, and then dried by a spray dryer or the like. It is a method of drying and forming a spherical or ellipsoidal precursor, and then sintering it at a high temperature to obtain an active material.

The positive electrode active material in the present invention can use this positive electrode active material containing manganese alone, also can use this positive electrode active material containing manganese and one or more with this positive electrode active material composition containing manganese in any combination and ratio Positive electrode active materials with different or different powder properties. As a preferred combination at this time, a combination of a positive electrode active material containing manganese and LiNiO ₂ or part of Ni replaced by other transition metals; or a positive electrode active material containing manganese and LiCoO ₂ or part of Co replaced by A combination of substances obtained by substitution of other transition metals. In addition, as a particularly preferred combination, the combination of the positive electrode active material represented by the composition formula (5) to (7) and LiNiO ₂ or a part of Ni replaced by other transition metals; or the composition formula (5) A combination of the positive electrode active material represented by ~ (7) and LiCoO ₂ or a part of Co replaced by other transition metals. The positive electrode active material containing manganese, especially the positive electrode active material represented by the composition formulas (5) to (7) is preferably 30% by mass or more, more preferably 50% by mass or more of the total positive electrode active material. If the ratio of the positive electrode active material represented by the composition formulas (5) to (7) is reduced, the cost of the positive electrode may not be reduced.

[Structure of the positive electrode of the positive electrode [1]]

Next, the structure of the positive electrode used in the positive electrode [1] will be described.

Electrode structure and manufacturing method in positive electrode [1], compaction of positive electrode active material layer, conductive material, binder used in the production of positive electrode active material layer, liquid medium for forming slurry, current collector, electrode The area, discharge capacity, thickness of the positive electrode plate, etc. are the same as above.

<Positive pole [2]>

Next, the positive electrode [2] "a positive electrode containing a positive electrode active material having a specific composition represented by the composition formula (4)" used in the lithium secondary battery of the present invention will be described.

[Positive electrode active material of positive electrode [2]]

Next, the positive electrode active material used in the positive electrode [2] will be described.

[[composition]]

As the positive electrode active material, a material having a composition represented by the following composition formula (4) and containing a transition metal capable of electrochemically storing and releasing lithium ions (hereinafter, simply referred to as "the positive electrode active material") is used.

Li _x Ni _(1-yz) Co _y M _z O ₂ composition formula (4)

[In the composition formula (4), M represents at least one element selected from Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, x represents a number satisfying 0<x≤1.2, and y represents the number satisfying 0.05≤y≤0.5, and z represents the number satisfying 0.01≤z≤0.5].

In the composition formula (4), M is preferably Mn, Al or Mg, and x is preferably 0.2≤x≤1.15. In addition, y is preferably 0.08≤y≤0.4, particularly preferably 0.1≤y≤0.3. In addition, z is preferably 0.02≤z≤0.4, particularly preferably 0.03≤z≤0.3.

[[Cladding]]

In addition, it is preferable to use a positive electrode active material having a composition different from that of the positive electrode active material adhered to the surface of the positive electrode active material. The type, method of adhesion, amount of adhesion, etc. of the surface adhesion substance are the same as above.

[[shape]]

The particle shape of the positive electrode active material is the same as above.

[[Tap Density]]

The tap density of this positive electrode active material is the same as above.

[[Median particle size d ₅₀ ]]

The median diameter d ₅₀ (the diameter of the secondary particle when the primary particles are aggregated to form secondary particles) of the particles of the positive electrode active material is the same as above.

[[average primary particle size]]

When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is the same as described above.

[[BET specific surface area]]

The BET specific surface area of the positive electrode active material is the same as above.

[[Manufacturing method]]

As a method for producing the positive electrode active material, a common method for producing an inorganic compound can be used. In particular, when making a spherical or ellipsoidal active material, various methods can be considered, for example, the following method can be enumerated: nickel raw materials such as nickel nitrate and nickel sulfate, cobalt raw materials such as cobalt nitrate and cobalt sulfate, and the composition formula (4 ) in the M raw material is dissolved or pulverized and dispersed in water or other solvents, and the pH is adjusted while stirring to prepare and obtain a spherical precursor. After drying it as necessary, add LiOH, Li ₂ CO ₃ , LiNO ₃ and other Li source, a method of sintering at high temperature to obtain an active material; nickel raw materials such as nickel nitrate, nickel sulfate, nickel oxide, nickel hydroxide, nickel hydroxide, and cobalt nitrate, cobalt sulfate, cobalt oxide, cobalt hydroxide, The cobalt raw material such as cobalt basic hydroxide and the raw material of M in the composition formula (4) are dissolved or pulverized and dispersed in a solvent such as water, and then dried and shaped by a spray dryer to form a spherical or ellipsoidal precursor. body, and then adding Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and sintering at high temperature to obtain active materials; and nickel nitrate, nickel sulfate, nickel oxide, nickel hydroxide, nickel hydroxide Nickel raw materials such as cobalt nitrate, cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide and other cobalt raw materials, and the raw materials of M in the composition formula (4) and LiOH, Li ₂ CO ₃ , LiNO ₃ etc. Li source is dissolved or pulverized and dispersed in a solvent such as water, and then dried and shaped by a spray dryer to form a spherical or ellipsoidal precursor, which is then sintered at a high temperature to obtain an active material.

In order to manufacture the positive electrode in the present invention, the positive electrode active material (the positive electrode active material represented by the composition formula (4) and/or the positive electrode active material represented by the composition formula (4) coated by the above-mentioned surface attachment substance) can be used alone, or The cathode active material and one or more substances different in composition from the cathode active material may be used in combination in any combination and ratio. As a preferred combination at this time, the combination of the positive active material and LiMn ₂ O ₄ or a part of Mn thereof is replaced by other transition metals; or the positive active material and LiCoO ₂ or part of Co is replaced by other transition metals. Combination of substances obtained by substitution of metals.

Here, the positive electrode active material is preferably 30% by mass or more, more preferably 50% by mass or more of the total positive electrode active material. When the usage ratio of the positive electrode active material is reduced, the battery capacity may be reduced. In addition, "the positive electrode active material" and "the positive electrode active material other than the positive electrode active material" are collectively referred to as "the positive electrode active material".

[Structure of the positive electrode of the positive electrode [2]]

Next, the structure of the positive electrode used in the positive electrode [2] will be described.

Electrode structure and manufacturing method in positive electrode [2], compaction of positive electrode active material layer, conductive material, binder used in the production of positive electrode active material layer, liquid medium for forming slurry, current collector, electrode The area, discharge capacity, thickness of the positive electrode plate, etc. are the same as above.

<Positive pole [3]>

Next, the positive electrode [3] "a positive electrode containing any one positive electrode active material selected from the following (a) to (d)" used in the lithium secondary battery of the present invention will be described.

(a) A positive electrode active material having a BET specific surface area of 0.4m ² /g to 2m ² /g

(b) Positive active material having an average primary particle size of 0.1 μm to 2 μm

(c) A positive electrode active material having a median diameter _d50 of 1 μm to 20 μm

(d) A positive electrode active material having a tap density of 1.3 g/cm ³ to 2.7 g/cm ³ .

[Positive electrode active material of positive electrode [3]]

Next, the positive electrode active material used in the positive electrode [3] will be described.

[[composition]]

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. A substance containing lithium and at least one transition metal is preferable, and examples thereof include lithium-transition metal composite oxides and lithium-containing transition metal phosphate compounds. Specifically, those having the same composition as above can be used.

[[Cladding]]

Preferably, a positive electrode active material having a composition different from that of the positive electrode active material of the core adheres to the surface of the positive electrode active material. The type, method of adhesion, amount of adhesion, etc. of the surface adhesion substance are the same as above.

[[shape]]

The particle shape of the positive electrode active material is the same as above.

[[BET specific surface area]]

The BET specific surface area of the positive electrode active material is preferably 0.4 m ² /g or more, more preferably 0.5 m ² /g or more, even more preferably 0.6 m ² /g or more, the upper limit is preferably 2 m ² /g or less, more preferably 1.8 m ² /g or less, more preferably 1.5 m ² /g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to decrease, and if the BET specific surface area is larger than this range, it is difficult to increase the tap density, and problems may easily occur in coating properties when forming a positive electrode active material.

The BET specific surface area is defined as the following value: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 150°C for 30 minutes under nitrogen flow, and then adjusted to the nitrogen relative The value measured by the nitrogen adsorption BET 1-point method using the gas flow method for a nitrogen-helium mixed gas with a relative pressure value of 0.3 at atmospheric pressure.

[[average primary particle size]]

When primary particles aggregate to form secondary particles, the average primary particle size of the positive electrode active material is preferably 0.1 μm or more, more preferably 0.2 μm or more, further preferably 0.3 μm or more, most preferably 0.4 μm or more, and the upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, most preferably 1 μm or less. When the average primary particle size exceeds the above upper limit, it is difficult to form spherical secondary particles, which adversely affects the powder fillability, or the specific surface area is greatly reduced, and therefore battery performance such as output characteristics may decrease. On the contrary, if the average primary particle diameter is less than the above-mentioned lower limit, problems such as poor charge-discharge reversibility may occur due to incomplete crystallization.

The primary particle size can be measured by observation using a scanning electron microscope (SEM). Specifically, it is obtained by the following method: in a photograph with a magnification of 10,000 times, for any 50 primary particles, the longest value of the slice generated by the left and right boundary lines of the primary particles on a straight line in the horizontal direction is obtained, and the maximum value is obtained. average value.

[[Median particle size d ₅₀ ]]

The median diameter _d50 of the particles of the positive electrode active material (when the primary particles are aggregated to form secondary particles, the diameter of the secondary particles) is preferably 1 μm or more, more preferably 1.2 μm or more, even more preferably 1.5 μm or more, and most preferably 1 μm or more. It is preferably 2 μm or more, and the upper limit thereof is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, and most preferably 15 μm or less. If the median particle diameter _d50 is lower than the above-mentioned lower limit, a product with a high tap density may not be obtained, and if it exceeds the upper limit, since the diffusion of lithium in the particles takes time, the performance of the battery may sometimes decrease, or the resulting battery may be damaged. Streaks and other problems occur when the active material and conductive agent or binder are slurried in a solvent and then coated into a film. When the positive electrode active material of the present invention is a positive electrode active material obtained by mixing two or more positive electrode active materials having different median particle diameters _d50 , it can further improve the filling property when making a positive electrode, which is preferable.

In addition, the median diameter _d50 in the present invention can be measured using a known laser diffraction/scattering type particle size distribution analyzer. LA-920 manufactured by HORIBA was used as a particle size distribution meter. As a dispersion medium used in the measurement, a 0.1% by mass sodium hexametaphosphate aqueous solution was used, ultrasonically dispersed for 5 minutes, and then measured by setting the measurement refractive index to 1.24.

[[Tap Density]]

The tap density of the positive electrode active material is preferably 1.3 g/cm ³ or higher, more preferably 1.5 g/cm ³ or higher, still more preferably 1.6 g/cm ³ or higher, most preferably 1.7 g/cm ³ or higher. If the tap density of the positive electrode active material is lower than the above-mentioned lower limit, then when forming the positive electrode active material layer, the amount of dispersion medium required increases, and the necessary amount of conductive material or binder increases simultaneously, and the positive electrode active material is in the positive electrode active material layer. The filling rate of the battery is restricted, and the battery capacity is sometimes restricted. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. In general, the larger the tap density, the better, and there is no particular upper limit, but if the tap density is too large, the diffusion of lithium ions in the positive electrode active material layer with the electrolyte as a medium becomes a factor determining the speed, and the load characteristics sometimes Therefore, the upper limit of the tap density is preferably 2.7 g/cm ³ or less, more preferably 2.5 g/cm ³ or less.

In the present invention, the tap density is defined as follows: the sample is dropped into a 20 cm ³ tapped container through a sieve with an aperture of 300 μm, and after the container volume is filled, a powder density measuring device (for example, Tap densor manufactured by Seishin Co., Ltd.) is used. , vibration with a stroke length of 10 mm was performed 1000 times, and the bulk density at this time was taken as the tap density.

From the perspective of long life and high output, the positive electrode active material in the lithium secondary battery of the present invention preferably satisfies 2 of the above-mentioned BET specific surface area, average primary particle size, median particle size _d50 and tap density at the same time. more than one physical property.

[[Manufacturing method]]

The manufacturing method of this positive electrode active material is the same as above.

The positive electrode active material in the lithium secondary battery of the present invention may be used alone, or may be used in combination of two or more positive electrode active materials having different compositions or different powder physical properties in any combination and ratio. In addition, from the viewpoint of improving life, the positive electrode of the present invention preferably contains a positive electrode active material (the positive electrode active material) having any of the above physical properties and a positive electrode active material having a composition different from the positive electrode active material.

[Structure of the positive electrode of the positive electrode [3]]

Next, the structure of the positive electrode used in the positive electrode [3] will be described.

Electrode structure and manufacturing method in positive electrode [3], compaction of positive electrode active material layer, conductive material, binder used in the production of positive electrode active material layer, liquid medium for forming slurry, current collector, electrode The area, discharge capacity, thickness of the positive electrode plate, etc. are the same as above.

<Positive pole [4]>

Next, the positive electrode [4] "a positive electrode satisfying any one of the following conditions (e) to (f)" used in the lithium secondary battery of the present invention will be described.

(e) A positive electrode made by forming a positive electrode active material layer containing a positive electrode active material, a conductive material and a binder on a current collector, wherein the content of the conductive material in the positive electrode active material layer is 6% by mass to 20% by mass range (mode 1)

(f) a positive electrode made by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector, wherein the density of the positive electrode active material layer is in the range of 1.7 g/cm ³ to 3.5 g/cm ³ ( way 2)

(g) a positive electrode made by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on the current collector, wherein the ratio of the thickness of the positive electrode active material layer to the current collector (one period before injecting the nonaqueous electrolyte solution) The value of (thickness of side active material layer)/(thickness of current collector) is 1.6 to 20 (form 3).

[Positive electrode active material of positive electrode [4]]

Next, the positive electrode active material used in the positive electrode [4] will be described.

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. A substance containing lithium and at least one transition metal is preferable, and examples thereof include lithium-transition metal composite oxides and lithium-containing transition metal phosphate compounds. Specifically, those having the same composition as above can be used.

The surface coating, shape, tap density, median particle size d ₅₀ , average primary particle size, BET specific surface area, production method, etc. of the positive electrode active material are the same as above.

[Structure of the positive electrode of the positive electrode [4]]

Next, the structure of the positive electrode used in the positive electrode [4] will be described.

[[Electrode structure and fabrication method]]

The positive electrode [4] in the lithium secondary battery of the present invention is produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be performed according to a usual method. That is, at least the positive electrode active material, the binder, the conductive material used as needed (in the mode 1 is an essential component), and the thickener used as needed are dry-mixed to form a sheet, and then the The sheet-like material is pressure-bonded on the positive electrode collector, or these materials are dissolved or dispersed in a liquid medium to make a slurry, and then the slurry is coated on the positive electrode collector and dried, so that the A positive electrode active material layer is formed on the current collector to obtain a positive electrode.

The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, particularly preferably 84% by mass or more. The upper limit thereof is preferably 95% by mass or less, more preferably 93% by mass or less. When the content of the positive electrode active material in the positive electrode active material layer is low, the capacitance may become insufficient. Conversely, if the content of the positive electrode active material is too high, the strength of the positive electrode may not be sufficient.

[[Conductive Material]]

As the conductive material, known conductive materials can be used arbitrarily. Specific examples include the same conductive materials as those described above.

The content of the conductive material used in the positive electrode of the lithium secondary battery of the present invention in the positive electrode active material layer is as follows: in mode 1, it must be 6% by mass or more, preferably 7% by mass or more, more preferably 8% by mass or more, It is more preferably 9% by mass or more; and it is not particularly limited in Embodiment 2 and Embodiment 3, but is preferably 6% by mass or more, more preferably 7% by mass or more, and still more preferably 8% by mass or more. If the content of the conductive material in the positive electrode active material layer is too small, the conductivity may be insufficient, and high output may not be obtained.

In addition, the upper limit of the content of the conductive material in the positive electrode active material layer is as follows: in mode 1, it must be 20 mass % or less, preferably 18 mass % or less, particularly preferably 15 mass % or less; in addition, in mode 2 and mode 3 is not particularly limited, but is preferably 20% by mass or less, more preferably 18% by mass or less, even more preferably 15% by mass or less. If its content is too large, the battery capacity will decrease, and high output may not be obtained.

[[Binder]]

The binder used in the manufacture of the positive electrode active material layer is not particularly limited. When using the coating method, any material can be dissolved or dispersed in the liquid medium used in the manufacture of the electrode. As a specific example, The same substances as above are listed.

The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60% by mass or less, more preferably Preferably it is 40 mass % or less, More preferably, it is 10 mass % or less. If the ratio of the binder is too low, the positive electrode active material may not be sufficiently retained, the mechanical strength of the positive electrode may be insufficient, and battery performance such as cycle characteristics may deteriorate. On the other hand, if the ratio of the binder is too high, it sometimes leads to a decrease in battery capacity or conductivity.

[[The liquid medium used to form the slurry]]

The liquid medium used to form the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, conductive agent, binder and, if necessary, a thickener. Aqueous solvents and organic solvents can be used. any of the solvents. Specific examples include the same ones as above. The kind and addition amount of the tackifier are also the same as above.

[[Compaction]]

In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably compacted using a manual press, a roll press, or the like. The lower limit of the density of the positive electrode active material layer must be 1.7 g/cm ^or more in mode 2, preferably 2.0 g/cm ^or more, particularly preferably 2.2 g/cm ^or more; in addition, in mode 1 and mode 3, there is no Especially limited, it is preferably 1.7 g/cm ³ or more, more preferably 2.0 g/cm ³ or more, and still more preferably 2.2 g/cm ³ or more. If the density is lower than this range, the conductivity between the active materials will decrease, the battery impedance will increase, and high output may not be obtained.

The upper limit of the density of the positive electrode active material layer must be 3.5g/cm ³ or less in mode 2, preferably 3.0 g/cm ³ or less, particularly preferably 2.8 g/cm ³ or less; Especially limited, it is preferably 3.5 g/cm ³ or less, more preferably 3.0 g/cm ³ or less, and still more preferably 2.8 g/cm ³ or less. If the density is higher than this range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector/active material interface decreases, especially the charge and discharge characteristics at high current density decrease, and high output may not be obtained.

[[Collector]]

The material of the positive electrode current collector is not particularly limited, and is the same as above. In addition, the shape of the current collector and the thickness of the film are also the same as above.

For the ratio of the thickness of the positive electrode active material layer and the current collector, the value of (the thickness of the active material layer on the side before injecting the nonaqueous electrolyte)/(the thickness of the current collector) must be 20 or less in mode 3, preferably It is 15 or less, particularly preferably 10 or less; in addition, it is not particularly limited in Embodiment 1 and Embodiment 2, but it is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. If this range is exceeded, the current collector may generate heat due to Joule heat during high current density charge and discharge, and the positive electrode may be damaged.

The lower limit of the value of (the thickness of the active material layer on the side before injecting the nonaqueous electrolyte)/(the thickness of the current collector) must be 1.6 or more in mode 1, preferably 1.8 or more, particularly preferably 2 or more; Moreover, although it does not specifically limit in the form 1 and the form 2, Preferably it is 1.6 or more, More preferably, it is 1.8 or more, More preferably, it is 2 or more. Below this range, since the volume ratio of the current collector to the positive electrode active material increases, the capacity of the battery decreases, and high output may not be obtained.

The above-mentioned "content of conductive material in the positive electrode active material layer", "density of the positive electrode active material layer", "ratio of the thickness of the positive electrode active material layer and the current collector, that is (the activity of the side before injecting the non-aqueous electrolyte) A more preferable high-power lithium secondary battery can be formed by combining the respective preferable ranges of "substance layer thickness)/(current collector thickness)".

[[Electrode Area]]

When using the non-aqueous electrolytic solution of the present invention, from the viewpoint of high output and improved stability at high temperature, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery case, which is the same as above.

[[Discharge capacity]]

When using the non-aqueous electrolytic solution for secondary batteries of the present invention, if the capacitance (capacity when the battery is discharged from a fully charged state to a discharged state) of the battery elements contained in the battery case of one secondary battery is 3 If the ampere-hour (Ah) or more is greater, the effect of improving the output characteristics becomes greater, which is preferable.

Therefore, the design and the like of the positive electrode plate and the like are also the same as described above.

[[Thickness of positive plate]]

The thickness of the positive electrode plate is not particularly limited, and is the same as above.

<Positive pole [5]>

Next, the positive electrode [5] used in the lithium secondary battery of the present invention will be described.

[Positive electrode active material of positive electrode [5]]

Next, the positive electrode active material used in the positive electrode [5] will be described.

[[composition]]

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. A substance containing lithium and at least one transition metal is preferable, and examples thereof include lithium-transition metal composite oxides and lithium-containing transition metal phosphate compounds.

As the transition metal of the lithium-transition metal composite oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable, and specific examples include lithium-cobalt composite oxides such as LiCoO ₂ and lithium-cobalt composite oxides such as LiNiO ₂ . - Nickel composite oxides; LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO ₃ and other lithium-manganese composite oxides; Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg , Ga, Zr, Si, and other metals instead of a part of the transition metal atoms forming the main body of these lithium-transition metal composite oxides.

The lithium-cobalt composite oxide is not particularly limited, but preferably has a composition represented by the following composition formula (8).

Li _x Co _(1-y) M ¹ _y O ₂ composition formula (8)

[In the composition formula (8), ^M1 represents at least one element selected from Ni, Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (8), M ¹ is particularly preferably Ni, Mn, Al, and Fe, and x is particularly preferably 0.2≤x≤1.15, and y is particularly preferably 0.1≤y≤0.5.

The lithium-nickel composite oxide is not particularly limited, but preferably has a composition represented by the following composition formula (9).

Li _x Ni _(1-y) M ² _y O ₂ composition formula (9)

[In the composition formula (9), M represents at ^least one element selected from Co, Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (9), ^M2 is particularly preferably Co, Mn, Al, and Fe, and x is particularly preferably 0.2≤x≤1.15, and y is particularly preferably 0.1≤y≤0.5.

The lithium-manganese composite oxide is not particularly limited, but preferably has a composition represented by the following composition formula (10).

Li _x Mn _(1-y) M ³ _y O ₂ composition formula (10)

[In the composition formula (10), M represents at ^least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (10), M ³ is particularly preferably Ni, Co, and Fe, and x is particularly preferably 0.2≤x≤1.15, and y is particularly preferably 0.1≤y≤0.7.

As the above-mentioned lithium-manganese composite oxide, one having a composition represented by the following composition formula (11) is preferable.

Li _x Mn _(2-y) M ⁴ _y O ₄ composition formula (11)

[In the composition formula (11), M represents at ^least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (11), M ⁴ is particularly preferably Ni, Co, Al, and Mg, and x is particularly preferably 0.05≤x≤1.15, and y is particularly preferably 0.1≤y≤0.7.

As the lithium-manganese composite oxide, one having a composition represented by the following composition formula (12) is preferable.

Li _x Mn _(1-y) M ⁵ _y O ₃ composition formula (12)

[In the composition formula (12), M represents at ^least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤2.4 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (12), M ⁵ is particularly preferably Ni, Co, Al, and Mg, and x is particularly preferably 0.1≤x≤2.3, and y is particularly preferably 0.1≤y≤0.5.

The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples include LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , Iron phosphate such as LiFeP ₂ O ₇ ; Cobalt phosphate such as LiCoPO ₄ ; Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and others Substitution of a part of the transition metal atoms forming the main body of these lithium-containing transition metal phosphate compounds with a metal, etc.

The above-mentioned iron phosphates are not particularly limited, but preferably have a composition represented by the following composition formula (13).

Li _x Fe _(1-y) M ⁶ _y PO ₄ composition formula (13)

[In the composition formula (13), M represents at ^least one element selected from Ni, Co, Mn, Al, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents an element satisfying 0<x≤1.2 number, y represents the number satisfying 0.05≤y≤0.8].

In the composition formula (13), ^M6 is particularly preferably Ni, Co, Mn, and Al, and x is particularly preferably 0.2≤x≤1.15, and y is particularly preferably 0.1≤y≤0.5.

The positive electrode active material in the present invention is preferably used in combination of two or more materials having different compositions among the above positive electrode active materials in any combination and ratio. Since various positive electrode active materials have different performances, it is preferable to combine required performances of the positive electrode active material according to the intended use of the battery. In general, it is considered that the performance can be added and averaged by combination, but for life, the effect of a long-lived positive electrode active material can be further obtained unexpectedly, and by combining a positive electrode active material with a relatively good life and a relatively poor life but others. The positive electrode active material with good performance can realize the lithium secondary battery with high output, large capacity and long life of the present invention.

As an example of a preferred combination, the following combinations can be enumerated:

The positive electrode active material represented by composition formula (8) and the positive electrode active material represented by composition formula (10),

The positive electrode active material represented by composition formula (8) and the positive electrode active material represented by composition formula (11),

The positive electrode active material represented by composition formula (8) and the positive electrode active material represented by composition formula (12),

The positive electrode active material represented by composition formula (8) and the positive electrode active material represented by composition formula (13),

The positive electrode active material represented by composition formula (9) and the positive electrode active material represented by composition formula (10),

The positive electrode active material represented by composition formula (9) and the positive electrode active material represented by composition formula (11),

The positive electrode active material represented by the composition formula (9) and the positive electrode active material represented by the composition formula (12),

The positive electrode active material represented by composition formula (9) and the positive electrode active material represented by composition formula (13),

The positive electrode active material represented by the composition formula (10) and the positive electrode active material represented by the composition formula (11),

The positive electrode active material represented by composition formula (10) and the positive electrode active material represented by composition formula (12),

A positive electrode active material represented by compositional formula (10) and a positive electrode active material represented by compositional formula (13).

It is particularly preferred that

The positive electrode active material represented by composition formula (9) and the positive electrode active material represented by composition formula (11),

A positive electrode active material represented by compositional formula (10) and a positive electrode active material represented by compositional formula (11).

The combination ratio is not particularly limited, but is preferably 10:90 to 90:10, more preferably 20:80 to 80:20.

In the positive electrode used in the lithium secondary battery of the present invention, there are more than two kinds of positive electrode active materials with different compositions _, preferably the BET specific surface area, average primary particle size, and median particle size d of at least one positive electrode active material wherein And/or the tap density (hereinafter, abbreviated as "the following physical properties") is within the following specific range. Two or more positive electrode active materials having different compositions also include positive electrode active materials whose physical properties do not fall within the following ranges, but it is preferable that all of the two or more positive electrode active materials have certain physical properties within the following ranges. The content ratio of "all positive electrode active materials having any of the following physical properties within the following specific ranges" relative to "all positive electrode active materials contained in the positive electrode" depends on the physical properties and is not particularly limited, but is preferably 30% by mass or more, More preferably, it is 50 mass % or more, Especially preferably, it is all. Preferably, each of the two or more positive electrode active materials contained in the positive electrode has any one or more of the following physical properties within the following specific ranges, and more preferably any two or more physical properties are within the following specific ranges. It is particularly preferred that any three or more physical properties are within the following specific ranges, and most preferably all of the following physical properties are within the following specific ranges.

[[BET specific surface area]]

The BET specific surface area of at least one positive electrode active material in the positive electrode active material is preferably 0.4 m ² /g or more, more preferably 0.5 m ² /g or more, still more preferably 0.6 m ² /g or more, and the upper limit is 2 m ² /g or less, preferably 1.8 m ² /g or less, more preferably 1.5 m ² /g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to decrease, and if the BET specific surface area is larger than this range, it is difficult to increase the tap density, and problems may easily occur in coating properties when forming a positive electrode active material.

The BET specific surface area is defined as the following value: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 150°C for 30 minutes under nitrogen flow, and then adjusted to the nitrogen relative The value measured by the nitrogen adsorption BET 1-point method using the gas flow method for a nitrogen-helium mixed gas with a relative pressure value of 0.3 at atmospheric pressure.

[[average primary particle size]]

As the average primary particle diameter of at least one positive electrode active material in the positive electrode active material, it is preferably 0.1 μm or more, more preferably 0.2 μm or more, further preferably 0.3 μm or more, most preferably 0.4 μm or more, and the upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, most preferably 1 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder fillability, or the specific surface area is greatly reduced, and thus battery performance such as output characteristics may decrease in possibility. On the contrary, if it is less than the above-mentioned lower limit, problems such as poor reversibility of charging and discharging may arise due to incomplete crystallization.

In addition, the primary particle size can be measured by observation using a scanning electron microscope (SEM). Specifically, it is obtained by the following method: in a photograph with a magnification of 10,000 times, for any 50 primary particles, the longest value of the slice generated by the left and right boundary lines of the primary particles on a straight line in the horizontal direction is obtained, and the maximum value is obtained. average value. Although primary particles may aggregate to form secondary particles, in this case, only primary particles are measured.

[[Median particle size d ₅₀ ]]

The median diameter _d50 (the secondary particle diameter when the primary particles are aggregated to form secondary particles) of the particles of at least one positive electrode active material in the positive electrode active material is preferably 1 μm or more, more preferably 1.2 μm or more, More preferably 1.5 μm or more, most preferably 2 μm or more, the upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, most preferably 15 μm or less. If it is lower than the above-mentioned lower limit, sometimes a product with a high tap density cannot be obtained, and if it exceeds the upper limit, since the diffusion of lithium in the particles takes time, the performance of the battery may sometimes decrease, or the positive electrode of the battery, that is, the When active materials, conductive agents, binders, etc. are slurried in a solvent and then coated into a film, problems such as streaks occur. Here, by mixing two or more positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of producing the positive electrode can be further improved.

The median diameter d ₅₀ in the present invention can be measured using a known laser diffraction/scattering particle size distribution analyzer. LA-920 manufactured by HORIBA was used as a particle size distribution meter, and as a dispersion medium used in the measurement, 0.1 mass % sodium hexametaphosphate aqueous solution was used, ultrasonic dispersion was carried out for 5 minutes, and the measurement refractive index was set to 1.24 for measurement.

[[[Tap Density]]]

The tap density of at least one positive active material in the positive active material is preferably 1.3 g/cm ^or more, more preferably 1.5 g/cm ^or more, further preferably 1.6 g/cm ^or more, most preferably 1.7 g /cm ³ or more. If the tap density of the positive electrode active material is lower than the above-mentioned lower limit, then when forming the positive electrode active material layer, the amount of dispersion medium required increases, and the necessary amount of conductive material or binder increases simultaneously, and the positive electrode active material is in the positive electrode active material layer. The filling rate of the battery is restricted, and the battery capacity is sometimes restricted. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. Generally speaking, the larger the tap density is, the more preferable, there is no special upper limit, but if the tap density is too large, the diffusion of lithium ions in the positive electrode active material layer with the non-aqueous electrolyte as a medium becomes a factor determining the speed. Since the properties are likely to decrease in some cases, the upper limit of the tap density is preferably 2.7 g/cm ³ or less, more preferably 2.5 g/cm ³ or less.

In the present invention, the tap density is defined as follows: the sample is dropped into a 20 cm ³ tapped container through a sieve with an aperture of 300 μm, and after the container volume is filled, a powder density measuring device (for example, Tap densor manufactured by Seishin Co., Ltd.) is used. , vibration with a stroke length of 10 mm was performed 1000 times, and the bulk density at this time was taken as the tap density.

[[Cladding]]

At least one positive active material in the positive active material preferably uses a material (hereinafter referred to as "surface-attached material" for short) that is attached to its surface with a positive active material that constitutes the main body of the positive active material or a positive active material of the core. ). The type, method of adhesion, amount of adhesion, etc. of the surface adhesion substance are the same as above.

[[shape]]

The particle shape of at least one positive electrode active material among the positive electrode active materials may be the same shape as the above as conventionally used.

[[Manufacturing method]]

As a method for producing the positive electrode active material, a general method as a method for producing an inorganic compound similar to the above can be used.

[Structure of the positive electrode of the positive electrode [5]]

Next, the structure of the positive electrode used in the positive electrode [5] will be described.

In the present invention, electrode structure and production method, compaction of positive electrode active material layer, conductive material, binder material used in the manufacture of positive electrode active material layer, liquid medium for forming slurry, current collector, electrode area , discharge capacity, thickness of positive electrode plate, etc. are the same as above. When producing the positive electrode, two or more types of positive electrode active materials may be mixed beforehand, or may be added and mixed at the same time when producing the positive electrode.

<negative electrode>

The negative electrode used in the lithium secondary battery of the present invention is not particularly limited as long as an active material layer containing an active material capable of absorbing and releasing lithium ions is formed on the current collector, but the negative electrode is preferably selected from Any one of the following negative poles [1] to negative poles [10]:

Negative electrode [1]: a negative electrode containing two or more carbonaceous substances with different crystallinity as the negative electrode active material;

Negative pole [2]: the negative pole that contains amorphous carbonaceous as negative electrode active material, and the interplanar spacing (d002) of (002) plane of described amorphous carbonaceous by wide-angle X-ray diffractometry is more than 0.337nm, crystallite size ( Lc) is less than 80nm, and the Raman R value defined by the ratio of the peak intensity at 1360cm ^-1 to the peak intensity at 1580cm ^-1 measured by argon ion laser Raman spectroscopy is 0.2 or more;

Negative electrode [3]: a negative electrode containing a metal oxide as the negative electrode active material, and the metal oxide contains titanium capable of absorbing and releasing lithium ions;

Negative electrode [4]: a negative electrode containing carbonaceous material as the negative electrode active material, the circularity of the carbonaceous material is above 0.85, and the O/C value of the amount of surface functional groups is 0-0.01;

Negative electrode [5]: a negative electrode containing a hetero-orientation carbon composite as the anode active material, and the hetero-orientation carbon composite contains two or more carbonaceous substances with different orientations;

Negative electrode [6]: a negative electrode containing graphitic carbon particles as the negative electrode active material, the circularity of the graphitic carbon particles is 0.85 or more, and the interplanar distance (d002) of the (002) plane measured by wide-angle X-ray diffraction method is low At 0.337nm, the Raman R value defined by the ratio of the peak intensity at 1360cm ^-1 to the peak intensity at 1580cm ^-1 measured by argon ion laser Raman spectroscopy is 0.12-0.8;

Negative electrode [7]: a negative electrode containing the following multi-element-containing negative electrode active material (C') as the negative electrode active material, the multi-element-containing negative electrode active material (C') containing , Bi, In, Mg, Ga, Cd, Ag, Si, B, Au, Pt, Pd, and Sb lithium storage metal (A') and/or lithium storage alloy (B'), and contains C and/or N as element Z;

Negative electrode [8]: a negative electrode containing two or more negative electrode active materials with different properties as the negative electrode active material;

Negative electrode [9]: Containing a negative electrode active material with a tap density of 0.1 g/cm ³ or more and a pore volume equivalent to particles in the range of 0.01 μm to 1 μm in diameter measured by a mercury porosimeter of 0.01 mL/g or more negative electrode;

Negative pole [10]: when charged to 60% of the nominal capacity of the negative pole, the reaction resistance produced by the opposite battery of the negative pole is a negative pole below 500Ω.

Next, first, a negative electrode generally used in the lithium secondary battery of the present invention will be described.

[Negative electrode active material]

Next, negative electrode active materials commonly used in negative electrodes will be described.

[[composition]]

The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, and examples include carbonaceous materials, metal oxides such as tin oxide or silicon oxide, metal composite oxides, lithium simple substances, or lithium ions. Lithium alloys such as aluminum alloys, metals such as Sn and Si that can form alloys with lithium, and the like. These may be used individually, and may be used combining 2 or more types by arbitrary combinations and ratios. Among them, carbonaceous materials or lithium composite oxides are preferably used from the viewpoint of safety.

The metal composite oxide is not particularly limited as long as it can occlude and release lithium, but it is preferable to contain titanium and/or lithium as a constituent in terms of high current density charge and discharge characteristics.

As carbonaceous materials, from the balance of initial irreversible capacity and high current density charge and discharge characteristics, the following carbonaceous materials are preferred:

(1) Natural graphite;

(2) Artificial carbonaceous substances and artificial graphite substances; carbonaceous substances [such as natural graphite, coal coke, petroleum coke, coal pitch, petroleum pitch, or substances obtained by oxidation of these pitches, needle-shaped Coke, pitch coke, and carbon materials obtained by partially graphitizing them; thermal decomposition products of organic substances such as furnace black, acetylene black, and pitch-based carbon fibers, and carbonizable organic substances (for example, coal tar pitch from soft pitch to hard pitch) Or dry distillation liquefied oil and other coal-based heavy oil, atmospheric residual oil, vacuum residual oil and other straight-run heavy oil; crude oil, naphtha and other by-products of thermal decomposition of ethylene tar and other decomposed heavy oil; and acenaphthylene, decacyclic Aromatic hydrocarbons such as alkene, anthracene, and phenanthrene; nitrogen ring compounds such as phenazine or acridine; sulfur ring compounds such as thiophene and dithiophene; polyphenylenes such as biphenyl and terphenyl; polyvinyl chloride, polyvinyl alcohol, polyvinyl alcohol Butyral, their insoluble processed products, nitrogen-containing polyacrylonitrile, polypyrrole and other organic polymers; sulfur-containing polythiophene, polystyrene and other organic polymers; cellulose, lignin, mannan, Natural polymers such as polygalacturonic acid, chitosan, and sucrose; thermoplastic resins such as polyphenylene sulfide and polyphenylene ether; thermosetting resins such as furfuryl alcohol resins, phenolic resins, and imide resins) and their carbides; or solutions formed by dissolving carbonizable organic substances in low-molecular organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and their carbides] in the range of 400 to 3200 ° C for more than one time Carbon materials formed by heat treatment;

(3) The negative electrode active material layer is composed of at least two carbonaceous materials with different crystallinity, and/or carbon materials with different crystallinity carbonaceous interfaces that have a contact interface;

(4) The negative electrode active material layer is composed of at least two kinds of carbonaceous materials with different orientations, and/or a carbon material in which the carbonaceous materials with different orientations have a contact interface.

[Structure, Physical Properties and Preparation Method of Negative Electrode]

Regarding the properties of the carbon material, the negative electrode containing the carbon material, the electrode polarization method, the current collector and the lithium secondary battery, it is preferable to simultaneously satisfy any one or more of the following items (1) to (9).

(1) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction using the Gakujin method for the carbon material is preferably 0.335 nm or more, and its upper limit is usually 0.36 nm or less, preferably 0.35 mm or less, more preferably 0.345nm or less. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is preferably 1 nm or more, more preferably 1.5 nm or more.

(2) Ash content

The ash contained in the carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and the lower limit is preferably 1 ppm or more based on the total mass of the carbonaceous material. If the above range is exceeded, the deterioration of battery performance due to the reaction with the non-aqueous electrolytic solution at the time of charging and discharging cannot be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Volume-based average particle size

The volume-based average particle size of the carbonaceous material is the volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. In addition, the upper limit thereof is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, particularly preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, when an electrode is produced by coating, a non-uniform coating surface will be easily formed, and it may be unpreferable in a battery production process.

In the present invention, the volume-based average particle diameter is defined by a median particle diameter measured by dispersing carbon powder in polyoxyethylene (20) sorbitan as a surfactant. In a 0.2% by mass aqueous solution (about 10 mL) of monolaurate, it measures using a laser diffraction/scattering particle size distribution meter (for example, LA-700 manufactured by Horiba, Ltd.).

(4) Raman R value, Raman half value width

The R value of the carbonaceous material measured by the argon ion laser Raman optical method is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and its upper limit is 1.5 or less, preferably 1.2 or less, more preferably 1.0 or less, and further It is preferably in the range of 0.5 or less. If the R value is lower than this range, the crystallinity of the particle surface is too high, and the sites (sites) where Li enters the interlayer during charging and discharging may decrease. That is, charge acceptance may be lowered. In addition, when the anode is densified by pressing after coating on the current collector, the crystals tend to be oriented in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

In addition, the Raman half-value width of the carbonaceous material around 1580 cm ^-1 is not particularly limited, but it is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and its upper limit is usually 100 cm ^-1 or less, preferably 80 cm ^-1 or less , more preferably not more than 60 cm ^-1 , still more preferably not more than 40 cm ^-1 . If the Raman half-value width is below this range, the crystallinity of the particle surface is too high, and there may be fewer sites (sites) where Li enters the interlayer during charge and discharge. That is, charge acceptance may be lowered. In addition, when the anode is densified by pressing after coating on the current collector, the crystals tend to be oriented in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

The measurement of the Raman spectrum is carried out as follows: Using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped and filled in a measurement cell, and argon ions are irradiated on the surface of the sample in the cell. laser while rotating the pool in a plane perpendicular to the laser. For the obtained Raman spectrum, the intensity I _A of the peak PA near 1580 cm ^-1 and the intensity I _B of the peak P _B near 1360 cm ^-1 were measured _, and the intensity ratio R (R= _IB / _IA ) was calculated. It is defined as the Raman R value of the carbonaceous material. In addition, the half-value width of the peak _PA in the vicinity of 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the carbonaceous material.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

R value, half value width analysis: background (background) processing

Smoothing (smoothing) processing: simple average, convolution 5 points (コンボリユシヨン5ポイント)

(5) BET specific surface area

The specific surface area of the carbonaceous material of the present invention measured by the BET method is usually 0.1 m ² /g or more, preferably 0.7 m ² /g or more, more preferably 1.0 m ² /g or more, and still more preferably 1.5 m ² /g above. The upper limit thereof is usually 100 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. If the value of the specific surface area is less than the above range, when it is used as a negative electrode, the acceptance of lithium at the time of charging will be deteriorated, and lithium will be easily deposited on the surface of the electrode. On the other hand, if it is higher than the above range, when used as a negative electrode material, the reactivity with the non-aqueous electrolytic solution increases, the gas generated tends to increase, and it may be difficult to obtain a preferable battery.

The specific surface area measured by the BET method uses the value measured by pre-drying the sample at 350° C. for 15 minutes under nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), and then , using a nitrogen-helium mixed gas whose relative pressure value of nitrogen relative to the atmospheric pressure is accurately adjusted to 0.3, and measured by the nitrogen adsorption BET 1-point method using the gas flow method.

(6) Micropore size distribution

The pore size distribution of the carbonaceous material used in the present invention is obtained by mercury porosimetry (mercury intrusion method), which is equivalent to the voids in the particles with a pore diameter of 0.01 μm to 1 μm, which is caused by the unevenness of the particle surface. The amount of unevenness, the contact surface between particles, etc. is 0.01mL/g or more, preferably 0.05mL/g or more, more preferably 0.1mL/g or more, and the upper limit is 0.6mL/g or less, preferably 0.4mL/g or less, more preferably in the range of 0.3 mL/g or less. If it exceeds this range, a large amount of binder may be required when producing an electrode plate. If it is less than this range, the high current density charge-discharge characteristics will deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume corresponding to the pore diameter in the range of 0.01 μm to 100 μm is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, still more preferably 0.4 mL/g or more, and the upper limit thereof is 10 mL/g or less , preferably 5 mL/g or less, more preferably 2 mL/g or less. If it is higher than this range, a large amount of binder may be required when producing an electrode plate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained at the time of manufacturing the electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. If it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used as a mercury porosimeter, a mercury porosimeter (autopore (Autopore) 9520; manufactured by Micrometrics (Micromeritex) Co., Ltd.) can be used. About 0.2 g of the sample was sealed in a container for powder, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, depressurize to 4psia (about 28kPa), introduce mercury, increase the pressure from 4psia (about 28kPa) to 40000psia (about 280MPa) stepwise, and then lower the pressure to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore size distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

(7) Circularity

Using circularity as the spherical degree of the carbonaceous material, the circularity of particles whose particle diameter is in the range of 3 to 40 μm is preferably 0.1 or more, particularly preferably 0.5 or more, more preferably 0.8 or more, and even more preferably 0.85 or more, Most preferably, it is 0.9 or more. When the circularity is large, the high current density charge and discharge characteristics are improved, which is preferable.

The circularity is defined by the following formula. When the circularity is 1, it is a theoretical true sphere.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the value measured as follows is used: using, for example, a flow-type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial (Sysmex Industrial) Co., Ltd.), about 0.2 g of the sample is dispersed in a surfactant as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50 mL) of polyoxyethylene (20) sorbitan monolaurate with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, specify a detection range of 0.6 to 400 μm. Particles in the range of ~40μm are measured.

There is no particular limitation on the method of improving the circularity, but it is preferable to make the shape of the spheroid by performing the spheroidization treatment (mechanical energy treatment) because the shape of the gap between the particles can be uniformed when the electrode body is produced. Examples of spheroidization treatment include a method of mechanically approaching a spherical shape by applying a shear force or a compressive force, and a mechanical/physical treatment method of granulating a plurality of fine particles by the adhesive force possessed by a binder or the particles themselves. wait.

(8) True density

The true density of the carbonaceous material is usually above 1.4 g/cm ³ , preferably above 1.6 g/cm ³ , more preferably above 1.8 g/cm ³ , even more preferably above 2.0 g/cm ³ , and its upper limit is 2.26 g/cm 3 or above. ^cm3 or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase. In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

(9) Tap density

The tap density of the carbonaceous material is usually 0.1 g/cm ³ or more, preferably 0.5 g/cm ³ or more, more preferably 0.7 g/cm ³ or more, particularly preferably 1.0 g/cm ³ or more. In addition, the upper limit thereof is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. When the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics. The tap density is measured by the same method as described for the positive electrode, and is defined by this method.

(10) Orientation ratio

The orientation ratio of the carbonaceous material is usually not less than 0.005, preferably not less than 0.01, more preferably not less than 0.015, and the upper limit thereof is in the range of not more than a theoretical value of 0.67. If it is less than this range, the high-density charge-discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction after press-molding the sample. Fill a 0.47g sample into a molding machine with a diameter of 17mm, compress it at 600kgf/ ^cm2 to obtain a molded body, fix the molded body with clay so that it is on the same side as the surface of the sample holder for measurement, and then measure the X-ray diffraction. The ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained carbon (110) diffraction and (004) diffraction peak intensities, and this ratio was defined as the orientation ratio of the active material.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

·Slit:

Divergence slit = 0.5 degrees, light receiving slit = 0.15mm, scattering slit = 0.5 degrees

・Measurement range and step angle/measurement time

(110) surface: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds

(004) surface: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree / 60 seconds

(11) aspect ratio (powder)

The aspect ratio is theoretically 1 or more, and the upper limit is 10 or less, preferably 8 or less, more preferably 5 or less. When the upper limit is exceeded, streaks may be generated at the time of electrode plate production, a uniform coated surface may not be obtained, and high current density charge-discharge characteristics may be reduced.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of the carbonaceous material particle and the shortest diameter B perpendicular thereto when viewed three-dimensionally. Observation of carbon particles was performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of a metal plate with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

(12) Sub-material mixing

The so-called "mixture of auxiliary materials" means that two or more carbonaceous materials with different properties are contained in the negative electrode and/or the negative electrode active material. The properties mentioned here refer to X-ray diffraction parameters, median particle size, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, gray More than one property in a component.

As particularly preferred embodiments, the volume-based particle size distribution is asymmetrical around the median diameter, contains two or more carbonaceous materials with different Raman R values, or has different X-ray parameters.

As an example of the effect, it is possible to reduce resistance by including carbonaceous materials such as graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and amorphous carbon such as needle coke as a conductive agent. These may be used individually, and may be used in combination of 2 or more types by arbitrary combinations and arbitrary ratios. When added as a conductive agent, it is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is 45% by mass or less, preferably 40% by mass. If it is less than this range, it may be difficult to obtain the effect of improving electrical conductivity. If it exceeds the above-mentioned range, the initial irreversible capacity may be increased.

(13) Electrode fabrication

A common method can be used to fabricate the electrodes. For example, a binder, solvent, thickener, conductive material, filler, etc. are added to the negative electrode active material to make a slurry, which is coated on the current collector, dried, and pressed to form electrode. In the stage before the non-aqueous electrolyte injection process, the thickness of the negative electrode active material on each side of the battery is usually more than 15 μm, preferably more than 20 μm, more preferably more than 30 μm, and the upper limit is 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less. If it exceeds this range, the non-aqueous electrolytic solution becomes difficult to permeate to the vicinity of the current collector interface, so that the high current density charge and discharge characteristics are degraded. In addition, if it is less than this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. In addition, the negative electrode active material can be roll-formed to form a sheet-like electrode, or can be formed into a granular electrode by compression-molding.

(14) Collector

As the current collector, known current collectors can be used arbitrarily. Examples of the current collector of the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel, among which copper is preferred from the viewpoints of ease of processing and cost. The shape of the current collector, when the current collector is a metal material, includes metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded alloy, perforated metal, foamed metal, and the like. Among them, metal thin films are preferred, copper foils are more preferred, rolled copper foils produced by calendering and electrolytic copper foils produced by electrolysis are further preferred, and any of them can be used as a current collector. When the thickness of the copper foil is thinner than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu-Cr-Zr alloy, etc.) stronger than pure copper can be used. In addition, aluminum foil is preferably used because it can reduce the weight of a battery when used for a current collector because of its light specific gravity.

In the current collector made of copper foil produced by the rolling method, since the copper crystals are arranged in the rolling direction, even if the negative electrode is bent tightly or bent at an acute angle, it is not easy to break, and it is suitable for small cylindrical batteries. Electrodeposited copper foil is produced, for example, by immersing a metal drum in a non-aqueous electrolytic solution in which copper ions are dissolved, and passing an electric current while rotating the drum, thereby depositing copper on the surface of the drum and peeling it off. Copper can also be electrolytically deposited on the surface of the above-mentioned rolled copper foil. Roughening treatment or surface treatment (for example, chromate treatment with a thickness of about several nm to 1 μm, primer treatment such as Ti, etc.) may be performed on one or both sides of the copper foil.

The current collector substrate is required to have the following physical properties.

(1) Average surface roughness (Ra)

According to the method described in JIS B 0601-1994, the average surface roughness (Ra) of the active material thin film formation surface of the current collector substrate is not particularly limited, but it is usually 0.05 μm or more, preferably 0.1 μm or more, particularly preferably It is 0.15 μm or more, and its upper limit is usually 1.5 μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less. When the average surface roughness (Ra) of the current collector substrate is in the range between the above-mentioned lower limit and the upper limit, favorable charge-discharge cycle characteristics can be expected. By setting it as more than the said lower limit, the interface area with an active material thin film will become large, and the adhesiveness with an active material will improve. The upper limit of the average surface roughness (Ra) is not particularly limited. If the average surface roughness (Ra) exceeds 1.5 μm, it will be difficult to obtain a foil with an appropriate thickness as a battery, so it is preferably 1.5 μm or less.

(2) Tensile strength

The tensile strength of the current collector substrate is not particularly limited, but is usually 100 N/mm ² or higher, preferably 250 N/mm ² or higher, more preferably 400 N/mm ² or higher, particularly preferably 500 N/mm ² or higher. The term "tensile strength" refers to a value obtained by dividing the maximum tensile force required for a test piece to break by the cross-sectional area of the test piece. The tensile strength in the present invention can be measured using the same apparatus and method as for measuring elongation. A current collector substrate with high tensile strength can suppress cracking of the current collector substrate due to expansion/shrinkage of the active material film during charging/discharging, thereby obtaining good cycle characteristics.

(3) 0.2% Stamina

The 0.2% proof strength of the current collector substrate is not particularly limited, but is usually 30 N/mm ² or more, preferably 150 N/mm ² or more, particularly preferably 300 N/mm ² or more. The so-called 0.2% endurance refers to the load required to produce 0.2% plastic (permanent) deformation. After applying the load of this size, the deformation of 0.2 will be maintained after removing the load. The 0.2% endurance in the present invention can be measured by the same apparatus and method as for measuring elongation. A current collector substrate with a high 0.2% endurance can suppress plastic deformation of the current collector substrate due to expansion/shrinkage of the active material film during charging/discharging, thereby obtaining good cycle characteristics.

The thickness of the metal thin film is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. In addition, the upper limit thereof is usually 1 mm or less, preferably 100 μm or less, more preferably 30 μm or less. If it is thinner than 1 μm, the strength will decrease and coating may be difficult. In addition, if it is thicker than 100 μm, the shape of the electrode may be deformed such as curling. In addition, the metal thin film may also be in the form of a mesh.

(15) The ratio of the thickness of the current collector to the active material layer

The ratio of the thickness of the current collector to the active material layer is not particularly limited, and (the thickness of the active material layer on one side before injecting the nonaqueous electrolyte)/(thickness of the current collector) is preferably 150 or less, particularly preferably 20 or less , more preferably 10 or less, the lower limit thereof is preferably 0.1 or more, more preferably 0.4 or less, and still more preferably 1 or more. If this range is exceeded, the current collector may generate heat due to Joule heat during high current density charge and discharge. If it is less than this range, the volume ratio of the current collector to the negative electrode active material may increase and the capacity of the battery may decrease.

(16) Electrode density

The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, and the density of the active material present on the current collector is preferably 1.0 g/cm ^or more, more preferably 1.2 g/cm ^or more, and even more preferably 1.3 g/cm ³ or more, and the upper limit is usually 2.0 g/cm ³ or less, preferably 1.9 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, still more preferably 1.7 g/cm ³ or less. If it exceeds this range, the active material will be destroyed, resulting in an increase in the initial irreversible capacity, and a reduction in the permeability of the non-aqueous electrolyte to the vicinity of the current collector/active material interface, resulting in deterioration of high current density charge and discharge characteristics. On the other hand, if it is less than this range, the conductivity between the active materials will decrease, the battery resistance will increase, and the battery capacity per unit volume may decrease.

(17) Adhesive

The binder for binding the active material is not particularly limited as long as it is a material stable to the non-aqueous electrolyte solution or the solvent used in producing the electrode. Specifically, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene) rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), styrene-propylene rubber and other rubber-like polymers; styrene-butadiene-styrene block Copolymer or its hydrogenated product; EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isobutylene-styrene block copolymer or its addition Thermoplastic elastomer-like polymers such as hydrogen compounds; soft resin-like polymers such as syndiotactic 1,2 polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer; polybias Fluorine polymers such as vinyl fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; polymer compositions having ion conductivity with alkali metal ions (especially lithium ions), etc. These may be used individually by 1 type, and may combine and use 2 or more types by arbitrary combinations and ratios.

The solvent used to form the slurry is not particularly limited as long as it can dissolve or disperse the active material, binder, and optionally a thickener and conductive agent, and aqueous solvents or organic solvents can be used. any of the solvents. Examples of aqueous solvents include water, alcohol, etc.; examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, acetic acid Methyl ester, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, propylene oxide, tetrahydrofuran (THF), toluene, acetone, ether, dimethylacetamide, hexamethylphosphoramide, Dimethyl sulfide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. In particular, when using a water-based solvent, add the above-mentioned thickener and dispersant at the same time, and form a slurry using a latex such as SBR. In addition, these may be used individually by 1 type, and may combine and use 2 or more types by arbitrary combinations and ratios.

The ratio of the binder to the active material is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit thereof is usually 20% by mass or less, preferably 15% by mass or less, more preferably It is 10 mass % or less, More preferably, it is the range of 8 mass % or less. If this range is exceeded, the ratio of the binder that does not contribute to the battery capacity in the amount of the binder increases, resulting in a decrease in the battery capacity in some cases. Moreover, if it is less than the said range, the intensity|strength of a negative electrode may fall. In particular, when a rubber-like polymer represented by SBR is contained in the main component, the ratio of the binder to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. The upper limit is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. In addition, when a fluorine-based polymer typified by polyvinylidene fluoride is contained in the main component, the ratio of the binder to the active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more , the upper limit thereof is usually 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less.

Thickeners are generally used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and their salts, etc. These may be used individually by 1 type, and may combine and use 2 or more types by arbitrary combinations and ratios. In addition, when adding a thickener, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is usually 5% by mass or less, preferably It is 3 mass % or less, More preferably, it is the range of 2 mass % or less. If it is less than this range, coatability may fall remarkably. If it exceeds this range, the ratio of the active material in the negative electrode active material layer decreases, which may cause a problem of a decrease in battery capacity or an increase in the resistance between the negative electrode active materials.

(18) plate orientation ratio

The electrode plate orientation ratio is preferably 0.001 or more, more preferably 0.005 or more, particularly preferably 0.01 or more, and the upper limit is a theoretical value, ie, 0.67 or less. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

The measurement of the electrode plate orientation ratio was performed as follows. The active material orientation ratio of the electrode was measured by X-ray diffraction with respect to the negative electrode pressed to the target density. The specific method is not particularly limited, but as a standard method, using asymmetric Pearson (Piason) VII as a distribution (profile) function, fitting the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, and performing The peaks were separated, and the integrated intensities of the (110) diffraction and (004) diffraction peaks were calculated respectively. From the obtained integrated intensity, the ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated. The active material orientation ratio of the electrode calculated by this measurement was defined as the plate orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα line) graphite monochromator

· Slit: divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

·Sample preparation: Fix the electrode on the glass plate with 0.1mm thick double-sided tape

(19) Impedance

The negative electrode impedance when charging to 60% of the nominal capacity from the discharged state is preferably 100Ω or less, more preferably 50Ω or less, particularly preferably 20Ω or less, and/or the electric double layer capacity is preferably 1× ^10-6 F or more, more preferably It is preferably 1×10 ^-5 F, particularly preferably 1×10 ^-4 F. Since the output characteristics are good in this range, it is preferable.

The negative electrode resistance and electric double layer capacity were measured by the following methods. The lithium secondary battery to be measured uses the following battery: After being charged with a current value that can be charged to the nominal capacity in 5 hours, it is maintained in a state where it is not charged and discharged for 20 minutes, and then, it is charged with a current value that can be charged to the nominal capacity in 1 hour. The discharge current value is discharged, and the capacity at this time is more than 80% of the nominal capacity. For the lithium secondary battery in the above discharge state, the lithium secondary battery was immediately transferred to a spherical container under an argon atmosphere by charging to 60% of the nominal capacity at a current value capable of charging to the nominal capacity in 5 hours. Quickly disassemble the lithium secondary battery in the state of no discharge or short circuit, and take out the negative electrode. If it is a double-sided coated electrode, peel off the electrode active material on one side without damaging the electrode active material on the other side. The negative electrode was punched out to 12.5 mmφ, and the separators were sandwiched so that the active material surfaces were opposed without being displaced. Between the separator and the two negative electrodes, 60 μL of the non-aqueous electrolyte solution used in the battery was added dropwise to bond them without contact with the outside world, and the current collectors of the two negative electrodes were made conductive, and an AC impedance method was performed. The measurement is carried out as follows. The complex impedance is measured at a temperature of 25°C in the frequency band of 10 ^-2 to 10 ⁵ Hz, and the arc of the negative electrode resistance component of the obtained call·call·plot is approximated as a semicircle to obtain the surface resistance. (R) and double layer capacity (Cdl).

(20) Area and thickness of the negative plate

The area of the negative plate is not particularly limited, and it is generally designed to be slightly larger than the opposite positive plate so that the positive plate will not be exposed outside the negative plate. From the point of view of repeated charge-discharge cycle life or suppression of deterioration due to high-temperature storage, if the area is as close as possible to the same area as the positive electrode, the proportion of electrodes that work uniformly and efficiently can be further increased, and the characteristics can be improved. Therefore, it is preferable . In particular, when using a large current, the design of the electrode area is important.

The thickness of the negative plate is designed according to the positive plate used, and there is no particular limitation, but the thickness of the cladding material layer after subtracting the thickness of the metal foil of the core material is usually more than 15 μm, preferably more than 20 μm, more preferably more than 30 μm, The upper limit thereof is usually 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less.

<negative pole[1]>

Hereinafter, the negative electrode [1] "negative electrode containing two or more carbonaceous materials having different crystallinity" as negative electrode active materials used in the lithium secondary battery of the present invention will be described.

[Negative electrode active material of negative electrode [1]]

Next, the negative electrode active material used for the negative electrode [1] will be described.

[[constitute]]

The negative electrode active material used in the negative electrode [1] of the lithium secondary battery of the present invention is characterized by containing two or more carbonaceous substances having different crystallinity. Here, "containing two or more carbonaceous substances with different crystallinity" means that carbonaceous substances with different crystallinity coexist in the negative electrode. In addition, the coexistence form may be in the form of individual particles and mixed together. Either contained in a secondary particle, or a mixture of the two. In addition, as the negative electrode active material, it is preferable to contain a composite carbonaceous substance containing two or more carbonaceous substances with different crystallinity, and it is more preferable to also contain one or more carbonaceous substances in the composite carbonaceous substance in the composite carbonaceous substance. Carbonaceous substances (carbonaceous materials) different in physical properties are used as auxiliary materials.

Here, "included in one secondary particle" means a state in which carbonaceous substances having different crystallinity are bonded and constrained, a state in which they are physically constrained, a state in which their shape is maintained by electrostatic confinement, and the like. The term "physical restraint" here refers to the state in which one carbonaceous substance with different crystallinity is mixed into another carbonaceous substance, and the state in which they are intertwined, and the so-called "electrostatic restraint" refers to a carbonaceous substance with different crystallinity The state of attaching to another carbonaceous substance by electrostatic energy. In addition, "a state constrained by bonding" means a chemical bond such as a hydrogen bond, a covalent bond, or an ionic bond.

Among them, in the state where at least part of the surface of the carbonaceous material serving as the core has an interface with the clad layer having different crystallinity formed by bonding, the transfer resistance of lithium between the carbonaceous material with different crystallinity is small, which is advantageous. This covering layer can be formed by bonding with externally supplied materials and/or their modified products, or by modifying the material of the surface portion of the carbonaceous substance. Here, the so-called coverage means that at least a part of the interface with the surface of the carbonaceous material has a chemical bond, and it means (1) a state covering the entire surface, (2) a state covering a part of the carbon particle, (3) selectively covering a part The state of the surface, (4) the state that exists in an extremely small region containing chemical bonds. In addition, the crystallinity may change continuously or discontinuously at the interface.

The composite carbonaceous material preferably has an interface formed by covering the particulate carbonaceous material with a carbonaceous material different in crystallinity from the particulate carbonaceous material, and/or the particulate carbonaceous material is bonded with a crystallinity and The particulate carbonaceous material is an interface formed by different carbonaceous materials, and the crystallinity of the interface changes continuously and/or discontinuously. Which of the "particulate carbonaceous material" and "the carbonaceous material different in crystallinity from the particulate carbonaceous material" has higher crystallinity is not particularly limited, but when the crystallinity of the particulate carbonaceous material is high, the Since the above-mentioned effects of the present invention are achieved, it is preferable.

Here, the difference in crystallinity is judged by the difference in the interplanar distance (d002) of the (002) plane measured by the X-ray wide-angle diffraction method, the difference in Lc, and the difference in La. From the point of view of expressing the effect of the present invention, Preferably, the difference in crystallinity in terms of (d002) is 0.0002 nm or more, or La is 1 nm or more, or Lc is 1 nm or more. In the above range, the difference in (d002) is preferably 0.0005 nm or more, more preferably 0.001 nm or more, still more preferably 0.003 nm or more, and the upper limit thereof is usually 0.03 nm or less, preferably 0.02 nm or less. If it is less than this range, the effect due to the difference in crystallinity may become small. On the other hand, if it exceeds the above-mentioned range, the crystallinity of the part with low crystallinity tends to decrease, and the irreversible capacity caused by this may increase. In addition, in the above-mentioned range, the difference in La or Lc is preferably 2 mm or more, more preferably 5 nm or more, and still more preferably 10 nm or more. Generally, graphite is not defined above 100nm, so no upper limit can be specified. If it is less than this range, the effect due to the difference in crystallinity may become small.

A composite carbonaceous substance is formed by covering and/or bonding a carbonaceous substance different in crystallinity from the particulate carbonaceous substance on the particulate carbonaceous substance, and "particulate carbonaceous substance" and "with the granular carbonaceous substance" "Carbonaceous substances with different crystallinity of carbonaceous substances" as long as any one is graphite-like carbonaceous substances, and the other is low-crystalline carbonaceous substances. In addition, it is preferable that "particulate carbonaceous substances" be graphite-like carbonaceous substances , and "a carbonaceous substance different in crystallinity from the particulate carbonaceous substance" is a low-crystalline carbonaceous substance.

[[[Particulate carbonaceous matter]]]

As the particulate carbonaceous substance, it is preferable to contain natural graphite and/or a graphite-like carbonaceous substance containing artificial graphite, or to contain at least one selected from (a), (b) and (c) which are slightly lower in crystallinity than them. carbonaceous matter,

(a) Thermal decomposition products of organic matter selected from coal coke, petroleum coke, furnace black, acetylene black, and pitch-based carbon fibers;

(b) carbides of organic gases;

(c) A carbonaceous material obtained by graphitizing part or all of (a) or (b).

[[[[Graphite carbonaceous substances]]]]

The particulate carbonaceous material is preferably a graphitic carbonaceous material containing natural graphite and/or artificial graphite. The graphitic carbonaceous substance refers to various carbonaceous substances with high crystallinity whose interplanar distance (d002) of the (002) plane measured by X-ray wide-angle diffraction method is less than 0.340 nm.

As a specific example of graphite-based carbonaceous substances, powders selected from the following products are preferred: natural graphite, artificial graphite, or their mechanically pulverized products, reheated products, reheated products of expanded graphite, or high-purity refined products of these graphites . As a specific example of the above-mentioned artificial graphite, one or more organic substances are preferably graphitized at a sintering temperature of about 2500° C. to 3200° C., and then pulverized by an appropriate pulverization method. The organic substances Selected from: coal tar pitch, coal heavy oil, atmospheric residual oil, petroleum heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile , polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenolic resin, imide resin, etc.

(Physical properties of graphitic carbonaceous material)

The properties of the graphitic carbonaceous substance preferably simultaneously satisfy any one or more of (1) to (11) shown below.

(1) X-ray parameters

The graphitic carbonaceous material preferably has a d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction using the Gakushin method of 0.335 nm or more. In addition, from the definition, the lower limit is less than 0.340 nm, preferably 0.337 nm or less. If the d value is too large, the crystallinity may decrease, which may increase the initial irreversible capacity. On the other hand, 0.335 is the theoretical value of graphite. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually in the range of 30 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. If it is less than this range, the crystallinity may decrease and the initial irreversible capacity may increase.

(2) Ash content

The ash contained in the graphite-like carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, with a lower limit of 1 ppm or more based on the total mass of the graphite-like carbonaceous material. If the above-mentioned range is exceeded, the degradation of battery performance due to the reaction with the electrolytic solution during charging and discharging cannot be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Volume-based average particle size

The volume-based average particle size of the graphitic carbonaceous material is the volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method, and is usually more than 1 μm, preferably more than 3 μm, more preferably more than 5 μm, More preferably, it is 7 μm or more. In addition, the upper limit thereof is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, particularly preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode pad, and it may be unpreferable in a battery manufacturing process.

In the present invention, the volume-based average particle diameter is defined by a median particle diameter measured by dispersing carbon powder in polyoxyethylene (20) sorbitan as a surfactant. In a 0.2% by mass aqueous solution (about 1 mL) of monolaurate, it measures using a laser diffraction/scattering particle size distribution meter (for example, LA-700 manufactured by Horiba, Ltd.).

(4) Raman R value, Raman half value width

The R value of the graphitic carbonaceous material measured by argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.03 or more, more preferably 0.10 or more, and its upper limit is usually 0.60 or less, preferably 0.40 or less. If the R value is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and the reactivity with the electrolyte solution increases, resulting in a decrease in efficiency or an increase in gas generation.

In addition, the Raman half-value width of graphitic carbonaceous material around 1580 cm ^-1 is not particularly limited, but it is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and the upper limit is usually 60 cm ^-1 or less, preferably 45 cm ^-1 or less , more preferably in the range of 40 cm ^-1 or less. If the Raman half-value width is below this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, and the reactivity with the electrolytic solution will increase, which may result in a decrease in efficiency or an increase in generated gas.

The measurement of the Raman spectrum is carried out as follows: Using a Raman spectrometer (such as a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped and filled in the measurement cell, and the surface of the sample in the cell is irradiated with an argon ion laser. At the same time, Rotate the cell in a plane perpendicular to the laser. For the obtained Raman spectrum, the intensity I _A of the peak PA near 1580 cm ^-1 and the intensity I _B of the peak P _B near 1360 cm ^-1 were measured _, and the intensity ratio R (R= _IB / _IA ) was calculated. It is defined as the Raman R value of the carbon material. In addition, the half-value width of the peak _PA in the vicinity of 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the carbon material.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

R value, half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

(5) BET specific surface area

The specific surface area of the graphitic carbonaceous material of the present invention measured by the BET method is usually 0.1 m ² /g or more, preferably 0.7 m ² /g or more, more preferably 1 m ² /g or more, still more preferably 1.5 m ^{2 /g} or more. more than g. The upper limit thereof is usually 100 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. If the value of the specific surface area is less than the above range, when used as a negative electrode, the acceptability of lithium will deteriorate during charging, and lithium will be easily deposited on the surface of the electrode. On the other hand, when it exceeds the above-mentioned range, when used as a negative electrode material, the reactivity with the electrolytic solution increases and gas generation increases, making it difficult to obtain a preferable battery in some cases.

The BET specific surface area is defined as a value measured as follows: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then, using nitrogen gas relative to The relative pressure value of the atmospheric pressure is accurately adjusted to 0.3 nitrogen-helium mixed gas, and it is measured by the nitrogen adsorption BET 1-point method using the gas flow method.

(6) Micropore distribution

As a graphitic carbonaceous material, the amount corresponding to the voids in the particles with a diameter of 0.01 μm to 1 μm and the unevenness of the particle surface obtained by mercury porosimetry (mercury porosimetry) is usually 0.01 mL /g or more, preferably 0.05mL/g or more, more preferably 0.1mL/g or more, the upper limit is usually 0.6mL/g or less, preferably 0.4mL/g or less, more preferably 0.3mL/g or less. If it exceeds this range, a large amount of binder will be required to manufacture an electrode plate. On the other hand, if it is less than this range, the high current density charge-discharge characteristics deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of the sample (negative electrode material) was weighed, sealed in a powder container, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, the pressure is reduced to 4psia (about 28kPa), mercury is introduced, the pressure is raised from 4psia (about 28kPa) to 40000psia (about 280MPa) in steps, and then the pressure is lowered to 25psia (about 170kPa). The number of stages at the time of pressurization was 80 or more, and the amount of mercury intrusion was measured after a 10-second equilibration time in each stage. The pore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

(7) Circularity

Using the degree of circularity as the degree of spherical shape of the graphite-like carbonaceous material, the circularity of the particles of the graphite-like carbonaceous material having a particle size in the range of 3 to 40 μm is preferably 0.1 or more, particularly preferably 0.5 or more, more preferably 0.8 or more , more preferably 0.85 or more, most preferably 0.9 or more. When the circularity is large, the high current density charge and discharge characteristics are improved, which is preferable. The circularity is defined by the following formula, and when the circularity is 1, it becomes a theoretical true sphere.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the value measured as follows is used: using, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) as a surfactant. In a 0.2% by mass aqueous solution of sorbitan monolaurate (approximately 50mL), after irradiating 28kHz ultrasonic waves with an output power of 60W for 1 minute, specify a detection range of 0.6 to 400μm, and perform a test on particles in the range of particle diameters from 3 to 40μm. Determination.

There is no particular limitation on the method of improving the circularity, but it is preferable to make the shape of the gap between the particles uniform when the electrode body is produced by performing a spheroidization treatment to make it spherical. Examples of spheroidization treatment include a method of mechanically approaching a spherical shape by applying a shearing force or a compressive force; a mechanical/physical treatment method of granulating a plurality of fine particles by means of a binder or the adhesive force of the particles themselves wait.

(8) True density

The true density of the graphite-like carbonaceous material is usually above 2 g/cm ³ , preferably above 2.1 g/cm ³ , more preferably above 2.2 g/cm ³ , and even more preferably above 2.22 g/cm ³ , with an upper limit of 2.26 g /cm ³ or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase. In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

(9) Tap density

The tap density of the graphitic carbonaceous material is usually 0.1 g/cm ³ or higher, preferably 0.5 g/cm ³ or higher, more preferably 0.7 g/cm ³ or higher, particularly preferably 0.9 g/cm ³ or higher. In addition, the upper limit thereof is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. If the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm and dropped in a ²⁰ cm container for vibration until the sample is filled with the upper end surface of the container, and a powder density measuring device (for example, Seishin Enterprise Co., Ltd. manufactured Tap densor), vibrate 1000 times with a stroke length of 10mm, and define the bulk density at this time as the tap density.

(10) Orientation ratio (powder)

The orientation ratio of the graphitic carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

·Slit:

Divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

(11) aspect ratio (powder)

The aspect ratio of the graphitic carbonaceous material is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of the carbon material particle and the shortest diameter B perpendicular thereto when viewed three-dimensionally. Observation of carbon particles was performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of the metal with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

[[[[Low crystalline carbonaceous substances]]]]

The low-crystalline carbonaceous substance refers to a carbonaceous substance with low crystallinity whose interplanar distance (d002) of the (002) plane measured by X-ray wide-angle diffractometry is 0.340 nm or more.

(Composition of low crystalline carbonaceous substances)

The "carbonaceous substance different from the crystals of the particulate carbonaceous substance" is preferably a low-crystalline carbonaceous substance having lower crystallinity than the particulate carbonaceous substance. In addition, carbides of the following (d) or (e) are particularly preferred.

(d) selected from coal-based heavy oil, straight-run heavy oil, decomposed petroleum-based heavy oil, aromatic hydrocarbons, N-ring compounds, S-ring compounds, polyphenylene, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins carbonizable organic matter;

(e) A solution obtained by dissolving these carbonizable organic substances in a low-molecular organic solvent.

As coal heavy oil, coal tar pitch from soft asphalt to hard asphalt or dry distillation liquefied oil, etc. are preferred; as straight run heavy oil, atmospheric residual oil, vacuum residual oil, etc. are preferred; as decomposed petroleum heavy oil, crude oil, petroleum Ethylene tar, etc., which are by-produced during thermal decomposition of naphtha, etc.; as aromatic hydrocarbons, preferably acenaphthylene, decacyclene, anthracene, phenanthrene, etc.; as N-ring compounds, preferably phenazine, acridine, etc.; as S-ring compounds, preferably Thiophene, bithiophene, etc.; as polyphenylene, biphenyl, terphenyl, etc. are preferred; as organic polymers, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, their insoluble processed products, polyacrylonitrile , polypyrrole, polythiophene, polystyrene, etc.; as natural polymers, preferably polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, sucrose, etc.; as thermoplastic resins, preferably Polyphenylene sulfide, polyphenylene ether, etc.; as the thermosetting resin, furfuryl alcohol resin, phenolic resin, imide resin, etc. are preferable.

"Carbonaceous substances different in crystallinity from particulate carbonaceous substances" are preferably carbides of the above-mentioned "carbonizable organic substances", and it is also preferable to dissolve these "carbonizable organic substances" in benzene, toluene, xylene, quinoline, etc. , n-hexane and other low-molecular organic solvents to obtain carbides such as solutions. In addition, the "carbonaceous substance different in crystallinity from the particulate carbonaceous substance" is preferably a carbide of coal-based coke or petroleum-based coke.

As the above (d) or (e), a liquid state is particularly preferable. That is, from the viewpoint of partially forming an interface with the graphitic carbonaceous material, carbonization is preferably performed in the liquid phase.

(Physical properties of low crystalline carbonaceous material)

The physical properties as the low-crystalline carbonaceous substance preferably satisfy any one or more of the following (1) to (5) at the same time. In addition, one kind of low-crystalline carbonaceous material exhibiting these physical properties may be used alone, or two or more kinds may be used in combination in any combination and ratio.

(1) X-ray parameters

For the low-crystalline carbonaceous material part, the d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method is by definition 0.340 nm or more, preferably 0.340 nm or more, particularly preferably 0.341 nm or more. In addition, the upper limit thereof is 0.380 nm or less, particularly preferably 0.355 nm or less, further preferably 0.350 nm or less. If the d value is too large, a surface with significantly low crystallinity is formed, which may increase the irreversible capacity, and if the d value is too small, the effect of improving charge acceptance by providing a low-crystalline carbonaceous material on the surface becomes small, Thus, the effect of the present invention becomes small. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually 1 nm or more, preferably 1.5 nm or more. If it is less than this range, the crystallinity is lowered, and the increase of the initial irreversible capacity may be increased.

(2) Ash content

The ash contained in the low-crystalline carbonaceous material part is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less with respect to the total mass of the composite carbonaceous material. The lower limit is preferably 1 ppm or more . If the above-mentioned range is exceeded, the degradation of battery performance due to the reaction with the electrolytic solution during charging and discharging cannot be ignored. On the other hand, if it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Raman R value, Raman half value width

The R value of the low crystalline carbonaceous material portion measured by argon ion laser Raman spectroscopy is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and its upper limit is usually 1.5 or less, preferably 1.2 or less. If the R value is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. In addition, when the anode is densified by pressing after coating on the current collector, the crystals tend to be oriented in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and the reactivity with the electrolyte solution increases, resulting in a decrease in efficiency or an increase in gas generation.

In addition, the Raman half-value width of the low-crystalline carbonaceous material part is not particularly limited in the vicinity of 1580 cm ^-1 , but it is usually 40 cm ^{-1 or} more, preferably 50 cm ^-1 or more, and its upper limit is usually 100 cm-1 or less, preferably 100 cm ^{-1 or} less. 90 cm ^-1 or less, more preferably 80 cm ^-1 or less. If the Raman half-value width is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. In addition, when the anode is densified by pressing after coating on the current collector, the crystals tend to be oriented in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and the reactivity with the electrolyte solution increases, resulting in a decrease in efficiency or an increase in gas generation.

(4) True density

The true density of the low-crystalline carbonaceous material part is usually 1.4 g/cm ³ or more, preferably 1.5 g/cm ³ or more, more preferably 1.6 g/cm ³ or more, and even more preferably 1.7 g/cm ³ or more, the upper limit of which is Usually 2.1 g/cm ³ or less, preferably 2 g/cm ³ or less. If this range is exceeded, charge acceptance may be impaired. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

(5) Orientation ratio (powder)

The orientation ratio of the low-crystalline carbonaceous material portion is usually not less than 0.005, preferably not less than 0.01, more preferably not less than 0.015, and the upper limit thereof is not more than a theoretical value of 0.67. If it is less than this range, the high-density charge-discharge characteristics may deteriorate, which is not preferable. The orientation ratio was measured by X-ray diffraction. Use asymmetric Pearson VII as the distribution function, fit the peaks of (110) diffraction and (004) diffraction obtained by carbon through X-ray diffraction, carry out peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively Integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the active material orientation ratio.

[[[Composite carbonaceous material]]]

The composite carbonaceous material used in the negative electrode [1] in the lithium secondary battery of the present invention preferably contains "particulate carbonaceous material" and "a carbonaceous material different in crystallinity from the particulate carbonaceous material". In this case, It is only necessary that any one of them is a graphitic carbonaceous substance and the other is a low-crystalline carbonaceous substance. In addition, it is preferable that the "particulate carbonaceous substance" is a graphitic carbonaceous substance, and the "carbonaceous substance different in crystallinity from the particulate carbonaceous substance" is a low-crystalline carbonaceous substance.

In the composite carbonaceous material, the mass ratio of the graphite-like carbonaceous material and the low-crystalline carbonaceous material is preferably 50/50 or more, more preferably 80/20 or more, particularly preferably 90/10 or more, and preferably 99.9/20 or more. 0.1 or less, more preferably 99/1 or less, particularly preferably 98/2 or less. If it exceeds the above range, the effect of having two kinds of crystalline carbonaceous substances may not be obtained, and if it is below the above range, the initial irreversible capacity tends to increase, which may cause problems in battery design. The graphite-based carbonaceous substance is 50 mass % or more with respect to the whole composite carbonaceous substance.

(Physical properties of composite carbonaceous material)

As the composite carbonaceous substance, it is preferable to satisfy any one or more of the following (1) to (11) at the same time. In addition, one kind of composite carbonaceous material exhibiting these physical properties may be used alone, or two or more kinds may be used in combination in any combination and ratio.

(1) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) obtained by the X-ray diffraction of the composite carbonaceous material is preferably 0.335nm or more, and is usually 0.350nm or less, preferably 0.345nm or less, more Preferably it is 0.340 nm or less. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually 1.5 nm or more, preferably 3.0 nm or more. If it is less than this range, the crystallinity may decrease, which may increase the increase in the initial irreversible capacity.

(2) Ash content

The ash contained in the composite carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less with respect to the total mass of the composite carbonaceous material, and the lower limit thereof is preferably 1 ppm or more. If the above-mentioned range is exceeded, the degradation of battery performance due to the reaction with the electrolytic solution during charging and discharging cannot be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Volume-based average particle size

The volume-based average particle size of the composite carbonaceous material is the volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method, usually more than 1 μm, preferably more than 3 μm, more preferably more than 5 μm, and further It is preferably 7 μm or more. In addition, the upper limit thereof is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, particularly preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode plate, and it may be unpreferable in a battery manufacturing process.

(4) Raman R value, Raman half value width

The R value of the composite carbonaceous material measured by argon ion laser Raman spectroscopy is usually 0.03 or more, preferably 0.10 or more, more preferably 0.15 or more, and its upper limit is usually 0.60 or less, preferably 0.50 or less. If the R value is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. In addition, when the anode is densified by pressing after coating on the current collector, the crystals tend to be oriented in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and the reactivity with the electrolyte solution increases, resulting in a decrease in efficiency or an increase in gas generation.

In addition, the Raman half-value width of the composite carbonaceous material in the vicinity of 1580 cm ^-1 is not particularly limited, and is usually 15 cm ^-1 or more, preferably 20 cm ^-1 or more, and its upper limit is usually 70 cm ^-1 or less, preferably 60 cm ^-1 or less, more preferably in the range of 50 cm ^-1 or less. If the Raman half-value width is below this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. In addition, when the anode is densified by pressing after coating on the current collector, the crystals tend to be oriented in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and the reactivity with the electrolyte solution increases, resulting in a decrease in efficiency or an increase in gas generation.

(5) BET specific surface area

The specific surface area of the composite carbonaceous material of the present invention measured by the BET method is usually 0.1 m ² /g or more, preferably 0.7 m ² /g or more, more preferably 1 m ² /g or more, and still more preferably 1.5 m ² /g above. The upper limit thereof is usually 100 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. If the value of the specific surface area is less than the above range, when used as a negative electrode material, the acceptance of lithium at the time of charging will be deteriorated, and lithium will be easily deposited on the surface of the electrode. On the other hand, if it exceeds the above-mentioned range, when used as a negative electrode material, the reactivity with the electrolytic solution increases and the gas generated increases, making it difficult to obtain a preferable battery.

(6) Micropore distribution

As a composite carbonaceous material, the amount of voids in particles with a diameter of 0.01 μm to 1 μm and the amount of unevenness caused by particle surface is usually 0.01 mL/ g or more, preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, and the upper limit is usually 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder will be required to produce a pole plate. If it is less than this range, the high current density charge-discharge characteristics will deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when it is made into an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 80 μm or less, preferably 50 μm or less, more preferably 20 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the high current density charge and discharge characteristics may deteriorate.

(7) Circularity

Using the circularity as the degree of sphericity of the composite carbonaceous material, the circularity of particles of the composite carbonaceous material having a particle size in the range of 3 to 40 μm is preferably 0.85 or more, more preferably 0.87 or more, and still more preferably 0.9 or more. When the circularity is large, the high current density charge and discharge characteristics are improved, which is preferable.

(8) True density

The true density of the composite carbonaceous material is usually above 1.9 g/cm ³ , preferably above 2 g/cm ³ , more preferably above 2.1 g/cm ³ , even more preferably above 2.2 g/cm ³ , and its upper limit is 2.26 g/cm 3 or above. ^cm3 or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

(9) Tap density

The tap density of the composite carbonaceous material is usually 0.1 g/cm ³ or more, preferably 0.5 g/cm ³ or more, more preferably 0.7 g/cm ³ or more, particularly preferably 1 g/cm ³ or more. In addition, the upper limit thereof is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. When the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics. The tap density is measured by the same method as described above, and is defined according to the method.

(10) Orientation ratio (powder)

The orientation ratio of the composite carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, the high-density charge and discharge characteristics may deteriorate.

(11) aspect ratio (powder)

The aspect ratio of the composite carbonaceous material is theoretically 1 or more, and its upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge-discharge characteristics may deteriorate.

(Manufacturing method of composite carbonaceous material)

The method for producing these composite carbonaceous materials is not particularly limited, and the methods shown below are exemplified.

The compounding of graphite-like carbonaceous substance and low-crystalline carbonaceous substance can adopt the following method: directly use the carbon precursor for obtaining low-crystalline carbonaceous substance, and heat-treat the mixture of carbon precursor and graphite-like carbonaceous substance powder , the method of obtaining composite powder; the above-mentioned carbon precursor is partially carbonized, and the low-crystalline carbonaceous substance powder is prepared in advance, and then mixed with the graphite-like carbonaceous substance powder, and the method for compounding by heat treatment; the above-mentioned low-crystalline carbonaceous substance powder is prepared in advance. Carbonaceous substance powder, a method of mixing graphite-like carbonaceous substance powder, low-crystalline carbonaceous substance powder and carbon precursor, heating and compounding, etc. In addition, in the latter two methods of preparing low-crystalline carbonaceous material powder in advance, it is preferable to use low-crystalline carbonaceous material particles whose average particle diameter is one-tenth or less of the average particle diameter of graphite-based carbonaceous material. In addition, the following method can also be used: by applying mechanical energy such as pulverization to prefabricated low-crystalline carbonaceous substances and graphite-like carbonaceous substances, a structure in which one substance is mixed into another substance, or a structure in which one substance is electrostatically attached Methods.

Preferably, the mixture of the graphite-like carbonaceous material particles and the carbon precursor is heated to obtain an intermediate substance, or the mixture of the graphite-like carbonaceous material particles and the low-crystalline carbonaceous material particles is mixed with the carbon precursor The obtained mixture is heated to obtain an intermediate substance, which is then carbonized, sintered, and pulverized to finally obtain a composite carbonaceous substance in which a low-crystalline carbonaceous substance is composited in graphite-like substance particles.

The manufacturing process for obtaining a composite carbonaceous material is divided into the following 4 processes.

Step 1: Mix (graphite carbonaceous particles or (mixed particles of graphite carbonaceous particles and low-crystalline carbonaceous particles)) and low-crystalline carbon using various commercially available mixers or kneaders. The carbon precursor of the substance particle and, if necessary, a solvent are mixed to obtain a mixture.

Second step: heating the mixture to obtain an intermediate substance from which the solvent and the volatile components generated from the carbon precursor have been removed. At this time, stirring the above-mentioned mixture can be performed as needed. Also, even if volatile components remain, they can be removed in the subsequent third step, so there is no problem.

Step 3: In an inert gas atmosphere such as nitrogen, carbon dioxide, and argon, heat the above mixture or intermediate substance to 400° C. to 3200° C. to obtain a graphite-low crystalline carbonaceous material composite.

Step 4: If necessary, powder processing such as pulverization, crushing, and classification treatment is performed on the above-mentioned composite substance.

Among these steps, the second step and the fourth step may be omitted depending on circumstances, and the fourth step may be performed before the third step. However, when the fourth step is carried out before the third step, powder processing such as pulverization, crushing, and classification is performed again as necessary to obtain a composite carbonaceous material.

In addition, heat history temperature conditions are important as heat treatment conditions in the third step. The lower limit of the temperature varies depending on the type of carbon precursor and the heat history, but is usually 400°C or higher, preferably 900°C or higher. On the other hand, the upper limit temperature may reach a temperature at which there is substantially no structural order beyond the crystal structure of the graphite-like carbonaceous material particle nucleus. Therefore, the upper limit temperature of the heat treatment is usually not higher than 3200°C, preferably not higher than 2000°C, and more preferably not higher than 1500°C. Under such heat treatment conditions, the heating rate, cooling rate, heat treatment time, etc. can be set arbitrarily according to the purpose. In addition, after performing heat treatment in a relatively low temperature range, the temperature may be raised to a predetermined temperature. In addition, the reactor used in this step may be a batch type or a continuous type, and may be one or multiple.

[[Vice material mix]]

In addition to the above-mentioned composite carbonaceous substance, the negative electrode active material of the lithium secondary battery of the present invention contains one or more carbonaceous substances (carbonaceous materials) different from the above-mentioned composite carbonaceous substance in terms of carbonaceous physical properties, thereby Further improvement in battery performance can be achieved. The "carbonaceous physical properties" mentioned here refer to X-ray diffraction parameters, median particle size, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, micropore distribution, One or more properties of circularity, gray content. In addition, as a preferred embodiment, the volume-based particle size distribution is asymmetrical around the median particle size, contains two or more carbonaceous materials with different Raman R values, or has different X-ray parameters. As an example of the effect, reduction of electrical resistance by including carbon materials such as graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and amorphous carbon such as needle coke as sub-materials can be cited. These may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary and arbitrary ratios. When added as an auxiliary material, the amount added is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is 80% by mass or less, preferably 50% by mass or less, more preferably 40% by mass % or less, more preferably in the range of 30% by mass or less. If it is less than this range, it may be difficult to obtain the effect of improving electrical conductivity. If the above range is exceeded, the initial irreversible capacity may increase.

[Making the Negative [1] Electrode]

A common method can be used to manufacture the negative electrode [1], and the negative electrode [1] can be formed in the same manner as above. The current collector, the thickness ratio between the current collector and the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

<Negative pole [2]>

Next, the negative electrode [2] used in the lithium secondary battery of the present invention will be described. The negative electrode contains, as an active material, an amorphous carbonaceous substance whose (002) plane surface is measured by a wide-angle X-ray diffraction method. Raman R defined by the ratio of the peak intensity at 1360 cm ^-1 to the peak intensity at 1580 cm ^-1 in argon ion laser Raman spectroscopy with a spacing (d002) of 0.337 nm or more and a crystallite size (Lc) of 80 nm or less The value is 0.2 or more.

[Negative electrode active material of the negative electrode [2]]

Next, the negative electrode active material used in the negative electrode [2] will be described.

The negative electrode active material used in the negative electrode [2] of the lithium secondary battery of the present invention is an amorphous carbonaceous material containing at least the following (a), (b) and (c).

(a) The interplanar distance (d002) of the (002) plane measured by wide-angle X-ray diffraction method is 0.337nm or more;

(b) The crystallite size Lc of the (002) plane measured by wide-angle X-ray diffraction method is below 80nm;

(c) The Raman R value defined by the ratio of the peak intensity at 1360 cm ^-1 to the peak intensity at 1580 cm ^-1 in argon ion laser Raman spectroscopy (hereinafter, sometimes simply referred to as "Raman R value") is 0.2 above.

The negative active material used in the present invention contains at least amorphous carbonaceous meeting (a), (b) and (c), the content of these amorphous carbonaceous in the total negative active material is preferably more than 10% by mass, more preferably It is 50% by mass or more, particularly preferably 100% by mass, that is, all active materials are amorphous carbonaceous. The negative electrode active material used in combination with amorphous carbon is not particularly limited, and known negative electrode active materials such as artificial graphite and natural graphite can be used.

[[Space between faces (d002), Lc]]

In the lithium secondary battery of the present invention, the interplanar distance (d002) of the (002) plane measured by the wide-angle X-ray diffraction method of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] is 0.337 nm or more, preferably 0.34 nm above. The upper limit thereof is usually 0.39 nm or less, preferably 0.38 nm or less, more preferably 0.37 nm or less, still more preferably 0.36 nm or less, particularly preferably 0.35 nm or less. If it exceeds this range, the crystallinity will be remarkably reduced, and the reduction in the electrical conductivity between particles cannot be ignored, and it may be difficult to obtain the effect of improving the short-time high current density charge-discharge characteristics. On the other hand, if it is less than this range, the crystallinity becomes too high, and it may be difficult to obtain the effect of improving the short-time high current density charge-discharge characteristics.

The interplanar spacing (d002) of the (002) plane measured by the wide-angle X-ray method in the present invention refers to the d value (interlayer distance) of the lattice plane (002) plane obtained by X-ray diffraction using the Xuezhen method. ).

The crystallite size (Lc) of the (002) plane of the amorphous carbonaceous obtained by X-ray diffraction measured by the Gakushin method is 80 nm or less, preferably 35 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less. The lower limit thereof is usually 0.1 nm or more, preferably 1 nm or more. If it is less than this range, the crystallinity is remarkably reduced, and the reduction in the conductivity between particles may not be ignored, and it may be difficult to obtain the effect of improving charge and discharge at a high current density in a short time. On the other hand, if it exceeds this range, the crystallinity becomes too high, and it may be difficult to obtain the effect of improving short-time high current density charge and discharge.

[[Raman R value]]

The Raman R value of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] in the lithium secondary battery of the present invention must be 0.2 or more, preferably 0.5 or more, particularly preferably 0.7 or more, more preferably 0.8 or more. The upper limit thereof is usually 1.5 or less, more preferably 1.2 or less. If the Raman R value is lower than this range, the crystallinity of the particle surface is too high and the charge acceptance is lowered, so it may be difficult to obtain the effect of improving the short-time high current density charge-discharge characteristics. On the other hand, if it exceeds this range, the crystallinity of the surface of the particles will decrease significantly, so the contact resistance between the particles will increase, and it may be difficult to obtain the effect of improving charge and discharge at a high current density in a short time.

