JP2007227367A - Lithium ion secondary battery - Google Patents

Abstract

【選択図】なしA lithium ion secondary battery having good cycle characteristics and low-temperature output is provided.
A non-aqueous electrolyte contains 10 ppm or more of (1) cyclic siloxane, (2) fluorosilane, (3) compound, SF-bonded compound, nitrate, etc. A lithium ion secondary battery containing two or more types of negative electrode active materials having different properties.

[Selection figure] None

Description

  The present invention relates to a lithium ion secondary battery, and more particularly, to a lithium ion secondary battery using a specific non-aqueous electrolyte and a specific negative electrode active material.

  In the field of information-related equipment and communication equipment, along with the downsizing of personal computers, video cameras, mobile phones, etc., lithium-ion secondary batteries have been put to practical use because of their high energy density as the power source used for these equipment. It has become widespread.

  In recent years, in addition to the above fields, in the field of automobiles, lithium ion secondary batteries have been developed mainly for use as power sources for electric vehicles, which are urgently developed against the background of environmental and resource problems. Is being considered.

  Among lithium secondary batteries, secondary batteries using metal lithium as a negative electrode have been actively studied since long ago as batteries capable of achieving high capacity. However, these batteries have a problem that metallic lithium grows in a dendrite shape by repeated charging and discharging, eventually reaches the positive electrode, and a short circuit occurs inside the battery, and this problem is a metallic lithium secondary battery. Has become the biggest technical challenge when putting to practical use.

  Therefore, a nonaqueous electrolyte secondary battery using a carbonaceous material capable of occluding and releasing lithium ions such as coke, artificial graphite, and natural graphite has been proposed for the negative electrode. In such a non-aqueous electrolyte secondary battery, since lithium does not exist in a metal state, formation of dendrites is suppressed, and battery life and safety can be improved. In particular, graphite-based carbonaceous materials such as artificial graphite and natural graphite are expected as materials capable of improving the energy density per unit volume.

  However, lithium primary batteries are generally preferred as non-aqueous electrolyte secondary batteries using various graphite-based electrode materials alone or mixed with other negative electrode materials capable of occluding and releasing lithium as negative electrodes. When a non-aqueous electrolyte containing propylene carbonate used as a main solvent is used, the decomposition reaction of the solvent proceeds vigorously on the surface of the graphite electrode, making it impossible to smoothly occlude and release lithium into the graphite electrode. On the other hand, ethylene carbonate is often used as the main solvent of the electrolyte of non-aqueous electrolyte secondary batteries because of such a small amount of decomposition. However, even when ethylene carbonate is used as the main solvent, the surface of the electrode is charged and discharged. There is a problem in that charge / discharge efficiency and cycle characteristics are degraded due to decomposition of the electrolytic solution.

  Furthermore, when using a lithium ion secondary battery as a power source for an electric vehicle, it is necessary to exhibit a balanced performance such as long-term repeated use, input / output characteristics, storage characteristics when stored at high temperature, etc. .

  Thus, as a means for improving the characteristics of the lithium ion secondary battery in a well-balanced manner, many techniques have been studied for various battery components including positive and negative active materials.

  As a technique relating to the negative electrode active material, in Patent Document 1, when the particle size ratio and the mixing ratio of the large diameter powder and the small diameter powder are within a certain range, the packing density is particularly high and the electrode capacity is increased. Although the large-diameter powder is spherical, there is a description that even if the small-diameter powder is not a spherical powder, an irregularly shaped powder such as a pulverized powder can achieve a particularly large improvement in utilization. However, even with this method, the balance between the long-term cycle characteristics and the low-temperature output was not sufficiently satisfactory.

  As a technique related to the non-aqueous electrolyte solution, Patent Document 2 discloses that in a non-aqueous electrolyte secondary battery, when lithium monofluorophosphate or lithium difluorophosphate is added to the non-aqueous electrolyte solution, a good film is formed at the electrode interface. As a result, it is described that the decomposition of the electrolytic solution is suppressed and a battery having improved storage characteristics can be obtained.

However, even with this method, the balance between long-term cycle characteristics and low-temperature output cannot be said to be sufficient.
Japanese Patent Laid-Open No. 11-031509 Japanese Patent Application Laid-Open No. 11-067270

  This invention is made | formed in view of this background art, The subject is to provide the lithium ion secondary battery with which both cycling characteristics and a low-temperature output are favorable.

  As a result of diligent research in view of the above problems, the present inventor has found it important to dispose a negative electrode active material having a good balance between the functions in the negative electrode for performance with good cycle characteristics and low-temperature output. It was considered that it was better to mix negative electrode active materials having several different physical properties. Furthermore, the present invention was completed by finding out that both the cycle characteristics and the low-temperature output were improved by containing a specific compound in the non-aqueous electrolyte at the same time.

［一般式（１）中、Ｒ^１及びＲ^２は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ｎは３〜１０の整数を表す。］

［一般式（２）中、Ｒ^３〜Ｒ^５は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ｘは１〜３の整数を表し、ｐ、ｑ及びｒはそれぞれ０〜３の整数を表し、１≦ｐ＋ｑ＋ｒ≦３である。］

［一般式（３）中、Ｒ^６〜Ｒ^８は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ＡはＨ、Ｃ、Ｎ、Ｏ、Ｆ、Ｓ、Ｓｉ及び／又はＰから構成される基を表す。］ That is, the present invention is a lithium ion secondary battery having at least a non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt, a positive electrode active material, and a negative electrode active material, wherein the non-aqueous electrolyte solution has a general formula (1 ), A fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), a compound having an SF bond in the molecule, nitrate, nitrite, mono The negative electrode contains at least one compound selected from the group consisting of fluorophosphate, difluorophosphate, acetate, and propionate in a total amount of 10 ppm or more in the non-aqueous electrolyte solution, and the negative electrode The present invention provides a lithium ion secondary battery characterized in that the active material contains two or more types of negative electrode active materials having different properties.

[In General Formula (1), R ¹ and R ² represent the same or different organic group having 1 to 12 carbon atoms, and n represents an integer of 3 to 10. ]

[In General Formula (2), R ^{3 to} R ⁵ represent an organic group having 1 to 12 carbon atoms which may be the same or different from each other, x represents an integer of 1 to 3, p, q and Each r represents an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3. ]

[In General Formula (3), R ^{6 to} R ⁸ represent an organic group having 1 to 12 carbon atoms which may be the same as or different from each other, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P; ]

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

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these specific contents. However, various modifications can be made within the scope of the gist.

<Non-aqueous electrolyte>
The non-aqueous electrolyte used in the lithium ion secondary battery of the present invention contains a lithium salt and a non-aqueous solvent that dissolves the lithium salt.
[Lithium salt]
The lithium salt is not particularly limited as long as it is known to be used as an electrolyte of a non-aqueous electrolyte solution for a lithium ion secondary battery, and examples thereof include the following.

Inorganic lithium salt:
Inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; perhalogenates such as LiClO ₄ , LiBrO ₄ , LiIO ₄ ; inorganic chloride salts such as LiAlCl ₄ .
Fluorine-containing organic lithium salt:
Perfluoroalkane sulfonates such as LiCF ₃ SO ₃ ; 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 ), etc. Perfluoroalkanesulfonylimide salt; Perfluoroalkanesulfonylmethide salt such as LiC (CF ₃ SO ₂ ) ₃ ; 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 (CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Fluoroalkyl fluorophosphates such as Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ].
Oxalatoborate salt:
Lithium difluorooxalatoborate, lithium bis (oxalato) borate and the like.

These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. Among these, LiPF ₆ , LiBF _{4 and the} like are preferable, and LiPF ₆ is particularly preferable when comprehensively judging the solubility in the non-aqueous solvent, the charge / discharge characteristics in the case of the secondary battery, the output characteristics, the cycle characteristics, and the like. .

  The concentration of the lithium salt in the nonaqueous electrolytic solution is not particularly limited, but is usually 0.3 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more. Moreover, the upper limit is 2 mol / L or less normally, Preferably it is 1.8 mol / L or less, More preferably, it is 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the non-aqueous electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity. Performance may be degraded.

  The non-aqueous electrolyte preferably contains a fluorine-containing lithium salt as the lithium salt, and the concentration of the fluorine-containing lithium salt in the non-aqueous electrolyte is not particularly limited, but is 0.5 mol / L or more. The amount is particularly preferably 0.7 mol / L or more. Moreover, the upper limit is preferably 2 mol / L or less, particularly preferably 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the non-aqueous electrolyte solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity decreases due to an increase in viscosity, and the performance of the lithium ion secondary battery May decrease.

Lithium salts may be used singly or in combination of two or more in any combination and ratio. Preferred examples when two or more lithium salts are used are LiPF ₆ and LiBF _4. In this case, the proportion of LiBF _{4 in} the total of both is particularly preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 5% by mass. More preferably, it is as follows. Another preferred example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonylimide salt. In this case, the proportion of the inorganic fluoride salt in the total of both is 70% by mass or more and 99% by mass. % Or less, particularly preferably 80% by mass or more and 98% by mass or less. The combined use of both has the effect of suppressing deterioration due to high temperature storage.

[Nonaqueous solvent]
As the non-aqueous solvent, it can be appropriately selected from those conventionally proposed as solvents for non-aqueous electrolyte solutions. For example, the following are mentioned.
(1) Cyclic carbonate:
As for carbon number of the alkylene group which comprises a cyclic carbonate, 2-6 are preferable, Most preferably, it is 2-4. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, 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 is preferably 1 to 5, and particularly preferably 1 to 4, respectively. Specifically, for example, symmetric chain carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; asymmetric chain carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate And dialkyl carbonates. Of these, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like are preferable.
(3) Cyclic ester:
Specific examples include γ-butyrolactone and γ-valerolactone.
(4) Chain ester:
Specific examples include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.
(5) Cyclic ether:
Specific examples include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like.
(6) Chain ether:
Specific examples include dimethoxyethane and dimethoxymethane.
(7) Sulfur-containing organic solvent:
Specific examples include sulfolane and diethylsulfone.

  These may be used alone or in combination of two or more, but it is preferable to use in combination of two or more. For example, it is preferable to use a high dielectric constant solvent such as cyclic carbonates or cyclic esters in combination with a low viscosity solvent such as chain carbonates or chain esters.

  One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the nonaqueous solvent is 85% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more. Further, the capacity of the cyclic carbonate with respect to the total of the cyclic carbonate and the chain carbonate is 5% or more, preferably 10% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, More preferably, it is 30% or less. It is particularly preferred that the above preferred volume range of the total amount of carbonates occupying the entire non-aqueous solvent is combined with the preferred above volume range of cyclic carbonates relative to cyclic and chain carbonates.

  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 ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. In the case of containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50.

  Among these, those containing asymmetric chain carbonates are more preferable, particularly ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl. Those containing ethylene carbonate such as methyl carbonate, symmetric chain carbonates, and asymmetric chain carbonates are preferred because of a good balance between cycle characteristics and large current discharge characteristics. Among these, those in which the asymmetric chain carbonate is ethyl methyl carbonate are preferable, and the number of carbon atoms of the alkyl group constituting the dialkyl carbonate is preferably 1 or 2.

