JP2013211223A - Nonaqueous electrolytic solution and battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution for a secondary battery, which improves cycle characteristics even when exposed to a high-temperature storage condition in a charged state, and to provide a secondary battery using the nonaqueous electrolytic solution.SOLUTION: The nonaqueous electrolytic solution which contains an electrolyte and a nonaqueous solvent is characterized by containing a compound represented by a general formula (1). (In the formula, L represents an aliphatic Z-valent linking group having a ring structure, Z is an integer of 2 or more, each of Z number of Rs represents an alkyl group, an alkenyl group, an alkynyl group, or an aryl group, and Rs may have halogen atoms.)

Description

  The present invention relates to a non-aqueous electrolyte and a battery using the same.

With the rapid progress of electronic devices, the demand for higher capacity for secondary batteries is increasing, and lithium ion secondary batteries with higher energy density compared to nickel-cadmium batteries and nickel-hydrogen batteries are widely used. Also actively researched.
The electrolyte used for a non-aqueous electrolyte battery is usually composed mainly of an electrolyte and a non-aqueous solvent. As an electrolytic solution of the lithium ion secondary battery, an electrolyte such as LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , a high dielectric constant solvent such as ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethyl carbonate, A non-aqueous electrolyte solution dissolved in a mixed solvent with a low-viscosity solvent such as diethyl carbonate or ethyl methyl carbonate is used.

When such a lithium ion secondary battery is exposed to a high temperature condition, the electrolyte is decomposed on the electrode, the material constituting the battery is deteriorated, and the characteristics of the battery are deteriorated. There is also a possibility that safety may be lowered such as blistering, ignition or explosion.
So far, as a method for improving the battery characteristics of a lithium ion secondary battery, a nonaqueous electrolytic solution containing a disulfonic acid ester compound has been proposed (see Patent Document 1). In patent document 1, the battery which is excellent in cycling characteristics is made | formed by using the electrolyte solution containing a disulfonic acid ester compound. However, with the technique of Patent Document 1, it has been difficult to suppress deterioration in characteristics when the battery is exposed to high temperature conditions.

JP 2000-133304 A

  The present invention relates to a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte solution for a secondary battery that improves cycle characteristics even when exposed to high temperature storage in a charged state, and a secondary battery using this nonaqueous electrolyte solution It is an issue to provide.

(In the formula, L represents an aliphatic and Z-valent linking group having a ring structure, Z is an integer of 2 or more, and Z Rs are each independently an alkyl group, an alkenyl group, an alkynyl group, or Represents an aryl group, and R may have a halogen atom.)

As a result of repeating various studies in order to solve the above problems, the present inventors have found that the above problems can be solved by including the compound represented by the general formula (1) in the electrolytic solution. The invention has been completed.
That is, the gist of the present invention is as follows.
(A) A non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of occluding and releasing metal ions and a negative electrode having a negative electrode active material capable of occluding and releasing metal ions Because
A non-aqueous electrolyte containing a compound represented by the following general formula (1) (Claim 1).

(In the formula, L represents an aliphatic and Z-valent linking group having a ring structure, Z is an integer of 2 or more, and Z Rs are each independently an alkyl group, an alkenyl group, an alkynyl group, or Represents an aryl group, and R may have a halogen atom.)
(B) In the general formula (1), the linking group L has a cyclopentane ring or a cyclohexane ring as a ring structure.
(C) The non-aqueous electrolyte according to (a) or (b), wherein the linking group L in the general formula (1) and the formula (1) is any of the following:

(D) A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of occluding and releasing metal ions and a negative electrode having a negative electrode active material capable of occluding and releasing metal ions, A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte described in (c).

  By using the electrolytic solution of the present invention as a battery electrolytic solution, a battery having excellent cycle characteristics can be obtained even when exposed to a high temperature state in a charged state of the battery.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the description described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist of the claims.
[1. Non-aqueous electrolyte)
The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, as well as a general non-aqueous electrolyte solution, and further contains a compound represented by the general formula (1). Features.

[1-1. Electrolytes〕
There is no restriction | limiting in the electrolyte used for the non-aqueous electrolyte of this invention, A well-known thing can be arbitrarily employ | adopted if it is used as an electrolyte for the target non-aqueous electrolyte secondary battery. When the nonaqueous electrolytic solution of the present invention is used for a lithium secondary battery, a lithium salt is usually used as an electrolyte.

Specific examples of the electrolyte include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiSO ₃ F, LiN (FSO ₂ ) ₂ ; LiCF ₃ SO ₃ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,3-hexafluoropropane disulfonylimide, lithium cyclic 1,2-tetrafluoroethane disulfonylimide , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC
(CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂
) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , Li
Fluorine-containing organic lithium salts such as BF ₂ (CF ₃ SO ₂ ) ₂ and LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ ; lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tris (oxalato) phosphate, Examples include lithium salts of dicarboxylic acid complexes such as lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate.

Among these, LiPF ₆ , LiBF ₄ , LiSO ₃ F, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (in terms of solubility in a non-aqueous solvent, degree of dissociation, electrical conductivity, and obtained battery characteristics)
CF ₃ SO ₂ ), LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,3-hexafluoropropanedisulfonylimide, lithium cyclic 1,2- Tetrafluoroethanedisulfonylimide, lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate are preferred, especially LiPF ₆ and LiBF ₄ are preferred.

Moreover, electrolyte may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, when two types of specific inorganic lithium salts are used in combination, or when inorganic lithium salts and fluorine-containing organic lithium salts are used in combination, gas generation during trickle charging is suppressed, and deterioration after high-temperature storage is suppressed. Therefore, it is preferable. In particular, the combination and the LiPF ₆ and LiBF _4, and an inorganic lithium salt such as _{LiPF 6, LiBF 4, LiCF 3} SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) _2, etc. It is preferable to use in combination with a fluorine-containing organic lithium salt.

Furthermore, when LiPF ₆ and LiBF ₄ are used in combination, it is preferable that LiBF ₄ is usually contained at a ratio of 0.01% by mass or more and 50% by mass or less with respect to the entire electrolyte. The ratio is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, while preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, Most preferably, it is 3 mass% or less. When the ratio is in the above range, a desired effect can be easily obtained, and the low dissociation degree of LiBF ₄ suppresses increase in resistance of the electrolytic solution.

On the other hand, inorganic lithium salts such as LiPF ₆ and LiBF ₄ and inorganic lithium salts such as LiSO ₃ F and LiN (FSO ₂ ) ₂ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,3-hexafluoropropane disulfonylimide, lithium cyclic 1,2-tetrafluoroethane disulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC ( CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄
(CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C _{2
F 5) 2, LiBF 2 (} CF 3 SO 2) 2, LiBF 2 (C 2 F 5 SO 2) and fluorine-containing organic ₂ or the like,
Dicarboxylic acids such as lithium bis (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluorooxalatoborate, lithium tri (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate When an acid complex lithium salt or the like is used in combination, the proportion of the inorganic lithium salt in the entire electrolyte is usually 70% by mass or more, preferably 80% by mass or more, more preferably 85% by mass or more, and usually 99% by mass or less. Preferably, it is 95 mass% or less.