The measurement of the Raman spectrum is carried out as follows: using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped into the measurement container, and the sample is filled. The surface of the sample is irradiated with an argon ion laser while the container is rotated in a plane perpendicular to the laser. For the obtained Raman spectrum, measure the intensity I _A of the peak PA at 1580 cm ^-1 and the intensity I _B of the peak P _B at 1360 cm ^-1 , calculate the _intensity ratio R (R= _IB / _IA ), and define it as is the Raman R value of the amorphous carbonaceous. In addition, the half-value width of the peak _PA at 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of amorphous carbonaceous.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

Raman R value, Raman half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

In addition, in the lithium secondary battery of the present invention, the Raman half-value width of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] is not particularly limited at 1580 cm ^-1 , and is usually more than 20 cm ^-1 , preferably 25 cm ^-1 or more, and the upper limit is usually 150 cm ^-1 or less, preferably 140 cm ^-1 or less. If the Raman half-value width is less than this range, the crystallinity of the particle surface becomes too high, and the charge acceptance decreases. Therefore, it may be difficult to obtain the effect of improving short-time high current density charge and discharge. On the other hand, if it exceeds the above-mentioned range, the crystallinity of the particle surface will be significantly reduced, so the contact resistance between particles will increase, and it may be difficult to obtain the effect of improving charge and discharge at a high current density in a short time. However, the Raman half-value width cannot sometimes be judged from the peak shape.

The amorphous carbon used in the present invention satisfies the above-mentioned interplanar spacing (d002), crystallite size (Lc) and Raman R value conditions, but from the point of view of battery balance, it is more preferable to satisfy the following items at the same time Any one or more conditions. Among these, it is particularly preferable to simultaneously satisfy any one of true density, H/C value, O/C value, tap density, BET specific surface area, micropore volume in the range of 0.01 μm to 1 μm, ash content, and volume average particle diameter. or multiple conditions.

[[true density]]

The true density of amorphous carbonaceous is usually 2.22 g/cm ³ or less, preferably 2.2 g/cm ³ or less, more preferably 2.1 g/cm ³ or less, still more preferably 2.0 g/cm ³ or less, and its lower limit is usually 1.4 g/cm ³ or more, preferably 1.5 g/cm ³ or more, more preferably 1.6 g/cm ³ or more, still more preferably 1.7 g/cm ³ or more, particularly preferably 1.8 g/cm ³ or more. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase. If it exceeds this range, the crystallinity of carbon will be too high, and it will be difficult to obtain the effect of improving charging and discharging at a high current density in a short time.

In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

[[O/C value]]

The upper limit of the atomic ratio O/C value of amorphous carbon is usually 0.15 or less, preferably 0.1 or less, more preferably 0.05 or less, further preferably 0.03 or less, and the lower limit is usually 0 or more, preferably 0.01 or more.

The O/C value represents the ratio of the molar concentration of oxygen atoms present in amorphous carbon to the molar concentration of carbon atoms, and is an index representing the amount of functional groups such as carboxyl groups, phenolic hydroxyl groups, and carbonyl groups. Amorphous carbon with a large O/C value often has oxygen-containing functional groups bonded to the end faces of carbon crystallites. When the O/C value exceeds the above range, the irreversible capacity may increase.

[[H/C value]]

The upper limit of the atomic ratio H/C value of amorphous carbon is usually 0.3 or less, preferably 0.15 or less, more preferably 0.1 or less, further preferably 0.08 or less, and the lower limit is usually 0 or more, preferably 0.01 or more.

The H/C value represents the ratio of the molar concentration of hydrogen atoms present in the amorphous carbonaceous substance to the molar concentration of carbon atoms, and is an index showing the amount of hydrogen present on the crystallite end faces of the amorphous carbonaceous substance. An amorphous carbonaceous material with a large H/C value often indicates that the amount of carbon such as crystallite end surfaces of carbon on the particle surface is greater than that of carbon. If the H/C value exceeds the above range, the irreversible capacity may increase.

The "O/C value" and "H/C value" mentioned in the present invention are determined by CHN elemental analysis shown below.

[[CHN Elemental Analysis]]

The amorphous carbon to be measured was dried under reduced pressure at 120° C. for about 15 hours, and then dried on a hot plate in a drying oven at 100° C. for 1 hour. Next, in an argon atmosphere, the sample was placed in an aluminum cup, and the carbon content was obtained from the weight of carbon dioxide gas generated by combustion, and the hydrogen content was obtained from the weight of water generated, and the nitrogen dioxide gas generated was obtained by The nitrogen content was calculated by weight, and the inorganic substance content was obtained from the weight of the residue remaining after combustion. The value of the oxygen content is obtained by subtracting the carbon content, the hydrogen content, the nitrogen content, and the inorganic content from the total weight. The number of moles was calculated from these values, and the O/C value and the H/C value were obtained by the following formula using the obtained mole numbers of each content.

O/C value = moles of oxygen/moles of carbon

H/C value = moles of hydrogen/moles of carbon

[[Tap Density]]

The tap density of the amorphous carbonaceous used as the active material of the negative electrode [2] in the lithium secondary battery of the present invention is preferably 0.1 g/cm ³ or more, more preferably 0.2 g/cm ³ or more, still more preferably 0.5 g /cm ³ or more, particularly preferably 0.7 g/cm ³ or more. In addition, the upper limit thereof is preferably 1.4 g/cm ³ or less, more preferably 1.2 g/cm ³ or less, particularly preferably 1.1 g/cm ³ or less. If the tap density is lower than this range, it will be difficult to increase the packing density when used as a negative electrode, and the contact area between particles will decrease, so the impedance between particles will increase, and the short-term high current density charge and discharge characteristics may be reduced. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, and the flow path of the nonaqueous electrolyte solution will be reduced, so the short-time high current density charge and discharge characteristics may be reduced.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm, the sample is dropped into a ²⁰ cm container for vibration, and after the sample is filled with the upper end of the container, a powder density measuring device (such as , Tap densor manufactured by Seishin Enterprise Co., Ltd.), vibration with a stroke length of 10 mm was performed 1000 times, and the density obtained from the volume at that time and the weight of the sample was taken as the tap density.

[[BET specific surface area]]

In the lithium secondary battery of the present invention, the specific surface area of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] measured by the BET method is preferably 0.1 m ² /g or more, particularly preferably 0.5 m ² /g or more, and more preferably Preferably it is 0.7 m ² /g or more, and more preferably 1.5 m ² /g or more. The upper limit thereof is preferably 100 m ² /g or less, particularly preferably 50 m ² /g or less, more preferably 25 m ² /g or less, and still more preferably 15 m ² /g or less. If the value of the BET specific surface area is below this range, when used as a negative electrode material, lithium acceptance during charge tends to deteriorate, and lithium may be deposited on the electrode surface. On the other hand, if the value of the BET specific surface area exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte solution increases, the gas generated increases, and a preferable battery may not be obtained.

The BET specific surface area is defined as a value as follows: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then, using nitrogen gas relative to atmospheric pressure The relative pressure value is accurately adjusted to 0.3 of the nitrogen-helium mixed gas, the value measured by the nitrogen adsorption BET1 point method using the gas flow method.

[[Volume average particle size]]

The volume average particle size of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] in the lithium secondary battery of the present invention is defined as the average particle size (median particle size) of the volume basis obtained by the laser diffraction/scattering method ), usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. In addition, when the above range is exceeded, an uneven coating surface is likely to be formed when forming an electrode plate, which may be unfavorable in the battery production process.

[[pore volume]]

The micropore volume of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] in the lithium secondary battery of the present invention is obtained by a mercury porosimeter (mercury porosimetry) and is equivalent to a diameter of 0.01 μm to 1 μm. The amount of voids in the particles and the unevenness of the particle surface is 0.01 mL/g or more, preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, and the upper limit is usually 0.6 mL/g or less, The range is preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder will be required to manufacture an electrode plate. On the other hand, if it is less than this range, the short-time high current density charge-discharge characteristics will deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If this range is exceeded, a large amount of adhesive is sometimes required. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the short-time high current density charge and discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of the sample (negative electrode material) was weighed, sealed in a powder container, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, depressurize to 4psia (about 28kPa), introduce mercury, increase the pressure from 4psia (about 28kPa) to 40000psia (about 280MPa) stepwise, and then lower the pressure to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

[[ash]]

The ash contained in the carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less with respect to the total mass of the carbonaceous material. In addition, as the lower limit, it is preferably by mass. Above 1ppm. If the above range is exceeded, the deterioration of battery performance due to the reaction with the non-aqueous electrolytic solution at the time of charging and discharging cannot be ignored. On the other hand, if it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

[[Circularity]]

The circularity of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] in the lithium secondary battery of the present invention is usually 0.1 or more, preferably 0.8 or more, more preferably 0.85 or more, and even more preferably 0.9 or more. As an upper limit, a theoretical true sphere is achieved when the circularity is 1. If it is less than this range, the filling property of the negative electrode active material will decrease, the impedance between the particles will increase, and the short-time high current density charge and discharge characteristics may decrease.

The circularity in the present invention is defined by the following formula.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the following value is used: Using, for example, a flow type particle image analysis device (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) sorbitol as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50mL) of sugar-alcohol monolaurate with an output of 60W for 1 minute at 28kHz ultrasonic waves, specify a detection range of 0.6-400μm, and measure particles with a particle diameter of 3-40μm , and use its measured mean.

[[Orientation Ratio]]

The orientation ratio of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] in the lithium secondary battery of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and its upper limit is theoretically 0.67 or less . If it is less than this range, short-time high-density charge and discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. From the obtained integrated intensity, a ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated, and this ratio was defined as the active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

·Slit:

Divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

[[Aspect Ratio]]

The aspect ratio of the amorphous carbonaceous used as the negative electrode active material of the negative electrode [2] in the lithium secondary battery of the present invention is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coated surface may not be obtained, and the short-time high current density charge-discharge characteristics may deteriorate.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of the carbonaceous material particle and the shortest diameter B perpendicular thereto when viewed three-dimensionally. Observation of carbon particles was performed with a scanning electron microscope capable of magnified observation. Randomly select 50 particles fixed on the end face of a metal plate with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

In addition, the amorphous carbonaceous substance contained in the lithium secondary battery of the present invention used as the negative electrode active material of the negative electrode [2] is preferably selected from the following amorphous carbonaceous substances (1) to (4).

(1) Substances obtained by heat-treating carbides selected from coal coke, petroleum coke, furnace black, acetylene black and pitch-based carbon fibers;

(2) organic matter selected from asphalt raw materials, aromatic hydrocarbons, N ring compounds, S ring compounds, polyphenylene, organic synthetic polymers, natural polymers, thermoplastic resins and thermosetting resins and/or thermal decomposition products thereof and/ or substances obtained by further heat treatment;

(3) dissolving the organic matter of (2) in a low molecular organic solvent to obtain a thermal decomposition product of the solution and/or further heat-treating to obtain a substance;

(4) Carbide of gas containing organic matter.

For (2), as long as it is a substance that can be carbonized, aromatic hydrocarbons such as pitch raw materials, acenaphthylene, decacyclene, anthracene, and phenanthrene; N-ring compounds such as phenazine or acridine; thiophene, bicycline, etc. S-ring compounds such as dithiophene; polyphenylenes such as biphenyl and terphenyl; polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, their cross-linked products, insoluble processed products, nitrogen-containing polyacrylonitrile, Polypyrrole and other organic polymers; sulfur-containing polythiophene, polystyrene and other organic polymers; polysaccharides represented by cellulose, lignin, mannan, polygalacturonic acid, chitosan, sucrose, etc. Natural polymers; thermoplastic resins such as polyphenylene sulfide and polyphenylene ether; thermosetting resins such as furfuryl alcohol resins, phenolic resins, and imide resins; Organic substances such as solutions formed in organic solvents; carbonizable gases containing these organic substances, etc.

Among these, the pitch raw material is preferable because it can produce a high-yield material due to its high carbon residue ratio (carbon residue ratio). In addition, in this specification, a "pitch raw material" refers to pitch and a substance belonging to pitch, and refers to a substance that can be carbonized or graphitized by appropriate treatment. As an example of a specific pitch raw material, tar, heavy oil, pitch, etc. can be used. Specific examples of tar include coal tar, petroleum tar, and the like. Specific examples of the heavy oil include catalysis oil, pyrolysis oil, atmospheric residual oil, vacuum residual oil, and the like of petroleum heavy oil. In addition, specific examples of pitch include coal tar pitch, petroleum pitch, synthetic pitch, and the like. Among them, coal tar pitch is preferable because of its high aromaticity. Any one of these pitch raw materials may be used alone, or two or more of them may be used in combination in any desired ratio.

As a preferred example of (3), it is possible to enumerate a solution obtained by dissolving the above-mentioned organic substance in (2) in low-molecular organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and then obtain a solution by thermally decomposing the solution as Precursor carbides.

Regarding (4), hydrocarbon compounds such as methane, ethane, propane, benzene, acetylene, and ethylene; carbon monoxide, and the like are exemplified.

Preferably, a crosslinking treatment is performed. The so-called cross-linking treatment is performed to make the carbonaceous material obtained by heat-treating the cross-linked pitch raw material etc. difficult to graphitize, and the charge capacity per unit mass can be increased by carrying out these treatments.

As an example of crosslinking treatment, the following treatment methods can be cited: in divinylbenzene, trivinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, N,N-methylene α,α'-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), lauroyl peroxide, isohydroperoxide are used as radical polymerization initiators in vinyl monomers such as bisacrylamide Cross-linking treatment such as propylbenzene, tert-butyl hydroperoxide, hydrogen peroxide, etc.; oxidizing agent treatment using oxidizing gases such as oxygen, ozone, nitrogen dioxide, or oxidizing liquids such as sulfuric acid, nitric acid, and aqueous hydrogen peroxide . An example of a method of crosslinking treatment includes a method of treating the asphalt raw material after mixing with a crosslinking agent or an oxidizing agent while controlling the temperature of the pitch raw material at 50°C to 400°C.

[[Li-NMR shift]]

When the amorphous carbonaceous material used in the negative electrode active material of the so-called negative electrode [2] in the lithium secondary battery of the present invention is subjected to ⁷ Li-NMR analysis when it is charged to a fully charged state, a resonance line toward the reference material LiCl is observed. The main resonance peak shifted by 80 to 200ppm on the low magnetic field side of , so in order to increase the capacity per unit mass of the amorphous carbonaceous substance, it is preferable to use a cross-linked amorphous carbonaceous substance.

[[How to make amorphous carbon]]

The method for producing the above-mentioned amorphous carbonaceous material is not particularly limited as long as it does not exceed the scope of the present invention, and various methods can be mentioned. In the production of amorphous carbon, one heat treatment step is necessary, but the heat treatment may be divided into two or more times, and it is also preferable to perform various treatments before and after the heat treatment and/or in the middle of the heat treatment. The various treatments include pulverization, classification, and the above-mentioned crosslinking treatment, etc., and the pulverization and classification treatment may be performed at any one of the before, after, and intermediate stages of the heat treatment as long as it is in a solid state. The crosslinking treatment is preferably performed before or during the heat treatment. By performing these treatments, the specific surface area of the negative electrode active material can be controlled, and the capacity per unit mass can be increased.

The device used in the pulverization before the heat treatment is not particularly limited, for example, as a coarse pulverizer, a shear mill, a jaw crusher, an impact crusher, a cone crusher, etc. can be mentioned, and as an intermediate pulverizer , include a roll crusher, a hammer mill, and the like, and examples of the fine pulverizer include a ball mill, a vibration mill, a pin mill, an agitator mill, and a jet mill.

The apparatus used in the heat treatment of the raw material is not particularly limited, for example, a shuttle furnace (Shyatoll furnace), a tunnel furnace (Tonell furnace), an electric furnace, a coke roasting furnace (Ride Hanma furnace), a rotary kiln, Reactors such as autoclaves, cokes (heat treatment tanks manufactured by cokes), direct electric furnaces, etc. When processing raw materials, stirring can be performed as needed.

The temperature conditions for heat treatment are not particularly limited, but are usually 600°C or higher, preferably 900°C or higher, and the upper limit is usually 2500°C or lower, preferably 1300°C or lower. When the temperature condition is lower than the above range, the crystallinity becomes too low, which may increase the irreversible capacity. On the other hand, when the upper limit is exceeded, the crystallinity becomes too high, and there is a possibility that the short-time high current density charge and discharge characteristics may be degraded.

The heat-treated amorphous carbon can be pulverized or classified according to the size of its lumps or particles. The device used for pulverization is not particularly limited. For example, as a coarse pulverizer, shear mills, jaw crushers, impact crushers, cone crushers, etc. can be mentioned, and as intermediate pulverizers, there can be mentioned Roller crushers, hammer mills, etc., and examples of fine pulverizers include ball mills, vibration mills, pin mills, stirring mills, and jet mills. The device used in the classification process is not particularly limited. For example, in the case of dry sieving, a rotary sieve, a shaking sieve, a rotary sieve (rotary sieve), a vibrating sieve, etc. can be used. In the case of airflow classification, gravity classifiers, inertial force classifiers, centrifugal force classifiers (classifiers, cyclone separators), etc. can be used. In addition, mechanical wet classifiers and hydraulic classifiers can be used for wet sieving. , sedimentation classifier, centrifugal wet classifier, etc.

[Making the electrode of the negative electrode [2]]

The negative electrode [2] can be produced by a common method, and the negative electrode [2] can be formed in the same manner as above. The current collector, the thickness ratio between the current collector and the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

<Negative pole [3]>

Next, the negative electrode [3] used in the lithium secondary battery of the present invention will be described. The negative electrode contains, as a negative electrode active material, a metal oxide containing titanium capable of occluding and releasing lithium.

[Negative electrode active material of the negative electrode [3]]

Next, the negative electrode active material used in the negative electrode [3] will be described.

[[Composition of negative electrode active material]]

The negative electrode active material used in the negative electrode [3] of the lithium secondary battery of the present invention contains a metal oxide containing titanium capable of occluding and releasing lithium. Among the metal oxides, a composite oxide of lithium and titanium (hereinafter, simply referred to as "lithium-titanium composite oxide") is preferable, and the metal oxide is preferably a titanium-containing metal oxide having a spinel structure. In addition, when a metal oxide satisfying these conditions is used in the negative electrode active material for a lithium secondary battery, that is, when a lithium-titanium composite oxide having a spinel structure is used, the output impedance can be greatly reduced, so it is particularly preferable.

In addition, it is preferable that lithium or titanium in the lithium-titanium composite oxide is replaced by other metal elements, such as at least one element selected from Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. replacement.

The metal oxide is a lithium-titanium composite oxide represented by the general formula (1), and from the viewpoint of structural stability during doping/dedoping of lithium ions, it is preferable that in the general formula (1), 0.7≤x≤1.5, 1.5≤y≤2.3, 0≤z≤1.6.

Li _x Ti _y M _z O ₄ (1)

[In general formula (1), M represents at least one element selected from Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb].

Among the compositions represented by the above-mentioned general formula (1), the structures shown below are particularly preferable because the balance of battery performance is good.

In the general formula (1) Li _x Ti _y M _z O ₄ ,

(a) 1.2≤x≤1.4, 1.5≤y≤1.7, z=0

(b) 0.9≤x≤1.1, 1.9≤y≤2.1, z=0

(c) 0.7≤x≤0.9, 2.1≤y≤2.3, z=0

A particularly preferred representative composition of the above compound is: (a) Li _4/3 Ti _5/3 O ₄ , (b) Li ₁ Ti ₂ O ₄ , (c) Li _4/5 Ti _11/5 O ₄ .

In addition, regarding the structure of Z≠0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ can be cited as a preferable composition.

[[Physical properties, shape, etc. of the negative electrode active material]]

The negative electrode active material used in the negative electrode [3] of the lithium secondary battery of the present invention preferably satisfies at least one of the following physical properties in addition to the above requirements. In addition, it is particularly preferable to simultaneously satisfy at least two or more of the following physical properties in addition to the above requirements.

[[[BET specific surface area]]]

The specific surface area of the titanium-containing metal oxide used for the negative electrode active material of the negative electrode [3] in the lithium secondary battery of the present invention as measured by the BET method is preferably 0.5 m ² /g or more, more preferably 0.7 m ² /g or more , particularly preferably at least 1.0 m ² /g, more preferably at least 1.5 m ² /g. The upper limit thereof is preferably 200 m ² /g or less, more preferably 100 m ² /g or less, particularly preferably 50 m ² /g or less, further preferably 25 m ² /g or less. If the value of the BET specific surface area is below this range, when used as a negative electrode material, the reaction area in contact with the non-aqueous electrolytic solution decreases, and the output impedance may increase. On the other hand, if the value of the BET specific surface area exceeds this range, the crystal surface or end face portion of the metal oxide containing titanium will increase, and thus crystal unevenness (distortion) will occur, and the irreversible capacity will become unnegligible, sometimes No preferred battery was obtained.

The BET specific surface area is defined as a value as follows: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then, using nitrogen gas relative to atmospheric pressure The relative pressure value is accurately adjusted to 0.3 of the nitrogen-helium mixed gas, the value measured by the nitrogen adsorption BET1 point method using the gas flow method.

[[[Volume Average Particle Size]]]

In the lithium secondary battery of the present invention, the volume average particle diameter of the metal oxide containing titanium used as the negative electrode active material of the negative electrode [3] (when the primary particles are aggregated to form secondary particles, it is the secondary particle diameter) is defined by The volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method is preferably 0.1 μm or more, more preferably 0.5 μm or more, and still more preferably 0.7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If it is less than the above-mentioned range, a large amount of binder is required when producing an electrode, and as a result, the battery capacity may decrease. In addition, when the above range is exceeded, an uneven coating surface is likely to be formed when forming an electrode plate, which may be unfavorable in the battery production process.

[[[Average primary particle size]]]

When the primary particles are aggregated to form secondary particles, the average primary particle size of the titanium-containing metal oxide used as the negative electrode active material of the lithium secondary battery of the present invention is preferably 0.01 μm or more, more preferably 0.05 μm or more, and further preferably 0.05 μm or more. It is preferably 0.1 μm or more, most preferably 0.2 μm or more, and the upper limit thereof is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, and most preferably 1 μm or less. When the average primary particle size exceeds the above upper limit, it is difficult to form spherical secondary particles, which adversely affects the powder fillability, or the specific surface area is greatly reduced, and therefore battery performance such as output characteristics may decrease. On the contrary, if the average primary particle diameter is less than the above-mentioned lower limit, problems such as poor charge-discharge reversibility may occur due to incomplete crystallization.

The primary particle size can be measured by observation using a scanning electron microscope (SEM). Specifically, it is obtained by the following method: in a photograph with a magnification of 10,000 to 100,000 times, for any 50 primary particles, the longest value of the slice generated by the left and right boundary lines of the primary particles on a straight line in the horizontal direction is obtained, and Take its average.

[[[shape]]]

The particle shape of the titanium-containing metal oxide used in the negative electrode [3] of the lithium secondary battery of the present invention can be a block shape, a polyhedron shape, a spherical shape, an ellipsoidal shape, a plate shape, a needle shape, a columnar shape, etc., which have been used in the past, Among them, it is preferable that the primary particles are aggregated to form secondary particles, and the shape of the secondary particles is spherical or ellipsoidal. In general, the active material in the electrode expands and shrinks as the electrochemical element is charged and discharged, and thus degradation of the active material due to this stress, such as destruction of the active material or interruption of the conductive path, tends to occur. Therefore, it is preferable to agglomerate primary particles to form secondary particles rather than single-particle active material with only primary particles, because the formation of secondary particles can relieve the stress of expansion and contraction, thereby preventing deterioration. In addition, spherical or ellipsoidal particles are preferred over plate-like equiaxially oriented particles, because spherical or ellipsoidal particles have less orientation during electrode molding and less expansion and contraction of the electrode during charging and discharging, and in It is also easy to mix uniformly with the conductive agent when making electrodes.

[[[Tap Density]]]

The tap density of the titanium-containing metal oxide used as the negative electrode active material of the negative electrode [3] in the lithium secondary battery of the present invention is preferably 0.05 g/cm ³ or more, more preferably 0.1 g/cm ³ or more, and furthermore Preferably it is 0.2 g/cm ³ or more, particularly preferably 0.4 g/cm ³ or more. In addition, the upper limit thereof is preferably 2.8 g/cm ³ or less, more preferably 2.4 g/cm ³ or less, particularly preferably 2 g/cm ³ or less. If the tap density is lower than this range, it will be difficult to increase the packing density when used as a negative electrode, and the contact area between particles will decrease, so the impedance between particles will increase, and the output resistance may increase. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, and the flow path of the non-aqueous electrolyte solution will be reduced, which may increase the output resistance.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm, the sample is dropped into a ²⁰ cm container for vibration, and after the sample is filled with the upper end of the container, a powder density measuring device (such as , Tap densor manufactured by Seishin Enterprise Co., Ltd.), vibration with a stroke length of 10 mm was performed 1000 times, and the density obtained from the volume at that time and the weight of the sample was taken as the tap density.

[[[Circularity]]]

The circularity of the titanium-containing metal oxide used as the negative electrode active material of the negative electrode [3] in the lithium secondary battery of the present invention is usually 0.10 or more, preferably 0.80 or more, more preferably 0.85 or more, and still more preferably 0.90 or more . As an upper limit, when the circularity is 1, it becomes a theoretical true sphere. If it is less than this range, the filling property of the negative electrode active material will decrease, the impedance between the particles will increase, and the short-time high current density charge and discharge characteristics may decrease.

The circularity in the present invention is defined by the following formula.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the following value is used: Using, for example, a flow type particle image analysis device (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) sorbitol as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50mL) of sugar-alcohol monolaurate with an output of 60W for 1 minute at 28kHz ultrasonic waves, specify a detection range of 0.6-400μm, and measure particles with a particle diameter of 3-40μm And get the value.

[[[Aspect Ratio]]]

In the lithium secondary battery of the present invention, the aspect ratio of the titanium-containing metal oxide used as the negative electrode active material of the negative electrode [3] is theoretically 1 or more, the upper limit is 5 or less, preferably 4 or less, more preferably 3 or less , and more preferably 2 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coated surface may not be obtained, and the short-time high current density charge-discharge characteristics may deteriorate.

In addition, when A is the longest diameter of the particles in three-dimensional observation, and B is the shortest diameter perpendicular thereto, the aspect ratio is represented by A/B. Observation of particles is performed with a scanning electron microscope capable of magnified observation. Randomly select 50 graphite particles fixed on the end face of a metal plate with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and obtain the average value of A/B.

[[Manufacturing method of negative electrode active material]]

The method for producing the negative electrode active material of the negative electrode [3] in the lithium secondary battery of the present invention is not particularly limited within the scope not exceeding the gist of the present invention, and several methods can be cited, and the method for producing an inorganic compound can be used. the usual way. For example, a method of uniformly mixing a titanium raw material such as titanium oxide, raw materials of other elements used as needed, and a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and sintering at a high temperature to obtain an active material is mentioned. In particular, when producing a spherical or ellipsoidal active material, various methods are conceivable, for example, the method of dissolving or pulverizing a titanium raw material such as titanium oxide and, if necessary, raw materials of other elements in a solvent such as water In the process, adjusting the pH while stirring, making and obtaining spherical precursors, drying them as needed, adding Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and sintering at high temperatures to obtain active materials; Titanium raw materials such as titanium and raw materials of other elements used as needed are dissolved or pulverized in solvents such as water, and then dried and shaped by spray dryers to form spherical or ellipsoidal precursors, and then added Li sources such as LiOH, Li ₂ CO _{3 ,} LiNO ₃ , and a method for _obtaining an active material by sintering at a high temperature _; The raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water, and then dried and shaped by a spray dryer to form a spherical or ellipsoidal precursor, and then sintered at a high temperature to obtain an active material, etc. .

In addition, during these steps, elements other than Ti, such as Al, Mn, Ti, V, Cr, Mn, may also be present in the structure of the titanium-containing metal oxide and/or in contact with the titanium-containing oxide. , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn, Ag. By containing these elements, the operating voltage and capacity of the battery can be controlled.

[Making the electrode of the negative electrode [3]]

The negative electrode [3] can be produced by a common method, and the negative electrode [3] can be formed in the same manner as above. The current collector, the thickness ratio between the current collector and the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

<Negative pole [4]>

Next, the negative electrode [4] used in the lithium secondary battery of the present invention will be described. The negative electrode contains a carbonaceous substance as the negative electrode active material, the circularity of the carbonaceous substance is 0.85 or more, the surface functional group content O/C value 0 to 0.01.

[Negative electrode active material of negative electrode [4]]

Next, the negative electrode active material used in the negative electrode [4] will be described.

The negative electrode active material used in the negative electrode [4] of the lithium secondary battery of the present invention contains at least a carbonaceous material satisfying the following conditions (a) and (b).

(a) The circularity is above 0.85;

(b) O/C value of surface functional group amount is 0-0.01.

Next, details of the carbonaceous substance used in the present invention will be described.

[[Circularity]]

The circularity of the carbonaceous material is usually not less than 0.85, preferably not less than 0.87, more preferably not less than 0.89, particularly preferably not less than 0.92. As an upper limit, when the circularity is 1, it becomes a theoretical true sphere. If it is lower than this range, the filling property of the negative electrode active material will decrease, the compaction of the negative electrode electrode will become difficult, and the particles will be destroyed during compaction, and the surface of the particle interior that is poor in high temperature storage resistance at a low charge depth may be easily exposed.

The circularity referred to in the present invention is defined by the following formula.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the following value is used: Using, for example, a flow type particle image analysis device (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) sorbitol as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50mL) of sugar-alcohol monolaurate with an output of 60W for 1 minute at 28kHz ultrasonic waves, specify a detection range of 0.6-400μm, and measure particles with a particle diameter of 3-40μm And get the value.

[[O/C value]]

The O/C value of the amount of surface functional groups of the carbonaceous substance must be 0-0.01. The upper limit of the O/C value is preferably 0.005 or less, and the closer to 0, the more preferable.

The O/C value mentioned in the present invention is the ratio of the amount of surface functional groups measured by X-ray photoelectric spectroscopy (XPS). If the O/C value of the amount of surface functional groups exceeds the above range, the amount of functional groups on the particle surface will increase. When charging is performed under the condition of a specific compound, the stability of the SEI coating film formed on the surface is insufficient, which may lead to a decrease in high-temperature storage characteristics at a low charge depth.

The surface functional group amount O/C value represents the ratio of the molar concentration of oxygen atoms present on the surface of graphite materials and the like to the molar concentration of carbon atoms, and is an index representing the amount of functional groups such as carboxyl groups, phenolic hydroxyl groups, and carbonyl groups present on the surface. In many carbon materials having a large O/C value of surface functional groups, surface oxygen-containing functional groups are bonded to the crystallite end faces of the particle surface carbon. In addition, as the O/C value of the surface functional group amount of the graphite material, the following value is used: In the X-ray photoelectric spectrometry analysis, the peak area of the spectrum of C1s and O1s is obtained, and the atomic concentration ratio of C and O is calculated from this. (O atomic concentration/C atomic concentration). Specific measurement procedures are not particularly limited, and examples thereof are as follows.

That is, using an X-ray photoelectric spectrometer (for example, ESCA manufactured by ulvac-phi (アルバツク·フアイ) company) as the X-ray photoelectric spectrometry measurement, the measurement object (here, graphite material) is placed on the sample stand and the surface It is flat, and the spectra of C1s (280-300eV) and O1s (525-545eV) are measured by multiplex measurement with aluminum Kα rays as the X-ray source. Set the obtained peak top of C1s to 284.3eV for charging compensation, calculate the peak areas of C1s and O1s spectra, and multiply by the device sensitivity coefficient to calculate the surface atomic concentrations of C and O, respectively. The calculated atomic concentration ratio O/C of O and C (O atomic concentration/C atomic concentration) is defined as the surface functional group amount O/C value of the graphite material.

The carbonaceous substance used in the present invention satisfies the above-mentioned conditions of "circularity" and "surface functional group amount O/C value", but from the viewpoint of battery balance, it is more preferable to further satisfy any of the following items at the same time One or more conditions. Among these, it is preferable to simultaneously satisfy the conditions of any one or more of tap density, Raman R value, and volume average particle diameter.

[[Tap Density]]

The tap density of the carbonaceous material is usually 0.55 g/cm ³ or more, preferably 0.7 g/cm ³ or more, more preferably 0.8 g/cm ³ or more, particularly preferably 0.9 g/cm ³ or more. In addition, the upper limit thereof is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. When the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm, the sample is dropped into a ²⁰ cm container for vibration, and after the sample is filled with the upper end of the container, a powder density measuring device (such as , Tap densor manufactured by Seishin Enterprise Co., Ltd.) was vibrated 1000 times with a stroke length of 10 mm, and the density was calculated from the volume and weight at this time, and this value was taken as the tap density.

[[Raman R value, half value width]]

The R value of the carbonaceous material measured by argon ion laser Raman spectroscopy is usually 0.001 or more, preferably 0.01 or more, and its upper limit is usually 0.2 or less, preferably 0.18 or less, more preferably 0.15 or less. If the R value is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, the charge acceptance is lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and when charging is performed in the presence of a specific compound, the stability of the SEI coating film formed on the surface is insufficient, which may lead to high-temperature storage characteristics at a low charge depth. decrease.

In addition, the Raman half-value width of the carbonaceous material around 1580 cm ^-1 is not particularly limited, but it is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and the upper limit is usually 35 cm ^-1 or less, preferably 30 cm ^{-1 or} less. scope. If the Raman half-value width is below this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and when charging is performed in the presence of a specific compound, the stability of the SEI coating film formed on the surface is insufficient, which may lead to high-temperature storage at a low charging depth. reduction in characteristics.

The measurement of the Raman spectrum is carried out as follows: using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped into the measurement container, and the sample is filled. The surface of the sample is irradiated with an argon ion laser while rotating the container in a plane perpendicular to the laser. For the obtained Raman spectrum, the intensity I _A of the peak PA near 1580 cm ^-1 and the intensity I _B of the peak P _B near 1360 cm ^-1 were measured _, and the intensity ratio R (R= _IB / _IA ) was calculated. It is defined as the Raman R value of the carbonaceous material. In addition, the half-value width of the peak ^PA in the vicinity of 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the carbonaceous substance.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

R value, half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

[[Volume-Based Average Particle Size]]

The volume-based average particle size of the carbonaceous material is the volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, which may lead to loss of initial battery capacity. In addition, when the above range is exceeded, an uneven coating surface is likely to be formed when forming an electrode plate, which may be unfavorable in the battery production process.

In addition, the ratio (d ₉₀ /d ₁₀ ) of the 90% particle size to the 10% particle size of the distribution is 1.2 or more, preferably 1.5 or more, and more preferably 1.7 or more in terms of volume-based particle size. The upper limit is 8 or less, preferably 5 or less, more preferably 4 or less, and still more preferably 3 or less.

In the present invention, the volume-based average particle diameter is defined by a median particle diameter measured by dispersing carbon powder in polyoxyethylene (20) sorbitan as a surfactant. In a 0.2% by mass aqueous solution (about 1 mL) of monolaurate, it measures using a laser diffraction/scattering particle size distribution meter (for example, LA-700 manufactured by Horiba, Ltd.). As the ratio (d ₉₀ /d ₁₀ ) of the 90% particle diameter to the 10% particle diameter, the volume-based 90% particle diameter and the 10% particle diameter can be measured in the same manner, and the ratio (d ₉₀ /d ₁₀ ) can be used.

[[X-Ray Parameters]]

The carbonaceous material preferably has a d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction using the Gakushin method of 0.335 nm or more. In addition, the upper limit is 0.340 nm or less, preferably 0.337 nm or less. If the d value is too large, the crystallinity may decrease, which may increase the initial irreversible capacity. On the other hand, 0.335 is the theoretical value of graphite. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 80 nm or more. If it is less than this range, the crystallinity of the particles may decrease, which may increase the initial irreversible capacity.

[[ash]]

The ash contained in the carbonaceous material is 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, with a lower limit of 1 ppm or more based on the total mass of the carbonaceous material. If the above-mentioned range is exceeded, the degradation of battery performance due to the reaction with the electrolytic solution during charging and discharging cannot be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

[[BET specific surface area]]

The specific surface area of the carbonaceous material measured by the BET method is usually at least 0.1 m ² /g, preferably at least 0.7 m ² /g, more preferably at least 1 m ² /g, and still more preferably at least 1.5 m ² /g. The upper limit thereof is usually 100 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. If the value of the specific surface area is less than the above range, when used as a negative electrode material, the acceptance of lithium at the time of charging will be deteriorated, and lithium will be easily deposited on the electrode surface. On the other hand, when it exceeds the above-mentioned range, when used as a negative electrode material, the reactivity with the electrolytic solution increases and gas generation increases, making it difficult to obtain a preferable battery in some cases.

The BET specific surface area is defined as a value measured as follows: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then, using nitrogen gas relative to The relative pressure value of the atmospheric pressure is accurately adjusted to 0.3 nitrogen-helium mixed gas, and it is measured by the nitrogen adsorption BET 1-point method using the gas flow method.

[[Pore Distribution]]

The amount of voids in the carbonaceous material corresponding to particles with a diameter of 0.01 μm to 1 μm and the amount of unevenness caused by the surface of the particles measured by mercury porosimetry (mercury porosimetry) is usually 0.01 mL/g or more, It is preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, and the upper limit is usually 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder may be required when manufacturing an electrode plate. On the other hand, if it is less than this range, the high current density charge-discharge characteristics deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of the sample (negative electrode material) was weighed, sealed in a powder container, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, the pressure is reduced to 4psia (about 28kPa), mercury is introduced, the pressure is raised from 4psia (about 28kPa) to 40000psia (about 280MPa) in steps, and then the pressure is lowered to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

[[true density]]

The true density of the carbonaceous material is usually above 2 g/cm ³ , preferably above 2.1 g/cm ³ , more preferably above 2.2 g/cm ³ , and even more preferably above 2.22 g/cm ³ , with an upper limit of 2.26 g/cm 3 ³ or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase. In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

[[Orientation Ratio]]

The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

· Slit: divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

[[Aspect Ratio]]

The aspect ratio of the carbonaceous material is theoretically 1 or more, and the upper limit is 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of a particle and the shortest diameter B perpendicular thereto in three-dimensional observation. Observation of particles is performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of the metal with a thickness of 50 microns or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

[[Manufacturing method and raw material of carbonaceous material]]

The carbonaceous substance used in the present invention may be either naturally occurring or artificial, but is preferably derived from natural graphite. In addition, naturally occurring substances or artificially produced substances may also be subject to specific treatments. The production method (including the sorting method) is not particularly limited, and for example, a carbonaceous material having the above-mentioned characteristics may be sorted using a classification method such as sieving or wind classification.

Among these, carbonaceous substances obtained by heat-treating naturally occurring carbon materials (natural graphite raw materials) are preferable from the viewpoint of easy availability and easy processing in the preceding steps. In addition, from the viewpoint of improving filling properties, etc., carbonaceous substances obtained by applying mechanical energy treatment to naturally occurring carbon materials (natural graphite raw materials) or artificially produced carbon materials to modify and spheroidize, and then The obtained spheroidized carbonaceous is subjected to heat treatment. In addition, from the viewpoint of the balance of the performance of the lithium secondary battery, etc., carbonaceous materials prepared by subjecting natural graphite raw materials to mechanical energy treatment and heat-treating the obtained spheroidized natural graphite are particularly preferable. Hereinafter, the carbon material (raw material) before heat treatment, such as the above-mentioned natural graphite raw material, may be simply referred to as "raw material before heat treatment".

[[Natural graphite raw material]]

As described above, natural graphite is particularly preferable as the raw material of the carbonaceous substance.

Natural graphite is classified into flake graphite (Flake Graphite), scaly graphite (Crystalline (Vein) Graphite), and soil graphite (Amorphous Graphite) according to its properties (see "Powder Granular Process Technology Integration", Industrial Technology Co., Ltd. Center, Graphite item issued in Showa 49; and "HANDBOOK OF CARBON, GRAPHITE, DIAMOND AND FULLERENES", issued by NoyesPublications). The degree of graphitization is highest in flake graphite, which is 100%, followed by flake graphite, which is 99.9%, while soil graphite is as low as 28%. The quality of natural graphite is mainly determined by the place of origin and the vein. Flake graphite is mainly produced in Madagascar, China, Brazil, Ukraine, Canada, etc.; flake graphite is mainly produced in Sri Lanka, and soil graphite is mainly produced in the Korean Peninsula, China, Mexico, etc. Among these natural graphites, flaky graphite and flaky graphite are preferable as raw materials for carbonaceous substances because they have advantages such as a high degree of graphitization and a small amount of impurities.

[[[Mechanical energy processing, spherical processing]]]

The mechanical energy treatment is performed so that the volume average particle diameter before and after the treatment becomes 1 or less. The "volume average particle diameter ratio before and after treatment" is a value obtained by dividing the volume average particle diameter after treatment by the volume average particle diameter before treatment. In the present invention, it is preferable that the kinetic energy treatment performed to produce the raw material before the heat treatment is such that the average particle diameter ratio before and after the treatment is 1 or less.

The mechanical energy treatment is a treatment performed to reduce the particle size so that the average particle diameter ratio before and after the powder particle treatment is 1 or less, and at the same time control the particle shape. Among engineering unit operations that can be effectively utilized in particle design, such as pulverization, classification, mixing, granulation, surface modification, and reaction, mechanical energy processing belongs to pulverization processing.

The so-called pulverization refers to applying force to a substance to reduce its size to adjust the particle size, particle size distribution, and filling properties of the substance. Pulverization treatment is classified according to the type of force applied to the substance and the form of treatment. The force exerted on the substance is roughly divided into the following four types: (1) knocking force (impact force), (2) crushing force (compression force), (3) grinding force (grinding force), (4) scraping force force (shear force). On the other hand, processing forms are roughly classified into two types: volume crushing in which cracks are generated inside the particles and propagated, and surface crushing in which the particle surfaces are cut off. Volume crushing can be carried out by impact force, compression force and shear force; surface crushing can be carried out by grinding force and shear force. Pulverization is a process of various combinations of the type of force applied to these substances and the form of treatment. The combination thereof can be appropriately determined according to the purpose of treatment.

Pulverization may be performed using a chemical reaction such as blasting or volume expansion, but it is usually performed using a mechanical device such as a pulverizer. The pulverization treatment used in the production of the spheroidized carbonaceous material that is the raw material of the present invention is preferably a treatment that increases the ratio of the final surface treatment regardless of the presence or absence of volume pulverization. This is because it is important to remove the pulverized corners of the particle surface to introduce a round shape to the particle shape. Specifically, the surface treatment may be performed after a certain volume pulverization is performed, only the surface treatment may be performed without volume pulverization, or the volume pulverization and surface treatment may be performed simultaneously. It is preferable to perform surface crushing at the end to remove corners from the surface of the particles.

The device for mechanical energy processing is selected from devices capable of performing the above-mentioned preferable processing. The mechanical energy treatment can be realized by using more than one of the four kinds of forces applied to the above-mentioned substances, but it is preferable to repeatedly perform mechanical actions such as compression, friction, and shearing forces that include the interaction of particles on the body, so that the particles Gives impact. Therefore, specifically, a device that has a rotor provided with a plurality of blades inside the tank and that imparts mechanical forces such as impact compression, friction, and shearing force to the carbon material introduced into the inside by rotating the rotor at high speed is preferable. function, thereby carrying out surface treatment while performing volume crushing. In addition, a device having a mechanism for repeatedly imparting a mechanical action by circulating or convecting the carbonaceous material is more preferable.

As a preferable device, a mixing system (manufactured by Nara Machinery Manufacturing Co., Ltd.), Kryptron (cryptron) (manufactured by Earth Technica (Asteknica) Co., Ltd.), CF mill (manufactured by Ube Industrial Co., Ltd.), mechanical melting system (hosokawamicron) can be mentioned. (manufactured by Hosokawa Micron Co., Ltd.), etc. Among these, the mixing system manufactured by Nara Machinery Manufacturing Co., Ltd. is preferable. When using this apparatus for processing, the peripheral speed of the rotating rotor is preferably set at 30 to 100 m/sec, more preferably at 40 to 100 m/sec, and even more preferably at 50 to 100 m/sec. In addition, the treatment may be performed by merely passing the carbonaceous material, but it is preferably treated by circulating or staying in the device for 30 seconds or more, more preferably by circulating or staying in the device for 1 minute or more.

By performing the mechanical energy treatment in this way, the carbon particles become particles in which high crystallinity is maintained as a whole, but the vicinity of the surface of the particles becomes rough, and the edge surfaces are inclined and exposed. In this way, the surface where lithium ions can come and go increases, and it has a high capacity even at a high current density.

In general, the smaller the particle size of the scale-like, scale-like, and plate-like carbon materials tends to be, the worse the fillability is. This is considered to be due to the following reasons: as the particles become more amorphous by pulverization, or protrusions such as "burrs", "peeling" or "bends" generated on the particle surface increase, and some degree of deformation occurs on the particle surface. The strength is caused by the adhesion of finer amorphous particles, etc., so that the resistance between adjacent particles becomes larger, and the filling property is deteriorated.

If the amorphousness of these particles is reduced and the particle shape is close to spherical, even if the particle size becomes smaller, the filling property will be reduced very little. In theory, both large particle size carbon powder and small particle size carbon powder should be Shows an equivalent degree of tap density.

[[[Physical properties of raw materials before heat treatment]]]

The physical properties of the raw material before heat treatment preferably satisfy any one or more of the following (1) to (11) at the same time. In addition, the intangible measurement method and definition are the same as in the case of the above-mentioned carbonaceous substance.

(1) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction using the Gakushin method of the raw material before heat treatment is preferably 0.335 nm or more. In addition, the lower limit thereof is less than 0.340 nm, preferably 0.337 nm or less. If the d value is too large, the crystallinity may decrease, which may increase the initial irreversible capacity. On the other hand, 0.335 is the theoretical value of graphite. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 80 nm or more. If it is less than this range, the crystallinity may decrease, which may increase the initial irreversible capacity.

(2) Ash content

The ash contained in the raw material before heat treatment is usually 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and the lower limit thereof is usually 1 ppm or more based on the total mass of the raw material before heat treatment. If the above-mentioned range is exceeded, the degradation of battery performance due to the reaction with the electrolytic solution during charging and discharging cannot be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Volume-based average particle size

The volume-based average particle diameter of the raw material before heat treatment is the volume-based average particle diameter (median particle diameter) obtained by the laser diffraction/scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and further It is preferably 7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode pad, and it may be unpreferable in a battery manufacturing process.

(4) Raman R value, Raman half value width

The R value of the raw material before heat treatment measured by argon ion laser Raman spectroscopy is usually 0.10 or more, preferably 0.15 or more, more preferably 0.17 or more, still more preferably 0.2 or more, and the upper limit thereof is usually 0.8 or less, preferably 0.6 or less , more preferably in the range of 0.4 or less. If the R value is lower than this range, the particles may not be spheroidized, and the effect of improving filling properties may not be obtained. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, and the reactivity with the electrolyte solution increases, resulting in a decrease in efficiency or an increase in gas generation.

In addition, the Raman half-value width near 1580 cm ^-1 of the raw material before heat treatment is not particularly limited, but it is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and the upper limit is usually 80 cm ^-1 or less, preferably 60 cm ^-1 or less , more preferably 45 cm ^-1 or less, still more preferably 40 cm ^-1 or less. If the Raman half-value width is less than this range, the particles may not be spheroidized, and the effect of improving filling properties may not be obtained. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, and the reactivity with the electrolytic solution will increase, which may result in a decrease in efficiency or an increase in generated gas.

(5) BET specific surface area

The specific surface area of the raw material before heat treatment measured by the BET method is usually 0.1 m ² /g or more, preferably 0.7 m ² /g or more, more preferably 1 m ² /g or more, still more preferably 1.5 m ² /g or more. The upper limit thereof is usually 100 m ² /g or less, preferably 50 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. If the value of the specific surface area is less than the above range, when used as a negative electrode material, the acceptance of lithium at the time of charging will be deteriorated, and lithium will be easily deposited on the electrode surface. On the other hand, if it exceeds the above range, heat treatment will reduce the specific surface area, more than necessary reaction with the electrolytic solution will occur, and more gas will be generated, making it difficult to obtain a preferable battery.

(6) Micropore distribution

The amount of voids in particles with a diameter of 0.01 μm to 1 μm and unevenness on the particle surface of the raw material before heat treatment measured by mercury porosimetry (mercury porosimetry) is usually 0.01 mL/g Above, preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, the upper limit is usually 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder will be required to manufacture an electrode plate. On the other hand, if it is less than this range, the high current density charge-discharge characteristics deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the high current density charge-discharge characteristics may deteriorate.

(7) Circularity

Using circularity as the degree of sphericity of the raw material before heat treatment, the circularity of particles in the range of 3 to 40 μm in particle diameter of the raw material before heat treatment is preferably 0.85 or more, more preferably 0.87 or more, particularly preferably 0.90 or more, and further Preferably it is 0.92 or more. When the circularity is large, the high current density charge and discharge characteristics are improved, which is preferable.

The method of improving the circularity is not particularly limited, but it is preferable to perform the spheroidization treatment by the above-mentioned mechanical energy to form a spherical shape, because in this way, the shapes of the interparticle voids are uniform when the electrode body is produced.

(8) True density

The true density of the raw material before heat treatment is usually 2 g/cm ³ or more, preferably 2.1 g/cm ³ or more, more preferably 2.2 g/cm ³ or more, still more preferably 2.22 g/cm ³ or more, and the upper limit is 2.26 g/cm 3 or more. ^cm3 or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

(9) Tap density

The tap density of the raw material before heat treatment is usually 0.55 g/cm ³ or more, preferably 0.7 g/cm ³ or more, more preferably 0.8 g/cm ³ or more, particularly preferably 0.9 g/cm ³ or more. In addition, the upper limit thereof is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. If the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

(10) Orientation ratio

The orientation ratio of the raw material before heat treatment is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

(11) aspect ratio

The aspect ratio of the raw material before heat treatment is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

[[[Heat treatment temperature]]]

The heat treatment temperature of the raw material before heat treatment is usually 600°C or higher, preferably 1200°C or higher, more preferably 2000°C or higher, still more preferably 2500°C or higher, particularly preferably 2800°C or higher. The upper limit thereof is usually not higher than 3200°C, preferably not higher than 3100°C. If the temperature condition is lower than this range, the crystallization repair of the surface of scattered graphite particles by spheroidization treatment or the like is insufficient, and the Raman R value and the BET specific surface area may not be reduced. On the other hand, when it exceeds the said range, the amount of sublimation of graphite may become large easily.

[[[Heat treatment method]]]

Heat treatment can be achieved by passing through the above-mentioned temperature range once. The holding time for keeping the temperature condition in the above range is not particularly limited, but is usually longer than 10 seconds and is 168 hours or less.

The heat treatment is usually carried out in an inert gas atmosphere such as nitrogen gas or in a non-oxidizing atmosphere obtained from the gas generated from the raw material graphite. However, in the furnace of the type embedded in coke powder (fine pitch-sintered carbon), air is sometimes mixed initially. In such a case, a completely inert gas atmosphere may not be necessary.

The apparatus used for the heat treatment is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, a coke roasting furnace, a rotary furnace, a direct electric furnace, an Acheson electric furnace, a resistance heating furnace, an induction heating furnace, etc. can be used. .

In addition, various processing such as classification processing may be performed in addition to the processing described above. Classification treatment is performed to obtain the target particle size and remove coarse powder and fine powder. As the device used in the classification process, there is no particular limitation. For example, in the case of dry sieving, rotary sieves, shaking sieves, rotary sieves, vibrating sieves, etc. can be used; in the case of dry airflow classification In the case of wet sieving, gravity classifiers, inertial force classifiers, centrifugal force classifiers (classifiers, cyclone separators), etc. can be used; in the case of wet sieving, mechanical wet classifiers, hydraulic classifiers, Sedimentation classifier, centrifugal wet classifier, etc. Grading treatment can be carried out before heat treatment, and can also be carried out at other times, such as after heat treatment. Furthermore, the classification process itself can also be omitted. However, from the viewpoint of productivity of the graphite powder negative electrode material, it is preferable to carry out the classification treatment immediately after the spheroidization treatment and before the heat treatment.

[[Vice material mix]]

In addition to the above-mentioned carbonaceous substances, by containing one or more carbonaceous substances (carbonaceous materials) different from the above-mentioned carbonaceous substances in the physical properties of carbonaceous substances in the negative electrode active material used in the present invention, it is possible to further improve battery performance. improve. The "carbonaceous physical properties" mentioned here refer to X-ray diffraction parameters, median particle size, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, micropore distribution, One or more properties among circularity and gray content. In addition, as a preferred embodiment, the volume-based particle size distribution is asymmetrical around the median particle size, contains two or more carbon materials with different Raman R values, or has different X-ray parameters. As an example of the effect, reduction of electrical resistance by including carbon materials such as graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and amorphous carbon such as needle coke as sub-materials can be cited. These may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary and arbitrary ratios. When added as an auxiliary material, its addition amount is usually 0.1 mass % or more, preferably 0.5 mass % or more, more preferably 0.6 mass % or more, and its upper limit is usually 80 mass % or less, preferably 50 mass % or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less. If it is less than this range, it may be difficult to obtain the effect of improving electrical conductivity. If the above range is exceeded, the initial irreversible capacity may increase.

[Making the electrode of the negative electrode [4]]

A common method can be used to manufacture the negative electrode [4], and the negative electrode [4] can be formed in the same manner as above. The current collector, the thickness ratio between the current collector and the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

<Negative pole [5]>

Next, the negative electrode [5] used in the lithium secondary battery of the present invention will be described. The negative electrode contains, as an active material, a differently oriented carbon composite containing two or more types of carbon materials with different orientations. substance.

[Negative electrode active material of negative electrode [5]]

Next, the negative electrode active material used in the negative electrode [5] will be described.

[[Composition of Hetero-Oriented Carbon Composite]]

The negative electrode active material used in the negative electrode [5] of the lithium secondary battery of the present invention contains a differently oriented carbon composite containing two or more carbonaceous materials having different orientations.

The "different orientation" mentioned here means that when the powder is observed with a polarizing microscope, the pattern of the anisotropic unit of the optical anisotropic structure is visually compared, that is, the size, direction, number, etc. of the anisotropic unit. At least any one of their size, direction, number, etc. is different. For example, among carbonaceous 1 and carbonaceous 2, one has crystal orientation in one direction and the other has random crystal orientation; or carbonaceous 1 and carbonaceous 2 each have crystal directionality, but the direction is different, etc. In addition, when one or both of carbonaceous 1 and carbonaceous 2 is not a single crystal but an aggregate of multiple crystals, the unit of the aggregate is regarded as one region, and the respective optical anisotropy structures are compared. An assemblage pattern of anisotropic units.

In addition, the form in which the carbonaceous 1 and the carbonaceous 2 coexist in the anisotropic carbon composite is preferably included in one secondary particle. The term "included in one secondary particle" here refers to a state in which carbonaceous substances with different orientations are physically restrained and attached; a state in which the shape is maintained by electrostatic restraint and adhesion; Constrained status, etc. The "physical constraint and attachment" mentioned here refers to the state that one carbonaceous substance is mixed in another carbonaceous substance and connected together; The state in which electrostatic energy is attached to another carbonaceous substance. In this constrained and adhered state, the aforementioned orientation may be different, or the original carbonaceous substance may be the same substance. In addition, the "state bound by bonding" refers to chemical bonds such as hydrogen bonds, covalent bonds, and ionic bonds.

Among them, it is preferable that another carbonaceous substance has an interface with a different orientation by adhesion and/or bonding on at least a part of the surface of one carbonaceous substance. Compared with the case of having an interface and not having an interface, when particles of the same shape are compared, the expansion caused by lithium ion inclusions during charging is dispersed in many areas, thereby preventing battery deterioration, which is preferable in this point of view. of.

The portion having a different orientation may be formed by bonding with externally supplied materials and/or their modified products, or may be formed by modifying the material of the surface portion of the carbonaceous substance. Among them, the so-called coverage means having a chemical bond in at least part of the interface with the surface of the carbonaceous substance, thereby showing: (1) a state covering the entire surface, (2) a state of partially covering the carbonaceous substance, (3) selectivity (4) A state where a part of the surface is completely covered, and (4) a state where an extremely small region containing chemical bonds exists.

In addition, in the vicinity of the interface, the orientation of the carbonaceous material may change continuously or discontinuously. That is, it is preferable that the hetero-oriented carbon composite has an interface formed by the attachment and/or bonding of carbonaceous substances with different orientations, and the orientation of the carbonaceous substances at this interface changes discontinuously and/or continuously.

In addition, the components of the hetero-oriented carbonaceous composite (A) are not particularly limited as long as they have crystallinity, but carbonaceous substances with different orientations are preferred from the viewpoint of higher charge capacity per unit mass. One or more of them are graphite-like carbonaceous substances (B) derived from natural graphite (D) (hereinafter, simply referred to as "natural graphite-like carbonaceous substances (B)").

In addition, the ratio of the natural graphite-like carbonaceous material (B) contained in the heterooriented carbon composite to the heterooriented carbon composite is usually 5% by mass or more, preferably 20% by mass or more, more preferably 30% by mass Above, more preferably 40% by mass or more, particularly preferably 50% by mass or more. The upper limit thereof is usually 99.9% by mass or less, preferably 99% by mass or less, more preferably 95% by mass or less, and still more preferably 90% by mass or less. If it is less than this range, the load at the time of rolling of an electrode will increase remarkably, and peeling of an electrode, etc. may be caused. On the other hand, when this range is exceeded, the bonding at the interface of a composite of particles having different orientations may become weak.

In addition, as another constituent component of the differently oriented carbon composite, from the viewpoint of forming an interface during preparation of the differently oriented carbon composite and improving the adhesiveness of the interface, one or more carbonaceous substances having different orientations are preferable. It is a carbonaceous substance (C) selected from the following (1) to (5).

(1) Carbide selected from coal coke, petroleum coke, furnace black, acetylene black and pitch carbon fiber;

(2) Organic substances and/or thermal decomposition products selected from asphalt raw materials, aromatic hydrocarbons, N-ring compounds, S-ring compounds, polyphenylene, organic synthetic polymers, natural polymers, thermoplastic resins and thermosetting resins are used as precursors solid carbides;

(3) dissolving the organic substance of (2) in a low molecular weight organic solvent to obtain a carbide of the thermal decomposition product of the solution as a precursor;

(4) Carbide of gas containing organic matter;

(5) Graphites of (1) to (4).

Regarding (2), it is not particularly limited as long as it is a carbonizable substance, and examples thereof include aromatic hydrocarbons such as pitch raw materials, acenaphthylene, decacyclene, anthracene, and phenanthrene; and N-ring compounds such as phenazine and acridine. ; S-ring compounds such as thiophene and dithiophene; polyphenylenes such as biphenyl and terphenyl; polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, their insoluble processed products, nitrogen-containing polyacrylonitrile, poly Organic polymers such as pyrrole; organic polymers such as sulfur-containing polythiophene and polystyrene; natural polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, and sucrose Polymers; thermoplastic resins such as polyphenylene sulfide and polyphenylene ether; thermosetting resins such as furfuryl alcohol resins, phenolic resins, and imide resins; Organic substances such as solutions formed in solvents; carbonizable gases, etc.

Among these, the asphalt raw material is preferable because it can produce a high-yield material due to its high carbon residue rate. In addition, in this specification, a "pitch raw material" refers to pitch and a substance belonging to pitch, and refers to a substance that can be carbonized and/or graphitized by appropriate treatment. As an example of a specific pitch raw material, tar, heavy oil, pitch, etc. can be used. Specific examples of tar include coal tar, petroleum tar, and the like. Specific examples of the heavy oil include catalysis oil, pyrolysis oil, atmospheric residual oil, vacuum residual oil, and the like of petroleum heavy oil. In addition, specific examples of pitch include coal tar pitch, petroleum pitch, synthetic pitch, and the like. Among them, coal tar pitch is preferable because of its high aromaticity. Any one of these pitch raw materials may be used alone, or two or more of them may be used in combination in any desired ratio.

As a preferred example of (3), it is possible to enumerate a solution obtained by dissolving the above-mentioned organic substance in (2) in low-molecular organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and then obtain a solution by thermally decomposing the solution as Precursor carbides.

Regarding (4), hydrocarbon compounds such as methane, ethane, propane, benzene, acetylene, and ethylene; carbon monoxide, and the like are exemplified.

The ratio of the carbonaceous substance (C) contained in the heterooriented carbon composite is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass or more. The upper limit is not particularly limited, as long as there are interfaces with different orientations. If it is less than this range, the bonding of the interface in the hetero-oriented carbon composite may become weak. In addition, if it exceeds this range, the effect of suppressing the deformation of the particles during pressing due to the carbonaceous substance (C) is reduced, and the cycle characteristics are reduced.

As a more preferable configuration of the negative electrode active material used in the lithium secondary battery in the present invention, from the viewpoint of the pressing load at the time of electrode rolling and the viewpoint of the balance of the adhesiveness of the interface as the composite, the hetero-orientation is preferable. The carbonaceous composite contains more than one natural graphite-like carbonaceous substance (B) and more than one carbonaceous substance (C).

For the same reason as above, the mass ratio of the natural graphite-like carbonaceous substance (B) and the carbonaceous substance (C) in the hetero-oriented carbon composite (natural graphite-like carbonaceous substance (B)/carbonaceous substance (C) )) is usually 20/80 or more, preferably 40/60 or more, more preferably 60/40 or more, and still more preferably 70/30 or more. The upper limit thereof is 99.9/0.1 or less, preferably 99/1 or less, more preferably 95/5 or less. If this range is exceeded (if the ratio of the natural graphite-like carbonaceous substance (B) is too large), the adhesion of the interface by the carbonaceous substance (C) may decrease. On the other hand, if it is below this range (if the ratio of the natural graphite-like carbonaceous substance (B) is too small), the pressing load at the time of electrode rolling becomes significantly large, and peeling may occur during rolling.

The heterooriented carbon composite containing natural graphite-like carbonaceous material (B) and carbonaceous material (C) can take any form as long as it does not exceed the scope of the present invention. An example is shown below.

(1) The entire surface or part of the surface of the natural graphite-like carbonaceous substance (B) is attached and/or covered and/or bonded with the carbonaceous substance (C);

(2) The carbonaceous substance (C) is bonded to the entire surface or part of the surface of the natural graphite-like carbonaceous substance (B), and two or more natural graphite-like carbonaceous substances (B) and/or carbonaceous substances (C) Composite form;

(3) A form in which the above (1) and (2) are mixed in an arbitrary ratio.

In addition, the above-mentioned natural graphite-like carbonaceous substance (B) can also be replaced with the carbonaceous substance (C). In addition, as a specific compounding method of the hetero-oriented carbon composite, it can be enumerated that it is attached to the surface of the particle as the nucleus and / or covered and / or bonded form of carbonaceous substances; the surface of a plurality of core particles attached and / or covered and / or bonded form; or the state of non-parallel granulation of core particles. The state of non-parallel granulation here refers to a state in which particles having a certain crystallinity are fixed by other carbonaceous substances in a state of being oriented in a random direction, and are bonded to exhibit hetero-orientation.

[[Preparation of Hetero-Oriented Carbon Composite]]

For the preparation of differently oriented carbon composites, it is described in the following "Manufacturing method 1 and 2 of differently oriented carbon composites". When preparing differently oriented carbon composites, it can be improved by applying heat treatment. Crystalline and can increase capacity per unit weight. The heat treatment temperature is usually 400°C or higher, preferably 1000°C or higher, more preferably 2000°C or higher, still more preferably 2400°C or higher, particularly preferably 2800°C or higher. The upper limit thereof is usually not higher than 3400°C, preferably not higher than 3200°C. If it is less than this range, the crystallinity cannot be sufficiently improved, and there is a possibility that the capacity increase effect per unit weight cannot be obtained. On the other hand, if it exceeds this range, the loss due to the sublimation of carbon cannot be ignored, which may cause a decrease in yield.

[[Properties of Hetero-Oriented Carbon Composite]]

With respect to the properties of the heterooriented carbon composite, it is preferable to simultaneously satisfy any one or more of (1) to (5) shown below.

(1) Circularity

Using circularity as the degree of spherical shape of the heterooriented carbon composite, the circularity of the particles of the heterooriented carbon composite having a particle diameter in the range of 3 to 40 μm is usually 0.1 or more, preferably 0.5 or more, more preferably 0.8 or more, more preferably 0.85 or more, and most preferably 0.9 or more. When the circularity is large, the high current density charge and discharge characteristics are improved, which is preferable. The circularity is defined by the following formula. When the circularity is 1, it is a theoretical true sphere.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the value measured as follows is used: using, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) as a surfactant. In a 0.2% by mass aqueous solution of sorbitan monolaurate (approximately 50mL), after irradiating 28kHz ultrasonic waves with an output power of 60W for 1 minute, specify a detection range of 0.6 to 400μm, and perform a test on particles in the range of particle diameters from 3 to 40μm. Determination.

There is no particular limitation on the method of improving the circularity, but it is preferable to make the shape of the gap between the particles uniform when the electrode body is produced by performing a spheroidization treatment to make it spherical. Examples of spheroidization treatment include a method of mechanically approaching a spherical shape by applying a shear force or a compressive force, and a mechanical/physical treatment method of granulating a plurality of fine particles by the adhesive force possessed by a binder or the particles themselves. wait.

(2) Raman R value, Raman half value width

The Raman R value of the heterooriented carbon composite measured by argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.02 or more, more preferably 0.04 or more, and its upper limit is usually 0.35 or less, preferably 0.30 or less, more It is preferably in the range of 0.25 or less. If the Raman R value is lower than this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

In addition, the Raman half-value width of the carbon material of the present invention is not particularly limited in the vicinity of 1580 cm ^-1 , but it is usually 5 cm ^-1 or more, preferably 10 cm ^-1 or more, and its upper limit is usually 40 cm ^-1 or less, preferably It is in the range of 35 cm ^-1 or less, more preferably 30 cm ^-1 or less. If the Raman half-value width is below this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

The measurement of the Raman spectrum is carried out as follows: Using a Raman spectrometer (such as a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped and filled in the measurement cell, and the surface of the sample in the cell is irradiated with an argon ion laser. At the same time, Rotate the cell in a plane perpendicular to the laser. For the obtained Raman spectrum, the intensity I _A of the peak PA near 1580 cm ^-1 and the intensity I _B of the peak P _B near 1360 cm ^-1 were measured _, and the intensity ratio R (R= _IB / _IA ) was calculated. It is defined as the Raman R value of the carbon material. In addition, the half-value width of the peak _PA in the vicinity of 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the carbon material.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

Raman R value, Raman half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

(3) Tap density

The tap density of the heterooriented carbon composite is usually 0.55 g/cm ³ or more, preferably 0.70 g/cm ³ or more, more preferably 0.9 g/cm ³ or more, particularly preferably 1 g/cm ³ or more. In addition, it is preferably 2.0 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, still more preferably 1.7 g/cm ³ or less, particularly preferably 1.5 g/cm ³ or less. If the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm and dropped in a ²⁰ cm container for vibration until the sample is filled with the upper end surface of the container, and a powder density measuring device (for example, Seishin Enterprise Co., Ltd. The manufactured Tap densor) was vibrated 1000 times with a stroke length of 10 mm, and the density obtained from the volume at that time and the weight of the sample was defined as the tap density.

(4) BET specific surface area

The specific surface area of the heterooriented carbon composite measured by the BET method is usually 0.1 m ² /g or more, preferably 0.7 m ² /g or more, more preferably 1.0 m ² /g or more, and still more preferably 1.2 m ² /g above. The upper limit thereof is usually 100 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. When the value of the specific surface area is below this range, when used as a negative electrode material, lithium acceptance during charging tends to deteriorate, and lithium tends to be deposited on the electrode surface. On the other hand, if it is higher than the above range, when used as a negative electrode material, the reactivity with the non-aqueous electrolytic solution increases, the gas generated tends to increase, and it may be difficult to obtain a preferable battery.

The BET specific surface area is defined as a value measured by pre-drying the sample at 350° C. for 15 minutes under nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), and then, using nitrogen gas Nitrogen-helium mixed gas whose relative pressure value relative to the atmospheric pressure is accurately adjusted to 0.3 is measured by the nitrogen adsorption BET 1-point method using the gas flow method.

(5) Volume-based average particle size

The volume-based average particle diameter of the heterooriented carbon composite is the volume-based average particle diameter (median particle diameter) obtained by the laser diffraction/scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more , and more preferably 7 μm or more. In addition, the upper limit thereof is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, particularly preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode pad, and it may be unpreferable in a battery manufacturing process.

In the present invention, the volume-based average particle diameter is defined by a median particle diameter measured by dispersing carbon powder in polyoxyethylene (20) sorbitan as a surfactant. In a 0.2% by mass aqueous solution (about 1 mL) of monolaurate, it measures using a laser diffraction particle size distribution meter (for example, LA-700 manufactured by Horiba, Ltd.).

From the viewpoint of the balance of battery characteristics, it is preferable to satisfy one or more of the following items (6) to (11) in addition to the above items (1) to (5).

(6) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction using the Gakushin method of the hetero-oriented carbon composite is preferably 0.335 nm or more, and usually 0.340 nm or less, preferably 0.337 nm or less . If it is less than this range, the crystallinity may decrease, which may increase the initial irreversible capacity. In addition, the lower limit of 0.335 is the theoretical value of graphite. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 80 nm or more. If it is less than this range, the crystallinity may decrease, which may increase the initial irreversible capacity.

(7) Ash content

The ash contained in the heterooriented carbon composite is usually 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less with respect to the total mass of the heterooriented carbon composite, and the lower limit thereof is usually 1 ppm or more . If the above-mentioned range is exceeded, the degradation of the battery performance due to the reaction with the non-aqueous electrolytic solution during charge and discharge cannot be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(8) Micropore distribution

The amount of voids in particles with a diameter of 0.01 μm to 1 μm and unevenness on the surface of the particles of the heterooriented carbon composite obtained by mercury porosimetry (mercury porosimetry) is usually 0.001 mL/ g or more, preferably 0.002 mL/g or more, and the upper limit thereof is usually 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder may be required when manufacturing an electrode plate. On the other hand, if it is less than this range, the high current density charge-discharge characteristics deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. On the other hand, if it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of the sample (negative electrode material) was weighed, sealed in a powder container, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, the pressure is reduced to 4psia (about 28kPa), mercury is introduced, the pressure is raised from 4psia (about 28kPa) to 40000psia (about 280MPa) in steps, and then the pressure is lowered to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

(9) True density

The true density of the hetero-oriented carbon composite is usually 2.0 g/cm ³ or more, preferably 2.1 g/cm ³ or more, more preferably 2.2 g/cm ³ or more, still more preferably 2.22 g/cm ³ or more, and the upper limit is 2.26g/cm ³ or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase. In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

(10) Orientation ratio (powder)

The orientation ratio of the hetero-oriented carbon composite is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

· Slit: divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

(11) aspect ratio (powder)

The aspect ratio of the heterooriented carbon composite is theoretically 1 or more, and the upper limit is 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of the carbon material particle and the shortest diameter B perpendicular thereto when viewed three-dimensionally. Observation of particles is performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of the metal with a thickness of 50 microns or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

[[Raw material of natural graphite-like carbonaceous substance (B)]]

As a raw material of the natural graphite-like carbonaceous substance (B) contained in the hetero-oriented carbon composite, generally, a crystal whose interplanar distance (d002) of the (002) plane measured by the X-ray wide-angle diffraction method is 0.340 nm or less is exemplified. It is made of high-strength natural graphite as a raw material. Specifically, powders selected from natural graphite or products obtained by adding mechanically pulverized materials to improve circularity, and/or products obtained by heat-treating them at 100° C. or higher, heat-treated expanded graphite products, or high-purity refined products of these graphites.

Natural graphite (D), which is a precursor of natural graphite-like carbonaceous substances (B), is classified into flake graphite (Flake Graphite), scaly graphite (Crystalline (Vein) Graphite), soil graphite (Amorphous Graphite) (see "Powder Process Technology Integration", ((strain) Industrial Technology Center, issued in Showa 49) graphite item; and "HAND BOOK OF CARBON, GRAPHITE, DIAMOND AND FULLERENES", (issued by Noyes Publications) ). The degree of graphitization is highest in flake graphite, which is 100%, followed by flake graphite, which is 99.9%, while soil graphite is as low as 28%. Flake graphite as natural graphite is produced in Madagascar, China, Brazil, Ukraine, Canada, etc.; flake graphite is mainly produced in Sri Lanka. The main producing areas of soil graphite are the Korean Peninsula, China, Mexico, etc. Among these natural graphites, soil graphite not only usually has a smaller particle size, but also has low purity. In contrast, flaky graphite and flaky graphite can be preferably used in the present invention because they have advantages such as a low degree of graphitization or a low amount of impurities.

[[Preparation of natural graphitic carbonaceous material (B)]]

The preparation of the natural graphite-like carbonaceous material (B) will be described later in "Manufacturing Method 1 and Manufacturing Method 2 of Hetero-Oriented Carbon Composite".

[[Properties of Natural Graphite Carbonaceous Substance (B)]]

For the natural graphite-like carbonaceous substance (B), it is preferable to simultaneously satisfy any one or more of (1) to (11) shown below. In addition, the definition, measurement method, etc. of each are the same as those described in the section of hetero-oriented carbon composite.

(1) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction using the Gakushin method of natural graphite-like carbonaceous is preferably 0.335 nm or more, and usually 0.340 nm or less, preferably 0.337 nm or less. If it is less than this range, the crystallinity may decrease, which may increase the initial irreversible capacity. In addition, 0.335 nm is a theoretical value of graphite. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 90 nm or more. If it is less than this range, the crystallinity may decrease, which may increase the increase in the initial irreversible capacity.

(2) Ash content

The ash contained in natural graphite-like carbonaceous is usually 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and the lower limit thereof is usually 1 ppm or more based on the total mass of natural graphite-like carbonaceous. When the above-mentioned range is exceeded, the deterioration of the battery performance due to the reaction with the non-aqueous electrolytic solution during charging and discharging may not be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Volume-based average particle size

The volume-based average particle size of natural graphite-like carbonaceous is the volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, More preferably, it is 7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode pad, and it may be unpreferable in a battery manufacturing process.

(4) Raman R value, Raman half value width

The Raman R value of the natural graphitic carbonaceous measured by argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.02 or more, more preferably 0.04 or more, and its upper limit is usually 0.35 or less, preferably 0.30 or less, more preferably It is in the range of 0.25 or less. If the Raman R value is lower than this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

In addition, the Raman half-value width of the carbon material of the present invention is not particularly limited in the vicinity of 1580 cm ^-1 , but it is usually 5 cm ^-1 or more, preferably 10 cm ^-1 or more, and its upper limit is usually 40 cm ^-1 or less, preferably 35 cm-1 ⁻¹ or less, more preferably 30 cm ⁻¹ or less. If the Raman half-value width is below this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

(5) BET specific surface area

The specific surface area of natural graphite-like carbonaceous material measured by the BET method is usually 0.1 m ² /g or more, preferably 0.7 m ² /g or more, more preferably 1.0 m ² /g or more, still more preferably 1.5 m ² /g or more . The upper limit thereof is usually 100 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, still more preferably 10 m ² /g or less. When the value of the specific surface area is lower than this range, when used as a negative electrode material, the acceptance of lithium during charging is deteriorated, and lithium is likely to be deposited on the surface of the electrode. On the other hand, if it is higher than the above range, when used as a negative electrode material, the reactivity with the non-aqueous electrolytic solution increases, the gas generated tends to increase, and it may be difficult to obtain a preferable battery.

(6) Micropore distribution

The amount of voids in particles of natural graphite-like carbon equivalent to particles with a diameter of 0.01 μm to 1 μm, and the amount of unevenness due to particle surface roughness measured by mercury porosimetry (mercury intrusion method) is usually 0.01 mL/g Above, preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, the upper limit is usually 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder may be required when manufacturing an electrode plate. If it is less than this range, the high current density charge-discharge characteristics will deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, particularly preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. If it is less than this range, the high current density charge-discharge characteristics may deteriorate.

(7) Circularity

Using circularity as the spherical degree of the natural graphite-like carbon material, the circularity of the particles of the natural graphite-like carbon material with a particle diameter in the range of 3 to 40 μm is usually 0.1 or more, preferably 0.5 or more, more preferably 0.8 or more, More preferably, it is 0.85 or more, and most preferably, it is 0.9 or more. When the circularity is large, the high current density charge and discharge characteristics are improved, which is preferable.

(8) True density

The true density of natural graphite-like carbonaceous is usually above 2.0g/ ^cm3 , preferably above 2.1g/ ^cm3 , more preferably above 2.2g/ ^cm3 , even more preferably above 2.22g/ ^cm3 , and its upper limit is 2.26 g/ ^cm3 or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

(9) Tap density

The tap density of natural graphite-like carbonaceous is usually 0.1 g/cm ³ or more, preferably 0.5 g/cm ³ or more, more preferably 0.7 g/cm ³ or more, particularly preferably 0.9 g/cm ³ or more. In addition, it is preferably 2.0 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. If the tap density is lower than this range, it is difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, making it difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

(10) Orientation ratio (powder)

The orientation ratio of natural graphite-like carbonaceous is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

(11) aspect ratio (powder)

The aspect ratio of natural graphite-like carbon is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

[[Raw material of carbonaceous substance (C)]]

The raw material of the carbonaceous substance (C) contained in the heterooriented carbon composite of the present invention is not particularly limited as long as it can be carbonized, and examples thereof include pitch raw materials, acenaphthylene, decacyclene, anthracene, Aromatic hydrocarbons such as phenanthrene; N-ring compounds such as phenazine and acridine; S-ring compounds such as thiophene and dithiophene; polyphenylenes such as biphenyl and terphenyl; polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, Their insoluble processed products, nitrogen-containing polyacrylonitrile, polypyrrole and other organic polymers; sulfur-containing polythiophene, polystyrene and other organic polymers; cellulose, lignin, mannan, polygalacturaldehyde natural polymers such as polysaccharides represented by acid, chitosan, and sucrose; thermoplastic resins such as polyphenylene sulfide and polyphenylene ether; thermosetting resins such as furfuryl alcohol resins, phenolic resins, and imide resins; or dissolve them in benzene , toluene, xylene, quinoline, n-hexane and other low-molecular organic solvents and other organic substances; carbonizable gases, etc.

Among these, the asphalt raw material is preferable because it can produce a high-yield material due to its high carbon residue rate. In addition, in this specification, a "pitch raw material" refers to pitch and a substance belonging to pitch, and refers to a substance that can be carbonized and/or graphitized by appropriate treatment. As an example of a specific pitch raw material, tar, heavy oil, pitch, etc. can be used. Specific examples of tar include coal tar, petroleum tar, and the like. Specific examples of the heavy oil include catalysis oil, pyrolysis oil, atmospheric residual oil, vacuum residual oil, and the like of petroleum heavy oil. In addition, specific examples of pitch include coal tar pitch, petroleum pitch, synthetic pitch, and the like. Among them, coal tar pitch is preferable because of its high aromaticity. Any one of these pitch raw materials may be used alone, or two or more of them may be used in combination in any desired ratio.

In addition, the content of the above-mentioned quinoline-insoluble pitch raw material is not particularly limited, but a pitch raw material in the range of 30 or less is usually used. The so-called quinoline insoluble components are ultrafine carbon particles or extremely fine sludge contained in a small amount of coal tar. If these substances are too large, the increase in crystallinity will be significantly hindered during the graphitization process, resulting in discharge after graphitization. The capacity is significantly reduced. In addition, as a method for measuring quinoline-insoluble components, for example, the method specified in JIS K2425 can be used.

In addition, as long as the effect of the present invention is not hindered, various thermosetting resins, thermoplastic resins, and the like may be used in combination in addition to the above-mentioned pitch raw materials as raw materials.

[[Preparation of carbonaceous substance (C)]]

The preparation of the carbonaceous material (C) will be described later in "Manufacturing Method 1 and Manufacturing Method 2 of Hetero-Oriented Carbon Composite".

[[Properties of Carbonaceous Matter (C)]]

The carbonaceous substance (C) preferably satisfies any one or more of the following (1) to (4) at the same time. In addition, their definitions, measurement methods, and the like are the same as those described in the section on heterooriented carbon composites.

(1) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) of the carbonaceous substance (C) obtained by X-ray diffraction using the Gakushin method is preferably 0.335 nm or more, and usually 0.345 nm or less, preferably 0.340 nm or less , more preferably 0.337 nm or less. In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually 5 nm or more, preferably 10 nm or more, more preferably 50 nm or more, and even more preferably 80 nm or more. If it is less than this range, the crystallinity may decrease, which may increase the increase in the initial irreversible capacity.

(2) Ash content

The ash contained in the carbonaceous material (C) is usually 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less with respect to the total mass of the heterooriented carbon composite, and the lower limit thereof is usually 1 ppm or more . When the above-mentioned range is exceeded, the deterioration of the battery performance due to the reaction with the non-aqueous electrolytic solution during charging and discharging may not be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Raman R value, Raman half value width

The Raman R value of the carbonaceous substance (C) measured by argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.03 or more, more preferably 0.05 or more, and its upper limit is usually 0.60 or less, preferably 0.30 or less. . If the Raman R value is lower than this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

In addition, the Raman half-value width of the carbonaceous material (C) of the present invention is not particularly limited in the vicinity of 1580 cm ^-1 , but is usually 5 cm ^-1 or more, preferably 10 cm ^-1 or more, and the upper limit is usually 60 cm ^-1 or less , preferably 45 cm ^-1 or less, more preferably 30 cm ^-1 or less. If the Raman half-value width is below this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

(4) True density

The true density of the carbonaceous substance (C) is usually 2.0 g/cm ³ or more, preferably 2.2 g/cm ³ or more, more preferably 2.22 g/cm ³ or more, and its upper limit is 2.26 g/cm ³ or less of the theoretical upper limit of graphite . If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

[Manufacturing method of hetero-orientation carbon composite of negative electrode [5]]

The production method is not particularly limited, and any method can be used as long as it does not exceed the scope of the present invention, and the outlines of preferable examples are as follows (1) and (2).

(1) All or part of the initial raw material of the carbonaceous substance (C) is in a liquid state in any process, and mixed and/or kneaded with the natural graphite (D) in the liquid state;

(2) Devolatilization, sintering, and graphitization are performed on the composite obtained in this step, followed by pulverization and classification to adjust the particle size. There may be one or more pulverization/classification steps between these steps.

Specific examples of the above-mentioned outline are shown below.

[[Manufacturing Method 1 of Differently Oriented Carbon Composite]]

The hetero-orientation carbon composite in the present invention is preferably composed of a natural graphite-like carbonaceous substance (B) and a carbonaceous substance (C) different in orientation from the natural graphite-like carbonaceous substance (B). As an example, the following Method: The above-mentioned natural graphite (D) is mixed with the above-mentioned pitch raw material which is a precursor of the above-mentioned carbonaceous substance (C), or a material obtained by heat-treating and pulverizing the pitch raw material (hereinafter, simply referred to as " Heat treatment of graphite crystal precursors"), natural polymers, etc., after heat treatment A, crushing, and then heat treatment B (sintering, graphitization) methods, etc. In addition, if it is not necessary to make the median particle diameter sufficiently small, the above pulverization may not be performed.

[[[Manufacture of heat-treated graphite crystallization precursors]]]

Heat treatment is performed on the asphalt raw material in advance to obtain a heat-treated graphite crystallization precursor. This prior heat treatment is called asphalt heat treatment. After pulverizing the heat-treated graphite crystal precursor, mix it with natural graphite (D), and then perform heat treatment A. At this time, part or all of it melts. Here, the content of volatile components can be adjusted by prior heat treatment (pitch heat treatment), Thereby, its melting state is properly controlled. Moreover, hydrogen, benzene, naphthalene, anthracene, pyrene, etc. are usually mentioned as a volatile component contained in the heat-treated graphite crystal precursor.

The temperature conditions during the asphalt heat treatment are not particularly limited, but are usually in the range of 300°C to 550°C. If the temperature of the heat treatment is lower than this range, volatile components will increase, so it may be difficult to pulverize safely in air. On the other hand, if the upper limit is exceeded, when heat treatment A is performed, part or all of the heat-treated graphite crystal precursor will not melt, and sometimes it is difficult to obtain the natural graphite-like carbonaceous material (B) and the heat-treated graphite crystal precursor. Particles (hetero-oriented carbon composites). When pitch heat treatment is performed, it is carried out in an atmosphere of an inert gas such as nitrogen or an atmosphere of volatile components generated from pitch raw materials.

There are no particular limitations on the equipment used for heat treatment of asphalt. For example, reactors such as shuttle furnaces, tunnel furnaces, electric furnaces, and autoclaves, and coka (cokes (cokes) heat treatment tanks) can be used. wait. During asphalt heat treatment, stirring can be performed as needed.

In addition, as the heat-treated graphite crystal precursor, it is preferable to use one having a volatile component content of usually 5% by mass or more. By using a graphite crystal precursor with a volatile component content within this range, the natural graphite-like carbonaceous substance (B) and the carbonaceous substance (C) are compounded by heat treatment A, thereby obtaining the hetero-orientation property having the above-mentioned predetermined physical properties. carbon composite.

First of all, heat treatment is performed on the asphalt raw material in advance to produce a bulk mesophase (bulk mesofue one zu, bulk mesophase) as a precursor of graphite crystals (the graphite crystal precursors that have been heat-treated in advance are abbreviated as "heat-treated graphite crystal precursors" below. ”) method is described.

(Volatile components of heat-treated graphite crystallization precursor)

The volatile content of the graphite crystal precursor obtained by pitch heat treatment is not particularly limited, but is usually 5% by mass or more, preferably 6% by mass or more, and usually 20% by mass or less, preferably 15% by mass or less. If the volatile component is lower than the above-mentioned range, then because there are many volatile components, it is sometimes difficult to pulverize safely in the air, and if it exceeds the upper limit, then when heat treatment A is carried out, a part or all of the graphite crystal precursor will not be melted, It may be difficult to obtain particles (hetero-oriented carbon composites) in which natural graphite-like carbonaceous material (B) is composited with a heat-treated graphite crystal precursor. In addition, as a measurement method of volatile components, the method prescribed|regulated by JIS M8812 is used, for example.

(Softening point of heat-treated graphite crystallization precursor)

The softening point of the graphite crystal precursor obtained by pitch heat treatment is not particularly limited, but is usually 250°C or higher, preferably 300°C or higher, more preferably 370°C or higher, and usually 470°C or lower, preferably 450°C or lower , more preferably in the range of 430°C or less. If it is lower than the lower limit, the carbonization yield of the graphite crystallization precursor after heat treatment is low, and it is difficult to obtain a uniform mixture with the natural graphite-like carbonaceous substance (B). Some or all of the body does not melt, and sometimes it is difficult to obtain particles (hetero-oriented carbon composites) in which the natural graphite-like carbonaceous material (B) and the heat-treated graphite crystal precursor are composited.

As the softening point, a value measured by using a thermomechanical analyzer (for example, TMA4000 manufactured by bruke-axs (Bruka-Eyex) Co., Ltd.) under nitrogen flow, a temperature increase rate of 10° C./min, a needle tip shape of 1 mmφ, Under the condition of increasing the weight of 20gf, the penetration method (Penetray-Sion method) was used to measure the sample molded to a thickness of 1mm by a tablet molding machine.

(Crushing of Heat-treated Graphite Crystal Precursor)

Next, the heat-treated graphite crystal precursor obtained by heat-treating the pitch is pulverized. This is because, by heat treatment, the crystals of heat-treated graphite crystal precursors with large units arranged in the same direction are miniaturized, and/or the natural graphite (D) and heat-treated graphite crystal precursors are uniformly mixed and composited.

The pulverization of the graphite crystal precursor obtained by pitch heat treatment is not particularly limited, but the particle size of the heat-treated graphite crystal precursor after pulverization is usually 1 μm or more, preferably 5 μm or more, and usually 10 mm or less, preferably 5 mm or less, more preferably It is 500 μm or less, particularly preferably 200 μm or less, further preferably 50 μm or less. When the above-mentioned particle size is lower than 1 μm, the surface of the heat-treated graphite crystal precursor is oxidized due to contact with air during or after pulverization, which hinders the improvement of crystallinity in the graphitization process, and sometimes causes a decrease in the discharge capacity after graphitization. reduce. On the other hand, if the above-mentioned particle size exceeds 10 mm, the miniaturization effect due to pulverization will be weakened, the crystals will be easily oriented, and the carbonaceous substance (C) will be easily oriented, and the activity of the electrode using the different orientation carbonaceous composite (A) will be reduced. The material orientation ratio becomes low, and it becomes difficult to suppress electrode expansion during electrode charging. And/or since the difference in particle size between the natural graphite (D) and the heat-treated graphite crystal precursor becomes large, it is difficult to mix uniformly, and the compounding tends to become uneven in some cases.

The device used for pulverization is not particularly limited, for example, as a coarse pulverizer, shear mills, jaw crushers, impact crushers, cone crushers, etc. can be cited; as intermediate pulverizers, Roller crushers, hammer mills, and the like; examples of fine pulverizers include ball mills, vibration mills, pin mills, stirring mills, jet mills, and turbo mills.

[[[Natural graphite (D) and thermal treatment of heat-treated graphite crystallization precursors]]]

Mix natural graphite (D) and heat-treated graphite crystal precursor (raw material of carbonaceous substance (C)) in a predetermined ratio, and perform heat treatment A, pulverization, and heat treatment B (sintering, graphitization), thereby producing hetero-orientation carbon composite.

(mixture of natural graphite (D) and heat-treated graphite crystallization precursor)

The mixing ratio of natural graphite (D) and the heat-treated graphite crystal precursor carried out before heat treatment A is not particularly limited, and the ratio of natural graphite (D) to the mixture is usually 20% by mass or more, preferably 30% by mass or more, more preferably 40% by mass or more, and usually 95% by mass or less, preferably 90% by mass or less. If it is lower than the lower limit, then due to the increase in the proportion of the carbonaceous substance (C) in the heterogeneous carbon composite (A), it is difficult to increase the packing density when the electrode is made, an excessive pressing load is required, and sometimes the Effect of compounding natural graphite-like carbonaceous material (B). If the upper limit is exceeded, the exposure of the surface of the natural graphite-like carbonaceous material (B) in the different-oriented carbon composite (A) increases, and the specific surface area of the different-oriented carbon composite (A) may become larger. It may not be preferable in terms of powder physical properties.

When mixing the natural graphite (D) and the heat-treated graphite crystal precursor adjusted to a predetermined particle size, the device used is not particularly limited, for example, a V-type mixer, a W-type mixer, a variable container type mixer, a mixer Mills, tumble mixers, shear mixers, etc.

(heat treatment A)

Next, heat treatment A is performed on the mixture of natural graphite (D) and heat-treated graphite crystallization precursor. This is because the natural graphite (D) and the miniaturized heat-treated graphite crystal precursor particles are contacted and fixed in a non-oriented state by remelting or fusing the pulverized heat-treated graphite crystal precursor particles. Accordingly, the mixture of natural graphite (D) and heat-treated graphite crystal precursor can be not only a mixture of particles, but also a more uniform composite mixture (hereinafter appropriately referred to as "graphite composite mixture").

The temperature condition of the heat treatment A is not particularly limited, but is usually 300°C or higher, preferably 400°C or higher, more preferably 450°C or higher, and usually 650°C or lower, preferably 600°C or lower. If the temperature of heat treatment A is lower than the above range, a large amount of volatile components will remain in the material after heat treatment A, so the powders may be fused during the sintering or graphitization process, and regrinding may be necessary. On the other hand, if the above-mentioned range is exceeded, the remelted components will be separated into needles at the time of pulverization, which may lead to a decrease in the tap density. The heat treatment A is performed in an atmosphere of an inert gas such as nitrogen or an atmosphere of volatile components generated from the pulverized and miniaturized heat-treated graphite crystal precursor.

The apparatus used for the heat treatment A is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, etc. can be used.

(Crushing of Heat-treated Graphite Crystal Precursor and Replacement Treatment of Heat-Treatment A)

However, as an alternative to the above pulverization and heat treatment A, it may be a treatment that can make the structure of the heat-treated graphite crystal precursor fine and non-oriented. For example, it may be performed in a temperature range where the heat-treated graphite crystal precursor melts or softens. In the process of imparting mechanical energy, it is mixed with natural graphite (D) and heat-treated.

The heat treatment as the replacement treatment is not particularly limited, but it is usually performed at 200°C or higher, preferably 250°C or higher, and usually 450°C or lower, preferably 400°C or lower. If the temperature condition is lower than the above-mentioned range, the melting and softening of the graphite crystal precursor during the substitution treatment may be insufficient, and it may be difficult to perform composite formation with natural graphite (D). In addition, if it exceeds the above range, the heat treatment is likely to proceed rapidly, and particles such as carbonaceous heat-treated graphite crystal precursors are separated into needles during pulverization, which may easily lead to a decrease in tap density.