  Other examples of preferred non-aqueous solvents are those containing chain esters. In particular, those containing a chain ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving the low-temperature characteristics of the battery. Examples of the chain esters include methyl acetate and ethyl acetate. 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, usually 50% or less, preferably 35% or less, more preferably 30% or less, More preferably, it is 25% or less.

  Examples of other preferable non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more organic solvents selected from the group. The mixed solvent becomes 60% by volume or more of the whole. Such a mixed solvent preferably has a flash point of 50 ° C. or higher, and particularly preferably has a flash point of 70 ° C. or higher. A non-aqueous electrolyte using this solvent reduces evaporation of the solvent and leakage even when used at high temperatures. Among them, the amount of γ-butyrolactone in the nonaqueous solvent is 60% by volume or more, and the total of ethylene carbonate and γ-butyrolactone in the nonaqueous solvent is 80% by volume or more, preferably 90% by volume or more. And the volume ratio of ethylene carbonate to γ-butyrolactone is 5:95 to 45:55, or the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 80% by volume or more, preferably 90% When the ratio of ethylene carbonate to propylene carbonate is 30:70 to 60:40, the balance between cycle characteristics and large current discharge characteristics is generally improved.

[Specific compounds]
The non-aqueous electrolyte used for the lithium ion secondary battery of the present invention is represented by the cyclic siloxane compound represented by the general formula (1), the fluorosilane compound represented by the general formula (2), and the general formula (3). A compound having an SF bond in the molecule, at least one compound selected from the group consisting of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, and propionate (Hereinafter, these may be abbreviated as “specific compounds”) 10 ppm or more is essential.

  Providing a lithium ion secondary battery with good cycle characteristics and low-temperature output by combining a non-aqueous electrolyte containing such a specific compound and a negative electrode active material having specific properties described later as a negative electrode active material can do.

[[Cyclic Siloxane Compound Represented by General Formula (1)]]
R ¹ and although R ² are identical there may be different even if an organic group having 1 to 12 carbon atoms with each other, as R ¹ and R ² in the general formula (1) cyclic siloxane compound represented by, Chain alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group and t-butyl group; cyclic alkyl groups such as cyclohexyl group and norbornyl group; vinyl group, Alkenyl groups such as 1-propenyl group, allyl group, butenyl group, 1,3-butadienyl group; alkynyl groups such as ethynyl group, propynyl group, butynyl group; halogenated alkyl groups such as trifluoromethyl group; 3-pyrrolidino An alkyl group having a saturated heterocyclic group such as a propyl group; an aryl group such as a phenyl group optionally having an alkyl substituent; a phenylmethyl group; Examples thereof include aralkyl groups such as nylethyl group; trialkylsilyl groups such as trimethylsilyl group; trialkylsiloxy groups such as trimethylsiloxy group.

Among these, those having a small number of carbon atoms tend to exhibit characteristics, and organic groups having 1 to 6 carbon atoms are preferable. Alkenyl groups act on non-aqueous electrolytes and coatings on electrode surfaces to improve input / output characteristics, and aryl groups have the effect of capturing radicals generated in the battery during charge and discharge to improve overall battery performance. Therefore, it is preferable. Accordingly, R ¹ and R ² are particularly preferably a methyl group, a vinyl group, or a phenyl group.

  In general formula (1), n represents an integer of 3 to 10, but an integer of 3 to 6 is preferable, and 3 or 4 is particularly preferable.

  Examples of the cyclic siloxane compound represented by the general formula (1) include, for example, hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5. -Cyclotrisiloxane such as trivinylcyclotrisiloxane, cyclotetrasiloxane such as octamethylcyclotetrasiloxane, cyclopentasiloxane such as decamethylcyclopentasiloxane, and the like. Of these, cyclotrisiloxane is particularly preferred.

[[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 having 1 to 12 carbon atoms which may be the same as or different from each other, but R in the general formula (1) Examples of the chain alkyl group, cyclic alkyl group, alkenyl group, alkynyl group, halogenated alkyl group, alkyl group having a saturated heterocyclic group, phenyl group optionally having an alkyl group, etc. mentioned as examples of ¹ and R ² In addition to aryl groups, aralkyl groups, trialkylsilyl groups, trialkylsiloxy groups, carbonyl groups such as ethoxycarbonylethyl groups; carboxyl groups such as acetoxy groups, acetoxymethyl groups, trifluoroacetoxy groups; methoxy groups, ethoxy groups, Oxy group such as propoxy group, butoxy group, phenoxy group, allyloxy group; amino group such as allylamino group; Mention may be made of the group, and the like.

  In general formula (2), x represents an integer of 1 to 3, p, q, and r each represents an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3. Inevitably, x + p + q + r = 4.

  Examples of the fluorosilane compound represented by the general formula (2) include trimethylfluorosilane, triethylfluorosilane, tripropylfluorosilane, phenyldimethylfluorosilane, triphenylfluorosilane, vinyldimethylfluorosilane, vinyldiethylfluorosilane, In addition to monofluorosilanes such as vinyldiphenylfluorosilane, trimethoxyfluorosilane, and triethoxyfluorosilane, difluorosilanes such as dimethyldifluorosilane, diethyldifluorosilane, divinyldifluorosilane, and ethylvinyldifluorosilane; methyltrifluorosilane, Also included are trifluorosilanes such as ethyltrifluorosilane.

  If the boiling point of the fluorosilane compound represented by the general formula (2) is low, it will volatilize, and therefore it may be difficult to contain a predetermined amount in the non-aqueous electrolyte. Moreover, even if it is made to contain in a non-aqueous electrolyte solution, there exists a possibility that it may volatilize on the conditions that the heat_generation | fever of a battery by charging / discharging or external environment becomes high temperature. Accordingly, those having a boiling point of 50 ° C. or higher at 1 atm are preferable, and those having a boiling point of 60 ° C. or higher are particularly preferable.

  Further, like the compound of the general formula (1), the organic group having a smaller number of carbon atoms is more effective, and the alkenyl group having 1 to 6 carbon atoms acts on the non-aqueous electrolyte solution or the electrode surface coating. Thus, the input / output characteristics are improved, and the aryl group has the effect of capturing radicals generated in the battery during charge / discharge and improving the overall battery performance. Therefore, from this viewpoint, the organic group is preferably a methyl group, a vinyl group, or a phenyl group, and examples of the compound include trimethylfluorosilane, vinyldimethylfluorosilane, phenyldimethylfluorosilane, and vinyldiphenylfluorosilane. .

[[Compound represented by 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 as or different from each other. A chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, an alkyl group having a saturated heterocyclic group, or an alkyl group, which are mentioned as examples of R ^{3 to} R ⁵ Aryl groups such as phenyl groups, aralkyl groups, trialkylsilyl groups, trialkylsiloxy groups, carbonyl groups, carboxyl groups, oxy groups, amino groups, benzyl groups, and the like can be similarly exemplified.

  A in the compound represented by the general formula (3) is not particularly limited as long as A is a group composed of H, C, N, O, F, S, Si and / or P, but the general formula (3) C, S, Si or P is preferable as the element directly bonded to the oxygen atom therein. Examples of the existence form of these atoms include a chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, a carbonyl group, a sulfonyl group, a trialkylsilyl group, a phosphoryl group, and a phosphinyl group. Those are preferred. The molecular weight of the compound represented by the general formula (3) is preferably 1000 or less, particularly preferably 800 or less, and more preferably 500 or less.

  Examples of the compound represented by the general formula (3) include siloxane compounds such as hexamethyldisiloxane, 1,3-diethyltetramethyldisiloxane, hexaethyldisiloxane, and octamethyltrisiloxane; methoxytrimethylsilane, ethoxy Alkoxysilanes such as trimethylsilane; peroxides such as bis (trimethylsilyl) peroxide; carboxylic acid esters such as trimethylsilyl acetate, triethylsilyl acetate, trimethylsilyl propionate, trimethylsilyl methacrylate, trimethylsilyl trifluoroacetate; methanesulfonic acid Sulfonic acid esters such as trimethylsilyl, trimethylsilyl ethanesulfonate, triethylsilyl methanesulfonate, trimethylsilyl fluoromethanesulfonate; bis (trimethylsilyl) Sulfuric esters such as sulfates; tris (trimethylsiloxy) borate esters such as boron; tris (trimethylsilyl) phosphate, tris (trimethylsilyl) phosphite phosphoric acid or phosphorous acid esters such as phosphite and the like.

  Of these, siloxane compounds, sulfonic acid esters, and sulfuric acid esters are preferable, and sulfonic acid esters are particularly preferable. The siloxane compound is preferably hexamethyldisiloxane, the sulfonic acid ester is preferably trimethylsilyl methanesulfonate, and the sulfuric acid ester is preferably bis (trimethylsilyl) sulfate.

[[Compound with SF bond in molecule]]
The compound having an S—F bond in the molecule is not particularly limited, but sulfonyl fluorides and fluorosulfonic acid esters are preferred. 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 Examples include 3-hexafluoropropane-1,3-bis (sulfonyl fluoride), methyl fluorosulfonate, ethyl fluorosulfonate, and the like. Of these, methanesulfonyl fluoride, methanebis (sulfonyl fluoride) or methyl fluorosulfonate is preferable.

[[Nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, propionate]]
The counter cation of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, propionate is not particularly limited, but metal elements such as Li, Na, K, Mg, Ca, Fe, Cu, etc. In addition, ammonium or quaternary ammonium represented by NR ⁹ R ¹⁰ R ¹¹ R ¹² (wherein R ^{9 to} R ¹² each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms). Is mentioned. Here, the organic group having 1 to 12 carbon atoms of R ^{9 to} R ¹² is an alkyl group which may be substituted with a halogen atom, a cycloalkyl group which may be substituted with a halogen atom, or a halogen atom. An aryl group which may be present, a nitrogen atom-containing heterocyclic group, and the like. 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 is preferable, and lithium is particularly preferable from the viewpoint of battery characteristics when used in a lithium ion secondary battery. Of these, nitrate or difluorophosphate is preferable in terms of the effect of improving output, battery cycle and high-temperature storage characteristics, and lithium difluorophosphate is particularly preferable. These compounds synthesized in a non-aqueous solvent may be used as they are, or those synthesized separately and substantially isolated are added in a non-aqueous solvent or a non-aqueous electrolyte. May be.

  A specific compound, that is, a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and an SF bond in the molecule. Compound, nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate or propionate may be used alone, or two or more compounds may be used in any combination and ratio May be. Moreover, even if it is a compound classified into said each with a specific compound, 1 type may be used independently and 2 or more types of compounds may be used together by arbitrary combinations and a ratio.