  The concentration of the lithium salt in the non-aqueous electrolyte of the present invention is arbitrary as long as the gist of the present invention is not impaired, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.8. 8 mol / L or more. Moreover, it is 3 mol / L or less normally, Preferably it is 2 mol / L or less, More preferably, it is 1.8 mol / L or less, More preferably, it is the range of 1.6 mol / L or less. When the concentration of the lithium salt is in the above range, the electrical conductivity of the non-aqueous electrolyte is sufficient, and the electrical conductivity is decreased due to an increase in viscosity, and the non-aqueous electrolyte using the non-aqueous electrolyte of the present invention is reduced. It suppresses the deterioration of the performance of the secondary battery.

[1-2. Nonaqueous solvent)
The non-aqueous solvent contained in the non-aqueous electrolyte solution of the present invention can be appropriately selected from conventionally known solvents as non-aqueous electrolyte solutions. In addition, a non-aqueous solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
Examples of commonly used non-aqueous solvents include cyclic carbonates, chain carbonates, chain and cyclic carboxylic acid esters, chain and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, aromatic fluorine-containing solvents, etc. Is mentioned.

  Examples of the cyclic carbonate include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and the carbon number of the cyclic carbonate is usually 3 or more and 6 or less. Among these, ethylene carbonate and propylene carbonate are preferable in that the electrolyte is easily dissolved because of a high dielectric constant, and cycle characteristics are good when a non-aqueous electrolyte secondary battery is used, and ethylene carbonate is particularly preferable. Further, a part of hydrogen of these compounds may be substituted with fluorine. Examples of cyclic carbonates substituted with fluorine include fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, tetrafluoroethylene carbonate, 1-fluoro- Such as 2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, etc. Examples thereof include C3-C5 cyclic carbonates substituted with fluorine, and among these, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and trifluoromethylethylene carbonate are preferred. Arbitrariness.

  Examples of the chain carbonate include chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, and the like. The number of carbon atoms is preferably 1 or more and 5 or less, particularly preferably 1 or more and 4 or less. Among these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable from the viewpoint of improving battery characteristics.

Moreover, a part of hydrogen of the alkyl group may be substituted with fluorine. Examples of chain carbonates substituted with fluorine include bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) carbonate, bis (2-fluoroethyl) carbonate, and bis (2,2-difluoroethyl). ) Carbonate, bis (2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, and the like.

Examples of chain carboxylates include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, propion Examples include isopropyl acid, methyl butyrate, ethyl butyrate, propyl butyrate, methyl valerate, ethyl valerate and the like, and compounds in which part of hydrogen of these compounds is substituted with fluorine. Examples of the compound substituted with fluorine include methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, 2,2,2-trifluoroethyl trifluoroacetate and the like. Among these, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, and methyl valerate are preferable from the viewpoint of improving battery characteristics.

Examples of the cyclic carboxylic acid esters include γ-butyrolactone, γ-valerolactone, and the like, and compounds obtained by substituting a part of hydrogen of these compounds with fluorine. Among these, γ-butyrolactone is more preferable.
Further, the chain ether includes dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, , 1-ethoxymethoxyethane, 1,2-ethoxymethoxyethane and the like, and compounds obtained by substituting a part of hydrogen of these compounds with fluorine. As compounds in which part of hydrogen of these compounds is substituted with fluorine, bis (trifluoroethoxy) ethane, ethoxytrifluoroethoxyethane, methoxytrifluoroethoxyethane, 1,1,1,2,2,3,4, 5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-ethoxy-4- Trifluoromethyl-pentane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-propoxy-4-trifluoromethyl-pentane, 1,1,2,2-tetra Examples include fluoroethyl-2,2,3,3-tetrafluoropropyl ether and 2,2-difluoroethyl-2,2,3,3-tetrafluoropropyl ether. Among these, 1,2-dimethoxyethane and 1,2-diethoxyethane are more preferable.

Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran and the like, and compounds obtained by substituting a part of hydrogen of these compounds with fluorine.
Further, phosphorus-containing organic solvents include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, phosphorous acid. Examples include triethyl, triphenyl phosphite, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide and the like, and compounds obtained by substituting a part of hydrogen of these compounds with fluorine. As compounds in which part of hydrogen of these compounds is substituted with fluorine, tris phosphate (2,2,2-trifluoroethyl), tris phosphate (2,2,3,3,3-pentafluoropropyl), etc. Is mentioned.

Furthermore, as the sulfur-containing organic solvent, sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methylpropyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate,
Examples thereof include methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, dibutyl sulfate and the like, and compounds in which part of hydrogen of these compounds is substituted with fluorine.

Furthermore, examples of the aromatic fluorine-containing solvent include fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and benzotrifluoride.
Among the above non-aqueous solvents, it is preferable to use cyclic carbonates such as ethylene carbonate and / or propylene carbonate, and the combined use of these with chain carbonate can achieve both high conductivity and low viscosity of the electrolyte. To preferred.

Thus, when using a cyclic carbonate and a chain carbonate together as a non-aqueous solvent, the preferred content of the chain carbonate in the non-aqueous solvent in the non-aqueous electrolyte solution of the present invention is usually 20% by volume or more, Preferably it is 40 volume% or more, and usually 95 volume% or less, preferably 90
% By volume or less. On the other hand, the suitable content of the cyclic carbonate in the nonaqueous solvent in the nonaqueous electrolytic solution of the present invention is usually 5% by volume or more, preferably 10% by volume or more, and usually 80% by volume or less, preferably 70%. % By volume or less. When the proportion of the chain carbonate is in the above range, the viscosity increase of the non-aqueous electrolyte solution of the present invention is suppressed, and the electrical conduction of the non-aqueous electrolyte solution of the present invention due to the decrease in the dissociation degree of the lithium salt that is the electrolyte. Suppress rate decline. However, fluoroethylene carbonate may be used as a solvent or an additive, and in that case, the content is not limited to the above.
In the present specification, the capacity of the non-aqueous solvent is a measured value at 25 ° C., but a measured value at the melting point is used for a solid at 25 ° C. such as ethylene carbonate.
The non-aqueous electrolyte solution of the present invention contains a compound represented by the following general formula (1).

(In the formula, L represents an aliphatic and Z-valent linking group having a ring structure, Z is an integer of 2 or more, and Z Rs are each independently an alkyl group, an alkenyl group, an alkynyl group, or Represents an aryl group, and R may have a halogen atom.)
As an example of a Z-valent linking group which is an aliphatic group represented by L in the general formula (1) and has a ring structure,
The following structures are mentioned.

Among these, preferred examples include (1-7), (1-8), (1-9), (1-10), (1-11), (1-12), (1-13 ), (1-14), (1-15), (1-16), (1-17), (1-18), more preferably (1-7), (1-8) , (1-11), (1-12), (1-13), (1-14), (1-15), (1-16), more preferably (1-11)
(1-12), most preferably (1-11). The compound (1) having these linking groups is easy to produce, and the battery characteristics are improved due to the reactivity of the compound.

