JP6582730B2 - Non-aqueous electrolyte and non-aqueous electrolyte secondary battery using the same - Google Patents

Description

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

  Lithium non-aqueous electrolyte secondary batteries that use lithium-containing transition metal oxides as positive electrodes and non-aqueous solvents as electrolytes can achieve high energy density, so they can be used from small power sources such as mobile phones and laptop computers to automobiles. It is applied to a wide range of applications, from large power supplies for railways and road leveling. However, in recent years, there has been an increasing demand for higher performance of non-aqueous electrolyte secondary batteries, and there is a strong demand for improvement of various characteristics.

Lithium non-aqueous electrolyte secondary batteries include cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, and cyclic carboxyls such as γ-butyrolactone and γ-valerolactone. Non-aqueous solvents of acid esters, chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate; LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO _3, and LiN (CF ₃ SO ₂ ) A non-aqueous electrolyte containing a solute such as ₂ is used.

  In the non-aqueous electrolyte secondary battery using such a non-aqueous electrolyte, the reactivity varies depending on the composition of the non-aqueous electrolyte, and thus the battery characteristics are greatly changed by the non-aqueous electrolyte. In order to improve battery characteristics such as load characteristics, cycle characteristics and storage characteristics of non-aqueous electrolyte secondary batteries, and to improve battery safety during overcharge, various studies have been conducted on non-aqueous solvents and electrolytes. Has been made.

  Patent Document 1 discloses a technology for suppressing self-discharge during high-temperature storage by using an electrolytic solution to which tricarbimide is added in a non-aqueous electrolytic battery using lithium-containing cobalt dioxide as a positive electrode active material. Yes.

  Patent Document 2 discloses a technique for obtaining a battery excellent in load characteristics even after high-temperature storage by suppressing reductive decomposition of a solvent by using a nonaqueous electrolytic solution containing an isocyanuric acid derivative.

  Patent Document 3 discloses a battery represented by the flame retardancy of an electrolytic solution by using a non-aqueous electrolytic solution containing a phosphite ester and a compound having two or more polymerizable functional groups in the molecule at the same time. A technology that achieves both safety and battery cycle characteristics is disclosed.

JP-A-7-192757 JP 2000-348705 A JP 2010-282906 A

However, in recent years, the demand for improving the characteristics of non-aqueous electrolyte secondary batteries is increasing, and it is required to have various performances at a high level, but it has not been achieved yet. Among them, there is a problem that it is difficult to achieve both high temperature life and suppression of deterioration of large current capacity after standing at high temperature.
According to the study of the inventors of the present invention, in a non-aqueous electrolyte secondary battery not using a specific positive electrode, as described above, when a non-aqueous electrolyte containing an isocyanuric acid derivative or the like is used, the inside of the battery It has been found that the resistance increases remarkably and the large current capacity after being left at high temperature is significantly impaired.

The present invention has been made in view of the above-described problems. That is, an object of the present invention is to provide a battery having an excellent high-temperature life without impairing a large current capacity after being left at a high temperature for a non-aqueous electrolyte secondary battery.
As a result of intensive studies, the inventors of the present invention have found that in a non-aqueous electrolyte secondary battery using a specific positive electrode, the above problem can be solved by including a specific compound in the electrolytic solution. The present invention has been completed.

The gist of the present invention is as follows.
[1]
A transition metal oxide capable of occluding and releasing metal ions, comprising at least Ni and Co, and a positive electrode containing a transition metal oxide in which 50 mol% or more of the transition metals is Ni and Co;
A negative electrode capable of occluding and releasing metal ions;
A non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a non-aqueous solvent and a non-aqueous electrolyte containing an electrolyte dissolved in the non-aqueous solvent,
A non-aqueous electrolyte containing a compound having a structure represented by the following general formula (1).

(In the formula ^(1), R 1 ~R ^3, which may be the being the same or different, is an organic group having 1 to 20 carbon atoms that may have a substituent. However, R ¹ at least one of to R ³ is a carbon - carbon unsaturated bond or a cyano group).
[2]
In the general formula (1), R ^{1 to} R ³ may be the same as or different from each other, and are an optionally substituted organic group having 1 to 10 carbon atoms, [1] The non-aqueous electrolyte solution described in 1.
[3]
In the general formula (1), at least one of R ^{1 to} R ³ is the non-aqueous electrolyte solution according to [1] or [2], which is an organic group having a carbon-carbon unsaturated bond.
[4]
The non-aqueous system according to any one of [1] to [3], wherein in the general formula (1), the organic group having a carbon-carbon unsaturated bond is a group selected from the group consisting of an allyl group and a methallyl group. Electrolytic solution.
[5]
Any one of [1] to [4], wherein the compound having the structure represented by the general formula (1) is contained in an amount of 0.01% by mass or more and 10.0% by mass or less with respect to the total amount of the nonaqueous electrolytic solution. The non-aqueous electrolyte solution described in 1.
[6]
From cyclic carbonate having fluorine atom, cyclic carbonate having carbon-carbon unsaturated bond, difluorophosphate, fluorosulfate, compound having isocyanato group, compound having cyano group, cyclic sulfonate ester, and dicarboxylic acid complex salt The nonaqueous electrolytic solution according to any one of [1] to [5], which contains at least one compound selected from the group consisting of:
[7]
The nonaqueous electrolytic solution according to any one of [1] to [6], which contains a cyclic carbonate and a chain carbonate as the nonaqueous solvent, and contains at least two types of chain carbonates as the chain carbonate.
[8]
[1] to [7], wherein the transition metal oxide containing at least Ni and Co and 50 mol% or more of the transition metals is Ni and Co is represented by the following composition formula (2): Non-aqueous electrolyte.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ (2)
(In formula (2), 0.9 ≦ a1 ≦ 1.1, 0.3 ≦ b1 ≦ 0.9, 0.1 ≦ c1 ≦ 0.5, 0.0 ≦ d1 ≦ 0.5 are shown. 0.5 ≦ b1 + c1 and b1 + c1 + d1 = 1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)
[9]
The transition metal oxide containing at least Ni and Co, wherein 50 mol% or more of the transition metals is Ni and Co is represented by the following composition formula (3), according to any one of [1] to [7] Non-aqueous electrolyte.
Li _a2 Ni _b2 Co _c2 M _d2 O ₂ (3)
(In formula (3), 0.9 ≦ a2 ≦ 1.1, 0.3 ≦ b2 ≦ 0.9, 0.1 ≦ c2 ≦ 0.5, 0.0 ≦ d2 ≦ 0.5 C2 ≦ b2 and 0.6 ≦ b2 + c2 and b2 + c2 + d2 = 1, where M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
[10]
A transition metal oxide capable of occluding and releasing metal ions, comprising at least Ni and Co, and a positive electrode containing a transition metal oxide in which 50 mol% or more of the transition metals is Ni and Co;
A negative electrode capable of occluding and releasing metal ions;
A non-aqueous electrolyte secondary battery comprising a non-aqueous solvent and a non-aqueous electrolyte containing an electrolyte dissolved in the non-aqueous solvent, wherein the non-aqueous electrolyte is any one of [1] to [9] A nonaqueous electrolyte secondary battery, characterized by being a nonaqueous electrolyte solution.

