JP2013191458A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

The present invention provides a non-aqueous electrolyte secondary battery having high cycle characteristics.
SOLUTION: A positive electrode 10 having Li that moves between a positive electrode 10 and a negative electrode 20 to exchange electrons, and Li and SiO _x that moves between a positive electrode 10 and a negative electrode 20 to exchange electrons. The negative electrode 20 having 0 ≦ x <2) is incorporated. The positive electrode 10 preferably contains a positive electrode active material (A) having Li that moves between the positive electrode 10 and the negative electrode 20 to exchange electrons, and the positive electrode 10 includes the positive electrode active material ( A positive electrode active material (B) other than A) may be included, and the positive electrode active material (A) is one or more selected from lithium iron phosphate compounds, lithium cobalt oxides, and lithium nickel oxides. In addition, the positive electrode active material (B) is preferably at least one selected from spinel type lithium manganese oxide, molybdenum oxide and vanadium oxide.
[Selection] Figure 1

Description

 The present invention relates to a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries are attracting attention as a power source for electronic devices because of their high energy density and light weight. In particular, button-type non-aqueous electrolyte secondary batteries are small in size and are therefore portable electronic devices such as mobile phones. Widely used including backup applications.
The discharge capacity of the nonaqueous electrolyte secondary battery gradually decreases when charging and discharging are repeated. The nonaqueous electrolyte secondary battery may be heated to 50 ° C. or more by heat generated from the electronic device, and when charge and discharge are repeated under such a high temperature condition, the capacity is likely to decrease more rapidly. is there. For this reason, a nonaqueous electrolyte secondary battery is required that has a low discharge capacity (high cycle characteristics) even when charging and discharging are repeated.
For example, using _Li 4 _Mn 5 _{O 12} as the positive electrode active material, one using a SiO is known as an anode active material (e.g., Patent Document 1). According to the invention of Patent Document 1, the cycle characteristics are improved by combining a specific positive electrode active material and a specific negative electrode active material.

JP 2004-327282 A

However, further improvement in cycle characteristics is required for nonaqueous electrolyte secondary batteries.
Accordingly, the present invention is directed to a non-aqueous electrolyte secondary battery having high cycle characteristics.

A conventional non-aqueous electrolyte secondary battery has Li (hereinafter sometimes referred to as reversible Li) that transfers electrons between the positive electrode and the negative electrode only in the positive electrode or the negative electrode. For example, in a button-type (coin-type) non-aqueous electrolyte secondary battery, Li is occluded in a negative electrode, and electrons are transferred between the positive electrode and the negative electrode by movement of the occluded Li. Usually, a part of Li occluded in the negative electrode moves between the positive electrode and the negative electrode as a reversible capacity, and the other part is held in the negative electrode as an irreversible capacity. For this reason, it has been attempted to ensure the necessary amount of Li for the reversible capacity by storing the amount of Li with the irreversible capacity added to the negative electrode.
Reversible Li is consumed and reduced by generating a reaction product (organic matter, fluoride, hydroxide, etc.) with the electrolyte solution on the electrode surface during repeated charge and discharge, and is generated by the previous reaction product. The film (hereinafter sometimes referred to as SEI) increases the charge resistance of lithium ions, increases the overvoltage during charging and discharging, and decreases the battery function. Here, although the capacity of the negative electrode is made larger than the capacity of the positive electrode and a large amount of Li is occluded in the negative electrode, the cycle characteristics can be improved. However, in the small button type non-aqueous electrolyte secondary battery, the entire battery Since the ratio of the volume of the negative electrode occupying is limited, there is a limit to improving the cycle characteristics by increasing the volume ratio of the negative electrode.
As a result of intensive studies, the present inventors have found that the cycle characteristics of the nonaqueous electrolyte secondary battery can be improved by incorporating reversible Li in each of the positive electrode and the negative electrode in advance, leading to the present invention. It was.