Z is an integer of 2 or more, and is generally an integer of 6 or less, preferably 4 or less, more preferably 3 or less. Z R each independently represents an alkyl group, an alkenyl group, an alkynyl group or an aryl group. R may have a halogen atom.
Specific examples of R include the following.
Examples of the alkyl group include alkyl groups having usually 1 or more, usually 8 or less, preferably 6 or less, more preferably 4 or less, and specifically include a methyl group, an ethyl group, a propyl group, and a butyl group. Group, isopropyl group, s-butyl group, t-butyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group and the like. Examples of the alkenyl group include alkenyl groups having 1 or more carbon atoms and usually 8 or less, preferably 6 or less, more preferably 4 or less, specifically vinyl groups, allyl groups, 1-propenyl groups, Examples include 1-butenyl group, 2-butenyl group, 3-butenyl group, 1-fluorovinyl group, trifluorovinyl group and the like.

Examples of the alkynyl group include alkynyl groups having 1 or more carbon atoms, usually 8 or less, preferably 6 or less, more preferably 4 or less, and specifically include ethynyl group, 1-propynyl group, 2- Examples include propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group, fluoroethynyl group, trifluoro-1-propynyl group and the like.
Examples of the aryl group include aryl groups having usually 6 or more carbon atoms, usually 12 or less, preferably 10 or less, and more preferably 7 or less. Specifically, a phenyl group, a benzyl group, a phenethyl group, 4 -Tolyl group, naphthyl group, 4-fluorophenyl group, pentafluorophenyl group, perfluoro-4-tolyl group and the like can be mentioned.

Among these, preferable examples include methyl group, ethyl group, trifluoromethyl group, vinyl group, allyl group, ethynyl group, phenyl group, 4-tolyl group, 4-fluorophenyl group, and pentafluorophenyl group. More preferably, a methyl group, a trifluoromethyl group, a vinyl group, a phenyl group, and a pentafluorophenyl group can be mentioned, and a methyl group and a trifluoromethyl group are still more preferable. By selecting these, the effect of improving the battery characteristics is great, and the production as a compound is facilitated.

  By containing the compound represented by the general formula (1), the nonaqueous electrolytic solution of the present invention can provide a battery having excellent cycle characteristics even when exposed to a high temperature state in a charged state. Although the detailed reason is not yet known, it is assumed that (1) has a linking group having a ring structure, so that the strength of the protective film formed at the electrode interface is increased.

  The content of the compound represented by the formula (1) is not particularly limited, but is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably with respect to the non-aqueous electrolyte. It is 0.1 mass% or more, and is usually 10 mass% or less, preferably 5 mass% or less, more preferably 3 mass% or less. When the content of the compound represented by the formula (1) is in the above range, the effects of the present invention are easily exhibited and battery characteristics are prevented from deteriorating. In the formula (1), the compound may be one kind or a plurality of kinds may be used in combination, but when a plurality of kinds are used in combination, the content represents a total amount of the plurality of kinds.

[1-4. Compound group suitable for use in combination with compound represented by general formula (1)]
In the present invention, in addition to the compound represented by the formula (1), the effect can be further improved by containing a specific compound in the electrolytic solution. The non-aqueous electrolyte solution according to the present invention includes a cyclic carbonate having an unsaturated bond, a cyclic carbonate having a fluorine atom, an acid anhydride, an isocyanate, a nitrile, a difluorophosphate, and a monofluoro as long as the effects of the present invention are not impaired. Various other compounds such as at least one compound selected from the group consisting of phosphate, lithium bisoxalatoborate and lithium difluorooxalatoborate may be contained as an auxiliary agent.

(Cyclic carbonate compound having an unsaturated bond)
Examples of the cyclic carbonate compound having an unsaturated bond include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluoro vinylene carbonate, trifluoromethyl vinylene carbonate, and the like. Vinylene carbonate compound: vinyl ethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate and other vinyl ethylene carbonate compounds; 1,1-dimethyl-2-methylene ester Ren carbonate, methylene ethylene carbonate compounds such as 1,1-diethyl-2-methylene-ethylene carbonate. Among these, vinylene carbonate, vinyl ethylene carbonate, and 1,2-divinyl ethylene carbonate are preferable from the viewpoint of improving cycle characteristics and capacity maintenance characteristics after high-temperature storage, among which vinylene carbonate or vinyl ethylene carbonate is more preferable, and vinylene carbonate is particularly preferable. preferable. These may be used alone or in combination of two or more.

When using 2 or more types together, it is preferable to use together vinylene carbonate and vinyl ethylene carbonate.
When the cyclic carbonate compound having an unsaturated bond is contained, the proportion in the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, Moreover, it is 10 mass% or less normally, Preferably it is 8 mass% or less, More preferably, it is 6 mass% or less. When the content of the cyclic carbonate compound having a carbon-carbon unsaturated bond is in the above range, the effect of improving the cycle characteristics of the battery and the capacity maintenance characteristics after high-temperature storage is sufficiently exhibited. The increase in the amount of gas generated is suppressed.

(Cyclic carbonate compound having a fluorine atom)
Examples of the cyclic carbonate compound having a fluorine atom include fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, tetrafluoroethylene carbonate, 1- Fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate Etc. Of these, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and 1-fluoro-2-methylethylene carbonate are preferable from the viewpoint of improving cycle characteristics and high-temperature storage characteristics. These may be used alone or in combination of two or more.

  When the non-aqueous electrolytic solution contains a cyclic carbonate compound having a fluorine atom, the proportion in the non-aqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.8%. It is 3 mass% or more, More preferably, it is 0.5 mass% or more, Usually, 10 mass% or less, Preferably it is 5 mass% or less, More preferably, it is 4 mass% or less, More preferably, it is 3 mass% or less. However, fluoroethylene carbonate is [1-2. As described in the section “Nonaqueous solvent”, it may be used as a solvent, and in that case, the content is not limited to the above.

(Acid anhydride)
Examples of the acid anhydride include succinic anhydride, methyl succinic anhydride, 4,4-dimethyl succinic anhydride, 4,5-dimethyl succinic anhydride, maleic anhydride, citraconic anhydride, dimethyl maleic anhydride, and phenyl anhydride. Examples thereof include maleic acid, diphenylmaleic anhydride, phthalic anhydride, cyclohexane 1,2-dicarboxylic anhydride, acetic anhydride, propionic anhydride, acrylic anhydride, methacrylic anhydride, and crotonic anhydride. Of these, succinic anhydride, maleic anhydride, citraconic anhydride, acrylic acid anhydride, methacrylic acid anhydride, and crotonic acid anhydride are preferable from the viewpoint of improving cycle characteristics and high temperature storage characteristics. These may be used alone or in combination of two or more.

  When the non-aqueous electrolyte contains an acid anhydride, the proportion in the non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more. More preferably, it is 0.3% by mass or more, usually 10% by mass or less, preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. When the content of the acid anhydride is within the above range, the effect of improving the cycle characteristics of the battery and the capacity maintenance characteristics after high-temperature storage is sufficiently exhibited, and an increase in internal resistance is suppressed.

(Isocyanate)
Examples of the isocyanate include ethyl isocyanate, propyl isocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane 1,3-bis (isocyanatomethyl). ) Cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, allyl isocyanate, and the like. Of these, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane Is preferable from the viewpoint of improving cycle characteristics and high-temperature storage characteristics. These may be used alone or in combination of two or more.