  The ratio of these specific compounds in the non-aqueous electrolyte solution is essential to be 10 ppm or more (0.001 mass% or more) in total with respect to the total non-aqueous electrolyte solution, but is preferably 0.01 mass% or more. Preferably it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more. 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 obtain the effect of maintaining the output characteristics even after long-term use. On the other hand, if the concentration is too high, the charge / discharge efficiency may be reduced.

  In addition, when these specific compounds are actually used in the production of secondary batteries as non-aqueous electrolytes, the content of the specific compounds is significantly reduced even if the battery is disassembled and the non-aqueous electrolyte is taken out again. There are many. Therefore, what can detect the said specific compound at least from the non-aqueous electrolyte solution extracted from the battery is considered to be included in this invention.

[Other compounds]
The non-aqueous electrolyte solution in the lithium ion secondary battery of the present invention contains a lithium salt that is an electrolyte and a specific compound as essential components, but other compounds may be added as necessary within the range that does not impair the effects of the present invention. It can be contained in any amount. As such other compounds, specifically, for example,
(1) Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, o-cyclohexylfluoro Partially fluorinated products of the above-mentioned aromatic compounds such as benzene and p-cyclohexylfluorobenzene; fluorinated anisole such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole Overcharge inhibitors such as compounds;
(2) vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, trifluoropropylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, etc. Negative electrode film-forming agent;
(3) Ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sultone, butane sultone, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide Positive electrode protective agents such as tetramethylene sulfoxide, diphenyl sulfide, thioanisole, diphenyl disulfide, dipyridinium disulfide;
Etc.

  As the overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. Two or more of these may be used in combination. When using 2 or more types together, it is particularly preferable to use cyclohexylbenzene or terphenyl (or a partially hydrogenated product thereof) together with t-butylbenzene or t-amylbenzene.

  As the negative electrode film forming agent, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, and maleic anhydride are preferable. Two or more of these may be used in combination. As the positive electrode protective agent, ethylene sulfite, propylene sulfite, propane sultone, butane sultone, methyl methanesulfonate, and busulfan are preferable. Two or more of these may be used in combination. Moreover, the combined use of a negative electrode film forming agent and a positive electrode protective agent, or the combined use of an overcharge inhibitor, a negative electrode film forming agent, and a positive electrode protective agent is particularly preferable.

  The content ratio of these other compounds in the non-aqueous electrolyte solution is not particularly limited, but is preferably 0.01% by mass or more, particularly preferably 0.1% by mass or more, respectively, based on the whole non-aqueous electrolyte solution. The upper limit is preferably 5% by mass or less, particularly preferably 3% by mass or less, and further preferably 2% by mass or less. By adding these compounds, it is possible to suppress rupture / ignition of the battery at the time of abnormality due to overcharge, and to improve the capacity maintenance characteristic and cycle characteristic after high-temperature storage.

<Negative electrode>
The negative electrode used for the lithium ion secondary battery of this invention is demonstrated below.
[Negative electrode active material]
The negative electrode active material used for the negative electrode is described below.

  As the negative electrode active material used in the present invention, a material capable of electrochemically inserting and extracting lithium ions is used. The negative electrode active material used in the lithium ion secondary battery of the present invention is characterized by containing two or more types of negative electrode active materials having different properties.

  “Different properties” mentioned here are X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, ash content, etc. In addition to the difference in powder shape and powder physical properties typified by the above, “composite carbonaceous materials containing two or more types of carbonaceous materials having different crystallinity” and “different types containing two or more types of carbonaceous materials having different orientations”. The composition of the material such as “oriented carbon composite” is different, and the processing such as “adding heat treatment to the negative electrode active material” or “adding mechanical energy treatment to the negative electrode active material” is also different. Including.

[Differences in shape, physical properties, etc.]
Among these, the negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different volume-based average particle diameters (median diameters), thereby improving cycle characteristics while maintaining low-temperature output. It becomes possible. The difference in volume-based average particle diameter (median diameter) is usually 1 μm or more, preferably 2 μm or more, more preferably 5 μm or more. As an upper limit, it is 30 micrometers or less normally, Preferably it is 25 micrometers or less. Beyond this range, the particle diameter on the larger median diameter tends to be too large, which may cause problems such as striation on the coated surface during electrode production. On the other hand, if it falls below this range, the effect of mixing the two types may be difficult to express.

In addition, the negative electrode active material used in the present invention can exhibit good characteristics for the same reason as described above even when the material has an uneven volume-based particle size distribution. “Volume-based particle size distribution is biased” means that the volume-based particle size distribution with the logarithmic scale on the horizontal axis is not symmetrical when centered on the volume-based average particle size (median diameter). As the degree of not being symmetrical, the value of Z represented by the following formula (1) is usually 0.3 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more. If Z is less than this value, it may be difficult to obtain the effect of improving the cycle characteristics due to the uneven particle size distribution.
Z = | (mode diameter) − (median diameter) | (1)
In the formula (1), the unit of the mode diameter and the median diameter is “μm”, and “||” represents an absolute value.

  In the present invention, the volume-based average particle diameter (median diameter) and mode diameter are determined by dispersing the negative electrode active material in a 0.2 mass% aqueous solution (about 1 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant. And defined by a value measured using a laser diffraction particle size distribution meter (LA-700, manufactured by Horiba, Ltd.). The “median diameter” is generally also referred to as d50, and refers to the particle diameter in which the larger side and the smaller side are equivalent when the powder is divided into two from a certain particle diameter on a volume basis. Is the particle size distribution indicating the maximum value of the distribution in the volume-based particle size distribution, both of which are simply the values of “median diameter” and “mode diameter” in LA-700 manufactured by HORIBA, Ltd. Each is uniquely displayed on the device.

  In addition, it is preferable to use a negative electrode active material having a median diameter of 10 μm or less as at least one of the negative electrode active materials because an effect of improving cycle characteristics can be obtained while maintaining a low temperature output. 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 the range of 0.5 to 10% by mass with respect to the whole negative electrode active material.

  In addition, the negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different Raman R values measured by using an argon ion laser Raman spectrum method, so that low temperature output can be achieved while maintaining cycle characteristics. It becomes possible to improve. 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 Is in the range of 1.2 or less. Below this range, it may be difficult to obtain the effect due to the difference in the Raman R value. On the other hand, if it exceeds this range, the irreversible capacity may increase due to a portion having a high Raman R value.

In the present invention, a Raman spectrum is measured by using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), and the sample is naturally dropped into the measurement cell to fill the sample, and the measurement is performed on the sample surface in the cell. While irradiating with argon ion laser light, the cell is rotated in a plane perpendicular to the laser light. The obtained Raman spectrum, the intensity I _A of the peak P _A in the 1580 cm ^-1, and measuring the intensity I _B of a peak P _B of 1360 cm ^-1, the intensity ratio R of the (R = I _B / I _A) This is calculated and defined as the Raman R value of the graphitic carbon particles. Further, the half width of the peak P _{A at} 1580 cm ⁻¹ of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the graphitic carbon particles.

Here, the Raman spectrum measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
・ Raman R value, Raman half width analysis: Background processing ・ Smoothing processing: Simple average, 5 points of convolution

The negative electrode active material used as a negative electrode active material used in the present invention, although the Raman half-value width of 1580 cm ^-1 is not particularly limited, usually 10 cm ^-1 or more, preferably 15cm ^-1 or more, and as the upper limit, usually 150cm ^-1 or less, preferably 140 cm ^-1 or less. If the Raman half width is less than this range, the crystallinity of the particle surface becomes too high, and the low-temperature output may decrease. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, and the irreversible capacity may increase.

  In addition, the negative electrode active material used as the negative electrode active material used in the present invention can improve low-temperature output while maintaining cycle characteristics even when it contains two or more types of negative electrode active materials having different crystallinity. Become. The crystallinity here refers to a laminated structure such as the thickness and spacing of a repeating structure of a laminate of carbon hexagonal mesh surfaces. Specific physical property values showing the difference in crystallinity are not particularly limited, but there are, for example, face spacing, crystallite size, etc., and these are two or more types of negative electrode active materials used in the lithium ion secondary battery of the present invention. It is preferable that they are different. If the difference in crystallinity is too small, the effect of mixing may be difficult to obtain.

  The negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different (002) plane spacings (d002) by wide-angle X-ray diffraction, so that low temperature output is maintained while maintaining cycle characteristics. It becomes possible to improve. The difference in interplanar spacing (d002) is usually 0.0005 nm or more, preferably 0.001 nm or more, more preferably 0.003 nm or more, still more preferably 0.004 nm or more, and the upper limit is usually 0.05 or less. , Preferably 0.04 or less, more preferably 0.03 nm or less, still more preferably 0.02 nm or less. Below 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 low crystallinity. In the present invention, the (002) plane spacing (d002) by the wide angle X-ray diffraction method is the d value (interlayer distance) of the lattice plane (002 plane) obtained by the X-ray diffraction by the Gakushin method.

  Further, the negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different crystallite sizes (Lc) determined by X-ray diffraction by the Gakushin method, so that the low temperature is maintained while maintaining cycle characteristics. The output can be improved. The difference in crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually in the range of 1 nm or more, preferably 10 nm or more, more preferably 50 nm or more. Below this range, it may be difficult to obtain the effect due to the difference in crystallite size.

Further, the negative electrode active material used in the present invention can improve low-temperature output while maintaining cycle characteristics even when it contains two or more negative electrode active materials having different true densities. The difference between the true density, typically 0.03 g / cm ³ or higher, preferably 0.05 g / cm ³ or more, more preferably 0.1 g / cm ³ or more, more preferably 0.2 g / cm ³ or more, 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. Below this range, it may be difficult to obtain the effect due to the difference in true density. On the other hand, if it exceeds this range, the irreversible capacity may increase due to the low true density.

  The true density referred to in the present invention is defined by a value measured by a liquid phase replacement method (pycnometer method) using butanol.

In addition, the negative electrode active material used in the present invention can improve cycle characteristics while maintaining a low temperature output even when it contains two or more negative electrode active materials having different degrees of circularity. 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. Below 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 streaking may occur during electrode formation due to the low circularity.
The circularity referred to in the present invention is defined by the following equation.
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the circularity value, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) was used, and about 0.2 g of a sample was added to a polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, in an amount of 0. Dispersed in a 2% by weight aqueous solution (about 50 mL), irradiated with 28 kHz ultrasonic waves at 60 W output for 1 minute, specified a detection range of 0.6 to 400 μm, and measured particles with a particle size in the range of 3 to 40 μm Use the value obtained.

In addition, the negative electrode active material used in the present invention can improve cycle characteristics while maintaining a low-temperature output even by containing two or more negative electrode active materials having different tap densities. The difference in tap density is usually 0.1 g / cm ³ or more, preferably 0.2 g / cm ³ or more, more preferably 0.3 g / cm ³ or more. Below 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 measured by passing a sieve having a mesh size of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, Seishin Enterprise Co., Ltd.). Using a tap denser), tapping with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume at that time and the weight of the sample is defined as the tap density.