That is, the non-aqueous electrolyte secondary battery of the present invention includes a positive electrode having Li that moves between the positive electrode and the negative electrode to transfer electrons, and a Li that moves between the positive electrode and the negative electrode to transfer electrons. And a negative electrode having SiO _x (0 ≦ x <2).
The positive electrode preferably contains a positive electrode active material (A) having Li that moves between the positive electrode and the negative electrode to exchange electrons, and the positive electrode is a material other than the positive electrode active material (A). The positive electrode active material (B) may be included, and the positive electrode active material (A) is at least one selected from a lithium iron phosphate compound, a lithium cobalt oxide, and a lithium nickel oxide, The active material (B) is preferably at least one selected from spinel type lithium manganese oxide, molybdenum oxide and vanadium oxide.

  According to the nonaqueous electrolyte secondary battery of the present invention, the cycle characteristics can be improved.

It is sectional drawing of the nonaqueous electrolyte secondary battery concerning one Embodiment of this invention.

The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode having Li that moves between the positive electrode and the negative electrode to transfer electrons, and Li and SiO that moves between the positive electrode and the negative electrode to transfer electrons. and a negative electrode having _x (0 ≦ x <2).
An embodiment of the nonaqueous electrolyte secondary battery of the present invention will be described with reference to FIG. The nonaqueous electrolyte secondary battery 1 has a so-called coin-type structure.
A non-aqueous electrolyte secondary battery 1 in FIG. 1 includes a bottomed cylindrical main body (positive electrode can) 12, a covered cylindrical lid (negative electrode can) 22 that closes the opening of the positive electrode can 12, and a positive electrode can 12. The container 40 is provided with a gasket 40 provided along the inner peripheral surface thereof, and the opening peripheral edge of the positive electrode can 12 is caulked inward.
In the nonaqueous electrolyte secondary battery 1, a positive electrode 10 and a negative electrode 20 are disposed opposite to each other with a separator 30 in a storage container 2 and filled with an electrolytic solution 50. The positive electrode 10 is electrically connected to the inner surface of the positive electrode can 12 via the positive electrode current collector 14, and the negative electrode 20 is electrically connected to the inner surface of the negative electrode can 22 via the negative electrode current collector 24. The positive electrode 10, the negative electrode 20, and the separator 30 are impregnated with the electrolytic solution 50 filled in the storage container 2.

As the material of the positive electrode can 12, conventionally known materials are used, and examples thereof include stainless steel.
The material of the negative electrode can 22 is the same as that of the positive electrode can 12.

As the positive electrode 10, one having reversible Li is used.
The reversible Li is not particularly limited as long as it can move between the positive electrode 10 and the negative electrode 20 to exchange electrons. For example, the reversible Li is added to the positive electrode 10 as a positive electrode active material (A) having reversible Li. The
As the positive electrode active material (A), LiFe _1-p M ⁴ _p PO ₄ (0 ≦ p ≦ 1, M ⁴ is at least one of Mn, Ni, Co, Ti, Al, Cr, V, and Nb) Li ₃ Fe _{2 -q} M ⁵ _q (PO ₄ ) ₃ (0 ≦ q ≦ 1, M ⁵ is the same as M ⁴ ), etc., lithium iron phosphate compounds, LiCo _1-r M ⁶ _r O ₂ ( 0 ≦ r <1, ^{M 6} is Mn, Ti, Fe, Cr, Al, Mo, V, Cu, Nb, Zn, Ca, at least one) of lithium cobalt oxide such as of Mg, LiNi _1-s Lithium such as M ⁷ _s O ₂ (0 ≦ s <1, M ⁷ is Mn, Co, Ti, Fe, Cr, Al, Mo, V, Cu, Nb, Zn, Ca, Mg) Nickel oxide, LiCo _1-t M ⁸ _t PO ₄ (0 ≦ t <1, M ⁸ is the same as M ⁶ And lithium nickel phosphate compounds such as LiNi _1-u M ⁹ _u PO ₄ (0 ≦ u <1, M ⁹ is the same as M ⁷ ).

 The average particle diameter (D50) of the positive electrode active material (A) is not particularly limited. For example, in the case of lithium cobalt oxide or lithium nickel oxide, 0.1 to 100 μm is preferable, and 1 to 10 μm is more preferable. . Moreover, in a lithium iron phosphate compound, 0.001-1 micrometer is preferable and 0.01-0.1 micrometer is more preferable. This is because if it is less than the above lower limit value, it is difficult to mix with the positive electrode active material (B) described later, and if it exceeds the above upper limit value, the discharge rate decreases. In addition, an average particle diameter (D50) is a mass average particle diameter measured using a laser diffraction method.