  When the non-aqueous electrolyte contains isocyanate, the proportion in the non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further Preferably it is 0.3 mass% or more, Usually, 10 mass% or less, Preferably it is 5 mass% or less, More preferably, it is 4 mass% or less, More preferably, it is 3 mass% or less. When the isocyanate content is within the above range, the effect of improving the cycle characteristics of the battery and the capacity maintenance characteristics after high-temperature storage is sufficiently exhibited, and an increase in internal resistance is suppressed.

(Nitrile compound)
Examples of nitrile compounds include acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, heptanenitrile, octanenitrile, nonanenitrile, decanenitrile, dodecanenitrile (lauronitrile), tridecanenitrile, tetradecanenitrile (myristonitrile), Mononitriles such as hexadecane nitrile, pentadecane nitrile, heptadecane nitrile, octadecane nitrile (steanonitrile), nonadecane nitrile, icosaninitrile; Undecanedinitrile, dodecanedinitrile, methylmalononitrile,
Ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, trimethylsuccinonitrile, tetramethylsuccinonitrile, 3, 3 '
-Oxydipropionitrile, 3,3'-thiodipropionitrile, 3,3 '-(ethylenedioxy) dipropionitrile, 3,3'-(ethylenedithio) dipropionitrile,
And dinitriles such as 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-tris (2-cyanoethoxy) propane, tris (2-cyanoethyl) amine and the like. Among these, lauronitrile, succinonitrile,
Glutaronitrile, adiponitrile, pimelonitrile and suberonitrile are preferred.

These may be used alone or in combination of two or more.
When the non-aqueous electrolyte contains a nitrile compound, the proportion in the non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, More preferably, it is 0.2% by mass or more, usually 10% by mass or less, preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less. It is. It is. When the content of the nitrile compound is within the above range, the effect of the auxiliary agent is manifested, which is preferable in terms of suppressing gas generation and improving capacity retention characteristics after high-temperature storage.

(Monofluorophosphate and difluorophosphate)
The counter cations of monofluorophosphate and difluorophosphate are not particularly limited, but lithium, sodium, potassium, magnesium, calcium, and NR1R2R3R4 (wherein R1 to R4 are each independently a hydrogen atom or Examples thereof include ammonium represented by an organic group having 1 to 12 carbon atoms.

  Although it does not specifically limit as a C1-C12 organic group represented by R1-R4 of the said ammonium, For example, it may be substituted by the alkyl group which may be substituted by the halogen atom, the halogen atom, or the alkyl group Examples thereof include a good cycloalkyl group, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent. Among these, as R1 to R4, a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group is preferable.

  Specific examples of monofluorophosphate and difluorophosphate include lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, tetramethylammonium monofluorophosphate, tetraethylammonium monofluorophosphate, difluoro Examples include lithium phosphate, sodium difluorophosphate, potassium difluorophosphate, tetramethylammonium difluorophosphate, tetraethylammonium difluorophosphate, etc., preferably lithium monofluorophosphate and lithium difluorophosphate, more preferably lithium difluorophosphate. preferable. These may be used alone or in combination of two or more.

  When the non-aqueous electrolyte contains a monofluorophosphate and / or difluorophosphate, the proportion in the non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.01% by mass or more, More preferably, it is 0.1 mass% or more, More preferably, it is 0.2 mass% or more, Usually, 5 mass% or less, Preferably it is 3 mass% or less, More preferably, it is 2 mass% or less.

  In addition, when the monofluorophosphate and difluorophosphate are actually used for producing a secondary battery as a non-aqueous electrolyte, the content of the non-aqueous electrolyte even if the battery is disassembled and the non-aqueous electrolyte is extracted again. Is often significantly reduced. Therefore, those in which at least one monofluorophosphate and / or difluorophosphate can be detected from the non-aqueous electrolyte extracted from the battery are detected in the non-aqueous electrolyte at a predetermined ratio defined in the present invention. It is considered to be a non-aqueous electrolyte solution.

[1-5. Other additives]
The non-aqueous electrolyte solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. A conventionally well-known thing can be arbitrarily used as an additive. In addition, an additive may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
Examples of the additive include an overcharge inhibitor and an auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high temperature storage.

Specific examples of the overcharge inhibitor include alkylbiphenyls such as biphenyl, 2-methylbiphenyl, 2-ethylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclopentylbenzene, cyclohexylbenzene, cis-1-propyl-4 -Phenylcyclohexane, trans-1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran , Methylphenyl carbonate, ethylphenyl carbonate, diphenyl carbonate, triphenyl phosphate, tris (2-t-butylphenyl) phosphate, tris (3-t-
Butylphenyl) phosphate, tris (4-t-butylphenyl) phosphate, tris (2-t-amylphenyl) phosphate, tris (3-t-amylphenyl) phosphate, tris (4-t-amylphenyl) phosphate, tris Aromatic compounds such as (2-cyclohexylphenyl) phosphate, tris (3-cyclohexylphenyl) phosphate, tris (4-cyclohexylphenyl) phosphate; 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4 ′ -Partially fluorinated products of the above aromatic compounds such as difluorobiphenyl, 2,4-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6 Difluoroanisole, fluorinated anisole compound such as 3,5-difluoro anisole, and the like.

Among these, alkylbiphenyl such as biphenyl and 2-methylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclopentylbenzene, cyclohexylbenzene, cis-1-propyl-4-phenylcyclohexane, trans-1-propyl-4- Phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, methylphenyl carbonate, diphenyl carbonate, triphenyl phosphate, Aromatic compounds such as tris (4-t-butylphenyl) phosphate and tris (4-cyclohexylphenyl) phosphate; 2-fluorobiphenyl, 3-fluorobiphenyl, 4 -Partially fluorinated products of the above aromatic compounds such as -fluorobiphenyl, 4,4'-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, etc. are preferred. Partially hydrogenated terphenyl, cyclopentylbenzene, cyclohexylbenzene, Cis-1-propyl-4-phenylcyclohexane, trans-1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, t-butylbenzene, t -Amylbenzene, methylphenyl carbonate, diphenyl carbonate, triphenyl phosphate, tris (4-tert-butylphenyl) phosphate, tris (4-cyclohexylphenyl) phosphate, o-cyclohexyl Fluorobenzene, more preferably p- cyclohexyl fluorobenzene, partially hydrogenated member and cyclohexylbenzene terphenyl is particularly preferred.

  Two or more of these may be used in combination. When two or more types are used in combination, in particular, a partially hydrogenated terphenyl, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, or a partially hydrogenated biphenyl, alkylbiphenyl, terphenyl or terphenyl. It is overcharged to use together those selected from oxygen-free aromatic compounds such as cyclohexylbenzene, t-butylbenzene, t-amylbenzene and those selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran. This is preferable from the viewpoint of the balance between prevention characteristics and high-temperature storage characteristics.

The content ratio of these overcharge inhibitors in the non-aqueous electrolyte is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5%. It is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. When the concentration is in the above range, the desired effect of the overcharge inhibitor is easily exhibited, and a decrease in battery characteristics such as high-temperature storage characteristics is suppressed. By including an overcharge inhibitor in the non-aqueous electrolyte, it is possible to suppress the rupture / ignition of the non-aqueous electrolyte secondary battery due to overcharging, and the safety of the non-aqueous electrolyte secondary battery is improved. preferable.