  According to the nonaqueous electrolytic solution of the present invention, it is possible to provide a battery having an excellent high temperature life without impairing a large current capacity after being left at a high temperature.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is limited to these specific contents. However, various modifications can be made within the scope of the invention.

[1. Non-aqueous electrolyte]
The nonaqueous electrolytic solution of the present invention is a compound having a structure represented by the following general formula (1) (hereinafter referred to as “specific compound”) in a nonaqueous electrolytic solution containing a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent. A non-aqueous electrolyte solution characterized in that

(In the formula ^(1), R 1 ~R ^3, which may be the being the same or different, is an organic group having 1 to 20 carbon atoms that may have a substituent. However, R ¹ at least one of to R ³ is a carbon - carbon unsaturated bond or a cyano group).

<1-1. Electrolyte>
The electrolyte used for the non-aqueous electrolyte solution of the present invention is not particularly limited, and can be arbitrarily adopted depending on the intended non-aqueous electrolyte secondary battery. It is preferable to use a lithium salt as the electrolyte.

Specific examples of the electrolyte include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ and LiAlF ₄ ; LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , _{LiN (C 2 F 5 SO 2} ) 2, LiN (CF 3 SO 2) (C 2 F 5 SO 2), LiN (CF 3 SO 2) (C 3 F 7 SO 2), LiN (CF 3 SO 2) (FSO ₂ ), lithium cyclic 1,2-ethanedisulfonylimide, lithium cyclic 1,3-propanedisulfonylimide, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedi sulfonyl imide, lithium cyclic 1,4-perfluorobutane _{disulfonylimide, LiC (CF 3 SO 2)} 3, LiPF 4 (CF 3) 2, LiPF 4 (C 2 _{5) 2, LiPF 4 (CF} 3 SO 2) 2, LiPF 4 (C 2 F 5 SO 2) 2, LiBF 3 (CF 3), LiBF 3 (C 2 F 5), LiBF 2 (CF 3) 2, Fluorine-containing organic lithium salts such as LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ ; KPF ₆ , NaPF ₆ , NaBF ₄ , CF ₃ Sodium salt or potassium salt such as SO ₃ Na;

Among these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoro Ethanedisulfonylimide is preferred, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (FSO ₂ ) are more preferred, LiPF ₆ , LiBF ₄ or LiN (CF ₃ SO ₂ ) ₂ is preferred.

These electrolytes may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Of these, the combined use of two inorganic lithium salts and the combined use of an inorganic lithium salt and a fluorine-containing organic lithium salt are preferable because gas generation during continuous charging or deterioration after high-temperature storage is effectively suppressed.
In particular, the combination and the LiPF ₆ and LiBF _4, and an inorganic lithium salt such as _{LiPF 6, LiBF 4, LiN (} FSO 2) 2, LiN (CF 3 SO 2) 2, LiN (CF 3 SO 2) (FSO 2 ) And a fluorine-containing organic lithium salt such as LiN (C ₂ F ₅ SO ₂ ) ₂ are preferred.

When LiPF ₆ and LiBF ₄ are used in combination, the proportion of LiBF _{4 in} the entire electrolyte is preferably 0.001% by mass or more and 20% by mass or less. Within this range, the resistance of the non-aqueous electrolyte solution can be suppressed due to the low degree of dissociation of LiBF ₄ .

On the other hand, when inorganic lithium salts such as LiPF ₆ and LiBF ₄ are used in combination with fluorine-containing organic lithium salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ The proportion of the inorganic lithium salt in the entire electrolyte is preferably 70% by mass or more and 99.9% by mass or less. Within this range, the ratio of the fluorine-containing organic lithium salt having a large molecular weight is generally too high compared to the inorganic lithium salt, and the ratio of the non-aqueous solvent in the entire non-aqueous electrolyte decreases, resulting in non-aqueous electrolysis. An increase in the resistance of the liquid can be suppressed.