This replacement treatment is usually performed in an inert atmosphere such as nitrogen or an oxidizing atmosphere such as air. However, when the treatment is performed in an oxidizing atmosphere, it may be difficult to obtain high crystallinity after graphitization, so it is necessary to prevent excessive infusion by oxygen. Specifically, the amount of oxygen in the graphite crystal precursor after the substitution treatment is usually 8% by mass or less, preferably 5% by mass or less.

In addition, the device used for the replacement treatment is not particularly limited, and for example, a mixer, a kneader, or the like can be used.

(crushed)

Next, the graphite composite mixture subjected to the heat treatment A is pulverized. This is because the lumps of the graphite composite mixture melted or fused in a finer structure and non-oriented state by heat treatment A to be composited with natural graphite (D) are pulverized to reach the target particle size.

The particle size of the pulverized graphite composite mixture is not particularly limited, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, further preferably 7 μm or more, and usually 50 μm or less, preferably 35 μm or less, more preferably Below 30μm. If the particle size is less than the above range, the tap density of the hetero-oriented carbonaceous composite (A) becomes small, so it is difficult to increase the filling density of the active material when it is made into an electrode, and it is difficult to obtain a high-capacity battery. On the other hand, if it exceeds the above range, when an electrode is produced by coating as the hetero-oriented carbonaceous composite (A), coating unevenness may easily occur.

There is no particular limitation on the device used for pulverization. For example, as a coarse pulverizer, a jaw crusher, an impact crusher, a cone crusher, etc. can be mentioned; as an intermediate pulverizer, a roll crusher can be mentioned. , hammer mill, etc.; examples of fine pulverizers include ball mills, vibration mills, pin mills, stirring mills, jet mills, and the like.

(Heat treatment B: sintering)

Heat treatment B refers to sintering and graphitization. Next, the sintering will be described. However, sintering can also be omitted. The graphite composite mixture pulverized by pulverization is sintered. This is because fusion of the graphite composite mixture during graphitization is suppressed, and volatile components of the graphite composite mixture are removed by sintering.

The temperature conditions for sintering are not particularly limited, but are usually 600°C or higher, preferably 1000°C or higher, and the upper limit is usually 2400°C or lower, preferably 1300°C or lower. If the temperature condition is lower than the above-mentioned range, fusion of graphite composite mixture powder may easily occur during graphitization. On the other hand, if the above-mentioned range is exceeded, the sintering equipment will require cost, so it is usually carried out within the range of the above-mentioned temperature conditions.

The sintering is performed in an inert atmosphere such as nitrogen gas or a non-oxidizing atmosphere formed by gas generated from the re-pulverized graphite composite mixture. In addition, in order to simplify the production process, graphitization may be directly performed without performing the sintering process.

The apparatus used for sintering is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, a coke roasting furnace, a rotary kiln, and the like can be used.

(Heat treatment B: graphitization)

Next, graphitization is performed on the sintered graphite composite mixture. This is because the discharge capacity in battery evaluation is increased and the crystallinity is improved. By graphitization, a hetero-oriented carbonaceous composite (A) can be obtained.

The temperature conditions for graphitization are not particularly limited, but are usually 2800°C or higher, preferably 2900°C or higher, more preferably 3000°C or higher, and usually 3400°C or lower, preferably 3200°C or lower. If the above-mentioned range is exceeded, the reversible capacity of the battery may decrease, and it may be difficult to manufacture a high-capacity battery. Moreover, when exceeding the said range, the amount of sublimation of graphite may become large easily.

Graphitization is carried out in an inert atmosphere such as argon gas or in a non-oxidizing atmosphere formed by the gas generated from the sintered graphite composite mixture. The apparatus used for graphitization is not particularly limited, and examples thereof include a direct electric furnace, an Acheson electric furnace, an indirect electric resistance heating furnace, an induction heating furnace, and the like.

In addition, Si, B, etc. can also be added to the material (natural graphite (D), pitch raw material, or graphite crystal precursor) or on the surface during graphitization or in the previous process, that is, from heat treatment to sintering. graphitization catalyst.

(other processing)

In addition, as long as the effects of the present invention are not hindered, various processing such as classification processing may be performed in addition to the above-mentioned processing. The classification treatment is to make the particle size after the graphitization treatment the target particle size, and to remove coarse powder and fine powder.

As a device used for classification treatment, there is no particular limitation, for example, in the case of dry sieving, a rotary sieve, a shaking sieve, a rotary sieve, a vibrating sieve, etc. can be used; in the case of dry air classification , can use gravity classifier, inertial force classifier, centrifugal force classifier (classifier, cyclone separator), etc.; wet screening can use mechanical wet classifier, hydraulic classifier, sedimentation classifier, centrifugal wet classifier etc.

The classification treatment may be continued immediately after the pulverization after the heat treatment A, or may be performed at another time, such as after sintering after pulverization, or after graphitization. In addition, the classification process itself can also be omitted. However, from the viewpoint of reducing the BET specific surface area of the heterooriented carbonaceous composite (A) and the viewpoint of productivity, it is preferable to continue immediately after the pulverization after the heat treatment A.

(Processing after production of the hetero-oriented carbonaceous composite (A))

In order to control the BET specific surface area of the negative electrode material, improve the electrode compactness, increase the discharge capacity, and reduce costs, etc., it is also possible to add artificial graphite powder or natural stone to the heterooriented carbonaceous composite (A) produced in the above order. Toner powder and mix.

[Manufacturing Method 2 of Different Orientation Carbon Composite of Negative Electrode [5]]

A heterooriented carbon composite can be produced as follows. The hetero-orientation carbon composite in the present invention is preferably composed of a natural graphite-like carbonaceous substance (B) and a carbonaceous substance (C) different in orientation from the natural graphite-like carbonaceous substance (B). As an example, The following method: in the above-mentioned natural graphite (D), the pitch raw material as the precursor of the above-mentioned carbonaceous substance (C) is subjected to "kneading (mixing)", "forming", "sintering", "graphitization", "crushing "The process to manufacture and so on. However, among these steps, "molding", "sintering" and "crushing" may be omitted and/or performed simultaneously with other steps. Specifically, it can be obtained by the production methods listed below and the like.

[[kneading (mixing)]]

Mixing of raw materials such as natural graphite (D), a pitch raw material, and a graphitization catalyst added as desired is performed. At this time, it is preferable to heat for uniform mixing. Thereby, a liquid pitch raw material is added to the natural graphite (D) and the raw material that does not melt at the kneading temperature. At this time, you can add all the raw materials into the kneader and knead and heat up at the same time, or you can put ingredients other than asphalt raw materials into the kneader and heat them under stirring. state of asphalt raw material.

The heating temperature is usually higher than the softening point of the pitch raw material, preferably at a temperature higher than the softening point by 10°C or higher, more preferably in a temperature range higher than the softening point by 20°C or higher. In addition, the upper limit is usually not more than 300°C, preferably not more than 250°C. If it is less than this range, the viscosity of the asphalt raw material will become high, and mixing may become difficult. On the other hand, if it exceeds this range, the viscosity of the mixed system may become too high due to volatilization and polycondensation.

The mixer is preferably a model having stirring blades, and general-purpose stirring blades such as Z type and Machisket type can be used for the stirring blades. The amount of the raw material charged into the mixer is usually 10% by volume or more, preferably 15% by volume or more, and 50% by volume or less, preferably 30% by volume or less, based on the volume of the mixer. The mixing time must be 5 minutes or more, and the longest time until a significant change in viscosity due to volatilization of volatile components is brought about is usually 30 to 120 minutes. The mixer is preferably preheated to kneading temperature prior to mixing.

[[forming]]

The obtained mixture may be directly supplied to a devolatilization/sintering process for removing volatile components and carbonization, but for ease of handling, it is preferably supplied to the devolatilization/sintering process after molding.

The molding method is not particularly limited as long as the shape can be maintained, and extrusion molding, die molding, hydrostatic molding, and the like can be used. Among them, extrusion molding or mold molding is preferred, because extrusion molding is easy to orient particles in the molding body, and mold molding is easier to operate than hydrostatic molding from the viewpoint of productivity, although the particle orientation remains random. A molded body can be obtained without destroying the structure of random orientation.

The forming temperature may be any of room temperature (low temperature) and heating (high temperature, temperature above the softening point of the pitch raw material). When molding at low temperature, in order to improve the moldability and obtain the uniformity of the molded product, it is desirable to coarsely pulverize the mixture cooled after kneading to a maximum size of 1 mm or less. The shape and size of the molded body are not particularly limited, but in thermoforming, if the molded body is too large, it will take time to uniformly preheat before molding, so it is generally preferable to have a maximum size of about 150 cm or less.

If the pressure of the molding pressure is too high, it will be difficult to remove the volatile components passing through the micropores of the molded body, and the natural graphite (D) that is not perfectly round will be oriented, and the pulverization in the subsequent process will become difficult, so the molding pressure The upper limit is usually 3000 kgf/cm ² (294 MPa) or less, preferably 500 kgf/cm ² (49 MPa) or less, more preferably 10 kgf/cm ² (0.98 MPa) or less. The lower limit pressure is not particularly limited, but is preferably set to such an extent that the shape of the compact can be maintained in the devolatilization/sintering process.

[[Devolatilization/Sintering]]

The obtained molded body was devolatilized/sintered in order to remove the volatile components of the natural graphite (D) and pitch raw materials, and to prevent contamination of the filler during graphitization and adhesion of the filler to the molded body. Devolatilization/sintering is performed at a temperature of usually 600°C or higher, preferably 650°C or higher, and usually 1300°C or lower, preferably 1100°C or lower, for 0.1 to 10 hours. In order to prevent oxidation, heating is usually carried out under the circulation of inert gas such as nitrogen and argon, or in a non-oxidizing atmosphere filled with granular carbon materials such as coke slag (breeze) and packed coke (Packing coke) in the gap.

The equipment used for devolatilization and sintering is not particularly limited as long as it can be sintered in a non-oxidizing atmosphere, such as an electric furnace, a gas furnace, and a coke roasting furnace for electrode materials. In order to remove volatile components, the temperature increase rate during heating is preferably low, usually at 3 to 100°C/hour from about 200°C where low boiling point components start to volatilize to around 700°C where only hydrogen is generated.

[[Graphitization]]

The carbide shaped body obtained by devolatilization/sintering is then graphitized by heating at high temperature. The conditions for graphitization are the same as those described in Production Method 1.

In order to prevent oxidation, graphitization is performed under the flow of an inert gas such as nitrogen or argon, or under a non-oxidizing atmosphere in which a granular carbon material such as coke slag or filled coke is filled in the gap. The equipment used in graphitization is not particularly limited as long as it is an electric furnace, a gas furnace, an Acheson electric furnace for electrode materials, etc. that can achieve the above purpose, and the heating rate, cooling rate, heat treatment time, etc. can be used within the limits of the equipment used. can be set arbitrarily within the range.

[[Crush]]

The graphitized product obtained in this way is usually in the form of a block and is difficult to use as a negative electrode active material. Therefore, pulverization and/or removal of large-diameter and small-diameter substances is performed. The pulverization method of the graphitized product is not particularly limited, and as the pulverization device, the device of mechanical pulverization includes, for example, a ball mill, a hammer mill, a CF mill, a fine mill, a pulverizer, and a pulverization device utilizing wind power, such as a jet Grinding etc. For coarse crushing and intermediate crushing, crushing methods using impact force such as jaw crushers, hammer mills, and roller mills can be used. Here, the pulverization time may be before graphitization or after graphitization.

[Mix of sub-materials of negative electrode [5]]

In addition to the above-mentioned different orientation carbon composites, by containing one or more carbonaceous substances (carbonaceous materials) different from the above-mentioned different orientation carbon composites in the carbonaceous physical properties in the negative electrode active material of the lithium secondary battery of the present invention material), which can further improve the performance of the battery. The "carbonaceous physical properties" mentioned here refer to X-ray diffraction parameters, median particle size, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, micropore distribution, More than one characteristic of circularity and gray content. In addition, as a preferred embodiment, the volume-based particle size distribution is asymmetrical around the median particle size, contains two or more carbon materials with different Raman R values, or has different X-ray parameters. As an example of the effect, reduction of electrical resistance by including carbon materials such as graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and amorphous carbon such as needle coke as sub-materials can be cited. These may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary and arbitrary ratios. When it is added as an auxiliary material, its addition amount is usually 0.1 mass % or more, preferably 0.5 mass % or more, more preferably 0.6 mass % or more, and its upper limit is usually 80 mass % or less, preferably 50 mass % or less, more preferably 40% by mass or less, more preferably in the range of 30% by mass or less. If it is less than this range, it may be difficult to obtain the effect of improving electrical conductivity. If the above range is exceeded, the initial irreversible capacity may increase.

[Making the electrode of the negative electrode [5]]

A common method can be used to manufacture the negative electrode, and the negative electrode can be formed in the same manner as above [5]. The current collector, the thickness ratio between the current collector and the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as those described above.

<Negative pole [6]>

Next, the negative electrode [6] used in the lithium secondary battery of the present invention will be described. The negative electrode contains graphitic carbon particles as the negative electrode active material, and the circularity of the graphitic carbon particles is 0.85 or more. The interplanar distance (d002) of the (002) plane measured by the method is lower than 0.337nm, and the Raman R defined by the ratio of the peak intensity of 1360cm ^-1 to the peak intensity of 1580cm ^-1 measured by argon ion laser Raman spectroscopy The value is 0.12 to 0.8.

[Negative electrode active material of negative electrode [6]]

Next, the negative electrode active material used in the negative electrode [6] will be described.

The negative electrode active material used in the negative electrode [6] of the lithium secondary battery of the present invention contains at least graphitic carbon particles satisfying the following (a), (b) and (c).

(a) The circularity is above 0.85;

(b) The interplanar distance (d002) of the (002) plane measured by wide-angle X-ray diffraction method is less than 0.337nm;

(c) The Raman R value defined by the ratio of the peak intensity at 1360 cm ^-1 to the peak intensity at 1580 cm ^-1 measured by argon ion laser Raman spectroscopy (hereinafter, sometimes simply referred to as "Raman R value" ) is 0.12 to 0.8.

[[Circularity]]

The circularity of the graphitic carbon particles used as the negative electrode active material of the lithium secondary battery of the present invention is usually 0.85 or more, preferably 0.87 or more, more preferably 0.89 or more, particularly preferably 0.92 or more. As an upper limit, when the circularity is 1, it is a theoretical true sphere. If the circularity is lower than this range, the filling property of the negative electrode active material is lowered, and the thermal conductivity is lowered. Therefore, early output recovery may be hindered. In particular, output recovery from a low output state at low temperature may be slow.

The circularity referred to in the present invention is defined by the following formula.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the value measured as follows is used: using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) sorbitol as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50mL) of sugar-alcohol monolaurate with an output of 60W for 1 minute at 28kHz ultrasonic waves, specify a detection range of 0.6-400μm, and measure particles with a particle diameter of 3-40μm .

[[Space between faces (d002)]]

The graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention adopt the interplanar distance (d002) of the (002) plane measured by wide-angle X-ray diffraction method to be lower than 0.337nm, preferably 0.336nm the following. As the lower limit, the theoretical value of graphite is 0.335. If it exceeds this range, the crystallinity decreases, the thermal conductivity due to electrons decreases, and the early output recovery characteristics may decrease. In particular, the output recovery from the low output state at low temperature may be slow.

The interplanar distance (d002) of the (002) plane measured by the wide-angle X-ray diffraction method mentioned in the present invention is the d value (layer distance).

In addition, the crystallite size (Lc) of the graphitic carbon material obtained by X-ray diffraction using the Gakushin method is not particularly limited, but is usually 10 nm or more, preferably 30 nm or more, more preferably 80 nm or more. If it is less than this range, the crystallinity is lowered, the thermal conductivity caused by electrons is lowered, and the early output recovery characteristics may be lowered.

[[Raman R value]]

The Raman R value of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention must be 0.12 or more, preferably 0.15 or more, more preferably 0.17 or more, particularly preferably 0.2 or more. The upper limit thereof is preferably 0.8 or less, more preferably 0.6 or less, particularly preferably 0.45 or less. If the Raman R value is lower than this range, the crystallinity of the particle surface is too high, and the output may decrease with the decrease of charge and discharge sites. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the heat conduction by electrons decreases, and the output recovery characteristics may decrease.

The measurement of the Raman spectrum is carried out as follows: Using a Raman spectrometer (such as a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped and filled in the measurement cell, and the surface of the sample in the cell is irradiated with an argon ion laser. At the same time, Rotate the cell in a plane perpendicular to the laser. For the obtained Raman spectrum, the intensity I _A of the peak PA near 1580 cm ^-1 and the intensity I _B of the peak P _B near 1360 cm ^-1 were measured _, and the intensity ratio R (R= _IB / _IA ) was calculated. It is defined as the Raman R value of the graphitic carbon material. In addition, the half-value width of the peak _PA in the vicinity of 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the graphitic carbon material.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

Raman R value, half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

The Raman half-value width near 1580 ^cm of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention is not particularly limited, but it is usually 10 cm ^or more, preferably 15 cm ^-1 or more, and the upper limit is usually 60 cm ^-1 or less, preferably 50 cm ^-1 or less, more preferably 45 cm ^{-1 or} less. If the Raman half-value width is below this range, the crystallinity of the particle surface is too high, and the output may decrease with the decrease of charge and discharge sites. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the heat conduction by electrons decreases, and the output recovery characteristics may decrease.

[[Tap Density]]

The tap density of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention is usually 0.55 g/cm ³ or more, preferably 0.7 g/cm ³ or more, more preferably 0.8 g /cm ³ or more, particularly preferably 1 g/cm ³ or more. In addition, the upper limit is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. When the tap density is lower than this range, when used as a negative electrode, it is difficult to increase the packing density, and the contact area between particles decreases, so thermal conductivity may decrease. On the other hand, if it exceeds this range, the gap between the particles in the electrode will be too small, and the flow path of the non-aqueous electrolyte solution will decrease, so the output itself may decrease.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm and dropped in a ²⁰ cm container for vibration until the sample is filled with the upper end surface of the container, and a powder density measuring device (for example, Seishin Enterprise Co., Ltd. The manufactured Tap densor) was vibrated 1000 times with a stroke length of 10 mm, and the density obtained from the volume at that time and the weight of the sample was defined as the tap density.

[[BET specific surface area]]

The specific surface area of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention measured by the BET method is preferably 0.1 m ² /g or more, more preferably 0.7 m ² /g or more, It is particularly preferably 1 m ² /g or more, further preferably 1.5 m ² /g or more. The upper limit thereof is preferably 100 m ² /g or less, more preferably 50 m ² /g or less, particularly preferably 25 m ² /g or less, further preferably 15 m ² /g or less. If the value of the BET specific surface area is less than this range, when used as a negative electrode material, the acceptance of lithium at the time of charge tends to deteriorate, and lithium tends to precipitate on the electrode surface in some cases. On the other hand, if it is higher than the above range, when used as a negative electrode material, the reactivity with the non-aqueous electrolytic solution increases, the gas generated tends to increase, and it may be difficult to obtain a preferable battery.

The BET specific surface area is defined as a value measured by pre-drying the sample at 350° C. for 15 minutes under nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), and then, using nitrogen gas Nitrogen-helium mixed gas whose relative pressure value relative to the atmospheric pressure is accurately adjusted to 0.3 is measured by the nitrogen adsorption BET 1-point method using the gas flow method.

[[Volume average particle size]]

The volume average particle diameter of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention is defined as the average particle diameter (median particle diameter) of the volume basis obtained by the laser diffraction/scattering method ), preferably 1 μm or more, more preferably 3 μm or more, particularly preferably 5 μm or more, further preferably 7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and particularly preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode pad, and it may be unpreferable in a battery manufacturing process.

[[pore volume]]

For the micropore volume of the graphitic carbon particles used in the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention, the volume equivalent to 0.01 μm to 1 μm in diameter obtained by mercury porosimetry (mercury porosimetry) The amount of voids in the particles and the unevenness of the particle surface is usually 0.01 mL/g or more, preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, and the upper limit is usually 0.6 mL/g or less , preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder may be required when manufacturing an electrode plate. If it is less than this range, the high current density charge-discharge characteristics will deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. If it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of the sample (negative electrode material) was weighed, sealed in a powder container, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, the pressure is reduced to 4psia (about 28kPa), mercury is introduced, the pressure is raised from 4psia (about 28kPa) to 40000psia (about 280MPa) in steps, and then the pressure is lowered to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

[[ash]]

The ash content of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention is preferably 1% by mass or less, particularly preferably 0.5% by mass or less, with respect to the total mass of the graphitic carbon particles. Preferably it is 0.1 mass % or less. In addition, the lower limit thereof is preferably 1 ppm or more. When the above-mentioned range is exceeded, the deterioration of the battery performance due to the reaction with the non-aqueous electrolytic solution during charging and discharging may not be ignored. On the other hand, if it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

The true density of the graphitic carbon particles is usually 2.0 g/cm ³ or more, preferably 2.1 g/cm ³ or more, more preferably 2.2 g/cm ³ or more, still more preferably 2.22 g/cm ³ or more, and the upper limit is 2.26 g /cm ³ or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase. In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

[[Orientation Ratio]]

The orientation ratio of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. scope. If it is less than this range, high-density charge-discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

· Slit: divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

[[Aspect Ratio]]

The aspect ratio of the graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention is theoretically 1 or more, the upper limit is 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may be generated when forming an electrode plate, a uniform coating surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of a particle and the shortest diameter B perpendicular thereto in three-dimensional observation. Observation of particles is performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of the metal with a thickness of 50 microns or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

The graphitic carbon particles used as the negative electrode active material of the negative electrode [6] in the lithium secondary battery of the present invention may be naturally produced or artificially produced, but preferably the graphitic carbon particles contain natural graphite. In addition, naturally occurring substances or artificially produced substances may also be subject to specific treatments. In addition, the production method (including the sorting method) is not particularly limited, and for example, graphitic carbon particles having the above-mentioned characteristics can be obtained by sorting using a classification method such as sieving or wind classification.

Among these, particularly preferable graphitic carbon particles are produced by modifying naturally occurring carbonaceous particles or artificially produced carbonaceous particles by subjecting them to mechanical energy treatment. More preferably, the carbonaceous particles used as a raw material for mechanical energy treatment contain natural graphite.

[[Mechanical Energy Processing]]

Next, this mechanical energy processing will be described. The carbonaceous particles as the raw material to be subjected to the mechanical energy treatment are not particularly limited, and include natural or artificial graphite-based carbonaceous particles, carbonaceous particles that are precursors of graphite, and the like. The characteristics of these raw materials are shown below.

[[[Graphite-like carbonaceous particles as raw material for mechanical energy processing]]]

Regarding the properties of the raw material graphite-based carbonaceous particles, it is preferable to satisfy any one or more of the following (1) to (11) at the same time. In addition, the measurement methods and definitions of the physical properties are the same as in the case of the above-mentioned graphitic carbon particles.

(1) X-ray parameters

The d value (interlayer distance) of the lattice plane (002) obtained by the X-ray diffraction using the Gakushin method of the raw material graphite-based carbonaceous particles is preferably 0.335 nm or more, and the upper limit is usually 0.340 nm or less, preferably 0.337 nm the following. In addition, the crystallite size (Lc) of the graphitic carbonaceous particles obtained by X-ray diffraction using the Gakushin method is usually 30 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. If it is less than this range, the crystallinity may decrease, which may increase the increase in the initial irreversible capacity.

(2) Ash content

The ash contained in the raw graphite-like carbonaceous particles is 1% by mass or less, preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and the lower limit is usually 1 ppm or more based on the total mass of the graphite-like carbonaceous particles. When the above-mentioned range is exceeded, the deterioration of the battery performance due to the reaction with the non-aqueous electrolytic solution during charging and discharging may not be ignored. If it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

(3) Volume-based average particle size

The volume-based average particle size of the raw graphite-based carbonaceous particles is defined as the volume-based average particle size (median particle size) obtained by the laser diffraction/scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and more preferably 7 μm or more. The upper limit is not particularly limited, but is usually 10 mm or less, preferably 1 mm or less, more preferably 500 μm or less, further preferably 100 μm or less, particularly preferably 50 μm or less. If it is less than the above range, the particle diameter becomes too small by application of mechanical energy treatment, which may result in an increase in irreversible capacity. In addition, if it exceeds the above-mentioned range, it will be difficult for the device for applying mechanical energy treatment to operate effectively, which may result in a loss of time.

(4) Raman R value, Raman half value width

The Raman R value of the raw graphitic carbonaceous particles measured by argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and its upper limit is usually 0.6 or less, preferably 0.4 or less. If the Raman R value is lower than this range, the crystallinity of the particle surface is too high, the Raman value increases due to the application of mechanical energy treatment, and due to the decrease in crystallinity, Li enters the interlayer sites with charge and discharge. The number of dots sometimes decreases, that is, the charge acceptance sometimes decreases. On the other hand, if it exceeds this range, the crystallinity of the particle surface will further decrease due to the mechanical energy treatment, and the reactivity with the non-aqueous electrolyte solution will increase, resulting in a reduction in efficiency or an increase in generated gas.

In addition, the Raman half-value width of 1580 cm ^-1 is not particularly limited, and is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and its upper limit is usually 50 cm ^-1 or less, preferably 45 cm ^-1 or less, more preferably The range below 40cm ^-1 . If the Raman half-value width is lower than this range, the crystallinity of the particle surface is too high, the Raman value increases due to the application of mechanical energy treatment, and due to the decrease in crystallinity, Li enters the interlayer due to charge and discharge. The number of sites may decrease, that is, the charge acceptance may decrease. On the other hand, if it is higher than this range, the crystallinity of the particle surface will further decrease due to the application of mechanical energy treatment, and the reactivity with the non-aqueous electrolyte solution will increase, resulting in a decrease in efficiency or an increase in generated gas.

(5) BET specific surface area

The specific surface area of the raw graphite-based carbonaceous particles measured by the BET method is usually 0.05 m ² /g or more, preferably 0.2 m ² /g or more, more preferably 0.5 m ² /g or more, particularly preferably 1 m ² /g or more . The upper limit thereof is usually 50 m ² /g or less, preferably 25 m ² /g or less, more preferably 15 m ² /g or less, particularly preferably 10 m ² /g or less. If the value of the BET specific surface area is lower than this range, the BET specific surface area increases due to the application of mechanical energy treatment, and the acceptance of lithium tends to deteriorate during charging, and lithium tends to be deposited on the electrode surface. On the other hand, if it is higher than the above-mentioned range, the BET specific surface area is further increased due to the application of mechanical energy treatment, and when used as a negative electrode active material, the reactivity with the non-aqueous electrolyte increases, and the gas generated tends to increase, sometimes difficult Get the best battery.

(7) Circularity

Using the degree of circularity as the degree of sphericity of the raw material graphite-like carbonaceous particles, the particle diameter of the raw material graphite-like carbonaceous particles is preferably 0.1 or more, more preferably 0.2 or more, and particularly preferably 0.1 or more. 0.4 or more, more preferably 0.5 or more, most preferably 0.6 or more. If it is less than this range, even if a mechanical energy treatment is applied, the terraformation will not be sufficient, and the high current density charge and discharge characteristics may deteriorate.

(8) True density

The true density of the raw graphite-based carbonaceous particles is usually 2 g/cm ^or more, preferably 2.1 g/cm ^or more, more preferably 2.2 g/cm ^or more, further preferably 2.22 g/cm ^or more, and the upper limit is 2.26 g/ ^cm3 or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

(9) Tap density

The tap density of the raw graphite carbonaceous particles is usually 0.05 g/cm ³ or more, preferably 0.1 g/cm ³ or more, more preferably 0.2 g/cm ³ or more, particularly preferably 0.5 g/cm ³ or more. In addition, it is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. If the tap density is lower than this range, the tap density will not be sufficiently improved even if mechanical energy treatment is applied, and when used as a negative electrode active material, it will be difficult to increase the packing density, and a high-capacity battery may not be obtained. On the other hand, if it is higher than this range, when the mechanical energy is applied, the tap density will further increase, and the gap between the particles in the electrode after the electrode is made is too small, and the flow path of the non-aqueous electrolyte is insufficient, and high current Density charge and discharge characteristics may decrease. The tap density of graphite-based carbonaceous particles was also measured and defined by the same method as above.

(10) Orientation ratio (powder)

The orientation ratio of the raw graphite-based carbonaceous particles is usually 0.001 or more, preferably 0.005 or more. The upper limit is theoretically 0.67 or less. If it is less than this range, even if a mechanical energy process is applied, the improvement of an orientation ratio will not be sufficient, and high-density charge-discharge characteristics may fall.

(11) aspect ratio (powder)

The aspect ratio of the graphite-based carbonaceous particles is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, the aspect ratio cannot be sufficiently reduced even if a mechanical energy treatment is applied, and streaks may occur when forming an electrode plate, a uniform coated surface may not be obtained, and high current density charge-discharge characteristics may deteriorate.

Among the above-mentioned raw material graphite-based carbonaceous particles, examples of highly crystalline carbon materials in which the carbon hexagonal network structure is developed include highly oriented graphite in which the hexagonal network surface is clearly grown in a plane orientation, and highly oriented graphite particles assembled in direction of isotropic high-density graphite. Preferable highly oriented graphites include natural graphite produced in Sri Lanka or Madagascar, so-called aggregated graphite precipitated as supersaturated carbon from molten iron, artificial graphite with a partially high graphitization degree, and the like.

According to its properties, natural graphite is classified into flake graphite (Flake Graphite), scaly graphite (Crystalline (Vein) Graphite), soil graphite (Amorphous Graphite) (see "Powder Granular Process Technology Integration", ((Co., Ltd.) Industry Technology Center, Graphite Item, issued in Showa 49); and "HANDBOOK OF CARBON, GRAPHITE, DIAMOND AND FULLERENES", (issued by NoyesPublications)). The degree of graphitization is highest in flake graphite, which is 100%, followed by flake graphite, which is 99.9%, while soil graphite is as low as 28%. Flake graphite as natural graphite is produced in Madagascar, China, Brazil, Ukraine, Canada, etc.; flake graphite is mainly produced in Sri Lanka. The main producing areas of soil graphite are the Korean Peninsula, China, Mexico, etc. Among these natural graphites, soil graphite usually has a small particle size and low purity. In contrast, flaky graphite or flaky graphite has advantages such as a high degree of graphitization and a small amount of impurities, and thus can be preferably used in the present invention.

Artificial graphite can be produced by heating petroleum-based heavy oil, coal-based heavy oil, petroleum coke, or coal-based coke at a temperature of 1500 to 3000° C. or higher in a non-oxidizing atmosphere.

In the present invention, any artificial graphite may be used as a raw material as long as it exhibits high orientation and high capacity after mechanical energy treatment and heat treatment. In addition, in the above-mentioned artificial graphite, even if it is a material with incomplete graphitization, such as a graphite precursor, as long as it can be subjected to mechanical energy treatment to become a graphitic carbon particle satisfying the above physical properties, it can be used as the mechanical energy treatment of the present invention. raw materials used.

[[[Mechanical energy processing content]]]

The mechanical energy treatment of these raw graphite carbonaceous particles can reduce the particle size, so that the ratio of the volume average particle size after the treatment to that before the treatment is less than 1, and the tap density can be improved through the treatment, and the treatment can also It can make the Raman R value more than 1.1 times.

By performing such a mechanical energy treatment, carbonaceous particles such as graphite-based carbonaceous particles as a raw material become particles that maintain high crystallinity as a whole, but become rough near the surface of the particles, and slope and expose edge surfaces. In this way, the surface where lithium ions can come and go increases, and it has a high capacity even at a high current density.

Among the engineering primitive operations that can be effectively used in particle design such as crushing, classification, mixing, granulation, surface modification, and reaction, the "mechanical energy processing" in the present invention belongs to "crushing processing", but it is also Including surface treatment that produces fine structural defects by impacting, rubbing, or compressing the surface structure.

Generally speaking, the so-called crushing treatment refers to applying force to a substance to reduce its size to adjust the particle size, particle size distribution, and filling properties of the substance. Pulverization treatment is classified according to the type of force applied to the substance and the form of treatment. The force exerted on the substance is roughly divided into the following four types: (1) knocking force (impact force), (2) crushing force (compression force), (3) grinding force (grinding force), cutting force (shearing force) cutting force). On the other hand, processing forms are roughly classified into two types: volume crushing in which cracks are generated inside the particles and propagated, and surface crushing in which the particle surfaces are cut off. Volume crushing can be carried out by impact force, compression force and shear force; surface crushing can be carried out by grinding force and shear force. The pulverization treatment is a treatment of various combinations of the type of force applied to these substances and the treatment form. The combination thereof can be appropriately determined according to the purpose of treatment. The pulverization treatment may be performed using a chemical reaction such as blasting or volume expansion, but it is usually performed using a mechanical device such as a pulverizer.

The mechanical energy treatment preferably used in the production of the graphitic carbonaceous particles of the present invention preferably finally includes surface treatment so that the proportion of pulverization of the particle surface (surface pulverization) increases, regardless of the presence or absence of volume pulverization. This is because pulverization of the particle surface is important to remove the corners of carbonaceous particles such as graphite carbonaceous particles to make the particle shape into a circle. Specifically, the kinetic energy treatment may be performed such that surface pulverization is performed after performing a certain volume pulverization, or the dynamic energy treatment may be performed such that only surface pulverization is performed with little volume pulverization. It is also possible to perform mechanical energy processing by simultaneously performing volume crushing and surface crushing. It is preferable to carry out surface pulverization at the end, and to perform mechanical energy treatment such that corners are removed from the surface of the particles.

The mechanical energy treatment of the present invention can reduce the particle diameter, make the ratio of the volume average particle diameter after the treatment to be below 1, and improve the tap density through the treatment, and the Raman R value can also be reached by the treatment. More than 1.1 times.

The "ratio of volume average particle diameter before and after treatment" is a value obtained by dividing the volume average particle diameter after treatment by the volume average particle diameter before treatment. The value of (volume average particle diameter after treatment)/(volume average particle diameter before treatment) is 1 or less, preferably 0.95 or less. If it is substantially 1, the effect of improving the fillability by improving the circularity by mechanical energy treatment may be small. In addition, the particle shape can also be controlled by reducing the particle size so that the ratio of the average particle diameter after treatment to that before treatment is 1 or less.

The tap density can be improved by the mechanical energy treatment in the present invention. Increasing the tap density means increasing the degree of spherification represented by circularity as described later. Therefore, the mechanical energy treatment must be such a treatment. The value of (tap density after treatment)/(tap density before treatment) is 1 or more, preferably 1.1 or more. If it is less than 1, the effect of improving the fillability by improving the circularity may be small.

Through the mechanical energy treatment in the present invention, the Raman R value can be made more than 1.1 times. Improving the Raman R value means reducing the crystallinity near the particle surface as described later, and mechanical energy treatment must be such a treatment. The value of (Raman R value after treatment)/(Raman R value before treatment) is 1.1 or more, preferably 1.4 or more. If it is less than 1.1, the effect of improving charge acceptance due to changes in the Raman R value may be small.

The mechanical energy treatment of the present invention makes the particles into a circular shape, thereby increasing the tap density of these particles. In order to increase the tap density of the powder particles, smaller particles known to fill the interstices formed between the particles and the particles are preferred. Therefore, it is considered that if the carbonaceous particles such as graphite carbonaceous particles are pulverized to reduce the particle size, the tap density can be increased. However, if such a method is used to reduce the particle size, the tap density will generally decrease. . The reason for this is considered to be that the particle shape becomes more amorphous due to pulverization.

On the other hand, as the number of particles (coordination number n) in contact with one particle (particle of interest) in the powder particle group increases, the proportion of voids in the filled layer decreases. That is, as factors affecting the tap density, the size ratio and composition ratio of particles, that is, the particle size distribution, are important. However, this research is only carried out with the spherical particle group of the model, and the carbonaceous particles such as graphite-like carbonaceous particles before treatment used in the present invention are scale-shaped, scale-like, and plate-like. Grinding, classification, etc. are used to control the particle size distribution to increase the tap density, but such a high filling state cannot be produced.

In general, the smaller the particle size of carbonaceous particles such as scaly, scaly, and plate-shaped graphite-based carbonaceous particles, the lower the tap density tends to be. This is considered to be due to the following reasons: as the particles become more amorphous by pulverization, and protrusions such as "burrs", "peeling" or "bending" generated on the surface of the particles increase, and some degree of The strength is caused by the adhesion of finer amorphous particles, etc., so that the resistance between adjacent particles becomes larger, and the filling property is deteriorated.

If the amorphousness of these particles is reduced and the particle shape is close to spherical, even if the particle size becomes smaller, the reduction in filling property will be less. In theory, both large particle size and small particle size particles should show the same degree of Tapped density.

The inventors of the present invention have confirmed through studies that carbonaceous or graphite particles having substantially the same true density and substantially the same average particle diameter exhibit higher tap densities as the shape is more spherical. That is, it is important to make the shape of the particles close to a sphere rather than a circle. If the particle shape is close to spherical, the filling property of the powder is also significantly improved at the same time. In the present invention, the tap density of the powder is used as an index when mechanical energy is applied for the above reasons. When the fillability of the treated powder or granule is higher than that before the treatment, it is considered that the particle is spheroidized by the treatment method used. In addition, in the method of the present invention, if the tap density of the carbon material obtained when the particle size is significantly reduced by processing is compared with the tap density of the carbon material with the same particle size obtained by ordinary pulverization, if it shows a high When the value is , it can be considered as the result of spherification.

级)的结晶性混乱，表现出边缘面的露出变多。As an indicator of the crystallinity of the particles and the roughness of the particle surface, that is, the amount of edge planes of the crystals, the interplanar distance (d002) of the (002) plane and the crystallite size (Lc) measured by the wide-angle X-ray diffraction method can be used. and Raman R value. In general, the smaller the value of the interplanar distance (d002) of the (002) plane and the larger the crystallite size (Lc) of the carbon material, the smaller the Raman R value. That is, all carbonaceous particles such as graphite-based carbonaceous particles exhibit almost the same crystal state. In contrast, the graphitic carbon particles of the present invention take a large Raman R value although the value of the interplanar distance (d002) of the (002) plane is small and the crystallite size (Lc) is large. That is, although the lumps of graphitic carbon particles have high crystallinity, they are near the surface (distance from the particle surface

Grade) crystallinity is disordered, showing increased exposure of edge surfaces.

From the viewpoint of improving fillability, it is more preferable to increase the circularity to 1.02 times, and it is particularly preferred to increase the circularity to 1.04 times by the mechanical energy treatment in the present invention.

[[[Device used in mechanical energy processing]]]

The device for performing mechanical energy processing is selected from devices capable of performing the above-mentioned preferable processing. The inventors of the present invention found that, although one or more of the above-mentioned four kinds of forces applied to the substance can be used, the following device is preferable: the impact force is the main force, and the particle is repeatedly applied to the particle, including the interaction. Mechanical effects such as compression, friction, and shear forces. Specifically, the following device is preferable: the device has a rotor provided with a plurality of blades inside the tank, and when the rotor rotates at a high speed, mechanical effects such as impact compression, friction, and shearing force are applied to the carbonaceous particles introduced into the inside. , so that surface pulverization is performed while volume pulverization is performed. In addition, a device having a mechanism for repeatedly imparting a mechanical action by circulating or convecting the carbonaceous particles is more preferable. The number of blades inside the box is preferably 3 or more, particularly preferably 5 or more.

As an example of a preferable apparatus which satisfies such requirements, the mixing system by Nara Machinery Manufacturing Co., Ltd. is mentioned. When using this apparatus for processing, the peripheral speed of the rotating rotor is preferably set at 30 to 100 m/sec, more preferably at 40 to 100 m/sec, and even more preferably at 50 to 100 m/sec. In addition, the treatment may be performed by simply passing the carbonaceous particles, but it is preferably treated by circulating or staying in the device for 30 seconds or more, more preferably by circulating or staying in the device for 1 minute or more.

When the true density of the graphite-based carbonaceous particles used as a raw material is less than 2.25 and the crystallinity is not so high, it is preferable to further perform a heat treatment for improving crystallinity after performing the mechanical energy treatment. Such heat treatment is preferably performed at 2000°C or higher, more preferably at 2500°C or higher, and even more preferably at 2800°C or higher.

[Making the electrode of the negative electrode [6]]

A common method can be used to produce the negative electrode, and the negative electrode can be formed in the same manner as above [6]. The current collector, the thickness ratio between the current collector and the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as those described above.

<Negative [7]>

Next, the negative electrode [7] used in the lithium secondary battery of the present invention will be described. The negative electrode contains a negative electrode active material (C') containing multiple elements as the negative electrode active material. ) containing a lithium occlusion metal (A') and/or a lithium occlusion selected from the group consisting of Al, Pb, Zn, Sn, Bi, In, Mg, Ga, Cd, Ag, Si, B, Au, Pt, Pd and Sb At least one of the alloys (B'), and contains C and/or N as the element Z.

[Negative electrode active material of negative electrode [7]]

Next, the negative electrode active material used in the negative electrode [7] will be described.

[[composition]]

The negative electrode active material used in the negative electrode [7] of the lithium secondary battery of the present invention is characterized in that it contains at least a metal (lithium storage metal (A')) and/or an alloy (lithium storage alloy ( B')), and contains C and/or N as element Z.

The so-called lithium storage metal (A') refers to more than one selected from Al, Pb, Zn, Sn, Bi, In, Mg, Ga, Cd, Ag, Si, B, Au, Pt, Pd and Sb . Among them, Al, Si, Sn, or Pb is preferable, Si or Sn is more preferable, and Si is still more preferable. The reason why Si is preferable is that the capacity per unit mass is large.

The so-called lithium storage alloy (B') refers to an alloy containing two or more of the above lithium storage metals (A'), or the lithium storage metal (A') contains "lithium storage metal (A') and Alloys of elements other than C and N". The "lithium storage metal (A') and elements other than C and N" are preferably selected from groups 4, 5, 6, 8, 9, 10, 11, 13, and 16 of the periodic table. One or two or more elements in the group, more preferably Ti, Zr, V, Cr, W, B, O, Co elements, still more preferably Ti, Zr, W, O, Co elements. Since these elements tend to form high-melting compounds, they can be preferably used from the viewpoint of controlling reactivity. From the viewpoint of capacity, the content of the "lithium storage metal (A') and elements other than C and N" forming the alloy is preferably 50 mol% or less based on the lithium storage alloy (B').

In addition, as the C and/or N of element Z in the negative electrode active material (C ') that contains multi-element, can enumerate following mode:

1. State contained in lithium occlusion metal (A') and/or lithium occlusion alloy (B') (lithium occlusion substance (D') containing element Z);

2. The state existing around the lithium occlusion metal (A') and/or the lithium occlusion alloy (B') (the element Z is external to the lithium occlusion substance (F));

3. A state in which the states of 1 and 2 above are combined.

As a preferred mode of the lithium storage material (D') containing the element Z, it is preferable that the element Z (C and/or N) exists in the lithium storage metal (A') and/or the lithium storage alloy in a non-equilibrium state Among (B'), and particularly preferably, the lithium-occluding metal (A') is Si.

As a preferred form of the element Z-external lithium storage material (F), it is preferable that the element Z is C, and that C can exhibit conductivity.

The multi-element-containing negative electrode active material (C') used as the negative electrode active material in the present invention contains a lithium storage metal (A') and/or a lithium storage alloy (B'), and contains C and/or N As an essential component, it is preferable to further contain one or two or more elements selected from Groups 4, 5, 6, 8, 9, 10, 11, 13, and 16 of the periodic table. Such elements are more preferably Ti, Zr, V, Cr, W, B, O, and Co elements, and still more preferably Ti, Zr, W, O, and Co elements.

1. Lithium occlusion material containing element Z (D’)

In the lithium-occluding metal (A') of the present invention, since Si is easy to obtain the effect, as the lithium-occluding material (D') containing the element Z, it is preferable that the element Z exists in Si in a non-equilibrium phase. A compound represented by the general formula SiZ _x M _y (wherein, Z, M, x, and y are represented by the following conditions (1) to (4)) having the main component.

(1) Element Z is an element including C and/or N;

(2) The element M is one or two or more elements selected from Si and elements other than Z;

(3) x is a value such that the Z concentration ratio Q(Z) relative to the compound SiaZp existing in equilibrium with the composition closest to Si is 0.10 to 0.95 (wherein, a, p is an integer) Z concentration (p/(a+p)), calculated by the formula Q(Z)=[x/(1+x)]/[p/(a+p)];

(4) y is a number in the range of 0≤y≤0.50.

(about SiZ _x M _y )

((element Z))

Element Z in SiZ _x M _y is an element including C and/or N. In addition, the reasons why C and/or N are preferred as the contained element Z are as follows:

(1) Can form a compound with a higher melting point than Si;

(2) The covalent bond radius is smaller than Si;

(3) The diffusion coefficient in Si is small;

(4) Even if it reacts with lithium, its volume change is small.

Specifically, elements C and N can form equilibrium compounds such as SiC and Si ₃ N ₄ whose melting point is higher than that of Si. And, the free energy that the high-melting point compound usually generates is negative, is a very stable compound, so from the viewpoint of effectively reducing the activity of Si and suppressing the reactivity with the non-aqueous electrolytic solution, preferably C and/or N are used as Element Z.

In addition, since the atomic radius of the covalent bond of elements C and N is smaller than that of Si, it is considered that it is difficult to form a compound that exists in equilibrium in the SiZ _x M _y compound, and it is effective for a more uniform distribution of the element Z at a high concentration, although its The details are not clear, but it is preferable from the viewpoint of effectively reducing the activity of Si and suppressing the reactivity with the non-aqueous electrolytic solution.

In addition, the diffusion coefficients of elements C and N in Si are small, so when elements C and N are dispersed in Si, the agglomeration or crystallization of Si accompanying charge and discharge is suppressed, from suppressing the micronization of Si or combining with non-aqueous It is preferable from the viewpoint of the reaction of the electrolytic solution. In addition, even if elements C and N react with lithium, the volume change is small, and therefore it is difficult to affect the interruption of the conductive path of Si, so it is preferable.

In addition, like elements such as Cu and Ni, Cu ₃ Si, Ni ₂ Si, etc., when the compound that can exist in equilibrium is lower than Si, the activity of Si cannot be effectively reduced and it is difficult to suppress the reactivity with the non-aqueous electrolyte, and Since Cu and Ni elements have a large diffusion coefficient in Si, aggregation or crystallization of Si proceeds along with charging and discharging, and micronization of Si tends to occur, and cycle characteristics may not be improved. In addition, when the compound existing in equilibrium in the SiZ _{x My} compound becomes the main component, the activity of Si cannot be lowered, and the reactivity with the non-aqueous electrolyte cannot be suppressed, so the cycle characteristics may deteriorate.

((element M))

The element M in SiZ _x M _y is one or two or more elements selected from elements other than Si and element Z, preferably selected from group 4, group 5, group 6, group 8, group 9, group 10 of the periodic table One or more elements of Group 11, Group 13, and Group 16 are more preferably Ti, Zr, V, Cr, W, B, O element, more preferably Ti, Zr, W, O element.

In the composition of SiZ _x My _y , x in SiZ _x My _y is a value such that the Z concentration ratio Q(Z) is within a range of usually 0.10 or more, preferably 0.15 or more, more preferably 0.30 or more , especially preferably 0.40 or more, in addition, the upper limit is usually 0.95 or less, preferably 0.85 or less, more preferably 0.75 or less, more preferably 0.65 or less; the Z concentration ratio Q (Z) is relative to the closest Si The Z concentration (p/(a+p)) of the compound SiaZp (wherein, a, p are integers) that composition balance exists, by formula Q(Z)=[x/(1+x)]/[p/( a+p)] and calculated. In addition, the "compound that exists in equilibrium with a composition closest to Si" refers to the compound SiaZp that exists in equilibrium with the value of p/(a+p) taking the lowest value among SiaZp.

In addition, the compound SiaZp existing in the composition equilibrium closest to Si in the present invention is recorded in the phase diagram of Si and element Z (for example, "Desk Handbooks Phase Diagrams for Binary Alloys" published by ASM International Corporation), and in the present invention Here, the aforementioned Z concentration ratio Q(Z) is set with respect to the Z concentration (p/(a+p)) of the SiaZp, and the range of x is defined using the numerical range of the Z concentration ratio Q(Z).

The compound existing in equilibrium as mentioned here is a proportional compound such as the compound Si _a Z _p (wherein, a and p are integers) described as the apex of the line diagram in the above-mentioned phase diagram etc., for example, when Z is C , SiC is known to be a stable compound, and in the present invention, this compound is regarded as a compound existing in equilibrium. Therefore, when Z is C, SiC corresponds to Si _a Z _p of the present invention. In addition, for example, when Z is N, it is known that Si ₃ N ₄ is the most stable compound, but it is also known that Si ₂ N ₃ and SiN also exist as proportional compounds. In the present invention, all these compounds are considered to be balanced compounds present. Therefore, when Z is N, SiN corresponds to Si _a Z _p of the present invention.

On the other hand, the compound in a non-equilibrium phase refers to a compound other than a compound in equilibrium. In the case of a non-equilibrium compound, no specific ratio compound is formed, and Si atoms and Z atoms are uniformly dispersed macroscopically.

If the Z concentration ratio Q(Z) is lower than this range, the effect of lowering the activity of Si is small, the reactivity with the non-aqueous electrolyte cannot be suppressed, the electrode expansion becomes large, and preferable cycle characteristics may not be obtained. On the other hand, if it exceeds this range, a stable compound such as Si _a Z _p in equilibrium will be formed, and even if the element Z is increased, the activity of Si will not decrease, and the reactivity with the non-aqueous electrolyte may not be suppressed. In addition, since Si _a Z _p and the like have low conductivity, when such a compound is formed, the conductivity of the active material deteriorates, doping and dedoping of lithium become difficult, and charging and discharging may not be performed.

Here, when the Z concentration ratio Q(Z) is 1, it means that Si forms a stable compound Si _a Z _p , which is not preferable. On the other hand, when this range is greatly exceeded, it is difficult to obtain the effect of increasing the capacity by containing Si, and preferable battery characteristics may not be obtained.

In addition, when using C and N elements together as the element Z, the Z concentration ratio Q(Z) of the element Z concentration based on the Si _a Z _p standard for each of the two elements is obtained, and the total value is viewed as The operation is Z concentration ratio Q(Z).

y in SiZ _x M _y is a real number satisfying 0≤y≤0.5. When the compound SiZ _x M _y contains the element M, and y≠0, the ratio y of the element M in the compound SiZ _x M _y is usually 0.08 or more, preferably 0.10 or more, and the upper limit is usually 0.50 or less, preferably 0.40 or less, more preferably 0.30 or less. When y exceeds this range, the Si content decreases and it may be difficult to obtain a high capacity. When the element M is substantially not contained, the ratio y of the element M is y=0 or y≒0. In the present invention, y≒0 refers to the case where the element M is unavoidably contained (substantially free of M) in the production process of the negative electrode active material related to the present invention, for example, the case where y is less than 0.08.

The composition of the negative electrode active material (C') that contains multiple elements can be obtained according to the usual method, for example, using an X-ray photoelectric spectrometer (for example, "ESCA" manufactured by ulvac-phi company), so that the side containing the negative electrode compound faces Place it on the sample table and make the surface flat, use aluminum Kα rays as the X-ray source, carry out Ar sputtering while performing depth profile (depth profile) measurement, respectively calculate Si, element Z, Atomic concentrations of elements M etc.

(Composition of SiC _x O _y )

When the element Z is C and the element M is O, in the general formula SiC _x O _y , x is usually 0.053 or more, preferably 0.08 or more, more preferably 0.15 or more, particularly preferably 0.25 or more, and the upper limit thereof is usually 0.90 or less , preferably 0.75 or less, more preferably 0.60 or less, particularly preferably 0.45 or less. In addition, y is usually 0 or more, preferably a value greater than 0, particularly preferably 0.08 or more, more preferably 0.10 or more, and its upper limit is usually 0.50 or less, preferably 0.40 or less, particularly preferably 0.30 or less.

(Existence state of element Z in Si in lithium occlusion material (D') containing element Z)

In the negative electrode compound SiZ _x M _y of the present invention, the XIsz value measured by X-ray diffraction is not particularly limited for the state of the element Z in Si. When the element Z is C, it is preferably 1.2 or less, more preferably 0.7 or less . When the element Z is N, it is preferably 1.1 or less, more preferably 1.0 or less. When the XIsz value is below this range, it means that the phase in which the element Z exists non-equilibrium in Si is the main component, and the compound existing in equilibrium such as Si _a Z _p is not the main component, and the following XIsz value exceeding the above range will not occur. The problem of the situation, it is preferred. When the XIsz value exceeds the above range, that is, when the phase of the compound that exists in equilibrium such as Si _a Z _p is the main component (silicon carbide when the element Z is C, and silicon nitride when the element Z is N), there are the following cases: no The activity of Si is reduced, the reactivity with the non-aqueous electrolyte cannot be suppressed, and the cycle characteristics are deteriorated; due to the low conductivity of Si _a Z _p , etc., the conductivity of the active material film is deteriorated, and the doping and dedoping of lithium The case where the charge and discharge cannot be performed due to the impurity of impurities, or the case where the discharge capacity per unit mass of the active material becomes small. The lower limit of the XIsz value is usually 0.00 or more.

((X-ray diffraction measurement method))

The XIsz value measured by X-ray diffraction can be, for example, provided with the negative electrode active material of the present invention as an irradiation surface, and can be measured using an X-ray diffraction device (for example, "X-ray diffraction device" manufactured by Rigaku Corporation). Conditions are as shown in Examples described later.

In addition, the definition of the XIsz value is as follows.

(((XIsz value when element Z is C)))

The peak intensity Isz at 2θ of 35.7 degrees and the peak intensity Is of 28.4 degrees at 2θ were measured, and the intensity ratio XIsz (XIsz=Isz/Is) was calculated and defined as XIsz of the active material thin film. Here, the peak with a 2θ of 35.7 degrees is considered to be a peak derived from SiC, the peak at 28.4 degrees is a peak derived from silicon, and the XIsz value of 1.2 or less means that almost no SiC was detected.

(((XIsz value when element Z is N)))

The peak intensity Isz at 2θ of 70.2 degrees and the peak intensity Is of 28.4 degrees in 2θ were measured, and the intensity ratio XIsz (XIsz=Isz/Is) was calculated and defined as XIsz of the active material thin film. Here, the peak with a 2θ of 27.1 degrees is considered to be a peak derived from Si ₃ N ₄ , the peak at 28.4 degrees is a peak derived from silicon, and the XIsz value of 1.1 or less means that almost no Si ₃ N ₄ was detected.

(Distribution state of element Z in lithium occlusion material (D') containing element Z)

The element Z in SiZ _x My _y of the present invention exists, for example, in the size of an atom or a molecule or an atomic cluster (cluster) of 1 μm or less, and the distribution state of the element Z is preferably uniformly distributed in SiZ _{x My} , more preferably from SiZ The central part of _x M _y slopes toward the surface direction so that the concentration gradient of the element Z becomes higher (in the case of the film-shaped negative electrode material described later, the concentration gradient becomes higher from the contact part with the current collector to the surface of the film; powdery In the case of the negative electrode material, the concentration gradient is increased from the center of the particle to the surface of the thin film) and distributed obliquely. In the negative electrode active material, when the distribution of the element Z is unevenly localized, the expansion/contraction caused by the charge and discharge of Si occurs concentratedly in the Si part where the element Z does not exist, so as the cycle progresses, the conductivity sometimes decreases. deterioration. The dispersed state of the element Z is shown below, and can be confirmed by EPMA or the like.

(distribution state of element M)

The distribution state of the element M in SiZ _x M _y of the present invention is not particularly limited, and may be uniformly distributed or non-uniformly distributed.

(Raman RC value, Raman RSC value, Raman RS value)

The lithium occlusion substance (D') containing the element Z in the present invention has a Raman RC value measured by Raman spectroscopic analysis usually at least 0.0, and its upper limit is preferably at most 2.0. If the Raman RC value exceeds this range, it will be difficult to obtain the effect of increasing the capacity by containing Si, and it will be difficult to obtain preferable battery characteristics. Especially when the element Z contains C, the Raman RC value of the negative electrode active material SiZ _x My _y of the present invention is preferably 2.0 or less, more preferably 1.0 or less, particularly preferably 0.5 or less. For measurement reasons, the lower limit of the Raman RC value is usually 0.0 or more.

The lithium occlusion substance (D') containing the element Z in the present invention has a Raman RSC value measured by Raman spectroscopic analysis usually at least 0.0, and the upper limit thereof is preferably at most 0.25. When the Raman RSC value exceeds this range, the conductivity deteriorates, doping and dedoping of lithium become difficult, and charge and discharge may not be performed. In addition, especially when the element Z contains C, the RSC value is preferably 0.25 or less, more preferably 0.20 or less. For measurement reasons, the lower limit of the Raman RSC value is usually 0.0 or more.

The Raman RS value of the lithium occlusion substance (D') containing element Z in the present invention measured by Raman spectroscopic analysis is preferably 0.40 or more, more preferably 0.50 or more, and its upper limit is preferably 1.00 or less, more preferably 0.90 the following. If the Raman RS value is below this range, the cycle characteristics may deteriorate. On the other hand, if it exceeds this range, charge and discharge may not be performed, which is not preferable. Especially when the element Z contains C, the RS value is preferably 0.40 or more, more preferably 0.50 or more; the upper limit thereof is preferably 0.75 or less, preferably 0.65 or less. Especially when the element Z contains N, the RS value is preferably 0.40 or more, more preferably 0.50 or more; the upper limit thereof is preferably 1.00 or less, preferably 0.90 or less.

The Raman RC value, Raman RSC value, and Raman RS value measured by Raman spectroscopic analysis in the present invention are obtained by Raman spectroscopic analysis using the following Raman measurement method, and are defined as follows.

((Raman measurement method))

Using a Raman spectrometer (for example, "Raman spectrometer" manufactured by JASCO Corporation), the non-aqueous electrolyte secondary battery negative electrode of the present invention is installed in the measurement cell, and the sample surface in the cell is irradiated with argon ion laser and To measure. By performing background compensation on the measured Raman spectrum, the Raman RC value, Raman RSC value, and Raman RS value are obtained. In addition, the background compensation is carried out as follows: connect the end points of the peaks with a straight line to obtain the background, and then subtract this value from the peak intensity.

Here, the Raman measurement conditions are as follows, and the smoothing process is a simple average of 15 convolution points.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~40mW

·Resolution: 10～20cm ^-1

· Measuring range: 200cm ^-1 ~ 1900cm ^-1

(((Raman RC value)))

Measure the peak intensity Ic of the peak c appearing around 1300cm ^-1 ～1600cm ^-1 , and the peak intensity Ias of the peak as appearing around 300cm ^-1 ～500cm ^-1 , and calculate the intensity ratio RC (RC=Ic/Ias), which is It is defined as the Raman RC value of the negative electrode. Here, peak c and peak as are considered to be peaks derived from carbon and silicon, respectively. Therefore, the Raman RC value reflects the amount of carbon, and the Raman RC value of 2.0 or less means that almost no carbon is detected.

(((Raman RSC value)))

Measure the peak intensity Isc of the peak sc appearing around 650cm ^-1 ～850cm ^-1 , and the peak intensity Ias of the peak as appearing around 300cm ^-1 ～500cm ^-1 , and calculate the intensity ratio RSC (RSC=Isc/Ias), which is It is defined as the Raman RSC value of the negative electrode.

Here, the peak sc and the peak as are considered to be peaks derived from SiC and silicon, respectively. Therefore, the Raman RSC value reflects the amount of SiC, and the Raman RSC value of 0.25 or less means that almost no SiC is detected.

(((Raman RS value)))

The intensity Is at 520 cm ^-1 and the peak intensity Ias of the peak as appearing around 300 cm ^-1 to 500 cm ^-1 were measured, and the intensity ratio RS (RS=Is/Ias) was calculated, which was defined as the Raman RS value of the negative electrode. The Raman RS value reflects the state of Si.

(IRsc value)

The IRsc value of the negative electrode having the negative electrode active material used in the present invention after charging and discharging is preferably 0.90 or higher, more preferably 1.1 or higher, and particularly preferably 1.2 or higher. If the IRsc is lower than this range, the negative electrode containing Si reacts with the non-aqueous electrolyte solution during the cycle, and the amount of active material that can be substantially charged and discharged gradually decreases, and it may be difficult to obtain preferable cycle characteristics. The upper limit of the IRsc value is about 3.0. In addition, the IRsc value measured by the infrared reflected light analysis of the negative electrode in this invention is calculated|required by the following infrared reflected light measurement by the infrared spectrophotometer, and is defined as follows.

((Infrared reflected light analysis method using infrared spectrophotometer))

Using an infrared spectrophotometer (for example, "Magna560" manufactured by Thermoelectron (thermoelectron) Co., Ltd.), the active material surface of the negative electrode of the lithium secondary battery after charging and discharging is installed in the measurement cell, and the reflection method to measure. The measurement was carried out under an inert atmosphere using a sample holder for reflection measurement (Folder) made of diamond as a window material. The IRsc value was obtained by performing background compensation of the measured infrared absorption spectrum. In addition, the background compensation was carried out by connecting the minimum values in the range of 2000 to 4000 cm ^-1 and extending the straight line to obtain the background, and subtracting the value from each intensity. The reflected light intensity Isc at 1600cm ^-1 and the reflected light intensity Iaco at 1650cm ^-1 were measured, and the intensity ratio IRsc (IRsc=Isc/Iaco) was calculated, which was defined as the IRsc value after charging and discharging.

Although the details are not yet clear, it is considered that Isc is derived from the film of Si, and Iaco is derived from the film of alkyllithium carbonate. Therefore, IRsc reflects the state and quantity ratio of the film (solid electrolyte interface: SEI) of the negative electrode, and IRsc A value of 0.9 or more means that it is composed of a film derived from alkyllithium carbonate and a film derived from Si.

<Function, principle>

First, the activity will be described. In general, the so-called activity is a thermodynamic concentration. For a multi-component system containing substances n ₁ , n ₂ ...n _i ..., if the chemical potential of component i is set as μ _i and the chemical potential of pure substance is set as μ _i ⁰ , then the the following formula

μ _i −μ _i ⁰ ＝RTloga _i

The defined a _i is called the activity.

In addition, the ratio γ _i of the activity a _i to the concentration c _i is called the activity coefficient.

a _i /c _i =γ _i

For example, when considering a system containing a solvent and a solute as a thermodynamic solution, the activity coefficient is the chemical potential corresponding to a certain component when the system is regarded as an ideal solution and when the system is regarded as a real solution. The amount of difference between the true chemical potentials of a component. (1) In the case of a real solution in which a certain component i is a solute, if the concentration of the solute becomes lower, the system is close to an ideal solution in which component i is a solute, and the activity coefficient is close to 1. On the contrary, (2) in the case of a real solution in which component i is a solvent, if the concentration of the solvent becomes higher, the system is close to an ideal solution in which component i is a solvent, and the activity coefficient is close to 1. In addition, when the real solution is more stable than the ideal solution, the chemical potential of component i is γx<1.

In the present invention, if Si showing good characteristics is cited as an example, the component i is Si, and by containing the element Z regarded as a solute in Si regarded as a solvent, the activity ai of the solvent _Si decreases, and γ _{When i} <1, the Si compound (solid solution: regarded as a real solution) containing the element Z is more stable than Si ( regarded as an ideal solution), and as a result, the reactivity with the non-aqueous electrolytic solution can be suppressed.

However, if a compound Si _a Z _p in which Si and the element Z exist in equilibrium is formed, the activity of Si cannot be effectively reduced, so it is important that the element Z exists in Si in a non-equilibrium manner.

[Form of negative electrode [7]]

In the present invention, the form of the negative electrode active material used in the negative electrode [7] is usually film or powder. In the present invention, as described in the production method described later, the negative electrode using the thin film active material can be obtained by performing vapor phase film formation of the active material layer on the current collector, and the negative electrode of the powdery active material can be obtained by, for example, forming the active material layer on the current collector. A powdery active material, a binder, and the like are coated on the electrode to form an active material layer.

[[Film active substance]]

[[[structure]]]

Examples of the structure of the thin-film active material formed on the current collector include a columnar structure, a layered structure, and the like.

[[[Film Thickness]]]

The film thickness of the thin-film active material corresponds to the thickness of the active material layer using the thin-film active material, and is usually at least 1 μm, preferably at least 3 μm, and the upper limit thereof is usually 30 μm or less, preferably 20 μm or less, more preferably 15 μm the following. If the film thickness of the thin-film active material is lower than this range, the negative electrode of the present invention using the thin-film active material (hereinafter, the negative electrode using the thin-film active material may be referred to as "thin-film negative electrode") has a capacity of each Small, in order to obtain a large-capacity battery, a large number of negative electrodes are required. Therefore, correspondingly, the total volume of the current collector of the required positive electrode, separator, and thin-film negative electrode itself becomes larger, and the negative active material that can be filled per unit battery volume is essentially It is difficult to increase the battery capacity. On the other hand, if it exceeds this range, the thin-film active material layer may peel off from the current collector substrate due to expansion/shrinkage caused by charge and discharge, and the cycle characteristics may deteriorate.

[[Powder Active Substance]]

[[[shape]]]

Examples of the shape of the powdery active material include a spherical shape, a polyhedral shape, and an amorphous shape.

[[[Volume-Based Average Particle Size]]]

The volume-based average particle diameter of the powdery active material is not particularly limited, but it is usually 0.1 μm or more, preferably 1 μm or more, more preferably 3 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less . If the volume-based average particle size of the powdery active material is lower than the above-mentioned range, it is difficult to obtain a conductive path between the powdery active material or a conductive path between the powdery active material and a conductive agent described later because the particle size is too small, Cycle characteristics sometimes deteriorate. On the other hand, when the above-mentioned range is exceeded, unevenness may occur when the negative electrode active material layer is produced by coating on the current collector as described later.

In addition, as the volume-based average particle diameter of the powdery active material, the value measured as follows: a 2 volume % aqueous solution of polyoxyethylene (20) sorbitan monolaurate ( About 1 mL), using ion-exchanged water as a dispersion medium, using a laser diffraction/scattering particle size distribution meter (for example, "LA-920" manufactured by Horiba Manufacturing Co., Ltd.), measure the average particle diameter (median particle size) based on volume path). In Examples described later, the volume-based average particle diameter was obtained by this method.

[[[BET specific surface area]]]

The BET specific surface area of the powdery active material is not particularly limited, but is usually at least 0.1 m ² /g, preferably at least 0.5 m ² /g, more preferably at least 1.0 m ² /g, and usually at most 100 m ² /g , preferably not more than 30 m ² /g, more preferably not more than 15 m ² /g. If the value of the BET specific surface area is lower than the lower limit of the above-mentioned range, when it is used as a negative electrode, the acceptability of lithium is likely to deteriorate during battery charging, and lithium is likely to be deposited on the surface of the electrode, so it is not preferable in terms of safety. . On the other hand, if the value of the BET specific surface area exceeds the upper limit of the above-mentioned range, the reactivity with the non-aqueous electrolyte solution increases when the negative electrode is made, and a large amount of gas is generated, and it may be difficult to obtain a preferable battery.

In addition, the BET specific surface area of the powdery active material is a value measured by using a surface area meter (for example, a full-automatic surface area measuring device manufactured by Okura Riken) and pre-preparing the powdery active material at 350° C. for 15 minutes in nitrogen gas flow. After drying, it was measured by the nitrogen adsorption BET 1-point method using the gas flow method using a nitrogen-helium mixed gas in which the relative pressure value of nitrogen to the atmospheric pressure was accurately adjusted to 0.3.

[[[Tap Density]]]

The tap density of the powdery active material is not particularly limited, but is usually 0.2 g/cm ³ or more, preferably 0.3 g/cm ³ or more, more preferably 0.5 g/cm ³ or more, and usually 3.5 g/cm ³ or less , preferably in the range of 2.5 g/cm ³ or less. If the tap density is lower than this range, it will be difficult to increase the packing density of the negative electrode active material layer, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, the amount of pores in the negative electrode active material may decrease, and it may be difficult to obtain preferable battery characteristics.

In the present invention, the tap density is defined as follows: the sample is dropped in a ^20cm container through a sieve with an aperture of 300 μm until the powdery active substance is filled with the upper end of the container, and the powder density measuring device (for example, seishin Tap densor (manufactured by the company) was vibrated 1000 times with a stroke length of 10 mm, and the density was obtained from the volume and the weight of the sample at this time, and this density was defined as the tap density.

2. Element Z external lithium occlusion substance (F)

The so-called external lithium storage material (F) of element Z refers to the lithium storage metal (A') and/or lithium storage alloy (B') and C (carbon) (carbonaceous substance) as element Z in the negative electrode. (E')) Compounded substance. In addition, the "composite" mentioned here means a state in which a lithium storage metal (A') and/or a lithium storage alloy (B') and a carbonaceous substance (E') are constrained by bonding, and a state in which they are physically constrained. state, a state in which shape is retained by electrostatic confinement, and the like. The "physical constraint" mentioned here refers to the state in which the lithium occlusion metal (A') and/or lithium occlusion alloy (B') are intermingled in the carbonaceous substance (E') and connected together; the so-called "static Constraint" refers to the state in which the lithium occlusion metal (A') and/or lithium occlusion alloy (B') is attached to the carbonaceous substance (E') by electrostatic energy. In addition, the "state bound by bonding" refers to chemical bonds such as hydrogen bonds, covalent bonds, and ionic bonds.

Here, at least a part of the surface of the lithium storage metal (A') and/or the lithium storage alloy (B') has an interface with the layer of the carbonaceous substance (E') by bonding from the viewpoint of lowering the resistance. Status is favorable. The coverage mentioned here means that there is a chemical bond in at least part of the interface with the surface of the carbonaceous substance (E'), and it shows (1) a state covering the entire surface, (2) a state of partially covering carbonaceous particles, ( 3) The state of selectively covering a part of the surface, (4) The state of existing in an extremely small region containing chemical bonds.

In addition, the crystallinity may change continuously or discontinuously at the interface. That is, the external lithium storage material (F) of the element Z has a lithium storage metal (A') and/or a lithium storage alloy (B') covered and/or bonded by a carbonaceous substance (E') The interface, the crystallinity of which preferably changes discontinuously and/or continuously.

[Properties of the carbonaceous material (E') of the negative electrode [7]]

[[Composition of Carbonaceous Matter (E')]]

The carbonaceous substance (E') is particularly preferably a carbide of (a) or (b) shown below, and may also contain a graphite substance (G') such as natural graphite or artificial graphite. Since the crystallinity of graphite (G) is very high, generally speaking, its conductivity is higher than that of graphite (E). Compared with graphite (E), the effect of improving conductivity is high. From the viewpoint of properties, it is preferable to coexist with graphite (E).

(a) selected from coal-based heavy oil, straight-run heavy oil, decomposed petroleum-based heavy oil, aromatic hydrocarbons, N-ring compounds, S-ring compounds, polyphenylene, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins carbonizable organic matter;

(b) A solution obtained by dissolving these carbonizable organic substances in a low-molecular organic solvent.

Here, coal-based heavy oil is preferably coal tar pitch from soft asphalt to hard asphalt or dry distillation liquefied oil, etc.; straight-run heavy oil is preferably atmospheric residual oil, vacuum residual oil, etc.; decomposed petroleum heavy oil is preferably crude oil , naphtha and other by-products such as ethylene tar during thermal decomposition; as aromatic hydrocarbons, preferably acenaphthylene, decacyclene, anthracene, phenanthrene, etc.; as N-ring compounds, preferably phenazine, acridine, etc.; as S-ring compounds , preferably thiophene, dithiophene, etc.; as polyphenyl, preferably biphenyl, terphenyl, etc.; as organic polymers, preferably polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, their insoluble processed products, poly Acrylonitrile, polypyrrole, polythiophene, polystyrene, etc.; as natural polymers, preferably polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, sucrose, etc.; as thermoplastic resins , preferably polyphenylene sulfide, polyphenylene ether, etc.; as the thermosetting resin, preferably furfuryl alcohol resin, phenolic resin, imide resin, etc.

The carbonaceous substance (E') is preferably a carbide of the above-mentioned "carbonizable organic matter". In addition, it is also preferable to dissolve such "carbonizable organic matter" in benzene, toluene, xylene, quinoline, n-hexane, etc. Molecular carbides obtained in solution in organic solvents.

As the above (a) and (b), liquid ones are particularly preferred. That is, from the viewpoint of forming an interface with the storage metal (A) and/or the lithium storage alloy (B'), carbonization is preferably performed in the liquid phase.

[[Physical properties of carbonaceous substance (E')]]

As the physical properties of the carbonaceous substance (E'), it is preferable to simultaneously satisfy any one or more of the following (1) to (3). In addition, one kind of carbonaceous substance (E') exhibiting such physical properties may be used alone, or two or more kinds may be used in combination in any combination and ratio.

(1) X-ray parameters

Regarding the physical properties of the carbonaceous material (E'), the d value (interlayer distance) (hereinafter, abbreviated as "d002") of the lattice plane (002 plane) obtained by X-ray diffraction using the Gakushin method (hereinafter, abbreviated as "d002") is preferable It is 0.38 nm or less, particularly preferably 0.36 nm or less, further preferably 0.35 nm or less. If the d value is too large, a surface with significantly low crystallinity will be formed and the impedance will increase, so the effect of improving charge acceptance will be small, and the effect of the present invention will be small. In addition, the lower limit is 0.335 nm or more of the theoretical value of graphite.

In addition, the crystallite size (Lc) of the carbon material obtained by X-ray diffraction using the Gakushin method is usually 1 nm or more, preferably 1.5 nm or more. If it is less than this range, the impedance increases, and the effect of improving charge acceptance may become small.

(2) Raman R value, Raman half value width

The Raman R value of the carbonaceous substance (E') portion measured by argon ion laser Raman spectroscopy is usually 0.2 or more, preferably 0.3 or more, more preferably 0.4 or more, and its upper limit is usually 1.5 or less, preferably 1.2 or less range. If the Raman R value is lower than this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

In addition, the Raman half-value width of the carbonaceous material (E') portion near 1580 cm ^-1 is not particularly limited, but is usually 20 cm ^-1 or more, preferably 30 cm ^-1 or more, and its upper limit is usually 140 cm ^-1 or less , preferably in the range of 100 cm ^-1 or less. If the Raman half-value width is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

(3) True density

The true density of the carbonaceous material (E') part is usually 1.4 g/cm ³ or more, preferably 1.5 g/cm ³ or more, more preferably 1.6 g/cm ³ or more, and even more preferably 1.7 g/cm ³ or more, which The upper limit is 2.26 g/cm ³ or less, the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

The negative electrode active material (C') containing multiple elements used in the negative electrode active material of the negative electrode [7] of the lithium secondary battery of the present invention is preferably an occlusion metal (A) and/or a lithium occlusion alloy (B') The element Z exogenous lithium storage material (F) obtained by complexing with the carbonaceous material (E') is preferably carbon that further contains a graphite material (G') other than the carbonaceous material (E') as the element Z (C).

[[Composition and properties of graphitic substance (G')]]

As an example of the composition of the graphitic substance (G'), natural graphite, artificial graphite, and those obtained by pulverizing them are mentioned, and the physical properties of the graphitic substance (G') preferably satisfy the following simultaneously. Any one or more of (1) to (3). In addition, one kind of graphitic substance (G') exhibiting such physical properties may be used alone, or two or more kinds may be used in combination in any combination and ratio.

(1) X-ray parameters

For the graphitic substance (G') portion, the d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method is 0.335 nm or more, the theoretical value of graphite. The upper limit thereof is preferably 0.340 nm or less, more preferably 0.338 nm or less, particularly preferably 0.337 nm or less. If the d value is too large, a surface with significantly low crystallinity will be formed and the impedance will increase, so the effect of improving charge acceptance will be small, and the effect of the present invention will be small.

In addition, the crystallite size (Lc) of the graphitic substance (G') obtained by X-ray diffraction using the Gakushin method is usually 10 nm or more, preferably 50 nm or more, more preferably 80 nm or more. If it is less than this range, since the impedance increases, the effect of improving charge acceptance may become small.

(2) Raman R value, Raman half value width

The Raman R value of the graphitic substance (G') portion measured by argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.10 or more, and its upper limit is usually 0.40 or less, preferably 0.35 or less, more preferably 0.25 or less range. If the Raman R value is lower than this range, the crystallinity of the particle surface may be too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

In addition, the Raman half-value width of the graphitic substance (G') portion near 1580 cm ^-1 is not particularly limited, but is usually 10 cm ^-1 or more, preferably 15 cm ^-1 or more, and its upper limit is usually 50 cm ^-1 or less , preferably in the range of 40 cm ^-1 or less. If the Raman half-value width is lower than this range, the crystallinity of the particle surface is too high, and there may be fewer sites for Li to enter the interlayer due to charge and discharge. That is, charge acceptance may be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolyte solution increases, and the efficiency may decrease or the generated gas may increase.

(3) True density

The true density of the graphitic substance (G') part is usually 2.0 g/cm ³ or more, preferably 2.1 g/cm ³ or more, more preferably 2.2 g/cm ³ or more, and even more preferably 2.22 g/cm ³ or more, which The upper limit is 2.26 g/cm ³ or less, the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the initial irreversible capacity may increase.

The element Z used in the negative electrode active material of the negative electrode [7] of the lithium secondary battery of the present invention is contained in the lithium occlusion substance (F), and the occlusion metal (A) and/or lithium occlusion alloy (B) and carbon The mass ratio of the substance (E) is usually 20/80 or more, preferably 50/50 or more, more preferably 80/20 or more, particularly preferably 90/10 or more, and preferably 99.9/0.1 or less, more preferably 99.9 /1 or less, particularly preferably 98/2 or less. If it exceeds the above range, the effect of having the carbonaceous substance (E) may not be obtained, and if it is below the above range, the effect of increasing the capacity per unit mass may become small. Preferably, the occlusion metal (A) and/or lithium occlusion alloy (B) is 20% by mass or more relative to the total element Z external lithium occlusion substance (F).

When the graphite substance (G') is contained, the graphite substance (G') is preferably 5% by mass or more, more preferably 20% by mass, based on the total amount of the carbonaceous substance (E') and the graphite substance (G'). % or more, more preferably 50% by mass or more. In addition, the upper limit thereof is preferably 99% by mass or less, more preferably 95% by mass or less. If there are too many graphitic substances (G'), the bonding at the interface becomes weak, and sometimes it is difficult to obtain the effect of improving the conductivity, and if there are too few graphitic substances (G'), it is sometimes difficult to obtain ') to improve the electrical conductivity.

In the present invention, the lithium storage substance (F) external to the element Z is usually in the form of film or powder. In addition, in the present invention, the negative electrode using the thin-film active material can be obtained by vapor-phase film-forming the active material layer on the current collector as described in the following manufacturing method, and the negative electrode of the powdery active material can be obtained by For example, an active material layer is formed by coating a powdery active material, a binder, and the like on a current collector.

The preferred ranges of powder physical properties when the lithium occlusion material (F) containing the element Z is in powder form are the same as the ranges of the preferred powder physical properties of the lithium occlusion material (D') containing the element Z.

[Current collector of negative electrode [7]]

(material)

Examples of the material of the current collector include copper, nickel, stainless steel, and the like, and among them, copper, which is easy to process into a thin film and is inexpensive, is preferable. Copper foil includes rolled copper foil produced by calendering and electrolytic copper foil produced by electrolysis, and any of them can be used as a current collector. In addition, when the thickness of the copper foil is thinner than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu-Cr-Zr alloy, etc.) that is stronger than pure copper can be used.

In the current collector made of copper foil produced by the rolling method, since the copper crystals are arranged in the rolling direction, even if the negative electrode is bent tightly or bent at an acute angle, it is not easy to break, and it is suitable for small cylindrical batteries. Electrodeposited copper foil is produced, for example, by immersing a metal drum in a non-aqueous electrolytic solution in which copper ions are dissolved, and passing an electric current while rotating the drum, thereby depositing copper on the surface of the drum and peeling it off. Copper can also be electrolytically deposited on the surface of the above-mentioned rolled copper foil. Roughening treatment or surface treatment (for example, chromate treatment with a thickness of about several nm to 1 μm, primer treatment such as Ti, etc.) may be performed on one or both sides of the copper foil.

(thickness)

Among current collector substrates made of copper foil or the like, thinner thin film negative electrodes can be produced, and a thin film negative electrode with a larger surface area can be packed in a battery container with the same storage volume, which is preferable. However, if If it is too thin, the strength will be insufficient, and the copper foil may be cut during winding and the like during battery production, so the thickness is preferably 10 to 70 μm. When the active material layers are formed on both sides of the copper foil, the copper foil is preferably thinner, but from the viewpoint of avoiding the generation of cracks caused by the expansion/contraction of the active material film accompanying charge and discharge, in this case , the more preferable thickness of copper foil is 8-35 micrometers. In addition, when metal foil other than copper foil is used as the current collector, a preferable thickness can be used according to various metal foils, but it is generally within a range of about 10 to 70 μm.

(physical properties)

The current collector substrate is also desired to have the following physical properties.

(1) Average surface roughness (Ra)

The average surface roughness (Ra) of the active material thin film formation surface of the current collector substrate specified by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.01 μm or more, preferably 0.03 μm or more, and usually 1.5 μm or more. μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less.

When the average surface roughness (Ra) of the current collector substrate is within the range between the above-mentioned lower limit and upper limit, good charge-discharge cycle characteristics can be expected. That is, by setting it as more than the said lower limit, the interface area with an active material thin film becomes large, and the adhesiveness with an active material thin film improves. In addition, the upper limit of the average surface roughness (Ra) is not particularly limited. If the average surface roughness (Ra) exceeds 1.5 μm, it is difficult to obtain a foil having an appropriate thickness as a battery, so it is preferably 1.5 μm or less.

(2) Tensile strength

The tensile strength of the current collector substrate is not particularly limited, but is usually 50 N/mm ² or more, preferably 100 N/mm ² or more, more preferably 150 N/mm ² or more. The term "tensile strength" refers to a value obtained by dividing the maximum tensile force required for a test piece to break by the cross-sectional area of the test piece. The tensile strength in the present invention can be measured using the same apparatus and method as for measuring elongation. A current collector substrate with high tensile strength can suppress cracking of the current collector substrate due to expansion/shrinkage of the active material film during charging/discharging, thereby obtaining good cycle characteristics.

(3) 0.2% Stamina

The 0.2% proof strength of the current collector substrate is not particularly limited, but is usually 30 N/mm ² or more, preferably 100 N/mm ² or more, particularly preferably 150 N/mm ² or more. The so-called 0.2% endurance refers to the load required to produce 0.2% plastic (permanent) deformation. After applying a load of this size, the load will also maintain 0.2% deformation. The 0.2% endurance in the present invention can be measured by the same apparatus and method as for measuring elongation. A current collector with a high 0.2% endurance can suppress plastic deformation of the current collector substrate due to expansion/shrinkage of the active material film during charging/discharging, thereby obtaining good cycle characteristics.

[Manufacturing method of negative electrode active material (C') containing multiple elements of negative electrode [7]]

The manufacturing method of the multi-element-containing negative electrode active material (C') of the present invention (lithium occlusion material (D') containing element Z and lithium occlusion material (F) external to element Z) is not particularly limited, for example, It can be produced by the production method listed below.

1. Manufacturing method of lithium storage substance (D') containing element Z

<Manufacturing method 1>

Evaporation source, sputtering source or sputtering source use any of the following substances:

时为Si和元素Z的组合物)；(i) Composition of Si, element Z and element M (wherein, y=0 or

When it is the combination of Si and element Z);

时为Si和元素Z的混合物)；(ii) a mixture of Si, element Z and element M (wherein, y=0 or

When it is a mixture of Si and element Z);

时为Si和元素Z各自的单质)；(iii) simple substances of Si, element Z and element M (each simple substance may also be a gas containing each element) (wherein, y=0 or

When Si and element Z are the respective simple substances);

(iv) The composition or mixture of Si and element Z and the simple substance of element M (may also be a gas containing M);

时为含有Si和元素Z的气体)；(v) gas containing Si, element Z and element M (wherein, y=0 or

When it is a gas containing Si and element Z);

(vi) Composition or mixture of Si simple substance, element Z and element M;

(vii) The composition or mixture of Si and element M and the simple substance of element Z (may also be a gas containing M),

And utilize vapor deposition method and/or sputtering method and sputtering method to form Si, element Z and element M (wherein, when y=0 or y≒0, be Si and element Z) on above-mentioned current collector substrate to form 1 A thickness of ˜30 μm, preferably a film having a thickness described in the section of film thickness of the active material thin film.

(raw material)

As an Si elemental raw material for a vapor deposition source, a sputtering source, or a sputtering (spraying) source (hereinafter, sometimes appropriately referred to as "raw material"), for example, crystalline Si, amorphous Si, or the like can be used. As the Z raw material, C and N elements can be used. In addition, as long as the element Z satisfies the above items, two or more kinds of elements may be used in combination.

Among the raw materials, as (i) a composition of Si, element Z, and element M (wherein, when y=0 or y≒0, it is a composition of Si and element Z), a combination of Si, element Z, and element M can be used, Or a single compound formed by combining Si and element Z, or a plurality of compounds may be used. In addition, these Si, Z raw materials, and M raw materials can be used in the form of powder, granule, pellet, block, plate, etc., for example.

In the general formula SiZ _x M _y , when y ≠ 0 and contains element M, the element M can be selected from group 2, group 4, group 8, group 9, group 10, group 11, One or two or more elements of Group 13, Group 14, Group 15, and Group 16 are preferably Ti, Zr, W, O, and Co elements, more preferably O elements.

(film forming method)

As a method for forming an active material thin film, a vapor phase film-forming method can be mentioned, and specifically, an evaporation method (vacuum evaporation method, CVD method, ion plating method), a sputtering method, a thermal spraying method (flame spraying method, plasma coating method) can be mentioned. body spraying method), etc. It is also possible to form a film by combining a sputtering method and a vapor deposition method, or a sputtering method and a thermal spraying method.

Next, a method for forming the negative electrode active material thin film will be described.

A. Sputtering method

In the sputtering method, a thin film is formed by colliding and depositing an active material emitted from a target containing the above-mentioned raw material and a current collector substrate by using plasma under reduced pressure. According to the sputtering method, the interface state between the formed active material thin film and the current collector substrate is good, and the adhesiveness of the active material thin film to the current collector is also high.

As a method of applying the sputtering voltage to the target, either a DC voltage or an AC voltage can be used. In this case, a negative bias voltage is substantially applied to the current collector substrate, and the collision energy of ions originating in the plasma can be reduced. Take control. The ultimate vacuum in the chamber before the start of film formation is usually 0.1 Pa or less to prevent contamination of impurities.

As the sputtering gas, inert gases such as Ne, Ar, Kr, and Xe are used. Among these, argon gas is preferably used from the viewpoint of sputtering efficiency and the like. In addition, when the element Z in the compound SiZ _x My _y is N, it is preferable in terms of production that a small amount of nitrogen gas coexists with the above-mentioned inert gas. Usually, the sputtering gas pressure is about 0.05 to 70 Pa. The temperature of the current collector substrate when the active material thin film is formed by the sputtering method can be controlled by water cooling or a heater. The temperature range of the current collector substrate is usually room temperature to 900°C, but is preferably 150°C or lower. The film forming rate when forming the active material thin film by the sputtering method is usually 0.01 to 0.5 μm/min.

Furthermore, before forming the active material thin film, the surface of the current collector substrate may be etched by pretreatment such as reverse sputtering or other plasma treatment. Such pretreatment is effective for removing contaminants and oxide films on the surface of the copper foil serving as a current collector substrate, and for improving the adhesion of the active material thin film.

B. Vacuum evaporation method

The vacuum evaporation method is a method of melting and evaporating the above-mentioned raw materials as active materials, and depositing them on the current collector substrate. Generally speaking, this method has the advantage of forming a thin film at a higher film formation rate than the sputtering method. advantage. From the viewpoint of shortening the time required to form an active material thin film having a predetermined film thickness, the vacuum vapor deposition method can be advantageously utilized in terms of production cost compared with the sputtering method. Specific methods thereof include an induction heating method, a resistance heating method, an electron beam heating vapor deposition method, and the like. The induction heating method is to heat and melt the evaporation material and evaporate it to form a film through an induction current in an evaporation crucible such as graphite; the resistance heating method is to heat and melt the evaporation material in an evaporation boat or the like through a heating current that is energized. and evaporated to form a film; electron beam heating evaporation is to heat, melt and evaporate the evaporation material to form a film through an electron beam.

As the atmosphere of the vacuum evaporation method, vacuum is generally used. In addition, when the element Z in the compound SiZ _x My _y is N, a trace amount of nitrogen gas can be introduced together with an inert gas and the pressure can be reduced to simultaneously form SiZ _x My _y under vacuum. The ultimate vacuum in the chamber before the start of film formation is usually 0.1 Pa or less to prevent contamination of impurities.

The temperature of the current collector substrate when the active material thin film is formed by the vacuum evaporation method can be controlled by a heater or the like. The temperature range of the current collector substrate is usually room temperature to 900°C, but is preferably 150°C or lower. The film formation rate when forming the negative electrode active material thin film by the vacuum deposition method is usually 0.1 to 50 μm/min.

In addition, as in the case of the sputtering method, before depositing the active material thin film on the current collector substrate, the surface of the current collector substrate can be etched by ion irradiation with an ion gun or the like. Such etching can further improve the adhesion between the substrate and the active material thin film. In addition, when the thin film is formed, the adhesion of the active material thin film to the current collector substrate can be further improved by causing ions to collide with the current collector substrate.

C. CVD method

In the CVD method, the above-mentioned raw materials as active materials are deposited on the current collector substrate by a gas-phase chemical reaction. In general, the CVD method is characterized by the fact that various materials can be synthesized with high purity because the compound gas in the reaction chamber is controlled by the gas inflow. Specific methods include thermal CVD, plasma CVD, optical CVD method, cat-CVD method, etc. The thermal CVD method is to introduce the raw material gas of the halogen compound with high vapor pressure into the heated reaction vessel at about 1000°C together with the carrier gas or reaction gas, and make it produce a thermochemical reaction to form a thin film. Plasma CVD is a method of using plasma instead of thermal energy; photo CVD is a method of using light energy instead of thermal energy. The cat-CVD method is a catalytic chemical vapor deposition method that forms a thin film by applying a contact decomposition reaction of a raw material gas and a heated catalyst.

Among the raw material gases used in the CVD method, the source of element Si is SiH ₄ , SiCl ₄ , etc.; the source of element Z is NH ₃ , N ₂ , BCl ₃ , CH ₄ , C ₂ H ₆ , C ₃ H ₈ , etc.

D. Ion plating method

In the ion plating method, the above-mentioned raw material as an active material is melted and evaporated, and evaporated particles are ionized and excited under plasma, whereby a film is firmly formed on the current collector substrate. Specifically, methods for melting and evaporating raw materials include induction heating, resistance heating, and electron beam heating evaporation; methods for ionizing and exciting include activation reaction evaporation, poly Cathodic thermionic irradiation method, high-frequency excitation method, HCD method, ion beam method (klasta-ionbiim method), multi-arc method, etc. In addition, the method of evaporating the above-mentioned raw materials and the method of ionization and excitation can be appropriately selected and combined.

E. Sputtering method

In the sputtering method, the above-mentioned raw material as an active material is melted or softened by heating to form fine particles and accelerated, so that the particles are solidified and deposited on the current collector substrate. Specific methods thereof include a flame spraying method, an arc spraying method, a DC plasma spraying method, an RF plasma spraying method, a laser spraying method, and the like.

F. Combination of sputtering method and evaporation method

Utilizing the advantages of high film-forming speed of the vapor deposition method and the strong film-forming adhesion to the current collector substrate of the sputtering method, for example, the first thin film layer is formed by the sputtering method and then formed at a high speed by the vapor deposition method The second thin film layer can thereby form an interface region with excellent adhesion with the current collector substrate, and at the same time form an active material thin film at a high film formation rate. A thin-film negative electrode having a high charge-discharge capacity and excellent charge-discharge cycle characteristics can be efficiently produced by such a mixed combination method of film-forming methods.

The combination of sputtering and vapor deposition to form an active material thin film is preferably performed continuously while maintaining a reduced pressure atmosphere. This is because contamination of impurities can be prevented by continuously forming the first thin film layer and the second thin film layer without exposing them to the atmosphere. For example, it is preferable to use a thin film forming apparatus that sequentially performs sputtering and vapor deposition while moving the current collector substrate in the same vacuum environment.

In the present invention, when the active material thin film is formed on both sides of the current collector substrate by such a film-forming method, the active material thin film layer (may also be the above-mentioned first thin film layer and second thin film layer) is formed on one side of the current collector substrate. Combination of thin film layers) and forming an active material thin film layer (also can be the combination of the first thin film layer and the second thin film layer) on the other side of the current collector substrate, preferably continuously under the state of maintaining a reduced pressure atmosphere .

<Manufacturing method 2>

The production method when the element Z in the general formula SiZ _x M _y is C will be described below.