Further, the negative electrode active material used in the present invention can improve low-temperature output while maintaining cycle characteristics even when it contains two or more negative electrode active materials having different BET specific surface areas. 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 Is in the range of 15 m ² / g or less, more preferably 12 m ² / g or less. Below this range, it may be difficult to obtain the effect of mixing materials having different BET specific surface areas. On the other hand, if it exceeds this range, the irreversible capacity may increase due to a portion having a large BET specific surface area.

  In the present invention, the BET specific surface area is determined by using a surface area meter (a fully automatic surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under a nitrogen flow, and then relative pressure of nitrogen to atmospheric pressure. This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas that has been accurately adjusted so that the value of γ is 0.3.

  As the mixing ratio of the two or more different types of negative electrode active materials used in the present invention, the ratio of one type of negative electrode active material is usually 0.1% by mass or more, preferably 1% by mass with respect to the total amount. Or more, more preferably 10% by mass or more, further preferably 20% by mass or more, and the upper limit is usually 99.9% by mass or less, preferably 99% by mass or less, more preferably 90% by mass or less, and still more preferably. The range is 80% by mass or less. If it is out of this range, the effect of containing two or more different types of negative electrode active materials may be difficult to obtain.

  Of these, it is preferable in view of high cost performance that at least one of two different types of negative electrode active materials contains natural graphite and / or a processed product of natural graphite.

  Natural graphite is classified into flake graphite (Flake Graphite), scaly graphite (Crystalline (Vein) Graphite), and earthy graphite (Amorphous Graphite), depending on its properties ("Powder Process Technology Assembly" (Co., Ltd.). (Refer to "HANDBOOK OF CARBON, GRAPHITE, DIAMOND AND FULLERENES" (published by Noyes Publications)). The degree of graphitization is the highest at 100% for scaly graphite, followed by 99.9% for scaly graphite, but as low as 28% for earthy graphite. Scaly graphite, which is natural graphite, is produced in Madagascar, China, Brazil, Ukraine, Canada, etc., and scaly graphite is produced mainly in Sri Lanka. Soil graphite is mainly produced in the Korean peninsula, China, Mexico, etc. Among these natural graphites, earthy graphite generally has a small particle size and low purity. In contrast, scaly graphite and scaly graphite have advantages such as a high degree of graphitization and a low amount of impurities, and therefore can be preferably used in the present invention.

[Processing differences]
Even when the negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different processing treatments, it is possible to improve low-temperature output while maintaining cycle characteristics. Examples of the processing method of natural graphite include a method of applying heat treatment, a treatment of applying mechanical energy treatment, and the like. An example of the heat treatment is shown below.

[[Heat treatment temperature]]
The heat treatment temperature of the negative electrode active material is usually in the range of 600 ° C. or higher, preferably 1200 ° C. or higher, more preferably 2000 ° C. or higher, still more preferably 2500 ° C. or higher, and 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 below this range, the crystal repair of the surface of the natural graphite particles may be insufficient. On the other hand, if it exceeds the above range, the sublimation amount of graphite tends to increase. The negative electrode active material used in the present invention preferably contains two or more types of negative electrode active materials having different heat treatment temperatures.

[[Heat treatment method]]
The heat treatment is achieved by passing through the aforementioned 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 not longer than 168 hours.

  The heat treatment is usually performed in an inert gas atmosphere such as nitrogen gas or in a non-oxidizing atmosphere by a gas generated from the raw natural graphite. However, in the type of furnace that is embedded in a breeze (fine pitch calcined carbon), the atmosphere may initially be mixed. In such a case, a completely inert gas atmosphere is not necessarily required. Although there is no restriction | limiting in particular as an apparatus used for heat processing, For example, a shuttle furnace, a tunnel furnace, an electric furnace, a lead hammer furnace, a rotary kiln, a direct current furnace, an Atchison 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 types of negative electrode active materials having different heat treatment techniques.

  In addition to the above processes, various processes such as a classification process can be performed. The classification treatment is for removing coarse powder and fine powder to obtain a target particle size. There are no particular restrictions on the equipment used for the classification process. For example, in the case of dry sieving: rotary sieving, oscillating sieving, rotating sieving, vibrating sieving, etc. Machine, inertial classifier, centrifugal classifier (classifier, cyclone, etc.), etc., when wet sieving: mechanical wet classifier, hydraulic classifier, sedimentation classifier, centrifugal wet classifier, Each can be used. The classification treatment can be performed before the heat treatment, or can be performed at other timing, for example, after the heat treatment. Furthermore, the classification process itself can be omitted. The negative electrode active material used in the present invention preferably contains two or more types of negative electrode active materials having different classification treatment conditions.

  Even when the negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different mechanical energy treatments described later, it is possible to improve low-temperature output while maintaining cycle characteristics. An example of mechanical energy treatment is shown below.

[[Mechanical energy treatment]]
The mechanical energy treatment is performed so that the volume average particle diameter before and after the treatment is 1 or less. The “volume average particle diameter ratio before and after treatment” is a value obtained by dividing the volume average particle system after treatment by the volume average particle diameter before treatment. In the present invention, in the mechanical energy treatment performed for producing the raw material before the heat treatment, the average particle size ratio before and after the treatment is preferably 1 or less. The mechanical energy treatment is to control the particle shape while reducing the particle size so that the average particle size ratio before and after the treatment of the powder particles is 1 or less. Among engineering unit operations that can be utilized for particle design such as grinding, classification, mixing, granulation, surface modification, reaction, etc., mechanical energy treatment belongs to grinding treatment.

  Grinding refers to applying a force to a substance to reduce its size and adjusting the particle size, particle size distribution, and fillability of the substance. The pulverization process is classified according to the type of force applied to the substance and the processing form. The force applied to the substance is (1) crushing force (impact force), (2) crushing force (compression force), (3) crushing force (grinding force), and (4) scraping force (shearing force). It is roughly divided into two. On the other hand, the treatment mode is roughly divided into two types: volume pulverization in which cracks are generated and propagated inside the particles, and surface pulverization in which the particle surfaces are scraped off. Volume pulverization proceeds by impact force, compression force, and shear force, and surface pulverization proceeds by grinding force and shear force. Grinding is a process that variously combines the types of forces applied to these substances and the processing forms. The combination can be appropriately determined according to the processing purpose.

  The pulverization may be performed using a chemical reaction such as blasting or volume expansion, but is generally performed using a mechanical device such as a pulverizer. The pulverization treatment used for the production of the spheroidized carbonaceous material as the raw material of the present invention is preferably a treatment that finally increases the proportion of the surface treatment regardless of the presence or absence of volume pulverization. This is because it is important to take the corner of the surface grinding of the particle and introduce roundness into the particle shape. Specifically, the surface treatment may be performed after volume pulverization has progressed to some extent, the surface treatment may be performed with little progress in volume pulverization, and further, volume pulverization and surface treatment may be performed simultaneously. Also good. It is preferable to carry out a pulverization process so that the surface pulverization finally proceeds and the corners of the particles are removed. Even when the negative electrode active material used in the present invention contains two or more types of negative electrode active materials having different degrees of surface treatment, the low temperature output can be improved while maintaining cycle characteristics.

  The apparatus for performing the mechanical energy treatment is selected from those capable of performing the above preferred treatment. Mechanical energy treatment can also be achieved by using one or more of the four forces applied to the substance, but preferably, compression, friction, shearing force, etc., including the interaction of particles mainly with impact force. It is effective to repeatedly give mechanical action to the particles. Therefore, specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, impact compression, friction, shearing force, etc. are applied to the carbon material introduced inside. An apparatus that performs the surface treatment while advancing volume grinding is preferable. Moreover, what has a mechanism which gives a mechanical action repeatedly by circulating or convection of a carbonaceous material is more preferable.

  Preferred devices include a hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron (manufactured by Earth Technica), CF mill (manufactured by Ube Industries), mechanofusion system (manufactured by Hosokawa Micron), and the like. Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable. When processing using this apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and further preferably 50 to 100 m / sec. preferable. The treatment can be performed by simply passing a carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is preferable to circulate or stay in the apparatus for 1 minute or longer. More preferred.

  By performing such a mechanical energy treatment, the carbon particles are roughened only in the vicinity of the surface of the particles while maintaining high crystallinity as a whole, and become strained and exposed edges. This increases the number of surfaces through which lithium ions can enter and exit, resulting in a high capacity even at high current densities.

  In general, scaly, scaly, and plate-like carbon materials tend to have poorer packing properties as the particle size decreases. This is because the particles become more irregular due to pulverization, and the generation of protrusions such as “crushing”, “peeling”, and “bending” is increased on the surface of the particles. This is considered to be because the resistance between adjacent particles is increased due to the adhesion of such irregular shaped particles with a certain degree of strength and the filling property is deteriorated. If these irregularities are reduced and the particle shape is close to a sphere, the decrease in filling property is reduced even if the particle size is reduced. Theoretically, the particle size is the same for both large and small particle size carbon powders. It should indicate the tap density.

  The ratio of these natural graphite and / or processed natural graphite is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more. As an upper limit, it is 99.9 mass% or less normally, Preferably it is 99 mass% or less, More preferably, it is 90 mass% or less, More preferably, it is the range of 80 mass% or less. Below this range, it may be difficult to improve the cost performance by adding natural graphite and / or processed natural graphite. On the other hand, when it exceeds this range, the improvement effect by a different negative electrode active material may become difficult to obtain.

[[Pore volume etc.]]
The pore volume of the negative electrode active material used as the negative electrode active material of the lithium ion secondary battery of the present invention is determined by mercury porosimetry (mercury intrusion method), and the inside of particles corresponding to a diameter of 0.01 μm or more and 1 μm or less. The amount of irregularities due to voids and particle surface steps (hereinafter abbreviated as “pore volume”) is usually 0.01 mL / g or more, 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 forming an electrode plate. If it is less than the range, the high current density charge / discharge characteristics may be deteriorated, and the effect of mitigating the expansion / contraction of the electrode during charge / discharge may not be obtained.

  The total pore volume is preferably 0.1 mL / g or more, more preferably 0.25 mL / g or more, and the upper limit is usually 10 mL / g or less, preferably 5 mL / g or less, more preferably 2 mL / g. The range is as follows. If this range is exceeded, a large amount of binder may be required during electrode plate formation. If it is less than that, it may not be possible to obtain the effect of dispersing the thickener or the binder during the electrode plate formation.

  The average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, further preferably 0.5 μm or more, and the upper limit is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. It is. Beyond this range, a large amount of binder may be required. If it is less, the high current density charge / discharge characteristics may deteriorate.

  As an apparatus for mercury porosimetry, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) is used. A sample (negative electrode material) is weighed to a value of about 0.2 g, sealed in a powder cell, and pretreated by degassing at room temperature and under vacuum (50 μmHg or less) for 10 minutes. Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa). The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation. The surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is calculated as 140 °. As the average pore diameter, the pore diameter when the cumulative pore volume is 50% is used.