  The concentration of the electrolyte such as a lithium salt in the final composition of the nonaqueous electrolytic solution of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired, but preferably 0.5 mol / L or more and 3 mol / L or less. It is. If the electrolyte concentration is above this lower limit, sufficient ionic conductivity of the non-aqueous electrolyte solution can be easily obtained, and if it is lower than the upper limit, it is avoided that the viscosity is excessively increased, and good ionic conductivity is obtained. It is easy to ensure the performance of the nonaqueous electrolyte secondary battery using the nonaqueous electrolyte solution. The concentration of the electrolyte such as lithium salt is more preferably in the range of 0.6 mol / L or more, further preferably 0.8 mol / L or more, more preferably 2 mol / L or less, more preferably 1.5 mol / L or less. It is.

In particular, when the non-aqueous solvent of the non-aqueous electrolyte is mainly composed of a carbonate compound such as alkylene carbonate or dialkyl carbonate, LiPF ₆ may be used alone, but when used together with LiBF ₄ , capacity deterioration due to continuous charging is suppressed. Therefore, it is preferable. When these are used in combination, the amount of LiBF ₄ used relative to 1 mol of LiPF ₆ is preferably 0.005 mol or more and 0.4 mol or less. If it is less than this upper limit, it is easy to avoid the battery characteristics after high temperature storage from being lowered, and if it is more than the lower limit, gas generation and capacity deterioration during continuous charging are easily avoided. The amount of LiBF ₄ used is preferably 0.01 mol or more, particularly preferably 0.05 mol or more, and preferably 0.2 mol or less with respect to 1 mol of LiPF ₆ .

<1-2. Nonaqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte of the present invention is not particularly limited as long as it does not adversely affect the battery characteristics when it is used as a battery, but it is one or more of the non-aqueous solvents listed below. Preferably there is.
Examples of non-aqueous solvents include chain carbonates and cyclic carbonates, chain carboxylic acid esters and cyclic carboxylic acid esters, chain ethers and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and boron-containing organic solvents. It is done.

  The kind of chain carbonate is not particularly limited, and examples thereof include dialkyl carbonates. Among them, the number of carbon atoms of the alkyl group is preferably 1 to 5, and more preferably 1 to 4, more preferably 1 Those of ˜3 are particularly preferred. Specific examples include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate and the like.

Among these, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.
Further, chain carbonates having a fluorine atom (hereinafter sometimes referred to as “fluorinated chain carbonate”) can also be suitably used. Although the number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, it is usually 6 or less, preferably 4 or less, more preferably 3 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate, fluorinated ethyl methyl carbonate, and fluorinated diethyl carbonate.

Examples of the fluorinated dimethyl carbonate include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, and bis (trifluoromethyl) carbonate.
As fluorinated ethyl methyl carbonate, 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trifluoro Examples include ethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

  As fluorinated diethyl carbonate, ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2-trifluoroethyl) ) Carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2,2,2 -Trifluoroethyl-2 ', 2'-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate and the like.

  In addition, a fluorinated chain carbonate expresses an effective function not only as a solvent but also as an additive described in 1-4 below. When the fluorinated chain carbonate is used as a solvent and additive, there is no clear boundary in the blending amount, and the described blending amount can be followed as it is.

  The kind of cyclic carbonate is not particularly limited, and examples thereof include alkylene carbonate. Among them, the number of carbon atoms of the alkylene group constituting is preferably 2 to 6, particularly preferably 2 to 4. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate (2-ethylethylene carbonate, cis and trans 2,3-dimethylethylene carbonate) and the like.

Among these, ethylene carbonate or propylene carbonate is preferable, and ethylene carbonate is particularly preferable because the resistance of the non-aqueous electrolyte secondary battery can be reduced due to the high dielectric constant.
Further, cyclic carbonates having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated cyclic carbonate”) can also be suitably used.

  Examples of the fluorinated cyclic carbonate include cyclic carbonates having a fluorinated alkylene group having 2 to 6 carbon atoms, such as fluorinated ethylene carbonate and derivatives thereof. Examples of the fluorinated ethylene carbonate and derivatives thereof include ethylene carbonate or a fluorinated product of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms). Fluoride of ethylene carbonate is preferred.

  Specifically, monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4- Fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethyl Le ethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate.

  Among these, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, and 4,5-difluoro-4,5-dimethylethylene carbonate is more preferable. As 4,5-difluoroethylene carbonate, a trans isomer is preferable to a cis isomer. This is to provide high ionic conductivity and to suitably form an interface protective film.

  In addition, a fluorinated cyclic carbonate expresses an effective function not only as a solvent but also as an additive described in 1-4 below. When the fluorinated cyclic carbonate is used as a solvent and additive, there is no clear boundary, and the described amount can be followed as it is.

  The type of the chain carboxylic acid ester is not particularly limited. For example, methyl acetate, ethyl acetate, acetic acid-n-propyl, acetic acid-i-propyl, acetic acid-n-butyl, acetic acid-i-butyl, acetic acid-t-butyl , Methyl propionate, ethyl propionate, propionate-n-propyl, propionate-i-propyl, propionate-n-butyl, propionate-i-butyl, propionate-t-butyl, methyl butyrate, ethyl butyrate, etc. Is mentioned.

  Among these, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate are preferable in terms of industrial availability and various characteristics in non-aqueous electrolyte secondary batteries.

  Furthermore, it does not specifically limit about cyclic carboxylic acid ester, For example, (gamma) -butyrolactone, (gamma) -valerolactone, (delta) -valerolactone etc. are mentioned.

  Among these, γ-butyrolactone is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

  The type of chain ether is not particularly limited, and examples thereof include dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, and ethoxymethoxyethane.

  Of these, dimethoxyethane and diethoxyethane are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

  The cyclic ether is not particularly limited, and examples thereof include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like.