Evaporation sources, sputter sources or sputter sources use any of the following:

(i) the composition of Si, C and element M (wherein, when y=0 or y≒0, it is the composition of Si and C);

(ii) A mixture of Si, C and element M (wherein, when y=0 or y≒0, it is a mixture of Si and C);

(iii) simple substances of Si, C and element M (wherein, when y=0 or y≒0, they are simple substances of Si and C);

(iv) The composition or mixture of Si and C and the simple substance of element M (may also be a gas containing M);

(v) Gas containing Si, C and element M (wherein, when y=0 or y≒0, it is a gas containing Si and C);

(vi) Composition or mixture of Si elemental substance and C and element M;

(vii) Compositions or mixtures of Si and element M with C alone,

And utilize vapor deposition method and/or sputtering method and sputtering method to form Si, C and element M (wherein, when y=0 or y≒0, be Si and C) on above-mentioned current collector substrate and form 1～30 μm The thickness is preferably a film with the thickness described in the item of film thickness of the active material thin film.

(raw material)

As a Si raw material for a vapor deposition source or a sputtering source (hereinafter sometimes referred to as "raw material"), for example, crystalline Si, amorphous Si, or the like can be used. As the C raw material, for example, carbon materials such as natural graphite and artificial graphite can be used. As the M raw material, it is usually an element of Group 2, Group 4, Group 8, Group 9, Group 10, Group 11, Group 13, Group 14, Group 15, and Group 16 of the periodic table other than Si and the element Z. Preferably, Ti, Among Zr, W, O, and Co elements, O element is particularly preferably used.

Among the raw materials, as the composition of (i) Si, C, and element M, a single compound obtained by combining Si, C, and element M may be used, or a plurality of compounds may be used. In addition, the forms of these Si, C, and M raw materials can be used in, for example, powder, granule, pellet, block, plate, and the like. In addition, the element M can be used as a nitride of Si or C, or an oxide of Si or C. For O, etc. that exist as a gas at room temperature, it is preferable to coexist as a raw material gas O, etc. in Si and C film formation. of.

(film forming method)

The same film-forming method as that of Production Method 1 above was used.

A. Sputtering method

As the sputtering gas, inert gases such as Ne, Ar, Kr, and Xe are used. Among these, argon gas is preferably used from the viewpoint of sputtering efficiency and the like. In addition, when the M element in the general formula SiC _x My _y is O, it is preferable in terms of production to coexist a small amount of oxygen in each of the above inert gases. Usually, the sputtering gas pressure is about 0.05 to 70 Pa.

B. Vacuum evaporation method

As the atmosphere of the vacuum evaporation method, vacuum is generally used. In addition, when the element M in the general formula SiC _x M _y is O, a small amount of oxygen can be introduced together with an inert gas, and the pressure can be reduced simultaneously, thereby simultaneously forming Si/C/M under vacuum.

C. CVD method

Among the raw material gases used in the CVD method, SiH ₄ , SiCl ₄ , etc. are used as the elemental Si source; CH ₄ , C ₂ H ₆ , C ₃ H ₈ , etc. are used as the elemental C source.

<Manufacturing method 3>

Next, the production method when the element Z is C and the element M is O in the general formula SiZ _x M _y will be described.

Evaporation sources, sputter sources or sputter sources use any of the following:

(1) the composition of Si and C;

(II) a mixture of Si and C;

(III) the respective simple substances of Si and C,

or

(IV) gases containing Si and C,

In an atmosphere where the oxygen concentration in the film-forming gas (in the residual gas during film formation in vacuum) is 0.0001 to 0.125%, Si and C are deposited simultaneously by vapor deposition and/or sputtering and sputtering A film having a thickness of 1 to 30 μm, preferably the thickness described in the section of film thickness of the active material thin film, is formed on the above-mentioned current collector substrate.

(raw material)

As a Si raw material of a vapor deposition source, a sputtering source, or a thermal spraying source of a raw material, for example, crystalline Si, amorphous Si, or the like can be used. As the C raw material, for example, carbon materials such as natural graphite and artificial graphite can be used. As oxygen in the film-forming gas, a gas containing an O element such as oxygen is used alone or in combination with an inert gas. The forms of these Si and C raw materials can be used in powder form, granule form, pellet form, block form, plate form, etc., for example. In addition, oxygen is preferable as a raw material gas in the coexistence production of Si and C film formation.

(film forming method)

The same film-forming method as that of Production Method 1 above was used.

(Oxygen concentration during film formation)

The oxygen concentration in the film-forming gas (residual gas during film-forming in vacuum) during vapor deposition and/or sputtering and sputtering is usually 0.0001% or more, and usually 0.125% or less, preferably 0.100% or less, More preferably, it is 0.020% or less. If the oxygen concentration contained in the film-forming gas exceeds this range, the amount of element O in the Si/C/O thin film will increase, and the reactivity with the non-aqueous electrolyte will increase, which may lead to a decrease in charge and discharge efficiency. If the oxygen concentration is too low, the Si/C/O thin film may not be formed.

Furthermore, the oxygen concentration in the film-forming gas can be obtained, for example, by analyzing the mass spectrum of the film-forming gas using a quadrupole filter. In addition, when argon gas coexisting with oxygen gas is used as the film-forming gas, it can be obtained by measuring the argon gas with an oxygen analyzer.

<Manufacturing method 4>

The production method when the element Z in the general formula SiZ _x M _y is N and y=0 or y≒0 will be described below.

Evaporation sources, sputter sources or sputter sources use any of the following:

(1) Si simple substance;

(II) compositions containing Si;

(III) mixtures containing Si,

or

(IV) Si-containing gas,

In the atmosphere where the nitrogen concentration in the film-forming gas (in the residual gas when forming a film in vacuum) is 1 to 22%, Si and N are simultaneously deposited by evaporation and/or sputtering and sputtering. A film having a thickness of 1 to 30 μm, preferably the thickness described in the section of film thickness of the active material thin film, is formed on the above-mentioned current collector substrate.

(raw material)

As a raw material of Si simple substance as a vapor deposition source, a sputtering source, or a thermal spraying source of a raw material, for example, crystalline Si, amorphous Si, or the like can be used. As N in the film-forming gas, a gas containing an N element such as nitrogen is used alone or in combination with an inert gas. The form of these Si etc. can be used, for example in a powder form, a granular form, a pellet form, a lump form, a plate form, etc. In addition, nitrogen gas is preferable as a raw material gas in the coexistence production of Si film formation.

(film forming method)

The same film-forming method as that of Production Method 1 above was used.

(Nitrogen concentration during film formation)

The nitrogen concentration in the film-forming gas (residual gas during film-forming in vacuum) during vapor deposition and/or sputtering and sputtering is usually 1% or more, and usually 22% or less, preferably 15% or less, More preferably, it is 10% or less. If the nitrogen concentration contained in the film-forming gas exceeds this range, the amount of element N in the _SiNx thin film will increase, and silicon nitride that does not participate in charge and discharge will be generated, resulting in a decrease in discharge capacity in some cases. If the nitrogen concentration is too low, the SiN _x thin film containing N may not be formed, resulting in degradation of cycle characteristics. In addition, the nitrogen concentration in the film-forming gas can be obtained, for example, by analyzing the mass spectrum of the film-forming gas using a quadrupole mass filter.

2. Preparation method of element Z external lithium occlusion substance (F)

<Manufacturing method 5>

Mix the lithium storage metal (A') and/or the lithium storage alloy (B') with the carbonizable organic matter described in the composition item of the carbonaceous substance (E'), heat and decompose the organic matter, and solidify phase and/or liquid phase and/or gas phase to carbonize to form a carbonaceous substance (E') to obtain a composite. The particles are then pulverized and classified so that the volume-based average particle diameter becomes an appropriate value.

(raw material)

The volume-based average particle diameter of the lithium storage metal (A') and/or lithium storage alloy (B') as a raw material is usually 100 μm or less, preferably 10 μm or less, more preferably 1 μm or less, and the lower limit is 1 nm or more. scope. If the upper limit is exceeded, it will be difficult to relax swelling during charging, and the cycle retention may decrease. Moreover, if it is less than the lower limit, pulverization becomes difficult, and time and economic loss may be caused. In addition, although the raw material of the carbonaceous substance (E') is as described above, it is preferably a substance that passes through a liquid phase during carbonization.

<Manufacturing method 6>

mixing the lithium storage metal (A') and/or the lithium storage alloy (B') with the graphite (G), and then mixing the carbonizable organic matter described in the composition item of the carbonaceous material (E'), and The organic matter is heated, decomposed, and carbonized in the liquid phase to form a carbonaceous substance (E') to obtain a composite. The particles are then pulverized and classified so that the volume-based average particle diameter becomes an appropriate value.

(raw material)

The raw materials are the same as in <Manufacturing method 5>.

<Manufacturing method 7>

mixing the lithium storage metal (A') and/or the lithium storage alloy (B') with the graphite (G), and then mixing the carbonizable organic matter described in the composition item of the carbonaceous material (E'), and The organic matter is heated and decomposed, and carbonized in the solid phase, and the carbonaceous substance (E') is formed through the phase, and a composite is obtained. The particles are further pulverized and classified so that the volume-based average particle diameter becomes an appropriate value.

(raw material)

The raw materials are the same as in <Manufacturing method 5>.

<Manufacturing method 8>

mixing the lithium storage metal (A') and/or the lithium storage alloy (B') with the graphite (G), and then mixing the carbonizable organic matter described in the composition item of the carbonaceous material (E'), and Organic matter is heated and decomposed, carbonized in the gas phase, and carbonaceous substance (E') is formed through the gas phase to obtain a composite. The particles are further pulverized and classified so that the volume-based average particle diameter becomes an appropriate value.

(raw material)

The raw materials are the same as in <Manufacturing method 5>.

[Electric Polarization of Powdered Active Material of Negative Electrode [7]]

The manufacture of negative pole can be carried out according to conventional method, for example, as mentioned above, can be made into slurry by adding binding agent, solvent in negative pole active material, adding thickener, conductive material, filling material etc. as required, its It is formed by pressing after coating and drying on the current collector. The thickness of the negative electrode active material layer on each side in the stage before the electrolyte solution injection step of the battery is usually 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and its upper limit is 150 μm or less, preferably 120 μm or less, more preferably Below 100μm. If it exceeds this range, since the nonaqueous electrolyte solution becomes difficult to permeate to the vicinity of the current collector interface, the high current density charge and discharge characteristics may be deteriorated. In addition, if it is less than this range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease. In addition, the negative electrode active material may be formed into a sheet electrode by roll molding, or a granular electrode may be formed by compression molding.

Usable binders, thickeners, and the like are the same as above.

<negative pole[8]>

Next, the negative electrode [8] containing two or more negative electrode active materials having different properties as the negative electrode active material used in the lithium secondary battery of the present invention will be described.

[Negative electrode active material of negative electrode [8]]

Next, the negative electrode active material used in the negative electrode [8] will be described.

The negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention is characterized by containing two or more negative electrode active materials having different properties.

The "different properties" mentioned here not only refer to X-ray diffraction parameters, median particle size, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circular Shape, ash content, etc. are different in powder shape and powder physical properties, and also include "composite carbonaceous substances containing two or more carbonaceous substances with different crystallinity", "composite carbonaceous substances containing two or more carbonaceous substances with different orientations" The composition of materials such as "hetero-oriented carbon composites" is different, or the processing treatments such as "heat treatment of the negative electrode active material" and "mechanical energy treatment of the negative electrode active material" are different.

[differences such as shape, physical properties]

Wherein, the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention can maintain the low temperature output power by containing more than two kinds of negative electrode active materials with different volume-based average particle diameters (median particle diameters), and at the same time Cycle characteristics can be improved. The difference in volume-based average particle diameter (median particle diameter) is usually 1 μm or more, preferably 2 μm or more, more preferably 5 μm or more. The upper limit is usually 30 μm or less, preferably 25 μm or less. If it exceeds this range, the particle diameter with a large median diameter tends to be too large, and therefore problems such as stringing of the coated surface may occur during electrode production. On the other hand, if it is less than this range, it may be difficult to express the effect of mixing two kinds of negative electrode active materials.

In addition, for the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention, for the same reason as above, a material with a non-uniform volume-based particle size distribution can also exhibit good characteristics. The so-called "uneven volume-based particle size distribution" refers to the volume-based particle size distribution when the horizontal axis is a logarithmic scale. When the volume-based average particle size (median particle size) is the center, it does not form left-right symmetry. The Z value represented by the following formula (1) is usually 0.3 μm or more, preferably 0.5 μm or more, and more preferably 1 μm or more. If Z is lower than this value, it may be difficult to obtain the effect of improving cycle characteristics due to uneven particle size distribution.

Z＝|(mode diameter)-(median particle diameter)| (1)

In formula (1), the unit of mode diameter and median particle diameter is "μm", and "||" represents an absolute value.

In the present invention, the volume-based average particle diameter (median particle diameter) and the modulus diameter are defined as the following values: the negative electrode active material is dispersed in polyoxyethylene (20) sorbitan monolaurate as a surfactant The value measured using the laser diffraction particle size distribution meter (LA-700 by Horiba Co., Ltd.) in 0.2 mass % aqueous solution (about 1 mL). "Median particle size" is usually also called d ₅₀ , which refers to the particle size when the powder is divided into two parts by a certain particle size under the volume basis, when the larger side and the smaller side are equal, and the "mode size" Refers to the particle size that represents the maximum value of the distribution in the volume-based particle size distribution, and any one of them is called "median particle size" and "mode size" in LA-700 manufactured by Horiba Co., Ltd. value, respectively, on the device.

In addition, it is preferable to use a negative electrode active material having a median particle size of 10 μm or less as at least one of the negative electrode active materials, since it is possible to maintain the low-temperature output and obtain an effect of improving cycle characteristics. Particularly preferably, it is 8 μm or less. The negative electrode active material having a median diameter of 10 μm or less is particularly preferably used in an amount of 0.5 to 10% by mass relative to the entire negative electrode active material.

In addition, the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention can maintain cycle by containing two or more negative electrode active materials with different Raman R values measured by argon ion laser Raman spectroscopy. characteristics, while improving low temperature output power. The difference in Raman R value is usually 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more, and the upper limit is usually 1.4 or less, preferably 1.3 or less, more preferably 1.2 or less. If it is less than this range, it may be difficult to obtain the effect due to the difference in Raman R value. On the other hand, if it exceeds this range, the irreversible capacity may increase due to a portion with a high Raman R value.

In the present invention, the measurement of the Raman spectrum is carried out as follows: using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped into the measurement container, the sample is filled, and the measurement process Yes, the sample surface in the container is irradiated with an argon ion laser while rotating the container in a plane perpendicular to the laser beam. For the obtained Raman spectrum, measure the intensity I _A of the peak PA at 1580 cm ^-1 and the intensity I _B of the peak P _B at 1360 cm ^-1 , calculate the _intensity ratio R (R= _IB / _IA ), and define it as is the Raman R value of the graphitic carbon particle. In addition, the half-value width of the peak _PA at 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the graphitic carbon particles.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

Raman R value, half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

In addition, the negative electrode active material used as the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of ^the present invention has a Raman half-value width of 1580 ^cm It is preferably 15 cm ^-1 or more, and the upper limit thereof is usually 150 cm ^-1 or less, preferably 140 cm ^-1 or less. If the Raman half-value width is below this range, the crystallinity of the particle surface is too high, and the low-temperature output may decrease. On the other hand, if it exceeds this range, the irreversible capacity may increase due to the decrease in the crystallinity of the particle surface.

In addition, even if the negative electrode active material used as the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention contains two or more negative electrode active materials with different crystallinity, the cycle characteristics can be maintained and the low temperature can be improved. Output Power. The term "crystallinity" here refers to a laminated structure such as the thickness and pitch of the repeating structure of the laminated body of carbon hexagonal network planes. The specific physical property values indicating the difference in crystallinity are not particularly limited, for example, interplanar spacing, crystallite size, etc., and these are preferably different among the two or more negative electrode active materials used in the lithium secondary battery of the present invention. When the difference in crystallinity is too small, it may be difficult to obtain the effect by mixing.

The negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention can maintain Cycle characteristics and improve low temperature output power. The difference between interplanar distances (d002) is usually at least 0.0005 nm, preferably at least 0.001 nm, more preferably at least 0.003 nm, and even more preferably at least 0.004 nm, and the upper limit thereof is usually at most 0.05 nm, preferably at most 0.04 nm, and more The range is preferably 0.03 nm or less, more preferably 0.02 nm or less. If it is less than this range, it may be difficult to obtain the effect due to the difference in crystallinity. On the other hand, if it exceeds this range, the irreversible capacity may increase due to the portion with low crystallinity. The interplanar spacing (d002) of the (002) plane measured by the wide-angle X-ray diffraction method mentioned in the present invention refers to the d value ( layer distance).

In addition, the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention can be obtained by containing two or more negative electrode active materials with different crystallite sizes (Lc) obtained by X-ray diffraction using the Gakushin method. Maintain cycle characteristics and increase low temperature output. The difference in crystallite size (Lc) obtained by X-ray diffraction by the Gakushin method is usually 1 nm or more, preferably 10 nm or more, more preferably 50 nm or more. If it is less than this range, it may be difficult to obtain the effect due to the difference in crystallite size.

In addition, the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention can maintain cycle characteristics and improve low-temperature output power by containing two or more negative electrode active materials with different true densities. The difference in true density is usually 0.03 g/cm ³ or more, preferably 0.05 g/cm ³ or more, more preferably 0.1 g/cm ³ or more, still more preferably 0.2 g/cm ³ or more, and the upper limit is usually 0.7 g /cm ³ or less, preferably 0.5 g/cm ³ or less, more preferably 0.4 g/cm ³ or less. If it is less than this range, it may be difficult to obtain the effect due to the difference in true density. On the other hand, if this range is exceeded, the irreversible capacity may increase due to the low true density portion.

The true density referred to in the present invention is defined as a value measured by a liquid-phase displacement method (hydrometer method) using butanol.

In addition, when the negative electrode active material used in the present invention contains two or more negative electrode active materials having different circularities, it is possible to maintain low-temperature output and improve cycle characteristics. The difference in circularity is usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, and the upper limit is usually 0.3 or less, preferably 0.2 or less, more preferably 0.1 or less. If it is less than this range, it may be difficult to obtain the effect due to the difference in circularity. On the other hand, if it exceeds this range, problems such as stringing may occur at the time of electric polarization due to the portion with low circularity.

The circularity referred to in the present invention is defined by the following formula.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the value measured as follows is used: using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) sorbitol as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50mL) of sugar-alcohol monolaurate with an output of 60W for 1 minute at 28kHz ultrasonic waves, specify a detection range of 0.6-400μm, and measure particles with a particle diameter of 3-40μm .

In addition, the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention can maintain low-temperature output and improve cycle characteristics by containing two or more negative electrode active materials with different tap densities. The tap density difference is usually at least 0.1 g/cm ³ , preferably at least 0.2 g/cm ³ , and more preferably at least 0.3 g/cm ³ . If it is less than this range, it may be difficult to obtain the effect of mixing materials with different tap densities.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm, the sample is dropped into a ²⁰ cm container for vibration, and after the sample is filled with the upper end of the container, a powder density measuring device (such as , Tap densor manufactured by Seishin Enterprise Co., Ltd.), vibration with a stroke length of 10 mm was performed 1000 times, and the density was calculated from the volume at this time and the weight of the sample, and this value was taken as the tap density.

In addition, the negative electrode active material used in the negative electrode [8] of the lithium secondary battery of the present invention contains two or more negative electrode active materials with different BET specific surface areas, so that the cycle characteristics can be maintained and the low-temperature output can be improved. The difference in BET specific surface area is usually 0.1 m ² /g or more, preferably 0.5 m ² /g or more, more preferably 1 m ² /g or more, and the upper limit is usually 20 m ² /g or less, preferably 15 m ² /g It is not more than 12 m ² /g, and more preferably not more than 12 m 2 /g. If it is less than this range, it may be difficult to obtain the effect by mixing materials with different BET specific surface areas. On the other hand, if this range is exceeded, the irreversible capacity may increase due to the portion with a large BET specific surface area.

In the present invention, the BET specific surface area is defined as a value as follows: Using a surface area meter (automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then adjusted using It is a value measured by the nitrogen adsorption BET 1-point method using a gas flow method for a nitrogen-helium mixed gas whose relative pressure value of nitrogen to atmospheric pressure is 0.3.

As the mixing ratio of two or more different negative electrode active materials used in the negative electrode [8] of the lithium secondary battery of the present invention, the ratio of one negative electrode active material to the total amount is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and the upper limit thereof is usually 99.9% by mass or less, preferably 99% by mass or less, more preferably 90% by mass or less, still more preferably 80% by mass % below the range. If it is outside this range, it may be difficult to obtain the effect by containing two or more different negative electrode active materials.

In addition, natural graphite and/or a processed product of natural graphite are contained in at least one of the two different negative electrode active materials, which is preferable from the standpoint of high cost performance.

According to its properties, natural graphite is classified into flake graphite (Flake Graphite), scaly graphite (Crystalline (Vein) Graphite), soil graphite (Amorphous Graphite) (see "Powder Granular Process Technology Integration", ((Co., Ltd.) Industry Technology Center, Graphite Item, issued in Showa 49); and "HANDBOOK OF CARBON, GRAPHITE, DIAMOND AND FULLERENES", (issued by NoyesPublications)). The degree of graphitization is highest in flake graphite, which is 100%, followed by flake graphite, which is 99.9%, while soil graphite is as low as 28%. Flake graphite as natural graphite is produced in Madagascar, China, Brazil, Ukraine, Canada, etc.; flake graphite is mainly produced in Sri Lanka. The main producing areas of soil graphite are the Korean Peninsula, China, Mexico, etc. Among these natural graphites, soil graphite generally has a small particle size and low purity. On the contrary, flaky graphite and flaky graphite can be preferably used in the present invention because of their advantages of high degree of graphitization and low amount of impurities.

[difference in the negative electrode [8] handling]

The negative electrode active material used in the present invention can maintain cycle characteristics and improve low-temperature output by containing two or more different processed negative electrode active materials. Examples of the processing method of natural graphite include a method of applying heat treatment, a method of applying mechanical energy treatment, and the like. An example of heat treatment is described below.

[[heat treatment temperature]]

The heat treatment temperature of the negative electrode active material is usually 600°C or higher, preferably 1200°C or higher, more preferably 2000°C or higher, further preferably 2500°C or higher, particularly preferably 2800°C or higher. The upper limit is usually 3200°C or lower, preferably 3100°C or lower. If the temperature condition is lower than this range, the crystallization restoration of the surface of the natural graphite particles may be insufficient. On the other hand, when it exceeds the said range, the amount of sublimation of graphite may increase easily. The negative electrode active material used in the present invention preferably contains two or more negative electrode active materials having different heat treatment temperatures.

[[Heat treatment method]]

Heat treatment is achieved by passing through the above temperature range once. The holding time for keeping the temperature condition within the above range is not particularly limited, but is usually longer than 10 seconds and not more than 168 hours.

The heat treatment is usually carried out in an inert gas atmosphere such as nitrogen gas or a non-oxidizing atmosphere formed by gas generated from natural graphite as a raw material. However, for furnaces of the type embedded in pulverized coal (fine pitch-sintered carbon), the atmosphere is sometimes mixed initially. In this case, it is not necessary to completely inert gas atmosphere. The apparatus used for the heat treatment is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, a coke roasting furnace, a rotary furnace, a direct electric furnace, an Acheson electric furnace, a resistance heating furnace, an induction heating furnace, etc. can be used. The negative electrode active material used in the present invention preferably contains two or more negative electrode active materials having different heat treatment methods.

In addition, various processing such as classification processing may be performed in addition to the processing described above. Classification treatment is performed to obtain the target particle size and remove coarse powder and fine powder. As the device used in the classification process, there is no particular limitation. For example, in the case of dry sieving, rotary sieves, shaking sieves, rotary sieves, vibrating sieves, etc. can be used; in the case of dry airflow classification In the case of wet sieving, gravity classifiers, inertial force classifiers, centrifugal force classifiers (classifiers, cyclone separators), etc. can be used; in the case of wet sieving, mechanical wet classifiers, hydraulic classifiers, Sedimentation classifier, centrifugal wet classifier, etc. Grading treatment can be carried out before heat treatment, and can also be carried out at other times, such as after heat treatment. Furthermore, the classification process itself can also be omitted. The negative electrode active material used in the present invention preferably contains two or more negative electrode active materials with different classification treatment conditions.

The negative electrode active material used in the present invention can maintain cycle characteristics and improve low-temperature output by containing two or more negative electrode active materials different in mechanical energy treatment described later. An example of mechanical energy processing is described below.

[[Mechanical Energy Processing]]

The mechanical energy treatment is performed so that the volume average particle diameter ratio before and after the treatment becomes 1 or less. The "volume average particle diameter ratio before and after treatment" is a value obtained by dividing the volume average particle diameter after treatment by the volume average particle diameter before treatment. In the present invention, it is preferable that the kinetic energy treatment performed to produce the raw material before the heat treatment is such that the average particle diameter ratio before and after the treatment is 1 or less. The mechanical energy treatment is a treatment performed to reduce the particle size so that the average particle diameter ratio before and after the powder particle treatment is 1 or less, and at the same time control the particle shape. Among engineering unit operations that can be effectively utilized in particle design, such as pulverization, classification, mixing, granulation, surface modification, and reaction, mechanical energy processing belongs to pulverization processing.

The so-called pulverization refers to applying force to a substance to reduce its size to adjust the particle size, particle size distribution, and filling properties of the substance. Pulverization treatment is classified according to the type of force applied to the substance and the form of treatment. The force exerted on the substance is roughly divided into the following four types: (1) knocking force (impact force), (2) crushing force (compression force), (3) grinding force (grinding force), (4) scraping force force (shear force). On the other hand, processing forms are roughly classified into two types: volume crushing in which cracks are generated inside the particles and propagated, and surface crushing in which the particle surfaces are cut off. Volume crushing can be carried out by impact force, compression force and shear force; surface crushing can be carried out by grinding force and shear force. Pulverization is a process of various combinations of the type of force applied to these substances and the form of treatment. The combination thereof can be appropriately determined according to the purpose of treatment.

Pulverization may be performed using a chemical reaction such as blasting or volume expansion, but it is usually performed using a mechanical device such as a pulverizer. The pulverization treatment used in the production of the spheroidized carbon as the raw material of the present invention is preferably a treatment in which the ratio of the final surface treatment increases, regardless of the presence or absence of volume pulverization. This is because it is important to remove the pulverized corners of the particle surface so that the particle shape becomes circular. Specifically, the surface treatment may be performed after a certain volume pulverization is performed, only the surface treatment may be performed without volume pulverization, or the volume pulverization and surface treatment may be performed simultaneously. It is preferable to perform surface crushing at the end to remove corners from the surface of the particles. When the negative electrode active material used in the present invention contains two or more negative electrode active materials having different degrees of surface treatment, cycle characteristics can be maintained and low-temperature output can be improved.

The device for mechanical energy processing is selected from devices capable of performing the above-mentioned preferable processing. Mechanical energy processing can be achieved by using more than one of the four types of force applied to the above-mentioned substances, but it is preferably based on impact force, and repeatedly applies compression, friction, shearing, including particle interaction, to the particles. Mechanical effects such as shear force. Therefore, specifically, a device that has a rotor provided with a plurality of blades inside the tank and that imparts mechanical forces such as impact compression, friction, and shearing force to the carbon material introduced into the inside by rotating the rotor at high speed is preferable. function, thereby carrying out surface treatment while performing volume crushing. In addition, a device having a mechanism for repeatedly imparting a mechanical action by circulating or convecting the carbonaceous material is more preferable.

As a preferable apparatus, a mixing system (manufactured by Nara Machinery Co., Ltd.), Kryptron (manufactured by Earth Technica Co., Ltd.), a CF mill (manufactured by Ube Industries, Ltd.), a mechanical fusion system (manufactured by Hosokawa Micron Co., Ltd.) and the like are exemplified. Among these, the mixing system manufactured by Nara Machinery Manufacturing Co., Ltd. is preferable. When using this apparatus for processing, the peripheral speed of the rotating rotor is preferably set at 30 to 100 m/sec, more preferably at 40 to 100 m/sec, and even more preferably at 50 to 100 m/sec. In addition, the treatment may be performed by merely passing the carbonaceous material, but it is preferably treated by circulating or staying in the device for 30 seconds or more, more preferably by circulating or staying in the device for 1 minute or more.

By performing the mechanical energy treatment in this way, the carbon particles become particles in which high crystallinity is maintained as a whole, but the vicinity of the surface of the particles becomes rough, and the edge surfaces are inclined and exposed. In this way, the surface where lithium ions can come and go increases, and it has a high capacity even at a high current density.

In general, the smaller the particle size of the scale-like, scale-like, and plate-like carbon materials tends to be, the worse the fillability is. This is considered to be due to the following reasons: as the particles become more amorphous by pulverization, or protrusions such as "burrs", "peeling" or "bends" generated on the particle surface increase, and some degree of deformation occurs on the particle surface. The strength is caused by the adhesion of finer amorphous particles, etc., so that the resistance between adjacent particles becomes larger, and the filling property is deteriorated. If the amorphousness of these particles is reduced and the particle shape is close to spherical, even if the particle size becomes smaller, the filling property will be reduced very little. In theory, both large particle size carbon powder and small particle size carbon powder should be Shows an equivalent degree of tap density.

The ratio of these natural graphite and/or processed products of natural graphite is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and the upper limit is usually 99.9% by mass. Mass % or less, Preferably it is 99 mass % or less, More preferably, it is 90 mass % or less, More preferably, it is 80 mass % or less. If it is less than this range, it may be difficult to improve the cost performance by adding natural graphite and/or a processed product of natural graphite. On the other hand, if it exceeds this range, it may be difficult to obtain the improvement of the effect by a different negative electrode active material.

[[pore volume, etc.]]

The pore volume of the negative electrode active material used as the negative electrode active material of the lithium secondary battery of the present invention is obtained by mercury porosimetry (mercury porosimetry) due to the voids in particles corresponding to a diameter of 0.01 μm to 1 μm. , The amount of unevenness on the surface of the particles (hereinafter referred to simply as "micropore volume") is usually more than 0.01mL/g, preferably more than 0.05mL/g, more preferably more than 0.1mL/g, the upper limit Usually it is 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder will be required to manufacture an electrode plate. If it is less than this range, the high current density charge-discharge characteristics will deteriorate, and the effect of alleviating electrode expansion and contraction during charge-discharge may not be obtained.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and its upper limit is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. If it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of a sample (negative electrode material) was weighed, sealed in a container for powder, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, the pressure is reduced to 4psia (about 28kPa), mercury is introduced, the pressure is raised from 4psia (about 28kPa) to 40000psia (about 280MPa) in steps, and then the pressure is lowered to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

[[ash]]

The ash content of the negative electrode active material of the lithium secondary battery of the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, based on the total mass of the graphitic carbon particles. In addition, the lower limit thereof is preferably 1 ppm or more. If the above-mentioned range is exceeded, the degradation of the battery performance due to the reaction with the non-aqueous electrolytic solution during charge and discharge cannot be ignored. On the other hand, if it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

[[Orientation Ratio]]

The orientation ratio of the graphitic carbon particles used as the negative electrode active material of the lithium secondary battery of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, the high-density charge and discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

· Slit: divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

[[Aspect Ratio]]

The aspect ratio of the graphitic carbon particles used as the negative electrode active material of the lithium secondary battery of the present invention is theoretically 1 or more, the upper limit is 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, the electrode plate may be threaded or a uniformly coated surface may not be obtained, and the high current density charge and discharge characteristics may deteriorate.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of a particle and the shortest diameter B perpendicular thereto in three-dimensional observation. Observation of particles is performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of the metal with a thickness of 50 microns or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

The lithium secondary battery having the negative electrode [8] of the present invention only needs to contain two or more negative electrode active materials having different properties, and the type of negative electrode active material is not particularly limited. However, for properties measured by X-ray diffraction such as interplanar spacing (d002), crystallite size (Lc), orientation ratio, and plate orientation ratio; Raman R value, Raman half-value width, etc. ; and ash content, since the above values are premised on carbonaceous substances, the difference between the above values applies to carbonaceous substances. On the other hand, for properties related to particle size distribution such as median particle size, modulus diameter, Z, etc.; BET specific surface area; micropore volume, total micropore volume, average micropore diameter, etc., measured by mercury porosity meter; true density ; circularity; tap density; and aspect ratio, the above-mentioned values are not limited to carbonaceous materials, but are applicable to all materials that can be used as negative electrode active materials, and the difference between the above-mentioned values is also applicable to all materials. However, it is preferable that the substance having the above two properties is a carbonaceous substance. In this case, the above numerical values are regarded as values representing properties of the carbonaceous material, and it is preferable to use two or more types of carbonaceous materials having different properties as the negative electrode active material.

[Mixing method of two or more negative electrode active materials of the negative electrode [8]]

When mixing two or more negative electrode active materials, the device used is not particularly limited, and examples include V-type mixers, W-type mixers, variable container mixers, kneaders, tumble mixers, shear mixers, etc. .

[Electrode manufacturing of negative electrode [8]]

The manufacture of the negative electrode [8] can be performed by a conventional method, and the negative electrode [8] can be formed in the same manner as above. The current collector, the thickness ratio of the current collector to the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

<Negative electrodes [9] and [10]>

Next, the negative electrode [9] (form A) and the negative electrode [10] (form B) used in the lithium secondary battery of the present invention will be described. The negative electrode [9] contains a tap density of 0.1 g/cm ³ or more, and Negative electrode active materials with a micropore volume of 0.01 mL/g or more corresponding to particles in the range of 0.01 μm to 1 μm in diameter measured by a mercury porosimeter; when the negative electrode [10] is charged to 60% of the nominal capacity of the negative electrode , The reaction resistance generated by the opposite battery of the negative electrode is 500Ω or less.

"Negative electrode [9] (mode A)"

Mode A of the present invention relates to a lithium secondary battery in which the physical properties of the negative electrode active material contained in the negative electrode used in the present invention are specified, and the lithium secondary battery includes a non-aqueous electrolytic solution and a negative electrode, the non-aqueous The aqueous electrolytic solution contains the above-mentioned specific compound, and the negative electrode contains a negative electrode active material having the following specific physical properties. Embodiment A of the present invention will be described below.

[Negative electrode active material of the negative electrode [9]]

The negative electrode active material in aspect A of the present invention can electrochemically occlude and release lithium ions, and also satisfies at least the following requirements (a) and (b).

(a) The tap density is above 0.1g/ ^cm3 ;

(b) The pore volume in the range of 0.01 μm to 1 μm measured by a mercury porosimeter is 0.01 mL/g or more.

[[Tap Density]]

The tap density of the negative electrode active material contained in the negative electrode [9] of the lithium secondary electrode of the present invention is preferably 0.1 g/cm ³ or more, more preferably 0.5 g/cm ³ or more, even more preferably 0.7 g/cm ³ or more , particularly preferably 0.9 g/cm ³ or more. In addition, the upper limit thereof is preferably 2 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, particularly preferably 1.6 g/cm ³ or less. If the tap density is lower than this range, especially the effect of high output cannot be achieved. On the other hand, if it exceeds this range, the gaps between the particles in the electrode will be too small, the flow path in the non-aqueous electrolyte solution will be reduced, and the output power itself may be reduced.

In the present invention, the tap density is defined as follows: the sample is passed through a sieve with an aperture of 300 μm, the sample is dropped into a ²⁰ cm container for vibration, and after the sample is filled with the upper end of the container, a powder density measuring device (such as , Tap densor manufactured by Seishin Enterprise Co., Ltd.) was vibrated 1000 times with a stroke length of 10 mm, and the density was calculated from the volume and weight at this time, and this value was taken as the tap density.

[[pore volume]]

The micropore volume of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is obtained by the mercury porosimeter (mercury intrusion method) because it is equivalent to the volume in particles with a diameter of 0.01 μm to 1 μm. The amount of voids and irregularities on the particle surface (hereinafter, simply referred to as "micropore volume") is 0.01 mL/g or more, preferably 0.05 mL/g or more, more preferably 0.1 mL/g or more, and the upper limit Usually it is 0.6 mL/g or less, preferably 0.4 mL/g or less, more preferably 0.3 mL/g or less. If it exceeds this range, a large amount of binder will be required to manufacture an electrode plate. On the other hand, if it is below this range, long life and high output cannot be realized.

In addition, the total pore volume is preferably 0.1 mL/g or more, more preferably 0.25 mL/g or more, and even more preferably 0.4 mL/g or more, and the upper limit thereof is usually 10 mL/g or less, preferably 5 mL/g or less, more preferably It is in the range of 2 mL/g or less. If it exceeds this range, a large amount of adhesive may be required to form a substrate. If it is less than this range, the dispersion effect of the thickener or the binder may not be obtained when forming an electrode plate. The "total pore volume" as used herein refers to the sum of the pore volumes measured in the entire range of the following measurement conditions.

In addition, the average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. If this range is exceeded, a large amount of adhesive is sometimes required. If it is less than this range, the high current density charge-discharge characteristics may deteriorate.

As an apparatus used for the mercury porosimeter, a mercury porosimeter (autopore9520; manufactured by Micrometrics Inc.) can be used. About 0.2 g of a sample (negative electrode material) was weighed, sealed in a container for powder, and degassed at room temperature under vacuum (50 μmHg or less) for 10 minutes to perform pretreatment. Next, the pressure is reduced to 4psia (about 28kPa), mercury is introduced, the pressure is raised from 4psia (about 28kPa) to 40000psia (about 280MPa) in steps, and then the pressure is lowered to 25psia (about 170kPa). The number of stages during the pressurization was 80 or more, and the amount of mercury intrusion was measured after an equilibration time of 10 seconds in each stage. The micropore distribution was calculated from the mercury intrusion curve thus obtained using the Washburn formula. In addition, the surface tension (γ) of mercury is 485 dyne/cm, and the contact angle (φ) is 140°. As the average pore diameter, the pore diameter at which the cumulative pore volume reaches 50% is used.

In the lithium secondary battery of mode A of the present invention, as long as the above-mentioned requirements (a) and (b) are satisfied for the negative electrode active material, the effect of the above-mentioned present invention can be exerted, and the performance can be fully exerted. Further, for the negative electrode active material, preferably simultaneously Satisfy any one or more of the following physical properties. In addition, it is particularly preferable for the negative electrode to simultaneously satisfy any one or more of the physical properties and structure of the negative electrode in Embodiment B described later.

[[BET specific surface area]]

The specific surface area of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention measured by the BET method is preferably 0.1 m ² /g or more, particularly preferably 0.7 m ² /g or more, more preferably 1 m ² /g or more, more preferably 1.5 m ² /g or more. The upper limit thereof is preferably 100 m ² /g or less, particularly preferably 50 m ² /g or less, more preferably 25 m ² /g or less, and still more preferably 15 m ² /g or less. If the value of the BET specific surface area is lower than the above range, when used as a negative electrode material, the acceptance of lithium at the time of charging will deteriorate, and lithium will be easily deposited on the electrode surface, and high output power may not be obtained. On the other hand, when it exceeds the above-mentioned range, when used as a negative electrode material, the reactivity with the electrolytic solution increases and gas generation increases, making it difficult to obtain a preferable battery in some cases.

The BET specific surface area is defined as a value measured as follows: Using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), the sample is pre-dried at 350° C. for 15 minutes under nitrogen flow, and then, using nitrogen gas relative to The relative pressure value of the atmospheric pressure is accurately adjusted to 0.3 nitrogen-helium mixed gas, and it is measured by the nitrogen adsorption BET 1-point method using the gas flow method.

[[Volume average particle size]]

The volume average particle size of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is defined as the average particle size (median particle size) based on the volume obtained by the laser diffraction/scattering method, preferably 1 μm Above, especially preferably 3 μm or more, more preferably 5 μm or more, even more preferably 7 μm or more. In addition, the upper limit thereof is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If it is less than the above-mentioned range, the irreversible capacity may increase, resulting in loss of initial battery capacity. Moreover, if it exceeds the said range, it will become easy to form an uneven coating surface at the time of making an electrode pad, and it may be unpreferable in a battery manufacturing process.

In the present invention, the volume-based average particle diameter is defined by a median particle diameter measured by dispersing carbon powder in polyoxyethylene (20) sorbitan as a surfactant. In a 0.2% by mass aqueous solution (about 1 mL) of monolaurate, it measures using a laser diffraction/scattering particle size distribution meter (for example, LA-700 manufactured by Horiba, Ltd.).

[[Circularity]]

The circularity of the negative electrode active material contained in the negative electrode [9] of the lithium secondary electrode of the present invention is usually 0.1 or more, preferably 0.5 or more, more preferably 0.8 or more, particularly preferably 0.85 or more, and more preferably 0.9 or more. As an upper limit, when the circularity is 1, a true sphere is theoretically formed. If the circularity is lower than this range, problems such as stringing may occur during electric polarization.

The circularity referred to in the present invention is defined by the following formula.

Circularity = (perimeter of an equivalent circle having the same area as the particle projected shape)/(actual perimeter of the particle projected shape)

As the value of circularity, the value measured as follows is used: using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is dispersed in polyoxyethylene (20) sorbitol as a surfactant. After irradiating a 0.2% by mass aqueous solution (approximately 50mL) of sugar-alcohol monolaurate with an output of 60W for 1 minute at 28kHz ultrasonic waves, specify a detection range of 0.6-400μm, and measure particles with a particle diameter of 3-40μm .

[[Space between faces (d002)]]

The interplanar distance (d002) of the (002) planes (d002) of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention measured by wide-angle X-ray diffraction method is usually 0.38nm or less, preferably 0.36nm or less, more preferably It is 0.35 nm or less, more preferably 0.345 nm or less, and its lower limit is 0.335 nm or more, the theoretical value of graphite. If it exceeds this range, the crystallinity is significantly lowered, and the irreversible capacity may increase.

The interplanar spacing (d002) of the (002) plane measured by the wide-angle X-ray diffraction method in the present invention refers to the d value (layer distance).

[[Crystalline Size (Lc)]]

In addition, the crystallite size (Lc) of the negative electrode active material obtained by X-ray diffraction by the Gakushin method is not particularly limited, but is usually 0.1 nm or more, preferably 0.5 nm or more, and more preferably 1 nm or more. If it is less than this range, the crystallinity will decrease remarkably, and the irreversible capacity may increase.

[[true density]]

The true density of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is generally 1.5 g/cm ³ or more, preferably 1.7 g/cm ³ or more, more preferably 1.8 g/cm ³ or more, and further It is preferably 1.85 g/cm ³ or more, and the upper limit thereof is 2.26 g/cm ³ or less. The upper limit is the theoretical value of graphite. If it is less than this range, the crystallinity of carbon may be too low, and the irreversible capacity may increase. In the present invention, the true density is defined as a value measured by a liquid phase displacement method (pycnometer method) using butanol.

[[Raman R value]]

The Raman R value of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more. The upper limit is preferably 1.5 or less, more preferably 1.2 or less, particularly preferably 0.5 or less. If the Raman R value is lower than this range, the crystallinity of the particle surface is too high, and the output power may decrease with the decrease of charge and discharge sites. On the other hand, if it exceeds this range, the crystallinity of the particle surface may decrease and the irreversible capacity may increase.

The measurement of the Raman spectrum is carried out as follows: Using a Raman spectrometer (such as a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped and filled in the measurement cell, and the surface of the sample in the cell is irradiated with an argon ion laser. At the same time, Rotate the cell in a plane perpendicular to the laser. For the obtained Raman spectrum, measure the intensity I _A of the peak PA at 1580 cm ^-1 and the intensity I _B of the peak P _B at 1360 cm ^-1 , calculate the _intensity ratio R (R= _IB / _IA ), and define it as is the Raman R value of the negative electrode active material. In addition, the half-value width of the peak _PA near 1580 cm ⁻¹ in the obtained Raman spectrum was measured, and this was defined as the Raman half-value width of the negative electrode active material.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~25mW

·Resolution: 10～20cm ^-1

· Measuring range: 1100cm ^-1 ~ 1730cm ^-1

Raman R value, Raman half-value width analysis: background processing

·Smooth processing: simple average, convolution 5 points

In addition, the Raman half-value width of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is not particularly limited at 1580 cm ^-1 , and is usually more than 10 cm ^-1 , preferably more than 15 cm ^-1 , and , the upper limit of which is usually 150 cm ^-1 or less, preferably 100 cm ^-1 or less, more preferably 60 cm ^{-1 or} less. If the Raman half-value width is below this range, the crystallinity of the surface of the particle is too high, and the output may decrease with the decrease of the charge and discharge sites. On the other hand, if it exceeds this range, the crystallinity of the particle surface may decrease, and the irreversible capacity may increase.

[[ash]]

The ash content of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less. In addition, the lower limit is preferably 1 ppm or more. If it exceeds the above-mentioned range, the degradation of battery performance due to the reaction with the non-aqueous electrolyte solution during charging and discharging cannot be ignored, and the cycle retention rate may decrease. On the other hand, if it is less than this range, long time and energy are required for manufacturing and equipment for preventing pollution, and the cost may increase.

[[Aspect Ratio]]

The aspect ratio of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, the active material may become stringy or a uniform coating surface may not be obtained during the production of the negative electrode, and the high current density charge and discharge characteristics may be reduced.

In addition, the aspect ratio is represented by the ratio A/B of the longest diameter A of a particle and the shortest diameter B perpendicular thereto in three-dimensional observation. Observation of particles is performed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed on the end face of the metal with a thickness of 50 microns or less, rotate and tilt the stage on which the sample is fixed, measure A and B of these particles, and calculate the average value of A/B.

[[Orientation Ratio]]

The orientation ratio of the negative electrode active material contained in the negative electrode [9] of the lithium secondary battery of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. If it is less than this range, the high-density charge and discharge characteristics may deteriorate.

The orientation ratio was measured by X-ray diffraction. Using asymmetric Pearson VII as a distribution function, fit the peaks of (110) diffraction and (004) diffraction of carbon obtained by X-ray diffraction, perform peak separation, and calculate the peaks of (110) diffraction and (004) diffraction respectively integral strength. A ratio represented by (110) diffraction integrated intensity/(004) diffraction integrated intensity was calculated from the obtained integrated intensity, and this ratio was defined as the negative electrode active material orientation ratio.

The X-ray diffraction measurement conditions here are as follows. In addition, "2θ" represents a diffraction angle.

Target: Cu (Kα ray) graphite monochromator

· Slit: divergence slit = 1 degree, light receiving slit = 0.1mm, scattering slit = 1 degree

・Measurement range and step angle/measurement time

(110) surface: 76.5 degrees ≤ 2θ ≤ 78.5 degrees 0.01 degrees / 3 seconds

(004) plane: 53.5 degrees ≤ 2θ ≤ 56.0 degrees 0.01 degrees / 3 seconds

[Manufacture of electrode for negative electrode [9]]

The production of the negative electrode can be performed by a conventional method, and the negative electrode can be formed in the same manner as above [9]. The current collector, the thickness ratio of the current collector to the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

"For the negative electrode [10] (mode B)"

The negative electrode [10] (form B) of the present invention relates to a lithium secondary battery, wherein, the negative electrode used in the present invention is specified for the physical properties and/or structure of the negative electrode itself, and the lithium secondary battery includes a non-aqueous electrolyte and has The following specific physical and/or structure of the negative electrode, the non-aqueous electrolyte contains the above-mentioned specific compounds. Next, the negative electrode [10] (form B) of the present invention will be described.

[Negative electrode [10] Physical properties and structure of the negative electrode]

The physical properties and structure of the negative electrode used in the lithium secondary battery of Embodiment B will be described below. The negative electrode has a negative electrode active material layer on a current collector.

[[Reaction Resistance]]

The reaction resistance obtained in the measurement of the opposite impedance (opposed impedance) of the negative electrode used in the aspect B of the present invention must be 500Ω or less, preferably 100Ω or less, more preferably 50Ω or less. The lower limit is not particularly limited. If it exceeds this range, when the lithium secondary battery is produced, the output characteristics before and after the cycle test will decrease. In addition, there may be a decrease in the cycle retention rate due to high electrical resistance.

Next, the method of measuring the opposing impedance will be described. Generally, in the impedance measurement of lithium secondary batteries, the AC impedance is measured between the positive terminal and the negative terminal of the battery. However, if this method is used, the impedance of the positive and negative electrodes mixed together cannot be clearly determined which is positive and negative. Which produces the resistance. Therefore, in the present invention, the reaction resistance generated only by the counter battery of the negative electrode was measured. The method for measuring the reaction resistance in the present invention will be described below.

The measured lithium secondary battery uses the following battery: After charging with a current value that can charge the nominal capacity for 5 hours, maintain the state of not charging and discharging for 20 minutes, and then charge it with a current value that can discharge the nominal capacity for 1 hour. Discharge, the capacity at this time is more than 80% of the nominal capacity. For the lithium secondary battery in the above discharge state, charge it to 60% of the nominal capacity at a current value that can charge the nominal capacity for 5 hours, and immediately transfer the lithium secondary battery to a glove box under an argon atmosphere. Wherein, the lithium secondary battery is quickly disassembled and taken out in a state where the negative electrode is not discharged or short-circuited. If the electrode is coated on both sides, the electrode active material on one side is peeled off without damaging the electrode active material on the other side. The negative electrode was punched to a size of 12.5 mmφ, and the active material surface was opposed to each other without deviation through the separator. 60 μL of the non-aqueous electrolyte solution used in the battery was dripped between the separator and the two negative electrodes and sealed to keep it in a state of not being in contact with the outside world. Conduction was conducted on the current collectors of the two negative electrodes, and an AC impedance method was performed. The measurement was performed at a temperature of 25°C and a complex impedance measurement was performed in a frequency band of 10 ^-2 to 10 ⁵ Hz, and the circle of the negative electrode resistance component of the obtained Coley-Cole curve (Colley-Cole plot) was calculated. The arc is approximated as a semicircle, and the reaction resistance (Rct) and double layer capacity (Cdl) are obtained.

In the lithium secondary battery according to the aspect B of the present invention, as long as the reaction resistance generated by the opposite cell (opposite cell) of the negative electrode satisfies the above-mentioned requirements, the effect of the present invention can be exerted, so that the performance can be fully exhibited, and further Preferably, any one or more of the following physical properties or structures of the negative electrode are preferably satisfied at the same time. In addition, for the negative electrode active material, it is particularly preferable to simultaneously satisfy any one or more of the physical properties of the negative electrode active material described in item A of the aspect.

[[Double Layer Capacity (Cdl)]]

The double-layer capacity (Cdl) obtained by measuring the opposing impedance of the negative electrode used in the present invention is preferably 1×10 ^-6 F or higher, particularly preferably 1×10 ^-5 F or higher, more preferably 3×10 ^-5 F or above. If it is less than this range, since the area which can react decreases, output power may fall as a result.

[[Binder]]

As the binder that binds the negative electrode active material and the current collector, as long as it is a stable material for the non-aqueous electrolyte or the solvent used in the manufacture of the electrode, there are no particular restrictions. The materials and binders that can be used are relatively The ratio etc. of all the negative electrode active material layers are the same as above.

[Negative electrode [10] electrode manufacturing]

The manufacture of the negative electrode [10] can be performed by a conventional method, and the negative electrode [10] can be formed in the same manner as above. The current collector, the thickness ratio of the current collector to the active material layer, electrode density, binder, plate orientation ratio, impedance, and the like are also the same as described above.

<Non-aqueous electrolyte>

The non-aqueous electrolytic solution used in the present invention is not particularly limited as long as it contains an electrolyte (lithium salt) and a non-aqueous solvent and a specific compound for dissolving the electrolyte. The non-aqueous electrolytic solution preferably satisfies the following electrolytic solution [1] ~Electrolyte of any condition in the electrolyte [9]:

Electrolyte [1]: The non-aqueous solvent constituting the electrolyte is a mixed solvent containing at least ethylene carbonate, and the ratio of ethylene carbonate to the total amount of non-aqueous solvent is 1% to 25% by volume;

Electrolyte [2]: The nonaqueous solvent constituting the electrolyte contains at least one asymmetric chain carbonate, and the proportion of the asymmetric chain carbonate in all nonaqueous solvents is 5% to 90% by volume %;

Electrolyte [3]: the non-aqueous solvent constituting the electrolyte contains at least one chain carboxylate;

Electrolyte [4]: The non-aqueous solvent constituting the electrolyte contains a solvent with a flash point above 70°C, and its content is above 60% by volume of all non-aqueous solvents;

Electrolyte [5]: containing LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and/or lithium bis(oxalato)borate as the lithium salt constituting the electrolyte;

Electrolyte [6]: The lithium salt constituting the electrolyte is a fluorine-containing lithium salt, and contains 10 ppm to 300 ppm of hydrogen fluoride (HF) in all non-aqueous electrolytes;

Electrolyte [7]: the electrolyte contains vinylene carbonate, and the content of the vinylene carbonate is in the range of 0.001% by mass to 3% by mass of the total mass of the electrolyte;

Electrolyte solution [8]: the electrolyte solution also contains at least A compound whose content in the entire non-aqueous electrolyte is in the range of 0.001% by mass to 5% by mass;

Electrolyte solution [9]: The electrolyte solution also contains an overcharge preventing agent.

Hereinafter, first, non-aqueous electrolytic solutions generally used in the lithium secondary battery of the present invention will be described.

[lithium salt]

The electrolyte is not particularly limited as long as it is a lithium salt known to be usable as an electrolyte of a nonaqueous electrolytic solution for lithium secondary batteries, and examples thereof include the following lithium salts.

Inorganic lithium salts: LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ and other inorganic fluoride salts; LiClO ₄ , LiBrO ₄ , LiIO ₄ and other perhalide salts; LiAlCl ₄ and other inorganic chloride salts, etc.

Fluorinated organolithium salts: LiCF ₃ SO ₃ and other perfluoroalkane sulfonates; LiN(CF ₃ SO ₂ ) ₂ , LiN(CF ₃ CF ₂ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ) and other perfluoroalkanesulfonylimide salts; LiC(CF ₃ SO ₂ ) ₃ and other perfluoroalkanesulfonylmethylation salts, Li[PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li[PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li[PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li[PF ₄ ( Fluoroalkyl fluorophosphates such as CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Li[PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ], etc.

Oxalatoborates: lithium di(oxalato)borate, lithium difluorooxalatoborate, and the like.

These may be used individually by 1 type, and may use 2 or more types together in arbitrary combinations and ratios. Among them, LiPF ₆ is preferable when the solubility in non-aqueous solvents, charge and discharge characteristics when used as a secondary battery, output characteristics, cycle characteristics, etc. are comprehensively judged.

A preferred example of using two or more types in combination is to use LiPF ₆ and LiBF ₄ in combination. In this case, the ratio of LiBF ₄ to the total of both is preferably 0.01% by mass to 20% by mass, particularly preferably 0.1% by mass to 5% by mass. %.

In addition, another example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonylimide salt. At this time, the ratio of the inorganic fluoride salt to the total of the two is preferably 70% by mass to 99% by mass, more preferably 80% by mass. % by mass to 98% by mass. The combined use of both has an effect of suppressing deterioration due to high-temperature storage.

The concentration of the lithium salt in the non-aqueous electrolytic solution is not particularly limited, but is usually 0.5 mol/L or higher, preferably 0.6 mol/L or higher, more preferably 0.7 mol/L or higher. In addition, the upper limit thereof is usually 2 mol/L or less, preferably 1.8 mol/L or less, more preferably 1.7 mol/L or less. If the concentration is too low, the conductivity of the non-aqueous electrolytic solution may be insufficient. On the other hand, if the concentration is too high, the conductivity may decrease due to an increase in viscosity, and the performance of the lithium secondary battery may decrease.

[Non-aqueous solvent]

As the non-aqueous solvent, it can be appropriately selected and used from those conventionally proposed as solvents for non-aqueous electrolytic solutions. For example, the following non-aqueous solvents are mentioned.

1) Cyclic carbonate:

The number of carbon atoms of the alkylene group constituting the cyclic carbonate is preferably 2-6, particularly preferably 2-4. Specifically, ethylene carbonate, propylene carbonate, butylene carbonate, etc. are mentioned, for example. Among them, ethylene carbonate and propylene carbonate are preferable.

2) Chain carbonate

As the chain carbonate, dialkyl carbonate is preferable, and the number of carbon atoms of the alkyl group constituting the dialkyl carbonate is preferably 1-5, particularly preferably 1-4. Specifically, for example, dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, etc. . Among them, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable.

3) Cyclic esters:

Specifically, γ-butyrolactone, γ-valerolactone, etc. are mentioned, for example.

4) Chain esters:

Specifically, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, etc. are mentioned, for example.

5) Cyclic ethers

Specifically, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, etc. are mentioned, for example.

6) Chain ethers:

Specifically, dimethoxyethane, dimethoxymethane, etc. are mentioned, for example.

7) Sulfur-containing organic solvents:

Specifically, for example, sulfolane, diethylsulfone, etc. are mentioned.

These may be used individually or in combination of 2 or more types, Preferably it is used in combination of 2 or more types. For example, it is preferable to use a solvent with a high dielectric constant such as cyclic carbonates or cyclic esters in combination with a low-viscosity solvent such as chain carbonates or chain esters.

One of the preferred combinations of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of cyclic carbonates and chain carbonates accounts for 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more in the non-aqueous solvent. In addition, the capacity of cyclic carbonates is 5% or more, preferably 10% or more, more preferably 15% or more, and usually 50% or less with respect to the total of cyclic carbonates and chain carbonates, Preferably it is 35% or less, More preferably, it is 30% or less. It is particularly preferred to combine the above-mentioned preferred volume ranges of the total carbonates in the non-aqueous solvent with the above-mentioned preferred volume ranges of cyclic carbonates with respect to cyclic and chain carbonates. Use of this combination of non-aqueous solvents is preferred because the balance between cycle characteristics and high-temperature storage characteristics (especially residual capacity after high-temperature storage and high-load discharge capacity) of a battery manufactured using the combination becomes excellent.

The mixed solvent contains lithium salts and cyclic siloxane compounds represented by the above general formula (1), fluorosilane compounds represented by the above general formula (2), and compounds represented by the above general formula (3) , a compound having an S-F bond in the molecule, a non-aqueous electrolyte of at least one compound in nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate, due to the use of the non-aqueous A battery made of an electrolyte solution is preferable because it is excellent in balance between cycle characteristics, high-temperature storage characteristics (particularly, residual capacity after high-temperature storage and high-load discharge capacity), and suppression of gas generation.

Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate Ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate esters, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, etc. A combination in which propylene carbonate is further added to these combinations of ethylene carbonate and chain carbonate is mentioned as a preferable combination. When propylene carbonate is contained, the capacity ratio of ethylene carbonate and propylene carbonate is usually 99:1 to 40:60, preferably 95:5 to 50:50.

Further, if the amount of propylene carbonate accounting for the total non-aqueous solvent is more than 0.1% by volume, preferably more than 1% by volume, more preferably more than 2% by volume, and usually less than 10% by volume, preferably 8% by volume It is less than, more preferably 5% by volume or less, since it is possible to maintain the characteristics of the combination of ethylene carbonate and chain carbonates, and the low-temperature characteristics are more excellent, so it is preferable.

Among them, it is further preferred to contain asymmetric chain carbonates, especially ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate , dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and other ethylene carbonate, symmetrical chain carbonates and asymmetric chain carbonates, because the balance between cycle characteristics and large current discharge characteristics is excellent, so preferred. Among them, the asymmetric chain carbonates are preferably ethyl methyl carbonate, and the number of carbon atoms of the alkyl group constituting the dialkyl carbonate is preferably 1-2.

Other examples of preferred non-aqueous solvents are non-aqueous solvents containing chain esters. As a chain ester, methyl acetate, ethyl acetate, etc. are especially preferable. The capacity of the chain ester in the non-aqueous solvent is usually 5% or more, preferably 8% or more, more preferably 15% or more, and usually 50% or less, preferably 35% or less, more preferably 30% or less , More preferably 25% or less. In particular, it is preferable to contain a chain ester in the mixed solvent of the above-mentioned cyclic carbonates and chain carbonates from the viewpoint of improving the low-temperature characteristics of the battery.

Examples of other preferred non-aqueous solvents are an organic solvent selected from ethylene carbonate, propylene carbonate, γ-butyrolactone and γ-valerolactone, or containing 2 selected from this group A non-aqueous solvent in which the mixed solvent of the above organic solvents accounts for more than 60% by volume of the total solvents. Such a mixed solvent preferably has a flash point of 50°C or higher, and particularly preferably a flash point of 70°C or higher. Even if the nonaqueous electrolytic solution using this solvent is used at a high temperature, evaporation of the solvent and leakage are reduced. Wherein, if the amount of γ-butyrolactone in the non-aqueous solvent is 60% by volume or more, the total of ethylene carbonate and γ-butyrolactone accounts for 80% by volume or more in the non-aqueous solvent, preferably A solvent that is more than 90% by volume and has a volume ratio of ethylene carbonate to γ-butyrolactone of 5:95 to 45:55, or the total of ethylene carbonate and propylene carbonate accounts for 80% by volume in a non-aqueous solvent % or more, preferably 90% by volume or more, and a solvent in which the volume ratio of ethylene carbonate and propylene carbonate is 30:70 to 60:40, the balance between general cycle characteristics and large current discharge characteristics becomes excellent.

[specific compound]

The non-aqueous electrolytic solution of the present invention, as described above, is characterized in that it contains or adds a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a fluorosilane compound represented by the general formula Compounds shown in (3), compounds having an S-F bond in the molecule, at least one compound of nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates, and propionates (sometimes they are referred to as "Specific Compound").

[[Cyclic siloxane compound represented by general formula (1)]]

R ¹ and R ² in the cyclic siloxane compound represented by the general formula (1) are organic groups having 1 to 12 carbon atoms which may be the same or different from each other, and examples of R ¹ and R ² include methyl Chain alkyl such as radical, ethyl, n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl; cyclic alkyl such as cyclohexyl, norbornyl; vinyl, 1 -alkenyl such as propenyl, allyl, butenyl, 1,3-butadienyl; alkynyl such as ethynyl, propynyl, butynyl; haloalkyl such as trifluoromethyl; 3-pyrrole Alkyl groups with saturated heterocyclic groups such as alkanopropyl groups; aryl groups such as phenyl groups that may have alkyl substituents; aralkyl groups such as phenylmethyl and phenylethyl groups; trialkyl groups such as trimethylsilyl groups silyl group; trimethylsiloxane group and other trialkylsiloxane groups, etc.

Among them, a group having a small number of carbon atoms tends to exhibit characteristics, and is preferably an organic group having 1 to 6 carbon atoms. In addition, the alkenyl group improves the output power characteristics by acting on the non-aqueous electrolyte or the coating film on the electrode surface, and the aryl group has the effect of improving the overall performance of the battery by capturing the free radicals generated in the battery during charge and discharge, so it is preferred. Therefore, R ¹ and R ² are particularly preferably methyl, vinyl or phenyl.

In General formula (1), n represents the integer of 3-10, Preferably it is an integer of 3-6, Especially preferably, it is 3 or 4.

Examples of the cyclic siloxane compound represented by the general formula (1) include hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1 , 3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane and other cyclotrisiloxanes; octamethylcyclotetrasiloxane and other cyclotetrasiloxanes; decamethylcyclopentasiloxane and other Cyclopentasiloxane, such as siloxane, etc. Among them, cyclotrisiloxane is particularly preferable.

[[Fluorosilane compound represented by general formula (2)]]

R ³ to R ⁵ in the fluorosilane compound represented by the general formula (2) are organic groups with 1 to 12 carbon atoms that may be the same or different from each other, except for R ¹ and R in the general formula (1) Examples of ² include chain alkyl, cyclic alkyl, alkenyl, alkynyl, haloalkyl, alkyl having a saturated heterocyclic group, aryl such as phenyl that may have an alkyl, aralkyl, In addition to trialkylsilyl and trialkylsiloxyl groups, carbonyl groups such as ethoxycarbonylethyl; carboxyl groups such as acetoxy, acetoxymethyl, and trifluoroacetoxy; methoxy , ethoxy, propoxy, butoxy, phenoxy, allyloxy and other oxygen groups; allylamino and other amino groups; benzyl and the like.

In general formula (2), x represents the integer of 1-3, p, q, and r represent the integer of 0-3 respectively, and 1≤p+q+r≤3. Also, x+p+q+r=4 necessarily.

Examples of the fluorosilane compound represented by the general formula (2) include trimethylfluorosilane, triethylfluorosilane, tripropylfluorosilane, phenyldimethylfluorosilane, triphenylfluorosilane, Vinyldimethylfluorosilane, vinyldiethylfluorosilane, vinyldiphenylfluorosilane, trimethoxyfluorosilane, triethoxyfluorosilane and other monofluorosilanes, as well as dimethyldifluorosilane, Difluorosilanes such as diethyldifluorosilane, divinyldifluorosilane, and ethylvinyldifluorosilane; trifluorosilanes such as methyltrifluorosilane and ethyltrifluorosilane.

When the fluorosilane compound represented by the general formula (2) has a low boiling point, it may be difficult to contain a predetermined amount in the non-aqueous electrolytic solution due to volatilization. In addition, after being contained in the non-aqueous electrolytic solution, it may volatilize under conditions such as heat generation of the battery due to charge and discharge, or high temperature of the external environment. Therefore, compounds having a boiling point of 50°C or higher at 1 atmosphere are preferred, and compounds having a boiling point of 60°C or higher are particularly preferred.

In addition, like the compound of general formula (1), as an organic group, a group with a small number of carbon atoms is likely to exhibit an effect, and an alkenyl group with 1 to 6 carbon atoms acts on the surface of a non-aqueous electrolyte or an electrode. The coating film can improve the output power characteristics, and the aryl group can capture the free radicals generated in the battery during charging and discharging to improve the overall performance of the battery. Therefore, from this point of view, the organic group is preferably a methyl group, vinyl group, or phenyl group, and examples of the compound are particularly preferably trimethylfluorosilane, vinyldimethylfluorosilane, phenyldimethylsilane, or phenyldimethylsilane. Fluorosilane, vinyl diphenyl fluorosilane, etc.

[[Compound represented by general formula (3)]]

R ⁶ to R ⁸ in the compound represented by the general formula (3) are organic groups having 1 to 12 carbon atoms which may be the same or different from each other, and examples thereof include the same as in the general formula (2) Examples of R ³ to R ⁵ include chain alkyl, cyclic alkyl, alkenyl, alkynyl, haloalkyl, alkyl with saturated heterocyclic group, aromatic group such as phenyl that may have alkyl, etc. group, aralkyl group, trialkylsilyl group, trialkylsiloxy group, carbonyl group, carboxyl group, oxy group, amino group, benzyl group, etc.

A in the compound represented by the general formula (3) is not particularly limited as long as it is a group consisting of H, C, N, O, F, S, Si and/or P. As the general formula (3) The element directly bonded to the oxygen atom in is preferably C, S, Si or P. The presence of these atoms is preferably, for example, a chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a haloalkyl group, a carbonyl group, a sulfonyl group, a trialkylsilyl group, a phosphoryl group, a phosphinyl group, and the like. middle.

In addition, the molecular weight of the compound represented by the general formula (3) is preferably 1000 or less, particularly preferably 800 or less, more preferably 500 or less. Examples of compounds represented by the general formula (3) include hexamethyldisiloxane, 1,3-diethyltetramethyldisiloxane, hexaethyldisiloxane, octamethyldisiloxane, Silicone compounds such as trisiloxane; alkoxysilanes such as methoxytrimethylsilane and ethoxytrimethylsilane; peroxides such as bis(trimethylsilyl) peroxide; Trimethylsilyl acetate, triethylsilyl acetate, trimethylsilyl propionate, trimethylsilyl methacrylate, trimethylsilyl trifluoroacetate, etc. Carboxylic acid esters; trimethylsilyl methanesulfonate, trimethylsilyl ethanesulfonate, triethylsilyl methanesulfonate, trimethylsilyl fluoromethanesulfonate, etc. Sulfonate esters; bis(trimethylsilyl)sulfate and other sulfate esters; tris(trimethylsilyloxy)boron and other borate esters; tris(trimethylsilyl)phosphate, tri Phosphoric acid such as (trimethylsilyl) phosphite or phosphite, etc.

Among them, silicone compounds, sulfonate esters, and sulfate esters are preferable, and sulfonate esters are particularly preferable. As the siloxane compound, hexamethyldisiloxane is preferred; as the sulfonate, trimethylsilyl methanesulfonate is preferred; as the sulfuric acid ester, bis(trimethylsilyl)sulfuric acid is preferred. ester.

[[Compounds with S-F bonds in the molecule]]

The compound having an S-F bond in the molecule is not particularly limited, but sulfonyl fluorides and fluorosulfonate esters are preferable.

For example, methanesulfonyl fluoride, ethanesulfonyl fluoride, methanebis(sulfonyl fluoride), ethane-1,2-bis(sulfonyl fluoride), propane-1,3-bis(sulfonyl fluoride), Butane-1,4-bis(sulfonyl fluoride), difluoromethane bis(sulfonyl fluoride), 1,1,2,2-tetrafluoroethane-1,2-bis(sulfonyl fluoride), 1, 1,2,2,3,3-hexafluoropropane-1,3-bis(sulfonyl fluoride), methyl fluorosulfonate, ethyl fluorosulfonate, etc. Among them, methanesulfonyl fluoride, methanebis(sulfonyl fluoride) or methyl fluorosulfonate is preferable.

[[Nitrate, Nitrite, Monofluorophosphate, Difluorophosphate, Acetate, Propionate]]

As the counter cation of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, propionate, there is no particular limitation, except metal elements such as Li, Na, K, Mg, Ca, Fe, Cu, etc. In addition, ammonium and quaternary ammonium represented by NR ⁹ R ¹⁰ R ¹¹ R ¹² (in the formula, R ⁹ to R ¹² each independently represent a hydrogen atom or an organic group having 1 to 12 carbon atoms) can also be mentioned. Among them, as the organic groups with 1 to 12 carbon atoms of R ⁹ to R ¹² , there may be mentioned alkyl groups which may be substituted by halogen atoms, cycloalkyl groups which may be substituted by halogen atoms, aromatic groups which may be substituted by halogen atoms, group, heterocyclic group containing nitrogen atom, etc. R ⁹ to R ¹² are each preferably a hydrogen atom, an alkyl group, a cycloalkyl group, a nitrogen atom-containing heterocyclic group, or the like. Among these counter cations, lithium, sodium, potassium, magnesium, calcium, or NR ⁹ R ¹⁰ R ¹¹ R ¹² are preferred from the viewpoint of battery characteristics when used in a lithium secondary battery, and lithium is particularly preferred. Among them, nitrates or difluorophosphates are preferable, and lithium difluorophosphate is particularly preferable from the standpoint of output power improvement rate and cycle characteristics. In addition, these compounds may be used substantially as they are synthesized in a non-aqueous solvent, or may be added to a non-aqueous solvent that is synthesized separately and substantially isolated.

Specific compounds, namely cyclic siloxane compounds represented by general formula (1), fluorosilane compounds represented by general formula (2), compounds represented by general formula (3), compounds with S-F bonds in their molecules, nitric acid Salts, nitrites, monofluorophosphates, difluorophosphates, acetates, or propionates may be used alone, or two or more compounds may be used in combination in any combination and ratio. In addition, among the specific compounds, even among the above-mentioned separately classified compounds, one kind may be used alone, or two or more kinds of compounds may be used in combination in any combination and ratio.

The ratio of these specific compounds in the nonaqueous electrolytic solution must be 10 ppm or more (0.001 mass % or more) in total with respect to the entire nonaqueous electrolytic solution, preferably 0.01 mass % or more, more preferably 0.05 mass % or more , and more preferably 0.1% by mass or more. In addition, the upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. If the concentration of the specific compound is too low, it may be difficult to improve the battery output or to extend the battery life. On the other hand, if the concentration is too high, the charge and discharge efficiency may decrease.

In addition, when these specific compounds are actually used in the manufacture of secondary batteries as non-aqueous electrolytes, the contents of the non-aqueous electrolytes are often significantly reduced when the batteries are disassembled and taken out again. Therefore, it is within the scope of the present invention that at least the above-mentioned specific compound can be detected from the non-aqueous electrolytic solution extracted from the battery. The non-aqueous electrolytic solution related to the present invention can be prepared by dissolving an electrolyte lithium salt, a specific compound, and other compounds as needed in a non-aqueous solvent. When preparing a non-aqueous electrolyte, it is preferable to dehydrate each raw material in advance so that the moisture content is usually 50 ppm or less, preferably 30 ppm or less, particularly preferably 10 ppm or less.

[Other compounds]

The non-aqueous electrolytic solution in the present invention contains a lithium salt as an electrolyte and a specific compound as essential components in a non-aqueous solvent, and may contain any amount of other compounds as needed within the range not impairing the effect of the present invention. As the other compound, specifically, the following substances can be mentioned, for example:

(1) Aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, and dibenzofuran; 2 - Partial fluorides of the above-mentioned aromatic compounds such as fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6- Anti-overcharge agents such as difluoroanisole, 3,5-difluoroanisole and other fluorine-containing anisole compounds;

(2) Vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, trifluoropropylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic Anode coating film forming agents such as acid anhydride and cyclohexanedicarboxylic anhydride;

(3) Ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sultone, butane sultone, methyl methanesulfonate, butyl dimesylate, methyl toluenesulfonate Ester, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, anise sulfur Ether, diphenyl disulfide, dipyridine disulfide and other positive electrode protective agents.

As the anti-overcharge agent, biphenyl, alkylbiphenyl, terphenyl, partial hydrogenated product of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, dibenzofuran and other aromatic compounds are preferable. Family compounds. These can be used in combination of 2 or more types. When two or more are used in combination, it is particularly preferable to use cyclohexylbenzene or terphenyl (or a partially hydrogenated product thereof) in combination with tert-butylbenzene or tert-amylbenzene.

As the negative electrode coating film forming agent, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, and maleic anhydride are preferable. These can be used in combination of 2 or more types. When two or more are used in combination, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, or maleic anhydride are preferable. As the positive electrode protective agent, ethylene sulfite, propylene sulfite, propane sultone, butane sultone, methyl methanesulfonate, and butyl methanesulfonate are preferable. These can be used in combination of 2 or more types. In addition, it is particularly preferable to use a negative electrode coating film forming agent and a positive electrode protective agent in combination, and to use an overcharge preventing agent, a negative electrode coating film forming agent and a positive electrode protective agent in combination.

The content ratio of these other compounds in the nonaqueous electrolytic solution is not particularly limited, and is preferably 0.01% by mass or more, more preferably 0.1% by mass, and even more preferably 0.2% by mass, with respect to the entire nonaqueous electrolytic solution, and the upper limit is preferably It is 5 mass % or less, More preferably, it is 3 mass %, More preferably, it is 2 mass % or less. By adding these compounds, when an abnormality occurs due to overcharging, it is possible to suppress rupture and fire of the battery, and to improve capacity retention characteristics and cycle characteristics after high-temperature storage.

The method for preparing the non-aqueous electrolyte solution for secondary batteries of the present invention is not particularly limited, and can be prepared by dissolving lithium salts, specific compounds, and other compounds as needed in a non-aqueous solvent according to a conventional method.

<Electrolyte[1]>

In the above-mentioned non-aqueous electrolytic solution, it is preferable that the non-aqueous solvent constituting the electrolytic solution is a mixed solvent containing at least "ethylene carbonate", and the ratio of ethylene carbonate to the total amount of non-aqueous solvent is 1% by volume to 25% by volume (Electrolyte[1]).

Types and contents of "lithium salts", "non-aqueous solvents other than ethylene carbonate (EC)", "specific compounds" and "other compounds" in the present invention (electrolyte solution [1]), use conditions, non-aqueous solvents, etc. The preparation method and the like of the aqueous electrolytic solution are the same as described above.

<Electrolyte[2]>

In the above-mentioned non-aqueous electrolytic solution, it is preferable that the non-aqueous solvent constituting the electrolytic solution contains "at least one asymmetric chain carbonate" and the content ratio of the asymmetric chain carbonate in all non-aqueous solvents is 5 Volume %～90 volume % (electrolyte solution [2]).

The type and content of "lithium salt", "nonaqueous solvent other than asymmetric chain carbonate", "specific compound" and "other compound" in the present invention (electrolyte solution [2]), use conditions, nonaqueous The preparation method and the like of the electrolytic solution are the same as described above.

In the present invention (electrolyte solution [2]), at least one asymmetric chain carbonate is contained in 5% by volume to 90% by volume in the total non-aqueous solvent. Further, the content of at least one asymmetric chain carbonate in all nonaqueous solvents is preferably 8% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, particularly preferably 20% by volume or more In addition, the upper limit is preferably 85% by volume or less, more preferably 70% by volume or less, even more preferably 60% by volume or less, and particularly preferably 45% by volume or less. It is preferred due to the high low-temperature characteristics and cycle characteristics of the present invention. .

The asymmetric chain carbonate is not particularly limited, but is preferably an asymmetric alkyl carbonate, and preferably the alkyl group has 1 to 4 carbon atoms. Specific examples of such asymmetric alkyl carbonates include, for example, ethyl methyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, methyl isopropyl carbonate, ethyl carbonate Isopropyl ester, methyl n-butyl carbonate, ethyl n-butyl carbonate, etc. Among them, preferably ethyl methyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, methyl n-butyl carbonate, ethyl n-butyl carbonate, more preferably methyl ethyl carbonate, carbonic acid Methyl-n-propyl ester, methyl-n-butyl carbonate, particularly preferably methyl ethyl carbonate. These asymmetric chain carbonates may be used in combination of two or more.

As mentioned above, the nonaqueous solvent can mix and use 2 or more types. In particular, it is preferable to further contain at least one kind of cyclic carbonate in addition to the asymmetric chain carbonate from the viewpoint of improving the cycle characteristics and storage characteristics of the secondary battery. When a cyclic carbonate is contained, the ratio of the cyclic carbonate to the total non-aqueous solvent is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and the upper limit is usually 50% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less, even more preferably 25% by volume or less. If the ratio of the cyclic carbonate in all non-aqueous solvents is too small, the cycle characteristics and storage characteristics of the secondary battery may not be improved. On the other hand, if it is too large, the low-temperature discharge characteristics may sometimes decrease. .

In addition, it is preferable to further contain at least one kind of symmetrical chain carbonate in addition to the asymmetric chain carbonate from the viewpoint of improving the balance between cycle characteristics, storage characteristics, and low-temperature discharge characteristics of the secondary battery. When a symmetrical chain carbonate is contained, the proportion of the symmetrical chain carbonate in the total non-aqueous solvent is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and the upper limit is usually 80 volume % or less, Preferably it is 70 volume % or less, More preferably, it is 50 volume % or less, More preferably, it is 40 volume % or less. If the proportion of the symmetrical chain carbonate in all non-aqueous solvents is too small, sometimes the cycle characteristics or the balance between storage characteristics and low-temperature discharge characteristics cannot be obtained. On the other hand, if it is too large, sometimes it cannot be achieved to excellent cycle characteristics.

In addition, a mixed solvent of an asymmetric chain carbonate and two or more other non-aqueous solvents is preferable. That is, a mixed solvent containing three or more components of the asymmetric chain carbonate is preferable. As a mixed solvent of two or more non-aqueous solvents other than asymmetric chain carbonates, since it can improve all battery performance such as charge and discharge characteristics, battery life, etc., it is preferable to use high dielectric strength such as cyclic carbonates or cyclic esters. A constant solvent and a low-viscosity solvent such as a symmetrical chain carbonate or a chain ester are used in combination, and a combination of a cyclic carbonate and a symmetrical chain carbonate is particularly preferable. The mixing ratio at this time is not particularly limited, but from the aspects of improving cycle characteristics, storage characteristics, etc., preferably relative to 100 parts by volume of asymmetric chain carbonates, high dielectric constant solvents such as cyclic carbonates or cyclic esters are 10 ~400 parts by volume, and low-viscosity solvents such as symmetrical chain carbonates or chain esters are 10 to 800 parts by volume.

One of the preferred combinations of two or more types of non-aqueous solvents other than asymmetric chain carbonates is a combination mainly of cyclic carbonates and symmetrical chain carbonates. Specific examples of a preferable combination of cyclic carbonate and symmetrical chain carbonate include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate. The content ratio in all non-aqueous solvents is not particularly limited, but preferably 8 to 80% by volume of asymmetric chain carbonates, 10 to 35% by volume of cyclic carbonates, and 10 to 70% by volume of symmetrical chain carbonates. .

A combination in which propylene carbonate is further added to these combinations of ethylene carbonate and symmetrical chain carbonate is mentioned as a preferable combination. When propylene carbonate is contained, the capacity ratio of ethylene carbonate to propylene carbonate is preferably 99:1 to 40:60, particularly preferably 95:5 to 50:50.

Another preferred combination of two or more nonaqueous solvents other than the asymmetric chain carbonate is a combination containing a chain ester. In particular, from the viewpoint of improving the low-temperature characteristics of the battery, a combination containing the above-mentioned cyclic carbonate and a chain ester is preferable, and as the chain ester, methyl acetate, ethyl acetate, and the like are particularly preferable. The proportion of the chain ester in the total non-aqueous solvent is preferably 5% by volume or more, more preferably 8% by volume or more, particularly preferably 15% by volume or more, and the upper limit thereof is preferably 50% by volume or less, more preferably 35% by volume % or less, more preferably 30 volume % or less, particularly preferably 25 volume % or less. Therefore, at this time, the content ratio in all non-aqueous solvents is preferably as follows: asymmetric chain carbonate is 8 to 85 volume%, cyclic carbonate is 10 to 35 volume%, and chain ester is 5 to 50 volume%. .

A combination in which a symmetrical chain carbonate is further added to these combinations of cyclic carbonate and chain ester can be cited as a preferable combination. When a symmetrical chain carbonate is contained, the content ratio of the symmetrical chain carbonate in the entire non-aqueous solvent is preferably 10 to 60% by volume.

As specific examples of the preferred combination of the non-aqueous solvent of the non-aqueous electrolytic solution for secondary batteries of the present invention, for example, ethyl methyl carbonate and ethylene carbonate, methyl n-propyl carbonate and ethylene carbonate , a combination of asymmetric chain carbonates and cyclic carbonates such as ethyl methyl carbonate, ethylene carbonate and propylene carbonate, methyl-n-propyl carbonate, ethylene carbonate and propylene carbonate; methyl carbonate Ethyl carbonate, ethylene carbonate and dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate and diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and dimethyl carbonate, methyl carbonate N-propyl carbonate, ethylene carbonate and dimethyl carbonate, methyl-n-propyl carbonate, ethylene carbonate and diethyl carbonate, methyl-n-propyl carbonate, ethylene carbonate, diethyl carbonate Combinations of asymmetric chain carbonates, cyclic carbonates and symmetrical chain carbonates such as esters and dimethyl carbonate; ethyl methyl carbonate, ethylene carbonate and methyl acetate, ethyl methyl carbonate, ethylene carbonate Combinations of asymmetric chain carbonates, cyclic carbonates and chain esters such as ethyl acetate; ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate and methyl acetate, ethyl methyl carbonate, ethylene carbonate Combinations of unsymmetrical chain carbonates, cyclic carbonates, symmetrical chain carbonates, and chain esters such as esters, diethyl carbonate, and methyl acetate.

The mixed solvent contains lithium salt and the above-mentioned specific compound such as difluorophosphate in an amount of 10 ppm or more relative to the total mass of the electrolyte, and the content ratio of the asymmetric chain carbonate in all non-aqueous solvents is 5% by volume The non-aqueous electrolyte of ~90% by volume is due to the cycle characteristics, low-temperature discharge characteristics, high-temperature storage characteristics (especially the residual capacity after high-temperature storage and high-load discharge capacity) of the secondary battery manufactured using it, and the balance change of suppressing gas generation. It is excellent and therefore preferred.

<Electrolyte[3]>

Among the above-mentioned non-aqueous electrolytic solutions, it is preferable that the non-aqueous solvent constituting the electrolytic solution contains at least "one or more kinds of chain carboxylate" (electrolytic solution [3]).

Types and contents of "lithium salts", "non-aqueous solvents other than chain carboxylic acid esters", "specific compounds" and "other compounds" in the present invention (electrolyte solution [3]), use conditions, non-aqueous electrolysis The preparation method of the liquid and the like are the same as above.

The chain carboxylate used in the present invention (electrolyte solution [3]) is not particularly limited, but is preferably an alkane having 1 to 4 carbon atoms of a carboxylic acid having 1 to 5 carbon atoms including the carbon of the carboxyl group. base ester. In addition, there is no particular limitation on the number of carboxylic acids mentioned above, but monocarboxylic acids or dicarboxylic acids are preferred.

Among them, fatty acid esters such as formate, acetate, propionate, and butyrate; various dicarboxylic acid esters, etc. are preferred, and acetate and propionate are particularly preferred.

Specifically, methyl acetate, ethyl acetate, propyl acetate, methyl propionate or ethyl propionate is preferred, and methyl acetate, ethyl acetate or methyl propionate is particularly preferred.

In addition, these chain carboxylic acid esters can be used in mixture of 2 or more types. The combination of mixing is not particularly limited, as a preferred combination, methyl acetate and ethyl acetate, methyl acetate and methyl propionate, ethyl acetate and methyl propionate, methyl acetate, ethyl acetate and propionate Acid methyl ester etc. Thus, the balance between output characteristics, high-temperature storage characteristics, and the like can be adjusted according to purposes.

When using a mixed solvent of the chain carboxylate and other non-aqueous solvents, the content ratio of the chain carboxylate to the entire non-aqueous solvent is preferably 3% by volume or more, more preferably 5% by volume or more , more preferably 8% by volume or more, particularly preferably 10% by volume or more, and the upper limit is preferably 50% by volume or less, more preferably 35% by volume or less, further preferably 30% by volume or less, particularly preferably 25% by volume Hereinafter, it is preferable because it has both high low-temperature characteristics and cycle characteristics of the present invention.

Although the reason why the low-temperature output characteristics are greatly improved by combining the chain carboxylate and the above-mentioned specific compound is not clear, the above-mentioned specific compound may have some degree of improvement in low-temperature characteristics even when the chain carboxylate is not contained effect, which is considered to be due to a certain action on the electrode, which is promoted by the chain carboxylate, in other words, it is considered to be due to the presence of the chain carboxylate which is also high in fluidity at low temperatures, and these specific compounds penetrate into the The effect is exerted without waste inside the electrode plate, or the chain carboxylate propagates the interaction of the above-mentioned specific compound and the electrode.

<Electrolyte [4]>

Among the non-aqueous electrolytic solutions, it is preferable that the non-aqueous solvent constituting the electrolytic solution contains a solvent having a flash point of 70° C. or higher at 60% by volume or more of the total non-aqueous solvent (electrolyte solution [4]).

The types and contents of "lithium salts", "non-aqueous solvents other than solvents with a flash point of 70°C or higher", "specific compounds" and "other compounds" in the present invention (electrolyte solution [4]), use conditions, non-aqueous solvents, etc. The preparation method and the like of the aqueous electrolytic solution are the same as described above.

In the present invention, the non-aqueous solvent must contain a solvent having a flash point of 70° C. or higher in an amount of at least 60% by volume of the total non-aqueous solvent. Further, it is preferable to contain 60% by volume or more of the total non-aqueous solvents and a solvent with a flash point of 80° C. or higher, and it is particularly preferred to contain 60% by volume or more of the total non-aqueous solvents and have a flash point of 90° C. or higher. solvent.

The solvent having a flash point of 70° C. or higher is not particularly limited, and examples thereof include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and the like as preferred solvents, and particularly Preference is given to ethylene carbonate, propylene carbonate or gamma-butyrolactone. These solvents may be used alone or in combination of two or more, and the combination is not particularly limited.

In addition, from the viewpoint of improving cycle characteristics, a composition containing 10% by volume or more of ethylene carbonate or propylene carbonate relative to the total non-aqueous solvent is preferable. On the other hand, if a large amount of ethylene carbonate is contained, the low-temperature characteristics will decrease, so the content of ethylene carbonate is preferably 70% by volume or less, particularly preferably 60% by volume or less, of the total non-aqueous solvent.

On a total basis, preferred examples of non-aqueous solvents containing solvents having a flash point of 70° C. or more of 60% by volume or more of the total non-aqueous solvents are:

(1) Non-aqueous solvents in which γ-butyrolactone accounts for more than 60% by volume in all non-aqueous solvents;

(2) The total of ethylene carbonate and γ-butyrolactone accounts for more than 80% by volume in all non-aqueous solvents, preferably accounts for more than 85% by volume and the capacity ratio of ethylene carbonate and γ-butyrolactone is 5: 95～45:55 non-aqueous solvent;

(3) The sum of ethylene carbonate and propylene carbonate accounts for more than 80% by volume in all non-aqueous solvents, preferably accounts for more than 85% by volume and the capacity ratio of ethylene carbonate and propylene carbonate is 30: 70～ 60:40 non-aqueous solvent, etc.

Use of these non-aqueous solvents provides excellent balance between cycle characteristics, high-current discharge characteristics, and the like.

In addition, the non-aqueous electrolytic solution preferably has a flash point of 40°C or higher, more preferably 50°C or higher, still more preferably 60°C or higher, particularly preferably 70°C or higher. Unless the flash point of the aqueous electrolytic solution is too low, there may be a fear of ignition of the electrolytic solution when the battery is exposed to high temperature.

The non-aqueous solvent used in the non-aqueous electrolytic solution for secondary battery of the present invention can be further mixed with a non-aqueous solvent component (hereinafter referred to as "other non-aqueous solvent components" with a flash point of less than 70 ° C) in a solvent with a flash point of more than 70 ° C. ). Such other nonaqueous solvent components can be appropriately selected and used from solvents conventionally proposed as solvents for nonaqueous electrolytic solutions. For example, the following non-aqueous solvents are mentioned.

(1) Chain carbonate

As the chain carbonate, dialkyl carbonate is preferable, and the number of carbon atoms of the alkyl group constituting the dialkyl carbonate is preferably 1-5, particularly preferably 1-4. Specifically, for example, dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, etc. . Among them, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable.

(2) chain ester

Specifically, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, etc. are mentioned, for example.

(3) Cyclic ether

Specifically, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, etc. are mentioned, for example.

(4) chain ether

Specifically, dimethoxyethane, dimethoxymethane, etc. are mentioned, for example.

The other non-aqueous solvent components may be used in combination with the "solvent having a flash point of 70° C. or higher", or two or more other non-aqueous solvent components may be used in combination. In this case, it is preferable to use a chain carbonate and/or a chain ester in combination with a "solvent having a flash point of 70° C. or higher" particularly from the viewpoint of cycle characteristics and large-current discharge characteristics.

The content of the solvent having a flash point of 70° C. or higher in all non-aqueous solvents must be 60% by volume or more, preferably 70% by volume or more, more preferably 75% by volume or more, further preferably 80% by volume or more, and particularly preferably 85% by volume. capacity % above. In addition, the upper limit thereof is preferably 100% by volume or less, particularly preferably 90% by volume or less. If the content of the solvent having a flash point of 70° C. or higher is too small, the desired effect of easily increasing the internal pressure may not be obtained when the battery is stored at a high temperature. The rate decreases, and the performance of the lithium secondary battery sometimes decreases.

Although the reason why the output power characteristics are excellent when a certain amount or more of a solvent with a high flash point is used for a nonaqueous electrolyte secondary battery using the nonaqueous electrolyte solution (electrolyte solution [4]) of the present invention is not clear, it is considered that The reasons are as follows, but the present invention should not be limited to the following reasons. That is, it is considered that the above-mentioned specific compound acts on the electrode to reduce the reaction resistance related to the entry and exit of lithium ions, thereby improving the output characteristics. In addition, it is considered that solvents with high flash points such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone have higher dielectric constants than chain carbonates, and there is a certain The effect becomes remarkable in the case of a solvent with a high dielectric constant of more than a certain degree. It is further considered that the battery element contained in one battery case of the secondary battery has a battery capacity of 3 ampere hours (Ah) or more and/or the DC resistance component of the secondary battery is 10 milliohms (Ω) In the following cases, the contribution of the DC resistance component is reduced, and the original effect of the non-aqueous electrolytic solution is more likely to be exhibited compared with a battery with a large contribution of the DC resistance component.

<Electrolyte [5]>

In the above-mentioned non-aqueous electrolytic solution, it is preferable to contain LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer of 1 to 4) and/or bis(oxalato)lithium borate as constituents of the electrolytic solution. Electrolyte of "lithium salt" (electrolyte [5]).

The types and contents of "non-aqueous solvent", "specific compound", and "other compounds" in the present invention (electrolyte [5]), use conditions, preparation method of non-aqueous electrolytic solution, etc. are the same as above.

The non-aqueous electrolytic solution for secondary batteries (electrolyte [5]) of the present invention has at least a lithium salt dissolved in a non-aqueous solvent, and such a lithium salt contains a lithium salt selected from LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and at least one of lithium bis(oxalato)borate. These may be used individually by 1 type, and may use 2 or more types together in arbitrary combinations and ratios.

In the non-aqueous electrolyte solution for secondary batteries, by using 10 ppm or more of (b) the above-mentioned "specific compound" in combination with the following (a), it is possible to provide a battery that has greatly improved output characteristics and excellent high-temperature storage characteristics or cycle characteristics. Non-aqueous electrolyte for secondary batteries.