 The content of the positive electrode active material (A) in the positive electrode 10 can be determined in consideration of the type of the positive electrode active material (A) and the like, for example, preferably 10 to 76% by mass, and more preferably 28 to 53% by mass. If it is more than the said lower limit, cycling characteristics can be improved more, and if it is below the said upper limit, the positive electrode 10 will be easy to shape | mold.

The positive electrode 10 may contain a positive electrode active material (B) other than the positive electrode active material (A).
As the positive electrode active material (B), for example, Li ₄ Mn _5-w M ¹ _w O ₁₂ (0 ≦ w <1, M ¹ is Ni, Co, Ti, Fe, Cr, Al, Mo, V, Cu, Nb, Zn, Ca, Mg), LiMn _2-y M ² _y O ₄ (0 ≦ y <1, M ² is the same as M ¹ ), Li ₂ Mn _4-z M ³ spinel lithium manganese oxide such as _z O ₉ (0 ≦ z <1, M ³ is the same as M ¹ ), molybdenum oxide such as MoO ₃ and MoO ₂ , V ₂ O ₅ , V ₃ O ₈ , Examples thereof include vanadium oxides such as V ₆ O ₁₃ . By containing these positive electrode active materials (B), the discharge capacity of the nonaqueous electrolyte secondary battery 1 can be increased.
A positive electrode active material (B) may be used individually by 1 type, and may be used in combination of 2 or more type.

The combination of the positive electrode active material (A) and the positive electrode active material (B) is determined in consideration of the voltage value of the nonaqueous electrolyte secondary battery 1 and the like.
For example, when the nonaqueous electrolyte secondary battery 1 has a voltage value of 4 V or more and less than 5 V (4 V secondary battery), the positive electrode active material (A) is included and the positive electrode active material (B) is not included. a positive electrode active material (a), configured like a combination of a positive electrode active material (B) excluding the LiMn ₂ O ₄ are preferred.
For example, when the non-aqueous electrolyte secondary battery 1 has a voltage value of 3 V or more and less than 4 V (3 V secondary battery), the positive electrode active material (A) and the positive electrode active material (B) are combined. Is preferred.

 Although the average particle diameter of a positive electrode active material (B) is not specifically limited, For example, 0.1-100 micrometers is preferable and 10-50 micrometers is more preferable. If it is less than the above lower limit value, the reactivity with the electrolytic solution is increased, which is difficult to handle, and if it exceeds the above upper limit value, the discharge rate decreases.

 The content of the positive electrode active material (B) in the positive electrode 10 is determined in consideration of the discharge capacity and the like required for the nonaqueous electrolyte secondary battery 1, and is preferably 10 to 76% by mass, for example, 28 to 53% by mass. More preferred. If it is more than the said lower limit, discharge capacity can be raised more, and if it is below the said upper limit, the positive electrode 10 will be easy to shape | mold.

The mass ratio represented by the positive electrode active material (A) / the positive electrode active material (B) (hereinafter sometimes referred to as A / B ratio) is determined in consideration of the voltage value of the nonaqueous electrolyte secondary battery 1 and the like. The If the A / B ratio is too low, the cycle characteristics may not be sufficiently improved. If the A / B ratio is too high, a desired voltage value cannot be obtained, or the positive electrode active material (A) is precipitated by overcharging. As a result, the non-aqueous electrolyte secondary battery 1 may overheat.
For this reason, for example, in the case of a 3V secondary battery, the A / B ratio is preferably 2/8 to 8/2, more preferably 3/7 to 7/3, and further preferably 4/6 to 6/4. preferable.

 The total amount of the positive electrode active material (A) and the positive electrode active material (B) in the positive electrode 10 is determined in consideration of the discharge capacity and the like required for the nonaqueous electrolyte secondary battery 1, and is, for example, 50 to 95% by mass. Preferably, 70 to 88% by mass is more preferable. If it is less than the above lower limit value, it is difficult to obtain a sufficient discharge capacity, and if it exceeds the above upper limit value, it tends to be difficult to form the positive electrode 10.