  Further, the phosphorus-containing organic solvent is not particularly limited, and examples thereof include trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris phosphate (2,2,2-trifluoroethyl), trimethyl phosphite, triethyl phosphite, and triphosphite. Examples include phenyl, trimethylphosphine oxide, triethylphosphine oxide, and triphenylphosphine oxide.

  The type of sulfur-containing organic solvent is not particularly limited, and examples thereof include ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolane, sulfolene, and dimethyl. Examples include sulfone, ethyl methyl sulfone, diphenyl sulfone, methyl phenyl sulfone, dibutyl disulfide, dicyclohexyl disulfide, tetramethyl thiuram monosulfide, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, and the like.

  The boron-containing organic solvent is not particularly limited, and examples thereof include boroxines such as 2,4,6-trimethylboroxine and 2,4,6-triethylboroxine.

  Among these, a chain carbonate and a cyclic carbonate, or a chain carboxylic acid ester and a cyclic carboxylic acid ester are preferable in terms of various characteristics in the non-aqueous electrolyte non-aqueous electrolyte secondary battery, and among them, Ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, methyl acetate, ethyl acetate, propionic acid More preferred are methyl, ethyl propionate, methyl butyrate, ethyl butyrate, and γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 2,2,2-tri Le Oro ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate are more preferred.

These nonaqueous solvents may be used alone or in combination of two or more, but two or more of them are preferably used. For example, it is preferable to use a high dielectric constant solvent of cyclic carbonates in combination with a low viscosity solvent such as chain carbonates or chain esters.
One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the whole non-aqueous solvent is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more. The volume of the cyclic carbonates with respect to the total of the chain and the chain carbonates is preferably 5% by volume or more, more preferably 10% by volume or more, still more preferably 15% by volume or more, particularly preferably 20% by volume or more, It is preferably 70% by volume or less, more preferably 50% by volume or less, still more preferably 40% by volume or less, and particularly preferably 35% by volume or less. A battery produced using a combination of these non-aqueous solvents is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) is improved.

  Examples of preferred combinations of cyclic carbonates and chain carbonates include combinations of ethylene carbonate and chain carbonates, such as ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, Examples include ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

  Of these combinations of cyclic carbonates and chain carbonates, those containing two or more chain carbonates are particularly preferred. This is because the freezing point is lowered and the electrolyte can be used even at an extremely low temperature. Examples include combinations of ethylene carbonate and two or more chain carbonates such as ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl. Examples include carbonate, a combination of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

  A combination in which propylene carbonate is further added to the combination of these ethylene carbonate and chain carbonate is also preferable. When propylene carbonate is contained, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, more preferably 95: 5 to 45:55, and particularly preferably 85:15 to 50:50. It is. Furthermore, when the amount of propylene carbonate in the entire non-aqueous solvent is 0.1% by volume or more and 10% by volume or less, further excellent discharge is maintained while maintaining the characteristics of the combination of ethylene carbonate and chain carbonates. This is preferable because load characteristics can be obtained. The amount of propylene carbonate in the entire non-aqueous solvent is more preferably 1% by volume, particularly preferably 2% by volume or more, more preferably 8% by volume or less, and particularly preferably 5% by volume or less.

  Among these, those containing asymmetrical chain carbonates as chain carbonates are more preferable, and in particular, ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate. Among them, those containing diethyl carbonate and ethyl methyl carbonate, or further containing propylene carbonate are preferable because the balance between cycle characteristics and discharge load characteristics is good. In particular, it is preferable that the asymmetric chain carbonate is ethyl methyl carbonate, and it is preferable that the alkyl group constituting the dialkyl carbonate has 1 to 2 carbon atoms.

  Other examples of preferred non-aqueous solvents are those containing chain carboxylic esters. In particular, those containing a chain carboxylic acid ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving the discharge load characteristics of the battery. In this case, as the chain carboxylic acid esters, Are particularly preferably methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate and ethyl butyrate. The volume of the chain carboxylic acid esters in the non-aqueous solvent is preferably 5% by volume or more, more preferably 8% by volume or more, particularly preferably 10% by volume or more, preferably 50% by volume or less, more preferably It is 35% by volume or less, particularly preferably 30% by volume or less, and particularly preferably 25% by volume or less.

<1-3. Compound having structure represented by general formula (1)>
The present invention is a transition metal oxide capable of occluding and releasing metal ions, containing at least Ni and Co, and containing a transition metal oxide in which 50 mol% or more of the transition metals is Ni and Co A non-aqueous electrolyte containing a specific compound in a non-aqueous electrolyte secondary battery comprising: a negative electrode capable of inserting and extracting metal ions; and a non-aqueous solvent and a non-aqueous electrolyte containing an electrolyte dissolved in the non-aqueous solvent By using the electrolytic solution, it is possible to improve the high-temperature life of the non-aqueous electrolyte secondary battery while maintaining a large current capacity after being left at a high temperature. Although this action and principle are not clear, the present inventors consider as follows. However, the present invention is not limited to the operations and principles described below.

The specific compound is
(A) The positive electrode active material interacts with the transition metal and exhibits the positive electrode protection function. (B) The battery is reduced in two processes, which is reduced on the charged negative electrode and the reduction product grows into a film to protect the negative electrode. It is thought that it contributes to the improvement of characteristics. Details are described below.