(a) LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer of 1 to 4) and/or lithium bis(oxalato)borate

(a) is not particularly limited, but LiN(CF ₃ SO ₂ ) ₂ or lithium bis(oxalato)borate is preferable because it can particularly exert the above-mentioned effects.

In the non-aqueous electrolytic solution for secondary batteries of the present invention, as described above, LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer of 1 to 4) and/or di Lithium (oxalato)borate is an essential component, but other conventionally known lithium salts (hereinafter simply referred to as "other lithium salts") may be used in combination.

It does not specifically limit as another lithium salt, For example, the following lithium salt is mentioned.

Inorganic lithium salts: LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ and other inorganic fluoride salts; LiClO ₄ , LiBrO ₄ , LiIO ₄ and other perhalide salts; LiAlCl ₄ and other inorganic chloride salts, etc.

Fluorinated organic lithium salts: LiCF ₃ SO ₃ and other perfluoroalkane sulfonates; LiC(CF ₃ SO ₂ ) ₃ and other perfluoroalkanesulfonylmethylation salts; Li[PF ₅ (CF ₂ CF ₂ CF ₃ )], Li[PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li[PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li[PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li Fluoroalkyl fluorinated phosphates such as [PF ₄ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Li[PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ], etc.

Other lithium oxalatoborates: lithium difluorooxalatoborate, etc.

These may be used individually by 1 type, and may use 2 or more types together in arbitrary combinations and ratios. Among these "other lithium salts", LiPF ₆ and LiBF ₄ are preferred, LiPF 6 is particularly preferred if the solubility in non-aqueous solvents, charge and discharge characteristics when used as a secondary battery, output power characteristics, and cycle characteristics are comprehensively judged. ₆ .

The concentration of LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and/or bis(oxalato)lithium borate in the non-aqueous electrolyte is when these salts are used as the main salts. When used, it is usually more than 0.3 mol/L, preferably more than 0.5 mol/L, more preferably more than 0.7 mol/L, and its upper limit is usually less than 2 mol/L, preferably less than 1.8 mol/L, more preferably 1 mol/L Below L. In addition, when LiPF ₆ , LiBF ₄ and other lithium salts are used as the main salt, LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer of 1 to 4) and/or bis(oxalato ) lithium borate concentration is more than 0.001mol/L, preferably more than 0.01mol/L, more preferably more than 0.03mol/L, in addition, its upper limit is usually less than 0.3mol/L, preferably less than 0.2mol/L, more Preferably it is 0.1 mol/L or less. The main salt mentioned here refers to the lithium salt with the largest concentration in the non-aqueous electrolyte.

The total concentration of lithium salts in the non-aqueous electrolytic solution is not particularly limited, but is usually at least 0.5 mol/L, preferably at least 0.6 mol/L, and more preferably at least 0.7 mol/L. In addition, the upper limit thereof is usually 2 mol/L or less, preferably 1.8 mol/L or less, more preferably 1.7 mol/L or less. If the concentration is too low, the conductivity of the non-aqueous electrolytic solution may be insufficient. On the other hand, if the concentration is too high, the conductivity may decrease due to an increase in viscosity, and the performance of the lithium secondary battery may decrease.

A preferred example of using two or more lithium salts in combination is LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer of 1 to 4) and lithium di(oxalato)borate At least one lithium salt and LiPF ₆ are used in combination. By using them in combination, in particular, output characteristics and storage characteristics can be improved. At this time, at least one lithium salt selected from LiN(C _n F _2n+1 SO ₂ ) ₂ (in the formula, n is an integer of 1 to 4) and lithium bis(oxalato)borate in the non-aqueous electrolyte solution The concentration in Li is as follows: when these lithium salts are used as the main salt, it is preferably 0.4 mol/L or more, more preferably 0.5 mol/L or more, particularly preferably 0.6 mol/L or more. The upper limit thereof is preferably 1.8 mol/L or less, more preferably 1.5 mol/L or less, particularly preferably 1.2 mol/L or less. The concentration of LiPF ₆ at this time is preferably 0.001 mol/L or more, more preferably 0.01 mol/L or more, particularly preferably 0.1 mol/L or more. In addition, the upper limit is LiPF ₆ to at least one lithium salt selected from LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer from 1 to 4) and lithium bis(oxalato)borate. In the range where the concentration is low, it is preferably 1 mol/L or less, more preferably 0.8 mol/L or less, particularly preferably 0.3 mol/L or less.

When LiPF ₆ is used as the main salt, at least one lithium selected from LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is an integer of 1 to 4) and lithium bis(oxalato)borate The concentration of the salt is preferably 0.001 mol/L or higher, more preferably 0.01 mol/L or higher, particularly preferably 0.03 mol/L or higher. In addition, the upper limit thereof is preferably 0.3 mol/L or less, more preferably 0.2 mol/L or less, particularly preferably 0.1 mol/L or less. The concentration of LiPF ₆ at this time is preferably 0.5 mol/L or higher, more preferably 0.6 mol/L or higher, and particularly preferably 0.7 mol/L or higher. In addition, the upper limit thereof is preferably 1.8 mol/L or less, more preferably 1.7 mol/L or less, particularly preferably 1.5 mol/L or less.

In _addition , if _at least one lithium salt _{and LiPF 6} Use of LiBF ₄ in combination is preferable since it has the effect of suppressing deterioration due to high-temperature storage. At this time, the concentration of _LiBF is usually 0.001 mol/L or more, preferably 0.01 mol/L or more, more preferably 0.03 mol/L or more, and its upper limit is usually 0.4 mol/L or less, preferably 0.15 mol/L or less, More preferably, it is 0.1 mol/L or less.

Containing LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and/or bis(oxalato)lithium borate and cyclic Compounds, compounds represented by the above general formula (2), chain compounds with structures represented by general formula (3) in their molecules, compounds with SF bonds in their molecules, nitrates, nitrites, monofluorophosphates, di The non-aqueous electrolytic solution of at least one compound in the compound in fluorophosphate, acetate, propionate, due to the cycle characteristics and high-temperature storage characteristics (especially after high-temperature storage) of batteries manufactured using the non-aqueous electrolytic solution The balance between residual capacity and high-load discharge capacity) becomes excellent, so it is preferable.

Although it is not clear why the output characteristics of the nonaqueous electrolyte secondary battery using the nonaqueous electrolyte of the present invention are excellent, and the high-temperature storage stability or cycle characteristics are excellent, it is considered that the above-mentioned specific compound has a certain effect on the electrode. , Reduce the reaction resistance related to the entry and exit of lithium ions, thereby improving the output power characteristics. It is speculated that by using LiN(C _n F _2n+1 SO ₂ ) ₂ (wherein, n is an integer of 1 to 4) and/or bis(oxalato)lithium borate as lithium salts, these lithium salts are in the negative electrode and Moderately react on the surface of the positive electrode, and form a stable composite protective coating film with excellent lithium ion permeability derived from the lithium salt with other non-aqueous electrolyte components. Unnecessary side reactions of the water electrolyte, thereby improving output power characteristics, while improving high-temperature storage characteristics and cycle characteristics.

<Electrolyte [6]>

In the non-aqueous electrolytic solution, it is preferable that the lithium salt constituting the electrolytic solution is a fluorine-containing lithium salt, and that the entire non-aqueous electrolytic solution contains 10 ppm to 300 ppm of hydrogen fluoride (HF) (electrolyte solution [6]).

The types and contents of "non-aqueous solvent", "specific compound", and "other compounds" in the present invention (electrolyte [6]), use conditions, preparation method of non-aqueous electrolytic solution, etc. are the same as above. In the present invention (electrolyte solution [6]), the "fluorine-containing lithium salt" is not particularly limited as long as it is a known fluorine-containing lithium salt that can be used as an electrolyte for a non-aqueous electrolyte solution for a lithium secondary battery, for example The lithium salts mentioned above can be used. These may be used individually by 1 type, and may use 2 or more types together in arbitrary combinations and ratios. Among them, LiPF ₆ , LiBF ₄ and the like are preferable from the viewpoint of easily generating hydrogen fluoride (HF) in the presence of alcohols described later. In addition, LiPF ₆ is preferable when the solubility in non-aqueous solvents, charge and discharge characteristics when used as a secondary battery, output power characteristics, cycle characteristics, etc. are comprehensively judged.

In addition, in addition to the fluorine-containing lithium salt, a fluorine-free lithium salt may be mixed and used in the electrolytic solution, and examples thereof include the following lithium salts.

Inorganic lithium salts: LiClO ₄ , LiBrO ₄ , LiIO ₄ and other perhalide salts; LiAlCl ₄ and other inorganic chloride salts, etc.

Oxalatoborate: lithium bis(oxalato)borate, etc.

The concentration of the lithium salt in the non-aqueous electrolytic solution is not particularly limited, but is usually at least 0.5 mol/L, preferably at least 0.6 mol/L, and more preferably at least 0.7 mol/L. In addition, the upper limit thereof is usually 2 mol/L or less, preferably 1.8 mol/L or less, more preferably 1.7 mol/L or less. If the concentration is too low, the conductivity of the non-aqueous electrolytic solution may be insufficient. On the other hand, if the concentration is too high, the conductivity may decrease due to an increase in viscosity, and the performance of the lithium secondary battery may decrease.

The concentration of the fluorine-containing lithium salt in the non-aqueous electrolyte solution is not particularly limited, but is usually 0.5 mol/L or more, preferably 0.6 mol/L or more, more preferably 0.7 mol/L or more. In addition, the upper limit thereof is usually 2 mol/L or less, preferably 1.8 mol/L or less, more preferably 1.7 mol/L or less. If the concentration is too low, the conductivity of the non-aqueous electrolytic solution is sometimes insufficient or the generation of hydrogen fluoride (HF) is sometimes insufficient. On the other hand, if the concentration is too high, the conductivity is sometimes reduced or the hydrogen fluoride (HF) ) may be generated excessively, and the performance of the lithium secondary battery may decrease.

The ratio of the fluorine-containing lithium salt to the total lithium salt in the nonaqueous electrolyte is preferably 50% by mass or more, particularly preferably 70% by mass or more, based on the total lithium salt. In addition, it is particularly preferable that the mixed lithium salts are all fluorine-containing lithium salts. When the ratio of the fluorine-containing lithium salt is too low, the production of hydrogen fluoride may be insufficient.

One kind of lithium salt may be used alone, or two or more kinds may be used in combination in any combination and ratio. A preferred example when two or more kinds of lithium salts are used in combination is the combined use of _LiPF6 and _LiBF4 . At this time, _LiBF4 is in the The ratio of the total of both is preferably 0.01% by mass to 20% by mass, more preferably 0.1% by mass to 5% by mass. Another preferred example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonylimide salt. In this case, the ratio of the inorganic fluoride salt to the total of the two is preferably 70% by mass to 99% by mass. , and more preferably 80% by mass to 98% by mass. The combined use of both has an effect of suppressing deterioration due to high-temperature storage.

Hydrogen fluoride (HF) is often contained in the non-aqueous electrolytic solution obtained by dissolving a fluorine-containing lithium salt such as LiPF ₆ in the above-mentioned non-aqueous solvent. The reason for containing hydrogen fluoride (HF) is not only hydrogen fluoride derived from impurities in the fluorine-containing lithium salt, but also hydrogen fluoride produced by the reaction of a small amount of water in the non-aqueous solvent or alcohols and the fluorine-containing lithium salt. In the above-mentioned Patent Document 16, it is necessary to remove hydrogen fluoride (HF) in the non-aqueous electrolytic solution as much as possible, and it is particularly preferably 15 ppm or less. In the examples, the cycle characteristics of the non-aqueous electrolytic solution of 9 ppm are the most excellent results.

In the case of the present invention (electrolyte solution [6]), the content of hydrogen fluoride (HF) is usually 10 ppm or more, preferably 12 ppm or more, more preferably 15 ppm or more, particularly preferably 20 ppm or more, and usually 300 ppm or less, preferably It is 250 ppm or less, more preferably 200 ppm or less, particularly preferably 150 ppm or less. If the content is too low, the effect of improving output power may not be sufficient, and if the content exceeds this range, output power and cycle characteristics may be adversely affected.

In order to contain hydrogen fluoride (HF), it can be directly added to the non-aqueous electrolyte or the non-aqueous solvent of the raw material, or it can be generated inside the non-aqueous electrolyte by the reaction of water or alcohols and fluorine-containing lithium salt. Therefore, the non-aqueous electrolyte can be used A method in which water or alcohols are added to the aqueous electrolytic solution, or these components are contained in an appropriate concentration in advance in the non-aqueous solvent of the raw material. In this case, it may take a certain amount of time until the end of the reaction. In other words, when a fluorine-containing lithium salt is dissolved in a non-aqueous solvent containing water or alcohols to prepare an electrolytic solution to which a specific compound is added, it takes time until the reaction between water or alcohols and a fluorine-containing lithium salt is completed, but it is used When manufacturing batteries, there is no need to wait for the reaction to finish. In the present invention, to function as a battery, hydrogen fluoride (HF) in a specific concentration range may be present, and may be generated in the battery. When hydrogen fluoride (HF) is generated in the non-aqueous solvent of the raw material, hydrogen fluoride (HF) may be generated in a part of the non-aqueous solvent used as the raw material and mixed with a non-aqueous solvent not containing water or alcohols.

When water or alcohols are previously contained in the non-aqueous solvent, depending on the purity of the solvent used, water or alcohols may be contained in a larger than necessary amount from the beginning. In this case, it is preferable to purify the nonaqueous solvent by methods such as adsorption treatment, distillation, and crystallization to remove water or alcohols before use. The non-aqueous solvent that removes water or alcohols and leaves a predetermined amount of water or alcohols may be used as it is, or it may be used in a purified non-aqueous solvent by mixing water or alcohols in a predetermined amount.

If the adsorption treatment can be carried out in a liquid state, it can be dissolved in a non-aqueous solvent such as alumina, activated carbon, silica gel, molecular sieve (trade name) 4A and/or molecular sieve 5A or by an adsorbent that does not react with a non-aqueous solvent. Carry out purification treatment. At this time, raw materials that are liquid at normal temperature, such as dimethyl carbonate, can also be purified separately, and raw materials that are solid at normal temperature, such as ethylene carbonate, can also be mixed with other raw materials to form a liquid, and they can be purified together. . Examples of the contact method include a method of continuously immersing the non-aqueous solvent (hereinafter referred to as a continuous method), or a method of adding an adsorbent to the non-aqueous solvent and leaving it to stand or stir (hereinafter referred to as a batch method). In the case of a continuous method, the contact time is preferably 0.1 to 5 hours per hour in terms of liquid hourly space velocity (LHSV). In addition, the contact temperature is preferably 10 to 60°C. In the case of the batch method, it is preferable to add 0.1 to 30% by mass of the adsorbent to the non-aqueous solvent, and to treat for 0.25 hours to 24 hours.

In addition, raw materials that are solid at normal temperature, such as ethylene carbonate, can also be subjected to the crystallization treatment. Crystallization can be carried out using solvents such as acetonitrile, acetone, and toluene.

The purification conditions are preferably adjusted appropriately according to the type and purity of the raw material used, and the target water or alcohol content.

When the nonaqueous electrolytic solution of the present invention (electrolyte solution [6]) is prepared without adding hydrogen fluoride (HF), water or alcohols are contained in the nonaqueous solvent used for the nonaqueous electrolytic solution. That is, it is used after adding water or alcohols or is used without removing water or alcohols. Alcohols are preferably contained, especially monohydric or dihydric alcohols. The alcohol is not particularly limited, nor is the type of the alkyl group or the number of alcohols, and specific examples include methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, etc. Monohydric alcohols; dihydric alcohols such as ethylene glycol and propylene glycol; trihydric alcohols such as glycerin, and the like are preferable alcohols. Methanol, ethanol, ethylene glycol, propylene glycol, etc. are mentioned as "water or alcohols" which are especially preferable at the time of addition.

In the non-aqueous solvent for the electrolytic solution to be used, it is industrially preferable to use alcohols mixed due to reasons such as the production process, etc., from the viewpoints of productivity, cost, and the like. Particular preference is given to using methanol, ethanol, ethylene glycol or propylene glycol in the preferred non-aqueous solvents used.

In the non-aqueous solvent used in the non-aqueous electrolytic solution (electrolyte [6]) of the present invention, it is desirable that the content of water or alcohols is 3 ppm or more, preferably 10 ppm or more, more preferably 20 ppm or more, further preferably 30 ppm or more , the upper limit thereof is 150 ppm or less, preferably 130 ppm or less, more preferably 120 ppm or less, and still more preferably 100 ppm or less. If the content of water or alcohol in the non-aqueous solvent is too small, the high output characteristics characteristic of the present invention may not be sufficiently obtained, and if too large, the cycle characteristics and high-temperature storage characteristics may deteriorate.

Among them, the monohydric alcohol is preferably 5 ppm or more, more preferably 10 ppm or more, even more preferably 15 ppm or more, and preferably 100 ppm or less, more preferably 80 ppm or less, and still more preferably 50 ppm or less in the non-aqueous solvent. In addition, as glycols, in the non-aqueous solvent, it is 3 ppm or more, preferably 10 ppm or more, more preferably 15 ppm or more, still more preferably 20 ppm or more, and is preferably 100 ppm or less, more preferably 90 ppm or less, still more preferably 80 ppm or less, particularly preferably 70 ppm or less. In addition, water in the non-aqueous solvent is 3 ppm or more, preferably 5 ppm or more, more preferably 10 ppm or more, and preferably 100 ppm or less, more preferably 80 ppm or less, still more preferably 70 ppm or less.

If the above-mentioned certain amount of hydrogen fluoride (HF) and the above-mentioned specific compound coexist in the non-aqueous electrolyte solution, the output of the lithium secondary battery can be improved without adversely affecting the cycle characteristics.

The reason why the output is improved without adversely affecting cycle characteristics by coexisting a certain amount of hydrogen fluoride (HF) and a specific compound in the non-aqueous electrolyte solution of the present invention is not clear, but it is considered to be as follows. In addition, the present invention is not limited to the principle of action described below. That is, the above-mentioned specific compound is likely to have an output improving effect to some extent regardless of the content of hydrogen fluoride (HF). This is considered to be because the specific compound acts on the electrodes of the battery to lower the reaction resistance related to the entry and exit of lithium ions. Among them, hydrogen fluoride (HF) may function to enhance or transmit this effect. For example, hydrogen fluoride (HF) functions as a mediator when a specific compound and hydrogen fluoride (HF) act together on the electrode or when the specific compound acts on the electrode. In addition, it is considered that the hydrogen fluoride (HF) provided with such a function can stably exist in the battery, so that it is unlikely to cause adverse effects such as a decrease in cycle characteristics.

<Electrolyte [7]>

Among the non-aqueous electrolytic solutions, it is preferable that vinylene carbonate is contained in the electrolytic solution, and the content of the vinylene carbonate is in the range of 0.001% by mass to 3% by mass of the total mass of the electrolytic solution (electrolyte solution [7]).

The types and contents of "lithium salt", "non-aqueous solvent", "specific compound" and "other compounds" in the present invention (electrolyte [7]), use conditions, preparation method of non-aqueous electrolytic solution, etc. are the same as those mentioned above same.

The non-aqueous electrolytic solution of the present invention is characterized by containing vinylene carbonate as described above. In the present invention, the ratio of vinylene carbonate to the entire non-aqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more. Moreover, it is usually 3 mass % or less, Preferably it is 2.8 mass % or less, More preferably, it is 2.5 mass % or less. If the concentration of vinylene carbonate is too low, it may be difficult to obtain the effect of improving the cycle characteristics. On the other hand, if the concentration is too high, the low-temperature characteristics of the battery may be lowered.

The content of vinylene carbonate in the non-aqueous electrolytic solution is not particularly limited with respect to the content of the above-mentioned specific compound. It is preferably 0.01 or more, more preferably 0.1 or more, and particularly preferably 0.3 or more in terms of mass ratio. In addition, the upper limit is preferably 300 or less, more preferably 100 or less, particularly preferably 30 or less. If it deviates significantly from this range, the goals of excellent cycle characteristics and low-temperature characteristics may not be achieved at the same time.

The reason why cycle characteristics are improved even with a small amount of vinylene carbonate by using the above-mentioned specific compounds such as vinylene carbonate in combination with difluorophosphate is not clear, but it is considered that the reason is that specific compounds such as difluorophosphate The compound suppresses the amount of vinylene carbonate consumed at the positive electrode due to charge and discharge of the battery, and vinylene carbonate can form a coating film on the negative electrode without waste; and by mixing specific compounds such as difluorophosphate and vinylene carbonate , the quality of the coating film formed on the negative electrode changes, forming a thin, low-resistance high-quality coating film that can further significantly inhibit the decomposition of the electrolyte lithium salt. Thus, it is considered that improvement in low-temperature characteristics can also be achieved.

<Electrolyte [8]>

In the above-mentioned non-aqueous electrolytic solution, it is preferable that the electrolytic solution further contains compounds selected from the above-mentioned general formula (4), heterocyclic compounds containing nitrogen and/or sulfur, cyclic carboxylic acid esters, fluorine-containing cyclic carbonic acids At least one compound in the ester, and its content in the whole non-aqueous electrolytic solution ranges from 0.001% by mass to 5% by mass (electrolyte solution [8]).

The types and contents of "lithium salt", "non-aqueous solvent", "specific compound" and "other compounds" in the present invention (electrolyte [8]), use conditions, preparation method of non-aqueous electrolyte, etc. are the same as those mentioned above same.

In the non-aqueous electrolytic solution of the present invention (electrolyte [8]), it further contains a compound selected from the above general formula (4), a heterocyclic compound containing nitrogen and/or sulfur, a cyclic carboxylate, a fluorine-containing At least one compound of cyclic carbonates (hereinafter sometimes referred to simply as "specific compound B"), and its content in the entire non-aqueous electrolytic solution ranges from 0.001% by mass to 5% by mass.

[[Compound represented by general formula (4)]]

In the above general formula (4), R ⁹ to R ¹² represent groups composed of one or more elements selected from the group consisting of H, C, N, O, F, S, and P, which may be the same or different from each other.

As the presence of these atoms, specifically, hydrogen atoms, fluorine atoms, alkyl groups, cycloalkyl groups, alkenyl groups, alkynyl groups, haloalkyl groups, alkoxy groups, carbonyl groups, carbonyloxy groups, and oxycarbonyl groups are preferably present. , Oxycarbonyloxy, sulfonyl, oxysulfonyl, sulfonyloxy, phosphoryl, phosphinyl, etc. In addition, the molecular weight of the compound represented by the general formula (4) is preferably 500 or less, more preferably 300 or less, and even more preferably 200 or less.

Specific examples of the compound represented by the general formula (4) include vinyl ethylene carbonate, divinyl ethylene carbonate, methyl vinyl carbonate, ethyl vinyl carbonate, propyl vinyl carbonate, Ester, divinyl carbonate, allyl methyl carbonate, allyl ethyl carbonate, allyl propyl carbonate, diallyl carbonate and other carbonates; vinyl acetate, vinyl propionate ester, vinyl acrylate, vinyl crotonate, vinyl methacrylate, allyl acetate, allyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, methacrylic acid Esters such as ethyl ester and propyl methacrylate; divinyl sulfone, methyl vinyl sulfone, ethyl vinyl sulfone, propyl vinyl sulfone, diallyl sulfone, allyl methyl sulfone, allyl Sulfones such as ethyl ethyl sulfone and allyl propyl sulfone; Sulfites such as divinyl sulfite, methyl vinyl sulfite, ethyl vinyl sulfite, diallyl sulfite ; Vinyl methanesulfonate, vinyl ethanesulfonate, allyl methanesulfonate, allyl ethanesulfonate, methyl vinylsulfonate, ethyl vinylsulfonate and other sulfonates Classes; divinyl sulfate, methyl vinyl sulfate, ethyl vinyl sulfate, diallyl sulfate and other sulfates, etc. Among them, vinyl ethylene carbonate, divinyl ethylene carbonate, vinyl acetate, vinyl propionate, vinyl acrylate, divinyl sulfone, vinyl methanesulfonate, and the like are particularly preferable.

[[Heterocyclic compounds containing nitrogen and/or sulfur]]

The heterocyclic compound containing nitrogen and/or sulfur is not particularly limited, and examples include 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-pyrrolidone, 1,5-dimethyl-2 -pyrrolidone, 1-ethyl-2-pyrrolidone, 1-cyclohexyl-2-pyrrolidone and other pyrrolidones; 3-methyl-2-oxazolidone, 3-ethyl-2-oxazolidone, 3- Cyclohexyl-2-oxazolidinone and other oxazolidinones; 1-methyl-2-piperidone, 1-ethyl-2-piperidone and other piperidones; 1,3-dimethyl -2-imidazolinone, 1,3-diethyl-2-imidazolinone and other imidazolinones; sulfolane, 2-methylsulfolane, 3-methylsulfolane and other sulfolanes; sulfolene; ethylene Sulfites such as sulfite and propylene sulfite; 1,3-propane sultone, 1-methyl-1,3-propane sultone, 3-methyl-1,3 - sultones such as propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone, etc. Among them, 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sulfonate are particularly preferred. Acid lactone, 1,4-butene sultone, etc.

[[Cyclic carboxylate]]

The cyclic carboxylic acid ester is not particularly limited, and examples thereof include γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-enantholactone, γ-octanolactone, and γ-nonanolactone , γ-decalactone, γ-undecanolactone, γ-dodecyl lactone, α-methyl-γ-butyrolactone, α-ethyl-γ-butyrolactone, α-propyl- γ-butyrolactone, α-methyl-γ-valerolactone, α-ethyl-γ-valerolactone, α,α-dimethyl-γ-butyrolactone, α,α-dimethyl- γ-valerolactone, δ-valerolactone, δ-caprolactone, δ-octylactone, δ-nonanolide, δ-decalactone, δ-undecanolactone, δ-dodecyl lactone Esters etc. Among them, γ-butyrolactone, γ-valerolactone, and the like are particularly preferable.

[[Fluorinated cyclic carbonate]]

The fluorine-containing cyclic carbonate is not particularly limited, and examples thereof include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, and trifluoropropylene carbonate. Among them, fluoroethylene carbonate and the like are particularly preferable.

Specific compound B, that is, at least one compound selected from compounds represented by general formula (4), nitrogen- and/or sulfur-containing heterocyclic compounds, cyclic carboxylic acid esters, and fluorine-containing cyclic carbonates can be used alone One, or two or more compounds may be used in combination in any combination and ratio. In addition, in the specific compound B, even if it is a compound classified separately above, one kind may be used alone or two or more kinds of compounds may be used in combination in arbitrary combinations and ratios.

The content ratio of the specific compound B in the non-aqueous electrolyte solution to the entire non-aqueous electrolyte solution is usually 0.001% by mass or more, more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more. In addition, the upper limit thereof is usually 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less, based on the total amount. If the concentration of the specific compound B is too low, it may be difficult to obtain the effect of improving cycle characteristics and storage characteristics. On the other hand, if the concentration is too high, the charge-discharge efficiency may decrease.

Although the reason why the nonaqueous electrolyte secondary battery using the nonaqueous electrolytic solution of the present invention is excellent in low-temperature discharge characteristics and high-temperature storage characteristics or cycle characteristics is not clear, it is considered to be the following reason, but the present invention is not limited to the following effects principle. That is, it is presumed that the reason is that the specific compound B undergoes reductive decomposition on the negative electrode during initial charging, and forms a stable coating film derived from the specific compound B on the surface of the negative electrode, thereby improving storage characteristics and cycle characteristics. However, the resistance of this coating film increases significantly at low temperatures, and there is a problem that low-temperature discharge characteristics are lowered. By coexisting with specific compound A, excessive reaction of specific compound B is suppressed, and a stable composite protective coating film with excellent lithium ion permeability is formed even at low temperatures, thereby improving low-temperature discharge characteristics and improving high-temperature storage characteristics or cycle characteristics.

It is further considered that the battery element contained in one battery case of the secondary battery has a battery capacity of 3 ampere hours (Ah) or more and/or the DC resistance component of the secondary battery is 10 milliohms (Ω) In the following cases, the contribution of the DC resistance component is reduced, and the original effect of the non-aqueous electrolytic solution is more likely to be exhibited compared with a battery with a large contribution of the DC resistance component.

<Electrolyte [9]>

In the above non-aqueous electrolytic solution, it is preferable to further contain an overcharge preventing agent (electrolytic solution [9]) in the electrolytic solution.

The types and contents of "lithium salt", "non-aqueous solvent", "specific compound" and "other compounds" in the present invention (electrolyte [9]), use conditions, preparation method of non-aqueous electrolyte, etc. are the same as those mentioned above same.

The non-aqueous electrolytic solution for secondary batteries of the present invention (electrolyte solution [9]) is characterized by containing an overcharge preventing agent. Although it does not specifically limit as an overcharge inhibitor, The compound etc. which are shown by following (1), (2) or (3) are preferable.

(1) Biphenyls, terphenyls, diphenyl ethers or dibenzofurans which may be substituted by alkyl and/or fluorine atoms;

(2) Partial hydrides of terphenyls;

(3) Benzene substituted with a tertiary alkyl group, cycloalkyl group, fluorine atom and/or methoxy group.

The compound of (1) is not particularly limited, and examples thereof include benzene ring linking compounds such as biphenyl, alkylbiphenyl, and terphenyl; fluorine-containing benzene ring linking compounds such as 2-fluorobiphenyl; diphenyl ether Aromatic ethers such as dibenzofuran; aromatic heterocyclic linking compounds such as dibenzofuran, etc.

The compound of (3) is not particularly limited, and examples thereof include (cyclo)alkylbenzenes such as cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene; Atom-substituted benzenes; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and other fluorine-containing anisole class etc.

Preferable specific examples include biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, dibenzofuran and other aromatic compounds. These compounds are particularly preferable because the effect of improving the speed characteristics after high-temperature storage in the present invention is increased.

The overcharge preventing agent can be used in combination of 2 or more types. When two or more are used in combination, it is particularly preferable to use cyclohexylbenzene or terphenyl (or a partially hydrogenated product thereof) and tert-butylbenzene or tert-amylbenzene in combination.

The partial hydrogenated product of terphenyl referred to here refers to a hydrogenated product obtained by partially adding hydrogen to the double bond of the benzene ring of the terphenyl. The partial hydrogenated product of terphenyl may be a single compound or a mixture containing multiple compounds. For example, it may be a mixture of two or more partially hydrogenated terphenyls having different partial hydrogenation rates, or may be partially hydrogenated terphenyls having equal partial hydrogenation rates. In addition, the hydrogenated benzene ring may be a mixture of hydrides having different positions, a double bond position may be different, or a mixture containing structural isomers may be used.

The partial hydrogenation rate of terphenyl refers to the case where the partial hydrogenation rate at which hydrogen is not added to the double bond of the benzene ring of the terphenyl is 0%, and the complete hydrogenation product of the terphenyl, that is, when hydrogen is added to all the double bonds ( When 18 moles of hydrogen atoms are added to 1 mole of terphenyl), the partial hydrogenation rate is calculated as 100%, and in the case of a mixture, it is an average value per mole. For example, when 2 moles of hydrogen atoms are added to 1 mole of terphenyl, the partial hydrogenation rate is 11.1% (=2/18).

When the partial hydrogenation rate defined above is used, the partial hydrogenation rate of the partially hydrogenated product of terphenyl used in the present invention can take a value exceeding 0% and less than 100%. The partial hydrogenation of terphenyl can contain the complete hydrogenation of terphenyl (partial hydrogenation rate 0%), m-terphenyl (partial hydrogenation rate 100%), and the molar average partial hydrogenation rate of the mixture is preferably more than 0% and less than 100%. value. The partial hydrogenation rate of terphenyl is preferably 30 to 70%, more preferably 35 to 60%, from the standpoint of storage properties of the battery and solubility in the electrolytic solution. Moreover, although it does not specifically limit as a terphenyl or the partially hydrogenated product of terphenyl, It is especially preferable that it is a partial hydrogenated product of m-terphenyl or m-terphenyl.

The ratios of these overcharge preventing agents in the non-aqueous electrolytic solution are usually 0.01% by mass or more, preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and the upper limit is usually 5% by mass or less, preferably 3% by mass or less, particularly preferably 2% by mass or less. If it is less than the lower limit, it may not be possible to ensure sufficient safety during overcharge, and if it exceeds the upper limit, it may not be possible to form a battery with excellent storage characteristics even if it is mixed with the specific compound described below.

The reason why the deterioration of the rate characteristic after storage due to the overcharge additive is less likely to occur in the presence of the above-mentioned specific compound is not clear, but it is presumed to be as follows. In general, the overcharge preventing agent can form a polymerized coating film on the surface of the positive electrode during overcharging to greatly increase the internal resistance of the battery, or the current blocking device inside the battery can can be operated by the gas generated during the polymerization. This improves the safety of the secondary battery, etc., but even when the battery is stored at a high temperature in a charged state, a part of the polymerized coating film is formed, which causes a decrease in the discharge capacity of the battery or deterioration of the rate characteristic. If the specific compound specified in the present invention exists therein, the compound acts on the surface of the positive electrode to suppress the reaction of the overcharge preventing agent and the positive electrode active material in a normal charged state by forming a weak barrier. However, when the battery is overcharged and the positive electrode is in an excessively active state, the weak barrier is destroyed or the reaction between the positive electrode and the overcharge preventive agent is accelerated, exceeding the barrier formed by the barrier, thereby proceeding to the polymerization reaction, and the purpose of overcharging can be ensured. safety.

<Battery Design (Battery Structure)>

Next, the structure (battery structure) of the lithium secondary battery of the present invention will be described in detail.

The rechargeable lithium secondary battery of the present invention at least consists of a positive electrode and a negative electrode capable of absorbing and releasing lithium ions, the above-mentioned non-aqueous electrolyte, a microporous membrane separator arranged between the positive electrode and the negative electrode, a collector terminal and a casing And so on. Protection elements can also be installed inside and/or outside the battery as required. In addition, in this specification, the characteristic part of the structure (battery structure) of the lithium secondary battery of this invention may be called structure [1] - structure [6].

[Discharge capacity] (Structure[3])

In the lithium secondary battery of the present invention, if the capacity of the battery element contained in one battery case of the secondary battery (the capacity when the battery is discharged from a fully charged state to a discharged state) (sometimes referred to as "battery" for short) The capacity ") is 3 ampere-hours (Ah) or more, since the effect of improving output power characteristics is increased, it is preferable. Therefore, the positive plate is preferably designed to have a discharge capacity of 3 ampere hours (Ah) to 20 Ah, more preferably 4 Ah to 10 Ah under full charge (structure [3]). When it is less than 3Ah, when a large current is released, the voltage drop due to the electrode reaction resistance increases, and the power utilization factor sometimes deteriorates. On the other hand, when it is greater than 20Ah, although the electrode reaction resistance decreases and the power utilization factor becomes better, the temperature distribution formed by the internal heat generation of the battery during pulse charge and discharge is large, the durability of repeated charge and discharge is poor, and the overcharge In case of abnormality such as internal short circuit or internal short circuit, the heat release efficiency of the sudden heat is also deteriorated, the internal pressure rises, and the operation phenomenon (valve operation) of the gas release valve does not stop, so that the probability of the phenomenon (rupture) that the battery contents are ejected rapidly outward It is possible to improve

[Collector Structure] (Structure[2], Structure[4])

The current collecting structure is not particularly limited, but in order to more effectively improve the output characteristics of the lithium secondary battery of the present invention, it is necessary to form a structure that reduces the resistance of the wiring portion or the junction portion. When this internal resistance is small, the effect of using the above-mentioned non-aqueous electrolytic solution can be exhibited particularly excellently.

When the electrode group has a laminated structure described later, it is preferable to use a structure in which current collecting tabs of each electrode layer are bundled and connected to terminals. Since the internal resistance increases when the area of one electrode increases, it is preferable to provide a plurality of collector sheets in the electrode to reduce the resistance. When the electrode group has a wound structure described later, a plurality of current collector sheets are respectively provided on the positive electrode and the negative electrode, and bundled to the terminals, whereby the internal resistance can be reduced.

By optimizing the above current collecting structure, the internal resistance can be reduced as much as possible. In a battery used with a large current, the impedance measured by the 10 kHz AC method (hereinafter referred to simply as "DC resistance component") is preferably 20 milliohms (mΩ) or less, more preferably 10 milliohms (mΩ) or less, and even more preferably 5 milliohms (mΩ). Below milliohms (mΩ) (structure [2]). On the other hand, if the DC resistance component is less than 0.1 milliohm, the high output characteristics are improved, but the ratio of the current collecting structure material used increases, and the battery capacity may decrease.

In the measurement of impedance, a battery measuring device 1470 manufactured by SOLAR (Solatron) Co., Ltd. and a frequency response analyzer 1255B manufactured by SOLAR Co., Ltd. were used as the measuring device, and the resistance when an alternating current of 10 kHz was applied under a bias voltage of 5 mV was measured. , as the DC resistance component.

The above non-aqueous electrolytic solution in the present invention is effective in reducing the reaction resistance related to the entry and exit of lithium into and out of the electrode active material, and this is considered to be the main reason why excellent output characteristics can be realized. However, in a normal battery with a large DC resistance component, the effect of reducing the reaction resistance cannot be 100% reflected in the output characteristics due to the hindrance of the DC resistance component. This problem can be improved by using a battery with a small direct-current resistance component, and the effect of the present invention can be fully exhibited.

In addition, from the viewpoint of manufacturing a battery that exerts the effect of the non-aqueous electrolyte and has high output characteristics, it is particularly preferable to satisfy this condition and the above-mentioned capacitance of the battery element contained in one battery case of the secondary battery at the same time. (The capacity when the battery is discharged from the fully charged state to the discharged state) (battery capacity) is a condition of 3 ampere hours (Ah) or more.

The connection between the collector tab and the terminal is preferably joined by any one of spot welding, high-frequency welding, or ultrasonic welding (structure [4]). These soldering methods have traditionally been simple soldering methods with low resistance, but due to long-term use, the soldered part reacts with impurities or by-products in the non-aqueous electrolyte and deteriorates, increasing the DC resistance component. However, when using the above-mentioned non-aqueous electrolyte solution containing a specific compound, a stable coating film can be formed on the welded part, and in addition, the side reaction of the non-aqueous electrolyte solution in the positive electrode can be suppressed, so even when used for a long time, the welded part Deterioration is also difficult to progress, and high output power can be maintained without increasing the DC resistance component.

[Battery Case 1] (Structure 5)

The material of the battery case is not particularly limited as long as it is stable to the non-aqueous electrolytic solution used. Specifically, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys, or laminated films (laminated films) of resin and aluminum foil can be used as preferable materials. From the viewpoint of weight reduction, it is particularly preferable to use a metal or a laminated film of aluminum or an aluminum alloy.

In the present invention, when the above-mentioned non-aqueous electrolytic solution is used, it is particularly preferable to use aluminum or an aluminum alloy metal (structure [5]). Aluminum or aluminum alloy is a material with light weight and high formability, but when it is used as a battery case for a long time, it will deteriorate due to the reaction with impurities or by-products in the non-aqueous electrolyte solution. strength or opening. When using the above-mentioned non-aqueous electrolyte solution containing a specific compound, a stable coating film can be formed on the aluminum surface or the aluminum alloy surface. In addition, the side reaction of the non-aqueous electrolyte solution on the positive electrode can be suppressed, so even if it is used for a long time Deterioration is also not easy to proceed.

Cases using the above metals include cases in which metals are fused by laser welding, resistance welding, or ultrasonic welding to form a hermetically sealed structure, or cases in which the above metals are riveted with a resin gasket. Examples of the case using the above laminated film include a case in which a hermetically sealed structure is formed by thermally fusing resin layers to each other. In order to improve sealability, a resin different from the resin used in the laminated film may be present between the above-mentioned resin layers. Especially when the resin layer is thermally fused through the collector terminal to form a closed structure, since a metal-resin bond is formed, it is preferable to use a resin having a polar group or a modified resin introduced with a polar group as the resin present in the resin. resin between layers.

[Battery Case 2] (Structure[6])

In the present invention, in the case material forming the battery case, it is preferable that at least a part of the inner surface side of the battery includes a sheet formed using a thermoplastic resin, and the electrode assembly is incorporated therein, and at the same time, the thermoplastic resin layer is heat-sealed, whereby sealing can be achieved. The battery pack (structure [6]).

In order to reduce the weight of the battery, the material of the battery case in the case of structure [6] is lightweight and stable to the non-aqueous electrolyte used, and since the electrode group must be easily and reliably sealed, at least a part of the inner surface of the battery A sheet formed using a thermoplastic resin must be included.

In structure [6], the electrode group is sealed by heat-sealing the thermoplastic resin layer, wherein the so-called "heat-sealing" refers to setting the temperature above the melting point of the thermoplastic resin on the basis of making the thermoplastic resin layers adhere to each other. , bonding the thermoplastic resin layers to each other. It is preferable to use a sealing machine that has a band-shaped heat generating portion and can heat while pressurizing. In addition, thermoplastic resin is used for at least a part of the inner surface of the battery, where "at least a part" means that only the electrode group can be sealed in the outer peripheral part of the sheet, and thermoplastic resin can be used only for the heat-sealed part. From the viewpoint of the efficiency of the sheet production process, it is preferable that the entire sheet surface on the inner side of the battery is covered with a thermoplastic resin layer.

In addition, in the structure [6], when the microporous membrane separator described later has the property of clogging pores by heating, it is preferable that the casing material contains A sheet formed using a thermoplastic resin having a melting point higher than the clogging initiation temperature of pores of the microporous membrane separator. That is, when abnormal heat generation occurs during overcharging, etc., the temperature of the battery rises, and if it exceeds the melting point of the thermoplastic resin of the case material, there is a case where the battery case ruptures or electrolyte leakage occurs to cause a fire, but if the microporous membrane separator It is preferable that the pores of the microporous membrane separator be blocked by heating before the leakage of the electrolyte from the casing material occurs, and further heat generation can be suppressed, so that rupture and ignition are prevented. Here, the melting point refers to the melting temperature measured by JIS K7121.

The thermoplastic resin in the structure [6] is not particularly limited, but preferably polyolefins such as polyethylene, polypropylene, modified polyolefin, and polyolefin copolymer; polyesters such as polyethylene terephthalate ; Nylon and other polyamides, etc. One type of thermoplastic resin may be used, or two or more types may be used.

As "at least a part of the housing material" in the structure [6], only thermoplastic resin may be used, but composite materials such as thermoplastic resin and thermosetting resin, elastomer, metal material, glass fiber, carbon fiber, etc. are preferably used. In addition, fillers such as fillers may also be contained. As a composite material, a laminated sheet of a thermoplastic resin layer and a single metal such as aluminum, iron, copper, nickel, titanium, molybdenum, or gold, or an alloy such as stainless steel or Hastelloy, is more preferable and has excellent processability laminated sheets of aluminum metal. That is, it is more preferable that the casing material includes at least a laminated sheet having an aluminum layer and a thermoplastic resin layer laminated. These metals or alloys may be used as foils of metals or the like, or may be used as metal vapor-deposited films.

In the configuration [6], examples of the case using the above-mentioned case material include a case in which a resin layer is thermally fused to form a hermetically sealed structure, and the like. In order to improve sealing performance, a resin different from the resin used in the case material may exist between the above-mentioned resin layers. Especially when the resin layer is thermally fused through the collector terminal to form a closed structure, since a metal-resin bond is formed, it is preferable to use a resin having a polar group or a modified resin introduced with a polar group as the resin present in the resin. resin between layers.

In structure [6], the thickness of the casing material is not particularly limited, but is preferably 0.03 mm or more, more preferably 0.04 mm or more, and still more preferably 0.05 mm or more. In addition, the upper limit thereof is preferably 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.2 mm or less. If the casing material is thinner than this range, the strength will decrease, and it may be easily deformed, broken, etc. On the other hand, if the exterior material is thicker than this range, the weight reduction of the battery may not be achieved due to the increase in the mass of the case.

The battery of the structure [6] using the above case material has the advantages of light weight and high degree of freedom in shape. On the other hand, if gas is generated inside the battery, the internal pressure increases and the case material may be easily deformed. In the lithium secondary battery in the present invention, the specific compound in the non-aqueous electrolyte is adsorbed on the surface of the positive electrode active material, thereby suppressing the side reaction of the positive electrode and suppressing the generation of gas components. Therefore, even if the above-mentioned casing material is used, there is no It exhibits the above-mentioned disadvantages and only exhibits the above-mentioned advantages of the above-mentioned shell material, so it is preferable.

[Microporous Membrane Separator]

As long as the microporous membrane separator used in the present invention has a predetermined mechanical strength to electronically insulate between the two electrodes, has a high ion permeability, and has both resistance to oxidation on the side contacting the positive electrode and resistance to the negative electrode side. The separator is not particularly limited as long as it is a reduction-resistant separator. As the material of the microporous membrane separator having this characteristic, resin, inorganic substance, glass fiber, etc. are used.

It does not specifically limit as said resin, For example, an olefin polymer, a fluoropolymer, a cellulosic polymer, polyimide, nylon etc. are mentioned. Specifically, it is preferable to select from materials that are stable to non-aqueous electrolytes and have excellent liquid retention properties, and it is preferable to use porous sheets or nonwoven fabrics made of polyolefins such as polyethylene and polypropylene. The inorganic substance is not particularly limited, and examples thereof include oxides such as alumina and silica; nitrides such as aluminum nitride and silicon nitride; sulfates such as barium sulfate and calcium sulfate, and the like. For the shape, granular or fibrous ones can be used.

The form is preferably in the form of a film such as a nonwoven fabric, a woven fabric, or a microporous film. In the film shape, it is preferable to use a film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm. In addition to the aforementioned independent film shape, a form in which the composite porous layer containing the aforementioned inorganic particles is formed on the surface layer of the positive electrode and/or the negative electrode using a resin binder may be used. Such an aspect includes, for example, a porous layer in which 90% of alumina particles having a particle size of 1 μm or less are formed using a fluororesin as a binder on both surfaces of the positive electrode.

The microporous membrane separator used in the present invention preferably has a property of clogging pores by heating. If the above-mentioned microporous membrane separator is used in combination with an outer casing material formed using a thermoplastic resin having a melting point higher than the pore clogging initiation temperature of the microporous membrane separator at least part of the inner surface side of the battery as the outer casing material, then In the event of abnormal heat generation such as overcharging, it has the effect of stopping the heat generation before the battery case breaks or the electrolyte leaks. In addition, the "property of clogging pores by heating" mentioned here means that the porous layer that forms the electrolytic solution that can move between the positive and negative electrodes contains thermoplastic resin, and when heated to near the melting point of the thermoplastic resin, the porous layer will Blockage, the property that the electrolyte cannot move between the positive and negative electrodes.

[battery shape]

The shape of the battery is not particularly limited, and examples thereof include a cylindrical shape with a bottom, a square shape with a bottom, a thin shape, a sheet shape, and a paper shape. When assembled into a system or machine, in order to improve volumetric efficiency and storage capacity, it can also be a horseshoe shape, a comb shape, or other irregular shapes that consider the storage of peripheral systems arranged around the battery. From the viewpoint of effectively releasing heat inside the battery to the outside, a square shape having at least one relatively smooth large-area surface is preferable.

In a battery with a bottomed cylindrical shape, since the outer surface area relative to the filled power generating element is reduced, it is preferable to form a design that efficiently releases Joule heat generated by internal resistance during charging or discharging to the outside. In addition, it is preferable to design so as to increase the filling ratio of a substance with high thermal conductivity and to reduce the internal temperature distribution.

In a square shape with a bottom, it is preferable that the ratio of the area S ₁ of the largest surface (the product of the width and the height of the external dimension excluding the terminal portion, in cm ² ) to the thickness T (in cm) of the battery external shape (2×S ₁ /T) is 100 or more, more preferably 200 or more. By enlarging the maximum surface, it is possible to improve the characteristics such as cycleability and high-temperature storage even for high-output and large-capacity batteries, and at the same time, it is possible to improve the heat release efficiency when abnormal heat generation occurs, thereby suppressing the formation of "crack" or "fire". dangerous state.

[Electrode group]

The electrode group can be a laminated structure electrode group formed by sandwiching a microporous membrane separator described later between a positive electrode plate and a negative electrode plate described later, and an electrode group of a laminated structure formed by sandwiching a The microporous membrane separator is wound into any one of the spirally wound structure electrode groups. The ratio of the volume of the electrode group to the volume excluding the protrusion of the battery case (hereinafter simply referred to as "electrode group occupancy") is preferably 0.3 to 0.7, more preferably 0.4 to 0.6. When the above-mentioned electrode group occupancy ratio is less than 0.3, the battery capacity becomes small. In addition, if it exceeds 0.7, since the void space decreases, the volume necessary for the current collection structure described later cannot be sufficiently ensured, and the battery resistance may increase. In addition, due to When the battery becomes high temperature, parts expand or the vapor pressure of the liquid component of the electrolyte increases, the internal pressure increases, and there is a gas release valve that reduces various characteristics such as repeated charge and discharge performance of the battery or high temperature storage, or further releases the internal pressure to the outside. work situation.

In addition, when the electrode group has a laminated structure, the ratio (L/(2×S ₂ )) of the sum of the length L (unit cm) around the electrodes of the positive electrode and the negative electrode to twice the electrode area S ₂ (unit cm ² ) is: 1 or less, more preferably 0.5 or less, still more preferably 0.3 or less. In addition, the lower limit thereof is preferably 0.02 or more, more preferably 0.03 or more, and still more preferably 0.05 or more. In the case of a laminated structure, the adhesiveness of the electrode film may deteriorate under the impact of residual stress or cutting at the part close to the periphery of the electrode. Therefore, when L/(2×S ₂ ) exceeds the above range , the output power characteristics sometimes degrade. In addition, when L/(2×S ₂ ) is lower than the above-mentioned range, the battery area may become too large, which may not be practical.

In addition, when the electrode group has a wound structure, it is preferable that the ratio of the length in the longitudinal direction of the positive electrode to the length in the width direction is 15-200. If the ratio is less than the above range, the height of the bottomed cylindrical shape of the battery case may be too high relative to the bottom area, and the balance may deteriorate to be impractical, or the positive electrode active material layer may become thick and high output may not be obtained. In addition, if the ratio is lower than the above range, the height of the bottomed cylindrical shape of the battery case is too small relative to the bottom area, and the balance becomes poor to be practical, or the ratio of the current collector increases, and the battery capacity reduced situation.

[Positive Electrode Area] (Structure[1])

In the present invention, when the above-mentioned non-aqueous electrolytic solution is used, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery case from the viewpoint of high output and improved stability at high temperature. Specifically, from the standpoint of improving the output power and effectively releasing the heat generated by charging and discharging through the current collector, it is preferable that the sum of the electrode areas of the above-mentioned positive electrode is calculated as an area ratio with respect to the surface area of the casing of the secondary battery. It is 15 times or more, more preferably 20 times or more (Structure [1]). The outer surface area of the casing refers to the total area calculated from the dimensions of length, width and thickness of the casing portion filled with the power generating element except the protruding portion of the terminal in the case of a square shape with a bottom. In the case of a bottomed cylindrical shape, it refers to a geometrical surface area in which the part of the case filled with the power generating elements except the protruding part of the terminal is approximately a cylinder. The sum of the electrode areas of the so-called positive electrode refers to the geometric surface area of the positive electrode composite layer material layer opposite to the composite layer material layer containing the negative electrode active material. In the structure where the positive electrode composite layer material layer is formed on both sides by the current collector foil , is to calculate the sum of the areas of each surface separately.

[protection element]

Examples of the above-mentioned protection elements include PTC (positive temperature coefficient, positive temperature coefficient) whose resistance increases when abnormal heat generation or excessive current flows, temperature fuses, thermistors, battery internal pressure or internal temperature when abnormal heat generation occurs. A valve (current blocking valve), etc., which rises sharply to block the current flowing in the circuit. The above-mentioned protection element is preferably an element that does not work in normal use with high current. From the viewpoint of high output power, it is more preferable to form a design that does not generate abnormal heat or thermal runaway even if there is no protection element.

[Assembled battery]

When the lithium secondary battery of the present invention is used as a power source in practical applications, the voltage required for the power source is often higher than the voltage of the single cell, and a booster device or the like that connects the cells in series must be used accordingly. Therefore, the lithium secondary battery of the present invention is preferably used as a battery pack in which a plurality of them are connected in series. By forming a battery pack, the resistance of the connecting portion is reduced, thereby suppressing a decrease in output power as a battery pack. As the battery pack, five or more batteries are preferably connected in series in terms of power supply voltage.

In addition, when connecting a plurality of assembled batteries, since the influence of heat generated by charging and discharging increases, it is preferable to have a cooling mechanism for keeping the battery below a certain temperature. The temperature of the battery is preferably 10° C. to 40° C., and it is preferably cooled by water cooling or air cooling using outside air.

[use]

The lithium secondary battery of the present invention and a battery pack formed by connecting a plurality of lithium secondary batteries of the present invention are preferably used for loading on vehicles due to their high output power, long life, high safety, etc., and their power At least for use in a drive system of a vehicle.

In addition, it is considered that the above-mentioned specific compound can suppress a side reaction with an electrolytic solution or the like by being adsorbed on the surface of the positive electrode active material or the surface of the metal material. It is considered that by suppressing side reactions on the surface of the positive electrode active material, less gas is generated, and even if a sheet-shaped casing material is used, deformation of the battery or increase in internal pressure is less likely to occur, which is preferable. In addition, it is considered that by suppressing the side reaction on the surface of the positive electrode active material, the battery life, output power, and safety during overcharge are improved, which is advantageous for application to large batteries. In addition, it is also believed that by suppressing the side reaction on the surface of the metal material, even when a simple welding method with low resistance is used in the connection of the current collector and the terminal, the increase in the DC resistance component during long-term use is suppressed, so it is beneficial to the connection between the current collector and the terminal. applications in large batteries. In addition, lowering the reaction resistance of the positive electrode is considered to be effective for further increasing the output in a battery designed for high output such as the shape of the battery or the area of the positive electrode, and is therefore preferable.

Example

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these Examples unless the summary of this invention is exceeded.

Positive electrode[1][Positive electrode active material]

The types and physical properties of positive electrode active materials used in the following Examples and Comparative Examples are as follows.

Positive electrode [1] Table 1

[Table 1]

Positive active material BET specific surface area m²/g Average primary particle size μm Median particle size d₅₀ μm Tap density g/cm³ A 1.2 0.8 4.4 1.6 B 3.0 0.2 0.9 1.0 C 1.2 0.8 4.4 1.6 D 1.0 0.5 8.0 2.3 E 0.4 9.0 9.0 2.6

Positive electrode [1] In Table 1, as the physical properties of the positive electrode active material, BET specific surface area, average primary particle size (measured by SEM), median particle size d ₅₀ , and tap density were measured according to the method described above.

[Positive electrode active material A]

The positive electrode active material A is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ . Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co(OH) ₂ as a cobalt raw material are weighed at a molar ratio of Mn:Ni:Co=1:1:1, and pure water is added thereto to prepare For the slurry, wet pulverize the solid components in the slurry to a median particle size of 0.2 μm using a circulating medium agitation type wet bead mill while stirring.

The slurry was spray-dried by a spray dryer to obtain roughly spherical granulated particles having a particle diameter of about 5 μm and containing only manganese raw materials, nickel raw materials, and cobalt raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles, and the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials, cobalt Raw material, granulated particles of manganese raw material and mixed powder of lithium raw material. The mixed powder was sintered at 950° C. for 12 hours under air circulation (the heating and cooling rate was 5° C./min), and then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material A.

[Positive electrode active material B]

The positive electrode active material B is a lithium transition metal composite oxide synthesized in the same way as the positive electrode active material A, and is represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ , the difference is that the spray drying conditions are changed to make the particle size The granulated particles are about 1 μm, and the sintering temperature is 930°C.

[Positive electrode active material C]

The positive electrode active material C is a positive electrode active material in which a sulfur compound and an antimony compound are attached to the surface of the positive electrode active material A, synthesized by the method shown below. That is, while stirring 96.7 parts by weight of the positive electrode active material A in the flow cell, 1.3 parts by weight of an aqueous solution of lithium sulfate (Li ₂ SO ₄ H ₂ O) was sprayed thereinto in a spray form. 2.0 parts by weight of antimony trioxide (Sb ₂ O ₃ , particle median diameter: 0.8 μm) was added to the obtained mixture, and mixed well. The mixture was transferred to an alumina container, and sintered at 680° C. for 2 hours in an air atmosphere to obtain a positive electrode active material C.

[Positive electrode active material D]

The positive electrode active material D is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.04 Mn _1.84 Al _0.12 O ₄ . LiOH as a lithium raw material, _Mn2O3 as a manganese raw material, and AlOOH as an aluminum raw material were weighed at a molar ratio of Li:Mn:Al=1.04:1.84:0.12 _, and pure water was added thereto to make a slurry, while While stirring, the solid content in the slurry was wet-milled to a median particle size of 0.5 μm using a circulating medium-stirred wet bead mill.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only the lithium raw material, the manganese raw material, and the aluminum raw material. The granulated particles were sintered at 900° C. for 3 hours in nitrogen flow (heating rate was 5° C./min), then the flow gas was changed from nitrogen to air, and then sintered at 900° C. for 2 hours (temperature drop rate was 1° C./min. minute). After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material D.

[Positive electrode active material E]

The positive electrode active material E is a commercial product (lithium cobalt oxide manufactured by Nippon Chemical Industry Co., Ltd.), and is lithium cobalt oxide represented by the composition formula Li _1.03 CoO ₂ .

Positive electrode [1] embodiment 1

"Positive Production"

Mix 90% by mass of positive electrode active material A as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder in N-methylpyrrolidone solvent to prepare into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled into a thickness of 80 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the positive electrode. The density of the positive electrode active material was 2.35 g/cm ³ , and the value of (thickness of positive electrode active material layer on one side)/(thickness of current collector) was 2.2.

"The Making of Negative Pole"

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal (Timcal) company, trade name), add 100 parts by weight of aqueous dispersion of sodium carboxymethyl cellulose as a thickener (concentration of sodium carboxymethyl cellulose 1% by mass), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to make a slurry material. The obtained slurry is coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press machine, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

"Making Electrolyte"

Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 3:3:4, at 1mol/L The concentration dissolves well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"Battery Making"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of electrolytic solution was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and the battery was sealed to produce a battery. The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 20.6.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.1V to 3.0V, use a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

(Measurement method of initial output power)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) was taken as the output power (W). The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

(Cycle test (measuring method of battery capacity after endurance and output power after endurance))

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.1V with 2C constant current and constant voltage method, discharge at a constant current of 2C to the end-of-discharge voltage of 3.0V, which is regarded as a charge-discharge cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, three cycles of charging and discharging were performed at a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was used as the battery capacity after endurance. In addition, for the battery after the cycle test, the output power was measured, and it was set as the output power after durability. The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

Positive electrode [1] Example 2

It carried out similarly to positive electrode [1] Example 1 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

Positive electrode [1] Example 3

It carried out similarly to positive electrode [1] Example 1 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

Positive electrode [1] Example 4

The procedure was carried out in the same manner as in positive electrode [1] Example 1, except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

Positive electrode [1] Comparative Example 1

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, it is carried out in the same manner as the positive electrode [1] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [1].

Positive electrode [1] Table 2

[Table 2]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 1 Hexamethylcyclotrisiloxane 6.4 605 5.4 401 Example 2 Trimethylsilyl methanesulfonate 6.4 608 5.5 407 Example 3 phenyl dimethyl fluorosilane 6.4 600 5.4 398 Example 4 LiPO₂F₂ 6.4 618 5.5 415 Comparative example 1 none 6.4 525 5.1 325

Positive electrode [1] Example 5

Except using the positive electrode active material obtained by mixing the positive electrode active material A and the positive electrode active material B at a mass ratio of 2:1 as the positive electrode active material, the positive electrode [1] Example 1 was carried out in the same manner. The BET specific surface area of the mixed positive electrode active material was 1.8 m ² /g, the average primary particle size was 0.22 μm, the median particle size d ₅₀ was 3.2 μm, and the tap density was 1.5 g/cm ² . The results of the battery evaluation are shown in Table 3 of the positive electrode [1].

Positive electrode [1] Example 6

It carried out similarly to positive electrode [1] Example 5 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [1].

Positive electrode [1] Example 7

It carried out similarly to positive electrode [1] Example 5 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [1].

Positive electrode [1] Example 8

The same procedure was carried out as in Example 5 of the positive electrode [1] except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [1].

Positive electrode [1] Comparative example 2

Except that the electrolytic solution does not contain hexamethylcyclotrisiloxane, the same implementation is carried out as in the positive electrode [1] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [1].

Positive pole [1] Table 3

[table 3]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 5 Hexamethylcyclotrisiloxane 6.4 641 5.2 406 Example 6 Trimethylsilyl methanesulfonate 6.4 648 5.2 409 Example 7 phenyl dimethyl fluorosilane 6.4 637 5.1 403 Example 8 LiPO₂F₂ 6.4 657 5.2 419 Comparative example 2 none 6.4 558 4.9 328

Positive electrode [1] Example 9

Except using the positive electrode active material C as the positive electrode active material to prepare a positive electrode, it was carried out in the same manner as the positive electrode [1] Example 1. The results of the battery evaluation are shown in Table 4 of the positive electrode [1].

Positive electrode [1] Example 10

It carried out similarly to positive electrode [1] Example 9 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [1].

Positive electrode [1] Example 11

The same procedure was carried out as in positive electrode [1] Example 9 except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [1].

Positive electrode [1] Example 12

The procedure was carried out in the same manner as in positive electrode [1] Example 9 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [1].

Positive electrode [1] Comparative example 3

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, the same implementation is carried out as in Example 9 of the positive electrode [1]. The results of the battery evaluation are shown in Table 4 of the positive electrode [1].

Positive pole [1] Table 4

[Table 4]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 9 Hexamethylcyclotrisiloxane 6.4 604 5.6 412 Example 10 Trimethylsilyl methanesulfonate 6.4 609 5.6 419 Example 11 phenyl dimethyl fluorosilane 6.4 599 5.6 409 Example 12 LiPO₂F₂ 6.4 618 5.6 427 Comparative example 3 none 6.4 525 5.3 337

Positive electrode [1] Example 13

Use the positive electrode active material D as the positive electrode active material to make the positive electrode, roll it into a thickness of 108 μm with a press machine, and use 28 pieces of the positive electrode and 29 negative electrodes, except that it is made in the same way as the positive electrode [1] Example 1 Battery. (The thickness of the positive electrode active material layer on the positive electrode side/the thickness of the positive electrode current collector) was 3.1, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 18.1. The battery was evaluated in the same manner as in Example 1 of the positive electrode [1], except that the voltage range of the capacity measurement was 3.0 to 4.2 V, and the upper limit voltage of the cycle test was 4.2 V. The results of the battery evaluation are shown in Table 5 of the positive electrode [1].

Positive electrode [1] Example 14

The procedure was carried out in the same manner as in positive electrode [1] Example 13 except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [1].

Positive electrode [1] Example 15

The procedure was carried out in the same manner as in positive electrode [1] Example 13 except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [1].

Positive electrode [1] Example 16

The procedure was carried out in the same manner as in positive electrode [1] Example 13 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [1].

Positive electrode [1] Comparative example 4

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, it is carried out in the same manner as the positive electrode [1] Example 13. The results of the battery evaluation are shown in Table 5 of the positive electrode [1].

Positive pole [1] Table 5

[table 5]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 13 Hexamethylcyclotrisiloxane 5.6 792 3.5 392 Example 14 Trimethylsilyl methanesulfonate 5.6 800 3.6 398 Example 15 phenyl dimethyl fluorosilane 5.6 788 3.5 388 Example 16 LiPO₂F₂ 5.6 811 3.6 407 Comparative example 4 none 5.6 689 3.2 304

Positive electrode [1] Example 17

The positive electrode active material obtained by fully mixing the positive electrode active material D and the positive electrode active material E with a mass ratio of 2:1 is used as the positive electrode active material to make the positive electrode, and it is rolled into a thickness of 94 μm with a pressing machine, and 29 pieces of the positive electrode and the positive electrode are used. Except for 30 negative electrodes, it was carried out in the same manner as the positive electrode [1] Example 1. (The thickness of the positive electrode active material layer on the positive electrode side/the thickness of the positive electrode current collector) was 2.6, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 18.7. In addition, the mixed positive electrode active material had a BET specific surface area of 0.8 m ² /g, an average primary particle size of 0.50 μm, a median particle size d ₅₀ of 8.3 μm, and a tap density of 2.5 g/cm ³ . The results of the battery evaluation are shown in Table 6 of the positive electrode [1].

Positive electrode [1] Example 18

The same procedure as in Example 17 of the positive electrode [1] was carried out except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [1].

Positive electrode [1] Example 19

The procedure was carried out in the same manner as in positive electrode [1] Example 17, except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [1].

Positive electrode [1] Example 20

The procedure was carried out in the same manner as in positive electrode [1] Example 17, except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [1].

Positive electrode [1] Comparative example 5

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, the same implementation is carried out as in Example 17 of the positive electrode [1]. The results of the battery evaluation are shown in Table 6 of the positive electrode [1].

Positive pole [1] Table 6

[Table 6]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 17 Hexamethylcyclotrisiloxane 5.8 694 4.2 397 Example 18 Trimethylsilyl methanesulfonate 5.8 700 4.2 401 Example 19 phenyl dimethyl fluorosilane 5.8 690 4.2 393 Example 20 LiPO₂F₂ 5.8 711 4.3 411 Comparative Example 5 none 5.8 604 3.9 313

From the results in Table 2 of the positive electrode [1] to Table 6 of the positive electrode [1], it can be seen that in any positive electrode, since the electrolyte contains a specific compound, the output power and capacity retention rate are improved, and even after the cycle test , can also fully maintain the battery capacity and output power.

Positive electrode [2] [positive active material]

The types and physical properties of positive electrode active materials used in the following Examples and Comparative Examples are as follows.

Positive pole [2] Table 1

[Table 7]

Positive active material BET specific surface area m²/g Average primary particle size μm Median particle size d₅₀ μm Tap density g/cm³ A 0.6 0.7 9.0 2.1 B 3.1 0.2 0.8 1.2 C 0.6 0.7 9.0 2.1 D 0.5 0.6 10.9 2.1 E 1.0 0.5 8.0 2.3

Positive electrode [2] In Table 1, as the physical properties of the positive electrode active material, BET specific surface area, average primary particle size (measured by SEM), median particle size d ₅₀ , and tap density were measured according to the method described above.

[Positive electrode active material A]

The positive electrode active material A is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ . NiO as a nickel raw material, Co(OH) as a cobalt raw material, and AlOOH as an Al raw material were weighed at a molar ratio of Ni:Co:Al=80:15: ₅ , and pure water was added thereto to make a slurry, While stirring, the solid content in the slurry was wet-pulverized to a median particle size of 0.25 μm using a circulating medium agitation type wet bead mill.

The slurry was spray-dried with a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only nickel raw materials, cobalt raw materials, and aluminum raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles, and the ratio of the molar number of Li to the total molar number of Ni, Co and Al was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials, cobalt Raw materials, granulated particles of aluminum raw materials and mixed powder of lithium raw materials. The mixed powder was sintered at 740° C. for 6 hours under oxygen flow (the heating and cooling rate was 5° C./min), and then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material A.

[Positive electrode active material B]

The positive electrode active material B is a lithium transition metal composite oxide synthesized in the same way as the positive electrode active material A, and is represented by the composition formula Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ , and the difference is that the conditions of spray drying are changed to make Granulated particles with a particle size of about 1 μm, and a sintering temperature of 720°C.

[Positive electrode active material C]

The positive electrode active material C is a positive electrode active material in which a sulfur compound and an antimony compound are attached to the surface of the positive electrode active material A, synthesized by the method shown below. That is, while stirring 96.7 parts by weight of the positive electrode active material A in the flow cell, 1.3 parts by weight of an aqueous solution of lithium sulfate (Li ₂ SO ₄ H ₂ O) was sprayed thereinto in a spray form. 2.0 parts by weight of antimony trioxide (Sb ₂ O ₃ , particle median diameter: 0.8 μm) was added to the obtained mixture, and mixed well. The mixture was transferred to an alumina container, and sintered at 680° C. for 2 hours in an air atmosphere to obtain a positive electrode active material C.

[Positive electrode active material D]

The positive electrode active material D is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.03 Ni _0.65 Co _0.20 Mn _0.15 O ₂ . Weigh Ni(OH) ₂ as a nickel raw material, Co(OH) ₂ as a cobalt raw material, and Mn ₂ O ₃ as a manganese raw material at a molar ratio of Li:Co:Mn=65:20:15, and add Pure water was used to make a slurry, and the solid content in the slurry was wet-milled to a median particle size of 0.2 μm using a circulating medium agitation type wet bead mill while stirring.

The slurry was spray-dried with a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 12 μm and containing only nickel raw materials, cobalt raw materials, and manganese raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles, and the ratio of the molar number of Li to the total molar number of Ni, Co and Mn was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials, cobalt Raw material, granulated particles of manganese raw material and mixed powder of lithium raw material. The mixed powder was sintered at 950° C. for 12 hours under air circulation (the heating and cooling rate was 5° C./min), and then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material D.

[Positive electrode active material E]

The positive electrode active material E is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.04 Mn _1.84 Al _0.12 O ₄ . LiOH as a lithium raw material, _Mn2O3 as a manganese raw material, and AlOOH as an aluminum raw material were weighed at a molar ratio of Li:Mn:Al=1.04:1.84:0.12 _, and pure water was added thereto to make a slurry, while While stirring, the solid content in the slurry was wet-milled to a median particle size of 0.5 μm using a circulating medium-stirred wet bead mill.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only the lithium raw material, the manganese raw material, and the aluminum raw material. The granulated particles were sintered at 900° C. for 3 hours in nitrogen flow (heating rate was 5° C./min), then the flow gas was changed from nitrogen to air, and then sintered at 900° C. for 2 hours (temperature drop rate was 1° C./min. minute). After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material E.

Positive electrode [2] Example 1

"Positive Production"

Mix 90% by mass of positive electrode active material A as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder in N-methylpyrrolidone solvent to prepare into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled into a thickness of 66 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the positive electrode. The density of the positive electrode active material was 2.35 g/cm ³ , and the value of (thickness of positive electrode active material layer on one surface)/(thickness of current collector) was 1.7.

"The Making of Negative Pole"

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press machine, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

"Making Electrolyte"

Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 3:3:4, at 1mol/L The concentration dissolves well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"Battery Making"

34 sheets of positive electrodes and 35 sheets of negative electrodes were alternately arranged, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes to perform lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of electrolytic solution was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and the battery was sealed to produce a battery. The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 21.9.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.1V to 3.0V, use a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

(Measurement method of initial output power)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) was taken as the output power (W). The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

(Cycle test (measuring method of battery capacity after endurance and output power after endurance))

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.1V with 2C constant current and constant voltage method, discharge at a constant current of 2C to the end-of-discharge voltage of 3.0V, which is regarded as a charge-discharge cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, three cycles of charging and discharging were performed at a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was used as the battery capacity after endurance. In addition, for the battery after the cycle test, the output power was measured, and it was set as the output power after durability. The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

Positive electrode [2] Example 2

It carried out similarly to positive electrode [2] Example 1 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

Positive electrode [2] Example 3

The procedure was carried out in the same manner as in positive electrode [2] Example 1 except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

Positive electrode [2] embodiment 4

The procedure was carried out in the same manner as in positive electrode [2] Example 1 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

Positive electrode [2] Comparative example 1

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, it is carried out in the same manner as the positive electrode [2] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [2].

Positive pole [2] Table 2

[Table 8]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 1 Hexamethylcyclotrisiloxane 6.1 551 5.4 377 Example 2 Trimethylsilyl methanesulfonate 6.1 556 5.4 381 Example 3 phenyl dimethyl fluorosilane 6.1 545 5.3 371 Example 4 LiPO₂F₂ 6.1 563 5.4 387 Comparative example 1 none 6.1 478 5.0 303

Positive electrode [2] Example 5

Except that positive electrode active material A and positive electrode active material B were fully mixed at a mass ratio of 2:1 as the positive electrode active material, the positive electrode was made in the same manner as positive electrode [2] Example 1. The BET specific surface area of the mixed positive electrode active material was 1.4 m ² /g, the average primary particle size was 0.2 μm, the median particle size d ₅₀ was 6.3 μm, and the tap density was 1.9 g/cm ² . The results of the battery evaluation are shown in Table 3 of the positive electrode [2].

Positive electrode [2] Embodiment 6

The same procedure as in Example 5 of the positive electrode [2] was performed except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [2].

Positive electrode [2] Example 7

It carried out similarly to positive electrode [2] Example 5 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [2].

Positive electrode [2] embodiment 8

The same procedure was carried out as in Example 5 of the positive electrode [2] except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [2].

Positive electrode [2] Comparative example 2

Except that the electrolytic solution does not contain hexamethylcyclotrisiloxane, it is carried out in the same manner as the positive electrode [2] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [2].

Positive pole [2] Table 3

[Table 9]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 5 Hexamethylcyclotrisiloxane 6.1 590 5.0 375 Example 6 Trimethylsilyl methanesulfonate 6.1 596 5.0 378 Example 7 phenyl dimethyl fluorosilane 6.1 585 4.9 369 Example 8 LiPO₂F₂ 6.1 604 5.0 385 Comparative example 2 none 6.1 514 4.8 310

Positive electrode [2] embodiment 9

Except using the positive electrode active material C as the positive electrode active material to prepare a positive electrode, it was carried out in the same manner as the positive electrode [2] Example 1. The results of the battery evaluation are shown in Table 4 of the positive electrode [2].

Positive electrode [2] Example 10

The procedure was carried out in the same manner as in positive electrode [2] Example 9 except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [2].

Positive electrode [2] Example 11

The same procedure as in positive electrode [2] Example 9 was carried out except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [2].

Positive electrode [2] Example 12

The procedure was carried out in the same manner as in positive electrode [2] Example 9 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [2].

Positive electrode [2] Comparative example 3

Except that the electrolytic solution does not contain hexamethylcyclotrisiloxane, the same implementation is carried out as in the positive electrode [2] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [2].

Positive pole [2] Table 4

[Table 10]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 9 Hexamethylcyclotrisiloxane 6.1 548 5.3 374 Example 10 Trimethylsilyl methanesulfonate 6.1 555 5.4 379 Example 11 phenyl dimethyl fluorosilane 6.1 546 5.3 371 Example 12 LiPO₂F₂ 6.1 563 5.4 386 Comparative example 3 none 6.1 478 5.1 311

Positive electrode [2] Example 13

Use the positive active material D as the positive active material to make the positive pole, roll it into a thickness of 68 μm with a press, and use 34 pieces of the positive pole and 35 negative poles. In addition, it is made in the same way as the positive pole [2] Example 1 Battery. (The thickness of the positive electrode active material layer on the positive electrode side/the thickness of the positive electrode current collector) was 1.8, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 21.9. The battery was evaluated in the same manner as in Example 1 of the positive electrode [2], except that the voltage range of the capacity measurement was 3.0 to 4.2 V, and the upper limit voltage of the cycle test was 4.2 V. The results of the battery evaluation are shown in Table 5 of the positive electrode [2].

Positive electrode [2] Example 14

The same procedure as in Example 13 of the positive electrode [2] was performed except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [2].

Positive electrode [2] Example 15

The procedure was carried out in the same manner as in positive electrode [2] Example 13 except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [2].

Positive electrode [2] Example 16

The procedure was carried out in the same manner as in positive electrode [2] Example 13 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [2].

Positive electrode [2] Comparative example 4

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, the same implementation is carried out as in the positive electrode [2] Example 13. The results of the battery evaluation are shown in Table 5 of the positive electrode [2].

Positive electrode [2] Table 5

[Table 11]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 13 Hexamethylcyclotrisiloxane 6.1 580 5.0 369 Example 14 Trimethylsilyl methanesulfonate 6.1 586 5.0 374 Example 15 phenyl dimethyl fluorosilane 6.1 578 5.0 366 Example 16 LiPO₂F₂ 6.1 594 5.0 380 Comparative example 4 none 6.1 505 4.7 300

Positive electrode [2] Example 17

Use positive active material A and positive active material E to fully mix the positive active material that obtains with the mass ratio of 2: 1 as positive active material, make positive pole, be rolled into thickness with press machine and be 76 μ m, and use 32 this positive pole and Except for 33 negative electrodes, the same implementation was carried out as in Example 1 of the positive electrode [2]. (The thickness of the positive electrode active material layer on the positive electrode side/the thickness of the positive electrode current collector) was 2.0, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.6. In addition, the mixed positive electrode active material had a BET specific surface area of 0.7 m ² /g, an average primary particle size of 0.6 μm, a median particle size d ₅₀ of 8.7 μm, and a tap density of 2.2 g/cm ³ . The results of the battery evaluation are shown in Table 6 of the positive electrode [2].

Positive electrode [2] Example 18

It carried out similarly to positive electrode [2] Example 17 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [2].

Positive electrode [2] Example 19

The same procedure as in positive electrode [2] Example 17 was carried out except that the electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [2].

Positive electrode [2] Example 20

The procedure was carried out in the same manner as in positive electrode [2] Example 17, except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [2].

Positive electrode [2] Comparative example 5

Except that the electrolytic solution does not contain hexamethylcyclotrisiloxane, the same implementation is carried out as in the positive electrode [2] Example 17. The results of the battery evaluation are shown in Table 6 of the positive electrode [2].

Positive pole [2] Table 6

[Table 12]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 17 Hexamethylcyclotrisiloxane 6.0 617 4.7 381 Example 18 Trimethylsilyl methanesulfonate 6.0 623 4.7 384 Example 19 phenyl dimethyl fluorosilane 6.0 615 4.7 378 Example 20 LiPO₂F₂ 6.0 632 4.8 392 Comparative Example 5 none 6.0 538 4.6 316

From the results in Table 2 of the positive electrode [2] to Table 6 of the positive electrode [2], it can be seen that in any positive electrode, since the electrolyte contains a specific compound, the output power and capacity retention rate are improved, and even after the cycle test , can also fully maintain the battery capacity and output power.

Positive electrode [3] [positive active material]

The types and physical properties of positive electrode active materials used in the following Examples and Comparative Examples are as follows.

Positive pole [3] Table 1

[Table 13]

Positive active material BET specific surface area m²/g Average primary particle size μm Median particle size d₅₀ μm Tap density g/cm³ A 1.3 0.7 6.0 2.0 B 2.9 0.2 0.9 1.1 C 1.3 0.7 6.0 2.0 D 1.0 0.5 8.0 2.3

Positive electrode [3] In Table 1, as the physical properties of the positive electrode active material, BET specific surface area, average primary particle size (measured by SEM), median particle size d ₅₀ , and tap density were measured according to the method described above.

[Positive electrode active material A]

The positive electrode active material A is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.05 Ni _0.8 Co _0.2 O ₂ . Weigh NiO as a nickel raw material and Co(OH) ₂ as a cobalt raw material at a molar ratio of Ni:Co=80:20, and add pure water to them to make a slurry, and use a circulating medium stirring type wet type while stirring. The bead mill wet-milled the solid content in the slurry to a median particle size of 0.25 μm.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 8 μm and containing only the nickel raw material and the cobalt raw material. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles, and the ratio of the molar number of Li to the total molar number of Ni and Co was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials and cobalt raw materials. Mixed powder of granulated particles and lithium raw material. The mixed powder was sintered at 740° C. for 6 hours under oxygen flow (the heating and cooling rate was 5° C./min), and then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material A.

[Positive electrode active material B]

The positive electrode active material B is a lithium transition metal composite oxide synthesized in the same way as the positive electrode active material A, expressed by the composition formula Li _1.05 Ni _0.8 Co _0.2 O ₂ , the difference is that the spray drying conditions are changed to make the particle size The granulated particles are about 1 μm, and the sintering temperature is 720°C.

[Positive electrode active material C]

The positive electrode active material C is a positive electrode active material in which a sulfur compound and an antimony compound are attached to the surface of the positive electrode active material A, synthesized by the method shown below. That is, while stirring 96.7 parts by weight of the positive electrode active material A in the flow cell, 1.3 parts by weight of an aqueous solution of lithium sulfate (Li ₂ SO ₄ H ₂ O) was sprayed thereinto in a spray form. 2.0 parts by weight of antimony trioxide (Sb ₂ O ₃ , particle median diameter: 0.8 μm) was added to the obtained mixture, and mixed well. The mixture was transferred to an alumina container, and sintered at 680° C. for 2 hours in an air atmosphere to obtain a positive electrode active material C.

[Positive electrode active material D]

The positive electrode active material D is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.04 Mn _1.84 Al _0.12 O ₄ . LiOH as a lithium raw material, _Mn2O3 as a manganese raw material, and AlOOH as an aluminum raw material were weighed at a molar ratio of Li:Mn:Al=1.04:1.84:0.12 _, and pure water was added thereto to make a slurry, while While stirring, the solid content in the slurry was wet-milled to a median particle size of 0.5 μm using a circulating medium-stirred wet bead mill.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only the lithium raw material, the manganese raw material, and the aluminum raw material. The granulated particles were sintered at 900° C. for 3 hours in nitrogen flow (heating rate was 5° C./min), then the flow gas was changed from nitrogen to air, and then sintered at 900° C. for 2 hours (temperature drop rate was 1° C./min. minute). After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material D.

Positive electrode [3] embodiment 1

"Positive Production"

In N-methylpyrrolidone solvent, mix 90% by mass of positive electrode active material A as a positive electrode active material, 5% by mass of acetylene black as a conductive material and 5% by mass of polyvinylidene fluoride (PVdF) as a binder, Make slurry. The obtained slurry is coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled into a thickness of 65 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm and an uncoated layer with a width of 30 mm. The shape of the part is made into a positive electrode. The density of the positive electrode active material was 2.35 g/cm ³ , and the value of (thickness of positive electrode active material layer on one side)/(thickness of current collector) was 1.7.

"The Making of Negative Pole"

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press machine, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

"Making Electrolyte"

Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 3:3:4, at 1mol/L The concentration dissolves well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"Battery Making"

34 sheets of positive electrodes and 35 sheets of negative electrodes were alternately arranged, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes to perform lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of electrolytic solution was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and the battery was sealed to produce a battery. The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 21.9.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.1V to 3.0V, use a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

(Measurement method of initial output power)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) was taken as the output power (W). The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

(Cycle test (measuring method of battery capacity after endurance and output power after endurance))

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.1V with 2C constant current and constant voltage method, discharge at a constant current of 2C to the end-of-discharge voltage of 3.0V, which is regarded as a charge-discharge cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, three cycles of charging and discharging were performed at a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was used as the battery capacity after endurance. In addition, for the battery after the cycle test, the output power was measured, and it was set as the output power after durability. The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

Positive electrode [3] embodiment 2

The same procedure as in Example 1 of the positive electrode [3] was performed except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

Positive electrode [3] Example 3

It carried out similarly to positive electrode [3] Example 1 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

Positive electrode [3] embodiment 4

The same procedure was carried out as in Example 1 of the positive electrode [3] except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

Positive electrode [3] Comparative Example 1

Except that the electrolytic solution does not contain hexamethylcyclotrisiloxane, it is carried out in the same manner as the positive electrode [3] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [3].

Positive pole [3] Table 2

[Table 14]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 1 Hexamethylcyclotrisiloxane 6.5 505 4.8 290 Example 2 Trimethylsilyl methanesulfonate 6.5 509 4.8 293 Example 3 phenyl dimethyl fluorosilane 6.5 500 4.8 286 Example 4 LiPO₂F₂ 6.5 516 4.8 297 Comparative Example 1 none 6.5 438 4.7 244

Positive electrode [3] Example 5

Except using the positive electrode active material obtained by mixing the positive electrode active material A and the positive electrode active material B at a mass ratio of 2:1 as the positive electrode active material, the positive electrode [3] Example 1 was carried out in the same manner. The BET specific surface area of the mixed positive electrode active material was 1.8 m ² /g, the average primary particle size was 0.2 μm, the median particle size d ₅₀ was 4.3 μm, and the tap density was 1.8 g/cm ² . The results of the battery evaluation are shown in Table 3 of the positive electrode [3].

Positive electrode [3] embodiment 6

It carried out similarly to positive electrode [3] Example 5 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [3].

Positive electrode [3] Example 7

It carried out similarly to positive electrode [3] Example 5 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [3].

Positive electrode [3] embodiment 8

The procedure was carried out in the same manner as in positive electrode [3] Example 5, except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [3].

Positive electrode [3] Comparative example 2

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, it is carried out in the same manner as the positive electrode [3] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [3].

Positive pole [3] Table 3

[Table 15]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 5 Hexamethylcyclotrisiloxane 6.5 524 4.6 288 Example 6 Trimethylsilyl methanesulfonate 6.5 529 4.6 290 Example 7 phenyl dimethyl fluorosilane 6.5 519 4.6 284 Example 8 LiPO₂F₂ 6.5 536 4.6 294 Comparative example 2 none 6.5 456 4.6 247

Positive electrode [3] embodiment 9

Except using the positive electrode active material C as the positive electrode active material to prepare a positive electrode, it was carried out in the same manner as the positive electrode [3] Example 1. The results of the battery evaluation are shown in Table 4 of the positive electrode [3].

Positive electrode [3] Example 10

The procedure was carried out in the same manner as in positive electrode [3] Example 9 except that the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [3].

Positive electrode [3] Example 11

It carried out similarly to positive electrode [3] Example 9 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [3].

Positive electrode [3] Example 12

The procedure was carried out in the same manner as in positive electrode [3] Example 9 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [3].

Positive electrode [3] Comparative example 3

Except that the electrolytic solution does not contain hexamethylcyclotrisiloxane, the same implementation is carried out as in the positive electrode [3] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [3].

Positive pole [3] Table 4

[Table 16]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 9 Hexamethylcyclotrisiloxane 6.5 503 4.2 252 Example 10 Trimethylsilyl methanesulfonate 6.5 509 4.2 255 Example 11 phenyl dimethyl fluorosilane 6.5 500 4.2 251 Example 12 LiPO₂F₂ 6.5 516 4.2 259 Comparative example 3 none 6.5 438 4.2 217

Positive electrode [3] Example 13

Use positive active material A and positive active material D to fully mix the positive active material that obtains with the mass ratio of 2: 1 as positive active material, make positive pole, be rolled into thickness with pressing machine and be 74 μ m, and use 32 this positive pole and Except for 33 negative electrodes, the same implementation was carried out as in Example 1 of the positive electrode [3]. (The thickness of the positive electrode active material layer on the positive electrode side/the thickness of the positive electrode current collector) was 2.0, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.6. The BET specific surface area of the mixed positive electrode active material was 1.2 m ² /g, the average primary particle size was 0.6 μm, the median particle size d ₅₀ was 6.7 μm, and the tap density was 2.2 g/cm ² . The results of the battery evaluation are shown in Table 5 of the positive electrode [3].

Positive electrode [3] Example 14

It carried out similarly to positive electrode [3] Example 13 except having made electrolytic solution contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [3].

Positive electrode [3] Example 15

It carried out similarly to positive electrode [3] Example 13 except having made electrolytic solution contain 0.3 mass % of phenyldimethylfluorosilanes instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [3].

Positive electrode [3] Example 16

The procedure was carried out in the same manner as in positive electrode [3] Example 13 except that the electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [3].

Positive electrode [3] Comparative example 4

Except that hexamethylcyclotrisiloxane is not contained in the electrolytic solution, it is carried out in the same manner as the positive electrode [3] Example 13. The results of the battery evaluation are shown in Table 5 of the positive electrode [3].

Positive pole [3] Table 5

[Table 17]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 13 Hexamethylcyclotrisiloxane 6.1 631 4.3 346 Example 14 Trimethylsilyl methanesulfonate 6.1 637 4.3 350 Example 15 phenyl dimethyl fluorosilane 6.1 628 4.3 344 Example 16 LiPO₂F₂ 6.1 645 4.3 354 Comparative example 4 none 6.1 549 4.3 297

From the results in Table 2 of positive electrode [3] to Table 5 of positive electrode [3], it can be seen that in any positive electrode, since specific compounds are contained in the electrolyte, the output power and capacity retention rate are improved, and even after the cycle test , can also fully maintain the battery capacity and output power.

Positive electrode [4] [positive electrode active material]

The types and physical properties of positive electrode active materials used in the following Examples and Comparative Examples are as follows.

Positive pole [4] Table 1

[Table 18] positive active material BET specific surface area m²/g Average primary particle size μm Median particle size d₅₀ μm Tap density g/cm³ A 1.1 0.9 7.0 2.1 B 3.2 0.2 0.8 1.0 C 1.1 0.9 7.0 2.1 D. 1.0 0.5 8.0 2.3

Positive electrode [4] In Table 1, as the physical properties of the positive electrode active material, BET specific surface area, average primary particle size (measured by SEM), median particle size d ₅₀ , and tap density were measured according to the method described above.

[Positive electrode active material A]

The positive electrode active material A is a lithium-cobalt composite oxide synthesized by the method shown below and represented by the composition formula LiCoO ₂ . Weigh LiOH as a lithium raw material and Co(OH) ₂ as a cobalt raw material at a molar ratio of Li:Co=1:1, add pure water to them to make a slurry, and use a circulating medium stirring type wet type while stirring. The bead mill wet-milled the solid content in the slurry to a median particle size of 0.2 μm.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 9 μm and containing only the lithium raw material and the cobalt raw material. The granulated particles were sintered at 880° C. for 6 hours under air circulation (the heating and cooling rate was 5° C./minute). After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material A.

[Positive electrode active material B]

The positive electrode active material B is a lithium transition metal composite oxide synthesized in the same way as the positive electrode active material A, expressed by the composition formula _LiCoO2 , the difference is that the spray drying conditions are changed to make granulated particles with a particle diameter of about 1 μm , and the sintering temperature is 860°C.

[Positive electrode active material C]

The positive electrode active material C is a positive electrode active material in which a sulfur compound and an antimony compound are attached to the surface of the positive electrode active material A, synthesized by the method shown below. That is, while stirring 96.7 parts by weight of the positive electrode active material A in the flow cell, 1.3 parts by weight of an aqueous solution of lithium sulfate (Li ₂ SO ₄ H ₂ O) was sprayed thereinto in a spray form. 2.0 parts by weight of antimony trioxide (Sb ₂ O ₃ , particle median diameter: 0.8 μm) was added to the obtained mixture, and mixed well. The mixture was transferred to an alumina container, and sintered at 680° C. for 2 hours in an air atmosphere to obtain a positive electrode active material C.

[Positive electrode active material D]

The positive electrode active material D is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula Li _1.04 Mn _1.84 Al _0.12 O ₄ . LiOH as a lithium raw material, _Mn2O3 as a manganese raw material, and AlOOH as an aluminum raw material were weighed at a molar ratio of Li:Mn:Al=1.04:1.84:0.12 _, and pure water was added thereto to make a slurry, while While stirring, the solid content in the slurry was wet-milled to a median particle size of 0.5 μm using a circulating medium-stirred wet bead mill.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only the lithium raw material, the manganese raw material, and the aluminum raw material. The granulated particles were sintered at 900° C. for 3 hours in nitrogen flow (heating rate was 5° C./min), then the flow gas was changed from nitrogen to air, and then sintered at 900° C. for 2 hours (temperature drop rate was 1° C./min. minute). After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material D.

Positive pole [4] embodiment 1

"Positive Production"

Mix 85% by mass of positive electrode active material A as a positive electrode active material, 10% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder in N-methylpyrrolidone solvent to prepare into slurry. The obtained slurry is coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled into a thickness of 85 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm and an uncoated layer with a width of 30 mm. The shape of the part is made into a positive electrode. The density of the positive electrode active material was 2.35 g/cm ³ , and the value of (thickness of positive electrode active material layer on one side)/(thickness of current collector) was 2.3.

"The Making of Negative Pole"

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press machine, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

"Preparation of Non-Aqueous Electrolyte"

Under a dry argon atmosphere, in a 3:3:4 (volume ratio) mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), with 1mol /L concentration dissolves well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"Battery Making"

31 positive electrodes and 32 negative electrodes were alternately arranged, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and the battery was sealed to produce a battery. The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the case of the battery was 20.0.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

(Measurement method of initial output power)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) was taken as the output power (W). The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

(Cycle test (measuring method of battery capacity after endurance and output power after endurance))

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.2V by 2C constant current and constant voltage method, discharge to the end-of-discharge voltage of 3.0V with a constant current of 2C, which is regarded as a charge-discharge cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, three cycles of charging and discharging were performed at a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was used as the battery capacity after endurance. In addition, for the battery after the cycle test, the output power was measured, and it was set as the output power after durability. The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

Positive pole [4] embodiment 2

The non-aqueous electrolytic solution was carried out in the same manner as in Example 1 of positive electrode [4] except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

Positive electrode [4] Example 3

The non-aqueous electrolytic solution was carried out in the same manner as the positive electrode [4] Example 1 except that 0.3% by mass of phenyldimethylfluorosilane was contained instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

Positive electrode [4] embodiment 4

The non-aqueous electrolytic solution was made to contain 0.3 mass % of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

Positive electrode [4] Comparative example 1

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, it is carried out in the same manner as the positive electrode [4] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [4].