  Other auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate, methoxyethyl-ethyl carbonate, ethoxyethyl-methyl carbonate, ethoxyethyl-ethyl carbonate; dimethyl succinate Diethyl succinate, diallyl succinate, dimethyl maleate, diethyl maleate, diallyl maleate, dipropyl maleate, dibutyl maleate, bis (trifluoromethyl) maleate, bis (pentafluoroethyl) maleate, bis maleate Dicarboxylic acid diester compounds such as (2,2,2-trifluoroethyl); 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10- Tetraoxaspir [5.5] Spiro compounds such as undecane; ethylene sulfite, propylene sulfite, 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone, methyl methanesulfonate, ethyl Methanesulfonate, methyl-methoxymethanesulfonate, methyl-2-methoxyethanesulfonate, busulfan, diethylene glycol dimethanesulfonate, 1,2-ethanediol bis (2,2,2-trifluoroethanesulfonate), 1,4-butanediol Bis (2,2,2-trifluoroethanesulfonate), sulfolane, 3-sulfolene, 2-sulfolene, dimethylsulfone, diethylsulfone, divinylsulfone, diphenylsulfone, bis (methylsulfonyl) methane Sulfur-containing compounds such as bis (methylsulfonyl) ethane, bis (ethylsulfonyl) methane, bis (ethylsulfonyl) ethane, bis (vinylsulfonyl) methane, bis (vinylsulfonyl) ethane; 1-methyl-2-pyrrolidinone, 1 -Nitrogen-containing compounds such as methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; heptane, octane, nonane, decane, cycloheptane, Hydrocarbon compounds such as methylcyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, t-butylcyclohexane, dicyclohexyl; fluorinated benzenes such as fluorobenzene, difluorobenzene, pentafluorobenzene, hexafluorobenzene; 2 Fluorinated toluene such as fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, benzotrifluoride; methyl dimethyl phosphinate, ethyl dimethyl phosphinate, ethyl diethyl phosphinate, trimethyl phosphonoformate, triethyl phosphonoformate, Examples thereof include phosphorus-containing compounds such as trimethylphosphonoacetate, triethylphosphonoacetate, trimethyl-3-phosphonopropionate, and triethyl-3-phosphonopropionate. Among these, ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone, busulfan, 1,4 in terms of improving battery characteristics after high-temperature storage Sulfur-containing compounds such as butanediol bis (2,2,2-trifluoroethanesulfonate) are preferred.

Two or more of these may be used in combination.
The content ratio of these auxiliaries in the non-aqueous electrolyte solution is not particularly limited, but is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, Usually, it is 8 mass% or less, Preferably it is 5 mass% or less, More preferably, it is 3 mass% or less, More preferably, it is 1 mass% or less. The addition of these auxiliaries is preferable in terms of improving capacity maintenance characteristics and cycle characteristics after high-temperature storage. When this concentration is in the above range, the effect of the auxiliary agent is easily exhibited, and the deterioration of battery characteristics such as high load discharge characteristics is suppressed.

[1-6. Gelling agent]
When used in the lithium secondary battery of the present invention, the nonaqueous electrolytic solution is usually present in a liquid state. For example, the nonaqueous electrolytic solution may be gelled with a polymer to form a semi-solid electrolyte. The polymer used for the gelation is arbitrary, and examples thereof include polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyethylene oxide, polyacrylate, and polymethacrylate. In addition, the polymer | macromolecule used for gelatinization may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Moreover, when using a non-aqueous electrolyte as a semi-solid electrolyte, the ratio of the non-aqueous electrolyte in the semi-solid electrolyte is arbitrary as long as the effects of the present invention are not significantly impaired. As a suitable range, the ratio of the non-aqueous electrolyte to the total amount of the semisolid electrolyte is usually 30% by mass or more, preferably 50% by mass or more, more preferably 75% by mass or more, and usually 99.95. It is at most mass%, preferably at most 99 mass%, more preferably at most 98 mass%. If the ratio of the non-aqueous electrolyte is too large, it may be difficult to hold the electrolyte and the liquid may easily leak. Conversely, if it is too small, the charge / discharge efficiency and the capacity may be insufficient.

[1-7. Nonaqueous electrolyte production method]
The non-aqueous electrolyte solution of the present invention dissolves the above-described electrolyte, the compound represented by the general formula (1) of the present invention, and other auxiliary agents used as necessary in the above-described non-aqueous solvent. Can be prepared.
If water is present in the non-aqueous electrolyte, electrolysis of water, reaction between water and lithium metal, hydrolysis of lithium salt, and the like may occur, which is not preferable. Therefore, when preparing the non-aqueous electrolyte solution, it is preferable to dehydrate each component such as a non-aqueous solvent in advance. Specifically, it is preferable to dehydrate until the water content is usually 50 ppm or less, particularly 20 ppm or less. The method of dehydration can be arbitrarily selected, and examples thereof include a method of heating under reduced pressure or passing through a molecular sieve.

[2. Nonaqueous electrolyte secondary battery)
The non-aqueous electrolyte secondary battery of the present invention is the same as the conventionally known non-aqueous electrolyte secondary battery except for the non-aqueous electrolyte, and is usually impregnated with the non-aqueous electrolyte of the present invention. The positive electrode and the negative electrode are laminated via a porous film (separator), and these are housed in a case (exterior body). The shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

[2-1. Non-aqueous electrolyte)
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix and use other nonaqueous electrolyte solution with respect to the nonaqueous electrolyte solution of this invention.
[2-2. Negative electrode)
The negative electrode active material used for the negative electrode is described below. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.

<Negative electrode active material>
Examples of the negative electrode active material include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like.
Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. .
(1) Examples of natural graphite include scaly graphite, scaly graphite, soil graphite, and / or graphite particles obtained by subjecting these graphites to spheroidization or densification. Among these, spherical or ellipsoidal graphite subjected to spheroidizing treatment is particularly preferable from the viewpoints of particle filling properties and charge / discharge rate characteristics.

As an apparatus used for the spheroidization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and mechanical action such as impact compression, friction, shearing force, etc. on the carbon material introduced inside the rotor by rotating at high speed. And a device for performing the spheroidizing treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the carbon material.
For example, when the spheroidizing treatment is performed using the above-described apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / second, more preferably 40 to 100 m / second, and 50 to 100 m / second. More preferably. 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.

  (2) Artificial graphite includes coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are usually in the range of 2500 ° C. or higher and usually 3200 ° C. or lower. Examples thereof include those produced by graphitization at a temperature and, if necessary, pulverized and / or classified. At this time, a silicon-containing compound or a boron-containing compound can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in the heat treatment process of pitch can be mentioned. Furthermore, the artificial graphite of the granulated particle which consists of primary particles is also mentioned. For example, by mixing mesocarbon microbeads and graphitizable carbonaceous material powders such as coke, graphitizable binders such as tar and pitch, and graphitization catalyst, graphitizing, and pulverizing as necessary Examples of the resulting graphite particles include a plurality of flat particles and aggregated or bonded so that the orientation planes are non-parallel.