(A) The specific compound that interacts with the transition metal in the positive electrode active material and exhibits the positive electrode protective action has a non-shared electron pair in the N atom in the molecule and acts as a Lewis base. Since it interacts with transition metal elements having vacant orbitals, it is thought that it concentrates on the surface of the positive electrode (especially the reactive sites where the transition metal is exposed due to oxygen deficiency or the like). At that time, the specific compound contains an electron-rich and active structure such as a carbon-carbon unsaturated bond or cyano group in the molecular structure. It is thought that it contributes to a positive electrode protection effect by forming a shaped structure.
The energy level of the vacant orbit of the transition metal described above is closely related to the composition of the transition metal oxide, and as defined in the present invention, it contains at least Ni and Co, and 50 mol% or more of the transition metal. Is Ni and Co, it is presumed that the interaction with the unshared electron pair of the N atom in the specific compound is preferable. In addition, since the three N atoms of the isocyanuric skeleton of the specific compound are arranged on an equilateral triangle, three unshared electron pairs can simultaneously interact with one transition metal element and interact with the positive electrode. Is presumed to be suitable.

(Ii) Reduced on the charged negative electrode, the reduction product grows in the form of a film and protects the negative electrode. The specific compound has a carbon-carbon unsaturated bond or a cyano group that is an electrochemically reduced multiple bond in the molecular structure. Therefore, it is thought that it contributes to a negative electrode protection effect by forming a crosslinkable film by reacting on the negative electrode. This coating suppresses the side reaction of decomposition of the electrolyte because it is an insulator, and at the same time does not inhibit the electrode reaction because it is a metal ion conductor such as lithium, so that the characteristics of the non-aqueous electrolyte secondary battery can be reduced. Improve. The specific compound has a large number of polarization structures, and is characterized in that it does not easily become a resistance component by suitably interacting with a metal ion such as lithium.
Moreover, since the radical anion used as a nucleophile generate | occur | produces in the case of the reaction on the said negative electrode, it is estimated that it reacts in concert with the below-mentioned specific additive.

  The non-aqueous electrolyte solution of the present invention contains a specific compound as an essential component, and the specific compound is a compound represented by the general formula (1). In the non-aqueous electrolyte solution of the present invention, one type of the specific compound may be used, or two or more types may be used in combination.

In the general formula (1), R ^{1 to} R ³ may be the same as or different from each other, and may be an organic group having 1 to 20 carbon atoms that may have a substituent. However, at least one of R ^{1 to} R ³ has a carbon-carbon unsaturated bond or a cyano group. Preferably, in the formula (1), R ^{1 to} R ³ may be the same as or different from each other, and may be an organic group having 1 to 10 carbon atoms that may have a substituent. More preferably, in formula (1), at least one of R ^{1 to} R ³ is an organic group having a carbon-carbon unsaturated bond.

  Here, the organic group represents a functional group composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a silicon atom, a sulfur atom and a halogen atom.

Specific examples of the organic group that may have a substituent include an alkyl group having 1 to 20 carbon atoms, an alkenyl group, an alkynyl group, an aryl group, a cyano group, an acrylic group, a methacryl group, a vinylsulfonyl group, a vinylsulfo group, and the like. Is mentioned.
Examples of the substituent herein include a halogen atom and an alkylene group. Moreover, an unsaturated bond etc. may be contained in a part of alkylene group. Of the halogen atoms, a fluorine atom is preferred.

  Specific examples of the alkyl group which may have a substituent include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group and a tert-butyl group. Examples thereof include a linear or branched alkyl group or a cyclic alkyl group such as a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group.

  Specific examples of the alkenyl group that may have a substituent include a vinyl group, an allyl group, a methallyl group, and a 1-propenyl group. Specific examples of the alkynyl group which may have a substituent include ethynyl group, propargyl group, 1-propynyl group and the like. Specific examples of the aryl group which may have a substituent include a phenyl group, a tolyl group, a benzyl group, and a phenethyl group.

  Among these, an alkyl group, an alkenyl group, an alkynyl group, an acrylic group, a methacryl group, an aryl group, a cyano group, a vinylsulfonyl group, and a vinylsulfo group that may have a substituent are preferable.

  More preferably, an alkyl group, an alkenyl group, an alkynyl group, an acrylic group, a methacryl group, or a cyano group, which may have a substituent, may be mentioned.

  Particularly preferably, an alkyl group, an alkenyl group, an acrylic group, a methacryl group, or a cyano group, which may have a substituent, may be mentioned.

  Most preferably, the alkyl group, allyl group, and methallyl group which may have a substituent are mentioned. In particular, an allyl group or a methallyl group which is an organic group having an unsubstituted carbon-carbon unsaturated bond is preferable. An allyl group is preferable from the viewpoint of film forming ability.

  Although the compound used for this invention is a compound which has a structure shown by General formula (1), the compound of the following structures is mentioned as the specific example.

  Preferably, the compound of the following structures is mentioned.

  More preferably, the compound of the following structures is mentioned.

  Particularly preferred are compounds having the following structures.

  Most preferably, the compound of the following structure is mentioned.

また、これら最も好ましい化合物の中でも、被膜形成能の観点から以下の構造の化合物が好ましい。

Of these most preferred compounds, compounds having the following structure are preferred from the viewpoint of film-forming ability.

  With respect to the specific compound, there is no particular limitation on the production method, and any known method can be selected and produced.

  The ratio of the specific compounds in the non-aqueous electrolyte is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 10% by mass or less, more preferably 4.5% by mass in total. Hereinafter, it is more preferably 3% by mass or less, still more preferably 2% by mass or less, particularly preferably 1.8% by mass or less, and most preferably 1.6% by mass or less. If the concentration of the specific compound is excessive, there are too many reduction products, so that the surface of the negative electrode is excessively covered and the electrode reaction is inhibited. Moreover, the cost of a non-aqueous electrolyte solution will also increase. If it is said density | concentration, since the effect | action in an electrode interface will advance more suitably, it will become possible to optimize a battery characteristic.