Positive electrode [4] Table 2

[Table 19]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 1 Hexamethylcyclotrisiloxane 5.9 530 4.2 296 Example 2 Trimethylsilyl methanesulfonate 5.9 535 4.2 299 Example 3 phenyl dimethyl fluorosilane 5.9 524 4.2 292 Example 4 LiPO₂F₂ 5.9 541 4.3 303 Comparative example 1 none 5.9 460 4.2 249

Positive electrode [4] embodiment 5

Except for using the positive electrode active material B as the positive electrode active material to prepare a positive electrode, the same implementation was carried out as in the positive electrode [4] Example 1. The results of the battery evaluation are shown in Table 3 of the positive electrode [4].

Positive electrode [4] embodiment 6

The nonaqueous electrolytic solution was made to contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [4].

Positive electrode [4] embodiment 7

The non-aqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [4].

Positive electrode [4] embodiment 8

The non-aqueous electrolytic solution was made to contain 0.3 mass % of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [4].

Positive electrode [4] Comparative example 2

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, it is carried out in the same manner as the positive electrode [4] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [4].

Positive electrode [4] Table 3

[Table 20]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 5 Hexamethylcyclotrisiloxane 5.9 584 3.6 276 Example 6 Trimethylsilyl methanesulfonate 5.9 590 3.6 277 Example 7 phenyl dimethyl fluorosilane 5.9 579 3.6 272 Example 8 LiPO₂F₂ 5.9 598 3.6 281 Comparative example 2 none 5.9 509 3.6 236

Positive electrode [4] embodiment 9

The positive electrode active material obtained by fully mixing the positive electrode active material A and the positive electrode active material B at a mass ratio of 2:1 was used as the positive electrode active material to make a positive electrode, except that it was carried out in the same manner as the positive electrode [4] Example 1. The mixed positive electrode active material had a BET specific surface area of 1.8 m ² /g, an average primary particle size of 0.2 μm, a median particle size d ₅₀ of 4.9 μm, and a tap density of 1.8 g/cm ³ . The battery evaluation results are shown in Table 4 of the positive electrode [4].

Positive electrode [4] Example 10

The non-aqueous electrolytic solution was carried out in the same manner as in positive electrode [4] Example 9 except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [4].

Positive electrode [4] Example 11

The non-aqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [4].

Positive electrode [4] Example 12

The non-aqueous electrolytic solution was made to contain 0.3 mass % of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [4].

Positive electrode [4] Comparative Example 3

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, it is carried out in the same manner as the positive electrode [4] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [4].

Positive electrode [4] Table 4

[Table 21]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 9 Hexamethylcyclotrisiloxane 5.9 546 4.0 291 Example 10 Trimethylsilyl methanesulfonate 5.9 553 4.0 295 Example 11 phenyl dimethyl fluorosilane 5.9 544 4.0 289 Example 12 LiPO₂F₂ 5.9 560 4.0 299 Comparative example 3 none 5.9 476 4.0 250

Positive electrode [4] Example 13

Except for using the positive electrode active material C as the positive electrode active material to prepare a positive electrode, the same implementation was carried out as in the positive electrode [4] Example 1. The results of the battery evaluation are shown in Table 5 of the positive electrode [4].

Positive electrode [4] Example 14

The non-aqueous electrolytic solution was carried out in the same manner as in positive electrode [4] Example 13 except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [4].

Positive electrode [4] Example 15

The same procedure was carried out as in Example 13 of the positive electrode [4], except that the nonaqueous electrolyte contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [4].

Positive electrode [4] Example 16

The same procedure as in Example 13 of the positive electrode [4] was carried out except that the nonaqueous electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [4].

Positive electrode [4] Comparative example 4

Except not containing hexamethylcyclotrisiloxane in the non-aqueous electrolytic solution, the same implementation was carried out as in the positive electrode [4] Example 13. The results of the battery evaluation are shown in Table 5 of the positive electrode [4].

Positive electrode [4] Table 5

[Table 22]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 13 Hexamethylcyclotrisiloxane 5.9 529 4.3 303 Example 14 Trimethylsilyl methanesulfonate 5.9 535 4.3 306 Example 15 phenyl dimethyl fluorosilane 5.9 527 4.3 301 Example 16 LiPO₂F₂ 5.9 541 4.3 310 Comparative example 4 none 5.9 460 4.3 260

Positive electrode [4] Example 17

Use positive active material A and positive active material D to fully mix the positive active material that obtains with the mass ratio of 2: 1 as positive active material, make positive pole, be rolled into thickness 92 μ m with pressing machine, and use 30 this positive pole and 31 The sheet negative electrode was carried out in the same manner as in Example 1 of the positive electrode [4] except for this. (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 2.6, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 19.4. In addition, the mixed positive electrode active material had a BET specific surface area of 1.1 m ² /g, an average primary particle size of 0.6 μm, a median particle size d ₅₀ of 7.3 μm, and a tap density of 2.2 g/cm ³ . The battery evaluation results are shown in Table 6 of the positive electrode [4].

Positive electrode [4] Example 18

The non-aqueous electrolytic solution was carried out in the same manner as in positive electrode [4] Example 17, except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [4].

Positive electrode [4] Example 19

The non-aqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [4] Example 17. The results of the battery evaluation are shown in Table 6 of the positive electrode [4].

Positive electrode [4] Example 20

The same procedure as in Example 17 of the positive electrode [4] was carried out except that the nonaqueous electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [4].

Positive electrode [4] Comparative Example 5

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolytic solution, the same implementation is carried out as in the positive electrode [4] Example 17. The results of the battery evaluation are shown in Table 6 of the positive electrode [4].

Positive pole [4] Table 6

[Table 23]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 17 Hexamethylcyclotrisiloxane 5.7 624 3.9 333 Example 18 Trimethylsilyl methanesulfonate 5.7 629 3.9 335 Example 19 phenyl dimethyl fluorosilane 5.7 621 3.9 330 Example 20 LiPO₂F₂ 5.7 639 3.9 341 Comparative Example 5 none 5.7 543 3.9 285

From the results in Table 2 of the positive electrode [4] to Table 6 of the positive electrode [4], it can be seen that in any positive electrode, the initial output power is improved due to the specific compound contained in the non-aqueous electrolyte. In addition, the capacity retention rate is improved, and the battery capacity and output power can be fully maintained even after a cycle test.

Positive electrode [5] [positive electrode active material]

The types and physical properties of positive electrode active materials used in the following Examples and Comparative Examples are as follows.

Positive electrode [5] Table 1

[Table 24]

Positive active material BET specific surface area m²/g Average primary particle size μm Median particle size d₅₀ μm Tap density g/cm³ A 1.1 0.9 7.0 2.1 B 1.3 0.7 6.0 2.0 C 0.6 0.7 9.0 2.1 D 0.6 0.7 9.0 2.1 E 1.2 0.8 4.4 1.6 F 1.0 0.5 8.0 2.3

In positive pole [5] table 1, as the physical property of positive pole active material, according to the method described above, carry out BET specific surface area, average primary particle diameter (measure with SEM), median diameter d ₅₀ , tap density Determination.

[Positive electrode active material A]

The positive electrode active material A is a lithium-cobalt composite oxide synthesized by the method shown below and represented by the composition formula LiCoO ₂ . Weigh LiOH as a lithium raw material and Co(OH) ₂ as a cobalt raw material at a molar ratio of Li:Co=1:1, add pure water to them to make a slurry, and use a circulating medium stirring type wet type while stirring. The bead mill wet-milled the solid content in the slurry to a median particle size of 0.2 μm.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 9 μm and containing only the lithium raw material and the cobalt raw material. The granulated particles were sintered at 880° C. for 6 hours under air circulation (the heating and cooling rate was 5° C./minute). After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material A.

[Positive electrode active material B]

The positive electrode active material B is a lithium transition metal composite oxide synthesized by the following method, represented by the composition formula Li _1.05 Ni _0.80 Co _0.2 O ₂ . Weigh NiO as a nickel raw material and Co(OH) ₂ as a cobalt raw material at a molar ratio of Ni:Co=80:20, and add pure water to them to make a slurry, and use a circulating medium stirring type wet type while stirring. The bead mill wet-milled the solid content in the slurry to a median particle size of 0.25 μm.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 8 μm and containing only the nickel raw material and the cobalt raw material. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles so that the ratio of the number of moles of Li to the total number of moles of Ni and Co was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials and cobalt raw materials. Mixed powder of granulated particles and lithium raw material. The mixed powder was sintered at 740° C. for 6 hours under oxygen flow (the heating and cooling rate was 5° C./min), then pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material B.

[Positive electrode active material C]

The positive electrode active material C is a lithium transition metal composite oxide synthesized by the following method, represented by the composition formula Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ . NiO as a nickel raw material, Co(OH) as a cobalt raw material, _and AlOOH as an aluminum raw material were weighed at a molar ratio of Ni:Co:Al=80:15:5, and pure water was added thereto to make a slurry, while While stirring, the solid content in the slurry was wet-milled to a median particle size of 0.25 μm using a circulating medium-stirred wet bead mill.

The slurry was spray-dried with a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only nickel raw materials, cobalt raw materials, and aluminum raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles so that the ratio of the number of moles of Li to the total number of moles of Ni, Co, and Al was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials, cobalt Raw materials, granulated particles of aluminum raw materials and mixed powder of lithium raw materials. The mixed powder was sintered at 740° C. for 6 hours under oxygen flow (the heating and cooling rate was 5° C./min), and then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material C.

[Positive electrode active material D]

The positive electrode active material C is a positive electrode active material in which a sulfur compound and an antimony compound are adhered to the surface of the positive electrode active material C by the method shown below. That is, while stirring 96.7 parts by weight of the positive electrode active material C in the flow cell, 1.3 parts by weight of an aqueous solution of lithium sulfate (Li ₂ SO ₄ H ₂ O) was sprayed thereinto in a spray form. 2.0 parts by weight of antimony trioxide (Sb ₂ O ₃ , particle median diameter: 0.8 μm) was added to the obtained mixture, and mixed well. The mixture was transferred to an alumina container, and sintered at 680° C. for 2 hours in an air atmosphere to obtain a positive electrode active material D.

[Positive electrode active material E]

The positive electrode active material E is a lithium transition metal composite oxide synthesized by the following method, represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ . Weigh Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co(OH) ₂ as a cobalt raw material at a molar ratio of Mn:Ni:Co=1:1:1, and add pure water to make a slurry While stirring, the solid components in the slurry were wet pulverized into a median particle size of 0.2 μm using a circulating medium agitation wet bead mill.

The slurry was spray-dried by a spray dryer to obtain roughly spherical granulated particles having a particle diameter of about 5 μm and containing only manganese raw materials, nickel raw materials, and cobalt raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles so that the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co was 1.05, and mixed with a high-speed mixer to obtain manganese raw materials, nickel Raw material, granulated particles of cobalt raw material and mixed powder of lithium raw material. The mixed powder was sintered at 950° C. for 12 hours under oxygen flow (the heating and cooling rate was 5° C./min), and then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material E.

[Positive electrode active material F]

The positive electrode active material F is a lithium transition metal composite oxide synthesized by the following method, represented by the composition formula Li _1.04 Mn _1.84 Al _0.12 O ₄ . Weigh LiOH as a lithium raw material, _Mn2O3 as a manganese raw material, and AlOOH as an aluminum raw material at a molar ratio of Li:Mn:Al=1.04:1.84:0.12, add pure water to them to make _a slurry, and stir The solid content in the slurry was wet pulverized to a median particle size of 0.5 μm while using a circulating medium agitation type wet bead mill.

The slurry was spray-dried by a spray dryer to obtain approximately spherical granulated particles having a particle diameter of about 10 μm and containing only the lithium raw material, the manganese raw material and the aluminum raw material. The granulated particles obtained were sintered at 900°C under nitrogen flow (the rate of temperature rise and fall was 5°C/min) for 3 hours, then the flow gas was changed from nitrogen to air, and then sintered at 900°C (the rate of temperature drop was 1°C). °C/min) for 2 hours. After cooling to room temperature, it was taken out and pulverized, and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material F.

Positive pole [5] embodiment 1

"Positive Production"

The positive electrode active material A and the negative electrode active material B were fully mixed at a mass ratio of 1:1, and the obtained positive electrode active material was used to prepare a positive electrode. The mixed positive electrode active material had a BET specific surface area of 1.2 m ² /g, an average primary particle size of 0.8 μm, a median particle size d ₅₀ of 6.5 μm, and a tap density of 2.1 g/cm ³ .

In N methylpyrrolidone solvent, mix 90% by mass of the above-mentioned mixed positive electrode active material A, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder to form slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled into a thickness of 70 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm and an uncoated layer with a width of 30 mm. The shape of the part is made into a positive electrode. The density of the positive electrode active material was 2.35 g/cm ³ , and the value of (thickness of positive electrode active material layer on one side)/(thickness of current collector) was 1.8.

"The Making of Negative Pole"

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press machine, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

"Preparation of Non-Aqueous Electrolyte"

Under a dry argon atmosphere, in a 3:3:4 (volume ratio) mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC), with 1mol /L concentration dissolves well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"Battery Making"

33 positive electrodes and 34 negative electrodes were alternately arranged, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and the battery was sealed to produce a battery. The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 21.3.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

(Measurement method of initial output power)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) was taken as the output power (W). The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

(Cycle test (measuring method of battery capacity after endurance and output power after endurance))

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.2V by 2C constant current and constant voltage method, discharge to the end-of-discharge voltage of 3.0V with a constant current of 2C, which is regarded as a charge-discharge cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, three cycles of charging and discharging were performed at a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was used as the battery capacity after endurance. In addition, for the battery after the cycle test, the output power was measured, and it was set as the output power after durability. The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

Positive pole [5] embodiment 2

The non-aqueous electrolytic solution was carried out in the same manner as in Example 1 of the positive electrode [5] except that 0.3% by mass of trimethylsilyl methanesulfonate was contained instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

Positive electrode [5] Example 3

The nonaqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

Positive electrode [5] embodiment 4

The non-aqueous electrolytic solution was made to contain 0.3 mass % of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

Positive electrode [5] Comparative Example 1

Except not containing hexamethylcyclotrisiloxane in the non-aqueous electrolytic solution, it was carried out in the same manner as the positive electrode [5] Example 1. The results of the battery evaluation are shown in Table 2 of the positive electrode [5].

Positive electrode [5] Table 2

[Table 25]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 1 Hexamethylcyclotrisiloxane 6.3 539 4.6 309 Example 2 Trimethylsilyl methanesulfonate 6.3 544 4.6 311 Example 3 phenyl dimethyl fluorosilane 6.3 534 4.6 305 Example 4 LiPO₂F₂ 6.3 551 4.6 315 Comparative example 1 none 6.3 468 4.6 264

Positive electrode [5] embodiment 5

The positive active material obtained by using the positive active material A and the positive active material E in a mass ratio of 1:1 is fully mixed as the positive active material to make a positive electrode, which is rolled into a thickness of 78 μm with a pressing machine, and 32 pieces of the positive electrode and 33 are used. The sheet negative electrode was carried out in the same manner as in Example 1 of the positive electrode [5] except for this. (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 2.1, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.6. The mixed positive electrode active material had a BET specific surface area of 1.2 m ² /g, an average primary particle size of 0.8 μm, a median particle size d ₅₀ of 5.7 μm, and a tap density of 2.0 g/cm ³ . The battery evaluation results are shown in Table 3 of the positive electrode [5].

Positive electrode [5] Embodiment 6

The nonaqueous electrolytic solution was carried out in the same manner as in positive electrode [5] Example 5 except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 3 of the positive electrode [5].

Positive electrode [5] embodiment 7

The nonaqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [5].

Positive electrode [5] embodiment 8

The non-aqueous electrolytic solution was made to contain 0.3 mass % of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [5].

Positive electrode [5] Comparative example 2

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, it is carried out in the same manner as the positive electrode [5] Example 5. The results of the battery evaluation are shown in Table 3 of the positive electrode [5].

Positive electrode [5] Table 3

[Table 26]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 5 Hexamethylcyclotrisiloxane 6.1 589 5.0 377 Example 6 Trimethylsilyl methanesulfonate 6.1 595 5.0 379 Example 7 phenyl dimethyl fluorosilane 6.1 584 5.0 370 Example 8 LiPO₂F₂ 6.1 604 5.0 387 Comparative example 2 none 6.1 513 4.7 305

Positive electrode [5] embodiment 9

Use the positive active material obtained by fully mixing the positive active material A and the positive active material F with a mass ratio of 1:1 as the positive active material to make the positive pole, roll it into a thickness of 91 μm with a pressing machine, and use 30 pieces of the positive pole and 31 The sheet negative electrode was carried out in the same manner as in Example 1 of the positive electrode [5] except for this. (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 2.5, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 19.4. The BET specific surface area of the mixed positive electrode active material was 1.0 m ² /g, the average primary particle size was 0.6 μm, the median particle size d ₅₀ was 7.5 μm, and the tap density was 2.2 g/cm ³ . The battery evaluation results are shown in Table 4 of the positive electrode [5].

Positive electrode [5] Example 10

The non-aqueous electrolytic solution was carried out in the same manner as in positive electrode [5] Example 9 except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 4 of the positive electrode [5].

Positive electrode [5] Example 11

The nonaqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [5].

Positive electrode [5] Example 12

The non-aqueous electrolytic solution was made to contain 0.3 mass % of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [5].

Positive electrode [5] Comparative Example 3

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, it is carried out in the same manner as the positive electrode [5] Example 9. The results of the battery evaluation are shown in Table 4 of the positive electrode [5].

Positive electrode [5] Table 4

[Table 27]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 9 Hexamethylcyclotrisiloxane 5.7 679 4.2 390 Example 10 Trimethylsilyl methanesulfonate 5.7 687 4.2 397 Example 11 phenyl dimethyl fluorosilane 5.7 675 4.2 387 Example 12 LiPO₂F₂ 5.7 696 4.3 404 Comparative example 3 none 5.7 592 3.9 313

Positive electrode [5] Example 13

Use the positive active material obtained by fully mixing the positive active material C and the positive active material E with a mass ratio of 1:1 as the positive active material to make the positive electrode, and roll it into a thickness of 72 μm with a press machine. Use 33 pieces of the positive electrode and 34 pieces The negative electrode was carried out in the same manner as in Example 1 of the positive electrode [5] except for this. The mixed positive electrode active material had a BET specific surface area of 0.9 m ² /g, an average primary particle size of 0.7 μm, a median particle size d ₅₀ of 6.7 μm, and a tap density of 2.0 g/cm ³ . (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 1.9, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 21.3. The battery was evaluated in the same manner as in Example 1 of the positive electrode [5], except that the voltage range in the capacity measurement was 3.0 to 4.1 V, and the upper limit voltage in the cycle test was 4.1 V. The battery evaluation results are shown in Table 5 of the positive electrode [5].

Positive electrode [5] Example 14

The non-aqueous electrolytic solution was carried out in the same manner as in Example 13 of the positive electrode [5] except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [5].

Positive electrode [5] Example 15

The same procedure was carried out as in Example 13 of the positive electrode [5] except that the nonaqueous electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [5].

Positive electrode [5] Example 16

The procedure was carried out in the same manner as in Example 13 of the positive electrode [5] except that the nonaqueous electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 5 of the positive electrode [5].

Positive electrode [5] Comparative example 4

Except not containing hexamethylcyclotrisiloxane in the non-aqueous electrolytic solution, the same implementation was carried out as in Example 13 of the positive electrode [5]. The results of the battery evaluation are shown in Table 5 of the positive electrode [5].

Positive electrode [5] Table 5

[Table 28]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 13 Hexamethylcyclotrisiloxane 6.3 578 5.5 397 Example 14 Trimethylsilyl methanesulfonate 6.3 584 5.6 402 Example 15 phenyl dimethyl fluorosilane 6.3 576 5.5 393 Example 16 LiPO₂F₂ 6.3 591 5.6 410 Comparative example 4 none 6.3 503 5.1 315

[2453] positive electrode [5] embodiment 17

The positive active material obtained by fully mixing the positive active material C and the positive active material F at a mass ratio of 1:1 is used as the positive active material to make the positive electrode, which is rolled into a thickness of 78 μm with a press machine, and 32 pieces of the positive electrode and 33 pieces are used. The negative electrode was carried out in the same manner as in Example 1 of the positive electrode [5] except for this. (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 2.1, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.6. The BET specific surface area of the mixed positive electrode active material was 0.8 m ² /g, the average primary particle size was 0.6 μm, the median particle size d ₅₀ was 8.5 μm, and the tap density was 2.2 g/cm ³ . The battery evaluation results are shown in Table 6 of the positive electrode [5].

Positive electrode [5] Example 18

The non-aqueous electrolytic solution was carried out in the same manner as in Example 17 of the positive electrode [5] except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [5].

Positive electrode [5] Example 19

The non-aqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 17. The results of the battery evaluation are shown in Table 6 of the positive electrode [5].

Positive electrode [5] Example 20

The same procedure as in Example 17 of the positive electrode [5] was carried out except that the nonaqueous electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 6 of the positive electrode [5].

Positive electrode [5] Comparative Example 5

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, the same implementation was carried out as in Example 17 of the positive electrode [5]. The results of the battery evaluation are shown in Table 6 of the positive electrode [5].

Positive electrode [5] Table 6

[Table 29]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 17 Hexamethylcyclotrisiloxane 6.1 723 5.0 457 Example 18 Trimethylsilyl methanesulfonate 6.1 732 5.0 469 Example 19 phenyl dimethyl fluorosilane 6.1 719 5.0 455 Example 20 LiPO₂F₂ 6.1 741 5.0 477 Comparative Example 5 none 6.1 630 4.6 363

[2466] positive electrode [5] embodiment 21

Use the positive active material obtained by fully mixing the positive active material D and the positive active material E with a mass ratio of 1:1 as the positive active material to make the positive electrode, and roll it into a thickness of 72 μm with a press machine. Use 33 pieces of the positive electrode and 34 pieces The negative electrode was carried out in the same manner as in Example 1 of the positive electrode [5] except for this. The mixed positive electrode active material had a BET specific surface area of 0.9 m ² /g, an average primary particle size of 0.7 μm, a median particle size d ₅₀ of 6.7 μm, and a tap density of 2.0 g/cm ³ . (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 1.9, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 21.3. The battery was evaluated in the same manner as in Example 1 of the positive electrode [5], except that the voltage range in the capacity measurement was 3.0 to 4.1 V, and the upper limit voltage in the cycle test was 4.1 V. The battery evaluation results are shown in Table 7 of the positive electrode [5].

Positive electrode [5] Example 22

The non-aqueous electrolytic solution was made to contain 0.3 mass % of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 17. The results of the battery evaluation are shown in Table 7 of the positive electrode [5].

Positive electrode [5] Example 23

The non-aqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 17. The results of the battery evaluation are shown in Table 7 of the positive electrode [5].

Positive electrode [5] Example 24

The same procedure as in Example 17 of the positive electrode [5] was carried out except that the nonaqueous electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 7 of the positive electrode [5].

Positive electrode [5] Comparative example 6

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, the same implementation was carried out as in Example 17 of the positive electrode [5]. The results of the battery evaluation are shown in Table 7 of the positive electrode [5].

Positive electrode [5] Table 7

[Table 30]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 21 Hexamethylcyclotrisiloxane 6.3 578 5.6 402 Example 22 Trimethylsilyl methanesulfonate 6.3 584 5.6 406 Example 23 phenyl dimethyl fluorosilane 6.3 576 5.6 397 Example 24 LiPO₂F₂ 6.3 591 5.7 415 Comparative example 6 none 6.3 503 5.2 319

Positive electrode [5] Example 25

Use the positive active material obtained by fully mixing the positive active material E and the positive active material F at a mass ratio of 1:1 as the positive active material to make a positive electrode, and roll it into a thickness of 86 μm with a press machine. Use 31 pieces of the positive electrode and 32 pieces The negative electrode was carried out in the same manner as in Example 1 of the positive electrode [5] except for this. (Thickness of the positive electrode active material layer on the positive electrode side)/(Thickness of the positive electrode current collector) was 2.4, and the ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.0. The mixed positive electrode active material had a BET specific surface area of 1.1 m ² /g, an average primary particle size of 0.6 μm, a median particle size d ₅₀ of 6.2 μm, and a tap density of 2.0 g/cm ³ . The battery evaluation results are shown in Table 8 of the positive electrode [5].

Positive electrode [5] Example 26

The non-aqueous electrolytic solution was carried out in the same manner as in Example 17 of the positive electrode [5] except that 0.3% by mass of trimethylsilyl methanesulfonate was included instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 8 of the positive electrode [5].

Positive electrode [5] Example 27

The non-aqueous electrolytic solution was made to contain 0.3 mass % of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane, and it carried out similarly to positive electrode [5] Example 17. The results of the battery evaluation are shown in Table 8 of the positive electrode [5].

Positive electrode [5] Example 28

The same procedure as in Example 17 of the positive electrode [5] was carried out except that the nonaqueous electrolytic solution contained 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane. The results of the battery evaluation are shown in Table 8 of the positive electrode [5].

Positive electrode [5] Comparative example 7

Except that hexamethylcyclotrisiloxane is not contained in the non-aqueous electrolyte solution, the same implementation was carried out as in Example 17 of the positive electrode [5]. The results of the battery evaluation are shown in Table 8 of the positive electrode [5].

Positive pole [5] Table 8

[Table 31]

specific compound battery capacity initial output power Endurance battery capacity Output power after durability Ah W Ah W Example 25 Hexamethylcyclotrisiloxane 5.9 744 4.8 474 Example 26 Trimethylsilyl methanesulfonate 5.9 755 4.9 484 Example 27 phenyl dimethyl fluorosilane 5.9 739 4.8 469 Example 28 LiPO₂F₂ 5.9 763 4.9 493 Comparative example 7 none 5.9 648 4.4 368

From the results in Table 2 of the positive electrode [5] to Table 8 of the positive electrode [5], it can be seen that in any positive electrode, since the non-aqueous electrolyte contains a specific compound, the output power and capacity retention are improved, and even in the cycle After the test, the battery capacity and output power can also be fully maintained.

Negative electrode[1][Production of negative electrode active material]

(Production of negative electrode active material 1)

In order to prevent the commercially available natural graphite powder, which is a particulate carbonaceous material, from being mixed with coarse particles, the sieve was repeatedly sieved five times using an ASTM 400 mesh sieve. The negative electrode material thus obtained is referred to as a carbonaceous substance (A).

(Production of negative electrode active material 2)

Petroleum heavy oil obtained during pyrolysis of naphtha was subjected to carbonization treatment at 1300° C. in an inert gas, and then the carbonaceous material (B) was obtained by classifying the sintered product. In the classification process, in order to prevent the mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times.

(Production of negative electrode active material 3)

95% by mass of the carbonaceous substance (A) and 5% by mass of the carbonaceous substance (B) were uniformly mixed, and the mixture was made into a two-type crystalline carbonaceous substance mixture (C).

(Production of negative electrode active material 4)

Petroleum heavy oil obtained during the pyrolysis of naphtha is mixed with the carbonaceous substance (A), carbonized at 1300° C. in an inert gas, and then the carbonaceous substance (D) is obtained by classifying the sintered product, The composite carbonaceous substance (D) is a composite carbonaceous substance in which carbonaceous substances having different crystallinity are coated on the surface of the carbonaceous substance (A) particle. During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of low-crystalline carbonaceous material relative to 95 parts by weight of graphite.

(Production of negative electrode active material 5)

In addition to reducing the heavy petroleum oil obtained during the pyrolysis of naphtha in the making of the negative active material 4 and mixing, follow the same method as the making of the negative active material 4 to obtain a composite carbonaceous material (E), which is compared 99 parts by weight of graphite is coated with 1 weight of low-crystalline carbonaceous material.

(Production of negative electrode active material 6)

In addition to increasing the petroleum heavy oil obtained during the pyrolysis of naphtha in the making of negative active material 4 and mixing, follow the same method as making 4 of negative active material to obtain composite carbonaceous material (F), which is compared 90 parts by weight of graphite is coated with 10 parts by weight of low-crystalline carbonaceous material.

(Production of negative electrode active material 7)

In addition to increasing the petroleum heavy oil obtained during the pyrolysis of naphtha in the making of the negative active material 4 and mixing, follow the same method as the making of the negative active material 4 to obtain a composite carbonaceous material (G), which is compared 70 parts by weight of graphite is coated with 30 parts by weight of low-crystalline carbonaceous material.

(Production of negative electrode active material 8)

In addition to implementing the graphitization treatment at 3000° C. in an inert gas in the making 4 of the negative electrode active material, the same method as the making 4 of the negative electrode active material was carried out to obtain a composite carbonaceous material (I), which was compared to 95 The parts by weight of graphite are coated with 5 parts by weight of low-crystalline carbonaceous material.

(Production of negative electrode active material 9)

Mix the phenol-formaldehyde solution in the carbonaceous substance (A), implement carbonization treatment at 1300° C. in an inert gas, and then obtain a composite carbonaceous substance powder by classifying the sintered material, and the composite carbonaceous substance powder is A composite carbonaceous substance powder in which carbonaceous substances with different crystallinity are coated on the surface of graphite particles. During the classification process, in order to prevent the mixing of coarse particles, the ASTM400 mesh sieve was used to sieve repeatedly 5 times to obtain the composite carbonaceous material (J). It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of low-crystalline carbonaceous material relative to 95 parts by weight of graphite.

(Production of negative electrode active material 10)

Coal tar pitch having a quinoline-insoluble component of 0.05% by mass or less was heat-treated in a reaction furnace at 460°C for 10 hours, and the obtained block was crushed using a pulverizer (orient mill manufactured by Seishin Enterprise Co., Ltd.). The carbonaceous material was pulverized and then finely pulverized using a pulverizer (turbine mill manufactured by Matsubo Co., Ltd.) to a median particle size of 17 μm. The particles were placed in a metal container, and heat-treated at 540° C. for 2 hours in a box-shaped electric furnace under a flow of nitrogen gas. Obtained massive material was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho Co., Ltd.), and finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.). The obtained powder was put into a container, and sintered in an electric furnace at 1300° C. for 1 hour in a nitrogen atmosphere. Then, the obtained sintered product is subjected to classification treatment to obtain a carbonaceous material (K). During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times.

(Production of negative electrode active material 11)

Mix the phenol-formaldehyde solution in the carbonaceous substance (K), implement carbonization treatment at 1300° C. in an inert gas, and then obtain a composite carbonaceous substance powder by classifying the sintered material, and the composite carbonaceous substance powder is A composite carbonaceous substance powder in which carbonaceous substances with different crystallinity are coated on the surface of graphite particles. During the classification process, in order to prevent mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain the composite carbonaceous material (L). It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 40 parts by weight of low-crystalline carbonaceous material relative to 60 parts by weight of graphite.

(Production of negative electrode active material 12)

Petroleum heavy oil obtained during the pyrolysis of naphtha is mixed with the carbonaceous substance (K), carbonized at 1300°C in an inert gas, and then the composite carbonaceous substance powder is obtained by classifying the sintered product. The composite carbonaceous substance powder is a composite carbonaceous substance powder in which carbonaceous substances having different crystallinity are coated on the surface of graphite particles. During the classification process, in order to prevent the mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain the composite carbonaceous material (M). It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of low-crystalline carbonaceous material relative to 95 parts by weight of graphite.

(Production of negative electrode active material 13)

Coal tar pitch with a quinoline-insoluble component of 0.05% by mass or less was heat-treated in a reaction furnace at 460°C for 10 hours, and the obtained massive carbonaceous material was pulverized using a pulverizer (orient mill manufactured by Senshin Enterprise Co., Ltd.) , and then finely pulverized using a pulverizer (turbine mill manufactured by Matsubo Co., Ltd.) to a median particle size of 17 μm. The particles were placed in a metal container, and heat-treated at 540° C. for 2 hours in a box-shaped electric furnace under a flow of nitrogen gas. The obtained lumpy material was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), and then finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.), and the obtained powder was put into a container , under a nitrogen atmosphere, sintered in an electric furnace at 1000 ° C for 1 hour. Then, the sintered powder was transferred to a graphite crucible, and graphitized in an inert gas atmosphere at 3000° C. for 5 hours in a direct electric furnace to obtain a carbonaceous material (N). Petroleum-based heavy oil obtained during pyrolysis of naphtha is mixed with the carbonaceous substance (N), carbonized at 900°C in an inert gas, and then the carbonaceous substance (O) is obtained by classifying the sintered product, The composite carbonaceous substance (O) is obtained by coating the surface of graphite particles with carbonaceous substances having different crystallinity. During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of low-crystalline carbonaceous material relative to 95 parts by weight of graphite.

(Production of negative electrode active material 14)

Except using flaky natural graphite to replace the carbonaceous material (A) in the making 4 of the negative electrode active material, carry out according to the making 4 identical method with the negative electrode active material, obtain composite carbonaceous material (P), it is compared with 95 parts by weight of graphite is coated with 5 parts by weight of low-crystalline carbonaceous material.

(Production of negative electrode active material 15)

In addition to reducing the heavy petroleum oil obtained during naphtha pyrolysis in the making of negative electrode active material 14 and mixing, follow the same method as making 4 of negative electrode active material, then, the powder obtained is transferred in the graphite crucible, Graphitization was performed at 3000° C. for 5 hours in an inert gas atmosphere using a direct electric furnace. Then, the carbonaceous substance (Q) is obtained by classifying the sintered product, and the composite carbonaceous substance (Q) is obtained by coating the carbonaceous substance with different crystallinity on the surface of graphite particles. During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 1 weight part of low-crystalline carbonaceous material relative to 99 parts by weight of graphite.

(Production of negative electrode active material 16)

In addition to using natural graphite with a volume average particle diameter of 48 μm to replace the carbonaceous material (A) in the production 4 of the negative active material, the method is the same as that in the production 4 of the negative active material to obtain a composite carbonaceous material (R). , which is coated with 5 wt. parts of low-crystalline carbonaceous material relative to 95 wt. parts of graphite.

(Production of negative electrode active material 17)

Except using natural graphite with 1% ash remaining in a low degree of purification to replace the carbonaceous material (A) in the making of the negative active material 4, proceed according to the same method as the making of the negative active material 4 to obtain a composite carbonaceous material (S) which is coated with 5 weight parts of low-crystalline carbonaceous substances with respect to 95 weight parts of graphite.

The physical properties of the obtained negative electrode active material are shown in Table 1 of the negative electrode [1]. The measurement method of the physical properties is the same as above.

Negative electrode [1] Table 1

[Table 32]

Negative active material Particle size μm Circularity - Specific surface area m²/g Raman R value - Raman half value width cm^-1 d₀₀₂ nm Ash Content Mass% Micropore distribution mL/g Total Micropore Distribution mL/g True Density g/cm³ Circularity - Length-to-diameter ratio - Carbonaceous matter (A) 14.2 0.93 10.5 0.28 26 0.335 0.07 0.125 0.760 2.26 0.93 1.4 Carbonaceous matter (B) 15.0 0.87 12.2 0.90 85 0.345 0.04 0.084 0.490 2.10 0.90 1.4 2 kinds of crystalline carbonaceous mixture (C) 14.7 0.91 10.6 0.33 32 0.336 0.05 0.120 0.758 2.25 0.91 1.7 Composite carbonaceous substance (D) 15.2 0.93 3.0 0.35 37 0.336 0.07 0.101 0.692 2.25 0.93 1.4 Composite carbonaceous substance (E) 14.2 0.93 7.2 0.42 32 0.336 0.07 0.120 0.750 2.26 0.93 1.4 Composite carbonaceous substance (F) 15.7 0.93 3.0 0.42 44 0.336 0.06 0.090 0.683 2.24 0.93 1.4

Negative active material Particle size μm Circularity - Specific surface area m²/g Raman R value - Raman half value width cm^-1 d₀₀₂ nm Ash Content Mass % Micropore distribution mL/g Total Micropore Distribution mL/g True Density g/cm³ Circularity - Length-to-diameter ratio - Composite carbonaceous substance (G) 14.2 0.91 2.5 0.68 65 0.338 0.06 0.086 0.625 2.21 0.91 1.6 Composite carbonaceous substance (I) 15.5 0.93 2.8 0.28 29 0.335 0.03 0.125 0.346 2.26 0.93 1.4 Composite carbonaceous material (J) 15.9 0.92 5.4 0.45 46 0.337 0.08 0.132 0.634 2.24 0.92 1.5 Carbonaceous matter (K) 18.0 0.91 7.5 1.00 86 0.345 0.05 0.086 0.489 2.10 0.87 2.3 Composite carbonaceous substance (L) 19.3 0.92 4.2 1.30 90 0.348 0.05 0.145 0.621 2.09 0.90 2.3 Composite carbonaceous substance (M) 17.8 0.91 5.5 1.04 88 0.345 0.07 0.991 0.593 2.25 0.90 2.2 Composite carbonaceous substance (O) 18.3 0.91 1.7 0.22 twenty two 0.336 0.03 0.058 0.345 2.25 0.92 2.0 Composite carbonaceous substance (P) 19.4 0.80 3.4 0.25 27 0.336 0.08 0.125 0.693 2.25 0.80 3.1 Composite carbonaceous substance (Q) 19.4 0.80 2.5 0.21 20 0.336 0.09 0.121 0.743 2.26 0.80 3.0 Composite carbonaceous substance (R) 53.2 0.90 2.2 0.38 40 0.336 0.08 0.124 0.789 2.25 0.92 1.4 Composite carbonaceous substance (S) 15.7 0.93 3.1 0.34 36 0.336 0.50 0.101 0.693 2.25 0.93 1.4

Negative electrode[1][Battery production]

"Making of Positive Pole 1"

90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride ( PVdF), made into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and then cut into a positive electrode active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the positive electrode active material at this time was 2.35 g/cm ³ .

"Making of Positive Pole 2"

The positive electrode was produced in the same manner as in the positive electrode production 1, except that the mass of the active material coated on each surface was twice that of the positive electrode production 1.

"Making of Positive Pole 3"

90% by mass of LiNi _0.80 Co _0.15 Al _0.05 O ₂ as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride as a binder were mixed in N-methylpyrrolidone solvent (PVdF), made into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, and rolled to a thickness of 65 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm and an uncoated part with a width of 30 mm. shape, as the positive electrode. The density of the positive electrode active material at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode. The negative electrode active material density at this time was 1.35 g/cm ³ .

"The Making of Negative Pole 2"

The preparation of the negative electrode was performed in the same manner as in the preparation 1 of the negative electrode, except that the mass of the active material coated on each surface was twice the amount used in the preparation 1 of the negative electrode.

"The Making of Negative Pole 3"

A negative electrode was produced in the same manner as in negative electrode production 1 except that the density of the active material on one side in negative electrode production 1 was 1.70 g/cm ³ .

"The Making of Negative Pole 4"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 8 parts by weight of sodium carboxymethylcellulose as a binder in 95 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole. The active material density at this time was 1.35 g/cm ³ .

"Production of Electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"Making Electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

"Battery Making 1"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ).

"Battery Making 2"

16 sheets of positive electrodes and 17 sheets of negative electrodes were alternately arranged, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes to perform lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The battery has a rated discharge capacity of about 6 ampere hours (Ah), and a DC resistance component of about 7 milliohms (mΩ) measured by an alternating current method at 10 kHz.

Negative electrode [1] Example 1

Use the negative electrode made by using the negative electrode active material in "Making of Negative Electrode 1" as a mixture of two crystalline carbonaceous substances (C), the positive electrode made in "Making of Positive Electrode 1" and "Making of Electrolyte 1" The electrolytic solution produced in the item is used, and the battery is produced by the method in the item of "Battery Production 1". The battery was measured by the method described in the following item "Evaluation of Battery" and the above-mentioned measurement method.

Negative electrode [1] Example 2

Except that the composite carbonaceous material (D) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 3

Except that the composite carbonaceous material (E) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 4

Except that the composite carbonaceous material (F) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 5

Except that the composite carbonaceous material (G) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative pole [1] embodiment 6

Except that the composite carbonaceous material (J) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 7

Except that the composite carbonaceous material (I) was used as the negative electrode active material in the negative electrode [1] Example 1 of "Making of Negative Electrode 1", a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was carried out.

Negative pole [1] embodiment 8

Except that the composite carbonaceous material (M) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 9

Except that the composite carbonaceous material (R) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 10

Except that the composite carbonaceous material (L) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 11

Except that the composite carbonaceous material (S) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Evaluation of the Battery" was performed.

Negative electrode [1] Example 12

Except that the composite carbonaceous material (O) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Evaluation of the Battery" was performed.

Negative electrode [1] Example 13

Except that the composite carbonaceous material (P) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 14

Except that the composite carbonaceous material (Q) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [1] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed.

Negative electrode [1] Example 15

Use the negative electrode made of the negative electrode active material in "Making of Negative Electrode 2" as the composite carbonaceous material (D), the positive electrode made in "Making of Positive Electrode 2" and the one made in "Making of Electrolyte 1" Electrolyte, make a battery by the method in "Battery Production 2". In addition, evaluation of the battery was carried out in the same manner as in negative electrode [1] Example 1.

Negative electrode [1] Example 16

Use the negative electrode made of the negative electrode active material in "Making of Negative Electrode 3" as a composite carbonaceous material (D), the positive electrode made in "Making of Positive Electrode 1" and the one made in "Making of Electrolyte 1" Electrolyte, the battery is made by the method in item "Battery Production 1". In addition, evaluation of the battery was carried out in the same manner as in negative electrode [1] Example 1.

Negative electrode [1] Example 17

Use the negative electrode made of the negative electrode active material in "Making of Negative Electrode 4" as a composite carbonaceous material (D), the positive electrode made in "Making of Positive Electrode 1" and the one made in "Making of Electrolyte 1" Electrolyte, the battery is made by the method in item "Battery Production 1". In addition, evaluation of the battery was carried out in the same manner as in negative electrode [1] Example 1.

The evaluation results of Negative Electrode [1] Example 1 to Negative Electrode [1] Example 17 are shown in Negative Electrode [1] Table 2.

Negative electrode [1] Examples 18-34

The evaluation of the battery was performed in the same manner except that the electrolytic solution in Examples 1 to 17 of the negative electrode [1] was replaced with the electrolytic solution produced in the item "Preparation of Electrolyte Solution 2". The evaluation results of negative electrode [1] Example 18 to negative electrode [1] Example 34 are shown in Table 3 of negative electrode [1].

Negative electrode [1] Examples 35-51

The evaluation of the battery was performed in the same manner except that the electrolytic solution in Examples 1 to 17 of the negative electrode [1] was replaced with the electrolytic solution produced in the item "Preparation of Electrolyte Solution 3". The evaluation results of negative electrode [1] Example 35 to negative electrode [1] Example 51 are shown in Table 4 of negative electrode [1].

Negative electrode [1] Comparative Example 1

A battery was produced in the same manner as the negative electrode [1] except that the carbonaceous material (A) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of Example 1, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative example 2

Except for the negative electrode [1] and the electrolyte solution of Comparative Example 1, the electrolyte solution prepared in the item "Preparation of Electrolyte Solution 4" was used, and a battery was produced in the same manner, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative example 3

A battery was produced in the same manner as the negative electrode [1] except that the carbonaceous material (B) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of Example 1, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative example 4

Except that the electrolyte solution of the negative electrode [1] Comparative Example 3 was prepared in the item "Preparation of Electrolyte Solution 4", a battery was produced in the same manner as the negative electrode [1] Comparative Example 3, and the battery described in the item "Evaluation of the Battery" was performed. evaluate.

Negative electrode [1] Comparative example 5

Except that the electrolyte solution of the negative electrode [1] Example 1 uses the electrolyte solution produced in the item "Preparation of Electrolyte Solution 4", a battery is produced in the same manner as the negative electrode [1] Example 1, and the battery described in the item "Evaluation of the Battery" is carried out. evaluate.

Negative electrode [1] Comparative Example 6

Except for the negative electrode [1], the electrolyte solution of Example 2 was used, except that the electrolyte solution prepared in the item "Preparation of Electrolyte Solution 4" was used, and a battery was produced in the same manner, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative Example 7

A battery was produced in the same manner as the negative electrode [1] except that the carbonaceous material (K) was used as the negative electrode active material in the item "Preparation of Negative Electrode 1" of Example 1, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative example 8

A battery was produced in the same manner except that the electrolyte solution prepared in the item "Preparation of Electrolyte Solution 4" was used for the electrolyte solution of the negative electrode [1] Comparative Example 7, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative Examples 9-11

The evaluation of the battery was performed in the same manner except that the electrolytic solution of the negative electrode [1] Comparative Examples 1, 3, and 7 was replaced with the electrolytic solution prepared in the item "Preparation of Electrolyte Solution 2".

Negative electrode [1] Comparative examples 12-14

The evaluation of the battery was performed in the same manner except that the electrolytic solution of the negative electrode [1] Comparative Examples 1, 3, and 7 was replaced with the electrolytic solution prepared in the item "Preparation of Electrolyte Solution 3".

The evaluation results of Negative Electrode [1] Comparative Example 1 to Negative Electrode [1] Comparative Example 14 are shown in Negative Electrode [1] Table 5.

Negative electrode [1] Example 52

Use the negative electrode made of the negative electrode active material in "Making of Negative Electrode 1" as the composite carbonaceous material (D), the positive electrode made in "Making of Positive Electrode 1" and the one made in "Making of Electrolyte 1" As for the electrolyte solution, a battery was produced by the method in the item "Production of Battery 1", and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Example 53

A battery was fabricated in the same manner as in Example 52, except that the electrolyte solution prepared in the item "Preparation of Electrolyte Solution 2" was used, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Example 54

A battery was produced in the same manner as in Example 52, except that the electrolyte solution prepared in the item "Preparation of Electrolyte Solution 3" was used, and the battery evaluation described in the item "Evaluation of Battery" was performed.

Negative electrode [1] Comparative Example 15

A battery was fabricated in the same manner as in Example 52, except that the electrolyte solution prepared in the item "Preparation of Electrolyte Solution 4" was used, and the battery evaluation described in the item "Evaluation of Battery" was performed.

The evaluation results of Examples 52 to 54 and Comparative Example 15 are shown in Table 6 of Negative Electrode [1].

Negative electrode [1] "Battery Evaluation"

(capacity measurement)

For a battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 hour Rate (one-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. Then perform the output power measurement shown below.

(Output power measurement)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) was taken as the output power (W).

(cycle test)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.2V by 2C constant current and constant voltage method, discharge to the end-of-discharge voltage of 3.0V with a constant current of 2C, which is regarded as a charge-discharge cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, 3 cycles of charging and discharging were performed in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was used as the capacity after the cycle. The cycle retention rate was obtained from the initial capacity measured before the cycle and the post-cycle capacity measured after the cycle test was completed by the following calculation formula.

Cycle retention (%) = 100 × capacity after cycle / initial capacity

The output power measurement described in the item (Output Power Measurement) was performed on the battery after the cycle test. At this time, the output power retention rate shown by the following formula was calculated using the output power before the cycle test and the output power implemented after the cycle test was completed.

Output power retention (%) = 100 × output power after cycle test / output power before cycle

The impedance Rct and the double-layer capacity Cdl in Table 2 of the negative electrode [1] are one of the parameters that contribute to the output power. The smaller the value of the impedance Rct, or the larger the value of the double-layer capacity Cdl, the more the output power will be improved. tendency. In addition, "impedance Rct" and "double layer capacitance Cdl" were obtained by the method described in the section describing impedance.

Negative pole [1] Table 2

[Table 33]

No. Negative active material Impedance Rct Ω Impedance Cdl ×10^-4F initial capacity mAh DC Resistance mΩ Cycle Retention % Initial output power W Output power after cycle W Output Power Retention % Example 1 Two crystalline carbonaceous mixtures (C) twenty two 1.1 6001 5.2 80 574 420 73 Example 2 Composite carbonaceous substance (D) 25 0.9 6010 4.9 84 595 450 76 Example 3 Composite carbonaceous substance (E) 11 1.9 6005 5.2 82 602 432 72 Example 4 Composite carbonaceous substance (F) 28 1.2 6000 5.2 83 581 420 72 Example 5 Composite carbonaceous substance (G) 30 0.8 5890 5.6 81 567 396 70 Example 6 Composite carbonaceous material (J) twenty four 1.2 5987 5.1 82 588 414 70 Example 7 Composite carbonaceous substance (I) 35 1.0 6010 5.3 84 574 414 72 Example 8 Composite carbonaceous substance (M) 75 0.7 5609 5.4 79 560 390 70 Example 9 Composite carbonaceous substance (R) 25 0.9 6007 4.9 78 574 408 71 Example 10 Composite carbonaceous substance (L) 60 0.7 5045 5.5 76 532 342 64 Example 11 Composite carbonaceous substance (S) twenty two 1.0 6002 5.8 81 574 402 70 Example 12 Composite carbonaceous substance (O) 150 0.1 5928 5.4 80 539 366 68 Example 13 Composite carbonaceous substance (P) 42 0.7 5920 5.4 82 539 366 68 Example 14 Composite carbonaceous substance (Q) 45 0.9 5902 5.2 79 553 372 67 Example 15 Composite carbonaceous substance (D) 14 0.8 5989 5.1 76 560 366 65 Example 16 Composite carbonaceous substance (D) 15 1.0 5989 4.8 79 588 396 67 Example 17 Composite carbonaceous substance (D) 50 0.4 5982 5.5 78 602 390 65

Negative electrode [1] In Table 2, the electrolytic solution contained 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) prepared in <<Preparation of Electrolyte Solution 1>>.

Negative pole [1] Table 3

[Table 34]

No. Negative active material Impedance Rct Ω Impedance Cdl ×10^-4F initial capacity mAh DC Resistance mΩ Cycle Retention % Initial output power W Output power after cycle W Output Power Retention % Example 18 Two crystalline carbonaceous mixtures (C) twenty three 1.1 5821 5.3 78 557 400 72 Example 19 Composite carbonaceous substance (D) 27 0.9 5830 5.6 82 577 426 74 Example 20 Composite carbonaceous substance (E) 12 1.8 5825 4.9 80 584 415 71 Example 21 Composite carbonaceous substance (F) 30 1.2 5820 4.6 81 564 391 69 Example 22 Composite carbonaceous substance (G) 32 0.7 5713 5.5 79 550 375 68 Example 23 Composite carbonaceous material (J) 25 1.2 5807 5.2 80 570 396 69 Example 24 Composite carbonaceous substance (I) 37 0.9 5830 5.3 82 557 394 71 Example 25 Composite carbonaceous substance (M) 80 0.7 5441 5.1 77 543 368 68 Example 26 Composite carbonaceous substance (R) 27 0.9 5827 5.3 76 557 389 70 Example 27 Composite carbonaceous substance (L) 64 0.7 4894 4.8 74 516 318 62 Example 28 Composite carbonaceous substance (S) twenty three 0.9 5822 4.7 79 557 382 69 Example 29 Composite carbonaceous substance (O) 159 0.1 5750 4.8 78 523 348 67 Example 30 Composite carbonaceous substance (P) 45 0.6 5742 5.2 80 523 336 64 Example 31 Composite carbonaceous substance (Q) 48 0.8 5725 5.2 77 536 345 64 Example 32 Composite carbonaceous substance (D) 15 0.8 5809 5.0 74 543 335 62 Example 33 Composite carbonaceous substance (D) 16 1.0 5809 4.7 77 570 372 65 Example 34 Composite carbonaceous substance (D) 53 0.4 5803 4.9 76 584 365 63

Negative electrode [1] In Table 3, the electrolytic solution contained 0.3% by mass of trimethylsilyl methanesulfonate prepared in <<Preparation of Electrolyte Solution 2>>.

Negative pole [1] Table 4

[Table 35]

No. Negative active material Impedance Rct Ω Impedance Cdl ×10^-4F initial capacity mAh DC Resistance mΩ Cycle Retention % Initial output power W Output power after cycle W Output Power Retention % Example 35 Two crystalline carbonaceous mixtures (C) 26 1.3 6061 4.8 78 557 391 70 Example 36 Composite carbonaceous substance (D) 30 1.0 6070 5.2 81 577 419 73 Example 37 Composite carbonaceous substance (E) 13 2.0 6065 5.1 80 584 402 69 Example 38 Composite carbonaceous substance (F) 34 1.3 6060 5.0 81 564 391 69 Example 39 Composite carbonaceous substance (G) 36 0.8 5949 5.2 79 550 369 67 Example 40 Composite carbonaceous material (J) 29 1.3 6047 4.9 80 570 386 68 Example 41 Composite carbonaceous substance (I) 42 1.1 6070 4.7 81 557 386 69 Example 42 Composite carbonaceous substance (M) 90 0.8 5665 5.1 77 543 363 67 Example 43 Composite carbonaceous substance (R) 30 1.0 6067 5.0 76 557 377 68 Example 44 Composite carbonaceous substance (L) 72 0.8 5095 4.8 74 516 314 61 Example 45 Composite carbonaceous substance (S) 26 1.1 6062 5.3 79 557 358 64 Example 46 Composite carbonaceous substance (O) 180 0.1 5987 5.1 78 523 341 65 Example 47 Composite carbonaceous substance (P) 50 0.7 5979 4.9 80 523 341 65 Example 48 Composite carbonaceous substance (Q) 54 1.0 5961 5.1 77 536 354 66 Example 49 Composite carbonaceous substance (D) 17 0.9 6049 5.0 74 543 345 63 Example 50 Composite carbonaceous substance (D) 18 1.1 6049 4.6 77 570 352 62 Example 51 Composite carbonaceous substance (D) 60 0.4 6042 5.4 76 584 350 60

Negative electrode [1] In Table 4, the electrolytic solution contained 0.3% by mass of hexamethylcyclotrisiloxane prepared in <<Preparation of Electrolyte Solution 3>>.

Negative pole [1] Table 5

[Table 36]

No. Negative active material specific compound Impedance Rct Ω Impedance Cdl ×10^-4F initial capacity mAh DC Resistance mΩ Cycle Retention % Initial output power W Output power after cycle W Output power retention rate % Comparative example 1 Carbonaceous matter (A) Lithium difluorophosphate 9 1.4 6006 4.7 75 525 342 65 Comparative example 2 Carbonaceous matter (A) - 9 1.4 6003 4.9 72 504 312 62 Comparative example 3 Carbonaceous matter (B) Lithium difluorophosphate 50 0.5 5102 5.1 75 483 318 66 Comparative example 4 Carbonaceous matter (B) - 50 0.5 5034 5.2 73 455 288 63 Comparative Example 5 2 kinds of crystalline carbonaceous mixture (C) - twenty two 1.1 5989 5.4 75 511 330 65 Comparative example 6 Carbonaceous matter (D) - 9 1.4 5996 4.9 78 518 330 64 Comparative example 7 Carbonaceous matter (K) Lithium difluorophosphate 60 0.5 5042 4.9 75 511 282 55 Comparative example 8 Carbonaceous matter (K) - 60 0.5 5111 5.0 73 497 276 56 Comparative example 9 Carbonaceous matter (A) Trimethylsilyl methanesulfonate 10 1.4 5886 4.6 74 515 331 64 Comparative Example 10 Carbonaceous matter (B) Trimethylsilyl methanesulfonate 53 0.5 4898 4.9 74 473 312 66 Comparative example 11 Carbonaceous matter (K) Trimethylsilyl methanesulfonate 64 0.5 4992 4.8 74 501 266 53 Comparative example 12 Carbonaceous matter (A) Hexamethylcyclotrisiloxane 11 1.5 6186 4.9 72 504 315 63 Comparative Example 13 Carbonaceous matter (B) Hexamethylcyclotrisiloxane 59 0.5 5204 5.3 72 464 298 64 Comparative Example 14 Carbonaceous matter (K) Hexamethylcyclotrisiloxane 74 0.6 5395 5.4 72 491 244 50

Negative electrode [1] Table 6

Table [36] No. Electrolyte Additives for Electrolyte initial capacity DC Resistance cycle retention Initial output power Output power after cycle output power retention mAh mΩ % W W % Example 52 Preparation of Electrolyte 1 Lithium difluorophosphate 5780 4.6 88 634 465 73 Example 53 Electrolyte preparation 2 Trimethylsilyl methanesulfonate 5830 5.5 88 632 457 72 Example 54 Preparation of Electrolyte 3 Hexamethylcyclotrisiloxane 5760 4.9 88 619 452 73 Comparative Example 15 Preparation of electrolyte 4 none 5810 4.7 82 543 364 67

From the results of Tables 2 to 6 of the negative electrode [1], it can be seen that by combining the situation of containing difluorophosphate lithium salt, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane and making the negative electrode active material contain 2 The combination of more than one carbonaceous material with different crystallinity can dramatically improve the power retention rate after cycling.

Negative electrode [2] [Production of negative electrode active material]

(Production of negative electrode active material 1)

Coal tar pitch with a quinoline-insoluble component of 0.05% by mass or less was heat-treated in a reaction furnace for 10 hours at 460° C., and the resulting lumpy carbonaceous material was crushed using a pulverizer (orient mill manufactured by Seishin Enterprise Co., Ltd.). After crushing, finely pulverize using a pulverizer (turbine mill manufactured by Matsubo Co., Ltd.), and refine it to a median particle size of 18 μm. The particles were placed in a metal container, and heat-treated at 540° C. for 2 hours in a box-shaped electric furnace under nitrogen gas flow. The resulting lumpy material was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), and finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.), and the obtained powder was filled into a container , under a nitrogen atmosphere, fired in an electric furnace at 1000°C for 1 hour. Then, the obtained sintered product is subjected to classification treatment to obtain an amorphous carbonaceous material (A). During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times.

(Production of negative electrode active material 2)

In a reaction furnace at 460° C., coal tar pitch with a quinoline-insoluble component of 0.05% by mass or less was heat-treated for 10 hours. Heat treatment was performed at 1000°C for 2 hours. Then, the obtained sintered product is subjected to classification treatment to obtain an amorphous carbonaceous material (A). The obtained amorphous lump was pulverized using a coarse pulverizer (roll crusher manufactured by Yoshida Seisakusho), and finely pulverized using a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.) to obtain an amorphous powder. In order to prevent coarse particles from being mixed into the obtained powder, the sieve was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as an amorphous carbonaceous material (B).

(Production of negative electrode active material 3)

The amorphous bulk material obtained in (making of negative electrode active material 2) is transferred in the graphite crucible again, use direct electric furnace, under inert gas atmosphere, heat treatment at 2200 ℃ for 5 hours, with coarse pulverizer (Yoshida Roller crusher manufactured by Seisakusho Co., Ltd.) pulverizes the obtained lumpy material, and then finely pulverizes it with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.). In order to prevent coarse particles from being mixed into the obtained powder, an ASTM400 mesh sieve is used. Sieve repeatedly 5 times. The negative electrode active material thus obtained is referred to as an amorphous carbonaceous material (C).

(Production of negative electrode active material 4)

Transfer the amorphous bulk material obtained in (production of negative electrode active material 2) to a graphite crucible, use a direct electric furnace, and carry out graphitization at 3000°C for 5 hours under an inert gas atmosphere, and use a coarse pulverizer (Roller crusher manufactured by Yoshida Seisakusho Co., Ltd.) crushed the obtained lumpy material, and then finely pulverized it using a pulverizer (turbine mill manufactured by Matsubo Co., Ltd.). In order to prevent coarse particles from being mixed into the obtained powder, ASTM400 was used The objective sieve was repeatedly sieved 5 times. The negative electrode active material thus obtained is referred to as an amorphous carbonaceous material (D).

(Production of negative electrode active material 5)

In order to prevent the commercially available flaky natural graphite powder from being mixed with coarse particles, it was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as an amorphous carbonaceous material (E).

The physical properties, shape, etc. of the negative electrode active materials obtained in Preparations 1 to 5 of the negative electrode active materials were measured by the above-mentioned method. The results are shown in Table 1 of the negative electrode [2].

Negative electrode [2] Table 1

[Table 37]

Production No. Negative active material d002 nm Lc nm Raman R value - Raman half value width cm^-1 True Density g/cm³ BET specific surface area m²/g Vibration Density g/cm³ Ash % Volume average particle size μm 1 Amorphous carbonaceous (A) 0.344 2.4 0.98 83.0 1.93 1.5 1.1 0.05 12.4 2 Amorphous carbonaceous (B) 0.343 2.2 1.06 86.0 1.97 5.4 0.9 0.05 14.6 3 Amorphous carbonaceous (C) 0.340 32.9 0.21 27.8 2.21 7.1 0.3 0.03 14.7 4 Graphite carbonaceous (D) 0.336 100＜ 0.11 25.9 2.26 8.6 0.4 0.02 15.3 5 Graphite carbonaceous (E) 0.335 100＜ 0.16 25.8 2.26 10.4 0.7 0.04 11.6

Negative electrode [2] [Battery production]

"Making of Positive Pole 1"

90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride ( PVdF), made into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the positive electrode active material at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole. The negative electrode active material density at this time was 1.35 g/cm ³ .

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

"Battery Making 1"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ). The ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.6.

Negative electrode [2] Embodiment 1

Using the negative electrode active material in "Making of Negative Electrode 1" as the negative electrode made of amorphous carbonaceous (A), the positive electrode made in "Making of Positive Electrode 1" and the electrolysis made in "Making of Electrolyte 1" liquid, and make a battery by the method in "Battery Production 1". The battery was subjected to battery evaluation by the method described in the item "Evaluation of Battery" below. The results are shown in Table 2 of the negative electrode [2].

Negative pole [2] embodiment 2

Except for using amorphous carbonaceous (B) as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [2] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed. The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Example 3

Except for using amorphous carbonaceous (C) as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [2] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed. The results are shown in Table 2 of the negative electrode [2].

Negative pole [2] Embodiment 4～6

Except that the non-aqueous electrolyte solution of Examples 1 to 2 of the negative electrode [2] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 2", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Examples 7-9

Except that the non-aqueous electrolyte solution of Examples 1 to 3 of the negative electrode [2] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 3", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Comparative examples 1 to 3

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolyte solutions of Comparative Examples 1 to 3 of the negative electrode [2] were replaced with the non-aqueous electrolyte solutions produced in the item "Preparation of Non-aqueous Electrolyte Solutions 4". The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Comparative example 4

Except for negative electrode [2] Example 1 "Preparation of Negative Electrode 1" negative electrode active material using graphite carbonaceous (D), similarly produced a battery, and carried out the battery evaluation described in "Battery Evaluation". The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Comparative Example 5

Except for using the graphite carbonaceous material (E) as the negative electrode active material in the item "Preparation of Negative Electrode 1" of the negative electrode [2] Example 1, a battery was produced in the same manner, and the battery evaluation described in the item "Battery Evaluation" was performed. The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Comparative examples 6-7

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolyte solutions of Comparative Examples 4 to 5 of the negative electrode [2] were replaced with the non-aqueous electrolyte solutions produced in the item "Preparation of Non-aqueous Electrolyte Solutions 2". The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Comparative Examples 8-9

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolyte solutions of Comparative Examples 4 to 5 of the negative electrode [2] were replaced with the non-aqueous electrolyte solutions produced in the item "Preparation of Non-aqueous Electrolyte Solutions 3". The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] Comparative examples 10-11

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolyte solutions of Comparative Examples 4 to 5 of the negative electrode [2] were replaced with the non-aqueous electrolyte solutions produced in the item "Preparation of Non-aqueous Electrolyte Solutions 4". The results are shown in Table 2 of the negative electrode [2].

Negative electrode [2] "Battery Evaluation"

(capacity measurement)

For a new battery that has not undergone charge-discharge cycles, 5 cycles of initial charge-discharge (voltage range 4.1V-3.0V) were performed at 25°C and a voltage range of 4.1V-3.0V. At this time, the 0.2 C discharge capacity of the fifth cycle (the current value of the 1-hour discharge rated capacity is taken as 1C, and the rated capacity depends on the discharge capacity of the 1-hour-rate (one-hour-rate), the same below) C discharge capacity is taken as the initial stage capacity.

(Short time high current density charge and discharge characteristics test)

The battery after the capacity measurement was charged for 150 minutes at a constant current of 0.2 C at a room temperature environment of 25° C. Taking the voltage at this time as the center, a high load current of 10C was applied to both the charging direction and the discharging direction for about 10 seconds, and the test was continuously repeated for a cycle of 35 seconds including the intermittent time. The battery was taken out at the time of the 100,000th cycle, discharged to 3V with a current of 0.2C, and one cycle was performed by the same method as in the item (capacity measurement), and the capacity after cycle was taken. Also, the short-time high current density charge and discharge characteristics were calculated by the following equation.

[Short-time high current density charge-discharge characteristics] = 100×[Capacity after cycle]/[Initial capacity]

Negative electrode [2] Table 2

[Table 38]

No. Negative active material specific compound Initial Capacity mAh Short time high current density charge and discharge characteristics % Example 1 Amorphous carbonaceous (A) Lithium difluorophosphate 6020 93 Example 2 Amorphous carbonaceous (B) Lithium difluorophosphate 6035 94 Example 3 Amorphous carbonaceous (C) Lithium difluorophosphate 6001 90 Example 4 Amorphous carbonaceous (A) Trimethylsilyl methanesulfonate 6021 91 Example 5 Amorphous carbonaceous (B) Trimethylsilyl methanesulfonate 6023 92 Example 6 Amorphous carbonaceous (C) Trimethylsilyl methanesulfonate 6015 88 Example 7 Amorphous carbonaceous (A) Hexamethylcyclotrisiloxane 6004 91 Example 8 Amorphous carbonaceous (B) Hexamethylcyclotrisiloxane 5997 90 Example 9 Amorphous carbonaceous (C) Hexamethylcyclotrisiloxane 5987 92 Comparative example 1 Amorphous carbonaceous (A) --- 6012 88 Comparative example 2 Amorphous carbonaceous (B) --- 6029 89 Comparative example 3 Amorphous carbonaceous (C) --- 6009 85 Comparative example 4 Graphite carbonaceous (D) Lithium difluorophosphate 5998 87 Comparative Example 5 Graphitic carbonaceous (E) Lithium difluorophosphate 6012 78 Comparative example 6 Graphite carbonaceous (D) Trimethylsilyl methanesulfonate 6001 86 Comparative example 7 Graphitic carbonaceous (E) Trimethylsilyl methanesulfonate 6003 79 Comparative example 8 Graphite carbonaceous (D) Hexamethylcyclotrisiloxane 6032 87 Comparative example 9 Graphitic carbonaceous (E) Hexamethylcyclotrisiloxane 6002 78 Comparative Example 10 Graphite carbonaceous (D) --- 6004 85 Comparative example 11 Graphitic carbonaceous (E) --- 5990 77

From the results of negative pole [2] table 2, it can be seen that by containing lithium difluorophosphate, trimethylsilyl methanesulfonate, hexamethylcyclotrisiloxane, and containing (002 ) surface spacing (d002) of 0.337 or more, Lc of 80nm or less, and Raman R value of 0.2 or more amorphous carbon as the negative electrode active material can dramatically improve short-term high current density charge and discharge characteristics .

Negative electrode [3] [Production of negative electrode active material]

(Production of negative electrode active material 1)

In order to prevent mixing of coarse particles, commercially available Li _1.33 Ti _1.66 O ₄ with a volume average particle diameter of 23 μm was repeatedly sieved five times using an ASTM 400 mesh sieve to obtain a lithium-titanium composite oxide (A).

(Production of negative electrode active material 2)

In order to prevent mixing of coarse particles, commercially available Li _1.33 Ti _1.66 O ₄ with a volume average particle diameter of 1.0 μm was repeatedly sieved five times using an ASTM 400 mesh sieve to obtain a lithium-titanium composite oxide (B).

(Production of negative electrode active material 3)

In order to prevent mixing of coarse particles, commercially available Li _1.33 Ti _1.66 O ₄ with a volume average particle diameter of 0.1 μm was repeatedly sieved five times using an ASTM400 mesh sieve to obtain a lithium-titanium composite oxide (C).

(Production of negative electrode active material 4)

In order to prevent the commercially available flaky natural graphite powder from being mixed with coarse particles, it was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as graphitic carbon (D).

The composition, structure, shape, and physical properties of the negative electrode active material are summarized in Table 1 of the negative electrode [3].

Negative pole [3] Table 1

[Table 39]

Production No. Negative active material Composition structure Volume average particle size μm BET specific surface area m²/g Vibration Density g/cm³ Circularity aspect ratio 1 Lithium titanium composite oxide (A) Li_1.33Ti_1.66O₄ Spinel structure twenty three 3.2 1.5 0.99 1.0 2 Lithium titanium composite oxide (B) Li_1.33Ti_1.66O₄ Spinel structure 1.0 10.5 1.2 0.99 1.0 3 Lithium titanium composite oxide (C) Li_1.33Ti_1.66O₄ Spinel structure 0.1 38.9 0.5 0.97 1.0 4 Graphite carbonaceous (D) C Graphite flakes 11.6 10.4 0.7 0.90 1.8

Negative electrode [3] [Battery production]

"Making of Positive Pole 1"

90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride ( PVdF), made into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the active material of the positive electrode at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

A slurry was prepared by mixing 90% by mass of a negative electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder in an N-methylpyrrolidone solvent. The obtained slurry is coated on one side of a rolled copper foil with a thickness of 10 μm, dried, and rolled to a thickness of 90 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

(Battery production 1)

Punch the negative electrode and the positive electrode into 12.5mmφ, vacuum dry at 110°C, transfer to the glove box, and place the positive and negative electrodes opposite each other with a polyethylene separator punched into 14mmφ under the argon atmosphere, and add A 2032-type coin battery (lithium secondary battery) was produced using the nonaqueous electrolyte solution described in the section on preparation of the nonaqueous electrolyte solution.

Negative pole [3] embodiment 1

The negative electrode produced by using lithium-titanium composite oxide (A) as the negative electrode active material in the item "Production of Negative Electrode 1", the positive electrode produced in the item "Production of Positive Electrode 1", and the item produced in "Production of Non-aqueous Electrolyte 1" Electrolyte, make a battery by the method in "Battery Production 1". The batteries were subjected to the battery evaluations described in the item "Evaluation of Batteries" below. The results are shown in Table 2 of the negative electrode [3].

Negative pole [3] embodiment 2

Except that the negative electrode active material of negative electrode [3] Example 1 of "Making of Negative Electrode 1" uses lithium titanium composite oxide (B), a battery is produced in the same manner as in negative electrode [3] Example 1, and "Battery Evaluation" "Battery evaluation recorded in item. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Example 3

Except that the negative electrode active material of negative electrode [3] Example 1 of "Making of Negative Electrode 1" uses lithium-titanium composite oxide (C), a battery is produced in the same manner as negative electrode [3] Example 1, and "Battery Evaluation" "Battery evaluation recorded in item. The results are shown in Table 2 of the negative electrode [3].

Negative pole [3] Embodiment 4～6

Except that the non-aqueous electrolyte solution of Examples 1 to 3 of the negative electrode [3] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 2", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Examples 7-9

Except that the non-aqueous electrolyte solution of Examples 1 to 3 of the negative electrode [3] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 3", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Comparative examples 1 to 3

Except that the non-aqueous electrolyte solution of Examples 1 to 3 of the negative electrode [3] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 4", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Comparative example 4

Except that the negative electrode active material of negative electrode [3] Example 1 of "Making of Negative Electrode 1" uses graphitic carbonaceous (D), a battery is produced in the same manner as negative electrode [3] Example 1, and "Battery Evaluation" is carried out Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Comparative example 5

Except that the non-aqueous electrolyte solution of the negative electrode [3] Comparative Example 4 was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 2", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Comparative example 6

Except that the non-aqueous electrolyte solution of the negative electrode [3] Comparative Example 4 was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 3", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Comparative example 7

Except that the non-aqueous electrolyte solution in Comparative Example 4 of the negative electrode [3] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 4", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] "Battery Evaluation"

(measurement of capacity)

For a new battery that has not been charged and discharged, the lithium-titanium composite oxide is 175mAh/g, and the graphite carbon is 350mAh/g, and the battery capacity is calculated from the amount of active material present on the copper foil. And, based on the battery capacity, at 25°C, in the voltage range of 2.7V to 1.9V, at 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on the rate of 1 hour (one- hour-rate) of the discharge capacity, the same below) for the initial charge and discharge of lithium-titanium composite oxide for 5 cycles. Similarly, the graphitic carbon was initially charged and discharged at 25° C. and in a voltage range of 4.1 V to 3.0 V. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity.

(measurement of output resistance)

In an environment of 25°C, charge with a constant current of 0.2C for 150 minutes, and discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds in an environment of -30°C, and measure the 10th second voltage. The slope of the current-voltage line is taken as the output resistance (Ω), and the results are shown in Table 2 of the negative electrode [3].

Negative electrode [3] Table 2

[Table 40]

No. Negative active material specific compound Output resistance Ω Output resistance reduction rate (%) Example 1 Amorphous carbonaceous (A) Lithium difluorophosphate 75 34 Example 2 Amorphous carbonaceous (B) Lithium difluorophosphate 69 31 Example 3 Amorphous carbonaceous (C) Lithium difluorophosphate 65 28 Example 4 Amorphous carbonaceous (A) Trimethylsilyl methanesulfonate 68 40 Example 5 Amorphous carbonaceous (B) Trimethylsilyl methanesulfonate 71 29 Example 6 Amorphous carbonaceous (C) Trimethylsilyl methanesulfonate 64 29 Example 7 Amorphous carbonaceous (A) Hexamethylcyclotrisiloxane 71 38 Example 8 Amorphous carbonaceous (B) Hexamethylcyclotrisiloxane 66 34 Example 9 Amorphous carbonaceous (C) Hexamethylcyclotrisiloxane 63 30 Comparative example 1 Amorphous carbonaceous (A) --- 114 - Comparative example 2 Amorphous carbonaceous (B) --- 100 - Comparative example 3 Amorphous carbonaceous (C) --- 90 - Comparative example 4 Graphite carbonaceous (D) Lithium difluorophosphate 130 17 Comparative Example 5 Graphite carbonaceous (D) Trimethylsilyl methanesulfonate 137 13 Comparative example 6 Graphite carbonaceous (D) Hexamethylcyclotrisiloxane 135 14 Comparative example 7 Graphite carbonaceous (D) --- 157 -

In Table 2 of the negative electrode [3], the "output resistance reduction rate" is the reduction rate (%) of the output resistance compared with the output resistance of the corresponding battery not containing the specific compound.

From the results in Table 2 of the negative electrode [3], it can be seen that by using lithium difluorophosphate, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane, and containing Titanium metal oxide negative electrode active material can dramatically reduce output resistance.

Negative electrode [4] [Production of negative electrode active material]

(Production of negative electrode active material 1)

Using a spheroidizing treatment device (mixing system manufactured by Nara Machinery Manufacturing Co., Ltd.), the highly purified scaly natural graphite (ash content 0.05% by weight) with a median diameter of about 150 μm was spheroidized at a rotation speed of 6500 rpm for 5 minutes. , 45% by weight of fine powder was removed using a wind-type classifier (OMC-100 manufactured by Seishin Enterprise Co., Ltd.) to obtain spheroidized natural graphite (C).

(Production of negative electrode active material 2)

The powder of the above classified spheroidized natural graphite (C) was charged into a graphite crucible, and heat-treated at 3000° C. for 5 hours in an inert atmosphere using a direct electric furnace to obtain a carbonaceous material (D).

(Production of negative electrode active material 3)

A carbonaceous material (E) was obtained in the same manner except that the heat treatment temperature in (Preparation 2 of the negative electrode active material) was set to 2000°C.

(Production of negative electrode active material 4)

A carbonaceous material (F) was obtained in the same manner except that the heat treatment temperature in (Preparation 2 of negative electrode active material) was set to 1600°C.

(Production of negative electrode active material 5)

A carbonaceous material (G) was obtained in the same manner except that the heat treatment temperature in (Preparation 2 of negative electrode active material) was set to 1200°C.

(Production of negative electrode active material 5)

Scale-like natural graphite (ash content 0.1% by weight) that has been highly purified with a median particle size of 17 μm, a tap density of 0.5 g/cm ³ , and a BET specific surface area of 6 m ² /g is directly mixed with (production of negative electrode active material 2) In the same manner, heat treatment is performed without performing spheroidization treatment to obtain heat-treated natural graphite (H).

(Production of negative electrode active material 6)

The highly purified natural graphite (ash content 0.5% by weight) with a median particle size of 20 μm, a tap density of 0.75 g/cm ³ , and a BET specific surface area of 3 m ² /g was directly carried out in the same manner as in (production of negative electrode active material 2) The heat treatment is performed without the spheroidization treatment to obtain the carbonaceous substance (I).

According to the above-mentioned method, the spheroidized natural graphite (C), carbonaceous substance (D), carbonaceous substance (E), carbonaceous substance (F), carbonaceous substance (G) and heat-treated natural graphite (H) were measured. , The shape and physical properties of the carbonaceous substance (I). The results are shown in Table 1 of the negative electrode [4].

Negative pole [4] Table 1

Negative electrode [4] [Battery production]

"Making of Positive Pole 1"

90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride ( PVdF), made into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the active material of the positive electrode at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole. The density of the active material of the negative electrode at this time was 1.35 g/cm ³ .

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

(Battery production 1)

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ). The ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.6.

Negative pole [4] embodiment 1

Use the negative electrode made of carbonaceous material (D) as the negative electrode active material in the item "Making of Negative Electrode 1", the positive electrode made in the item of "Making of Positive Electrode 1", and the one made in the item of "Making of Nonaqueous Electrolyte 1" Non-aqueous electrolyte, the battery is made by the method in "Battery Production 1". The battery was measured by the method described in the following item "Evaluation of Battery" and the above-mentioned measurement method. The results are shown in Table 2 of the negative electrode [4].

Negative pole [4] embodiment 2

Except that the carbonaceous material (E) is used as the negative electrode active material in the negative electrode [4] Example 1 of "Making of Negative Electrode 1", a battery is produced in the same manner as in negative electrode [4] Example 1, and the item "Battery Evaluation" is carried out. Documented battery evaluation. The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Example 3

Except that the carbonaceous material (F) is used as the negative electrode active material in the negative electrode [4] Example 1 of "Making of the Negative Electrode 1", a battery is produced in the same manner as in the negative electrode [4] Example 1, and the item "Evaluation of the Battery" is carried out. Documented battery evaluation. The results are shown in Table 2 of the negative electrode [4].

Negative pole [4] embodiment 4

Except that the carbonaceous material (G) is used as the negative electrode active material in the negative electrode [4] Example 1 of "Making of the Negative Electrode 1", a battery is produced in the same manner as in the negative electrode [4] Example 1, and the item "Evaluation of the Battery" is carried out. Documented battery evaluation. The results are shown in Table 2 of the negative electrode [4].

Negative pole [4] embodiment 5

Except that negative electrode [4] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses carbonaceous material (I), make battery similarly with negative electrode [4] embodiment 1, and carry out " evaluation of battery " item Documented battery evaluation. The results are shown in Table 2 of the negative electrode [4].

Negative pole [4] Embodiment 6～10

Except that the non-aqueous electrolytes in Examples 1 to 5 of the negative electrode [4] were replaced with the non-aqueous electrolytes prepared in the item "Preparation of Non-aqueous Electrolyte 2", batteries were produced in the same way and evaluated. The results are shown in Table 2 (negative electrode [4] Table 2).

Negative electrode [4] Examples 11-15

Except that the non-aqueous electrolytic solutions in Examples 1 to 5 of the negative electrode [4] were replaced with the non-aqueous electrolytic solutions prepared in the item "Preparation of Non-aqueous Electrolyte 3", batteries were produced in the same way and evaluated. The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 1

Except that the negative electrode active material of negative electrode [4] Example 1 of "Making of Negative Electrode 1" uses spheroidized natural graphite (C), a battery is produced in the same manner as negative electrode [4] Example 1, and "Battery Evaluation" is carried out Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 2

Except that the non-aqueous electrolytic solution of negative pole [4] comparative example 1 uses the non-aqueous electrolytic solution made in " making 4 of non-aqueous electrolytic solution ", make battery similarly with negative pole [4] comparative example 1, and carry out " battery The battery evaluation described in item "Evaluation". The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 3

Except that the negative electrode active material of negative electrode [4] Example 1 of "Making of Negative Electrode 1" uses heat-treated natural graphite (H), a battery is made in the same manner as negative electrode [4] Example 1, and the item "Battery Evaluation" is carried out Documented battery evaluation. The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 4

Except that the non-aqueous electrolytic solution of negative pole [4] comparative example 3 uses the non-aqueous electrolytic solution made in " making 4 of non-aqueous electrolytic solution ", make battery similarly with negative pole [4] comparative example 3, and carry out " battery The battery evaluation described in item "Evaluation". The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 5

Except that the non-aqueous electrolytic solution of negative pole [4] embodiment 5 uses the non-aqueous electrolytic solution made in " making 4 of non-aqueous electrolytic solution " item, make battery similarly with negative pole [4] embodiment 5, and carry out " battery The battery evaluation described in item "Evaluation". The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative Example 6

Except that the nonaqueous electrolytic solution of negative pole [4] embodiment 1 uses the nonaqueous electrolytic solution made in " making 4 of nonaqueous electrolytic solution " item, make battery similarly with negative pole [4] embodiment 1, and carry out " battery The battery evaluation described in item "Evaluation". The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 7, 8

Except that the non-aqueous electrolyte solution of the negative electrode [4] Comparative Examples 1 and 3 was replaced with the non-aqueous electrolyte solution prepared in the item "Preparation of Non-aqueous Electrolyte Solution 2", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Comparative example 9, 10

Except that the non-aqueous electrolyte solution of the negative electrode [4] Comparative Examples 1 and 3 was replaced with the non-aqueous electrolyte solution prepared in the item "Preparation of Non-aqueous Electrolyte Solution 3", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [4].

Negative electrode [4] Table 2

Negative electrode [4] "Battery Evaluation"

(capacity measurement)

For a battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 hour Rate (one-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity.

(preservation test)

Stored in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. Charge it with a constant current and constant voltage method at 0.2C until the capacity reaches 20% of the initial capacity measured during capacity measurement, and reach the charging upper limit voltage of 4.2V, and then store it in a high temperature environment of 60°C for 1 week. The stored battery was discharged at 0.2C to 3V in an environment of 25°C, and further charged and discharged for 3 cycles under the same conditions as (capacity measurement), and the 0.2C discharge capacity of the third cycle was regarded as low charge Capacity after deep save. The cycle retention rate was obtained from the initial capacity measured before the storage test and the capacity after storage at a low charge depth measured after the storage test was completed according to the following calculation formula.

Recovery rate after storage at low charging depth (%) = 100×capacity after storage at low charging depth/initial capacity

From the above results, it can be seen that by containing lithium difluorophosphate, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane, and making a negative electrode active material with a circularity of 0.85 or more and a surface functional The negative electrode of the carbonaceous material with the O/C value of the radical amount of 0-0.01 can dramatically improve the recovery rate after storage at the low depth of charge after the storage test at the low depth of charge.

Negative electrode [5] [Production of negative electrode material]

[Production of negative electrode material 1]

Coal tar pitch with a quinoline-insoluble content of 0.05% by mass or less was heat-treated in a reaction furnace at 460° C. for 10 hours to obtain a molten block-shaped heat-treated graphite crystal precursor with a softening point of 385° C. The obtained massive heat-treated graphite crystal precursor was pulverized with an intermediate pulverizer (orient mill manufactured by Seishin Enterprise Co., Ltd.), and then finely pulverized using a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.) to obtain a median particle size of 17 μm. The micronized graphite crystal precursor powder (E).

In the above-mentioned miniaturized graphite crystal precursor powder (E), a median particle size of 17 μm and an aspect ratio of 1.4 were mixed in a ratio of 50% by mass relative to the total weight of the miniaturized graphite crystal precursor powder and natural graphite. , natural graphite with a tap density of 1.0 g/cm ³ , a BET specific surface area of 6.5 g/cm ³ , and a circularity of 0.92 to obtain a mixed powder.

The mixed powder of the heat-treated graphite crystal precursor was put into a metal container, and heat treatment A was performed at 540° C. for 2 hours in a box-shaped electric furnace under nitrogen flow. In heat treatment A, the finer graphite crystal precursor powder is melted to form a lump of a heat-treated graphite crystal precursor mixture uniformly composited with natural graphite.

The block of the mixture of the solidified heat-treated graphite crystal precursor was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), and finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.), A powder having a median particle size of 18.5 μm was obtained.

The obtained powder was put into a container, and fired in an electric furnace at 1000° C. for 1 hour in a nitrogen atmosphere. After firing, the obtained powder (precursor mixture (F) before heat treatment B) was still in the form of powder, and almost no melting or fusion was observed.

In addition, the fired powder was transferred to a graphite crucible, and graphitized at 3000°C for 5 hours in an inert atmosphere using a direct electric furnace. In order to prevent the mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain different orientation. Carbon composite (G).

[Production of negative electrode material 2]

The natural graphite used in [Manufacture of Negative Electrode Material 1] and binder pitch as a graphitizable binder with a softening point of 88°C were mixed in a weight ratio of 100:30, and then put into a pre-heated to 128°C The mixture was mixed for 20 minutes in a kneader equipped with a masticator-type stirring blade.

Fill the fully kneaded mixture into the mold of a molding machine preheated to 108°C, let it stand for 5 minutes, squeeze the plunger when the temperature of the mixture is stable, and apply a pressure of 2kfg/cm ² (0.20MPa) for molding . The pressure was maintained for 1 minute, and then the drive was stopped. After the pressure reduction was completed, the composite molded body of natural graphite and graphite crystal precursor powder was taken out.

The obtained molded body was put into a metal refractory box as a heat-resistant container, and graphite coke powder was filled in the void. The temperature was raised from room temperature to 1000° C. in an electric furnace over 48 hours, and kept at 1000° C. for 3 hours for devolatilization and firing. Next, the molded body was placed in a graphite crucible, and graphite coke powder was filled in the gap, and heated at 3000° C. for 4 hours in an inert atmosphere using a direct electric furnace to perform graphitization.

The obtained graphite molded body was coarsely pulverized by a jaw crusher, and then finely pulverized by a mill with a pulverizing blade whose rotational speed was set to 4000 rpm. In addition, during the classification treatment, in order to prevent mixing of coarse particles, sieving was repeated 5 times using an ASTM 400-mesh sieve to obtain a hetero-oriented carbon composite (H).

[Production of negative electrode material 3]

An anisotropic carbon composite (I) was obtained in the same manner as in [Preparation of Negative Electrode Material 2], except that the heat treatment in [Preparation of Negative Electrode Material 2] was performed at 2200° C. using a direct electric furnace.

[Production of negative electrode material 4]

Except that the natural graphite in [Production of Negative Electrode Material 2] has a median particle size of 10 μm, an aspect ratio of 2.3, a tap density of 0.64 g/cm ³ , a BET specific surface area of 9.5 m ² /g, and a circularity of Except for the coke of 0.83, a hetero-oriented carbon composite (J) was obtained in the same manner as [Preparation of Negative Electrode Material 2].

[Production of negative electrode material 5]

In addition to mixing the coke used in [Production of Negative Electrode Material 4], silicon carbide as a graphitization catalyst, and binder pitch as a graphitizable binder with a softening point of 88°C in a mass ratio of 100:10:30 , in the same manner as in [Preparation of Negative Electrode Material 2], a hetero-oriented carbon composite (K) was obtained.

[Production of negative electrode material 6]

In addition to making the natural graphite in [Production of Negative Electrode Material 2] have a median particle size of 19.8 μm, an aspect ratio of 3.2, a tap density of 0.47 g/cm ³ , a BET specific surface area of 5.9 m ² /g, and a circularity A different orientation carbon composite (L) was obtained in the same manner as in [Preparation of Negative Electrode Material 2] except for flaky natural graphite having a value of 0.81.

[Production of negative electrode material 7]

Except that the natural graphite in [Production of Negative Electrode Material 2] has a median particle size of 35 μm, an aspect ratio of 1.4, a tap density of 1.02 g/cm ³ , a BET specific surface area of 3.9 m ² /g, and a circularity of Except for the natural graphite of 0.90, a different orientation carbon composite (M) was obtained in the same manner as in [Preparation of Negative Electrode Material 2].

[Production of negative electrode material 8]

A hetero-oriented carbon composite (N) was obtained in the same manner as in [Preparation of Negative Electrode Material 2] except that the rotational speed of the pulverizing blade was set at 1500 rpm.

[Production of negative electrode material 9]

Except that the natural graphite in [Preparation of Negative Electrode Material 2] was natural graphite with a median particle size of 6 μm, an aspect ratio of 1.5, and a tap density of 0.15 g/cm ³ , it was the same as in [Preparation of Negative Electrode Material 2] , to obtain hetero-orientation carbon composite (O).

[Production of negative electrode material 10]

The graphite crystal precursor powder (E) obtained in [Preparation of Negative Electrode Material 1] was put into a metal container, and heat treatment A was performed at 540° C. for 2 hours in a box-shaped electric furnace under nitrogen flow. In the heat treatment A, the graphite crystal precursor powder (E) is melted into a lump.

The solidified heat-treated graphite crystallization precursor block was crushed with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), and finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Corporation) to obtain a median Powder with a particle size of 18.5 μm.

The obtained powder was put into a container, and fired in an electric furnace at 1000° C. for 1 hour in a nitrogen atmosphere. After firing, the obtained powder was still in the form of a powder, and melting and fusion were hardly observed.

In addition, the fired powder was transferred to a graphite crucible, and graphitized at 3000°C for 5 hours in an inert atmosphere using a direct electric furnace. In order to prevent the mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain carbonaceous materials. (P).

[Production of negative electrode material 11]

The natural graphite used in [Preparation of Negative Electrode Material 1] was put into a metal container, and heat treatment A was performed at 540° C. for 2 hours in a box-shaped electric furnace under nitrogen flow. After heat treatment A, melting and fusion of natural graphite were hardly observed. The obtained powder was put into a container, and fired in an electric furnace at 1000° C. for 1 hour in a nitrogen atmosphere. After firing, the obtained powder was still in the form of a powder, and melting and fusion were hardly observed.

In addition, the fired powder was transferred to a graphite crucible, and graphitized at 3000°C for 5 hours in an inert atmosphere using a direct electric furnace. In order to prevent the mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain carbonaceous materials. (Q).

[Production of negative electrode material 12]

The carbonaceous substance (P) and the carbonaceous substance (Q) were mixed at 50% by mass each, and after uniform mixing, a carbonaceous substance mixture (R) was obtained.

Negative electrode [5] [Battery production]

"Making of Positive Pole 1"

90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride ( PVdF), made into slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the active material of the positive electrode at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole. The active material density of the negative electrode at this time was 1.35 g/cm ³ .

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

(Battery production 1)

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The battery has a rated discharge capacity of about 6 ampere hours (Ah), and a DC resistance of about 5 milliohms (mΩ) measured by an alternating current method at 10 kHz.

Negative pole [5] embodiment 1

Negative electrode made by using hetero-orientation carbon composite (G) as the negative electrode active material in item "Preparation of Negative Electrode 1", positive electrode produced in item "Preparation of Positive Electrode 1", and item "Preparation of Nonaqueous Electrolyte 1" The non-aqueous electrolyte solution produced in , and the battery was produced by the method in the "Battery Production 1" item. The battery was measured by the method described in the following item "Evaluation of Battery" and the above-mentioned measurement method.

Negative pole [5] embodiment 2

Except that negative electrode [5] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses different orientation carbon compound (H), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative electrode [5] Example 3

Except that negative electrode [5] embodiment 1 " making 1 of negative electrode " item negative electrode active material uses different orientation carbon compound (I), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative pole [5] embodiment 4

Except that negative electrode [5] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses different orientation carbon compound (J), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative pole [5] embodiment 5

Except that negative electrode [5] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses different orientation carbon compound (K), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative electrode [5] Embodiment 6

Except negative electrode [5] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses different orientation carbon compound (L), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative electrode [5] Embodiment 7

Except that the negative electrode active material of the negative electrode [5] embodiment 1 of "making 1 of the negative electrode" item uses a different orientation carbon composite (M), the battery is made in the same way as the negative electrode [5] embodiment 1, and the "Battery Preparation" Evaluation" item recorded in the battery evaluation.

Negative electrode [5] embodiment 8

Except negative electrode [5] embodiment 1 " making 1 of negative electrode " item negative electrode active material uses different orientation carbon compound (N), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative pole [5] embodiment 9

Except that negative electrode [5] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses different orientation carbon compound (O), make battery similarly with negative electrode [5] embodiment 1, and carry out " battery Evaluation" item recorded in the battery evaluation.

Negative electrode [5] Examples 10-18

Except that the non-aqueous electrolyte solution in Examples 1-9 of the negative electrode [5] was replaced with the non-aqueous electrolyte solution prepared in the item "Preparation of Non-aqueous Electrolyte Solution 2", the battery was made in the same way, and the battery evaluation was performed in the same way .

Negative electrode [5] Examples 19-27

Except that the non-aqueous electrolyte solution in Examples 1-9 of the negative electrode [5] was replaced with the non-aqueous electrolyte solution produced in the item "Production of Non-aqueous Electrolyte Solution 3", the battery was made in the same way, and the battery evaluation was performed in the same way .