The positive electrode 10 may contain a conductive additive (the conductive additive used for the positive electrode 10 may be referred to as a positive conductive additive). Examples of the positive electrode conductive assistant include carbon materials such as furnace black, ketjen black, acetylene black, and graphite. These positive electrode conductive aids may be used alone or in combination of two or more.
4-40 mass% is preferable, for example, and, as for content of the positive electrode conductive support agent in the positive electrode 10, 10-25 mass% is more preferable. If it is less than the lower limit, it is difficult to obtain sufficient conductivity, and it is difficult to form the positive electrode 10 in the form of a pellet, and if it exceeds the upper limit, the discharge capacity of the positive electrode 10 may be insufficient.

The positive electrode 10 may contain a binder (the binder used for the positive electrode 10 may be referred to as a positive electrode binder). As the positive electrode binder, conventionally known materials can be used. For example, polymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyacrylic acid (PA), carboxy, etc. Examples thereof include methyl cellulose (CMC) and polyvinyl alcohol (PVA). Among them, polyacrylic acid is preferable, and cross-linked polyacrylic acid is more preferable. These positive electrode binders may be used alone or in combination of two or more. In addition, when using polyacrylic acid, it is preferable to adjust polyacrylic acid to pH 3-10 previously. For adjusting the pH, an alkali metal hydroxide such as lithium hydroxide or an alkaline earth metal hydroxide such as magnesium hydroxide can be used.
The content of the positive electrode binder in the positive electrode 10 is, for example, 1 to 20% by mass.

The size of the positive electrode 10 is determined according to the size of the nonaqueous electrolyte secondary battery 1.
The thickness of the positive electrode 10 is determined according to the size of the non-aqueous electrolyte secondary battery 1, and if the non-aqueous electrolyte secondary battery 1 is a button-type non-aqueous electrolyte secondary battery for backup, 300 to 1000 μm.

The positive electrode 10 is obtained by a conventionally known manufacturing method. The method for producing the positive electrode 10 includes, for example, a positive electrode active material (A) and, if necessary, at least one selected from a positive electrode active material (B), a positive electrode conductive additive, and a positive electrode binder to form a positive electrode mixture. And a method of pressure-molding the positive electrode mixture into an arbitrary shape.
The pressure at the time of pressure molding is determined in consideration of the type of the positive electrode conductive additive, and is, for example, 0.2 to 5 ton / cm ² .

 A conventionally well-known thing is used as the positive electrode electrical power collector 14, For example, the conductive resin adhesive etc. which use carbon as a conductive filler are mentioned.

As the negative electrode 20, a material containing reversible Li is used, and for example, a negative electrode pellet containing a negative electrode active material and the like, in which metallic lithium as reversible Li is occluded, can be mentioned.
The content of reversible Li in the negative electrode 20 is determined in consideration of the discharge capacity of the nonaqueous electrolyte secondary battery 1. For example, in the negative electrode 20, the theoretical reversible capacity (hereinafter referred to as theoretical capacity) of the negative electrode active material. 5) to 100% is preferable, and an amount of 20 to 100% is more preferable (the content of reversible Li relative to the theoretical capacity of the negative electrode active material in the negative electrode may be referred to as negative electrode reversible Li amount) . When the negative electrode active material is SiO _x (x = 1), 4 mol of Li is occluded with respect to 1 mol of SiO _x (x = 1), but 2 mol of Li is trapped by the negative electrode active material. Thus, the reversible Li content is 2 mol. For this reason, if 2.1-4 mol of Li is occluded with respect to 1 mol of SiO _x (x = 1), the negative electrode reversible Li amount becomes 5 to 100%, and with respect to 1 mol of SiO _x (x = 1). If 2.4 to 4 mol of Li is occluded, the amount of negative electrode reversible Li becomes 20 to 100%. If the amount of negative electrode reversible Li is less than the above lower limit value, the cycle characteristics may not be sufficiently improved. If the amount exceeds the upper limit value, Li metal tends to precipitate on the surface of the negative electrode 20 with the cycle, and the nonaqueous electrolyte The stability of the secondary battery 1 may be reduced.