  When a specific compound is contained in a non-aqueous electrolyte solution and actually used for the production of a non-aqueous electrolyte secondary battery, even if the battery is disassembled and the non-aqueous electrolyte solution is extracted again, the content in the non-aqueous electrolyte solution is significantly reduced. There are many cases. Therefore, what can be detected from a non-aqueous electrolyte extracted from a battery even with a very small amount of a specific compound is considered to be included in the present invention. In addition, when the specific compound is actually used as a non-aqueous electrolyte for the production of a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte obtained by disassembling and re-extracting the battery contains a very small amount of the specific compound. Even if it is not, it is often detected on the positive electrode, the negative electrode, or the separator, which is another component of the non-aqueous electrolyte secondary battery. Therefore, when a specific compound is detected from the positive electrode, the negative electrode, and the separator, it can be assumed that the total amount is contained in the nonaqueous electrolytic solution. Under this assumption, it is preferable that the specific compound is included in the above range.

<1-4. Additives>
The nonaqueous electrolytic 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 for an additive. 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. Among these, as an auxiliary agent for suppressing capacity retention characteristics and resistance increase after high-temperature storage, cyclic carbonate having a fluorine atom, cyclic carbonate having a carbon-carbon unsaturated bond, difluorophosphate, fluorosulfate, Contains at least one compound selected from the group consisting of a compound having an isocyanato group, a compound having a cyano group, a cyclic sulfonic acid ester, and a dicarboxylic acid complex salt (hereinafter sometimes abbreviated as “specific additive”). It is preferable. Hereinafter, the specific additive and other additives will be described separately.

<1-4-1. Specific additive>
All of the specific additives are considered to react with the specific compound reduced on the negative electrode to form a film-like structure suitable for the electrode reaction in concert. Although this action / principle is not limited to the action / principle described below, the present inventors presume as follows. (I) dicarboxylic acid complex salt, (ii) cyclic carbonate having a fluorine atom, (iii) cyclic carbonate having a carbon-carbon unsaturated bond, (iv) difluorophosphate, (v) fluorosulfate, (vi) The presumed reaction mechanism of the compound having an isocyanato group, (vii) the compound having a cyano group, and (viii) the cyclic sulfonate with the nucleophilic species Nu ⁻ formed on the negative electrode surface by reduction of the specific compound is shown below. .

(In the reaction formula, Cat is a cation constituting a salt. Q ¹ is a single bond or a divalent organic group, X is a divalent organic group containing a complex central element, and Q ² is a divalent organic containing fluorine. Group, Q ³ represents a divalent organic group containing a carbon-carbon unsaturated bond, Q ⁶ and Q ⁷ represent a monovalent organic group, and Q ⁸ represents a divalent organic group.)
As shown in the reaction formula, each of the specific additives contains a nucleophilic attack accepting site, and each electrode reaction is the starting reaction, and the electrode reaction using the specific compound and the specific additive as raw materials is well supported. It is presumed that the film-like structure to be formed is formed in concert.

The molecular weight of the specific additive is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but those having a molecular weight of 50 or more and 250 or less are preferable. Within this range, the solubility of the specific additive in the non-aqueous electrolyte is good, and the effect of addition can be sufficiently exhibited.
Moreover, there is no restriction | limiting in particular also in the manufacturing method of a specific additive, It is possible to select and manufacture a well-known method arbitrarily. A commercially available product may also be used.

  In addition, the specific additive may be included alone in the nonaqueous electrolytic solution of the present invention, or two or more specific additives may be combined in any combination and ratio.

<1-4-1-1. Dicarboxylic acid complex salt>
Among the specific additives, the dicarboxylic acid complex salt is not particularly limited, and any dicarboxylic acid complex salt can be used.
Examples of the dicarboxylic acid complex salt include a dicarboxylic acid complex salt whose complex central element is boron, and a dicarboxylic acid complex salt whose complex central element is phosphorus.

  Specific examples of the dicarboxylic acid complex salt whose complex central element is boron include lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium bis (malonate) borate, lithium difluoro (malonato) borate, lithium bis (methylmalonate) Examples thereof include borate, lithium difluoro (methylmalonate) borate, lithium bis (dimethylmalonate) borate, and lithium difluoro (dimethylmalonate) borate.

  Specific examples of the dicarboxylic acid complex salt in which the complex element is phosphorus include lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, lithium tris (malonato) phosphate, lithium difluorobis (Malonate) phosphate, lithium tetrafluoro (malonate) phosphate, lithium tris (methylmalonate) phosphate, lithium difluorobis (methylmalonate) phosphate, lithium tetrafluoro (methylmalonate) phosphate, lithium tris (dimethylmalonate) phosphate, lithium difluorobis (dimethyl) Malonato) phosphate, lithium tetrafluoro (dimethylmalonate) phosphate and the like.

  Among them, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate are easily available and have a stable film structure It is more preferably used because it can contribute to the formation of an object.

The content of the dicarboxylic acid complex salt is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired, but are preferably 0.001% by mass or more with respect to the nonaqueous electrolytic solution of the present invention. 5% by mass or less.
When the content of the dicarboxylic acid complex salt is equal to or higher than this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, when it is below this upper limit, the increase in the manufacturing cost of a non-aqueous electrolyte secondary battery can be avoided, and the volume expansion of the non-aqueous electrolyte secondary battery due to gas generation can be avoided. The content of the dicarboxylic acid complex salt is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 2.0% by mass or less. More preferably, it is 1.5% by mass or less, particularly preferably 1.2% by mass or less.