Negative electrode [5] Comparative Example 1

Except that the negative electrode active material of negative electrode [5] Example 1 of "Making of Negative Electrode 1" uses a carbonaceous substance (P), a battery is produced in the same manner as negative electrode [5] Example 1, and the item "Battery Evaluation" is carried out. Documented battery evaluation.

Negative electrode [5] Comparative Example 2

Except that the non-aqueous electrolyte solution of the negative electrode [5] comparative example 1 is changed into the non-aqueous electrolyte solution made in the "making 4 of the non-aqueous electrolyte solution", the battery is made in the same way as the negative electrode [5] comparative example 1, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative example 3

Except that the carbonaceous material (Q) is used as the negative electrode active material in the negative electrode [5] Example 1 of "Making of Negative Electrode 1", a battery is produced in the same manner as in negative electrode [5] Example 1, and the item "Battery Evaluation" is carried out. Documented battery evaluation.

Negative electrode [5] Comparative example 4

Except that the non-aqueous electrolyte solution of the negative electrode [5] comparative example 3 is changed into the non-aqueous electrolyte solution made in the "making 4 of the non-aqueous electrolyte solution", the battery is made in the same way as the negative electrode [5] comparative example 3, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative Example 5

Except that the carbonaceous material mixture (R) was used as the negative electrode active material in the negative electrode [5] Example 1 of "Making of the Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [5] Example 1, and "Evaluation of the Battery" was carried out. Item recorded battery evaluation.

Negative electrode [5] Comparative example 6

Except changing the non-aqueous electrolyte solution of the negative electrode [5] comparative example 5 into the non-aqueous electrolyte solution made in the item "Making 4 of the non-aqueous electrolyte solution", the battery is made in the same way as the negative electrode [5] comparative example 5, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative Example 7

Except that the non-aqueous electrolytic solution of the negative pole [5] embodiment 1 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [5] embodiment 1, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative example 8

Except that the non-aqueous electrolytic solution of the negative pole [5] embodiment 2 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [5] embodiment 2, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative example 9

Except that the non-aqueous electrolytic solution of the negative pole [5] embodiment 4 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [5] embodiment 4, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative example 10

Except that the non-aqueous electrolytic solution of the negative pole [5] embodiment 5 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [5] embodiment 5, and carried out Battery evaluation described in "Evaluation of Batteries".

Negative electrode [5] Comparative examples 11-13

Except that the non-aqueous electrolyte solution of the negative electrode [5] comparative examples 1, 3, and 5 is replaced by the non-aqueous electrolyte solution produced in the item "Making of Non-aqueous Electrolyte Solution 2", the battery is made in the same way and carried out in the same way Battery evaluation.

Negative electrode [5] Comparative examples 14-16

Except that the non-aqueous electrolyte solution of the negative electrode [5] comparative examples 1, 3, and 5 is replaced by the non-aqueous electrolyte solution made in the "Making of Non-aqueous Electrolyte Solution 3", the battery is made in the same way and carried out in the same way. Battery evaluation.

Negative electrode [5] "Battery Evaluation"

(capacity measurement)

For a battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 hour Rate (one-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. Next, the output power measurement shown below was performed.

(Low charge deep cycle test)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the practical upper limit temperature of the lithium secondary battery. Charge with 2C constant current and constant voltage method until the capacity reaches 20% of the initial capacity measured during capacity measurement, and reach the charging upper limit voltage of 4.2V, then discharge at a constant current of 2C to the end-of-discharge voltage of 3.0V, and cycle the charge and discharge As one cycle, this cycle was repeated up to 500 cycles.

For the battery after the cycle test, 3 cycles of charging and discharging were performed in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was taken as the capacity after low-charging deep cycle. The cycle retention rate was obtained from the initial capacity measured before the cycle test and the capacity after low-charge deep cycle measured after the cycle test, according to the following calculation formula.

Cycle retention (%) = 100 × capacity after low charge deep cycle / initial capacity

The list of negative electrode active materials used in the negative electrode [5] example and the negative electrode [5] comparative example is shown in the negative electrode [5] Table 1, and the results of the battery evaluation are shown in the negative electrode [5] Table 2 and the negative electrode [5] Table 3. From the results in Table 2 of the negative electrode [5] and Table 3 of the negative electrode [5], it can be seen that by containing lithium difluorophosphate, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane, and combining them as the negative electrode The hetero-oriented carbon composite of the active material can dramatically improve the capacity retention rate (cycle retention rate) after a cycle test at a low depth of charge.

Negative electrode [5] Table 1

Negative electrode [5] Table 2

[Table 44]

No. Negative active material specific compound Initial capacity mAh Low charge depth Cycle capacity mAh Cycle Retention % Example 1 Hetero-oriented carbon composite (G) Lithium difluorophosphate 6045 5592 92.5 Example 2 Hetero-oriented carbon composite (H) Lithium difluorophosphate 6032 5640 93.5 Example 3 Hetero-oriented carbon composite (I) Lithium difluorophosphate 5780 5162 89.3 Example 4 Hetero-oriented carbon composite (J) Lithium difluorophosphate 6013 5478 91.1 Example 5 Hetero-oriented carbon composite (K) Lithium difluorophosphate 6003 5427 90.4 Example 6 Hetero-oriented carbon composite (L) Lithium difluorophosphate 6009 5426 90.3 Example 7 Hetero-oriented carbon composite (M) Lithium difluorophosphate 6001 5383 89.7 Example 8 Hetero-oriented carbon composite (N) Lithium difluorophosphate 5914 5246 88.7 Example 9 Hetero-oriented carbon composite (O) Lithium difluorophosphate 5959 5375 90.2 Example 10 Hetero-oriented carbon composite (G) Trimethylsilyl methanesulfonate 6037 5410 89.6 Example 11 Hetero-oriented carbon composite (H) Trimethylsilyl methanesulfonate 6035 5441 90.2 Example 12 Hetero-oriented carbon composite (I) Trimethylsilyl methanesulfonate 5806 5058 87.1 Example 13 Hetero-oriented carbon composite (J) Trimethylsilyl methanesulfonate 6019 5346 88.8 Example 14 Hetero-oriented carbon composite (K) Trimethylsilyl methanesulfonate 5997 5241 87.4 Example 15 Hetero-oriented carbon composite (L) Trimethylsilyl methanesulfonate 6011 5300 88.2 Example 16 Hetero-oriented carbon composite (M) Trimethylsilyl methanesulfonate 6006 5233 87.1 Example 17 Hetero-oriented carbon composite (N) Trimethylsilyl methanesulfonate 5921 5104 86.2 Example 18 Hetero-oriented carbon composite (O) Trimethylsilyl methanesulfonate 5968 5101 85.5 Example 19 Hetero-oriented carbon composite (G) Hexamethylcyclotrisiloxane 6039 5767 95.5 Example 20 Hetero-oriented carbon composite (H) Hexamethylcyclotrisiloxane 6023 5580 92.6 Example 21 Hetero-oriented carbon composite (I) Hexamethylcyclotrisiloxane 5793 5208 89.9 Example 22 Hetero-oriented carbon composite (J) Hexamethylcyclotrisiloxane 6009 5364 89.3 Example 23 Hetero-oriented carbon composite (K) Hexamethylcyclotrisiloxane 6003 5349 89.1 Example 24 Hetero-oriented carbon composite (L) Hexamethylcyclotrisiloxane 6010 5306 88.3 Example 25 Hetero-oriented carbon composite (M) Hexamethylcyclotrisiloxane 5996 5413 90.3 Example 26 Hetero-oriented carbon composite (N) Hexamethylcyclotrisiloxane 5917 5275 89.1 Example 27 Hetero-oriented carbon composite (O) Hexamethylcyclotrisiloxane 5961 5500 92.3

Negative electrode [5] Table 3

[Table 45]

No. Negative active material specific compound Initial capacity mAh Low charge depth Cycle capacity mAh Cycle Retention % Comparative example 1 Carbonaceous matter (P) Lithium difluorophosphate 5890 4671 79.3 Comparative example 2 Carbonaceous matter (P) - 5873 4552 77.5 Comparative example 3 Carbonaceous matter (Q) Lithium difluorophosphate 6058 4919 81.2 Comparative example 4 Carbonaceous matter (Q) - 6067 4866 80.2 Comparative Example 5 Carbonaceous substance mixture (R) Lithium difluorophosphate 5890 4836 82.1 Comparative example 6 Carbonaceous substance mixture (R) - 5887 4739 80.5 Comparative example 7 Hetero-oriented carbon composite (G) - 6031 4915 81.5 Comparative example 8 Hetero-oriented carbon composite (H) - 6045 4975 82.3 Comparative example 9 Hetero-oriented carbon composite (J) - 5790 4713 81.4 Comparative Example 10 Hetero-oriented carbon composite (K) - 5813 4604 79.2 Comparative example 11 Carbonaceous matter (P) Trimethylsilyl methanesulfonate 5903 4728 80.1 Comparative example 12 Carbonaceous matter (Q) Trimethylsilyl methanesulfonate 6038 4921 81.5 Comparative Example 13 Carbonaceous substance mixture (R) Trimethylsilyl methanesulfonate 5900 4832 81.9 Comparative Example 14 Carbonaceous matter (P) Hexamethylcyclotrisiloxane 5940 4764 80.2 Comparative Example 15 Carbonaceous matter (Q) Hexamethylcyclotrisiloxane 6002 4874 81.2 Comparative Example 16 Carbonaceous substance mixture (R) Hexamethylcyclotrisiloxane 5970 4782 80.1

Negative electrode[6][Production of negative electrode active material]

(Production of negative electrode active material 1)

In order to prevent coarse particles from being mixed into the commercially available natural graphite powder (A), sieve was repeated 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as a carbonaceous material (B).

(Production of negative electrode active material 2)

Commercially available natural graphite powder (C) (d002: 0.336nm, Lc: 100nm or more, Raman R value: 0.11, tap density: 0.46g/cm ³ , true density: 2.27g/cm ³ , volume average particle diameter: 28.7μm), and in order to prevent mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times to prepare carbonaceous material (D).

(Production of negative electrode active material 3)

Natural graphite powder (C) is processed into a spherical shape by using a mixing system (NHS-1 type mixing system manufactured by Nara Machinery Co., Ltd.) with a processing capacity of 90 g, a rotor peripheral speed of 60 m/s, and a processing time of 3 minutes. In addition, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. The negative electrode active material thus obtained is referred to as a carbonaceous material (E). By repeating this operation, the quantity necessary for battery production is secured.

(Production of negative electrode active material 4)

Commercially available natural graphite powder (F) (d002: 0.336nm, Lc: above 100nm, Raman R value: 0.09, vibration Bulk density: 0.57g/cm ³ , true density: 2.26g/cm ³ , volume average particle diameter: 85.4μm) were spheroidized, and in order to prevent mixing of coarse particles, sieve was repeated 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as a carbonaceous material (G). By repeating this operation, the quantity necessary for battery production is secured.

(Production of negative electrode active material 5)

Coal tar pitch with a quinoline-insoluble content of 0.05% by mass or less was heat-treated in a reaction furnace at 460°C for 10 hours to obtain a meltable block-shaped carbonized precursor with a softening point of 385°C. The obtained bulk carbonized precursor was put into a metal container, and heat-treated at 1000° C. for 2 hours in a box-shaped electric furnace under nitrogen flow. The obtained amorphous block was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), and finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.) to obtain a volume-based average particle size of 18 μm of amorphous powder. In order to prevent coarse particles from being mixed into the obtained powder, the sieve was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as a carbonaceous material (H).

(Production of negative electrode active material 6)

The carbonaceous material (H) obtained in (production of negative electrode active material 5) was transferred to a graphite crucible, and graphitized at 3000° C. for 5 hours in an inert atmosphere using a direct electric furnace. In order to prevent the obtained powder from being mixed with For coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. The negative electrode active material obtained here is referred to as carbonaceous material (I).

(Production of negative electrode active material 7)

The carbonaceous material (I) obtained in (Production of Negative Electrode Active Material 6) was spheroidized using a mixing system with a treatment capacity of 90 g, a rotor peripheral speed of 30 m/s, and a treatment time of 1 minute. In addition, in order to prevent the mixing of coarse particles , use the ASTM400 mesh sieve to sieve repeatedly 5 times. The negative electrode active material thus obtained is referred to as a carbonaceous material (J). By repeating this operation, the quantity necessary for battery production is secured.

(Production of negative electrode active material 8)

Natural graphite powder (K) (d002: 0.336nm, Lc: 100nm or more, Raman R value: 0.10, tap density: 0.49g/cm ³ , true density: 2.27g) lower in purity than natural graphite powder (A) /cm ³ , volume average particle diameter: 27.3 μm, ash content: 0.5% by mass) were spheroidized and sieved under the same conditions as (preparation of negative electrode active material 3) to prepare a carbonaceous material (L). By repeating this operation, the quantity necessary for battery production is secured.

(Production of negative electrode active material 9)

In order to prevent the commercially available flaky natural graphite powder (M) from being mixed with coarse particles, it was repeatedly sieved five times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as a carbonaceous material (N).

The shape and physical properties of the carbonaceous substances (B), (D), (E), (G), (H), (I), (J), (L), and (N) were measured according to the methods described above. The results are shown in Table 1 of the negative electrode [6].

Negative electrode [6] Table 1

Negative electrode [6] [Battery production]

"Making of Positive Pole 1"

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the active material of the positive electrode at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole. The density of the active material of the negative electrode at this time was 1.35 g/cm ³ .

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

"Battery Making 1"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ). The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 20.6.

Negative electrode [6] Embodiment 1

Use the negative electrode made of carbonaceous material (D) as the negative electrode active material in the item "Making of Negative Electrode 1", the positive electrode made in the item of "Making of Positive Electrode 1", and the one made in the item of "Making of Nonaqueous Electrolyte 1" Non-aqueous electrolyte, the battery is made by the method in "Battery Production 1". The battery was measured by the method described in the following item "Evaluation of Battery" and the above-mentioned measurement method. The results are shown in Table 2 (negative electrode [6] Table 2).

Negative pole [6] embodiment 2

Except that the carbonaceous material (E) is used as the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1", a battery is produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" is carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Example 3

Except that the carbonaceous material (G) was used as the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" was carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative pole [6] embodiment 4

Except that the carbonaceous material (J) was used as the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" was carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative pole [6] embodiment 5

Except that the carbonaceous material (L) was used as the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" was carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative pole [6] Embodiment 6～10

Except that the non-aqueous electrolyte solution of Examples 1 to 5 of the negative electrode [6] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 2", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Examples 11-15

Except that the non-aqueous electrolyte solution of Examples 1 to 5 of the negative electrode [6] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 3", batteries were produced and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Example 1

Except that the carbonaceous material (B) was used as the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" was carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Example 2

Except changing the non-aqueous electrolyte solution of the negative electrode [6] comparative example 1 into the non-aqueous electrolyte solution made in the item "Making 4 of the non-aqueous electrolyte solution", the battery is made in the same way as the negative electrode [6] comparative example 1, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Example 3

Except that the non-aqueous electrolytic solution of the negative pole [6] embodiment 2 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [6] embodiment 2, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative example 4

Except that the non-aqueous electrolytic solution of the negative pole [6] embodiment 1 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution" item, the battery is made in the same way as the negative pole [6] embodiment 1, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Example 5

Except that the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1" uses a carbonaceous substance (H), a battery is produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" is carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative example 6

Except that the non-aqueous electrolyte solution of the negative electrode [6] comparative example 5 is changed into the non-aqueous electrolyte solution made in the "making 4 of the non-aqueous electrolyte solution", the battery is made in the same way as the negative electrode [6] comparative example 5, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative example 7

Except that the carbonaceous material (N) is used as the negative electrode active material in the negative electrode [6] Example 1 of "Making of the Negative Electrode 1", a battery is produced in the same manner as in the negative electrode [6] Example 1, and "Evaluation of the Battery" is carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Example 8

Except that the non-aqueous electrolytic solution of the negative pole [6] comparative example 7 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [6] comparative example 7, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative example 9

Except that the negative electrode active material in the "making of negative electrode 1" item of the negative electrode [6] embodiment 1 uses carbonaceous material (I), the battery is made in the same manner as the negative electrode [6] embodiment 1, and "evaluation of the battery" is carried out Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative example 10

Except that the non-aqueous electrolyte solution of the negative electrode [6] comparative example 9 is changed into the non-aqueous electrolyte solution made in the "making 4 of the non-aqueous electrolyte solution", the battery is made in the same way as the negative electrode [6] comparative example 9, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Examples 11-14

Except that the non-aqueous electrolytic solution of negative electrode [6] comparative examples 1, 5, 7, 9 is changed into the non-aqueous electrolytic solution made in the "making 2 of non-aqueous electrolytic solution", the battery is made in the same way respectively, and Make an evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] Comparative Examples 15-18

Except that the non-aqueous electrolytic solution of negative electrode [6] comparative examples 1, 5, 7, 9 is changed into the non-aqueous electrolytic solution made in the "making 3 of non-aqueous electrolytic solution", the battery is made in the same way respectively, and Make an evaluation. The results are shown in Table 2 of the negative electrode [6].

Negative electrode [6] "Battery Evaluation"

(capacity measurement)

For a new battery that has not undergone charge-discharge cycles, 5 cycles of initial charge-discharge (voltage range 4.1V-3.0V) were performed at 25°C in a voltage range of 4.1V-3.0V. The 0.2C discharge capacity of the 5th cycle at this time (the current value of the 1-hour discharge rated capacity is taken as 1C, and the rated capacity depends on the discharge capacity of the 1-hour-rate (one-hour-rate), the same below) discharge capacity as initial capacity.

(Output power measurement 1)

At 25°C, charge with a constant current of 0.2C for 150 minutes, stand at -30°C for 3 hours, and then discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 5.0C for 10 seconds , Measure the voltage at the 10th second. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the initial low temperature output power (W).

(Output power measurement 2)

After output power measurement 1, implement low-voltage charging at 4.1V for 1 hour, then transfer the battery to an environment at 25°C, and after 15 minutes, discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 5.0C for 10 seconds clock, measure the voltage at the 10th second. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the output power (W) when the temperature rises.

From the results of the output measurement 1 and the output measurement 2, the temperature adaptation output improvement rate (%) was calculated by the following calculation formula.

Temperature adaptation output power increase rate (%)

＝[(Output power when temperature rises (W)/Initial low temperature output power (W))-1]×100

The impedance Rct and the double-layer capacity Cdl in Table 2 of the negative electrode [6] are one of the parameters that contribute to the output power. The smaller the value of the impedance Rct, or the larger the value of the double-layer capacity Cdl, the more the output power will be improved. tendency. In addition, "impedance Rct" and "double layer capacity Cdl" were obtained by the method described in the section describing impedance.

Negative electrode [6] Table 2

[Table 47]

No. Negative active material Carbonaceous material specific compound Initial Low Temperature Output Power W Output power when temperature rises W Temperature Adaptation Output Power Increase Rate % Impedance Rct Ω Double layer capacity Cdl ×10^-4F Example 1 (D) Lithium difluorophosphate 21.7 29.0 33 6 0.8 Example 2 (E) Lithium difluorophosphate 22.2 31.0 40 8 0.6 Example 3 (G) Lithium difluorophosphate 20.0 24.9 twenty four 13 0.5 Example 4 (J) Lithium difluorophosphate 21.5 27.6 28 100 0 Example 5 (L) Lithium difluorophosphate 21.9 29.6 35 8 0.5 Example 6 (D) Trimethylsilyl methanesulfonate 21.6 27.7 28 9 1 Example 7 (E) Trimethylsilyl methanesulfonate 21.9 29.1 33 11 0.9 Example 8 (G) Trimethylsilyl methanesulfonate 20.2 24.5 twenty one twenty two 0.6 Example 9 (J) Trimethylsilyl methanesulfonate 21.2 25.9 twenty two 135 0 Example 10 (L) Trimethylsilyl methanesulfonate 21.9 28.7 31 10 1 Example 11 (D) Hexamethylcyclotrisiloxane 22.0 27.9 27 9 0.9 Example 12 (E) Hexamethylcyclotrisiloxane 22.1 30.2 37 9 0.6 Example 13 (G) Hexamethylcyclotrisiloxane 20.1 24.1 20 20 0.5 Example 14 (J) Hexamethylcyclotrisiloxane 21.3 25.8 twenty one 121 0 Example 15 (L) Hexamethylcyclotrisiloxane 21.5 29.2 36 9 0.7 Comparative example 1 (B) Lithium difluorophosphate 21.1 24.7 17 7 1 Comparative example 2 (B) - 20.0 21.1 5 13 1.2 Comparative example 3 (E) - 20.5 22.7 11 10 0.9 Comparative example 4 (D) - 21.5 23.4 9 10 1 Comparative Example 5 (H) Lithium difluorophosphate 21.3 23.0 8 36 0.2 Comparative example 6 (H) - 20.7 21.2 2 50 0.3 Comparative example 7 (N) Lithium difluorophosphate 19.4 21.4 10 11 0.8 Comparative example 8 (N) - 19.0 20.1 6 16 0.7 Comparative example 9 (I) Lithium difluorophosphate 17.5 19.5 11 125 0 Comparative Example 10 (I) - 17.1 18.3 7 160 0 Comparative example 11 (B) Trimethylsilyl methanesulfonate 21.1 24.7 14 7 1.1 Comparative example 12 (H) Trimethylsilyl methanesulfonate 21.3 23.0 5 44 0.3 Comparative Example 13 (N) Trimethylsilyl methanesulfonate 19.4 21.4 7 13 0.7 Comparative Example 14 (I) Trimethylsilyl methanesulfonate 17.5 19.4 9 131 0 Comparative Example 15 (B) Hexamethylcyclotrisiloxane 21.1 24.7 15 9 1.4 Comparative Example 16 (H) Hexamethylcyclotrisiloxane 21.3 23.0 6 42 0.4 Comparative Example 17 (N) Hexamethylcyclotrisiloxane 19.4 21.4 9 13 0.4 Comparative Example 18 (I) Hexamethylcyclotrisiloxane 17.5 19.4 10 142 0

From the results in Table 2 of the negative electrode [6], it can be seen that by containing lithium difluorophosphate, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane, and containing a circularity of 0.85 or more, a wide-angle X The graphitic carbon particles whose interplanar distance (d002) of the (002) plane measured by the ray diffraction method is less than 0.337 and whose Raman R value is 0.12 to 0.8 are used as the negative electrode active material, which can increase the output power at a low temperature of -30°C. Recovery is dramatically accelerated with increasing temperature.

Negative electrode [7] <Production of negative electrode>

(Making of Negative Electrode 1)

A mixture of Si and C (circular plate with an area ratio of Si and C of approximately 100:9) was used as the target material, and the average surface roughness (Ra) was 0.2 μm, the tensile strength was 280 N/mm ² , and the tensile strength was 0.2%. Electrolytic copper foil with a thickness of 220 N/mm ² and a thickness of 18 μm was used as a current collector substrate, and a DC sputtering device ("HSM-52" manufactured by Shimadzu Corporation) was used to form a thin film of active material for 45 minutes to obtain a thin film negative pole (1).

At this time, the current collector substrate was mounted on a water-cooled jig and kept at about 25°C. The container was pre-vacuum-pumped to 4× ^10-4 Pa, and 40 sccm of high-purity argon gas was circulated in the container, and the main valve was adjusted. After the opening degree became an atmosphere of 1.6 Pa, film formation was performed at a power density of 4.7 W/cm ² and a deposition rate (film formation rate) of about 1.8 nm/sec (0.108 μm/min). The oxygen concentration of the sputtering gas was 0.0010%. In addition, in order to remove the oxide film on the surface of the electrolytic copper foil, reverse sputtering and etching of the substrate surface are performed before thin film formation.

Scanning electron microscope (SEM) observation of the cross-section of the thin film of the obtained thin film negative electrode (1) revealed that the film thickness of the formed thin film was 6 μm (see FIG. 1( a )). In addition, when the composition analysis of the thin film was performed by XPS according to the following method, the element C contained in the thin film was 24 atomic %, and the C concentration ratio Q(C) to the element C concentration in SiC corresponded to 0.49. In addition, when represented by an atomic concentration ratio, Si/C/O=1.00/0.33/0.04. In addition, when the Raman value of the thin film was obtained by Raman measurement according to the following method, RC=0.05, the peak of RSC=sc was not detected, and RS=0.55. In addition, when X-ray diffraction measurement of the thin film was performed according to the following method, no clear peak of SiC was detected, and XIsz=0.38. The results are shown in Table 1 of the negative electrode [7].

In addition, when the electron probe microanalyzer (EPMA) is used to measure the mass concentration distribution of Si in the film thickness direction in the film according to the following method, as shown in Figure 1(b), the maximum or minimum value and the average value of Si If the difference (absolute value) is within 25%, Si is formed into a film substantially continuously from the current collector. In addition, when the distribution of element C in the thin film was measured, as shown in FIG. 1( c ), element C was uniformly distributed in the Si thin film with a size of 1 μm or less.

(Making of Negative Electrode 2)

Except for using Si as the target material, an active material thin film was formed in the same manner as in (Preparation of Negative Electrode 1), and a thin-film negative electrode (2) was produced.

Observation with a scanning electron microscope (SEM) of the cross section of the thin film of the obtained thin film negative electrode (2) revealed that the thickness of the thin film after film formation was 6 μm. In addition, when the composition analysis of the thin film is carried out, the elements C and N are not contained in the thin film, and Si/O=1.00/0.02 when represented by the atomic concentration ratio. In addition, when the Raman value of the thin film was obtained, the peak of RC=c was not detected, the peak of RSC=sc was not detected, and RS=0.30. The results are shown in Table 1 of the negative electrode [7].

<XPS measurement>

As X-ray photoelectric spectrometry measurement, use an X-ray photoelectric spectrometer (for example, "ESCA" manufactured by ulvac-phi Co., Ltd.), place a thin-film negative electrode on a sample table and make the surface flat, and use Kα rays of aluminum as X-rays. Source, depth profile measurement was performed while performing Ar sputtering. Obtain the spectra of Si2p (90-110eV), C1s (280-300eV) and O1s (525-545eV) at a certain concentration depth (for example, 200nm). Set the peak top of the obtained C1s to 284.5eV to perform charge compensation, obtain the peak areas of the spectra of Si2p, C1s and O1s, and multiply them by the device sensitivity coefficient to calculate the atomic concentrations of Si, C and O, respectively. The atomic concentration ratio Si/C/O (Si atomic concentration/C atomic concentration/O atomic concentration) was calculated from the obtained atomic concentrations of Si, O, and C, and this was defined as the thin film composition value Si/C/O.

<Raman measurement>

For Raman measurement, a Raman spectrometer (for example, "Raman spectrometer" manufactured by JASCO Corporation) is used, a thin-film negative electrode is installed in a measurement cell, and the measurement is performed by irradiating the surface of the sample in the cell with an argon ion laser.

In addition, the Raman measurement conditions here are as follows.

Argon ion laser wavelength: 514.5nm

·Laser power on the sample: 15~40mW

·Resolution: 10～20cm ^-1

· Measuring range: 200cm ^-1 ~ 1900cm ^-1

·Smooth processing: simple average, convolution 15 points

<X-ray Diffraction Measurement>

As the X-ray diffraction measurement, "RINT2000PC" manufactured by Rigaku Corporation was used, and the thin-film negative electrode was set in the measurement cell, and the measurement in the range of 2θ=10 to 70 degrees was performed using the out-of-plane method. The background compensation is performed by connecting the vicinity of 2θ=15 to 20 degrees and the vicinity of 40 to 45 degrees with a straight line.

<EPMA measurement>

As the mass concentration distribution in the film thickness direction measured by EPMA or the distribution analysis of the film cross section, an electron probe microanalyzer ("JXA-8100" manufactured by JEOL Co., Ltd.) was used to make a microtome without resin embedding. Cross-sectional thin film anodes were subjected to elemental analysis from the current collector to the film surface. When obtaining the mass concentration distribution in the film thickness direction, the value obtained by converting the sum of the measured elements into 100% is used to obtain the mass concentration distribution of Si in the film thickness direction.

Negative electrode [7] Table 1

[Table 48]

Negative electrode [7] In Table 1, (Si) does not correspond to element Z.

Negative electrode [7] <Production of positive electrode>

(Making of positive electrode 1)

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on one side of an aluminum foil having a thickness of 15 μm, dried, and rolled to a thickness of 80 μm with a press.

Negative electrode [7] <Preparation of non-aqueous electrolyte>

(Preparation of non-aqueous electrolyte solution 1)

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

(Preparation of non-aqueous electrolyte solution 2)

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

(Preparation of non-aqueous electrolyte solution 3)

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

(Preparation of non-aqueous electrolyte solution 4)

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

Negative electrode [7] <Production of lithium secondary battery>

The negative and positive electrodes of the film were punched into 10mmφ, and after vacuum drying at 110°C, they were transferred to a glove box. Water electrolyte, making 2032 type coin battery (lithium secondary battery).

Negative pole [7] embodiment 1

Using the negative electrode prepared in (Making of Negative Electrode 1), the positive electrode prepared in (Making of Positive Electrode) and the nonaqueous electrolyte prepared in (Making of Nonaqueous Electrolyte 1), pass the "Making of Lithium Secondary Battery" "The method in item makes coin battery. The battery characteristics of the secondary battery were determined by the method described in the following item <Battery Evaluation>.

Negative pole [7] embodiment 2

Except that the non-aqueous electrolytic solution of the negative pole [7] embodiment 1 is changed into the non-aqueous electrolytic solution made in the item (making 2 of the non-aqueous electrolytic solution), the battery is made in the same way as the negative pole [7] embodiment 1, and adopts The battery was evaluated by the method described in the item <Battery Evaluation>. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] Example 3

Except that the non-aqueous electrolytic solution of the negative pole [7] embodiment 1 is changed into the non-aqueous electrolytic solution made in the item (making 3 of the non-aqueous electrolytic solution), the battery is made in the same way as the negative pole [7] embodiment 1, and adopts The battery was evaluated by the method described in the item <Battery Evaluation>. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] Comparative example 1

Except that the non-aqueous electrolytic solution of the negative pole [7] embodiment 1 is changed into the non-aqueous electrolytic solution made in the item (making 4 of the non-aqueous electrolytic solution), the battery is made in the same way as the negative pole [7] embodiment 1, and adopts The battery was evaluated by the method described in the item <Battery Evaluation>. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] Comparative Example 2

Except that the negative electrode of negative electrode [7] Example 1 was replaced with the electrode produced in item (Making of Negative Electrode 2), a battery was produced in the same manner as negative electrode [7] Example 1, and the method described in the item <Battery Evaluation> was adopted. Perform battery evaluation. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] Comparative example 3

Except that the non-aqueous electrolytic solution of the negative pole [7] comparative example 2 is changed into the non-aqueous electrolytic solution made in the item (making 2 of the non-aqueous electrolytic solution), the battery is made in the same way as the negative pole [7] comparative example 2, and adopts The battery was evaluated by the method described in the item <Battery Evaluation>. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] Comparative example 4

Except that the non-aqueous electrolytic solution of the negative pole [7] comparative example 2 is changed into the non-aqueous electrolytic solution made in (making 3 of the non-aqueous electrolytic solution), the battery is made in the same way as the negative pole [7] comparative example 2, and adopts The battery was evaluated by the method described in the item <Battery Evaluation>. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] Comparative Example 5

Except that the non-aqueous electrolytic solution of the negative pole [7] comparative example 2 is changed into the non-aqueous electrolytic solution made in the item (making 4 of the non-aqueous electrolytic solution), the battery is made in the same way as the negative pole [7] comparative example 2, and adopts The method described in "Battery Evaluation" item was used for battery evaluation. The results are shown in Table 2 of the negative electrode [7].

Negative electrode [7] <Evaluation of battery>

The evaluation of the discharge capacity and the measurement of the charge acceptance were performed on the coin cell produced in the section of <Preparation of Lithium Secondary Battery> according to the following methods.

"Evaluation of Discharge Capacity"

Charge the lithium counter electrode to 4.2V at a current density of 1.23mA/ ^cm2 , and then charge it at a constant voltage of 4.2V until the current value reaches 0.123mA. After doping the negative electrode with lithium, charge it at a current density of 1.23mA/ ^cm2 The lithium counter electrode was discharged to 2.5 V, and this charge-discharge cycle was repeated 5 times, and the average value of the discharges in the 3rd to 5th cycles was taken as the discharge capacity. In addition, in the case of the discharge capacity per unit mass, the mass of the active material can be obtained by subtracting the mass of copper foil punched into the same area from the mass of the negative electrode, and calculated according to the following formula.

Discharge capacity (mAh/g)

=[Average discharge capacity of the 3rd to 5th cycle (mAh)]/[Active material mass (g)]

Active material mass (g) = negative electrode mass (g) - copper foil mass (g) with the same area

"Determination of Charge Acceptance"

In an environment of 25°C, it will be charged to 4.2C at 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on the discharge capacity of 1 hour rate (one-hour-rate), the same below). The capacity at V is taken as the 0.2C charging capacity, and then discharged to 2.5V at 0.2C, and then charged to 4.2V at 1C, and the capacity at this time is taken as the 1C charging capacity. The charge acceptance was calculated|required from the obtained result by the following formula.

Charging acceptance (%) = 100×[1C charging capacity]/[0.2C charging capacity]

Negative electrode [7] Table 2

[Table 49]

From the results of the negative electrode [7] Table 2, it can be seen that lithium difluorophosphate, trimethylsilyl methanesulfonate or hexamethylcyclotrisiloxane are contained in the non-aqueous electrolyte, and using polyelement-containing The negative electrode active material (C') as the lithium secondary battery of the negative electrode active material can dramatically improve the charge acceptance, and the multi-element negative electrode active material (C') contains at least one lithium storage metal ( A') and/or lithium storage alloy (B'), and contains at least one element (element Z) selected from C or N.

Negative electrode[8][Production of negative electrode active material]

(Production of negative electrode active material 1)

Use a mixing system (the mixing system NHS-1 type manufactured by Nara Machinery Manufacturing Co., Ltd.) to treat natural graphite powder (d002: 0.336nm, Lc: 100nm or more, Raman R value: 0.11, tap density: 0.46g/cm ³ , true density: 2.27g/cm ³ , volume-based average particle size: 35.4μm) to spheroidize, and to To prevent mixing of coarse particles, use an ASTM400 mesh sieve to sieve repeatedly 5 times. The negative electrode active material thus obtained is referred to as a carbonaceous material (A). By repeating this operation, the quantity necessary for battery production is secured.

(Production of negative electrode active material 2)

The commercially available flaky natural graphite powder was removed with a wind classifier, and in order to prevent the obtained powder from being mixed with coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times. The negative electrode active material thus obtained is referred to as a carbonaceous material (B).

(Production of negative electrode active material 3)

Coal tar pitch with a quinoline insoluble content of 0.05% by mass or less was heat-treated in a reaction furnace at 460°C for 10 hours to obtain a fusible bulk carbonized precursor with a softening point of 385°C. The obtained massive carbonized precursor was put into a metal container, and heat-treated at 1000° C. for 2 hours in a box-shaped electric furnace under a flow of nitrogen gas. The resulting amorphous lump was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.), and then fine powder was removed with a wind classifier , in order to prevent the obtained powder from being mixed with coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times to obtain an amorphous powder with a volume reference particle size of 9 μm. The negative electrode active material thus obtained is referred to as a carbonaceous material (C).

(Production of negative electrode active material 4)

Petroleum heavy oil obtained during the pyrolysis of naphtha is mixed with the carbonaceous substance (A), carbonized at 1300°C in an inert gas, and then the carbonaceous substance is obtained by classifying the sintered product. The carbonaceous substance is a carbonaceous substance obtained by coating the carbonaceous substance (A) particle surface with a carbonaceous substance having a different crystallinity. During the classification process, in order to prevent mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain the carbonaceous material (D). It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of carbon derived from petroleum heavy oil relative to 95 parts by weight of graphite.

(Production of negative electrode active material 5)

80% by mass of the carbonaceous substance (A) and 20% by mass of the carbonaceous substance (B) were mixed until uniform to obtain a mixed carbonaceous substance (E).

(Production of negative electrode active material 6)

95% by mass of the carbonaceous substance (A) and 5% by mass of the carbonaceous substance (C) were mixed until uniform to obtain a mixed carbonaceous substance (F).

(Production of negative electrode active material 7)

80% by mass of the carbonaceous substance (D) and 20% by mass of the carbonaceous substance (A) were mixed until uniform to obtain a mixed carbonaceous substance (G).

The physical properties and shapes of the carbonaceous materials (A), (B), (C) and mixed carbonaceous materials (E), (F), (G) prepared in the production of negative electrode active materials 1 to 7 were obtained by the above method wait. The results are summarized in Table 1 of the negative electrode [8].

Negative electrode [8] Table 1

Negative electrode [8] [Battery production]

"Making of Positive Pole 1"

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the active material of the positive electrode at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole. The density of the active material of the negative electrode at this time was 1.35 g/cm ³ .

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

"Battery Making 1"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ). The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 20.6.

Negative pole [8] embodiment 1

The negative electrode produced by using the negative electrode active material in "Making of Negative Electrode 1" as a mixed carbonaceous material (E), the positive electrode produced in "Making of Positive Electrode 1" and the one produced in "Making of Nonaqueous Electrolyte 1" Non-aqueous electrolyte, the battery is made by the method in "Battery Production 1". The batteries were subjected to the battery evaluations described in the item "Evaluation of Batteries" below. The results are shown in Table 2 of the negative electrode [8].

Negative pole [8] embodiment 2

Except that the negative electrode active material of negative electrode [8] Example 1 of "Making of Negative Electrode 1" uses a mixed carbonaceous material (F), a battery is produced in the same manner as negative electrode [8] Example 1, and "Battery Evaluation" is carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Example 3

Except that the mixed carbonaceous material (G) was used as the negative electrode active material in the negative electrode [8] Example 1 of "Making of the Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [8] Example 1, and "Evaluation of the Battery" was carried out. Item recorded battery evaluation. The results are shown in Table 2 of the negative electrode [8].

Negative pole [8] Embodiment 4～6

Except that the non-aqueous electrolyte solution of Examples 1 to 3 of the negative electrode [8] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 2", batteries were produced in the same way, and battery evaluation was performed. The results are shown in Table 2 of the negative electrode [8].

Negative pole [8] Embodiment 7～9

Except that the non-aqueous electrolyte solution of Examples 1 to 3 of the negative electrode [8] was replaced with the non-aqueous electrolyte solution produced in the item "Preparation of Non-aqueous Electrolyte Solution 3", batteries were produced in the same way, and battery evaluation was performed. The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative Example 1

Except that the non-aqueous electrolytic solution of the negative pole [8] embodiment 1 is changed into the non-aqueous electrolytic solution made in the "making 4 of non-aqueous electrolytic solution" item, the battery is made in the same way as the negative pole [8] embodiment 1, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative Example 2

Except that the non-aqueous electrolytic solution of the negative pole [8] embodiment 2 is changed into the non-aqueous electrolytic solution made in the "making 4 of the non-aqueous electrolytic solution", the battery is made in the same way as the negative pole [8] embodiment 2, and carried out Battery evaluation described in "Evaluation of Batteries". The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative Example 3

Except that the carbonaceous material (A) was used as the negative electrode active material in the negative electrode [8] Comparative Example 1 of "Preparation of Negative Electrode 1", a battery was produced in the same manner as in the negative electrode [8] Comparative Example 1, and the item "Evaluation of the Battery" was carried out. Documented battery evaluation. The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative example 4

Except that the carbonaceous material (B) was used as the negative electrode active material in the negative electrode [8] Comparative Example 1 of "Preparation of the Negative Electrode 1", a battery was produced in the same manner as the negative electrode [8] Comparative Example 1, and the "Evaluation of the Battery" item was carried out. Documented battery evaluation. The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative example 5

Except that the carbonaceous material (C) was used as the negative electrode active material in the negative electrode [8] Comparative Example 1 "Negative Electrode Production 1", a battery was produced in the same manner as the negative electrode [8] Comparative Example 1, and the "Battery Evaluation" item was carried out. Documented battery evaluation. The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative examples 6-8

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolytes of Comparative Examples 3 to 5 of the negative electrode [8] were replaced with the non-aqueous electrolytes prepared in the item "Preparation of Non-aqueous Electrolyte 1". The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative Examples 9-11

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolyte solutions of Comparative Examples 3 to 5 of the negative electrode [8] were replaced with the non-aqueous electrolyte solutions produced in the item "Preparation of Non-aqueous Electrolyte Solutions 2". The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] Comparative Examples 12-14

Batteries were produced and evaluated in the same manner, except that the non-aqueous electrolyte solutions of Comparative Examples 3 to 5 of the negative electrode [8] were replaced with the non-aqueous electrolyte solutions produced in the item "Preparation of Non-aqueous Electrolyte Solutions 3". The results are shown in Table 2 of the negative electrode [8].

Negative electrode [8] "Battery Evaluation"

(capacity measurement)

For a new battery that has not undergone charge-discharge cycles, 5 cycles of initial charge-discharge (voltage range 4.1V-3.0V) were performed at 25°C in a voltage range of 4.1V-3.0V. The 0.2C discharge capacity of the 5th cycle at this time (the current value of the 1-hour discharge rated capacity is taken as 1C, and the rated capacity depends on the discharge capacity of the 1-hour-rate (one-hour-rate), the same below) discharge capacity as initial capacity.

(Output power measurement 1)

At 25°C, charge with a constant current of 0.2C for 150 minutes, stand at -30°C for 3 hours, and then discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 5.0C for 10 seconds , Measure the voltage at the 10th second. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the low-temperature output power (W).

(cycle test)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the practical upper limit temperature of the lithium secondary battery. Charge to the charging upper limit voltage of 4.2V by the constant current and constant voltage method of 2C, and then discharge to the end-of-discharge voltage of 3.0V by the constant current of 2C. The charge-discharge cycle is regarded as one cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, 3 cycles of charging and discharging were performed in an environment of 25° C., and the 0.2 C discharge capacity of the third cycle was taken as the capacity after cycle. The cycle retention rate was obtained from the initial capacity measured before the cycle test and the post-cycle capacity measured after the cycle test was completed according to the following calculation formula.

Cycle retention (%) = 100 × capacity after cycle / initial capacity

Negative electrode [8] Table 2

[Table 51]

NO. Negative active material specific compound Low temperature output power W Cycle Retention % Example 1 Mixed carbonaceous matter (E) Lithium difluorophosphate 26.2 81 Example 2 Mixed carbonaceous matter (F) Lithium difluorophosphate 27.4 80 Example 3 Mixed carbonaceous matter (G) Lithium difluorophosphate 29.4 85 Example 4 Mixed carbonaceous matter (E) Trimethylsilyl methanesulfonate 24.7 80 Example 5 Mixed carbonaceous matter (F) Trimethylsilyl methanesulfonate 28.2 78 Example 6 Mixed carbonaceous matter (G) Trimethylsilyl methanesulfonate 29.7 84 Example 7 Mixed carbonaceous matter (E) Hexamethylcyclotrisiloxane 26.1 80 Example 8 Mixed carbonaceous matter (F) Hexamethylcyclotrisiloxane 29.1 77 Example 9 Mixed carbonaceous matter (G) Hexamethylcyclotrisiloxane 28.8 84 Comparative example 1 Mixed carbonaceous matter (E) - 21.1 78 Comparative example 2 Mixed carbonaceous matter (F) - 23.2 75 Comparative example 3 Carbonaceous matter (A) - 20.5 77 Comparative example 4 Carbonaceous matter (B) - 24.5 71 Comparative Example 5 Carbonaceous matter (C) - 27.5 69 Comparative example 6 Carbonaceous matter (A) Lithium difluorophosphate 22.2 79 Comparative example 7 Carbonaceous matter (B) Lithium difluorophosphate 25.8 72 Comparative example 8 Carbonaceous matter (C) Lithium difluorophosphate 29.4 70 Comparative example 9 Carbonaceous matter (A) Trimethylsilyl methanesulfonate 21.7 80 Comparative Example 10 Carbonaceous matter (B) Trimethylsilyl methanesulfonate 25.2 72 Comparative example 11 Carbonaceous matter (C) Trimethylsilyl methanesulfonate 28.8 70 Comparative example 12 Carbonaceous matter (A) Hexamethylcyclotrisiloxane 21.7 78 Comparative Example 13 Carbonaceous matter (B) Hexamethylcyclotrisiloxane 24.5 72

NO. Negative active material specific compound Low temperature output power W Cycle Retention % Comparative Example 14 Carbonaceous matter (C) Hexamethylcyclotrisiloxane 28.2 69

From the results in Table 2 of the negative electrode [8], it can be seen that by containing lithium difluorophosphate, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane, and using two or more negative electrodes with different properties The negative electrode of the material, cycle characteristics and low temperature output power are all good.

Negative electrode[9][10][Production of negative electrode active material]

(Production of negative electrode active material 1)

Highly purified flaky natural graphite with a median diameter of about 150 μm (d002: 0.336 nm, Lc: 100 nm or more, Raman R value: 0.11, true density: 2.27g/cm ³ , ash content: 0.05% by mass) to spheroidize for 5 minutes, and then use an air classifier (OMC-100 manufactured by Seishin Enterprise Co., Ltd.) to remove 45% by mass of fine powder to obtain carbon Substance (A).

(Production of negative electrode active material 2)

The carbonaceous material (A) produced in (Production of Negative Electrode Active Material 1) was charged into a graphite crucible, and heat-treated at 3000° C. for 5 hours in an inert atmosphere using a direct electric furnace to obtain a carbonaceous material (B).

(Production of negative electrode active material 3)

The petroleum-based heavy oil obtained during the pyrolysis of naphtha is mixed with the carbonaceous material (A) produced in (production of negative electrode active material 1), and carbonization treatment at 1300° C. is carried out in an inert gas, and then the sintered product is The classification process yields a carbonaceous substance in which carbonaceous substances having different crystallinity are coated on the surface of the carbonaceous substance (A) particles. During the classification process, in order to prevent mixing of coarse particles, the ASTM400 mesh sieve was used to repeatedly sieve 5 times to obtain carbonaceous material (C). It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of carbon derived from petroleum heavy oil relative to 95 parts by weight of graphite.

(Production of negative electrode active material 4)

Coal tar pitch with a quinoline insoluble content of 0.05% by mass or less was heat-treated in a reaction furnace at 460°C for 10 hours to obtain a fusible bulk carbonized precursor with a softening point of 385°C. The obtained massive carbonized precursor was put into a metal container, and heat-treated at 1000° C. for 2 hours in a box-shaped electric furnace under a flow of nitrogen gas. The obtained amorphous block was pulverized with a coarse pulverizer (roller crusher manufactured by Yoshida Seisakusho), and finely pulverized with a fine pulverizer (turbine mill manufactured by Matsubo Co., Ltd.) to obtain a volume-based average particle size of 17 μm of amorphous powder. In order to prevent coarse particles from being mixed into the obtained powder, the sieve was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode active material thus obtained is referred to as a carbonaceous material (D).

The shapes and physical properties of the produced carbonaceous substance (A), carbonaceous substance (B), carbonaceous substance (C) and carbonaceous substance (D) were measured by the method described above. The results are shown in Table 1 for negative electrodes [9][10].

Negative electrode [9] [10] Table 1

[Table 52]

Negative active material Vibration Density g/cm³ Micropore Volume mL/g Total Micropore Volume mL/g Volume Average Particle Size μm Circularity - BET specific surface area m²/g Raman R value - Raman Half Value Width cm^-1 Interplanar distance d002 nm Crystalline size Lc nm Ash % True Density g/cm³ Length diameter ratio - Carbonaceous matter (A) 0.99 0.228 0.78 16.5 0.94 7.5 0.27 24.0 0.335 ＞100 0.05 2.26 1.1 Carbonaceous matter (B) 1.00 0.215 0.75 17.0 0.94 5.4 0.03 20.5 0.335 ＞100 0.02 2.26 1.1 Carbonaceous matter (C) 1.08 0.203 0.68 16.5 0.93 2.7 0.35 34.0 0.336 ＞100 0.07 2.25 1.2 Carbonaceous matter (D) 0.91 0.079 0.45 16.6 0.89 5.9 1.05 91.0 0.343 2.3 0.05 1.91 1.9

Negative electrode[9][10][Battery production]

"Making of Positive Pole 1"

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and then cut into a positive electrode active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the positive electrode active material layer of the positive electrode at this time was 2.35 g/cm ³ .

"Making of Negative Pole 1"

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener (the concentration of sodium carboxymethylcellulose is 1% by mass) and 2 parts by weight of sodium carboxymethylcellulose as a binder in 98 parts by weight of the negative electrode active material. An aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press, and then cut into a negative electrode active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

The density of the negative electrode active material layer of the negative electrode at this time was in the range of 1.33 to 1.36 g/cm ³ (respectively shown in the rightmost column of Table 2 of negative electrodes [9] and [10]). From the above, it can be seen that the content of the styrene-butadiene rubber as a binder in the negative electrode active material layer is 1% by mass relative to the entire negative electrode active material layer. In addition, the value of [(thickness of negative electrode active material layer on one surface)/(thickness of current collector)] was 75 μm/10 μm=7.5.

"Preparation of non-aqueous electrolyte 1"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of lithium difluorophosphate (LiPO ₂ F ₂ ) was contained.

"The production of non-aqueous electrolyte 2"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1 mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of trimethylsilyl methanesulfonate was contained.

"The Production of Non-aqueous Electrolyte 3"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"The Production of Non-aqueous Electrolyte 4"

Under a dry argon atmosphere, in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3:3:4), at a concentration of 1mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ).

"Battery Making 1"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ). The ratio of the sum of the electrode areas of the positive electrode to the sum of the surface areas of the battery case was 20.6.

Negative electrode [9] [10] Example 1

Use the negative electrode active material of " the making of negative electrode 1 " item to be the negative electrode made of carbonaceous material (A), the positive electrode made in the " making of positive electrode 1 " item and the nonaqueous electrolyte made in the item of " making 1 " The water electrolyte is used to make a battery by the method in "Battery Production 1". The battery was measured by the method described in the item "Evaluation of the battery" below. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 2

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 1 is changed into the non-aqueous electrolytic solution made in the "making 2 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 1 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 3

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 1 is changed into the non-aqueous electrolytic solution made in the "making 3 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 1 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Comparative Example 1

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 1 is changed into the non-aqueous electrolytic solution made in the "making 4 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 1 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 4

Except that negative pole [9] [10] embodiment 1 " making of negative pole 1 " item negative pole active material uses carbonaceous material (B), according to the same method as negative pole [9] [10] embodiment 1, make battery, and evaluate in the same way. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 5

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 4 is changed into the non-aqueous electrolytic solution made in the "making 2 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 4 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 6

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 4 is changed into the non-aqueous electrolytic solution made in the "making 3 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 4 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Comparative example 2

Except that the non-aqueous electrolytic solution of negative pole [9] [10] embodiment 4 is changed into the non-aqueous electrolytic solution made in " making 4 of non-aqueous electrolytic solution ", according to negative pole [9] [10] embodiment 4 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 7

Except negative electrode [9] [10] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses carbonaceous material (C), according to the same method as negative electrode [9] [10] embodiment 1, make battery, and evaluate in the same way. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 8

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 7 is changed into the non-aqueous electrolytic solution made in the "making 2 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 7 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 9

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 7 is changed into the non-aqueous electrolytic solution made in the "making 3 of non-aqueous electrolytic solution" item, according to the negative pole [9] [10] embodiment 7 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Comparative example 3

Except changing the non-aqueous electrolytic solution of negative pole [9] [10] embodiment 7 into the non-aqueous electrolytic solution made in " making 4 of non-aqueous electrolytic solution " item, according to negative pole [9] [10] embodiment 7 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 10

Except negative electrode [9] [10] embodiment 1 " making of negative electrode 1 " item negative electrode active material uses carbonaceous material (D), according to the same method as negative electrode [9] [10] embodiment 1, make battery, and evaluate in the same way. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 11

Except that the non-aqueous electrolytic solution of the negative pole [9] [10] embodiment 10 is changed into the non-aqueous electrolytic solution made in the "making of non-aqueous electrolytic solution 2" item, according to the negative pole [9] [10] embodiment 10 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Example 12

Except that the non-aqueous electrolytic solution of negative pole [9] [10] embodiment 10 is changed into the non-aqueous electrolytic solution made in " making 3 of non-aqueous electrolytic solution " item, according to negative pole [9] [10] embodiment 10 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode [9] [10] Comparative Example 4

Except changing the non-aqueous electrolytic solution of negative pole [9] [10] embodiment 10 into the non-aqueous electrolytic solution made in " making 4 of non-aqueous electrolytic solution " item, according to negative pole [9] [10] embodiment 10 Batteries were produced in the same manner and evaluated in the same manner. The results are shown in Table 2 of the negative electrode [9][10].

Negative electrode[9][10] "Battery Evaluation"

(capacity measurement)

For a battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 hour Rate (one-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. Next, the output power measurement shown below was performed.

(Output power measurement)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the output power (W). Let the output power before the cycle test be the "initial output power".

(cycle test)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the practical upper limit temperature of the lithium secondary battery. Charge to the charging upper limit voltage of 4.2V by the constant current and constant voltage method of 2C, and then discharge to the end-of-discharge voltage of 3.0V by the constant current of 2C. The charge-discharge cycle is regarded as one cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, 3 cycles of charging and discharging were performed in an environment of 25° C., and the 0.2 C discharge capacity of the third cycle was taken as the capacity after cycle. The cycle retention rate was obtained from the initial capacity measured before the cycle test and the post-cycle capacity measured after the cycle test was completed according to the following calculation formula.

Cycle retention (%) = 100 × capacity after cycle / initial capacity

The impedance Rct and the double-layer capacity Cdl in Table 2 of the negative electrode [9][10] are one of the parameters that contribute to the output power. The smaller the value of the impedance Rct, or the larger the value of the double-layer capacity Cdl, the higher the output power. There is a tendency to improve. In addition, "impedance Rct" and "double layer capacitance Cdl" were obtained by the method described in the section describing impedance.

The output power measurement described in the above item (measurement of output power) was performed on the battery after the cycle test, and the obtained value was taken as "output power after cycle test". The output power measurement results, capacity measurement results, cycle retention ratio, and the above-mentioned counter impedance measurement of the lithium secondary batteries of the negative electrode [9] [10] examples and the negative electrode [9] [10] comparative examples. The measurement results of reaction resistance and double-layer capacity are summarized in Table 2 of the negative electrode [9][10].

Negative pole [9] [10] Table 2

[Table 53]

NO. Negative active material specific compound initial capacity mAh Initial output power W Output power after cycle W Cycle Retention % Impedance Rct Response resistance Ω Impedance Cdl Double layer capacity ×10^-4F Negative active material layer density g/cm³ Example 1 Carbonaceous matter (A) Lithium difluorophosphate 6021 558 398 82 9.0 1.5 1.36 Example 2 Carbonaceous matter (A) Trimethylsilyl methanesulfonate 6022 545 384 82 9.5 1.4 1.36 Example 3 Carbonaceous matter (A) Hexamethylcyclotrisiloxane 6020 531 375 81 10.8 1.4 1.36 Comparative example 1 Carbonaceous matter (A) - 6099 486 290 78 12.1 1.3 1.36 Example 4 Carbonaceous matter (B) Lithium difluorophosphate 6032 551 350 81 10.4 1.5 1.35 Example 5 Carbonaceous matter (B) Trimethylsilyl methanesulfonate 6021 525 332 79 10.8 1.4 1.35 Example 6 Carbonaceous matter (B) Hexamethylcyclotrisiloxane 6112 524 315 78 10.8 1.4 1.35 Comparative example 2 Carbonaceous matter (B) - 6099 469 275 71 12.3 1.5 1.35 Example 7 Carbonaceous matter (C) Lithium difluorophosphate 5998 570 445 85 16.4 1.2 1.36 Example 8 Carbonaceous matter (C) Trimethylsilyl methanesulfonate 6021 564 423 83 17.8 1.1 1.36 Example 9 Carbonaceous matter (C) Hexamethylcyclotrisiloxane 6070 554 418 82 15.6 1.2 1.36 Comparative example 3 Carbonaceous matter (C) - 5989 507 340 79 19.4 1.1 1.36 Example 10 Carbonaceous matter (D) Lithium difluorophosphate 5991 546 346 77 32.0 0.9 1.33

NO. Negative active material specific compound initial capacity mAh Initial output power W Output power after cycle W Cycle Retention % Impedance Rct Response resistance Ω Impedance Cdl Double layer capacity ×10^-4F Negative active material layer density g/cm³ Example 11 Carbonaceous matter (D) Trimethylsilyl methanesulfonate 5987 557 337 76 41.0 0.8 1.33 Example 12 Carbonaceous matter (D) Hexamethylcyclotrisiloxane 5982 541 335 76 34.2 0.9 1.33 Comparative example 4 Carbonaceous matter (D) - 5889 521 287 73 48.0 0.7 1.33

From the results of the negative electrode [9][10] Table 2, it can be seen that by containing specific compounds such as lithium difluorophosphate, trimethylsilyl methanesulfonate, and hexamethylcyclotrisiloxane in the non-aqueous electrolyte , and by containing a negative electrode active material with a tap density of 0.1 or more and a pore volume of 0.01 mL/g or more in the range of 0.01 μm to 1 μm measured by a mercury porosimeter, even for large batteries, it can be realized High post-cycle output power and high cycle retention rate, so that a lithium secondary battery having both high output power and long life can be provided.

In addition, by including a specific compound in the non-aqueous electrolyte solution and making the reaction resistance of the counter battery of the negative electrode less than 500Ω, even for a large battery, it is possible to achieve a high output after cycle and a high cycle retention rate, Thus both high output power and good life.

Electrolyte solution [1] <Production of secondary battery>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the cloth part is used as the negative electrode.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The battery has a rated discharge capacity of about 6 ampere hours (Ah) and a DC resistance component of about 5 milliohms as measured by the 10 kHz AC method.

[evaluation of the battery]

(Measuring method of initial capacity)

For a new battery that has not undergone charge-discharge cycles, 5 cycles of initial charge-discharge (voltage range 4.1V-3.0V) were performed at 25°C in a voltage range of 4.1V-3.0V. The 0.2C discharge capacity of the 5th cycle at this time (the current value of the 1-hour discharge rated capacity is taken as 1C, and the rated capacity depends on the discharge capacity of the 1-hour-rate (one-hour-rate), the same below) discharge capacity as initial capacity.

(Measurement method of low temperature output power)

In an environment of 25°C, charge with a constant current of 0.2C for 150 minutes, and discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 5.0C for 10 seconds in an environment of -30°C, and measure the 10th second Voltage. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the output power (W).

Electrolyte [1] Example 1

Under a dry argon atmosphere, add lithium hexafluorophosphate (LiPF ₆ ) at 1 mol/L to a mixture of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) (volume ratio 15:85) and dissolve it. Hexamethylcyclotrisiloxane was mixed in an amount of 0.3% by mass to prepare a non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was fabricated according to the above-mentioned method, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 2

Use the non-aqueous electrolyte solution prepared in Example 1 of the electrolyte solution [1] with a volume ratio of EC and EMC of 20:80 to make a battery, and measure the low-temperature output power. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 3

Use the non-aqueous electrolyte solution that the non-aqueous solvent in the embodiment 1 of electrolytic solution [1] is changed into the mixture (volume ratio 15:40:45) of EC, dimethyl carbonate (DMC), EMC and prepare battery, and Determination of low temperature output power. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 4

Using a non-aqueous electrolytic solution prepared by mixing phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Example 1, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 5

Using the non-aqueous electrolytic solution prepared by mixing hexamethyldisiloxane instead of the hexamethylcyclotrisiloxane in the electrolytic solution [1] Example 1, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 6

Using a non-aqueous electrolytic solution prepared by mixing trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Example 1, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 7

Using the non-aqueous electrolytic solution prepared by mixing methyl fluorosulfonate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Example 1, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 8

A battery was produced using a non-aqueous electrolytic solution obtained by mixing lithium nitrate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Example 1 and storing for 3 days, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 9

Use lithium difluorophosphate prepared according to the method described on pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5 (7) to replace the hexamethyl ring in the electrolyte [1] Example 1 The non-aqueous electrolyte prepared by using trisiloxane was used as the non-aqueous electrolyte to make a battery and measure the low-temperature output power. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 10

Electrolyte solution [1] In Example 9, a battery was fabricated using a non-aqueous electrolyte solution obtained by changing the mixing amount of lithium difluorophosphate to an amount of 0.08% by mass relative to a mixed solution of a nonaqueous solvent and lithium hexafluorophosphate, and measured Low temperature output power. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 11

Using the non-aqueous electrolytic solution obtained by mixing lithium acetate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Example 1 and storing it for 3 days, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Example 12

<Production of secondary battery-2>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm by a press, and then cut into a size of 56 mm wide and 850 mm long, as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[Production of electrolyte solution]

The same non-aqueous electrolytic solution as in the electrolytic solution [1] Example 1 was prepared.

[assembling the battery]

The positive electrode and the negative electrode were stacked and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact, and an electrode body was produced. The positive and negative terminals were exposed in the battery can.

Then, 5 mL of an electrolytic solution described later was injected thereinto, followed by riveting molding to manufacture a 18650-type cylindrical battery. The battery has a rated discharge capacity of about 0.7 ampere hours (Ah) and a DC resistance of about 35 milliohms (mΩ) measured by the 10 kHz AC method. In addition, the area ratio of the sum of the electrode areas of the positive electrode to the surface area of the case of the secondary battery was 19.4 times. For the above battery, the low-temperature output was measured in the same manner as in Example 1 of the electrolytic solution [1]. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 1

A battery was fabricated using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 1 of the electrolyte solution [1], and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 2

A battery was produced using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 2 of the electrolyte solution [1], and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 3

A battery was produced using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 3 of the electrolyte solution [1], and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 4

Under a dry argon atmosphere, add lithium hexafluorophosphate (LiPF ₆ ) at 1 mol/L to a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 4:6) and dissolve it, and then add 0.3 mass % of the amount of mixed hexamethylcyclotrisiloxane to prepare a non-aqueous electrolyte.

A battery was produced using this non-aqueous electrolyte solution, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 5

Using a non-aqueous electrolytic solution prepared by mixing phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 6

Using a non-aqueous electrolytic solution prepared by mixing hexamethyldisiloxane instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 7

Using a non-aqueous electrolytic solution prepared by mixing trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 8

Using a nonaqueous electrolytic solution prepared by mixing methyl fluorosulfonate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 9

A battery was manufactured using a non-aqueous electrolytic solution obtained by mixing lithium nitrate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4 and storing for 3 days, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 10

Using a non-aqueous electrolytic solution prepared by mixing lithium difluorophosphate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 11

A battery was produced using a non-aqueous electrolytic solution obtained by mixing lithium acetate instead of hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, and storing for 3 days, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 12

Using the non-aqueous electrolytic solution prepared without mixing hexamethylcyclotrisiloxane in the electrolytic solution [1] Comparative Example 4, a battery was produced, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte [1] Comparative Example 13

Electrolyte solution [1] In Example 12, a battery was fabricated using the same non-aqueous electrolyte solution as in Electrolyte Solution [1] Comparative Example 1, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [1].

Electrolyte[1] Table 1

[Table 54]

Solvent Ratio of EC (volume%) contains compounds Low temperature output power (W) Remark Example 1 EC: EMC 15 Hexamethylcyclotrisiloxane 20.1 Compared with Comparative Example 1, it increased by 26.4% Example 2 EC: EMC 20 Hexamethylcyclotrisiloxane 19.9 Compared with Comparative Example 2, it increased by 25.9% Example 3 EC: DMC: EMC 15 Hexamethylcyclotrisiloxane 20.5 Compared with Comparative Example 3, it increased by 27.3% Example 4 EC: EMC 15 phenyl dimethyl fluorosilane 19.8 Compared with Comparative Example 1, it increased by 24.5% Example 5 EC: EMC 15 Hexamethyldisiloxane 20.2 Compared with Comparative Example 1, it increased by 27.0% Example 6 EC: EMC 15 Trimethylsilyl methanesulfonate 20.4 Compared with Comparative Example 1, it increased by 28.3% Example 7 EC: EMC 15 Methyl fluorosulfonate 19.8 Compared with Comparative Example 1, it increased by 24.5% Example 8 EC: EMC 15 lithium nitrate 20.0 Compared with Comparative Example 1, it increased by 25.8% Example 9 EC: EMC 15 Lithium difluorophosphate (0.3%) 20.8 Compared with Comparative Example 1, it increased by 30.8% Example 10 EC: EMC 15 Lithium difluorophosphate (0.08%) 19.0 Compared with Comparative Example 1, it increased by 19.5% Example 11 EC: EMC 15 Lithium acetate 19.9 Compared with Comparative Example 1, it increased by 25.2% Example 12 EC: EMC 15 Hexamethylcyclotrisiloxane 1.86 Compared with Comparative Example 13, it increased by 20.8% Comparative example 1 EC: EMC 15 none 15.9 Comparative example 2 EC: EMC 20 none 15.8 Comparative example 3 EC: DMC: EMC 15 none 16.1 Comparative example 4 EC: EMC 40 Hexamethylcyclotrisiloxane 17.6 Compared with Comparative Example 12, it increased by 15.0% Comparative Example 5 EC: EMC 40 phenyl dimethyl fluorosilane 17.5 Compared with Comparative Example 12, it increased by 14.4% Comparative example 6 EC: EMC 40 Hexamethyldisiloxane 17.6 Compared with Comparative Example 12, it increased by 15.0% Comparative example 7 EC: EMC 40 Trimethylsilyl methanesulfonate 17.8 Compared with Comparative Example 12, it increased by 16.3% Comparative example 8 EC: EMC 40 Methyl fluorosulfonate 17.5 Compared with Comparative Example 12, it increased by 14.4% Comparative example 9 EC: EMC 40 lithium nitrate 17.7 Compared with Comparative Example 12, it increased by 15.7% Comparative Example 10 EC: EMC 40 Lithium difluorophosphate 17.9 Compared with Comparative Example 12, it increased by 17.0% Comparative example 11 EC: EMC 40 Lithium acetate 17.6 Compared with Comparative Example 12, it increased by 15.0% Comparative example 12 EC: EMC 40 none 15.3 Comparative Example 13 EC: EMC 15 none 1.54

It can be seen from Table 1 of the electrolyte [1] that the lithium secondary batteries of the electrolyte [1] Examples 1 to 11 containing a specific amount of EC and a specific compound in the non-aqueous electrolyte are not only compatible with the lithium secondary batteries containing an excessive amount of EC, but also not Compared with the lithium secondary battery of the electrolyte solution [1] Comparative Example 12 containing the specific compound, and even with the electrolyte solution [1] Comparative Examples 1 to 3 that did not contain the specific compound although the EC amount was within a specific range, and although it contained The electrolytic solution [1] in which the specific compound was excessive in EC had improved low-temperature output characteristics compared with the lithium secondary batteries of Comparative Examples 4 to 11. In addition, the lithium secondary battery of Example 12 in the electrolyte solution [1] containing a specific amount of EC and a specific compound in the non-aqueous electrolyte solution, and the electrolyte solution [1] which does not contain the specific compound although the amount of EC is within a specific range Compared with the lithium secondary battery of Comparative Example 13, the low-temperature output characteristics were improved.

In addition, the effect is not a simple superposition of the two, but the effect is significantly enhanced by satisfying two conditions. Electrolyte solution [1] Table 1 shows the rate of increase in low-temperature output when using a non-aqueous electrolyte solution containing a specific compound (except for the same composition) compared to when using a non-aqueous electrolyte solution that does not contain a specific compound. In the electrolytic solution [1] Examples 1 to 12, this value was larger than that of the electrolytic solution [1] Comparative Examples 4 to 11 in which the amount of EC was excessive, and the effect of the present invention was large.

In addition, the increase rate of the output power of the electrolyte [1] Example 12 relative to the electrolyte [1] Comparative Example 13 was 20.8%, while the electrolyte [1] Example 1 with the same material but a different battery structure was compared to the The output increase rate of the electrolyte solution [1] Comparative Example 1 was 26.4%. It can be seen that the battery structure has a great influence on the effect of the non-aqueous electrolyte solution of the present invention. That is, the effect of the present invention is particularly large for a high-capacity battery or a battery with a small DC resistance.

Furthermore, although it is not described in the table, when an electrolyte solution with an EC content of less than 1% by volume is used, compared with the electrolyte solution [1] Example 1, the initial capacity is slightly lowered, and the output power characteristics or cycle characteristics at room temperature are deteriorated. .

As mentioned above, by using the non-aqueous electrolytic solution of the present invention, that is, a non-aqueous electrolytic solution for secondary batteries having the following characteristics, very large low-temperature output power characteristics can be brought into play. It is characterized by: it is a mixed solvent containing at least ethylene carbonate, the ratio of ethylene carbonate to the total amount of non-aqueous solvents is 1% to 25% by volume, and the non-aqueous electrolytic solution also contains At least one compound, and its content in all non-aqueous electrolytic solutions is 10ppm or more, said substances include: cyclic siloxane compounds represented by general formula (1), fluorosilane compounds represented by general formula (2), Compounds represented by the general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates and propionates.

In addition, compared with the battery structure of the electrolyte solution [1] Example 12, the battery structure of the electrolyte solution [1] Example 1, that is, a battery with a high capacity and a battery with a small DC resistance, can exert this effect more significantly .

Electrolyte solution [2] <Production of secondary battery-1>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm by a press, and then cut into a size of 56 mm wide and 850 mm long, as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[assembling the battery]

The positive electrode and the negative electrode were stacked and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact, and an electrode body was produced. The positive and negative terminals were exposed in the battery can. Then, 5 mL of an electrolytic solution described later was injected thereinto, followed by riveting molding to manufacture a 18650-type cylindrical battery. The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the secondary battery is about 0.7 ampere hours (Ah), and the DC resistance component measured by the 10kHz alternating current method is about 35 milliohms (mΩ ).

[evaluation of the battery]

(initial charge and discharge)

The produced battery was charged to 4.2V at 25°C by a constant current constant voltage charging method of 0.2C, and then discharged to 3.0V by a constant current of 0.2C. This was performed for 5 cycles to stabilize the battery. The discharge capacity at the 5th cycle at this time was taken as the initial capacity. Also, let the current value of the 1-hour discharge rated capacity which depends on the 1-hour-rate discharge capacity be 1C.

(cycle test)

The battery subjected to initial charge and discharge was charged to 4.2V at a constant current and constant voltage of 1C at 60°C, and then discharged to 3.0V at a constant current of 1C for 500 cycles. The ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle at this time was defined as the cycle retention ratio.

(low temperature test)

The battery subjected to the initial charge and discharge was charged to 4.2V by a 0.2C constant current constant voltage charging method at 25°C, and then a 0.2C constant current discharge was performed at -30°C. The discharge capacity at this time was taken as the initial low-temperature capacity, and the ratio of the initial low-temperature capacity to the initial capacity was taken as the initial low-temperature discharge rate.

In addition, the battery after the cycle test was charged to 4.2V at 25°C by a constant current constant voltage charging method of 0.2C, and then discharged to 3.0V by a constant current of 0.2C. Three cycles were performed on it, and the discharge capacity at the third cycle was taken as the capacity after cycle. Then, the same battery was charged to 4.2V at 25°C by a constant current constant voltage charging method of 0.2C, and then discharged at a constant current of 0.2C at -30°C. The discharge capacity at this time was taken as the post-cycle low-temperature capacity, and the ratio of the post-cycle low-temperature capacity to the post-cycle capacity was taken as the post-cycle low-temperature discharge rate.

Electrolyte [2] Example 1

Under a dry argon atmosphere, add lithium hexafluorophosphate (lithium hexafluorophosphate) at 0.9 mol/L to a mixture of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) (volume ratio 2:4:4). LiPF ₆ ) was dissolved, and the mixed solution contained 0.3% by mass of lithium difluorophosphate prepared according to the method described on pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5 (7), to prepare non- water electrolyte. A 18650-type cylindrical battery was manufactured using this non-aqueous electrolyte solution, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2]. Furthermore, when the electrolytic solution was recovered from the battery after the low-temperature capacity measurement after circulation by a centrifuge, and the amount of dimethyl carbonate (DMC) generated in the transesterification reaction was analyzed by gas chromatography (GC), the amount was 0.5% by mass in the electrolyte.

Electrolyte [2] Comparative Example 1

Except not containing lithium difluorophosphate, a 18650-type cylindrical battery was produced in the same manner as in the electrolyte solution [2] Example 1, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2]. Furthermore, when the electrolytic solution was recovered from the battery after the low-temperature capacity measurement after circulation by a centrifuge, and the amount of dimethyl carbonate (DMC) generated in the transesterification reaction was analyzed by gas chromatography (GC), the amount was 9.7% by mass in the electrolyte solution.

Electrolyte [2] Comparative Example 2

Under a dry argon atmosphere, lithium hexafluorophosphate (LiPF ₆ ) was added at 0.9 mol/L to a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 2:8) and dissolved, and the mixture The solution contained 0.3% by mass of lithium difluorophosphate to prepare a non-aqueous electrolytic solution. A 18650-type cylindrical battery was manufactured using this non-aqueous electrolyte solution, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2].

Electrolyte [2] Example 2

Except for using methyl-n-propyl carbonate instead of ethyl methyl carbonate, a 18650-type cylindrical battery was produced in the same manner as in the electrolyte solution [2] Example 1, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2].

Electrolyte [2] Comparative Example 3

Except not containing lithium difluorophosphate, a 18650-type cylindrical battery was produced in the same manner as in the electrolyte solution [2] Example 2, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2].

Electrolyte solution [2] <Production of secondary battery-2>

<Production of positive electrode>

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

<Production of Negative Electrode>

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

<Assembly of battery>

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the secondary battery, is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms ( mΩ).

Electrolyte [2] Example 3

Use the electrolytic solution used in the electrolytic solution [2] Example 1 to make a square battery, and adopt the same method as the electrolytic solution [2] Example 1 to implement the cycle test and low temperature test, and measure the cycle retention rate and low temperature discharge rate. The results are shown in Table 1 of the electrolyte [2].

Electrolyte [2] Comparative Example 4

Using the electrolytic solution used in the electrolytic solution [2] Comparative Example 1, a prismatic battery was produced, a cycle test and a low temperature test were performed, and the cycle retention rate and low temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2].

Electrolyte [2] Comparative Example 5

Using the electrolytic solution used in the electrolytic solution [2] Comparative Example 2, a prismatic battery was produced, a cycle test and a low temperature test were performed, and the cycle retention rate and low temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [2].

Electrolyte [2] Table 1

[Table 55]

No. Battery Circulation retention rate (%) Initial low temperature discharge rate (%) Low temperature after cycle Discharge rate (%) Example 1 Cylinder 64 68 64 Comparative example 1 Cylinder 58 59 50 Comparative example 2 Cylinder 60 60 50 Example 2 Cylinder 63 65 63 Comparative example 3 Cylinder 55 57 45 Example 3 square 73 74 71 Comparative example 4 square 68 62 53 Comparative Example 5 square 68 63 59

From the electrolyte [2] Table 1, it can be seen that if each cylindrical battery (electrolyte [2] embodiment 1, 2, electrolyte [2] comparative example 1-3), square battery (electrolyte [2] Example 3, electrolytic solution [2] comparative example 4,5) compare, then contain the lithium secondary battery of the electrolytic solution [2] embodiment of asymmetric chain carbonate and difluorophosphate in the non-aqueous electrolytic solution simultaneously, Compared with the lithium secondary battery of the comparative example of the electrolytic solution [2] not containing any of these, both the cycle retention rate and the low-temperature discharge rate were improved.

As mentioned above, the rated discharge capacity of the cylindrical batteries of this embodiment and this comparative example is less than 3 ampere hours (Ah), and the DC resistance component is greater than 10 milliohms (mΩ). On the other hand, the prismatic batteries of this example and this comparative example have a rated discharge capacity of 3 ampere hours (Ah) or more, and a DC resistance component of 10 milliohms (mΩ) or less. That is, the prismatic batteries of this example and this comparative example have lower resistance and higher capacitance than cylindrical batteries. Moreover, compared with the improvement degree of the low-temperature characteristics of the electrolyte [2] Example 1 relative to the electrolyte [2] Comparative Example 1, the low-temperature characteristics of the electrolyte [2] Example 3 relative to the electrolyte [2] Comparative Example 4 The degree of improvement is large, and the effect of the present invention is greater in a secondary battery with a large capacity or a secondary battery with a small DC resistance.

Electrolyte solution [3] <Manufacture of secondary battery-1>

[production of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[production of negative electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm).

Then, 20 mL of the non-aqueous electrolytes of the following electrolyte solution [3] example and electrolyte solution [3] comparative example were injected into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of the battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms (mΩ). In addition, the area ratio of the sum of the electrode areas of the positive electrode to the surface area of the case of the secondary battery was 20.65 times.

[evaluation of the battery]

(capacity measurement)

For a new battery that has not been charged and discharged, 5 cycles of initial charge and discharge (voltage range 4.1V to 3.0V) were performed at 25°C in a voltage range of 4.1V to 3.0V. The 0.2C discharge capacity of the 5th cycle at this time (the current value of the 1-hour discharge rated capacity is taken as 1C, and the rated capacity depends on the discharge capacity of the 1-hour-rate (one-hour-rate), the same below) discharge capacity as initial capacity.

(Output power measurement)

Charge at a constant current of 0.2C for 150 minutes at 25°C, discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 5.0C for 10 seconds at -30°C, and measure the voltage at the 10th second. The area of the triangle surrounded by the current-voltage straight line and the lower limit voltage (3V) is taken as the output power (W).

Electrolyte [3] Embodiment 1

Under a dry argon atmosphere, lithium hexafluorophosphate (LiPF ₆ ) and dissolving, and then mixing hexamethylcyclotrisiloxane in an amount of 0.3% by mass in the mixed solution to prepare a nonaqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the method described above, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 2

The non-aqueous electrolyte solution prepared by using an equal amount of ethyl acetate (EA) instead of methyl propionate in Example 1 of the electrolyte solution [3] was used to make a battery, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Example 3

The non-aqueous electrolytic solution prepared by using an equal amount of methyl acetate (MA) instead of methyl propionate in Example 1 of the electrolytic solution [3] was used to make a battery, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Example 4

Under a dry argon atmosphere, a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), methyl propionate (MP) and methyl acetate (MA) (volume ratio 30:60:5:5) Lithium hexafluorophosphate (LiPF ₆ ) was added and dissolved at 1 mol/L, and then 0.3% by mass of hexamethylcyclotrisiloxane was mixed in the mixed solution to prepare a non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the method described above, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 5

Using the electrolyte solution [3] in Example 1, the volume ratio of the mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and methyl propionate (MP) was changed to 3:4:3. Water electrolyte, according to the above method to make the battery, and measure the low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 6

Under a dry argon atmosphere, lithium hexafluorophosphate (LiPF ₆ ) was added at 1 mol/L to a mixture of ethylene carbonate (EC) and methyl propionate (MP) (volume ratio 3:7) and dissolved, and then mixed Hexamethylcyclotrisiloxane was mixed in an amount of 0.3% by mass in the solution to prepare a non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the method described above, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 7

The non-aqueous electrolytic solution obtained by mixing an equal amount of phenyldimethylfluorosilane instead of the hexamethylcyclotrisiloxane in Example 1 of the electrolytic solution [3] is used as the non-aqueous electrolytic solution to make a battery, and measure Low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 8

Use the hexamethylcyclotrisiloxane of mixing equal amount to replace the hexamethylcyclotrisiloxane in the electrolyte [3] embodiment 1 and obtain the non-aqueous electrolytic solution as the non-aqueous electrolytic solution to make the battery, and Determination of low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 9

Use the non-aqueous electrolytic solution obtained by mixing an equal amount of trimethylsilyl methanesulfonate to replace the hexamethylcyclotrisiloxane in the electrolytic solution [3] Example 1 as the non-aqueous electrolytic solution to make a battery , and determine the low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Embodiment 10

Use the non-aqueous electrolytic solution obtained by mixing an equal amount of methyl fluorosulfonate instead of hexamethylcyclotrisiloxane in the electrolytic solution [3] Example 1 as the non-aqueous electrolytic solution to make a battery, and measure the low-temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Example 11

Use the same amount of lithium nitrate to replace the hexamethylcyclotrisiloxane in the electrolyte [3] embodiment 1, and store the non-aqueous electrolyte obtained for 3 days as the non-aqueous electrolyte to make a battery, and measure Low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Example 12

Prepared according to the method described in Inorganic Nuclear Chemistry Letters (1969), 5(7), pages 581 to 582, by mixing equal amounts (0.3% by mass relative to a mixed solution of a non-aqueous solvent and lithium hexafluorophosphate) Lithium difluorophosphate is used to replace the hexamethylcyclotrisiloxane in the electrolyte solution [3] and the non-aqueous electrolyte solution prepared in Example 1 is used as the non-aqueous electrolyte solution to make a battery and measure the low-temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Example 13

Using the non-aqueous electrolytic solution prepared by changing the mixed amount of lithium difluorophosphate in Example 12 to 0.08% by mass relative to the mixed solution of the non-aqueous solvent and lithium hexafluorophosphate, a battery was produced, and the low-temperature Output Power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Example 14

<Production of secondary battery-2>

<Production of positive electrode>

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

<Production of Negative Electrode>

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm by a press, and then cut into a size of 56 mm wide and 850 mm long, as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[Preparation of Electrolyte Solution]

Prepare the same non-aqueous electrolytic solution as in Example 1 of the electrolytic solution [3].

[assembling the battery]

The positive electrode and the negative electrode were overlapped and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact to form an electrode body. The positive and negative terminals are housed in the battery can with the terminals exposed to the outside. Then, 5 mL of an electrolytic solution described later was injected thereinto, followed by riveting molding to manufacture a 18650-type cylindrical battery. The rated discharge capacity of the battery is about 0.7 Ah, and the DC resistance measured by the 10 kHz AC method is about 35 milliohms (mΩ). In addition, the area ratio of the sum of the electrode areas of the positive electrode to the surface area of the case of the secondary battery was 19.4 times. In the above battery, the low-temperature output was measured in the same manner as in Example 1 of the electrolytic solution [3]. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 1

Using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 1 of the electrolyte solution [3], a battery was fabricated by the above method, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 2

Using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 2 of the electrolyte solution [3], a battery was fabricated by the above method, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 3

Using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 3 of the electrolyte solution [3], a battery was fabricated by the above method, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 4

Using the non-aqueous electrolytic solution prepared without mixing hexamethylcyclotrisiloxane in the electrolytic solution [3] Example 4, a battery was fabricated by the above method, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 5

Using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 5 of the electrolyte solution [3], a battery was fabricated by the above-mentioned method, and the low-temperature output power was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 6

Under a dry argon atmosphere, lithium hexafluorophosphate (LiPF ₆ ) was added at 1 mol/L to a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7) and dissolved to prepare a non-aqueous electrolyte. Using this non-aqueous electrolytic solution, a battery was produced by the method described above, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 7

In a dry argon atmosphere, lithium hexafluorophosphate (LiPF ₆ ) was added at 1 mol/L to a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3:7) to dissolve it, and then mixed 0.3% by mass in the mixed solution amount of hexamethylcyclotrisiloxane to prepare a non-aqueous electrolyte. Using this non-aqueous electrolytic solution, a battery was produced by the method described above, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 8

Use the non-aqueous electrolyte obtained by mixing an equal amount of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in the electrolyte [3] Comparative Example 7 as the non-aqueous electrolyte, and make the battery by the above method , and determine the low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 9

The non-aqueous electrolytic solution obtained by mixing an equal amount of hexamethylcyclotrisiloxane instead of the hexamethylcyclotrisiloxane in the electrolyte [3] Comparative Example 7 was made by the above-mentioned method battery, and determine the low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 10

The non-aqueous electrolytic solution obtained by mixing an equal amount of trimethylsilyl methanesulfonate to replace the hexamethylcyclotrisiloxane in the electrolytic solution [3] Comparative Example 7 is used as the non-aqueous electrolytic solution. Methods The battery was fabricated and the output power at low temperature was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 11

Use the non-aqueous electrolytic solution obtained as non-aqueous electrolytic solution to replace the hexamethylcyclotrisiloxane in electrolytic solution [3] comparative example 7 with the same amount of fluorosulfonic acid methyl ester, make battery with the above-mentioned method, and Determination of low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 12

Use the same amount of lithium nitrate to replace the hexamethylcyclotrisiloxane in the electrolyte [3] Comparative Example 7, and store the non-aqueous electrolyte obtained for 3 days as the non-aqueous electrolyte, and make the battery by the above method , and determine the low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 13

Use the non-aqueous electrolyte obtained by mixing an equal amount of lithium difluorophosphate instead of hexamethylcyclotrisiloxane in Comparative Example 7 of the electrolyte [3] as the non-aqueous electrolyte, make a battery by the above method, and measure Low temperature output power. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Comparative Example 14

Electrolyte solution [3] In Example 14, using the non-aqueous electrolyte solution prepared in the same manner as electrolyte solution [3] Comparative Example 1, a battery was produced by the above-mentioned method, and the low-temperature output was measured. The results are shown in Table 1 of the electrolyte [3].

Electrolyte [3] Table 1

[Table 56]

No. Non-aqueous solvent Specific compound (mass%) Low temperature output power (W) Example 1 EC:EMC:MP Hexamethylcyclotrisiloxane (0.3%) 20.3 Example 2 EC:EMC:EA Hexamethylcyclotrisiloxane (0.3%) 20.5 Example 3 EC:EMC:MA Hexamethylcyclotrisiloxane (0.3%) 20.6 Example 4 EC:EMC:MA:MP Hexamethylcyclotrisiloxane (0.3%) 20.5 Example 5 EC:EMC:MP Hexamethylcyclotrisiloxane (0.3%) 20.0 Example 6 EC:MP Hexamethylcyclotrisiloxane (0.3%) 19.1 Example 7 EC:EMC:MP phenyldimethylfluorosilane (0.3%) 20.0 Example 8 EC:EMC:MP Hexamethyldisiloxane (0.3%) 20.5 Example 9 EC:EMC:MP Trimethylsilyl methanesulfonate (0.3%) 20.6 Example 10 EC:EMC:MP Methyl fluorosulfonate (0.3%) 20.0 Example 11 EC:EMC:MP Lithium nitrate (0.3%) 20.2 Example 12 EC:EMC:MP Lithium difluorophosphate (0.3%) 21.2 Example 13 EC:EMC:MP Lithium difluorophosphate (0.08%) 19.0 Example 14 EC:EMC:MP Hexamethylcyclotrisiloxane (0.3%) 1.84 Comparative example 1 EC:EMC:MP none 15.7 Comparative example 2 EC:EMC:EA none 15.8 Comparative example 3 EC:EMC:MA none 16.1 Comparative example 4 EC:EMC:MA:MP none 16.0 Comparative Example 5 EC:MP none 15.7 Comparative example 6 EC: EMC none 15.5 Comparative example 7 EC: EMC Hexamethylcyclotrisiloxane (0.3%) 18.3 Comparative example 8 EC: EMC phenyldimethylfluorosilane (0.3%) 18.0 Comparative example 9 EC: EMC Hexamethyldisiloxane (0.3%) 18.4 Comparative Example 10 EC: EMC Trimethylsilyl methanesulfonate (0.3%) 18.5 Comparative Example 11 EC: EMC Methyl fluorosulfonate (0.3%) 18.1 Comparative example 12 EC: EMC Lithium nitrate (0.3%) 18.4 Comparative Example 13 EC: EMC Lithium difluorophosphate (0.3%) 18.6 Comparative Example 14 EC:EMC:MP none 1.52

It can be seen from Table 1 of the electrolyte solution [3] that the lithium secondary batteries of the electrolyte solution [3] Examples 1 to 13 containing chain carboxylic acid esters and specific compounds in the non-aqueous electrolyte solution are not only compatible with those that do not contain any of them. Compared with the lithium secondary battery of the electrolyte [3] comparative example 6, and even compared with the electrolyte [3] comparative examples 1 to 5 that do not contain a specific compound, and the electrolyte [3] that does not contain a chain carboxylate Compared with the lithium secondary batteries of Examples 7 to 13, the low-temperature output characteristics were also improved. In addition, the effect is not a simple superposition of the two, but the effect is significantly enhanced by using both.

In addition, the increase rate of the output power of the electrolyte [3] Example 14 relative to the electrolyte [3] Comparative Example 14 is about 21%, while using the same material and different battery structures Liquid [3] The output power increase rate of Comparative Example 1 is about 29%. It can be seen that the battery structure has an influence on the effect of the non-aqueous electrolyte of the present invention.

As mentioned above, by using the non-aqueous electrolytic solution of the present invention, that is, a non-aqueous electrolytic solution for secondary batteries having the following characteristics, very large low-temperature output power characteristics can be brought into play. It is characterized by: containing at least one chain carboxylate, and at least one compound selected from the following substances, and its content in all non-aqueous electrolytes is more than 10ppm. The substances include: general formula Cyclic siloxane compounds represented by (1), fluorosilane compounds represented by general formula (2), compounds represented by general formula (3), compounds having an S-F bond in the molecule, nitrates, nitrites, monofluorophosphoric acid salt, difluorophosphate, acetate and propionate.

Electrolyte solution [4] <Production of secondary battery-1 (production of square battery)>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

2kg of artificial graphite powder KS-44 (manufactured by timcal company, trade name) and 1kg of petroleum pitch were mixed, and the obtained slurry mixture was heated up to 1100° C. for 2 hours in a batch heating furnace under an inert atmosphere. Keep at temperature for 2 hours.

This was pulverized, and the particle size was adjusted to 18 to 22 μm with a vibrating sieve to finally obtain an "amorphous-coated graphite-like carbonaceous material" in which the graphite surface was covered with 7% by mass of amorphous carbon. Using this "amorphous coated graphite-like carbonaceous material" as the negative active material, adding 100 parts by weight of sodium carboxymethylcellulose as a thickener to 98 parts by weight of the "amorphous coated graphite-based carbonaceous material" Aqueous dispersion (the concentration of sodium carboxymethylcellulose is 1% by mass), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50 mass %) %), mixed with a disperser to make a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated portions of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm) with a discharge valve. Then, 20 mL of a non-aqueous electrolytic solution described later was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and sealed to produce a square battery. The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the battery is about 6Ah, and the DC resistance component measured by the 10kHz AC method is about 5 milliohms.

"Battery Evaluation"

(capacity measurement)

For a battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 hour Rate (one-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity.

(Output power measurement)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the output power (W).

Electrolyte [4] Embodiment 1

Under a dry argon atmosphere, to a mixture (capacity 0.3 mol/L of LiPF ₆ and 0.7 mol/L of LiBF ₄ were added in a ratio of 2:7:1) and dissolved so that the mixed solution contained 1% by mass of vinylene carbonate, 0.3% by mass of hexamethanone Based cyclotrisiloxane, preparation of non-aqueous electrolyte. The flash point of this non-aqueous electrolytic solution was 61°C. Using this non-aqueous electrolytic solution, a rectangular battery was produced by the method described above, and the output was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte [4] Embodiment 2

Except for using phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane to prepare a nonaqueous electrolytic solution, a square battery was produced in the same manner as in Example 1 of the electrolytic solution [4], and the output power was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte [4] Example 3

Except using methyl fluorosulfonate instead of hexamethylcyclotrisiloxane to prepare a non-aqueous electrolytic solution, a square battery was produced in the same manner as in Example 1 of the electrolytic solution [4], and the output power was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte [4] Embodiment 4

In addition to using lithium difluorophosphate prepared according to the method described on pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5(7) to replace hexamethylcyclotrisiloxane to make a non-aqueous electrolyte , A square battery was produced in the same manner as in Example 1 of the electrolyte solution [4], and the output power was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte [4] Comparative Example 1

Except that the non-aqueous electrolyte solution did not contain hexamethylcyclotrisiloxane, a square battery was produced in the same manner as in the electrolyte solution [4] Example 1, and the output was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte solution [4] <Manufacture of secondary battery-2 (manufacture of cylindrical battery)>

[production of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[production of negative electrode]

2kg of artificial graphite powder KS-44 (manufactured by timcal company, trade name) and 1kg of petroleum pitch were mixed, and the obtained slurry mixture was heated up to 1100° C. for 2 hours in a batch heating furnace under an inert atmosphere. Keep at temperature for 2 hours.

This was pulverized, and the particle size was adjusted to 18 to 22 μm with a vibrating sieve to finally obtain an "amorphous-coated graphite-like carbonaceous material" in which the graphite surface was covered with 7% by mass of amorphous carbon. Using this "amorphous coated graphite-like carbonaceous material" as the negative active material, adding 100 parts by weight of sodium carboxymethylcellulose as a thickener to 98 parts by weight of the "amorphous coated graphite-based carbonaceous material" Aqueous dispersion (the concentration of sodium carboxymethylcellulose is 1% by mass), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50 mass %) %), mixed with a disperser to make a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 18 μm as a negative electrode current collector, dried, rolled to a thickness of 85 μm with a press, and then cut into a size of 56 mm in width and 850 mm in length as the negative electrode. Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[assembling the battery]

The positive electrode and the negative electrode were overlapped and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact to form an electrode body. The positive and negative terminals are housed in the battery can with the terminals exposed to the outside. Then, 5 mL of a non-aqueous electrolytic solution described later was injected thereinto, and then caulking was performed to manufacture a 18650-type cylindrical battery. The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the battery is about 0.7 ampere hours (Ah), and the DC resistance component measured by the 10kHz alternating current method is about 35 milliohms (mΩ ).