(3) As amorphous carbon, amorphous carbon that has been heat-treated at least once in a temperature range (400 to 2200 ° C.) in which no graphitizable carbon precursor such as tar or pitch is used as a raw material. Examples thereof include amorphous carbon particles that are heat-treated using particles or a non-graphitizable carbon precursor such as a resin as a raw material.
(4) Carbon-coated graphite can be obtained by mixing natural graphite and / or artificial graphite with a carbon precursor that is an organic compound such as tar, pitch, or resin, and heat-treating it at least once in the range of 400 to 2300 ° C. Examples thereof include a carbon graphite composite in which natural graphite and / or artificial graphite is used as nuclear graphite, and amorphous carbon coats the nuclear graphite. The composite form may cover the entire surface or a part thereof, or may be a composite of a plurality of primary particles using carbon originating from the carbon precursor as a binder. Carbon can also be deposited (CVD) by reacting natural graphite and / or artificial graphite with hydrocarbon gases such as benzene, toluene, methane, propane, and aromatic volatiles at a high temperature to deposit carbon on the graphite surface. A graphite composite can also be obtained.

(5) As graphite-coated graphite, natural graphite and / or artificial graphite and a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin are mixed and once in a range of about 2400 to 3200 ° C. Examples thereof include graphite-coated graphite in which natural graphite and / or artificial graphite obtained by heat treatment is used as nuclear graphite, and graphitized material covers the whole or part of the surface of nuclear graphite.
(6) As the resin-coated graphite, natural graphite and / or artificial graphite obtained by mixing natural graphite and / or artificial graphite with a resin and drying at a temperature of less than 400 ° C. is used as nuclear graphite, and the resin is nuclear graphite. And resin-coated graphite covering the surface.
Moreover, the carbonaceous material of (1)-(6) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

Examples of organic compounds such as tar, pitch and resin used in the above (2) to (5) include coal-based heavy oil, direct-current heavy oil, cracked heavy petroleum oil, aromatic hydrocarbon, N-ring compound. , S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and carbonizable organic compound selected from the group consisting of thermosetting resins. The raw material organic compound may be used after being dissolved in a low molecular organic solvent in order to adjust the viscosity at the time of mixing.

Moreover, as natural graphite and / or artificial graphite used as a raw material of nuclear graphite, natural graphite subjected to spheroidization treatment is preferable.
As an alloy material used as the negative electrode active material, as long as lithium can be occluded / released, lithium alone, simple metals and alloys forming lithium alloys, or oxides, carbides, nitrides, silicides, sulfides thereof Any of compounds such as products or phosphides may be used and is not particularly limited. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably aluminum, silicon and tin single metals and An alloy or compound containing these atoms. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

<Physical properties of carbonaceous materials>
When using a carbonaceous material as a negative electrode active material, it is desirable to have the following physical properties.
(X-ray parameters)
The d-value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of carbonaceous materials is usually 0.335 nm or more, usually 0.360 nm or less, and 0.350 nm. The following is preferable, and 0.345 nm or less is more preferable. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(Volume-based average particle size)
The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) obtained by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 7 μm. The above is particularly preferable, and is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less.

If the volume-based average particle size is below the above range, the irreversible capacity may increase, leading to loss of initial battery capacity. On the other hand, when the above range is exceeded, when an electrode is produced by coating, an uneven coating surface tends to be formed, which may be undesirable in the battery production process.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is performed using a meter (for example, LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(Raman R value)
The Raman R value of the carbonaceous material is a value measured using a laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1. 5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

When the Raman R value is lower than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the sites where Li enters the interlayer are reduced along 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 the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

The Raman spectrum is measured using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), and the sample is naturally dropped into the measurement cell and filled, and an argon ion laser beam (or semiconductor) is applied to the sample surface in the cell. While irradiating a laser beam, the cell is rotated in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and measuring the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention.

Moreover, said Raman measurement conditions are as follows.
・ Laser wavelength: Ar ion laser 514.5 nm (semiconductor laser 532 nm)
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
-Raman R value: background processing,
-Smoothing processing: Simple average, 5 points of convolution

(BET specific surface area)
BET specific surface area of the carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m ² · ^{g -1} or more, 0.7 m ² · ^{g -1} or more, 1. 0 m ² · ^{g -1} or more, and particularly preferably 1.5 m ² · ^{g -1} or more, generally not more than 100 m ² · ^{g -1,} preferably ^{25 m} 2 · ^{g -1} or less, 15 m ² · g ^-1 more preferably less, ^{10 m} 2 · ^{g -1} or less are especially preferred.

When the value of the BET 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, lithium is likely to precipitate on the electrode surface, and stability may be reduced. 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.
The specific surface area is measured by the BET method using a surface area meter (for example, a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas that is accurately adjusted so that the relative pressure value of nitrogen is 0.3, the nitrogen adsorption BET one-point method is performed by a gas flow method.

(Roundness)
When the circularity is measured as the degree of the sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere.
The circularity of the particles having a particle size of 3 to 40 μm in the range of the carbonaceous material is desirably closer to 1, and is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more, 0.85 or more is more preferable, and 0.9 or more is particularly preferable. High current density charge / discharge characteristics improve as the degree of circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity is measured using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm.

  The method for improving the circularity is not particularly limited, but a sphere-shaped sphere is preferable because the shape of the interparticle void when the electrode body is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by the binder or the adhesive force of the particles themselves, etc. Is mentioned.

(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 1 g · cm ⁻³ or more. Particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.8 g · cm ⁻³ or less is more preferable, and 1.6 g · cm ⁻³ or less is particularly preferable. When the tap density is below the above 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, when the above range is exceeded, there are too few voids between the particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.
The tap density is measured by passing through a sieve having an opening 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 device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample.

(Orientation ratio)
The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is below the above range, the high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.
The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molding obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(Aspect ratio (powder))
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.
The aspect ratio is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Carbonaceous material particles when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A and the shortest diameter B orthogonal thereto are measured, and the average value of A / B is obtained.

<Configuration and production method of negative electrode>
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. 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.
In the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.
(Electrode density)

The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more. but more preferably, particularly preferably 1.3 g · ^{cm -3} or more, preferably 2.2 g · ^{cm -3} or less, more preferably 2.1 g · ^{cm -3} or less, 2.0 g · ^{cm -3} or less Further preferred is 1.9 g · cm ⁻³ or less. When the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases or non-aqueous system near the current collector / negative electrode active material interface. There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the electrolytic solution. On the other hand, if the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

[2-3. (Positive electrode)
<Positive electrode active material>
The positive electrode active material (lithium transition metal compound) used for the positive electrode is described below.
<Lithium transition metal compound>
A lithium transition metal compound is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides. Examples of sulfides include compounds having a two-dimensional layered structure such as TiS ₂ and MoS ₂ , and strong compounds represented by the general formula Me _x Mo ₆ S ₈ (Me is various transition metals including Pb, Ag, and Cu). Examples thereof include a sugar compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMePO ₄ (Me is at least one or more transition metals), specifically LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples include LiMnPO ₄ . Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiMe ₂ O ₄ (Me is at least one transition metal), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like. Those having a layered structure are generally expressed as LiMeO ₂ (Me is at least one transition metal). LiCoO _{2 Specifically, LiNiO 2, LiNi 1-x} Co x O 2, LiNi 1-x-y Co x Mn y O 2, LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0. _{4 Mn 0.4 O 2, Li 1.2} Cr 0.4 Ti 0.4 O 2, such as LiMnO ₂ and the like.