[[ash]]
The ash content of the negative electrode active material of the lithium ion secondary battery of the present invention is preferably 1% by mass or less, particularly preferably 0.5% by mass or less, more preferably 0.1% by mass with respect to the total mass of the graphitic carbon particles. It is below mass%. Moreover, as a minimum, it is preferable that it is 1 ppm or more. If the above range is exceeded, deterioration of battery performance due to reaction with the non-aqueous electrolyte during charge / discharge may not be negligible. On the other hand, if it falls below this range, a great amount of time, energy and equipment for preventing contamination may be required for production, which may increase costs.

[[Orientation ratio]]
The orientation ratio of the graphitic carbon particles used as the negative electrode active material of the lithium ion 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. Below this range, the high-density charge / discharge characteristics may deteriorate.

  The orientation ratio is measured by X-ray diffraction. The peaks of (110) and (004) diffraction are integrated by fitting the peaks of (110) and (004) diffraction of carbon by X-ray diffraction using asymmetric Pearson VII as a profile function. Each intensity is calculated. From the obtained integrated intensity, a ratio expressed by (110) diffraction integrated intensity / (004) diffraction integrated intensity is calculated and defined as the orientation ratio of the active material.

The X-ray diffraction measurement conditions here are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree ・ Measurement range and step angle / measurement time:
(110) plane: 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 ion 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. is there. If the upper limit is exceeded, streaking or a uniform coated surface may not be obtained during electrode plate formation, and the high current density charge / discharge characteristics may deteriorate.

  The aspect ratio is expressed as A / B when the diameter is the longest diameter A when observed three-dimensionally and the shortest diameter B is perpendicular to the diameter. The particles are observed with a scanning electron microscope capable of magnifying observation. Select 50 arbitrary particles fixed to the end face of a metal with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed, measure A and B, and average A / B Ask for.

As the at least one preferred physical property value of the negative electrode active material, the Raman R value, the X-ray plane spacing, the crystallite size, the true density, the circularity, the tap density, and the BET specific surface area are as follows.
(1) Raman R value The Raman R value of the carbonaceous material measured using the argon ion laser Raman spectrum method by the measurement method and measurement conditions as described above is usually 0.01 or more, preferably 0.03 or more. Preferably it is 0.1 or more, and the upper limit is 1.5 or less, preferably 1.2 or less, more preferably 1.0 or less, and still more preferably 0.5 or less. When the Raman R value is below this range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge / discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, the reactivity with the non-aqueous electrolyte will increase, and the efficiency and gas generation may increase.

(2) X-ray plane spacing, crystallite size The carbonaceous material preferably has a d-value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method of 0.335 nm or more. The upper limit is usually 0.36 nm or less, preferably 0.35 nm or less, and more preferably 0.345 nm or less.
The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction by the Gakushin method is preferably 1 nm or more, and more preferably 1.5 nm or more.

(3) True density The true density of the carbonaceous material is usually 1.4 g / cm ³ or more, preferably 1.6 g / cm ³ or more, more preferably 1.8 g / cm ³ or more, and still more preferably 2.0 g / cm ^3. cm ³ and the upper limit is 2.26 g / cm ³ or less. The upper limit is the theoretical value of graphite. Below this range, the crystallinity of the carbon is too low and the initial irreversible capacity may increase.

(4) Circularity The circularity is used as the degree of sphericity of the carbonaceous material, and the circularity of particles having a particle size in the range of 3 to 40 μm is preferably 0.1 or more, particularly preferably 0.5 or more. Preferably it is 0.8 or more, more preferably 0.85 or more, and most preferably 0.9 or more. High circularity is preferable because high current density charge / discharge characteristics are improved.

(5) 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, and particularly preferably 1.0 g / cm ^3. It is desired to be cm ³ or more. The upper limit is preferably 2 g / cm ³ or less, more preferably 1.8 g / cm ³ or less, and particularly preferably 1.6 g / cm ³ or less. When the tap density is below this range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, there are too few voids between the particles in the electrode, it becomes difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

(6) BET specific surface area The specific surface area of the carbonaceous material of the present invention measured using 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, more preferably 1.5 m ² / g or more. The upper limit is usually 100 m ² / g or less, preferably 25 m ² / g or less, more preferably 15 m ² / g or less, and still more preferably 10 m ² / g or less. When the value of the specific surface area is less than this range, the acceptability of lithium is likely to deteriorate during charging when used as a negative electrode material, and lithium may easily precipitate on the electrode surface. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.

  If the lithium secondary battery of this invention contains the 2 or more types of negative electrode active material from which a property differs, the kind of negative electrode active material will not be specifically limited. However, properties measured by X-ray diffraction such as face spacing (d002), crystallite size (Lc), orientation ratio, electrode plate orientation ratio, etc .; Raman spectrum related properties such as Raman R value, Raman half width, etc .; Since the above figures are based on the assumption of carbonaceous materials, the difference between the above values applies to carbonaceous materials. On the other hand, particle size distribution-related properties such as median diameter, mode diameter, and Z; BET specific surface area; properties measured by mercury porosimetry such as pore volume, total pore volume, and average pore size; true density; circularity; Regarding the tap density; aspect ratio, the above numerical values are not limited to carbonaceous materials, but are applicable to all materials that can be used as the negative electrode active material, and the above difference in numerical values applies to all materials. However, preferably, the substance having such two kinds of properties is a carbonaceous material. In that case, the above numerical values are regarded as values representing the properties of the carbonaceous material, and two or more types of carbonaceous materials having different properties are preferably used as the negative electrode active material.

[Method of mixing two or more negative electrode active materials]
When mixing two or more types of negative electrode active materials, there is no particular limitation on the apparatus to be used. For example, a V-type mixer, a W-type mixer, a container variable type mixer, a kneader, a drum mixer, a shear mixer, etc. Can be mentioned.

[Electrode production]
The negative electrode may be manufactured by a conventional method. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do. The thickness of the negative electrode active material layer per side at the stage immediately before the step of injecting the electrolyte into the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is usually 150 μm or less, preferably 120 μm. Hereinafter, it is more preferably 100 μm or less. If it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

[[Current collector]]
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is particularly preferable from the viewpoint of ease of processing and cost. When the current collector is a metal material, examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector. When the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.

  A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to. Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

Further, the following physical properties are desired for the current collector substrate.
(1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material thin film forming surface of the current collector substrate defined 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, usually It is 1.5 μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less. By setting the average surface roughness (Ra) of the current collector substrate within the range between the lower limit and the upper limit described above, good charge / discharge cycle characteristics can be expected. By setting it to the above lower limit or more, the area of the interface with the active material thin film is increased, and the adhesion with the active material thin film is improved. The upper limit of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally difficult to obtain as foils having a practical thickness as a battery. 1.5 μm or less is preferable.

(2) Tensile Tensile strength strength collector substrate is not particularly limited, normally 50 N / mm ² or more, preferably 100 N / mm ² or more, more preferably 150 N / mm ² or more. The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(3) 0.2% proof stress of 0.2% proof stress current collector substrate is not particularly limited, normally 30 N / mm ² or more, preferably 100 N / mm ² or more, particularly preferably 150 N / mm ² or more . The 0.2% proof stress is the magnitude of the load necessary to give a plastic (permanent) strain of 0.2%. It means that The 0.2% proof stress in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. it can. Although the thickness of a metal thin film is arbitrary, it is 1 micrometer or more normally, Preferably it is 3 micrometers or more, More preferably, it is 5 micrometers or more. Moreover, an upper limit is 1 mm or less normally, Preferably it is 100 micrometers or less, More preferably, it is 30 micrometers or less. If the thickness is less than 1 μm, the strength may be reduced, and application may be difficult. If it is thicker than 100 μm, it may be difficult to deform it into a desired electrode shape by winding or the like. The metal thin film may be mesh.

[[Ratio of current collector to active material layer thickness]]
The ratio of the thickness of the current collector to the active material layer is not particularly limited, but the value of (thickness of active material layer on one side just before non-aqueous electrolyte injection) / (thickness of current collector) is Usually, it is 150 or less, preferably 20 or less, more preferably 10 or less, and the lower limit is usually 0.1 or more, preferably 0.4 or more, more preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the negative electrode active material increases and the battery capacity may decrease.

[[Electrode density]]
The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g / cm ³ or more, more preferably 1.2 g / cm ^3. More preferably, it is 1.3 g / cm ³ or more, and the upper limit is usually 2 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 The range is 1.7 g / cm ³ or less. If this range is exceeded, the active material particles are destroyed, the initial irreversible capacity increases, the permeability of the non-aqueous electrolyte near the current collector / active material interface decreases, and the high current density charge / discharge characteristics decrease. There is. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and the capacity per unit volume may be lowered.

[[binder]]
The binder for binding the active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode production. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene / butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile / butadiene rubber), rubbery polymers such as ethylene / propylene rubber; styrene / butadiene / styrene block copolymers and hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymers such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinegar Soft resinous polymers such as vinyl copolymers and propylene / α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers Molecule: a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The solvent for forming the slurry is not particularly limited as long as it is a solvent that can dissolve or disperse the active material, binder, thickener and conductive material used as necessary. Either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, a mixed solvent of alcohol and water, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, acrylic acid. Methyl, diethyltriamine, N, N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamerylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, Hexane etc. are mentioned. In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed using a latex such as SBR. In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  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, and the upper limit is usually 20% by mass or less, preferably 15%. It is in the range of not more than mass%, more preferably not more than 10 mass%, still more preferably not more than 8 mass%. If it exceeds this range, the binder ratio in which the binder amount does not contribute to the battery capacity may increase, and the battery capacity may decrease. On the other hand, if it is lower, the strength of the negative electrode is lowered, which may be undesirable in the battery production process. In particular, when the main component contains a rubbery polymer typified by SBR, 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%. The upper limit is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. Further, when the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio 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 is usually 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. When a thickener is further added, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% or more, more preferably 0.6% or more. Is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, applicability may be significantly reduced. If it exceeds the upper limit, the ratio of the active material in the negative electrode active material layer may be reduced, resulting in a problem that the capacity of the battery is reduced and a problem that the resistance between the negative electrode active materials is increased.

[[Plate orientation ratio]]
The electrode plate orientation ratio is usually 0.001 or more, preferably 0.005 or more, more preferably 0.01 or more, and the upper limit is 0.67 or less, which is a theoretical value. Below this range, the high-density charge / discharge characteristics may deteriorate.

  The measurement of the electrode plate orientation ratio is as follows. About the negative electrode after pressing to the target density, the active material orientation ratio of the electrode is measured by X-ray diffraction. The specific method is not particularly limited, but as a standard method, peak separation is performed by fitting the peaks of (110) and (004) diffraction of carbon by X-ray diffraction using asymmetric Pearson VII as a profile function. The integrated intensities of the peaks of (110) diffraction and (004) diffraction are calculated. From the obtained integrated intensity, a ratio represented by (110) diffraction integrated intensity / (004) diffraction integrated intensity is calculated. The electrode active material orientation ratio calculated by this measurement is defined as the electrode plate orientation ratio.