Electrolyte [4] Embodiment 5

The non-aqueous electrolytic solution used in the electrolytic solution [4] Example 1 was used as the non-aqueous electrolytic solution to manufacture a cylindrical battery, and the output power was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte [4] Comparative Example 2

Except for using the non-aqueous electrolyte solution used in the electrolyte solution [4] Comparative Example 1 as the non-aqueous electrolyte solution, a cylindrical battery was produced in the same manner as in the electrolyte solution [4] Example 5, and the output was measured. The results are shown in Table 1 of the electrolyte [4].

Electrolyte [4] Table 1

[Table 57]

No. specific compound Output power (W) Example 1 Hexamethylcyclotrisiloxane 500 Example 2 phenyl dimethyl fluorosilane 510 Example 3 Methyl fluorosulfonate 510 Example 4 Lithium difluorophosphate 525 Example 5 Hexamethylcyclotrisiloxane 45 Comparative example 1 --- 390 Comparative example 2 --- 37

From the electrolyte [4] Table 1, it can be seen that if each square battery (electrolyte [4] embodiment 1 to 4, electrolyte [4] comparative example 1), cylindrical battery (electrolyte [4] embodiment 5 , Electrolyte solution [4] Comparative Example 2) for comparison, it can be seen that the output power of the lithium secondary battery of this embodiment is improved.

As described above, the rated discharge capacity of the prismatic batteries of this example and this comparative example is 3 ampere hours (Ah) or more, and the DC resistance component is 10 milliohms (mΩ) or less. On the other hand, the rated discharge capacity of the cylindrical batteries of this embodiment and this comparative example is less than 3 ampere hours (Ah), and the DC resistance component is greater than 10 milliohms (mΩ). That is, the prismatic batteries of this example and this comparative example have lower resistance and higher capacitance than cylindrical batteries. Moreover, the output power improvement degree of the electrolyte solution [4] Example 1 relative to the electrolyte solution [4] Comparative Example 1 is higher than the output power improvement degree of the electrolyte solution [4] Example 5 relative to the electrolyte solution [4] Comparative Example 2 Large, the effect of the present invention is greater in a secondary battery with a large capacitance or a secondary battery with a small DC resistance.

Electrolyte [5] <Production of secondary battery>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated portions of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm) with a discharge valve. Then, 20 mL of a non-aqueous electrolytic solution described later was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and sealed to produce a square battery. The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the battery is about 6Ah, and the DC resistance component measured by the 10kHz AC method is about 5 milliohms (mΩ).

[evaluation of the battery]

(capacity measurement)

For a battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 hour Rate (one-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity.

(Output power measurement)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the output power (W).

(cycle test)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the practical upper limit temperature of the lithium secondary battery. After charging to the charging upper limit voltage of 4.2V by the constant current and constant voltage method of 2C, discharge to the end-of-discharge voltage of 3.0V by the constant current of 2C. This charge-discharge cycle is regarded as one cycle, and the cycle is repeated until 500 times.

(preservation test)

The storage test was carried out in a high-temperature environment of 60°C. The battery previously charged to a charging upper limit voltage of 4.2 V by a constant current constant voltage method in an environment of 25° C. was stored at 60° C. for one month.

The output power of the battery after the capacity measurement, the battery after the cycle test, and the battery after the storage test is measured, and they are respectively used as the initial output power, the output power after cycle, and the output power after storage.

Electrolyte [5] Embodiment 1

Under dry argon atmosphere, add 1 mol/L LiPF ₆ and 0.01 mol/L of LiN(CF ₃ SO ₂ ) ₂ was dissolved, and the mixed solution contained 0.3% by mass of hexamethylcyclotrisiloxane to prepare a non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the above-mentioned method, and the initial output power, the output power after cycling, and the output power after storage were measured. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 2

Except using phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane to make a non-aqueous electrolyte, a battery was made in the same manner as in Example 1 of the electrolyte [5], and the initial output power and output after cycling were measured. Power and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Example 3

Except using methyl fluorosulfonate to replace hexamethylcyclotrisiloxane to make non-aqueous electrolyte, make battery in the same way as electrolyte [5] embodiment 1, and measure initial output power, output power after cycle and Output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 4

In addition to using lithium difluorophosphate prepared according to the method described on pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5(7) to replace hexamethylcyclotrisiloxane to make a non-aqueous electrolyte , The battery was produced in the same manner as the electrolyte solution [5] Example 1, and the initial output power, output power after cycle and output power after storage were measured. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 5

Except for using bis(oxalato)lithium borate (LiBOB) instead of LiN(CF ₃ SO ₂ ) ₂ to make a non-aqueous electrolyte, a battery was produced in the same manner as in Example 1 of the electrolyte [5], and the initial output power was measured , output power after cycling and output power after storage. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 6

Except for using bis(oxalato)lithium borate (LiBOB) instead of LiN(CF ₃ SO ₂ ) ₂ to make a non-aqueous electrolyte, a battery was produced in the same manner as in Example 4 of the electrolyte [5], and the initial output power was measured , output power after cycling and output power after storage. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Comparative Example 1

A battery was produced in the same manner as in Example 1 except that LiN(CF ₃ SO ₂ ) ₂ was not dissolved in the non-aqueous electrolyte solution, and the initial output, output after cycles, and output after storage were measured. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Comparative Example 2

Except not containing hexamethylcyclotrisiloxane in the nonaqueous electrolytic solution, a battery was produced in the same manner as in the electrolytic solution [5] Example 1, and the initial output power, output power after cycle, and output power after storage were measured. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Comparative Example 3

Except that LiN(CF ₃ SO ₂ ) ₂ and hexamethylcyclotrisiloxane were not contained in the non-aqueous electrolyte solution, a battery was produced in the same manner as in Example 1 of the electrolyte solution [5], and the initial output power and output after cycling were measured. Power and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 7

<Manufacture of secondary battery-2>

[production of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[production of negative electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm by a press, and then cut into a size of 56 mm wide and 850 mm long, as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[assembling the battery]

The positive electrode and the negative electrode were overlapped and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact to form an electrode body. The positive and negative terminals are housed in the battery can with the terminals exposed to the outside. Then, 5 mL of a non-aqueous electrolytic solution described later was injected thereinto, and then caulking was performed to manufacture a 18650-type cylindrical battery. One battery of a secondary battery has the capacitance of the battery element contained in the exterior, that is, the rated discharge capacity of the secondary battery is about 0.7 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 35 milliohms (mΩ). .

The non-aqueous electrolytic solution used in the electrolytic solution [5] Example 1 was used as the non-aqueous electrolytic solution to manufacture a cylindrical battery, and the initial output power, output power after cycle and output power after storage were measured. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 8

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Example 2 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after cycling were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 9

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Example 3 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after the cycle were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 10

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Example 4 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after the cycle were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Embodiment 11

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Example 5 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after the cycle were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Example 12

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Example 6 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after the cycle were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Comparative Example 4

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Comparative Example 1 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after cycling were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Comparative Example 5

Except using the non-aqueous electrolyte solution used in the electrolyte solution [5] Comparative Example 2 as the non-aqueous electrolyte solution, a cylindrical battery was produced in the same manner as the electrolyte solution [5] Example 7, and the initial output power and the output power after cycling were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Comparative Example 6

Except using the non-aqueous electrolytic solution used in the electrolytic solution [5] Comparative Example 3 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [5] Example 7, and the initial output power and the output power after cycling were measured. and output power after saving. The results are shown in Table 1 of the electrolyte [5].

Electrolyte [5] Table 1

[Table 58]

No. specific lithium salts specific compound Initial output power (W) Output power after cycle (W) Output power after saving (W) Example 1 LiN(CF₃SO₂)₂ Hexamethyltrisiloxane 535 350 410 Example 2 LiN(CF₃SO₂)₂ phenyl dimethyl fluorosilane 520 320 405 Example 3 LiN(CF₃SO₂)₂ Methyl fluorosulfonate 515 330 400 Example 4 LiN(CF₃SO₂)₂ Lithium difluorophosphate 545 360 435 Example 5 LiBOB Hexamethyltrisiloxane 515 325 400 Example 6 LiBOB Lithium difluorophosphate 520 355 420 Comparative example 1 - Hexamethyltrisiloxane 500 285 345 Comparative example 2 LiN(CF₃SO₂)₂ - 450 240 340 Comparative example 3 - - 440 225 330 Example 7 LiN(CF₃SO₂)₂ Hexamethyltrisiloxane 48 29 35 Example 8 LiN(CF₃SO₂)₂ phenyl dimethyl fluorosilane 47 28 34 Example 9 LiN(CF₃SO₂)₂ Methyl fluorosulfonate 47 28 34 Example 10 LiN(CF₃SO₂)₂ Lithium difluorophosphate 49 31 36 Example 11 LiBOB Hexamethyltrisiloxane 48 29 33 Example 12 LiBOB Lithium difluorophosphate 48 31 34 Comparative example 4 - Hexamethyltrisiloxane 45 25 32 Comparative Example 5 LiN(CF₃SO₂)₂ - 41 twenty three 30 Comparative example 6 - - 40 twenty one 29

From the electrolyte [5] Table 1, it can be seen that if each square battery (electrolyte [5] embodiment 1-6, electrolyte [5] comparative example 1-3), cylindrical battery (electrolyte [5] Examples 7-12, electrolyte [5] Comparative Examples 4-6) are compared, then it can be seen that LiN(C _n F _2n+1 SO ₂ ) ₂ (where n is 1-4) is contained in the non-aqueous electrolyte Integer of ) and/or lithium bis(oxalato)borate and the electrolyte solution [5] of the specific compound The lithium secondary battery of the example, and the lithium secondary battery of the comparative example of the electrolyte solution [5] not containing any of these The output power is improved compared to the secondary battery.

As described above, the rated discharge capacity of the prismatic batteries of this example and this comparative example is 3 ampere hours (Ah) or more, and the DC resistance component is 10 milliohms (mΩ) or less. On the other hand, the rated discharge capacity of the cylindrical batteries of this embodiment and this comparative example is less than 3 ampere hours (Ah), and the DC resistance component is greater than 10 milliohms (mΩ). That is, the prismatic batteries of this example and this comparative example have lower resistance and higher capacitance than cylindrical batteries. Moreover, the output power improvement degree of the electrolyte solution [5] Example 1 relative to the electrolyte solution [5] Comparative Example 1 is higher than the output power improvement degree of the electrolyte solution [5] Embodiment 7 relative to the electrolyte solution [5] Comparative Example 4 big. In particular, there is a large difference in the degree of output power increase after cycling and the degree of output power increase after storage. From this, it can be seen that the effect of the present invention is greater in a secondary battery with a large capacity or a secondary battery with a small DC resistance.

Electrolyte solution [6] <Preparation of non-aqueous solvent>

Commercially available ethylene carbonate (EC) was subjected to adsorption treatment (50° C., LHSV, 1/hour) with molecular sieve 4A. On the other hand, after fully rectifying dimethyl carbonate and ethyl methyl carbonate with a reflux ratio of 1 and a theoretical plate number of 30 plates, adsorption treatment was carried out with molecular sieve 4A (25° C., LHSV, 1/hour). Then, they were mixed with EC:DMC:EMC (volume ratio 3:3:4), and further subjected to adsorption treatment (25° C., LHSV, 1/hour) with molecular sieve 4A to prepare a mixed non-aqueous solvent. At this time, no water or alcohols were detected in the non-aqueous solvent.

Electrolyte [6] <Production of secondary battery>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm) with a vent valve. Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery. The rated discharge capacity of this battery is a high capacity of about 6Ah, and the DC resistance component measured by the 10kHz AC method is about 5 milliohms.

[evaluation of the battery]

(capacity measurement)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity.

(Output power measurement)

In an environment of 25°C, charge was performed for 150 minutes with a constant current of 0.2C, and discharge was performed at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, respectively, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the output power (W).

(cycle test)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the upper limit temperature for practical use of lithium secondary batteries. After charging to the charging upper limit voltage of 4.2V by the constant current and constant voltage method of 2C, discharge to the end-of-discharge voltage of 3.0V by the constant current of 2C. This charge-discharge cycle is regarded as one cycle, and the cycle is repeated until 500 times. For the battery after the cycle test, charge and discharge for 3 cycles at 25°C, the 0.2C discharge capacity of the third cycle is taken as the post-cycle capacity, and the ratio of the post-cycle capacity to the initial capacity is taken as the capacity retention rate.

Electrolyte [6] Embodiment 1

In a dry argon atmosphere, 10 ppm of methanol was mixed into the mixed non-aqueous solvent, and lithium hexafluorophosphate (LiPF ₆ ) was added and dissolved at 0.8 mol/L. The amount of hydrogen fluoride (HF) in the solution after 1 day was 12 ppm, and when measured again 2 weeks later, it was 14 ppm. Hexamethylcyclotrisiloxane was mixed in an amount of 0.3% by mass in this mixed solution (2 weeks after mixing) to prepare a non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the method described above, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Embodiment 2

Except that in the electrolytic solution [6] Example 1, the mixing amount of methanol was changed to an amount of 20 ppm relative to the mixed non-aqueous solvent, a non-aqueous electrolytic solution was prepared in the same manner as the electrolytic solution [6] Example 1, and the non-aqueous electrolytic solution was used. The water electrolyte was used to make batteries, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the mixed solution one day after mixing LiPF ₆ was 16 ppm, and it was 19 ppm when measured again two weeks later.

Electrolyte [6] Embodiment 3

Except that in the electrolytic solution [6] Example 1, the mixing amount of methanol was changed to an amount of 35 ppm relative to the mixed non-aqueous solvent, a non-aqueous electrolytic solution was prepared in the same manner as the electrolytic solution [6] Example 1, and the non-aqueous electrolytic solution was used. The water electrolyte was used to make batteries, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the mixed solution one day after mixing LiPF ₆ was 22 ppm, and it was 27 ppm when measured again two weeks later.

Electrolyte [6] Embodiment 4

Except in electrolytic solution [6] embodiment 1, the ethylene glycol (EG) of mixing 15ppm amount with respect to mixed nonaqueous solvent replaces methanol, prepare nonaqueous electrolytic solution in the same way as electrolytic solution [6] embodiment 1, use The non-aqueous electrolytic solution was used to manufacture a battery, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the mixed solution one day after mixing LiPF ₆ was 14 ppm, and it was 16 ppm when measured again two weeks later.

Electrolyte [6] Embodiment 5

Except in electrolyte solution [6] embodiment 1, mix the ethylene glycol of 35ppm amount with respect to mixed nonaqueous solvent to replace methanol, prepare nonaqueous electrolyte solution in the same way as electrolyte solution [6] embodiment 1, use this nonaqueous The electrolyte was used to manufacture batteries, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the mixed solution one day after mixing LiPF ₆ was 23 ppm, and it was 27 ppm when measured again two weeks later.

Electrolyte [6] Embodiment 6

Except mixing 25ppm methanol and 25ppm ethylene glycol with respect to the mixed nonaqueous solvent in the electrolyte solution [6] Example 1, prepare the nonaqueous electrolyte solution in the same manner as the electrolyte solution [6] Example 1, and use the nonaqueous electrolyte solution Batteries were manufactured, and output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the mixed solution 1 day after mixing LiPF ₆ was 31 ppm, and it was 36 ppm when measured again 2 weeks later.

Electrolyte [6] Embodiment 7

In addition to mixing lithium difluorophosphate in an amount of 0.3% by mass with respect to the mixed solution in Example 1 of the electrolyte [6] (according to Inorganic Nuclear Chemistry Letters (1969), 5(7) 581-582 Prepared by the method) to replace hexamethylcyclotrisiloxane, prepare the non-aqueous electrolyte in the same manner as the electrolyte [6] Example 1, use the non-aqueous electrolyte to make a battery, and measure the output power and capacity retention Certainly. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Embodiment 8

Prepared in the same manner as in Electrolytic Solution [6] Example 3, except that lithium difluorophosphate was mixed in an amount of 0.3% by mass with respect to the mixed solution in Electrolytic Solution [6] Example 3 instead of hexamethylcyclotrisiloxane A non-aqueous electrolytic solution, using the non-aqueous electrolytic solution to manufacture a battery, and measuring output power and capacity retention. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Embodiment 9

Prepared in the same manner as in Electrolytic Solution [6] Example 4, except that lithium difluorophosphate was mixed in an amount of 0.3% by mass with respect to the mixed solution instead of hexamethylcyclotrisiloxane in Electrolytic Solution [6] Example 4 A non-aqueous electrolytic solution, using the non-aqueous electrolytic solution to manufacture a battery, and measuring output power and capacity retention. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Embodiment 10

Prepared in the same manner as in Electrolytic Solution [6] Example 6, except that lithium difluorophosphate was mixed in an amount of 0.3% by mass with respect to the mixed solution in the Electrolytic Solution [6] Example 6 instead of hexamethylcyclotrisiloxane A non-aqueous electrolytic solution, using the non-aqueous electrolytic solution to manufacture a battery, and measuring output power and capacity retention. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Embodiment 11

In addition to mixing trimethylsilyl methanesulfonate in an amount of 0.3% by mass with respect to the mixed solution in the electrolyte [6] Example 6 instead of hexamethylcyclotrisiloxane, the electrolyte [6] In Example 6, a non-aqueous electrolytic solution was prepared in the same manner, and a battery was fabricated using the non-aqueous electrolytic solution, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Example 12

<Production of secondary battery-2>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm by a press, and then cut into a size of 56 mm wide and 850 mm long, as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[Production of non-aqueous electrolyte]

The same non-aqueous electrolytic solution as in the electrolytic solution [6] Example 6 was prepared.

[assembling the battery]

The positive electrode and the negative electrode were overlapped and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact to form an electrode body. The positive and negative terminals are housed in the battery can with the terminals exposed to the outside. Then, 5 mL of a non-aqueous electrolytic solution described later was injected thereinto, and then caulking was performed to manufacture a 18650-type cylindrical battery. The battery has a rated discharge capacity of about 0.7 ampere hours (Ah) and a DC resistance of about 35 milliohms (mΩ) measured by the 10 kHz AC method. For the above battery, the output power and capacity retention were measured in the same manner as in Example 6 of the electrolyte solution [6]. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 1

Electrolyte solution [6] In Example 3, a non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane was used to fabricate a battery, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 2

Electrolyte solution [6] In Example 5, a non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane was used to fabricate a battery, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 3

Electrolyte solution [6] In Example 6, a non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane was used to fabricate a battery, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 4

Electrolyte solution [6] In Example 1, a nonaqueous electrolyte solution prepared without mixing methanol in a mixed nonaqueous solvent was used to fabricate a battery, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the solution one day after mixing LiPF ₆ was 9 ppm, and it was still 9 ppm when measured again 2 weeks later.

Electrolyte [6] Comparative Example 5

Electrolyte solution [6] In Comparative Example 4, a non-aqueous electrolyte solution prepared by mixing 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane was used to fabricate a battery, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 6

Electrolyte solution [6] In Comparative Example 4, a non-aqueous electrolyte solution prepared by mixing 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane was used to manufacture a battery and measure the output Power and capacity retention. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 7

In the electrolyte solution [6] Example 1, except that the mixing amount of methanol was changed to an amount of 700 ppm relative to the mixed non-aqueous solvent, a non-aqueous electrolyte solution was prepared in the same manner as the electrolyte solution [6] Example 1, and the non-aqueous electrolyte solution was used. The water electrolyte was used to make batteries, and the output power and capacity retention were measured. The results are shown in Table 1 of the electrolyte [6]. In addition, the amount of hydrogen fluoride (HF) in the solution one day after mixing LiPF ₆ was 321 ppm, and it was 403 ppm when measured again two weeks later.

Electrolyte [6] Comparative Example 8

Electrolyte solution [6] In Example 1, use the non-aqueous electrolyte solution prepared without mixing methanol and hexamethylcyclotrisiloxane in the mixed non-aqueous solvent to make a battery, and measure the output power and capacity retention Rate. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Comparative Example 9

Except not mixing hexamethylcyclotrisiloxane in the electrolyte solution [6] Example 12, prepare a non-aqueous electrolyte solution in the same manner as the electrolyte solution [6] Example 12, use the non-aqueous electrolyte solution to make a battery, and Determination of output power and capacity retention. The results are shown in Table 1 of the electrolyte [6].

Electrolyte [6] Table 1

[Table 59]

Alcohol HF content (ppm) contains compounds Output power (W) Capacity retention rate (%) Example 1 Methanol 10ppm 14 Hexamethylcyclotrisiloxane 481 71.0 Example 2 Methanol 20ppm 19 Hexamethylcyclotrisiloxane 489 71.0 Example 3 Methanol 35ppm 27 Hexamethylcyclotrisiloxane 498 70.9 Example 4 EG 15ppm 16 Hexamethylcyclotrisiloxane 483 71.0 Example 5 EG 35ppm 27 Hexamethylcyclotrisiloxane 498 70.9 Example 6 Methanol 25ppm EG 25ppm 36 Hexamethylcyclotrisiloxane 507 70.9 Example 7 Methanol 10ppm 14 Lithium difluorophosphate 492 71.3 Example 8 Methanol 35ppm 27 Lithium difluorophosphate 506 71.1 Example 9 EG 15ppm 16 Lithium difluorophosphate 494 71.3 Example 10 Methanol 25ppm EG 25ppm 36 Lithium difluorophosphate 519 71.0 Example 11 Methanol 25ppm EG 25ppm 36 Trimethylsilyl methanesulfonate 509 70.9 Example 12 Methanol 25ppm EG 25ppm 36 Hexamethylcyclotrisiloxane 45.7 70.4 Comparative example 1 Methanol 35ppm 27 none 395 69.5 Comparative example 2 EG 35ppm 27 none 395 69.6 Comparative example 3 Methanol 25ppm EG 25ppm 36 none 393 68.8 Comparative example 4 none 9 Hexamethylcyclotrisiloxane 462 71.0 Comparative Example 5 none 9 Lithium difluorophosphate 472 71.3 Comparative example 6 none 9 Trimethylsilyl methanesulfonate 467 71.0 Comparative example 7 Methanol 700ppm 403 Hexamethylcyclotrisiloxane 458 59.6 Comparative example 8 none 9 none 401 70.7 Comparative example 9 Methanol 25ppm EG 25ppm 36 none 38.4 68.5

From Table 1 of the electrolyte [6], it can be seen that the lithium secondary battery of the electrolyte [6] comparative examples 1-3 containing more hydrogen fluoride (HF) is compared with the lithium secondary battery of the electrolyte [6] comparative example 8 , In terms of output power characteristics and cycle characteristics, the electrolyte solution [6] Examples 1 to 11 are inferior to the electrolyte solution in which a specific compound is added. In the two aspects of output power characteristics and cycle characteristics, it is found that the characteristics are improved. . Furthermore, in terms of output power, the lithium secondary batteries of the electrolyte [6] Examples 1 to 11, and the lithium secondary batteries of the comparative examples 4 to 6 in the electrolyte [6] containing a specific compound but with a small amount of hydrogen fluoride (HF) Compared with the secondary battery, it has higher performance, and the surprising result of enhancing the output power improvement effect by the specific compound was obtained by the presence of hydrogen fluoride. However, in the lithium secondary battery of Comparative Example 7, which contained an excess amount of hydrogen fluoride (HF) in the electrolytic solution [6], particularly poor cycle characteristics were obtained.

In addition, the output power increase rate of the electrolyte [6] Example 12 of the battery structure with low capacity and high DC resistance is only about 19% relative to the electrolyte [6] Comparative Example 9. On the other hand, the high capacity, DC resistance The output power increase rate of the electrolyte solution [6] embodiment 6 of the low battery structure is about 29% relative to the electrolyte solution [6] comparative example 3 (both containing methanol 25ppm and ethylene glycol 25ppm), and the electrolyte solution [6] implements The output power increase rate of example 5 is about 26% with respect to electrolyte solution [6] comparative example 2 (both containing ethylene glycol 35ppm), and electrolyte solution [6] embodiment 3 is relative to electrolyte solution [6] comparative example 1 (both Containing methanol 35ppm) the output power increase rate is about 26%, which is relatively large. From this, it can be seen that the effect of the present invention is particularly large in a battery structure with high capacity and low DC resistance.

As mentioned above, by using the non-aqueous electrolytic solution of the present invention, that is, the non-aqueous electrolytic solution for secondary batteries formed by mixing fluorine-containing lithium salt in the non-aqueous solvent, the cycle characteristics will not deteriorate, and a large battery life can be obtained. Output power characteristics, the non-aqueous electrolyte solution for secondary batteries is characterized by: the hydrogen fluoride (HF) in the above-mentioned non-aqueous electrolyte solution is 10 ppm to 300 ppm, and also contains at least one compound selected from the following substances, and its The content in all non-aqueous electrolyte solutions is more than 10ppm, and the substances include: cyclic siloxane compounds represented by general formula (1), fluorosilane compounds represented by general formula (2), fluorosilane compounds represented by general formula (3) Compounds, compounds with S-F bonds in their molecules, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates and propionates.

In this embodiment, by adding alcohols to the purified non-aqueous solvent, the effect can be exerted, but when the non-aqueous solvent originally contains alcohols or water, by adjusting the purification conditions of the non-aqueous solvent, it is not necessary to add alcohols deliberately, which can to get the same effect. In general, the purification of non-aqueous solvents requires time and effort and increases industrial costs. However, in the present invention, a high-performance non-aqueous electrolytic solution can be produced without unnecessary purification, which is very valuable.

Electrolyte [7] <Battery Production-1>

[production of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[Production of Negative Electrode]

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose as a thickener in 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name) (the concentration of sodium carboxymethylcellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm with a press, and then cut into a size of 56 mm wide and 850 mm long as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[Preparation of Electrolyte Solution]

Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 3:3:4, 1 mol/L Concentration Dissolve fully dry lithium hexafluorophosphate (LiPF ₆ ) to prepare non-aqueous electrolyte solution (1). Further, 0.5% by mass of lithium difluorophosphate prepared according to the method described on pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5 (7) was contained in the non-aqueous electrolytic solution (1) to prepare a non-aqueous electrolytic solution (1). Water electrolyte (2).

[assembling the battery]

The positive electrode and the negative electrode were overlapped and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact to form an electrode body. The positive and negative terminals are housed in the battery can with the terminals exposed to the outside. Then, 5 mL of a non-aqueous electrolytic solution described later was injected thereinto, and then caulking was performed to manufacture a 18650-type cylindrical battery.

[evaluation of the battery]

(initial charge and discharge)

The manufactured cylindrical battery was charged to 4.2V at 25° C. by a constant current constant voltage charging method of 0.2C, and then discharged to 3.0V by a constant current of 0.2C. This was performed for 5 cycles to stabilize the battery. The discharge capacity at the 5th cycle at this time was taken as the initial capacity. In addition, the current value of the 1-hour discharge rated capacity which depends on the 1-hour-rate discharge capacity is defined as 1C.

(cycle test)

The battery subjected to the initial charge and discharge was charged to 4.2V at a constant current and constant voltage of 1C at 60°C, and then discharged to 3.0V at a constant current of 1C, and such charge and discharge were performed for 500 cycles. The ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle at this time was defined as the cycle retention ratio.

(low temperature test)

The battery subjected to the initial charge and discharge was charged to 4.2V by a 0.2C constant current constant voltage charging method at 25°C, and then a 0.2C constant current discharge was performed at -30°C. The discharge capacity at this time was taken as the initial low-temperature capacity, and the ratio of the initial low-temperature capacity to the initial capacity was taken as the initial low-temperature discharge rate.

In addition, the battery after the cycle test was charged to 4.2V at 25°C by a constant current constant voltage charging method of 0.2C, and then discharged to 3.0V by a constant current of 0.2C. Three cycles were performed on it, and the discharge capacity at the third cycle was taken as the post-cycle capacity. Then, the same battery was charged to 4.2V by a 0.2C constant current constant voltage charging method at 25°C, and then a 0.2C constant current discharge was performed at -30°C. The discharge capacity at this time was taken as the post-cycle low-temperature capacity, and the ratio of the post-cycle low-temperature capacity to the post-cycle capacity was taken as the post-cycle low-temperature discharge rate.

Electrolyte [7] Embodiment 1

In the nonaqueous electrolytic solution (2), vinylene carbonate (hereinafter abbreviated as "VC") was mixed in an amount of 1% by mass relative to the mass of the entire electrolytic solution to prepare a nonaqueous electrolytic solution (3). Using this non-aqueous electrolytic solution (3), a 18650-type battery was produced, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7]. In addition, the electrolytic solution was recovered from the battery after the initial charge and discharge by a centrifuge, and the amount of VC measured was 0.40% by mass.

Electrolyte [7] Comparative Example 1

Using the non-aqueous electrolytic solution (1), a 18650-type battery was produced in the same manner as in the electrolytic solution [7] Example 1, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Comparative Example 2

In the nonaqueous electrolytic solution (1), VC was mixed in an amount of 1% by mass relative to the total electrolytic solution mass to prepare a nonaqueous electrolytic solution (4). Using this non-aqueous electrolytic solution (4), a 18650-type battery was produced in the same manner as in the electrolytic solution [7] Example 1, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7]. In addition, the electrolytic solution was recovered from the battery after the initial charge and discharge by a centrifuge, and the measured amount of VC was 0.22% by mass.

Electrolyte [7] Comparative Example 3

A 18650-type battery was produced in the same manner as in Example 1 of the electrolyte solution [7] except that the non-aqueous electrolyte solution (2) was used and VC was not mixed, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Comparative Example 4

In the nonaqueous electrolytic solution (2), VC was mixed in an amount of 5% by mass relative to the total electrolytic solution mass to prepare a nonaqueous electrolytic solution (5). In the electrolyte solution [7] Example 1, the non-aqueous electrolyte solution (5) was used to manufacture a 18650-type battery, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Example 2

<Production of battery-2>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm). Then, 20 mL of the non-aqueous electrolytic solution (3) was injected into the battery can containing the electrode group to fully soak the electrodes, and sealed to manufacture a square battery.

For the prismatic battery produced in this way, a cycle test and a low temperature test were carried out in the same manner as in Example 1 of the electrolyte solution [7], and the cycle retention rate and low temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Comparative Example 5

Electrolyte solution [7] In Example 2, the non-aqueous electrolyte solution (1) was used instead of the non-aqueous electrolyte solution (3) to make a square battery, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Comparative Example 6

Electrolyte solution [7] In Example 2, the non-aqueous electrolyte solution (4) was used instead of the non-aqueous electrolyte solution (3) to make a square battery, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Comparative Example 7

Electrolyte solution [7] In Example 2, the non-aqueous electrolyte solution (2) was used instead of the non-aqueous electrolyte solution (3) to make a square battery, and the cycle retention rate and low-temperature discharge rate were measured. The results are shown in Table 1 of the electrolyte [7].

Electrolyte [7] Table 1

[Table 60]

No. Battery VC LiPO₂F₂ Initial capacity (mAh) DC resistance (mΩ) Cycle retention rate (%) Initial low temperature discharge rate (%) Low temperature after cycle Discharge rate (%) Example 1 Cylinder 1% have 702 35 79 68 69 Comparative example 1 Cylinder none none 700 35 64 61 54 Comparative example 2 Cylinder 1% none 701 35 74 59 56 Comparative example 3 Cylinder none have 700 35 65 68 64 Comparative example 4 Cylinder 5% have 699 35 84 37 29 Example 2 square 1% have 6010 5 85 73 75 Comparative Example 5 square none none 6005 5 70 63 57 Comparative example 6 square 1% none 6003 5 78 60 57 Comparative example 7 square none have 6006 5 72 72 69

From electrolytic solution [7] Table 1, it can be known that the lithium secondary battery of the electrolytic solution [7] embodiment 1 containing vinylene carbonate and difluorophosphate in the non-aqueous electrolytic solution is the same as the lithium secondary battery except that they are not contained in the non-aqueous electrolytic solution. In addition, compared with the lithium secondary battery of Comparative Example 1, the electrolyte solution [7] with the same structure has improved cycle retention rate and low-temperature discharge rate.

In addition, it can be seen that both the cycle retention rate and the low-temperature discharge rate are improved compared with the lithium secondary battery of Comparative Example 2 having the same structure as the electrolyte solution [7] except that only VC is contained in the non-aqueous electrolyte solution. The cycle retention varies significantly depending on the presence or absence of VC, but the effect is increased by adding difluorophosphate thereto. There is about a 2-fold difference in the amount of VC detected from the battery after the initial charge and discharge, and it is considered that the remaining VC suppresses battery deterioration in the cycle test.

From the example 1 of the electrolyte solution [7] and the comparative example 3 of the electrolyte solution [7], it can be seen that the cycle retention rate cannot be sufficiently improved only by difluorophosphate. In addition, although the initial low-temperature discharge rate of the lithium secondary battery of the electrolyte [7] Example 1 is the same as that of the lithium secondary battery of the electrolyte [7] Comparative Example 3, not only the cycle retention rate is greatly improved, but also The low-temperature discharge efficiency was also improved after cycling. By the synergistic effect of VC and difluorophosphate, the increase in the internal resistance of the battery due to the cycle test was suppressed.

The above is also the same between the electrolytic solution [7] Example 2 and the electrolytic solution [7] Comparative Examples 5 to 7.

If the lithium secondary battery of electrolyte [7] Example 1 is compared with the lithium secondary battery of electrolyte [7] Comparative Example 4 containing more VC, it can be seen that in electrolyte [7] Comparative Example 4, although The cycle retention rate is quite excellent, but the low-temperature discharge characteristics are remarkably poor, and it cannot withstand use in a low-temperature environment.

The table shows the values of DC resistance measured by the 10 kHz AC method. Compared with the cylindrical battery, the square battery in this experiment has smaller resistance and higher capacitance. Compared with the improvement degree of low-temperature characteristics of electrolyte solution [7] Example 1 relative to electrolyte solution [7] Comparative Example 1, the degree of improvement of low-temperature characteristics of electrolyte solution [7] Example 2 relative to electrolyte solution [7] Comparative Example 5 It can be seen that a secondary battery with high capacitance or a secondary battery with small DC resistance is particularly suitable as the object of implementation of the non-aqueous electrolyte solution of the present invention.

Electrolyte [8] <Production of secondary battery>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm) with a vent valve. Then, 20 mL of a non-aqueous electrolytic solution described later was poured into the battery can containing the electrode group, the electrodes were sufficiently permeated, and sealed to produce a square battery.

The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the secondary battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz alternating current method is about 5 milliohms ( mΩ).

Electrolyte [8] <Battery Evaluation>

[Cycle Retention Rate]

[Initial charge and discharge]

After charging to 4.2V with a constant current and constant voltage charging method of 0.2C at 25°C, it was discharged to 3.0V with a constant current of 0.2C. This was performed for 5 cycles to stabilize the battery. The discharge capacity at the 5th cycle at this time was taken as the initial capacity. Furthermore, the current value of the rated discharge capacity for 1 hour was defined as 1C.

(cycle test)

The battery subjected to initial charge and discharge was charged to 4.2V at 60° C. with a constant current and constant voltage method of 1C, and then discharged to 3.0V with a constant current of 1C, and the charge and discharge were performed for 500 cycles. The ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle at this time was defined as the cycle retention ratio.

[Initial low temperature discharge rate]

(low temperature test)

The battery subjected to the initial charge and discharge was charged to 4.2V by a 0.2C constant current constant voltage charging method at 25°C, and then a 0.2C constant current discharge was performed at -30°C. The discharge capacity at this time was taken as the initial low-temperature capacity, and the ratio of the initial low-temperature capacity to the initial capacity was taken as the initial low-temperature discharge rate.

[Low temperature discharge rate after cycle]

In addition, the battery after the cycle test was charged to 4.2V at 25°C by a constant current and constant voltage charging method of 0.2C, and then discharged to 3.0V by a constant current of 0.2C. Three cycles were performed on it, and the discharge capacity at the third cycle was taken as the capacity after cycle. Then, the same battery was charged to 4.2V by a 0.2C constant current constant voltage charging method at 25°C, and then a 0.2C constant current discharge was performed at -30°C. The discharge capacity at this time was taken as the post-cycle low-temperature capacity, and the ratio of the post-cycle low-temperature capacity to the post-cycle capacity was taken as the post-cycle low-temperature discharge rate.

Electrolyte [8] Embodiment 1

Under a dry argon atmosphere, LiPF ₆ was added at 1 mol/L to a mixture of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) (volume ratio 2:5:3), It was dissolved, and the mixed solution contained 0.3% by mass of hexamethylcyclotrisiloxane and 1% by mass of vinylethylene carbonate to prepare a non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the above-mentioned method, and the cycle retention rate, initial low-temperature discharge rate and low-temperature discharge rate after cycle were measured. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 2

Except using phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane to make a non-aqueous electrolyte, a battery was made in the same manner as in Example 1 of the electrolyte [8], and the cycle retention rate and initial low-temperature discharge were measured. rate and low temperature discharge rate after cycling. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Example 3

Except using methyl fluorosulfonate instead of hexamethylcyclotrisiloxane to make non-aqueous electrolyte, make battery in the same way as electrolyte [8] embodiment 1, and measure cycle retention rate, initial low temperature discharge rate and Low temperature discharge rate after cycle. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 4

In addition to using lithium difluorophosphate prepared according to the method described on pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5(7) to replace hexamethylcyclotrisiloxane to make a non-aqueous electrolyte , A battery was produced in the same manner as in Example 1 of the electrolyte solution [8], and the cycle retention rate, initial low-temperature discharge rate and low-temperature discharge rate after cycle were measured. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 5

Except using 1,3-propane sultone instead of vinyl ethylene carbonate to make non-aqueous electrolyte, make battery in the same way as electrolyte [8] embodiment 1, and measure cycle retention rate, initial low temperature discharge rate and Low temperature discharge rate after cycle. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 6

Except that γ-butyrolactone was used instead of vinyl ethylene carbonate to make non-aqueous electrolyte, a battery was made in the same manner as in Example 1 of electrolyte [8], and the cycle retention rate, initial low temperature discharge rate and low temperature after cycle were measured. discharge rate. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 7

In addition to using fluoroethylene carbonate instead of vinyl ethylene carbonate to make a non-aqueous electrolyte, a battery was made in the same manner as in Example 1 of the electrolyte [8], and the cycle retention rate, initial low-temperature discharge rate, and low-temperature after cycle were measured. discharge rate. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 8

Except using 1,3-propane sultone instead of vinyl ethylene carbonate to make non-aqueous electrolyte, make battery in the same way as electrolyte [8] embodiment 4, and measure cycle retention rate, initial low temperature discharge rate and Low temperature discharge rate after cycle. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 9

Except using gamma-butyrolactone instead of vinyl ethylene carbonate to make a non-aqueous electrolyte, make a battery in the same way as the electrolyte [8] Example 4, and measure the cycle retention rate, initial low-temperature discharge rate and low-temperature after cycle discharge rate. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Embodiment 10

In addition to using fluoroethylene carbonate instead of vinyl ethylene carbonate to make a non-aqueous electrolyte, a battery was made in the same manner as in Example 4 of the electrolyte [8], and the cycle retention rate, initial low-temperature discharge rate, and low-temperature after cycle were measured. discharge rate. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Comparative Example 1

Except that the non-aqueous electrolyte solution does not contain hexamethylcyclotrisiloxane, a battery was produced in the same manner as the electrolyte solution [8] Example 1, and the cycle retention rate, initial low-temperature discharge rate and low-temperature discharge rate after cycle were measured. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Comparative Example 2

Except that the non-aqueous electrolytic solution does not contain vinyl ethylene carbonate, a battery was produced in the same manner as the electrolytic solution [8] Example 1, and the cycle retention rate, initial low-temperature discharge rate and low-temperature discharge rate after cycle were measured. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Comparative Example 3

Except making the non-aqueous electrolytic solution not contain hexamethylcyclotrisiloxane and vinyl ethylene carbonate, a battery was produced in the same manner as the electrolytic solution [8] Example 1, and the cycle retention rate, initial low-temperature discharge rate and Low temperature discharge rate after cycle. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Example 11

<Production of secondary battery-2>

[making of positive electrode]

90% by mass of lithium cobaltate (LiCoOx) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder were mixed in N-methylpyrrolidone solvent , to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 20 μm, dried, and rolled to a thickness of 80 μm by a press machine, and then cut into a size of 52 mm in width and 830 mm in length as a positive electrode. Among them, an uncoated portion of 50 mm was provided in the longitudinal direction on both the front and back sides, and the length of the active material layer was 780 mm.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was uniformly coated on both sides of a copper foil with a thickness of 18 μm as the negative electrode current collector, and after drying, it was rolled to a thickness of 85 μm by a press, and then cut into a size of 56 mm wide and 850 mm long, as the negative electrode . Among them, an uncoated portion of 30 mm was provided in the longitudinal direction on both the front and back sides.

[assembling the battery]

The positive electrode and the negative electrode were overlapped and wound together with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact to form an electrode body. The positive and negative terminals are housed in the battery can with the terminals exposed to the outside. Then, 5 mL of a non-aqueous electrolytic solution described later was injected thereinto, and then caulking was performed to manufacture a 18650-type cylindrical battery. The capacitance of the battery element contained in one battery case of the secondary battery, that is, the rated discharge capacity of the battery is about 0.7 ampere hours (Ah), and the DC resistance component measured by the 10kHz alternating current method is about 35 milliohms (mΩ ).

Use the non-aqueous electrolyte used in Example 1 of the electrolyte [8] as the non-aqueous electrolyte to make a cylindrical battery, and measure the cycle retention rate, the initial low-temperature discharge rate and the low-temperature discharge rate after the cycle. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Example 12

Except using the non-aqueous electrolytic solution used in the electrolytic solution [8] Example 4 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [8] Example 11, and the cycle retention rate and the initial low-temperature discharge rate were measured. and low temperature discharge rate after cycling. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Comparative Example 4

Except using the non-aqueous electrolytic solution used in the electrolytic solution [8] Comparative Example 1 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [8] Example 11, and the cycle retention rate and initial low-temperature discharge rate were measured. and low temperature discharge rate after cycling. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Comparative Example 5

Except using the non-aqueous electrolytic solution used in the electrolytic solution [8] Comparative Example 2 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [8] Example 11, and the cycle retention rate and initial low-temperature discharge rate were measured. and low temperature discharge rate after cycling. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Comparative Example 6

Except using the non-aqueous electrolytic solution used in the electrolytic solution [8] Comparative Example 3 as the non-aqueous electrolytic solution, a cylindrical battery was produced in the same manner as the electrolytic solution [8] Example 11, and the cycle retention rate and initial low-temperature discharge rate were measured. and low temperature discharge rate after cycling. The results are shown in Table 1 of the electrolyte [8].

Electrolyte [8] Table 1

[Table 61]

No. Specific Compound A Specific compound B Cycle retention rate (%) Initial Low Temperature Discharge Rate (%) Low temperature after cycle Discharge rate (%) Example 1 Hexamethylcyclotrisiloxane Vinyl ethylene carbonate 83 74 73 Example 2 phenyl dimethyl fluorosilane Vinyl ethylene carbonate 81 71 69 Example 3 Methyl fluorosulfonate Vinyl ethylene carbonate 80 70 69 Example 4 Lithium difluorophosphate Vinyl ethylene carbonate 84 76 75 Example 5 Hexamethylcyclotrisiloxane 1,3-Propane sultone 82 72 69 Example 6 Hexamethylcyclotrisiloxane γ-butyrolactone 79 73 66 Example 7 Hexamethylcyclotrisiloxane Fluoroethylene carbonate 83 73 70 Example 8 Lithium difluorophosphate 1,3-Propane sultone 83 73 72 Example 9 Lithium difluorophosphate γ-butyrolactone 80 73 69 Example 10 Lithium difluorophosphate Fluoroethylene carbonate 84 74 73 Comparative example 1 - Vinyl ethylene carbonate 76 58 51 Comparative example 2 Hexamethylcyclotrisiloxane - 72 73 66 Comparative example 3 - - 68 65 54 Example 11 Hexamethylcyclotrisiloxane Vinyl ethylene carbonate 69 67 65 Example 12 Lithium difluorophosphate Vinyl ethylene carbonate 70 69 67 Comparative example 4 - Vinyl ethylene carbonate 65 54 49 Comparative Example 5 Hexamethylcyclotrisiloxane - 60 66 60 Comparative example 6 - - 58 60 52

From the electrolyte [8] Table 1, it can be seen that if each square battery (electrolyte [8] embodiment 1-10, electrolyte [8] used in comparative examples 1-3), cylindrical battery (electrolyte [8] ] Embodiment 11,12, electrolyte solution [8] used in comparative examples 4～6) is compared, then the electrolyte solution [8] that contains at least one specific compound A and at least one specific compound B in the non-aqueous electrolyte solution simultaneously The lithium secondary battery of the example, compared with the lithium secondary battery of the comparative example that does not contain any of these electrolyte solutions [8], has improved cycle retention rate, initial low-temperature discharge rate, and low-temperature discharge rate after cycle.

As described above, the rated discharge capacity of the prismatic batteries of this example and this comparative example is 3 ampere hours (Ah) or more, and the DC resistance component is 10 milliohms (mΩ) or less. On the other hand, the rated discharge capacity of the cylindrical batteries of this embodiment and this comparative example is less than 3 ampere hours (Ah), and the DC resistance component is greater than 10 milliohms (mΩ). That is, the prismatic batteries of this example and this comparative example have lower resistance and higher capacitance than cylindrical batteries. Moreover, the output power increase degree of the electrolyte solution [8] Example 1 relative to the electrolyte solution [8] Comparative Example 1 is higher than the output power increase degree of the electrolyte solution [8] Example 11 relative to the electrolyte solution [8] Comparative Example 4 Large, the effect of the present invention is greater in a secondary battery with a large capacitance or a secondary battery with a small DC resistance.

Electrolyte [9] <Production of secondary battery>

[making of positive electrode]

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 80 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode.

[Production of Negative Electrode]

In 98 parts by weight of artificial graphite powder KS-44 (manufactured by timcal company, trade name), add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass %), 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass), and mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a copper foil with a thickness of 10 μm, dried, rolled to a thickness of 75 μm with a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated layer with a width of 30 mm. The shape of the part, as the negative pole.

[assembling the battery]

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The respective uncoated parts of the positive and negative electrodes were welded to produce current collector sheets, and the electrode group was sealed in a battery can (outer dimensions: 120×110×10 mm) with a vent valve. Then, 20 mL of non-aqueous electrolytic solution was poured into the battery can containing the electrode group, the electrodes were fully soaked, and sealed to produce a square battery.

[Capacitance and DC resistance components]

The rated discharge capacity of this battery (capacitance of the battery element contained in one battery case) is a high capacity of about 6Ah, and the DC resistance component measured by the 10kHz AC method is about 5 milliohms.

[evaluation of the battery]

(measurement method of capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.2V to 3.0V, with a current value of 0.2C (the current value of the rated capacity of 1 hour discharge is taken as 1C, and the rated capacity depends on 1 One-hour-rate (one-hour-rate) discharge capacity, the same below) was performed for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the capacity.

(5C discharge capacity after storage)

The storage test was carried out in a high-temperature environment of 60°C. The battery previously charged to a charging upper limit voltage of 4.2 V by a constant current constant voltage method in an environment of 25° C. was stored at 60° C. for one month. For the stored batteries, perform a speed test at 25°C. That is, a battery previously charged to a charging upper limit voltage of 4.2V by the constant current and constant voltage method in an environment of 25°C was discharged at a constant current value equivalent to 5C, which was used as the 5C discharge capacity after storage.

(overcharge test)

The overcharge test was carried out in an environment of 25°C. It was charged with a constant current of 3C from the discharged state (3V), and its behavior was observed. Among them, "valve operation" refers to the phenomenon in which the exhaust valve operates to release the electrolyte components, and "rupture" refers to the phenomenon in which the battery container ruptures violently and the contents are forcibly released.

Electrolyte [9] Embodiment 1

Under a dry argon atmosphere, add lithium hexafluorophosphate (LiPF ₆ ), and dissolve, mix the cyclohexylbenzene (CHB) of the amount of 1 mass % and the hexamethylcyclotrisiloxane of the amount of 0.3 mass % in this mixed solution, prepare non-aqueous electrolytic solution. Using this non-aqueous electrolytic solution, a battery was produced by the above method, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 2

A non-aqueous electrolytic solution prepared by mixing phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in Example 1 of the electrolytic solution [9] was used to fabricate a battery, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 3

Use the non-aqueous electrolyte prepared by mixing trimethylsilyl methanesulfonate to replace the hexamethylcyclotrisiloxane in the electrolyte [9] Example 1, make a battery, and measure the 5C discharge after storage capacity. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 4

Use lithium difluorophosphate prepared according to the method described in Inorganic Nuclear Chemistry Letters (1969), 5 (7) on page 581 to page 582 to replace the hexamethyl ring in the electrolyte [9] Example 1 The non-aqueous electrolyte solution prepared from trisiloxane was used to make batteries, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 5

A non-aqueous electrolytic solution prepared by mixing biphenyl instead of cyclohexylbenzene in Example 1 of the electrolytic solution [9] was used to fabricate a battery, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 6

A non-aqueous electrolytic solution prepared by mixing phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in Example 5 of the electrolytic solution [9] was used to fabricate a battery, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 7

Use the non-aqueous electrolyte prepared by mixing trimethylsilyl methanesulfonate to replace the hexamethylcyclotrisiloxane in the electrolyte [9] embodiment 5, make the battery, and measure the 5C discharge after storage capacity. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 8

Use lithium difluorophosphate prepared according to the method described in Inorganic Nuclear Chemistry Letters (1969), 5 (7) on page 581 to page 582 to replace the hexamethyl ring in the electrolyte [9] Example 5 The non-aqueous electrolyte solution prepared from trisiloxane was used to make batteries, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 9

A non-aqueous electrolytic solution prepared by mixing tert-amylbenzene instead of cyclohexylbenzene in Example 1 of the electrolytic solution [9] was used to fabricate a battery, and the 5C discharge capacity after storage was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Embodiment 10

A non-aqueous electrolytic solution prepared by using a "partial hydrogenated product of m-terphenyl" mixed with a m-terphenyl content of 3.7% by mass and a partial hydrogenation rate of 42% instead of cyclohexylbenzene in the electrolyte [9] Example 1 solution, make a battery, and measure the 5C discharge capacity after storage. The results are shown in Table 1 of the electrolyte [9]. In addition, the partial hydrogenation of m-terphenyl used in the embodiment of the electrolyte [9] uses m-terphenyl as a raw material, and under the coexistence of platinum, palladium or nickel catalyst, it is mixed with hydrogen under high temperature and pressure. The substance obtained by the reaction. In addition, the partial hydrogenation rate was determined by taking the average of the composition ratios of the constituent components of the partially hydrogenated product of m-terphenyl obtained by gas chromatography analysis. The content of m-terphenyl was also obtained from the gas chromatographic analysis value.

Electrolyte [9] Comparative Example 1

A battery was fabricated using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 1 of the electrolyte solution [9], and the 5C discharge capacity was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Comparative Example 2

A battery was fabricated using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 5 of the electrolyte solution [9], and the 5C discharge capacity was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Comparative Example 3

A battery was manufactured using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 9 of the electrolyte solution [9], and the 5C discharge capacity was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Comparative Example 4

A battery was fabricated using the non-aqueous electrolyte solution prepared without mixing hexamethylcyclotrisiloxane in Example 10 of the electrolyte solution [9], and the 5C discharge capacity was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Comparative Example 5

A battery was fabricated using the non-aqueous electrolytic solution prepared without mixing either hexamethylcyclotrisiloxane or CHB in Example 1 of the electrolytic solution [9], and the 5C discharge capacity was measured. The results are shown in Table 1 of the electrolyte [9].

Electrolyte [9] Table 1

[Table 62]

No. Anti-overcharge agent specific compound 5C discharge capacity after storage (mAh) overcharge test Example 1 Cyclohexylbenzene Hexamethylcyclotrisiloxane 4016 valve work Example 2 Cyclohexylbenzene phenyl dimethyl fluorosilane 3967 valve work Example 3 Cyclohexylbenzene Trimethylsilyl methanesulfonate 4023 valve work Example 4 Cyclohexylbenzene Lithium difluorophosphate 4062 valve work Example 5 Biphenyl Hexamethylcyclotrisiloxane 3810 valve work Example 6 Biphenyl phenyl dimethyl fluorosilane 3772 valve work Example 7 biphenyl Trimethylsilyl methanesulfonate 3806 valve work Example 8 Biphenyl Lithium difluorophosphate 3855 valve work Example 9 tert-amylbenzene Hexamethylcyclotrisiloxane 4004 valve work Example 10 Partial hydride of m-terphenyl Hexamethylcyclotrisiloxane 3959 valve work Comparative example 1 Cyclohexylbenzene none 3522 valve work Comparative example 2 biphenyl none 3217 valve work Comparative example 3 tert-amylbenzene none 3511 valve work Comparative example 4 Partial hydride of m-terphenyl none 3403 valve work Comparative Example 5 none none 4091 burst

It can be seen from Table 1 of the electrolyte solution [9] that the lithium secondary batteries of the electrolyte solution [9] Examples 1 to 10 containing an overcharge preventing agent and a specific compound in the non-aqueous electrolyte solution are self-evident in the overcharge test. It can avoid battery rupture, and it also shows more excellent characteristics than the lithium secondary batteries of the electrolyte [9] Comparative Examples 1-4 in the high-current (5C) discharge test after storage. This characteristic is close to that of the lithium secondary battery of Comparative Example 5 of the electrolytic solution [9] that does not contain an overcharge preventing agent, and it can be seen that the practical value is very high while improving overcharge safety.

As described above, high large-current discharge characteristics and overcharge safety can be simultaneously satisfied by using a non-aqueous electrolyte solution for a secondary battery formed by mixing a lithium salt in a non-aqueous solvent having the following characteristics. The non-aqueous electrolytic solution for batteries is characterized by: containing an overcharge preventing agent, and at least one compound selected from the following substances, and its content in all non-aqueous electrolytic solutions is more than 10ppm, and said substances include: Cyclic siloxane compound represented by general formula (1), fluorosilane compound represented by general formula (2), compound represented by general formula (3), compound having S-F bond in the molecule, nitrate, nitrite, mono Fluorophosphates, difluorophosphates, acetates and propionates. In particular, it is highly practical for a battery in which the capacity of the battery element housed in one battery case is 3 ampere-hours (Ah) or more, and it has been difficult to satisfy these two elements at the same time.

Structure [1]～[5] Embodiment 1

"Preparation of Non-Aqueous Electrolyte"

Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:3:4 at a concentration of 1 mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). In addition, 0.3% by mass of hexamethylcyclotrisiloxane was contained.

"Positive Production"

The positive electrode active material is a lithium transition metal composite oxide synthesized by the following method, represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ . Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co(OH) ₂ as a cobalt raw material were weighed at a molar ratio of Mn:Ni:Co=1:1:1, and pure water was added thereto to prepare For the slurry, wet pulverize the solid components in the slurry to a median particle size of 0.2 μm by using a circulating medium agitation type wet bead mill while stirring.

The slurry was spray-dried by a spray dryer to obtain roughly spherical granulated particles having a particle diameter of about 5 μm and containing only manganese raw materials, nickel raw materials, and cobalt raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles, and the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials, cobalt Raw material, granulated particles of manganese raw material and mixed powder of lithium raw material. The mixed powder was calcined at 950° C. for 12 hours under air circulation (the heating and cooling rate was 5° C./min), then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material. The positive electrode active material had a BET specific surface area of 1.2 m ² /g, an average primary particle size of 0.8 μm, a median particle size d ₅₀ of 4.4 μm, and a tap density of 1.6 g/cm ³ .

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled to a thickness of 81 μm with a press, and cut into an active material layer having a width of 100 mm and a length of 100 mm and an uncoated portion of a width of 30 mm. shape, as the positive electrode. The density of the positive electrode active material layer was 2.35 g/cm ³ , (thickness of positive electrode active material layer on one surface)/(thickness of current collector) was 2.2, and L/(2×S ₂ ) was 0.2.

"The Making of Negative Pole"

In order to prevent the commercially available natural graphite powder, which is a granular carbonaceous material, from being mixed with coarse particles, the sieve was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode material thus obtained is referred to as a carbonaceous substance (A).

Petroleum heavy oil obtained during the pyrolysis of naphtha is mixed with the carbonaceous substance (A), carbonized at 1300°C in an inert gas, and then the composite carbonaceous substance is obtained by classifying the sintered product as a negative electrode In the active material, the composite carbonaceous substance is a composite carbonaceous substance in which carbonaceous substances having different crystallinity are coated on the surface of the carbonaceous substance (A) particle. During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of low-crystalline carbonaceous material relative to 95 parts by weight of graphite. The physical properties of the negative electrode active material are shown in Table 1 with structures [1]-[5].

Structure [1]～[5] Table 1

[Table 63]

Particle size μm Circularity - Specific surface area m²/g Raman R value - Raman half value width cm^-1 d₀₀₂ nm Ash Content Mass % Micropore distribution mL/g Total Micropore Distribution mL/g True Density g/cm³ Circularity - aspect ratio - Negative active material 15.2 0.93 3.0 0.35 37 0.336 0.07 0.101 0.692 2.25 0.93 1.4

Add 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1% by mass) and 2 parts by weight of a binder in 98 parts by weight of the above-mentioned negative electrode active material. The aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry was coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, and rolled to a thickness of 75 μm with a press machine, and then cut into an active material layer with a width of 104 mm and a length of 104 mm and an uncoated copper foil with a width of 30 mm. The shape of the coated part, as the negative electrode. The density of the negative electrode active material at this time was 1.35 g/cm ³ , and L/(2×S ₂ ) was 0.19.

"Battery Making"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The uncoated parts of the positive and negative electrodes were bundled and spot-welded to form current collector sheets, and the electrode group was sealed in an aluminum battery can (outer dimensions: 120×110×10 mm). As the battery can, a battery can having positive and negative current collector terminals, a pressure release valve, and a non-aqueous electrolytic solution inlet in the lid portion was used. The collector tabs and collector terminals are connected by spot welding. Then, inject 20 mL of non-aqueous electrolytic solution into the battery can containing the electrode group to fully soak the electrodes, seal the injection port, and manufacture a battery. The ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 20.5, 2×S ₁ /T was 264, and the electrode group occupancy ratio was 0.54.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged, at 25°C and a voltage range of 4.1V to 3.0V, use a current value of 0.2C (take the current value of the rated capacity of 1 hour discharge as 1C, and the rated capacity depends on the 1 hour rate ( One-hour-rate) discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as the initial capacity. The results of battery evaluation are shown in Table 2 for structures [1] to [5].

(Measurement method of initial output power)

Charge at a constant current of 0.2C for 150 minutes at 25°C, discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, and measure the voltage at 10 seconds. The area of the triangle surrounded by the current-voltage straight line and the lower limit voltage (3V) is taken as the output power (W). The results of battery evaluation are shown in Table 2 for structures [1] to [5].

(Measurement method of initial series resistance)

Charge at a constant current of 0.2 C for 150 minutes in an environment of 25° C., apply an alternating current of 10 kHz, measure the impedance, and use it as a direct current resistance. The results of battery evaluation are shown in Table 2 for structures [1] to [5].

(Cycle test (measuring method of battery capacity after endurance and output power after endurance))

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the practical upper limit temperature of the lithium secondary battery. After charging to the charging upper limit voltage of 4.1V by the constant current and constant voltage method of 2C, discharge to the end-of-discharge voltage of 3.0V by a constant current of 2C. This charge-discharge cycle is regarded as one cycle, and this cycle is repeated until 500 cycles. For the battery after the cycle test, it was charged and discharged for 3 cycles with a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle was taken as the battery capacity after endurance. In addition, for the battery after the cycle test, the output power was measured as the output power after endurance, and the series resistance was measured as the series resistance after endurance. The results of battery evaluation are shown in Table 2 for structures [1] to [5].

(overcharge test)

The overcharge test was carried out in an environment of 25°C. It was charged with a constant current of 3C from the discharged state (3V), and its behavior was observed. Among them, "valve operation" refers to the phenomenon in which the exhaust valve operates to release the electrolyte components, and "rupture" refers to the phenomenon in which the battery container ruptures violently and the contents are forcibly released. The results of battery evaluation are shown in Table 2 for structures [1] to [5].

Structure [1]～[5] Embodiment 2

The trimethylsilyl methanesulfonate containing 0.3% by mass in the non-aqueous electrolytic solution replaces the hexamethylcyclotrisiloxane in the structure [1]～[5] embodiment 1, in addition, Batteries were produced in the same manner as in Example 1 of structures [1] to [5], and battery evaluations were performed in the same manner. The results are shown in Table 2 of structures [1]-[5].

Structure [1]～[5] Embodiment 3

The non-aqueous electrolyte contains 0.3% by mass of phenyldimethylfluorosilane to replace the hexamethylcyclotrisiloxane in the structure [1]～[5] embodiment 1, in addition, with the structure [ 1] to [5] A battery was produced in the same manner as in Example 1, and battery evaluation was performed in the same manner. The results are shown in Table 2 of structures [1]-[5].

Structure [1]～[5] Embodiment 4

Make the non-aqueous electrolytic solution contain 0.3 mass % lithium difluorophosphate to replace the hexamethylcyclotrisiloxane in the structure [1]～[5] embodiment 1, in addition, with the structure [1]～ [5] A battery was produced in the same manner as in Example 1, and battery evaluation was performed in the same manner. The results are shown in Table 2 of structures [1]-[5].

Structure [1]～[5] Comparative Example 1

Make structure [1]～[5] in the non-aqueous electrolytic solution in the embodiment 1 of [5] do not contain hexamethylcyclotrisiloxane, except that, make in the same way as structure [1]～[5] embodiment 1 battery, and perform battery evaluation in the same way. The results are shown in Table 2 of structures [1]-[5].

Structure [1]～[5] Table 2

[Table 64]

specific compound battery capacity DC Resistance Initial output power Endurance battery capacity DC resistance after durability Output power after durability overcharge test Ah mΩ W Ah mΩ W Example 1 Hexamethylcyclotrisiloxane 6.1 4.8 577 5.4 5.0 395 open valve Example 2 Trimethylsilyl methanesulfonate 6.1 4.9 579 5.4 5.1 403 open valve Example 3 Phenyldimethylfluorosilane 6.1 4.9 572 5.4 5.1 393 open valve Example 4 Lithium difluorophosphate 6.1 4.8 588 5.5 5.0 410 open valve Comparative example 1 none 6.1 5.0 500 5.1 5.5 321 burst

Structure [1]～[5] Embodiment 5

"Positive Production"

Slurry was prepared in the same manner as in Example 1 of Structures [1] to [5] using the same positive electrode active material as in Example 1 of Structures [1] to [5]. The obtained slurry is coated on both sides of an aluminum foil with a thickness of 15 μm, dried, rolled into a thickness of 81 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 3200 mm, and has The shape of an uncoated portion having a width of 6 mm at intervals of 20 mm was used as a positive electrode. The density of the positive electrode active material layer was 2.35 g/cm ³ , and (thickness of the positive electrode active material layer on one surface)/(thickness of the current collector) was 2.2. The ratio of the length in the width direction to the length in the longitudinal direction of the positive electrode was 32.

"The Making of Negative Pole"

Slurry was prepared in the same manner as in Example 1 of Structures [1] to [5] using the same negative electrode active material as in Example 1 of Structures [1] to [5]. The obtained slurry is coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm by a press, and then cut into an active material layer with a width of 104 mm and a length of 3300 mm. The shape of an uncoated portion having a width of 6 mm at intervals of 20 mm in the direction was used as a negative electrode. The density of the negative electrode active material at this time was 1.35 g/cm ³ .

"Battery Making"

A microporous membrane separator (thickness 25 μm) of a porous polyethylene sheet is sandwiched between each electrode so that the positive electrode and the negative electrode do not directly contact each other, and the positive electrode and the negative electrode are overlapped and wound into an uncoated part on the opposite side. Round shape, made of electrode body. The positive electrode and the negative electrode were respectively spot-welded on the central axis of the bundle winding to make a collector sheet to make an electrode group, and the battery group was set in an aluminum battery can (outer dimension: 36φ×120mm) and Make the negative electrode current collector sheet as the bottom. The negative electrode current collector is spot-welded at the bottom of the tank to form a structure in which the battery can is the negative electrode current collector terminal. A battery can lid having a positive electrode collector terminal and a pressure release valve was prepared, and the positive electrode collector tab and the positive electrode collector terminal were connected by spot welding. Then, inject 20 mL of non-aqueous electrolyte solution into the battery can with the electrode group to fully soak the electrodes, and seal the lid of the battery can by riveting to make a cylindrical battery. The ratio of the total electrode area of the positive electrode to the total surface area of the battery case was 41.0, and the electrode group occupancy ratio was 0.58.

"Battery Evaluation"

Battery evaluation was performed in the same manner as in Example 1 with structures [1] to [5] except that the above-mentioned cylindrical battery was used. The structure of the battery evaluation is shown in Table 3 with structures [1] to [5].

Structure [1]～[5] Embodiment 6

In addition to making the non-aqueous electrolyte solution contain 0.3% by mass of trimethylsilyl methanesulfonate to replace hexamethylcyclotrisiloxane in Example 5 of structures [1] to [5], the same structure as [1] ] to [5] A battery was produced in the same manner as in Example 5, and battery evaluation was performed in the same manner. The results are shown in Table 3 of structures [1]-[5].

Structure [1]～[5] Embodiment 7

In addition to making the nonaqueous electrolyte solution contain 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in Example 5 of structures [1] to [5], the structure [1] to [ 5] A battery was produced in the same manner as in Example 5, and battery evaluation was performed in the same manner. The results are shown in Table 3 of structures [1]-[5].

Structure [1]～[5] Embodiment 8

Except that in Example 5 of structures [1] to [5], the non-aqueous electrolyte solution contains 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, and the structure [1] to [5] is implemented. A battery was produced in the same manner as in Example 5, and battery evaluation was performed in the same manner. The results are shown in Table 3 of structures [1]-[5].

Structure [1]～[5] Comparative example 2

Except that the non-aqueous electrolyte solution does not contain hexamethylcyclotrisiloxane in Example 5 of Structures [1] to [5], a battery was produced in the same manner as in Example 5 of Structures [1] to [5], and the same for battery evaluation. The results are shown in Table 3 of structures [1]-[5].

Structure [1]～[5] Table 3

[Table 65]

specific compound battery capacity DC Resistance initial output power Durable battery capacity DC resistance after durability Output power after durability Overcharge test Ah mΩ W Ah mΩ W Example 5 Hexamethylcyclotrisiloxane 6.1 5.7 569 5.3 5.9 386 open valve Example 6 Trimethylsilyl methanesulfonate 6.1 5.6 572 5.3 5.8 389 open valve Example 7 phenyl dimethyl fluorosilane 6.1 5.7 564 5.3 5.9 379 open valve Example 8 Lithium difluorophosphate 6.1 5.6 582 5.3 5.8 399 open valve Comparative example 2 none 6.1 5.9 493 5.0 6.3 303 burst

From the results in Table 2 of structures [1]-[5] and Table 3 of structures [1]-[5], it can be seen that in any battery, by including a specific compound in the nonaqueous electrolyte, the output power, capacity retention rate, safety The performance is improved, and even after the cycle test, the increase of the DC resistance component is small, and the battery capacity and output power are fully maintained.

Structure [6] Embodiment 1

"Preparation of Non-Aqueous Electrolyte"

Under a dry argon atmosphere, in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:3:4 at a concentration of 1 mol/L Dissolve well-dried lithium hexafluorophosphate (LiPF ₆ ). And it was made to contain 0.3 mass % of hexamethylcyclotrisiloxane.

"Positive Production"

The positive electrode active material is a lithium transition metal composite oxide synthesized by the following method, represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ . Weigh Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co(OH) ₂ as a cobalt raw material at a molar ratio of Mn:Ni:Co=1:1:1, and add pure water to make a slurry While stirring, the solid content in the slurry was wet pulverized to a median particle size of 0.2 μm using a circulating medium agitation type wet bead mill.

The slurry was spray-dried by a spray dryer to obtain roughly spherical granulated particles having a particle diameter of about 5 μm and containing only manganese raw materials, nickel raw materials, and cobalt raw materials. LiOH powder with a median diameter of 3 μm was added to the obtained granulated particles, and the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co was 1.05, and mixed with a high-speed mixer to obtain nickel raw materials, cobalt Raw material, granulated particles of manganese raw material and mixed powder of lithium raw material. The mixed powder was calcined at 950° C. for 12 hours under air circulation (the heating and cooling rate was 5° C./min), then pulverized and passed through a sieve with a mesh size of 45 μm to obtain a positive electrode active material. The positive electrode active material had a BET specific surface area of 1.2 m ² /g, an average primary particle size of 0.8 μm, a median particle size d ₅₀ of 4.4 μm, and a tap density of 1.6 g/cm ³ .

Mix 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF ) to make slurry. The obtained slurry is coated on both sides of aluminum foil with a thickness of 15 μm, dried, and rolled to a thickness of 81 μm with a press, and then cut into a positive electrode active material layer with a width of 100 mm and a length of 100 mm, and has a width of 30 mm. The shape of the part, as the positive electrode. The density of the positive electrode active material layer was 2.35 g/cm ³ , (thickness of positive electrode active material layer on one surface)/(thickness of current collector) was 2.2, and L/(2×S ₂ ) was 0.2.

"The Making of Negative Pole"

In order to prevent the commercially available natural graphite powder, which is a granular carbonaceous material, from being mixed with coarse particles, the sieve was repeatedly sieved 5 times using an ASTM400 mesh sieve. The negative electrode material thus obtained is referred to as a carbonaceous substance (A).

Petroleum heavy oil obtained during the pyrolysis of naphtha is mixed with the carbonaceous substance (A), carbonized at 1300°C in an inert gas, and then the composite carbonaceous substance is obtained by classifying the sintered product as a negative electrode In the active material, the composite carbonaceous substance is a composite carbonaceous substance in which carbonaceous substances having different crystallinity are coated on the surface of the carbonaceous substance (A) particle. During the classification process, in order to prevent the mixing of coarse particles, use an ASTM400 mesh sieve to repeatedly sieve 5 times. It was confirmed from the carbon residue rate that the obtained negative electrode active material powder was coated with 5 parts by weight of low-crystalline carbonaceous material relative to 95 parts by weight of graphite. The physical properties of the negative electrode active material are shown in Table 1 of the structure [6].

Structure [6] Table 1

[Table 66]

Particle size μm Circularity - Specific surface area m²/g Raman R value - Raman half value width cm^-1 d₀₀₂ nm Ash Content Mass% Micropore distribution mL/g Total Micropore Distribution mL/g True Density g/cm³ Circularity - Length-to-diameter ratio - Negative active material 15.2 0.93 3.0 0.35 37 0.336 0.07 0.101 0.692 2.25 0.93 1.4

In 98 parts by weight of the above-mentioned negative electrode active material, add 100 parts by weight of the aqueous dispersion of sodium carboxymethyl cellulose as a thickener (the concentration of sodium carboxymethyl cellulose is 1 mass % ) , 2 parts by weight as An aqueous dispersion of styrene-butadiene rubber as a binder (the concentration of styrene-butadiene rubber is 50% by mass) was mixed with a disperser to prepare a slurry. The obtained slurry is coated on both sides of a rolled copper foil with a thickness of 10 μm, dried, rolled into a thickness of 75 μm by a press, and then cut into an active material layer with a width of 104 mm and a length of 104 mm, and has a width of 30 mm. The shape of the uncoated part, as the negative electrode. The density of the negative electrode active material at this time was 1.35 g/cm ³ , and L/(2×S ₂ ) was 0.19.

"Battery Making"

32 positive electrodes and 33 negative electrodes were arranged alternately, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes for lamination. At this time, the surface of the positive electrode active material faces the surface of the negative electrode active material without protruding from the surface of the negative electrode active material. The uncoated parts of the positive and negative electrodes were bundled together, and connected by spot welding together with the metal sheet serving as a current collecting terminal to produce a current collecting sheet and an electrode group. Above, the porous polyethylene sheet clogged the pores above 135°C. As the battery case material, a sheet (total thickness 0.1 mm) obtained by laminating a polypropylene film, an aluminum foil with a thickness of 0.04 mm, and a nylon film in this order was used, and the polypropylene film was formed on the inner side to form a rectangular cup. shell. The polypropylene film had a melting point of 165°C. Enclose the above-mentioned electrode group in the casing and expose the collector terminal from the unsealed part of the upper end of the cup, and inject 20mL of non-aqueous electrolyte solution to fully soak the electrodes. The upper end of the cup was sealed by heat sealing under reduced pressure to produce a battery. The battery was roughly square, and the ratio of the total electrode area of the positive electrode to the total surface area of the case (the surface area of the case material excluding the heat-sealed portion) was 22.6, and (2×S ₁ /T) was 411.

"Battery Evaluation"

(Measuring method of battery capacity)

For a new battery that has not been charged and discharged cycled, at 25°C and a voltage range of 4.1V to 3.0V, use a current value of 0.2C (take the current value of the rated capacity of 1 hour discharge as 1C, and the rated capacity depends on the rate of 1 hour (one-hour-rate discharge capacity, the same below) for 5 cycles of initial charge and discharge. The 0.2C discharge capacity at the fifth cycle at this time was taken as "battery capacity" (Ah). The results of the battery evaluation are shown in Table 3 of the structure [6].

(Measurement method of DC resistance component)

Charge for 150 minutes with a constant current of 0.2C in an environment of 25° C., apply an alternating current of 10 kHz, measure impedance, and use it as a “direct current resistance component” (mΩ). The results of the battery evaluation are shown in Table 3 of the structure [6].

(Measurement method of initial output power)

Charge at a constant current of 0.2C for 150 minutes at 25°C, discharge at 0.1C, 0.3C, 1.0C, 3.0C, and 10.0C for 10 seconds, and measure the voltage at 10 seconds. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3V) is taken as the "initial output power" (W). The results of the battery evaluation are shown in Table 3 of the structure [6].

(cycle test)

(Measurement method of battery capacity after endurance, DC resistance component after endurance, output power after endurance)

The cycle test was performed in a high-temperature environment of 60° C., which is regarded as the practical upper limit temperature of the lithium secondary battery. After charging to the charging upper limit voltage of 4.1V by the constant current and constant voltage method of 2C, it was discharged to the end-of-discharge voltage of 3.0V by the constant current of 2C. This charge-discharge cycle was regarded as one cycle, and this cycle was repeated until 500 cycles. For the battery after the cycle test, it is charged and discharged for 3 cycles with a current value of 0.2C in an environment of 25°C, and the 0.2C discharge capacity of the third cycle is taken as the "endurance battery capacity". In addition, the DC resistance component of the battery after the cycle test was measured as the "DC resistance component after endurance", and the output power was measured as "Output after endurance". The results of the battery evaluation are shown in Table 3 of the structure [6].

(overcharge test)

The overcharge test was carried out in an environment of 25°C. It was charged with a constant current of 3C from the discharged state (3V), and its behavior was observed. Among them, "valve operation" refers to the phenomenon in which the exhaust valve operates to release the non-aqueous electrolyte components, and "rupture" refers to the phenomenon in which the battery container ruptures violently and the contents are forcibly released. The results of the battery evaluation are shown in Table 3 of the structure [6].

(Measuring method of volume change rate)

The volume of the battery in the discharged state (3V) was measured in an environment of 25°C. Volume is determined by adding ethanol to a graduated container and submerging the cell in the ethanol. The ratio of the volume after the cycle test to the volume before the cycle test was defined as the "volume change rate". The evaluation results are shown in Table 3 of the structure [6].

Structure [6] Embodiment 2

A battery was fabricated in the same manner as in Example 1, except that in Example 1 of structure [6], the nonaqueous electrolyte contained 0.3% by mass of trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane. , and perform battery evaluation in the same manner. The results are shown in Table 3 of the structure [6].

Structure [6] Embodiment 3

Produced in the same manner as structure [6] Example 1, except that the non-aqueous electrolytic solution contained 0.3% by mass of phenyldimethylfluorosilane instead of hexamethylcyclotrisiloxane in Structure [6] Example 1 battery, and perform battery evaluation in the same way. The results are shown in Table 3 of the structure [6].

Structure [6] Embodiment 4

Except that in structure [6] Example 1, the nonaqueous electrolyte solution contains 0.3% by mass of lithium difluorophosphate instead of hexamethylcyclotrisiloxane, a battery was produced in the same manner as in Structure [6] Example 1, and Battery evaluation was performed in the same manner. The results are shown in Table 3 of the structure [6].

Structure [6] Comparative Example 1

A battery was produced in the same manner as in Example 1 of Structure [6] except that the non-aqueous electrolyte solution did not contain hexamethylcyclotrisiloxane in Example 1 of Structure [6], and battery evaluation was performed in the same manner. The results are shown in Table 3 of the structure [6].

Structure [6] Table 2

[Table 67]

No. Specific compounds in non-aqueous electrolytes Example 1 Hexamethylcyclotrisiloxane Example 2 Trimethylsilyl methanesulfonate Example 3 phenyl dimethyl fluorosilane Example 4 Lithium difluorophosphate Comparative example 1 none

Structure [6] Table 3

[Table 68]

No. Battery Capacity Ah DC resistance component mΩ Initial output power W Endurance battery capacity Ah DC resistance component after durability mΩ Output power after durability W overcharge test Volume change rate Example 1 6.1 4.3 583 5.3 4.2 394 valve work 1.01 Example 2 6.1 4.2 585 5.3 4.4 398 valve work 1.01 Example 3 6.1 4.3 579 5.3 4.5 388 valve work 1.01 Example 4 6.1 4.3 595 5.3 4.5 407 valve work 1.01 Comparative example 1 6.1 4.5 508 5.0 4.9 318 burst 1.03

From the results of structure [6] Table 3, it can be seen that by including specific compounds in the non-aqueous electrolyte, the initial output power, capacity retention rate, and safety are improved, and the battery capacity and output power can be fully maintained even after the cycle test , the change in battery volume is also small.

Industrial Applicability

The application of the lithium secondary battery of the present invention is not particularly limited, and it can be used in various known applications. Specific examples include notebook personal computers, pen input personal computers, mobile personal computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, convenient vacuum cleaners, portable CDs, mini record players, radio transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, electric motors, automobiles, motorcycles, Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, electric tools, stroboscopes, cameras, etc. The lithium secondary battery of the present invention has a large capacity, excellent life and high output power, produces less gas, and is highly safe even when overcharged, so it can be suitably widely used in fields requiring a large capacity. application.

Although the present invention and specific embodiments have been specifically described above, it is obvious for those skilled in the art that various changes can be made without departing from the intention and scope of the present invention. Also, this application is based on the following Japanese patent applications, all of which are incorporated by reference.

Japanese Patent Application No. 2005-331255 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-331362 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-331391 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-331477 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-331513 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-339794 (filing date: November 25, 2005)

Japanese Patent Application No. 2006-019863 (application date: January 27, 2006)

Japanese Patent Application No. 2006-005622 (filing date: January 13, 2005)

Japanese Patent Application No. 2005-367747 (filing date: December 21, 2005)

Japanese Patent Application No. 2005-377366 (filing date: December 28, 2005)

Japanese Patent Application No. 2005-349052 (filing date: December 2, 2005)

Japanese Patent Application No. 2005-359061 (filing date: December 13, 2005)

Japanese Patent Application No. 2006-019879 (application date: January 27, 2006)

Japanese Patent Application No. 2006-013664 (filing date: January 23, 2005)

Japanese Patent Application No. 2005-314043 (filing date: October 28, 2005)

Japanese Patent Application No. 2005-331585 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-305368 (filing date: October 20, 2005)

Japanese Patent Application No. 2005-344732 (filing date: November 29, 2005)

Japanese Patent Application No. 2005-343629 (filing date: November 29, 2005)

Japanese Patent Application No. 2005-332173 (filing date: November 16, 2005)

Japanese Patent Application No. 2005-305300 (application date: October 20, 2005)

Japanese Patent Application No. 2005-353005 (application date: December 7, 2005)

Japanese Patent Application No. 2005-314260 (filing date: October 28, 2005)

Japanese Patent Application No. 2005-369824 (filing date: December 22, 2005)

Japanese Patent Application No. 2005-370024 (filing date: December 22, 2005)

Description of drawings

[ Fig. 1 ] (a) is a cross-sectional scanning electron microscope (SEM) photograph of a thin film negative electrode (1) used in Examples 1 to 3 and Comparative Example 1 of the negative electrode [7]. (b) is a photograph showing the mass concentration distribution of element Si in the film thickness direction of the thin-film negative electrode (1) of the negative electrode [7] obtained by an electron probe microanalyzer (EPMA). (c) is a photograph showing the mass concentration distribution of element C in the film thickness direction of the thin-film negative electrode (1) of the negative electrode [7] obtained by an electron probe microanalyzer (EPMA).

Claims (46)

1. A lithium secondary battery, the lithium secondary battery at least comprising: an electrode group formed by sandwiching a microporous film separator between positive and negative electrodes, and a nonaqueous electrolytic solution formed by containing lithium salt in a nonaqueous solvent liquid, and they are housed in the battery case, wherein, The positive electrode and the negative electrode respectively form an active material layer on the current collector, and the active material layer contains an active material capable of absorbing and releasing lithium ions; The non-aqueous electrolyte contains at least one compound selected from the following substances, and its content in all non-aqueous electrolytes is more than 10ppm, and the substances include: A cyclic siloxane compound represented by the following general formula (1),

In the general formula (1), ^R1 and ^R2 may be the same or different, and represent an organic group with 1 to 12 carbon atoms, and n represents an integer of 3 to 10, A fluorosilane compound represented by the following general formula (2), SiF _x R ³ _p R ⁴ _q R ⁵ _r (2) In the general formula (2), R ³ to R ⁵ may be the same or different, and represent an organic group with 1 to 12 carbon atoms, x represents an integer of 1 to 3, and p, q and r represent an integer of 0 to 3, respectively , and 1≤p+q+r≤3, A compound represented by the following general formula (3), In the general formula (3), R ⁶ to R ⁸ may be the same or different, and represent an organic group with 1 to 12 carbon atoms, and A represents an organic group composed of H, C, N, O, F, S, Si and/or P constitute the group, and Compounds with S-F bonds in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates and propionates; And, the positive electrode is any positive electrode selected from the following positive electrode [1] to positive electrode [5]: Positive electrode [1]: a positive electrode comprising a positive electrode active material containing manganese; Positive electrode [2]: a positive electrode comprising a positive electrode active material having a composition represented by the following composition formula (4), Li _x Ni _(1-yz) Co _y M _z O ₂ composition formula (4) In the composition formula (4), M represents at least one element selected from Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, x represents a number satisfying 0<x≤1.2, and y represents A number satisfying 0.05≤y≤0.5, z means a number satisfying 0.01≤z≤0.5; Positive electrode [3]: a positive electrode comprising any positive electrode active material selected from the following (a) to (d), (a) A positive electrode active material having a BET specific surface area of 0.4m ² /g to 2m ² /g (b) Positive active material having an average primary particle size of 0.1 μm to 2 μm (c) A positive electrode active material having a median diameter _d50 of 1 μm to 20 μm (d) a positive electrode active material with a tap density of 1.3g/cm ³ to 2.7g/cm ³ ; Positive electrode [4]: a positive electrode that satisfies any one of the following conditions (e) to (g), (e) A positive electrode made by forming a positive electrode active material layer containing a positive electrode active material, a conductive material and a binder on a current collector, wherein the content of the conductive material in the positive electrode active material layer is 6% by mass to 20% by mass range (f) A positive electrode produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector, wherein the density of the positive electrode active material layer is in the range of 1.7 g/cm ³ to 3.5 g/cm ³ (g) a positive electrode made by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on the current collector, wherein the ratio of the thickness of the positive electrode active material layer to the current collector (one period before injecting the nonaqueous electrolyte solution) The thickness of the side active material layer)/(the thickness of the current collector) is in the range of 1.6 to 20; Positive electrode [5]: A positive electrode containing two or more positive electrode active materials with different compositions. 2. The lithium secondary battery according to claim 1, wherein the non-aqueous electrolytic solution contains at least one compound selected from the following substances, and its content is 0.01% by mass to 5% by mass, and the substances include: Cyclic siloxane compound represented by general formula (1), fluorosilane compound represented by general formula (2), compound represented by general formula (3), compound having S-F bond in the molecule, nitrate, nitrite, mono Fluorophosphates, difluorophosphates, acetates and propionates. 3. The lithium secondary battery according to claim 1, wherein the positive electrode active material containing manganese contained in the positive electrode [1] has a composition represented by the following composition formula (5), Li _x Mn _(1-y) M ¹ _y O ₂ composition formula (5) In the composition formula (5), M represents at ^least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents a number satisfying 0<x≤1.2 , y represents a number satisfying 0.05≤y≤0.8. 4. The lithium secondary battery according to claim 1, wherein the positive electrode active material containing manganese contained in the positive electrode [1] has a composition represented by the following composition formula (6), Li _x Mn _(1-yz) Ni _y M ² _z O ₂ composition formula (6) In the composition formula (6), M represents at ^least one element selected from Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, x represents a number satisfying 0<x≤1.2, and y represents a number satisfying 0.05≤y≤0.8, and z represents a number satisfying 0.01≤y≤0.5. 5. The lithium secondary battery according to claim 1, wherein the positive electrode active material containing manganese contained in the positive electrode [1] has a composition represented by the following composition formula (7), Li _x Mn _(2-y) M ³ _y O ₄ composition formula (7) In the composition formula (7), M represents at ^least one element selected from Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb, and x represents a number satisfying 0<x≤1.2 , y represents a number satisfying 0.05≤y≤0.8. 6 . The lithium secondary battery according to claim 1 , wherein the positive electrode active material containing manganese contained in the positive electrode [1] has a BET specific surface area of 0.4 m ² /g to 2 m ² /g. 7. The lithium secondary battery according to claim 1, wherein the positive electrode active material containing manganese contained in the positive electrode [1] has an average primary particle size of 0.1 μm to 2 μm. 8 . The lithium secondary battery according to claim 1 , wherein the median diameter d ₅₀ of the positive electrode active material containing manganese contained in the positive electrode [1] is 1 μm to 20 μm. 9 . The lithium secondary battery according to claim 1 , wherein the tap density of the positive electrode active material containing manganese contained in the positive electrode [1] is 1.3 g/cm ³ to 2.7 g/cm ³ . 10. The lithium secondary battery according to claim 1, wherein the positive electrode active material containing manganese contained in the positive electrode [1] has a substance having a composition different from that of the positive electrode active material containing manganese adhered to its surface. 11. The lithium secondary battery according to claim 1, wherein the positive electrode active material containing manganese contained in the positive electrode [1] is a mixture of two or more positive electrode active materials having different median particle sizes. 12. The lithium secondary battery according to claim 1, wherein the positive electrode [1] contains the positive electrode active material containing manganese and a positive electrode active material having a different composition from the positive electrode active material containing manganese. 13. The lithium secondary battery according to claim 1, wherein the positive electrode [1] is a positive electrode obtained by forming a positive electrode active material layer containing the positive electrode active material containing manganese and a binder on a collector , and the content of the positive electrode active material in the positive electrode active material layer is in the range of 80% by mass to 95% by mass. 14. The lithium secondary battery according to claim 1, wherein the positive electrode [1] is a positive electrode obtained by forming a positive electrode active material layer containing the positive electrode active material containing manganese and a binder on a collector , and the density of the positive electrode active material layer is in the range of 1.5 g/cm ³ to 3.5 g/cm ³ . 15. The lithium secondary battery according to claim 1, wherein the positive electrode [1] is a positive electrode obtained by forming a positive electrode active material layer containing the positive electrode active material containing manganese and a binder on a collector , and the ratio of the thickness of the current collector to the positive electrode active material layer (thickness of the active material layer on one side before injection of the nonaqueous electrolyte solution)/(thickness of the current collector) is in the range of 0.5 to 20. 16. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [2] has a substance having a composition different from that of the positive electrode active material of the core adhered to its surface. 17. The lithium secondary battery according to claim 1, wherein the tap density of the positive electrode active material contained in the positive electrode [2] is 1.3 g/cm ³ to 2.7 g/cm ³ . 18. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [2] has a median diameter _d50 of 1 μm to 20 μm. 19. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [2] is a mixture of two or more positive electrode active materials having different median diameters. 20. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [2] has an average primary particle diameter of 0.1 μm to 2 μm. 21. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [2] has a BET specific surface area of 0.4 m ² /g to 2 m ² /g. 22. The lithium secondary battery according to claim 1, wherein the positive electrode [2] contains the positive electrode active material and a positive electrode active material having a different composition from the positive electrode active material. 23. The lithium secondary battery according to claim 1, wherein the positive electrode [2] is a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on a current collector, and the positive electrode active material The content of the positive electrode active material in the layer is in the range of 80% by mass to 95% by mass. 24. The lithium secondary battery according to claim 1, wherein the positive electrode [2] is a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on a current collector, and the positive electrode active material The density of the layer is in the range of 1.5 g/cm ³ to 3.5 g/cm ³ . 25. The lithium secondary battery according to claim 1, wherein the positive electrode [2] is a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on a current collector, and (injecting non- The value of the thickness of the active material layer on the side before the aqueous electrolyte solution)/(thickness of the current collector) is in the range of 0.5 to 20. 26. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [3] has a substance having a composition different from that of the positive electrode active material of the core adhered to its surface. 27. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [3] is a mixture of two or more positive electrode active materials having different median particle sizes. 28. The lithium secondary battery according to claim 1, wherein the positive electrode [3] contains the positive electrode active material and a positive electrode active material having a composition different from the positive electrode active material. 29. The lithium secondary battery according to claim 1, wherein the positive electrode [3] is a positive electrode obtained by forming a positive electrode active material layer containing the positive electrode active material and a binding agent on a collector, and the positive electrode The content of the positive electrode active material in the active material layer is in the range of 80% by mass to 95% by mass. 30. The lithium secondary battery according to claim 1, wherein the positive electrode [3] is a positive electrode obtained by forming a positive electrode active material layer containing the positive electrode active material and a binding agent on a collector, and the positive electrode The density of the active material layer is in the range of 1.5 g/cm ³ to 3.5 g/cm ³ . 31. The lithium secondary battery according to claim 1, wherein the positive pole [3] is a positive pole obtained by forming a positive pole active material layer containing the positive pole active material and a binding agent on a collector, and ( The value of the thickness of the active material layer on one side before injection of the nonaqueous electrolyte solution)/(thickness of the current collector) is in the range of 0.5 to 20. 32. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [4] has a BET specific surface area of 0.4 m ² /g to 2 m ² /g. 33. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [4] has an average primary particle diameter of 0.1 μm to 2 μm. 34. The lithium secondary battery according to claim 1, wherein the median diameter _d50 of the positive electrode active material contained in the positive electrode [4] is 1 μm to 20 μm. 35. The lithium secondary battery according to claim 1, wherein the tap density of the positive electrode active material contained in the positive electrode [4] is 1.3 g/cm ³ to 2.7 g/cm ³ . 36. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [4] has a substance having a composition different from that of the positive electrode active material of the core adhered to its surface. 37. The lithium secondary battery according to claim 1, wherein the positive electrode active material contained in the positive electrode [4] is a mixture of two or more positive electrode active materials having different median particle sizes. 38. The lithium secondary battery according to claim 1, wherein the positive electrode [4] contains the positive electrode active material and a positive electrode active material having a different composition from the positive electrode active material. 39. The lithium secondary battery according to claim 1, wherein the BET specific surface area of at least one positive electrode active material contained in the positive electrode [5] is 0.4 m ² /g to 2 m ² /g . 40. The lithium secondary battery according to claim 1, wherein at least one positive electrode active material contained in the positive electrode [5] has an average primary particle diameter of 0.1 μm to 2 μm. 41. The lithium secondary battery according to claim 1, wherein at least one positive electrode active material contained in the positive electrode [5] has a median diameter _d50 of 1 μm to 20 μm. 42. The lithium secondary battery according to claim 1, wherein the tap density of at least one positive electrode active material contained in the positive electrode [5] is 1.3 g/cm ³ to 2.7 g/cm ³ . 43. The lithium secondary battery according to claim 1, wherein at least one of the positive active materials contained in the positive electrode [5] has a material different in composition from the positive active material of the core attached to its surface. . 44. The lithium secondary battery according to claim 1, wherein the positive electrode [5] is a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on a current collector, and the positive electrode active material The content of the positive electrode active material in the layer is in the range of 80% by mass to 95% by mass. 45. The lithium secondary battery according to claim 1, wherein the positive electrode [5] is a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on a current collector, and the positive electrode active material The density of the layer is in the range of 1.5 g/cm ³ to 3.5 g/cm ³ . 46. The lithium secondary battery according to claim 1, wherein the positive electrode [5] is a positive electrode obtained by forming a positive electrode active material layer containing a positive electrode active material and a binding agent on a current collector, and the positive electrode active material The ratio of the thickness of the layer to the current collector (thickness of the active material layer on one side before injection of the nonaqueous electrolyte solution)/(thickness of the current collector) is in the range of 0.5 to 20.

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