<1-4-1-2. Cyclic carbonate having a fluorine atom>
Among the specific additives, the cyclic carbonate having a fluorine atom (hereinafter sometimes abbreviated as “F-carbonate”) is not particularly limited as long as it has a fluorine atom. Can be used.

The number of fluorine atoms in the fluorinated carbonate is not particularly limited as long as it is 1 or more, and 2 or less is particularly preferable.
Examples of the fluorinated carbonate include fluoroethylene carbonate and derivatives thereof.
Specific examples of fluoroethylene carbonate and derivatives thereof include fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4- Methyl ethylene carbonate, 4-fluoro-5-methyl ethylene carbonate, 4,4-difluoro-5-methyl ethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (tri Fluoromethyl) -ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate Boneto, 4,5-difluoro-4,5-dimethylethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate.

Among these fluorinated carbonates, fluoroethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate are preferable, and in particular, fluoroethylene carbonate is a stable film. It is possible to contribute to the formation of the structure, and is most preferably used.
The content of the fluorinated carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. However, the content of the fluorinated carbonate is preferably 0.001% by mass or more and 10.0% with respect to the nonaqueous electrolytic solution of the present invention. It is below mass%.

  When the content of the fluorinated carbonate is not less than this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, the increase in the manufacturing cost of a non-aqueous electrolyte secondary battery can be avoided as it is below this upper limit. The content of fluorinated carbonate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 8.0% by mass or less. Especially preferably, it is 6.0 mass% or less.

  In addition, fluorinated carbonate expresses an effective function not only as an additive but also as the non-aqueous solvent described in 1-2 above. There is no clear boundary in the blending amount when using fluorinated carbonate as a solvent and additive, and the described blending amount can be followed as it is.

<1-4-1-3. Cyclic carbonate having a carbon-carbon unsaturated bond>
Among specific additives, as cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes abbreviated as “unsaturated carbonate”), carbon-carbon double bonds, carbon-carbon triple bonds, etc. If it is a carbonate which has a carbon unsaturated bond, it will not specifically limit, Arbitrary unsaturated carbonates can be used.

Examples of the unsaturated carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having a carbon-carbon unsaturated bond, and the like.
Specific examples of vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate and the like.
Specific examples of ethylene carbonates substituted with a substituent having a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, and the like.

Among these, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are preferable. In particular, vinylene carbonate can contribute to the formation of a stable film-like structure and is more preferably used.
The content of the unsaturated carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. However, the content of the unsaturated carbonate is preferably 0.001% by mass or more and 5.0% with respect to the nonaqueous electrolytic solution of the present invention. It is below mass%.

  When the content of the unsaturated carbonate is not less than this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, the initial resistance increase of a non-aqueous electrolyte secondary battery can be avoided as it is below this upper limit. The content of the unsaturated carbonate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 4.0% by mass or less. More preferably, it is 3.0 mass% or less, Most preferably, it is 2.0 mass% or less.

<1-4-1-4. Difluorophosphate>
Among the specific additives, the difluorophosphate is not particularly limited as long as it is a salt having a difluorophosphate anion as a constituent element, and any difluorophosphate can be used.
Examples of the difluorophosphate include lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, ammonium difluorophosphate, and the like.

Among these, lithium difluorophosphate is preferable, can contribute to the formation of a stable film-like structure, and is more preferably used.
The content of the difluorophosphate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired, but are preferably 0.001% by mass or more with respect to the nonaqueous electrolytic solution of the present invention. 0% by mass or less.

  When the content of difluorophosphate is at least the lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, the increase in the manufacturing cost of a non-aqueous electrolyte secondary battery can be avoided as it is below this upper limit. The content of difluorophosphate is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 1.5% by mass or less. More preferably, it is 1.2 mass% or less, Most preferably, it is 1.1 mass% or less.

<1-4-1-5. Fluorosulfate>
Among the specific additives, the fluorosulfate is not particularly limited as long as it is a salt having a fluorosulfuric acid anion as a constituent element, and any fluorosulfate can be used.
Examples of the fluorosulfate include lithium fluorosulfate, sodium fluorosulfate, potassium fluorosulfate, ammonium fluorosulfate, and the like.

Among these, lithium fluorosulfate is preferable, can contribute to the formation of a stable film-like structure, and is more preferably used.
The content of the fluorosulfate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired. However, the content of the fluorosulfate is preferably 0.001% by mass or more and 4.0% with respect to the nonaqueous electrolytic solution of the present invention. It is below mass%.

  When the content of the fluorosulfate is equal to or higher than this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Further, if it is below this upper limit, it is possible to avoid an increase in the manufacturing cost of the non-aqueous electrolyte secondary battery, and corrosion of aluminum frequently used for the positive electrode current collector and metal can often used for the exterior body. Performance degradation due to can be avoided. The content of fluorosulfate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 3.0% by mass or less. More preferably, it is 2.5 mass% or less, Most preferably, it is 2.0 mass% or less.

<1-4-1-6. Compound having isocyanato group>
Among the specific additives, the compound having an isocyanato group (hereinafter sometimes abbreviated as “isocyanate”) is not particularly limited, and any isocyanate can be used.
Examples of the isocyanate include monoisocyanates, diisocyanates, and triisocyanates.

  Specific examples of monoisocyanates include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1-isocyanate. Natooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl isocyanate And fluorosulfonyl isocyanate.

  Specific examples of diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanate. Natooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,3-diisocyanatopropene, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato -3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohe Sun, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1, 2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1′-diisocyanate, dicyclohexylmethane-2,2′-diisocyanate, dicyclohexylmethane-3, 3′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, isophorone diisocyanate, bicyclo [2.2.1] heptane-2,5-diylbis (methyl = isocyanate), bi And black [2.2.1] heptane-2,6-diylbis (methyl = isocyanate), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and the like. .