The X-ray diffraction measurement conditions here are as follows. “2θ” indicates a diffraction angle.
-Target: Cu (Kα ray) graphite monochromator-Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree-Measurement range and step angle / measurement time:
(110) plane: 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 to the glass plate with double-sided tape with a thickness of 0.1 mm

[[Impedance]]
The resistance of the negative electrode when charged to 60% of the nominal capacity from the discharged state is preferably 500Ω or less, particularly preferably 100Ω or less, more preferably 50Ω or less, and / or the double layer capacity is preferably 1 × 10 ⁻⁶ F or more. Particularly preferably, it is 1 × 10 ⁻⁵ F or more, more preferably 3 × 10 ⁻⁵ F or more. Within this range, the output characteristics are good and preferable.

The resistance and double layer capacity of the negative electrode are measured by the following procedure. The lithium-ion secondary battery to be measured is charged at a current value that can be charged for 5 hours in a nominal capacity, then maintained in a state where it is not charged / discharged for 20 minutes, and then discharged at a current value that can be discharged in 1 hour for a nominal capacity. The capacity when the capacity is 80% or more of the nominal capacity is used. About the lithium ion secondary battery of the above-mentioned discharge state, it charges to 60% of a nominal capacity with the electric current value which can charge a nominal capacity in 5 hours, Immediately transfers a lithium ion secondary battery in the glove box under argon gas atmosphere. Here, the lithium ion secondary battery is quickly disassembled and taken out in a state where the negative electrode is not discharged or short-circuited, and if it is a double-sided coated electrode, the electrode active material on one side is peeled off without damaging the electrode active material on the other side. Two electrodes are punched to 12.5 mmφ, and are opposed to each other so that the active material surface does not shift through a separator. 60μL of non-aqueous electrolyte used in the battery was dropped between the separator and both negative electrodes, and kept in close contact with the outside air, and the current collector of both negative electrodes was made conductive and the AC impedance method was carried out. To do. The measurement is performed at a temperature of 25 ° C., and a complex impedance measurement is performed in a frequency band of 10 ⁻² to 10 ⁵ Hz. And double layer capacity | capacitance (Cdl) is calculated | required.

<Positive electrode>
The positive electrode used for the non-aqueous electrolyte secondary battery of the present invention will be described below.
[Positive electrode active material]
The positive electrode active material used for the positive electrode is described below.
[[Composition of positive electrode active material]]
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 a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound.

The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples include lithium / cobalt composite oxide such as LiCoO ₂ or LiNiO ₂ . Lithium / nickel composite oxide, 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, and those substituted with other metals such as Si. Specific examples of the substituted ones include, for example, 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. Is mentioned.

As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

[[Surface coating]]
In addition, a material in which a material having a composition different from that of the material constituting the positive electrode active material is attached to the surface of the positive electrode active material can be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon. These surface adhering materials are, for example, dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, and dried. It can be made to adhere to the positive electrode active material surface by the method of making it react by the method etc., the method of adding to a positive electrode active material precursor, and baking simultaneously. In addition, when attaching carbon, the method of attaching carbonaceous material later, for example in the form of activated carbon etc. can also be used.

  The amount of the surface adhering substance is by mass with respect to the positive electrode active material, and is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit is preferably 20% by mass or less, more preferably as a lower limit. It is used at 10 mass% or less, more preferably 5 mass% or less. The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently exhibited. If the amount is too large, the resistance may increase in order to inhibit the entry and exit of lithium ions.

[[Physical properties of positive electrode active material]]
[[[shape]]]
As the shape of the positive electrode active material particles in the present invention, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. It is preferably formed by forming particles, and the shape of the secondary particles is spherical or elliptical. In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, it is preferable that the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration. In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the expansion and contraction of the electrode during charging and discharging is small, and the electrode is produced. The mixing with the conductive material is also preferable because it is easy to mix uniformly.

[[[Tap density]]]
The tap density of the positive electrode active material is usually 1.3 g / cm ³ or more, preferably 1.5 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, and most preferably 1.7 g / cm ³ or more. . If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of the conductive material and the binder increases. In some cases, the filling rate of the substance is limited, and the battery capacity is limited. By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, but there is no particular upper limit. However, if the tap density is too large, diffusion of lithium ions using the non-aqueous electrolyte solution as a medium in the positive electrode active material layer becomes rate-determining, and load characteristics may be likely to deteriorate. Usually, it is 2.5 g / cm ³ or less, preferably 2.4 g / cm ³ or less. The tap density of the positive electrode active material is also measured and defined by the same method as that described in the section of the negative electrode active material.

[[[Median diameter d ₅₀ ]]]
The median diameter d _{50 of the} particles (secondary particle diameter when primary particles are aggregated to form secondary particles) is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, Most preferably, it is 3 μm or more, and the upper limit is usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, and most preferably 15 μm or less. If the lower limit is not reached, a high tap density product may not be obtained, and if the upper limit is exceeded, it takes time to diffuse lithium in the particles. When a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur. Here, by mixing two or more types of positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of forming the positive electrode can be further improved.

The median diameter d ₅₀ in the present invention is measured by a known laser diffraction / scattering particle size distribution measuring device. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

[[[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, it is 0.1 μm or more, and the upper limit is 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 above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the BET specific surface area is greatly reduced, so that there is a high possibility that the battery performance such as output characteristics will deteriorate. There is. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.

  The primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

[[[BET specific surface area]]]
The BET specific surface area of the positive electrode active material used for the 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 It is 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 tends to be lowered, and if the BET specific surface area is larger, the tap density is difficult to increase, and there may be a problem in applicability when forming the positive electrode active material.

  The BET specific surface area is determined by using a surface area meter (for example, a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample for 30 minutes at 150 ° C. under nitrogen flow, and then measuring the relative pressure of nitrogen relative to atmospheric pressure. It is defined by a value measured by a nitrogen adsorption BET one-point method using a gas flow method using a nitrogen-helium mixed gas that is accurately adjusted to have a value of 0.3.

[[[Production method of positive electrode active material]]]
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for producing a spherical or elliptical spherical active material. For example, transition metal raw materials such as transition metal nitrates and transition metal sulfates and, if necessary, raw materials of other elements are mixed with water. It is dissolved or pulverized and dispersed in a solvent such as, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO _3, etc. A method of obtaining an active material by adding a Li source of the above, a transition metal source material such as transition metal nitrate, transition metal sulfate, transition metal hydroxide, transition metal oxide, and other elements as required The raw material is dissolved or pulverized and dispersed in a solvent such as water, and is then dried and molded with a spray dryer or the like to obtain a spherical or elliptical precursor, and LiOH, Li ₂ CO ₃ , LiNO _{3 and} other Li Add the source at high temperature A method of obtaining an active material by firing, a transition metal source material such as transition metal nitrate, transition metal sulfate, transition metal hydroxide, transition metal oxide, and LiOH such as LiOH, Li ₂ CO ₃ , and LiNO ₃ Dissolve or pulverize the source and other elemental raw materials as necessary in a solvent such as water, and dry-mold them with a spray drier or the like to obtain a spherical or elliptical precursor, which is heated at a high temperature. Examples thereof include a method for obtaining an active material by firing.

[[Composition of positive electrode]]
Below, the structure of the positive electrode used for this invention is described.
[[[Electrode structure and fabrication method]]]
The positive electrode for a lithium ion 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. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form are pressure-bonded to a positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry. Two or more types of positive electrode active materials may be mixed in advance and used, or may be mixed by adding them simultaneously when forming the positive electrode.

  The content of the positive electrode active material used in the positive electrode of the lithium ion secondary battery of the present invention in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. It is. Moreover, an upper limit becomes like this. Preferably it is 95 mass% or less, More preferably, it is 93 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

[[[Conductive material]]]
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

[[[Binder]]]
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that can be dissolved or dispersed in the liquid medium used in electrode production may be used. , Polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose and other resin polymers; SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene Rubber, ethylene-propylene rubber and other rubbery polymers; styrene / butadiene / styrene block copolymers or hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer Polymer, styrene / isoprene Thermoplastic elastomeric polymers such as styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymers, etc. Soft polymer such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc .; alkali metal ions (especially lithium ions) Examples thereof include a polymer composition having ion conductivity. In addition, these substances may be used individually by 1 type, and may use 2 or more types together 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 40% by mass or less, and most preferably 10% by mass or less. When the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

[[[Liquid medium]]]
The liquid medium for forming the slurry may be any type of solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. There is no particular limitation, and either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium 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. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

[[[Thickener]]]
In particular, when an aqueous medium is used, it is preferable to make a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. When a thickener is further added, 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, Moreover, as an upper limit, it is 5 mass% or less normally, Preferably it is 3 mass% or less, More preferably, it is the range of 2 mass% or less. Below this range, applicability may be significantly reduced. If it exceeds, the ratio of the active material in the positive electrode active material layer may decrease, and there may be a problem that the capacity of the battery decreases and a problem that the resistance between the positive electrode active materials increases.

[[[Consolidation]]]
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. Density of the positive electrode active material layer, preferably as a lower limit 1.5 g / cm ³ or more, more preferably 2 g / cm ³ or more, still more preferably 2.2 g / cm ³ or more, the upper limit is preferably 3. The range is 5 g / cm ³ or less, more preferably 3 g / cm ³ or less, and still more preferably 2.8 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 may decrease, and the charge / discharge characteristics at a high current density may decrease. On the other hand, if it is lower, the conductivity between the active materials may be reduced, and the battery resistance may be increased.

[[[Current collector]]]
There is no restriction | limiting in particular as a material of a positive electrode electrical power collector, A well-known thing 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. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. Examples include thin films and carbon cylinders. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is 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 strength required for the current collector may be insufficient. Conversely, if the thin 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, but the value of (thickness of active material layer on one side immediately before non-aqueous electrolyte injection) / (thickness of current collector) is It is preferably 20 or less, more preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below this range, the volume ratio of the current collector to the positive electrode active material may increase, and the battery capacity may decrease.

[[[Electrode area]]]
In the case 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 outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the total electrode area of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 20 times or more, and more preferably 40 times or more. The outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. . In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

[[[Discharge capacity]]]
When the non-aqueous electrolyte containing the specific compound of the present invention is used, the electric capacity of the battery element housed in one battery case of the secondary battery (the electric capacity when the battery is discharged from the fully charged state to the discharged state) When the (capacity) is 3 ampere hours (Ah) or more, the contact area with the peripheral member is increased, which is preferable from the viewpoint of improving thermal conductivity. Therefore, the positive electrode plate is preferably designed so that the discharge capacity is fully charged and is 3 ampere hours (Ah) or more and 20 Ah or less, and more preferably 4 Ah or more and 10 Ah or less. If it is less than 3 Ah, the voltage drop due to the electrode reaction resistance becomes large when taking out a large current, and the power efficiency may deteriorate. Above 20 Ah, the electrode reaction resistance decreases and the power efficiency improves, but the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge is large, the durability of repeated charge / discharge is inferior, and abnormalities such as overcharge and internal short circuit When the heat release efficiency deteriorates due to sudden heat generation at the time, the probability that the internal pressure rises and the gas release valve operates (valve operation), or the battery contents erupt violently (explosion) increases. There is.