<composition>
The lithium-containing transition metal compound is, for example, a lithium transition metal compound represented by the following composition formula (A) or (B).
1) In the case of a lithium transition metal compound represented by the following composition formula (A)
Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. In addition, the rich portion of Li represented by x may be replaced with the transition metal site M.

  In the composition formula (A), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. Moreover, x in the said compositional formula is the preparation composition in the manufacture stage of a lithium transition metal type compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, x may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

A lithium transition metal-based compound is excellent in battery characteristics when fired at a high temperature in an oxygen-containing gas atmosphere in order to enhance the crystallinity of the positive electrode active material.
Further, the lithium transition metal-based compound represented by the composition formula (A) may be a solid solution with Li ₂ MO ₃ called a 213 layer, as shown in the general formula (A ′) below.
αLi ₂ MO ₃ · (1-α) LiM′O ₂ (A ′)
In the general formula, α is a number satisfying 0 <α <1.

M is at least one metallic element average oxidation number of 4 ^+, specifically, at least one metal element Mn, Zr, Ti, Ru, selected from the group consisting of Re and Pt.
M 'is at least one metallic element average oxidation number of 3 ^+, preferably, V, Mn, Fe, at least one metallic element selected from the group consisting of Co and Ni, more preferably , At least one metal element selected from the group consisting of Mn, Co and Ni.

2) A lithium transition metal compound represented by the following general formula (B).
_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)
However, M is an element comprised from at least 1 sort (s) of the transition metals chosen from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg.
The value of b is usually 0.4 or more and 0.6 or less.
When the value of b is within this range, the energy density per unit weight in the lithium transition metal compound is high.

The value of a is usually 0 or more and 0.3 or less. Moreover, a in the above composition formula is a charged composition in the production stage of the lithium transition metal compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, a may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.
When the value of a is within this range, the energy density per unit weight in the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.
Furthermore, the value of δ is usually in the range of ± 0.5.
If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are good.

Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound, will be described in more detail below.
In order to obtain a and b in the composition formula of the lithium transition metal compound, each transition metal and lithium are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn. It is calculated by the thing.

From a structural point of view, it is considered that lithium related to a is substituted for the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.
Further, the lithium transition metal based compound may be substituted with fluorine, it is expressed as _{LiMn 2 O 4-x F 2x} .

<blend>
Specific examples of the lithium transition metal compound having the above composition include, for example, Li _{1 + x} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + x} Ni _0.85 Co _0.10 Al _0.05 O ₂ , Li _{1 + x
Ni 0.33 Mn 0.33 Co 0.33 O 2} , Li 1 + x Ni 0.45 Mn 0.45 Co 0.1 O 2, Li 1 + x Mn 1.8 Al 0.2 O 4, Li 1 + x Mn 1. ₅ Ni _0.5 O ₄ or the like. These lithium transition metal compounds may be used alone or in a blend of two or more.

<Introduction of foreign elements>
Moreover, a different element may be introduce | transduced into a lithium transition metal type compound. As the different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si, and Sn. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.

[Positive electrode for lithium secondary battery]
The positive electrode for a lithium secondary battery is formed by forming a positive electrode active material layer containing the above-described lithium transition metal compound powder for a lithium secondary battery positive electrode material and a binder on a current collector.
The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.

As the material for the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc. In addition, you may form a thin film suitably in mesh shape.
When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but a range of usually 1 μm or more and 100 mm or less is suitable. If it is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

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 is stable with respect to the liquid medium used during electrode production may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene・ Rubber polymers such as propylene rubber, styrene / butadiene / styrene block copolymers and hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymers), styrene / ethylene / butadiene / ethylene copolymers, Styrene / isoprene styrene bromide Copolymer and its hydrogenated thermoplastic elastomeric polymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. 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 and 80% by mass or less. If the proportion 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. Battery capacity and conductivity may be reduced.
The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. And carbon materials. 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 proportion of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  As a liquid medium for forming a slurry, it is possible to dissolve or disperse a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickener used as necessary. If it is a solvent, there is no restriction | limiting in particular in the kind, You may use either an aqueous solvent or an organic solvent. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a slurry such as SBR is slurried. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The content ratio of the lithium transition metal-based compound powder as the positive electrode material in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.
The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

The electrode density after pressing the positive electrode is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.
Thus, a positive electrode for a lithium secondary battery can be prepared.

[2-4. (Separator)
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention is used. Is preferred.

  As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. 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 above-described 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, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

The characteristics of the separator in the non-electrolyte secondary battery can be grasped by the Gurley value. The Gurley value indicates the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. It means that it is harder to go through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means lower communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator of the present invention is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous lithium secondary battery, a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance. Although the Gurley value of a separator is arbitrary, Preferably it is 10-1000 second / 100ml, More preferably, it is 15-800 second / 100ml, More preferably, it is 20-500 second / 100ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

[Battery design]
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

  When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<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 non-aqueous 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 an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve 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>
Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

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 non-aqueous electrolyte solution>
[Examples 1 to 3, Comparative Examples 1 to 4]
A mixture of ethylene carbonate (hereinafter referred to as EC), diethyl carbonate (hereinafter referred to as DEC), and ethyl methyl carbonate (hereinafter referred to as EMC) as a cyclic carbonate (volume ratio 2: 5: 3) in a dry argon atmosphere. ) LiPF ₆ that was sufficiently dried was added to 1 mol / L, and vinylene carbonate was added thereto at 2 wt% with respect to the entire non-aqueous electrolyte. An electrolyte solution was prepared by adding the following compounds in the amounts shown in the table to the original electrolyte solution. However, the original electrolyte solution was used for the comparative example.

<Preparation of positive electrode>
95% by mass of Ni-containing lithium transition metal oxide as a positive electrode active material, 2.5% by mass of acetylene black as a conductive material, and 2.5% by mass of polyvinylidene fluoride (PVdF) as a binder, -Mixed in a methylpyrrolidone solvent and slurried. The obtained slurry was applied to both sides of an aluminum foil, dried, and rolled to a thickness of 60 μm with a press machine, and cut into an active material having a width of 30 mm and a length of 40 mm to form a positive electrode. The prepared positive electrode was used after being dried under reduced pressure at 80 degrees Celsius for 12 hours.

<Production of carbon anode>
98 parts by mass of graphite powder as the negative electrode active material, 1 part by mass of aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) as the thickener and binder, respectively, and aqueous dispersion of styrene-butadiene rubber 1 part by mass (concentration of styrene-butadiene rubber 50% by mass) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to both sides of the copper foil, dried, and rolled to a thickness of 75 μm with a press. This was cut out so that the active material had a width of 30 mm and a length of 40 mm to form a negative electrode. The prepared negative electrode was dried under reduced pressure at 60 degrees Celsius for 12 hours.