 The total amount (reversible Li total amount) of reversible Li in the positive electrode 10 incorporated in the nonaqueous electrolyte secondary battery 1 and reversible Li in the negative electrode 20 incorporated in the nonaqueous electrolyte secondary battery 1 is the theoretical capacity of the positive electrode 10. And the theoretical capacity of the negative electrode 20 is 100, preferably more than 50 and less than 100, more preferably 60 to 70 (ratio of total reversible Li to 100 total of the theoretical capacity of the positive electrode 10 and the theoretical capacity of the negative electrode 20) May be referred to as a reversible Li content ratio). If the reversible Li content ratio is less than or equal to the above lower limit value, the cycle characteristics may not be sufficiently improved, and if the reversible Li content ratio exceeds the above upper limit value, Li metal tends to precipitate on the surface of the negative electrode 20 along with the cycle. The stability of the nonaqueous electrolyte secondary battery 1 may be reduced.

As a negative electrode pellet, for example, a material containing SiO _x (0 ≦ x <2) as a negative electrode active material, and a material containing SiO _x (x = 1) are preferable. By including such a negative electrode active material, the cycle characteristics of the nonaqueous electrolyte secondary battery 1 can be further increased, and the discharge capacity can be further increased. Note that SiO _x (0 ≦ x <2) may be used in an amorphous state that shows broad in an X-ray diffraction pattern, but was previously disproportionated by subjecting SiO _x (0 ≦ x <2) to heat treatment. It may be used in a state.

The negative electrode pellet can contain a negative electrode active material (optional negative electrode active material) other than SiO _x (0 ≦ x <2). Examples of the optional negative electrode active material include SnO _v (0 ≦ v <1), C (graphite, hard carbon, etc.), Li ₄ Ti ₅ O ₁₂ , LiAl, and the like.

The total amount of _SiO x of the negative electrode pellet (0 ≦ x <2) and any negative electrode active material is not particularly limited, for example, are 40 to 85 mass%. The content of the negative electrode active material is mainly determined by the conductivity of the negative electrode active material. Even if the negative electrode active material has a low conductivity, the negative electrode active material has a higher conductivity by coating the surface with carbon, etc. The content ratio of the active material can be increased.
The content of SiO _x (0 ≦ x <2) in the negative electrode active material is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and may be 100% by mass. . This is because the content of reversible Li can be increased and the cycle characteristics can be further improved if the lower limit is exceeded.

The negative electrode pellet can contain a conductive additive (the conductive aid used for the negative electrode 20 may be referred to as a negative conductive additive). The negative electrode conductive auxiliary is the same as the positive electrode conductive auxiliary.
Content of the negative electrode conductive support agent in a negative electrode pellet shall be 4-40 mass%, for example.
The negative electrode pellet can contain a binder (the binder used for the negative electrode 20 may be referred to as a negative electrode binder). As the negative electrode binder, a conventionally known material can be used. For example, polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), polyimide (PI), polyamideimide (PAI) and the like can be mentioned. Among them, polyacrylic acid is preferable, and cross-linked polyacrylic acid is more preferable. These negative electrode binders may be used individually by 1 type, and may be used in combination of 2 or more type. In addition, when using polyacrylic acid, it is preferable to adjust polyacrylic acid to pH 3-10 previously. For adjusting the pH, an alkali metal hydroxide such as lithium hydroxide or an alkaline earth metal hydroxide such as magnesium hydroxide can be used.
The content of the negative electrode binder in the negative electrode pellet is, for example, 1 to 20% by mass.

The size of the negative electrode 20 is determined in consideration of the type of the negative electrode active material, the size of the non-aqueous electrolyte secondary battery 1, the size of the positive electrode 10, and the like. The size of the negative electrode 20 is preferably designed so that the capacity of the negative electrode 20 is larger than the capacity of the positive electrode 10.
The negative electrode / positive electrode capacity ratio represented by (theoretical capacity of the negative electrode 20) / (theoretical capacity of the positive electrode 10) is, for example, preferably 0.5 to 5, and more preferably 1 to 3. If the negative electrode / positive electrode capacity ratio is less than the lower limit, the cycle characteristics of the nonaqueous electrolyte secondary battery 1 may not be sufficiently improved. If the upper limit exceeds the upper limit, for example, the size of the positive electrode 10 is limited, The discharge capacity of the water electrolyte secondary battery 1 may be reduced.