[[[Positive electrode plate thickness]]]
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is relative to one side of the current collector. The lower limit is preferably 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 200 μm or less, more preferably 100 μm or less.

<Battery shape>
The battery shape is not particularly limited, and examples thereof include a bottomed cylindrical shape, a bottomed square shape, a thin shape, a sheet shape, and a paper shape. When incorporating into a system or device, in order to increase the volumetric efficiency and improve the storage capacity, it may be of a different shape such as a horseshoe shape or a comb shape considering the fit in the peripheral system arranged around the battery. . From the viewpoint of efficiently releasing the heat inside the battery to the outside, a rectangular shape having at least one surface that is relatively flat and has a large area is preferable.

  In a battery having a bottomed cylindrical shape, since the outer surface area with respect to the power generating element to be filled becomes small, it is preferable to design so that Joule heat generated by the internal resistance at the time of charging and discharging efficiently escapes to the outside. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced.

In the bottomed square shape, the ratio between the area S of the largest surface (the product of the width and height of the outer dimensions excluding the terminal portion, unit cm ² ) and the thickness T (unit cm) of the battery outer shape The 2S / T value is preferably 100 or more, and more preferably 200 or more. By increasing the maximum surface, it is possible to improve characteristics such as cycle performance and high-temperature storage even for high-power and large-capacity batteries, and increase heat dissipation efficiency during abnormal heat generation. Can be prevented from becoming a dangerous state.

<Battery configuration>
The rechargeable lithium ion secondary battery of the present invention includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, the non-aqueous electrolyte of the present invention, a separator disposed between the positive electrode and the negative electrode, and a current collecting terminal , And an exterior case. Further, if necessary, a protective element may be mounted inside the battery and / or outside the battery.

[Separator]
The separator used in the present invention has a predetermined mechanical strength that electrically insulates both electrodes, has a high ion permeability, and has resistance to oxidation on the side in contact with the positive electrode and reduction on the negative electrode side. There is no particular limitation as long as it has both. As a material for the separator having such required characteristics, a resin, an inorganic material, glass fiber, or the like is used. As the resin, olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon and the like are used. Specifically, it is preferable to select from materials that are stable with respect to the electrolytic solution and have excellent liquid retention properties, and it is preferable to use a porous sheet or nonwoven fabric made of a polyolefin such as polyethylene or polypropylene.

  Examples of the inorganic material include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and those having a particle shape or fiber shape are used. As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, alumina particles having a 90% particle diameter of less than 1 μm are formed on both surfaces of the positive electrode in a porous layer using a fluororesin as a binder.

[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used.

  The ratio of the volume of the electrode group to the battery internal volume (hereinafter referred to as electrode group occupancy) is preferably 40% to 90%, and more preferably 50% to 80%. If the electrode group occupancy is less than 40%, the battery capacity is small, and if it is 90% or more, the void space is small, the member expands when the battery becomes high temperature, and the vapor pressure of the liquid component of the electrolyte is high. As a result, the internal pressure rises, and various characteristics such as charge / discharge repetition performance and high-temperature storage as a battery are deteriorated. Further, a gas release valve that releases the internal pressure to the outside may operate.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the output recovery by the temperature adaptation according to the present invention, it is necessary to have a structure that reduces the resistance of the wiring portion and the junction portion. When such an internal resistance is small, the effect of combining the non-aqueous electrolyte solution of the present invention and the negative electrode active material is exhibited particularly well.

  In the case where the electrode group has the laminated structure described above, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

  By optimizing the above structure, the internal resistance can be made as small as possible. In a battery used at a large current, the impedance measured by the 10 kHz AC method (hereinafter abbreviated as “DC resistance component”) is preferably 10 milliohms (mΩ) or less, and the DC resistance component is 5 milliohms (mΩ). It is more preferable to make it below. When the direct current resistance component is less than 0.1 milliohm, the high output characteristics are improved, but the ratio of the current collecting structure used increases and the battery capacity may decrease.

  The non-aqueous electrolyte solution containing the specific compound used in the present invention is effective in reducing reaction resistance related to lithium desorption / insertion with respect to the electrode active material, which causes cycle characteristics and low temperature output. Conceivable. However, it has been found that a battery having a large direct current resistance is inhibited by the direct current resistance and the effect of reducing the reaction resistance cannot be reflected 100% on the low temperature discharge characteristics. This can be improved by using a battery having a small DC resistance component, and the effect of the non-aqueous electrolyte solution of the present invention can be sufficiently exhibited.

  Further, from the viewpoint of drawing out the effect of a non-aqueous electrolyte containing a specific compound and producing a battery having high low-temperature discharge characteristics, this requirement and the battery housed in one battery exterior of the secondary battery described above It is particularly preferable to satisfy the requirement that the electric capacity of the element (electric capacity when the battery is discharged from a fully charged state to a discharged state) is 3 ampere hours (Ah) or more at the same time.

[Exterior case]
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the nonaqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In the exterior case using the above metals, a laser-sealed, resistance-welded, ultrasonic welding is used to weld the metals together to form a sealed sealed structure, or a caulking structure using the above-mentioned metals via a resin gasket To do.

  Examples of the outer case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

[Protective element]
PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, the current flowing through the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation For example, a valve (current cutoff valve) that shuts off the current can be used. It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Action and principle>
Lithium ion secondary that has a good balance between low-temperature output and cycle characteristics by combining a “non-aqueous electrolyte containing a specific compound” and a “negative electrode containing two or more negative electrode active materials having different properties” The action / principle that can provide a battery is not clear, but the present invention is not limited by the action / principle, but there are both a part that can contribute to output and a part that can maintain cycle characteristics, and at the same time. It is speculated that the presence of the specific compound emphasizes the effect in particular.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

(Preparation of negative electrode active material 1)
Natural graphite powder (d002: 0.336 nm, Lc: 100 nm or more, Raman R value: 0.11, tap density: 0.46 g / cm ³ , true density: 2.27 g / cm ³ , volume-based average particle diameter: 35 .4 μm) using a hybridization system (hybridization system NHS-1 type manufactured by Nara Machinery Co., Ltd.) and processing at a processing amount of 90 g, a rotor peripheral speed of 60 m / s, and a processing time of 3 minutes. In order to prevent the coarse particles from being mixed, the ASTM 400 mesh sieve was repeated five times. The negative electrode active material obtained here was a carbonaceous material (A). By repeating this operation, an amount necessary for battery production was secured.

(Preparation of negative electrode active material 2)
Fine powder was removed from the commercially available scaly natural graphite powder with an air classifier, and the resulting powder was subjected to ASTM 400 mesh sieving five times in order to prevent mixing of coarse particles. The negative electrode active material obtained here was a carbonaceous material (B).

(Preparation of negative electrode active material 3)
A coal tar pitch having 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 bulk carbonized precursor having a softening point of 385 ° C. The obtained bulk carbonized precursor was packed in a metal container and heat-treated at 1000 ° C. for 2 hours in a box-shaped electric furnace under nitrogen gas flow. The obtained amorphous lump was pulverized with a crusher (Roll jaw crusher manufactured by Yoshida Seisakusho), and further pulverized with a fine pulverizer (Turbo Mill manufactured by Matsubo), and then the fine powder was removed with an air classifier. In order to prevent coarse particles from being mixed in the obtained powder, ASTM 400 mesh sieving was repeated 5 times to obtain an amorphous powder having a volume-based average diameter of 9 μm. The negative electrode active material obtained here was a carbonaceous material (C).

(Preparation of negative electrode active material 4)
The carbonaceous material (A) is mixed with petroleum heavy oil obtained at the time of naphtha pyrolysis, subjected to carbonization treatment at 1300 ° C. in an inert gas, and then the sintered product is classified, whereby the carbonaceous material (A ) A carbonaceous material having a carbonaceous material having different crystallinity on the particle surface was obtained. In the classification process, in order to prevent the inclusion of coarse particles, ASTM 400 mesh sieving was repeated 5 times to obtain a carbonaceous material (D). From the residual carbon ratio, it was confirmed that the obtained negative electrode active material powder was coated with carbonaceous matter derived from 5 parts by weight of petroleum heavy oil with respect to 95 parts by weight of graphite.

(Preparation of negative electrode active material 5)
80% by mass of the carbonaceous material (A) and 20% by mass of the carbonaceous material (B) were mixed until uniform, to obtain a mixed carbonaceous material (E).

(Preparation of negative electrode active material 6)
The carbonaceous material (A) 95% by mass and the carbonaceous material (C) 5% by mass were mixed until uniform, to obtain a mixed carbonaceous material (F).

(Preparation of negative electrode active material 7)
80% by mass of the carbonaceous material (D) and 20% by mass of the carbonaceous material (A) were mixed until uniform, to obtain a mixed carbonaceous material (G).

  The physical properties, shapes, etc. of the carbonaceous materials (A), (B), (C), and the mixed carbonaceous materials (E), (F), (G) prepared in Preparations 1-7 of the negative electrode active material are as described above. Determined by the method. The results are summarized in Table 1.

[Production of battery]
<< Preparation of positive electrode 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) as a binder, an N-methylpyrrolidone solvent Mixed in to a slurry. The obtained slurry was applied on both sides of an aluminum foil having a thickness of 15 μm, dried, and rolled to a thickness of 80 μm with a press machine, and the active material layer was uncoated with a width of 100 mm, a length of 100 mm and a width of 30 mm. It cut out into the shape which has a process part, and was set as the positive electrode. At this time, the density of the active material of the positive electrode was 2.35 g / cm ³ .

<< Preparation of negative electrode 1 >>
98 parts by weight of the negative electrode active material, 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose (concentration of 1% by weight of sodium carboxymethyl cellulose) as a thickener and binder, and an aqueous dispersion of styrene-butadiene rubber (styrene) -2 parts by weight of a butadiene rubber concentration of 50 mass%) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to both sides of a rolled copper foil having a thickness of 10 μm, dried, and rolled to a thickness of 75 μm with a press machine. The active material layer had a width of 104 mm, a length of 104 mm, and a width of 30 mm. It cut out in the shape which has a coating part, and was set as the negative electrode. At this time, the density of the active material of the negative electrode was 1.35 g / cm ³ .

<< Preparation of non-aqueous electrolyte 1 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved. Furthermore, lithium difluorophosphate (LiPO ₂ F ₂ ) was contained so as to be 0.3% by mass.

<< Preparation of non-aqueous electrolyte 2 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved. Furthermore, trimethylsilyl methanesulfonate was contained so as to be 0.3% by mass.

<< Preparation of non-aqueous electrolyte 3 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved. Furthermore, hexamethylcyclotrisiloxane was contained so that it might become 0.3 mass%.

<< Preparation of non-aqueous electrolyte solution 4 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved.