<Production of secondary battery>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the positive electrode, the separator, the negative electrode, the separator, and the positive electrode to produce a battery element. This battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and then 0.4 mL of non-aqueous electrolyte was put into the bag. This was injected and vacuum sealed to produce a sheet battery. Furthermore, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.

<Battery evaluation>
1. Cycle characteristics after exposure to high temperature conditions in the charged state 1 (Table-1)
The sheet-like battery was stabilized by charging and discharging several cycles at a constant current corresponding to 0.2 C at 25 ° C. with a charge end voltage of 4.2 V and a discharge end voltage of 2.5 V. Thereafter, the battery was left in a constant temperature bath at 80 ° C. for 3 days while being charged to 4.2V. Furthermore, a cycle test was performed using this battery. In the cycle test, the battery was charged to 4.2 V at 0.5 C, and 2.
Discharging to 5V was repeated at 45 ° C. Table 1 shows values (cycle maintenance ratios) of the battery capacity after 100 cycles of the cycle test expressed as a ratio (%) to the capacity before the cycle test.

In contrast to Comparative Example 1, in Examples 1 and 2 using the electrolytic solution of the present invention, it can be seen that the cycle retention rate is good even after exposure to high temperature conditions. On the other hand, in Comparative Example 2 or Comparative Example 3 using Compound C or Compound D of the prior art, the effect is recognized as compared with Comparative Example 1, but in Examples 1 and 2 using the electrolytic solution of the present invention, It can be seen that the effect is small when compared.
2. Cycle characteristics after exposure to high temperature conditions in the charged state 2 (Table-2)
The sheet-like battery was stabilized by charging and discharging several cycles at a constant current corresponding to 0.2 C at 25 ° C. with a charge end voltage of 4.2 V and a discharge end voltage of 2.5 V. Thereafter, the battery was left in a constant temperature bath at 60 ° C. for 3 days while being charged at 4.1 V. Furthermore, a cycle test was performed using this battery. In the cycle test, charging at 0.5C to 4.2V and discharging at 0.5C to 2.5V were repeated at 45 ° C. Table 2 shows the values (cycle maintenance ratio) of the battery capacity after 100 cycles of the cycle test expressed as a percentage (%) of the capacity before the cycle test.
Shown in

The experimental example in Table-2 differs in voltage and temperature when exposed to high temperature conditions compared to the experimental example in Table-1. Therefore, it is expected that the coating state on the electrode surface is different, and the cycle maintenance rates of Comparative Example 1 and Comparative Example 4 are different. Even in such a situation, it can be seen that in Example 3 using the electrolytic solution of the present invention, the cycle retention rate is good even after exposure to high temperature conditions as compared with Comparative Example 4. Further, since compound B is a compound in which L in formula (1) is not directly bonded to an oxygen atom, it can be seen that L is effective whether or not it is directly bonded to an oxygen atom. .
<Preparation of non-aqueous electrolyte solution>
[Examples 4 to 5, Comparative Example 5]
In a dry argon atmosphere, sufficient for a mixture (volume ratio 1: 4: 5) of ethylene carbonate (hereinafter referred to as EC), diethyl carbonate (hereinafter referred to as DEC), and propylene carbonate (hereinafter referred to as PC) The dried LiPF ₆ was added to 1.2 mol / L, vinylene carbonate was added at 1.5 wt% with respect to the entire non-aqueous electrolyte, and lithium difluorophosphate was added to the non-aqueous electrolyte at a concentration of 0.1 wt / L. 5 wt% was added. An electrolyte solution was prepared by adding the following compounds in the amounts shown in the table to the original electrolyte solution. However, the original electrolyte solution was used for the comparative example.

<Production of secondary battery>
The secondary battery was made in the same manner as in Example 1.
<Battery evaluation>
1. Cycle characteristics after exposure to high temperature conditions in the charged state 1 (Table-1)
The sheet-like battery was stabilized by charging and discharging several cycles at a constant current corresponding to 0.2 C at 25 ° C. with a charge end voltage of 4.2 V and a discharge end voltage of 2.5 V. Thereafter, the battery was left in a constant temperature bath at 80 ° C. for 3 days while being charged to 4.2V. Furthermore, a cycle test was performed using this battery. In the cycle test, the battery was charged to 4.2 V at 0.5 C, and 2.
Discharging to 5V was repeated at 45 ° C. Table 3 shows the values (cycle maintenance ratio) of the battery capacity after 100 cycles of the cycle test expressed as a percentage (%) to the capacity before the cycle test.

In contrast to Comparative Example 5, in Examples 4 and 5 using the electrolytic solution of the present invention, it can be seen that the cycle retention rate is good even after exposure to high temperature conditions. In contrast to Comparative Example 5, in Examples 4 and 5 using the electrolytic solution of the present invention, it can be seen that the cycle retention rate is good even after exposure to high temperature conditions. Further, since compound E is a group in which R in formula (1) contains an unsaturated bond, it can be seen that R is effective whether or not it contains an unsaturated bond.
From these experimental results, it can be said that by using the electrolytic solution of the present invention, a battery having excellent battery characteristics can be obtained even after being exposed to high temperature conditions.

According to the non-aqueous electrolyte solution of the present invention, the decomposition of the electrolyte solution of the non-aqueous electrolyte secondary battery is suppressed, and when the battery is used in a high temperature environment, gas generation and deterioration of the battery are suppressed and a high energy density. The non-aqueous electrolyte secondary battery can be manufactured. Therefore, it can be suitably used in various fields such as an electronic device in which a non-aqueous electrolyte secondary battery is used.
The use of the non-aqueous electrolyte for secondary batteries and the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. 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 notebook, calculator, memory card, portable tape recorder, radio, backup power supply, motor, automobile, motorcycle, motorbike, bicycle, lighting equipment, toy, game equipment, clock, electric tool, strobe, camera, home-use large A storage battery etc. can be mentioned.

Claims (5)

A non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of occluding and releasing metal ions and a negative electrode having a negative electrode active material capable of occluding and releasing metal ions. A non-aqueous electrolyte containing a compound represented by the following general formula (1):

(In the formula, L represents an aliphatic and Z-valent linking group having a ring structure, Z is an integer of 2 or more, and Z Rs are each independently an alkyl group, an alkenyl group, an alkynyl group, or Represents an aryl group, and R may have a halogen atom.)   The non-aqueous electrolyte solution according to claim 1, wherein the linking group L in the formula (1) has a cyclopentane ring or a cyclohexane ring as a ring structure. The non-aqueous electrolyte solution according to claim 1 or 2, wherein the linking group L in the formula (1) is any of the following.

  Cyclic carbonate having unsaturated bond in non-aqueous electrolyte, cyclic carbonate having fluorine atom, acid anhydride, isocyanate, nitrile, difluorophosphate, monofluorophosphate, lithium bisoxalatoborate, lithium difluorooxalato The non-aqueous electrolyte solution according to any one of claims 1 to 3, comprising at least one of borates.   A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of occluding and releasing metal ions and a negative electrode having a negative electrode active material capable of occluding and releasing metal ions, A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution according to any one of the above.