 The negative electrode current collector 24 is the same as the positive electrode current collector 14.

As a manufacturing method of the negative electrode 20, the following method is mentioned, for example.
First, a negative electrode active material and, if necessary, a negative electrode conductive additive and / or a negative electrode binder are mixed to form a negative electrode mixture, and the negative electrode mixture is pressure-molded into an arbitrary shape to form a negative electrode pellet.
The pressure at the time of pressure molding is determined in consideration of the type of the negative electrode conductive auxiliary agent, and is, for example, 0.2 to 5 ton / cm ² .
Next, while pressing a molded product of Li such as lithium foil on the surface of the negative electrode pellet at an arbitrary pressure, the negative electrode pellet is allowed to stand at an arbitrary temperature to occlude Li in the negative electrode pellet. In this case, the amount of Li obtained by adding the amount of Li for the irreversible capacity of the negative electrode active material to the desired amount of reversible Li is occluded in the negative electrode pellet (intercalation of lithium ions into SiO _x (0 ≦ x <2) of the negative electrode active material). (Calation).
The pressure which presses the molding of Li against a negative electrode pellet is not specifically limited, For example, you may be 0.01-1 Mpa.
The temperature to stand still is not specifically limited, For example, it is 10-60 degreeC, Preferably it is 20-30 degreeC.
The time to stand still is time which can fully occlude Li in a negative electrode pellet, for example, is 5 to 7 days.
Moreover, as a manufacturing method of the negative electrode 20, the method of forming Li layer on the surface of a negative electrode pellet by sputtering etc., and leaving still at arbitrary temperature and occluding Li in a negative electrode pellet is mentioned.

The electrolytic solution 50 is obtained by dissolving a supporting salt in a non-aqueous solvent.
As the non-aqueous solvent, conventionally known solvents are used. For example, ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), Carbonates such as diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), γ-butyrolactone (GBL), sulfolane (SL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1 , 2-ethoxymethoxyethane (EME), tetrahydrofuran (THF), 1,3-dioxolane (DOL) and the like. These non-aqueous solvents may be used alone or in combination of two or more.

As the supporting salt, a known substance used as a supporting salt in the electrolyte solution of the nonaqueous electrolyte secondary battery can be used. For example, LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₃ ) ₂ , Organic acid lithium salts such as LiN (FSO ₂ ) ₂ , lithium salts such as LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, and other inorganic acid lithium salts can be used. Among these, lithium salts that are compounds having lithium ion conductivity are preferable, LiN (CF ₃ SO ₂ ) _2, LiN (FSO ₂ ) _{2, and} LiBF ₄ are more preferable, heat resistance and reactivity with moisture are low, and storage is performed. From the viewpoint of sufficiently exhibiting the characteristics, LiN (CF ₃ SO ₂ ) ₂ is particularly preferable. These supporting salts may be used singly or in combination of two or more.

  The content of the supporting salt in the electrolytic solution 50 can be determined in consideration of the type of the supporting salt and the like. For example, when a lithium salt is used, 0.5 to 3.5 mol / L is preferable, and 0.5 to 3. 0 mol / L is more preferable, and 1 to 2.5 mol / L is particularly preferable. If the lithium salt concentration is too high or too low, the electrical conductivity is lowered, which may adversely affect the battery characteristics.

 As the separator 30, those conventionally used for separators of non-aqueous electrolyte secondary batteries can be applied, for example, glass such as borosilicate glass, alkali glass, quartz glass, lead glass, polyphenylene sulfide (PPS), polyether ether ketone. Nonwoven fabric made of a resin such as (PEEK), polyethylene terephthalate (PET), polyamideimide (PAI), polyimide (PI), and the like. Among these, a glass nonwoven fabric is preferable, and a borosilicate glass nonwoven fabric is more preferable. Since the glass nonwoven fabric has excellent mechanical strength and high ion permeability, the internal resistance can be reduced and the discharge capacity can be improved.