<< Production of Battery 1 >>
The 32 positive electrodes and 33 negative electrodes were alternately arranged, and the porous polyethylene sheet separator (thickness 25 μm) was laminated between each electrode. At this time, the positive electrode active material surface was faced so as not to deviate from the negative electrode active material surface. The uncoated portions of each of the positive electrode and the negative electrode were welded together to produce a current collecting tab, and an electrode group was enclosed in a battery can (outside dimension: 120 × 110 × 10 mm). Thereafter, 20 mL of a non-aqueous electrolyte solution was injected into a battery can loaded with the electrode group, sufficiently infiltrated into the electrode, and sealed to produce a prismatic battery. The rated discharge capacity of this battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz AC method is about 5 milliohms (mΩ). The ratio of the total electrode area of the positive electrode to the sum of the outer surface areas of the batteries was 20.6.

Example 1
A negative electrode produced as a mixed carbonaceous material (E) with the negative electrode active material described in the section << Preparation of Negative Electrode 1 >>, a positive electrode prepared in the section << Preparation of Positive Electrode 1 >>, and a non-preparation prepared in the section << Preparation 1 of Nonaqueous Electrolytic Solution >>. A battery was prepared using the aqueous electrolyte solution by the method described in the section <Preparation of battery 1>. With respect to this battery, the battery evaluation described in the section << Battery evaluation >> was performed. The results are shown in Table 2.

Example 2
A battery was prepared in the same manner as in Example 1 except that the mixed carbonaceous material (F) was used as the negative electrode active material in the section <Preparation of negative electrode 1>, and battery evaluation described in the section <Battery evaluation> was performed. The results are shown in Table 2.

Example 3
A battery was prepared in the same manner as in Example 1 except that the mixed carbonaceous material (G) was used as the negative electrode active material in the section “Preparation of negative electrode 1”, and battery evaluation described in the section “Battery evaluation” was performed. The results are shown in Table 2.

Examples 4-6
Batteries were prepared in the same manner except that the nonaqueous electrolytes of Examples 1 to 3 were replaced with the nonaqueous electrolyte prepared in the section “Preparation of Nonaqueous Electrolyte 2”. Carried out. The results are shown in Table 2.

Examples 7-9
Batteries were prepared in the same manner except that the non-aqueous electrolytes of Examples 1 to 3 were replaced with the non-aqueous electrolyte prepared in the section << Preparation of Non-Aqueous Electrolyte 3 >>. Carried out. The results are shown in Table 2.

Comparative Example 1
A battery was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte prepared in Section << Preparation of Non-Aqueous Electrolyte 4 >> was used as the non-aqueous electrolyte of Example 1, and the battery evaluation described in << Battery Evaluation >> Carried out. The results are shown in Table 2.

Comparative Example 2
A battery was prepared in the same manner as in Example 2 except that the non-aqueous electrolyte prepared in Section << Preparation of Non-Aqueous Electrolyte 4 >> was used as the non-aqueous electrolyte of Example 2, and the battery evaluation described in << Battery Evaluation >> Carried out. The results are shown in Table 2.

Comparative Example 3
A battery was prepared in the same manner except that the carbonaceous material (A) was used as the negative electrode active material in the section “Preparation of Negative Electrode 1” in Comparative Example 1, and battery evaluation described in the section “Battery Evaluation” was performed. The results are shown in Table 2.

Comparative Example 4
A battery was prepared in the same manner except that the carbonaceous material (B) was used as the negative electrode active material in the << Negative Electrode Preparation 1 >> section of Comparative Example 1, and the battery evaluation described in the << Battery Evaluation >> section was performed. The results are shown in Table 2.

Comparative Example 5
Batteries were prepared in the same manner except that the carbonaceous material (C) was used as the negative electrode active material in the section “Preparation of negative electrode 1” in Comparative Example 1, and the battery evaluation described in the section “Battery evaluation” was performed. The results are shown in Table 2.

Comparative Examples 6-8
Batteries were prepared and evaluated in the same manner except that the non-aqueous electrolytes of Comparative Examples 3 to 5 were replaced with the non-aqueous electrolyte prepared in the section << Preparation of Non-Aqueous Electrolytic Solution 1 >>. did. The results are shown in Table 2.

Comparative Examples 9-11
Batteries were prepared and evaluated in the same manner except that the non-aqueous electrolytes of Comparative Examples 3 to 5 were replaced with the non-aqueous electrolyte prepared in Section << Preparation of Non-Aqueous Electrolyte 2 >>. did. The results are shown in Table 2.

Comparative Examples 12-14
Batteries were prepared and evaluated in the same manner except that the non-aqueous electrolytes of Comparative Examples 3 to 5 were replaced with the non-aqueous electrolyte prepared in the section << Preparation of Non-Aqueous Electrolytic Solution 3 >>. did. The results are shown in Table 2.

<Battery evaluation>
(Capacity measurement)
An initial charge / discharge for 5 cycles was performed at 25 ° C. in a voltage range of 4.1 V to 3.0 V at 25 ° C. (voltage range of 4.1 V to 3.0 V) for a new battery that had not been charged or discharged. At this time, the discharge capacity was defined as the initial capacity 0.2C at the fifth cycle (the rated capacity due to the discharge capacity at the hour rate is 1 C, and the same applies hereinafter).

(Output measurement 1)
The battery was charged for 150 minutes at a constant current of 0.2C in an environment of 25 ° C., and allowed to stand for 3 hours in an environment of −30 ° C., then 0.1 C, 0.3 C, 1.0 C, 3.0 C, and 5. The battery was discharged at 0C for 10 seconds, and the voltage at the 10th second was measured. The area of the triangle surrounded by the current-voltage straight line and the lower limit voltage (3 V) was defined as the low temperature output (W).

(Cycle test)
The cycle test was performed in a high temperature environment of 60 ° C., which is regarded as the actual use upper limit temperature of the lithium ion secondary battery. After charging with a constant current constant voltage method of 2C to a charge upper limit voltage of 4.2V, a charge / discharge cycle for discharging with a constant current of 2C to a discharge end voltage of 3.0V was defined as one cycle, and this cycle was repeated up to 500 cycles. The battery after the end of the cycle test was charged and discharged for 3 cycles under an environment of 25 ° C., and the 0.2 C discharge capacity of the third cycle was defined as the post-cycle capacity. From the initial capacity measured prior to the cycle and the post-cycle capacity measured after the end of the cycle test, the cycle retention rate was determined by the following formula.
Cycle maintenance ratio (%) = 100 × capacity after cycle / initial capacity

  As can be seen from the results in Table 2, by using lithium difluorophosphate, trimethylsilyl methanesulfonate, hexamethylcyclotrisiloxane, and using a negative electrode containing two or more negative electrode active materials having different properties. It was found that both cycle characteristics and low-temperature output were good.

  The use of the lithium ion secondary battery of the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game equipment, watches, electric tools, strobes, cameras, etc. Can do. In particular, since the lithium ion secondary battery of the present invention can obtain good cycle characteristics and always high low temperature characteristics, it can be used widely and suitably for applications in environments where there is a great difference in temperature.

Claims (17)

A lithium ion secondary battery having at least a non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt, a positive electrode active material, and a negative electrode active material, wherein the non-aqueous electrolyte solution is a ring represented by the general formula (1) Siloxane compound, fluorosilane compound represented by general formula (2), compound represented by general formula (3), compound having SF bond in molecule, nitrate, nitrite, monofluorophosphate, difluoro It contains at least 10 ppm of at least one compound selected from the group consisting of phosphate, acetate and propionate in the whole non-aqueous electrolyte solution, and the negative electrode active material has properties A lithium ion secondary battery comprising two or more different negative electrode active materials.

[In General Formula (1), R ¹ and R ² represent the same or different organic group having 1 to 12 carbon atoms, and n represents an integer of 3 to 10. ]

[In General Formula (2), R ^{3 to} R ⁵ represent an organic group having 1 to 12 carbon atoms which may be the same or different from each other, x represents an integer of 1 to 3, p, q and Each r represents an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3. ]

[In General Formula (3), R ^{6 to} R ⁸ represent an organic group having 1 to 12 carbon atoms which may be the same as or different from each other, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P; ]   The lithium ion secondary battery according to claim 1, wherein the negative electrode active material contains two or more types of negative electrode active materials having different volume-based average particle diameters (median diameters). 2. The negative electrode active material uses a volume-based average particle diameter (median diameter) (μm) and a mode diameter (μm), and a value of Z defined by the following formula (1) is 0.3 μm or more. Or the lithium ion secondary battery of Claim 2.
Z = | (mode diameter) − (median diameter) | (1)   4. The negative electrode active material according to any one of claims 1 to 3, wherein the negative electrode active material contains two or more types of negative electrode active materials having different Raman R values measured using an argon ion laser Raman spectrum method. Lithium ion secondary battery.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the negative electrode active material contains two or more types of negative electrode active materials having different crystallinity.   6. The negative electrode active material according to any one of claims 1 to 5, wherein the negative electrode active material contains two or more types of negative electrode active materials having different (002) plane spacings according to a wide-angle X-ray diffraction method. Lithium ion secondary battery.   The lithium ion secondary battery according to any one of claims 1 to 6, wherein the negative electrode active material contains two or more types of negative electrode active materials having different true densities.   The lithium ion secondary battery according to any one of claims 1 to 7, wherein the negative electrode active material contains two or more types of negative electrode active materials having different degrees of circularity.   The lithium ion secondary battery according to any one of claims 1 to 8, wherein the negative electrode active material contains two or more types of negative electrode active materials having different tap densities.   The lithium ion secondary battery according to any one of claims 1 to 9, wherein the negative electrode active material contains two or more types of negative electrode active materials having different BET specific surface areas.   The lithium ion secondary battery according to any one of claims 1 to 10, wherein at least one of two or more types of negative electrode active materials having different properties is natural graphite and / or a processed product thereof.   The lithium ion secondary battery according to claim 11, wherein a ratio of natural graphite and / or a processed product thereof in the negative electrode active material is 0.1% by mass or more and 99.9% by mass or less.   The lithium ion secondary battery according to any one of claims 1 to 12, wherein at least one of two or more types of negative electrode active materials having different properties has a median diameter of 10 µm or less.   The non-aqueous electrolyte includes a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and an SF bond in the molecule. At least one compound selected from the group consisting of a compound having a salt, nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate in the entire non-aqueous electrolyte solution. The lithium ion secondary battery according to any one of claims 1 to 13, which is contained in an amount of 01% by mass or more and 5% by mass or less.   15. The lithium ion secondary battery according to claim 1, wherein the total area of the positive electrode area with respect to the surface area of the exterior of the secondary battery is 20 times or more in terms of area ratio.   The lithium ion secondary battery according to any one of claims 1 to 15, wherein a DC resistance component of the secondary battery is 10 milliohms (mΩ) or less.   The lithium ion secondary according to any one of claims 1 to 16, wherein an electric capacity of a battery element housed in one battery exterior of the secondary battery is 3 ampere hours (Ah) or more. battery.