 The thickness of the separator 30 is determined in consideration of the size of the nonaqueous electrolyte secondary battery 1, the material of the separator 30, and the like, and is, for example, 5 to 300 μm.

  The material of the gasket 40 is preferably a resin having a heat distortion temperature of 230 ° C. or higher. If the heat distortion temperature is 230 ° C. or higher, for example, reflow treatment can prevent the gasket 40 from being significantly deformed and the electrolyte solution 50 from leaking out. Examples of the material of the gasket 40 include polyphenyl sulfide (PPS), polyethylene terephthalate (PET), polyamide (PA), liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), and polyether. Ether ketone resin (PEEK), polyether nitrile resin (PEN), polyether ketone resin (PEK), polyarylate resin, polybutylene terephthalate resin (PBT), polycyclohexanedimethylene terephthalate resin, polyether sulfone resin (PES), Examples thereof include polyamino bismaleimide resin, polyetherimide resin, and fluororesin. Moreover, what added glass fiber, my cowsker, ceramic fine powder, etc. to these materials with the addition amount of 30 mass% or less can be used conveniently. By using such a material, deformation of the gasket 40 can be prevented in reflow soldering, and volatilization and leakage of the electrolytic solution 50 can be prevented.

According to the nonaqueous electrolyte secondary battery of the present embodiment, a positive electrode having reversible Li and a negative electrode containing SiO _x (0 ≦ x <2) as a negative electrode active material and having reversible Li are incorporated. Therefore, cycle characteristics can be improved.

 In the above-described embodiment, a coin-type nonaqueous electrolyte secondary battery including a storage container in which a stainless steel positive electrode can and a stainless steel negative electrode can are crimped has been described as an example. It is not limited. For example, the nonaqueous electrolyte secondary battery has a structure in which the opening of the ceramic container body is sealed with a ceramic lid by a heat treatment such as seam welding using a metal sealing member. Good.

 EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1-36, Comparative Examples 1-6)
According to the composition of the positive electrode active materials in Tables 1 to 4, the positive electrode active material (A) and the positive electrode active material (B) were mixed. According to the composition of the positive electrode in the table, 70 parts by mass of the positive electrode active material, 28 parts by mass of carbon as the positive electrode conductive auxiliary agent, and 2 parts by mass of cross-linked polyacrylic acid as the binder were mixed to obtain a positive electrode mixture. . 7 mg of this positive electrode mixture was pressure-molded at ² ton / cm ² to obtain a disk-type positive electrode having a diameter of 2 mm and a thickness of 600 μm.
45 parts by mass of pulverized SiO _x (x = 1), 40 parts by mass of carbon, and 15 parts by mass of cross-linked polyacrylic acid were mixed to obtain a negative electrode mixture. 1.0 mg of this negative electrode mixture was pressure-molded at ² ton / cm ² to obtain a disc-shaped negative electrode pellet having a diameter of 2.0 mm and a thickness of 200 μm.
30 parts by mass of ethylene carbonate, 35 parts by mass of propylene carbonate and 35 parts by mass of sulfolane are mixed to form a non-aqueous solvent, and the resulting non-aqueous solvent is mixed with ₂ supporting salts (LiN (CF ₃ SO ₂ ) ₂ ). An electrolytic solution was obtained by dissolving to 0.0 mol / L.

A positive electrode unit was obtained by adhering the positive electrode to the inner surface of a stainless steel positive electrode can using a positive electrode current collector made of a conductive resin adhesive containing carbon as a conductive filler. The positive electrode unit was dried in the air at 200 ° C. for 10 hours.
Subsequently, the sealing agent was apply | coated to the inner surface of the opening part of the positive electrode can of a positive electrode unit.
A negative electrode is bonded to the inner surface of a stainless steel negative electrode can using a negative electrode current collector made of a conductive resin adhesive containing carbon as a conductive filler, and the negative electrode reversible Li amount in the table is set on the negative electrode. Lithium foil was placed.
Next, the nonwoven fabric made from borosilicate glass fiber was dried, and then punched into a disk shape having a diameter of 3 mm and a thickness of 200 μm to obtain a separator. This separator was placed on the negative electrode, and a gasket was provided in the opening of the negative electrode can to obtain a negative electrode unit.
A total of 5 μL of electrolyte solution was filled in the positive electrode can and the negative electrode can.
The negative electrode unit was fitted into the positive electrode unit so that the lithium foil contacted the separator. Next, the positive electrode can and the negative electrode can were sealed by caulking the opening of the positive electrode can, and then allowed to stand at 25 ° C. for 7 days to obtain the nonaqueous electrolyte secondary battery of each example.
About the obtained nonaqueous electrolyte secondary battery, cycling characteristics were evaluated and the result is shown in a table | surface.
In order to set the negative electrode reversible Li amount to 100, 60, 30, 7, and 0, the thickness of the lithium foil (diameter 2 mm) placed on the negative electrode was 220 μm, 170 μm, 140 μm, 120 μm, and 110 μm, respectively.

(Evaluation method)
<Cycle characteristics>
Six nonaqueous electrolyte secondary batteries of each example immediately after production were discharged in a 24 ° C. environment at a constant current of 5 μA (discharge current) until 2.0 V was reached. Subsequently, it applied for 48 hours by the charging voltage value shown to Tables 1-4 in 24 degreeC environment. Thereafter, the battery was discharged at a constant current of 5 μA (discharge current) until it reached 2.0 V in a 24 ° C. environment, and the discharge capacity was calculated according to the following formula (i).

 Discharge capacity (μAh) = discharge current (5 μA) × discharge time (h) (i)

 For the nonaqueous electrolyte secondary battery whose initial discharge capacity was measured, after applying for 48 hours at the charging voltage values shown in Tables 1 to 4, until 2.0 V at a constant current of 5 μA (discharge current) in a 24 ° C. environment The operation of discharging (charging / discharging cycle) was repeated 100 times. The discharge capacity (post-cycle discharge capacity) in the 100th charge / discharge cycle was determined in the same manner as the initial discharge capacity, and the capacity retention rate was calculated by the following equation (ii). It can be said that the higher the capacity retention rate, the higher the cycle characteristics.

 Capacity maintenance ratio (%) = discharge capacity after cycle ÷ initial discharge capacity × 100 (ii)

Examples 1-27 and Comparative Examples 1-3 are examples of 3V secondary batteries, and Examples 28-36 and Comparative Examples 4-6 are examples of 4V secondary batteries.
As shown in Tables 1 to 4, the capacity retention rates of Examples 1 to 36 to which the present invention was applied were 83% or more.
On the other hand, the capacity maintenance rate of Comparative Examples 1 to 3 having no reversible Li in the positive electrode and having reversible Li only in the negative electrode, and Comparative Examples 4 to 4 having no reversible Li in the negative electrode and having reversible Li only in the positive electrode The capacity retention rate of 6 was 82% or less.
From this result, it was found that the cycle characteristics can be improved by applying the present invention.

In addition, in the 3V secondary battery, the capacity retention rate of Examples 1 to 27 was 87% or higher, while the capacity retention rate of Comparative Examples 1 to 3 was 78% or lower.
From this result, it was found that the effect of the present invention is remarkable in the 3V secondary battery.

1 Nonaqueous electrolyte secondary battery 10 Positive electrode 20 Negative electrode

Claims (4)

A positive electrode having Li that moves between the positive electrode and the negative electrode to transfer electrons, and a negative electrode having Li and SiO _x (0 ≦ x <2) that transfers between the positive electrode and the negative electrode to transfer electrons And non-aqueous electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode contains a positive electrode active material (A) having Li that moves between the positive electrode and the negative electrode to exchange electrons.   The non-aqueous electrolyte secondary battery according to claim 2, wherein the positive electrode has a positive electrode active material (B) other than the positive electrode active material (A). The positive electrode active material (A) is one or more selected from a lithium iron phosphate compound, a lithium cobalt oxide, and a lithium nickel oxide, and the positive electrode active material (B) is a spinel type lithium manganese oxide, The nonaqueous electrolyte secondary battery according to claim 3, which is at least one selected from molybdenum oxide and vanadium oxide.

Images