  Specific examples of triisocyanates include 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, 1,3,5-triisocyanate methylbenzene, 1,3,5 -Tris (6-isocyanatohex-1-yl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 4- (isocyanatomethyl) octamethylene = diisocyanate Can be mentioned.

  Among them, 1,6-diisocyanatohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,3,5-tris (6-isocyanatohex-1-yl) -1,3,5-triazine- 2,4,6 (1H, 3H, 5H) -trione, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate are industrially easily available It is preferable in that the production cost of the electrolytic solution can be kept low, and it can contribute to the formation of a stable film-like structure from the technical point of view, and is more preferably used.

The content of the isocyanate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. However, the content of the isocyanate is preferably 0.001% by mass or more and 1.0% by mass with respect to the nonaqueous electrolytic solution of the present invention. It is as follows.
When the isocyanate content is not less than this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, the initial resistance increase of a non-aqueous electrolyte secondary battery can be avoided as it is below this upper limit. The content of isocyanate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 0.8% by mass or less, still more preferably. Is 0.7% by mass or less, particularly preferably 0.6% by mass or less.

<1-4-1-7. Compound having cyano group>
Among the specific additives, the compound having a cyano group (hereinafter sometimes abbreviated as “nitrile”) is not particularly limited, and any nitrile can be used.
Examples of nitriles include mononitriles and dinitriles.
Specific examples of mononitriles include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, Cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitryl, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2 -Pentenenitrile, 2-hexenenitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluor Propionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3′-oxy Examples thereof include dipropionitrile, 3,3′-thiodipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, pentafluoropropionitrile and the like.

  Specific examples of dinitriles include malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecandinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert- Butylmalononitrile, methylsuccinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, 2,3,3-trimethylsuccinonitrile, 2,2,3,3-tetramethylsuccino Nitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2- Zikal Nitrile, bicyclohexyl-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2,3-diisobutyl-2,3-dimethylsuccinonitrile, 2,2-diisobutyl-3 , 3-Dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2 , 4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, maleonitrile, fumaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2- Jianobenzen, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3 '- (ethylenedioxy) dipropionate nitrile, 3,3' - (ethylene dithio) dipropionate nitrile, and the like.

Among them, dinitriles such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecanedinitrile, etc. can contribute to the formation of a stable film-like structure, More preferably used.
The content of nitrile is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired, but preferably 0.001% by mass or more and 5.0% by mass with respect to the nonaqueous electrolytic solution of the present invention. It is as follows.

  When the nitrile content is at least this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, when it is below this upper limit, the initial resistance increase of a non-aqueous electrolyte secondary battery can be avoided, and deterioration of rate characteristics can be suppressed. The nitrile content is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 4.0% by mass or less, still more preferably. Is 3.0% by mass or less, particularly preferably 2.5% by mass or less.

<1-4-1-8. Cyclic sulfonate ester>
Among the specific additives, the cyclic sulfonate ester is not particularly limited, and any cyclic sulfonate ester can be used.
Examples of cyclic sulfonic acid esters include saturated cyclic sulfonic acid esters, unsaturated cyclic sulfonic acid esters, saturated cyclic disulfonic acid esters, unsaturated cyclic disulfonic acid esters, and the like.

  Specific examples of the saturated cyclic sulfonate ester include 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, and 3-fluoro-1,3-propane sultone. 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1,4-butane sultone, 1-fluoro-1,4-butane sultone, 2-fluoro-1,4-butane sultone, 3-fluoro-1,4-butane sultone, 4-fluoro-1,4-butane sultone, 1-methyl-1,4-butane sultone, 2-methyl-1,4-butane sultone, Examples include 3-methyl-1,4-butane sultone and 4-methyl-1,4-butane sultone.

  Specific examples of the unsaturated cyclic sulfonate ester include 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro- 1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3-sultone, 2-fluoro-2-propene-1,3- Sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2-methyl-1-propene-1,3-sultone, 3-methyl-1- Propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl-2-propene-1,3-sultone, 1-butene-1, -Sultone, 2-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro-1-butene-1,4-sultone 3-fluoro-1-butene-1,4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-fluoro-2-butene-1,4-sultone, 2-fluoro-2-butene -1,4-sultone, 3-fluoro-2-butene-1,4-sultone, 4-fluoro-2-butene-1,4-sultone, 1-fluoro-3-butene-1,4-sultone, 2 -Fluoro-3-butene-1,4-sultone, 3-fluoro-3-butene-1,4-sultone, 4-fluoro-3-butene-1,4-sultone, 1-methyl-1-butene-1 , 4-sultone, 2-methyl-1-butene 1,4-sultone, 3-methyl-1-butene-1,4-sultone, 4-methyl-1-butene-1,4-sultone, 1-methyl-2-butene-1,4-sultone, 2- Methyl-2-butene-1,4-sultone, 3-methyl-2-butene-1,4-sultone, 4-methyl-2-butene-1,4-sultone, 1-methyl-3-butene-1, Examples include 4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1,4-sultone, 4-methyl-3-butene-1,4-sultone, and the like.

Among them, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3- Sultone is more preferably used because it can be easily obtained and can contribute to the formation of a stable film-like structure.
The content of the cyclic sulfonic acid ester is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired, but is preferably 0.001% by mass or more with respect to the nonaqueous electrolytic solution of the present invention. 0% by mass or less.

  When the content of the cyclic sulfonic acid ester is not less than this lower limit, a sufficient effect of improving cycle characteristics can be provided to the non-aqueous electrolyte secondary battery. Moreover, the increase in the manufacturing cost of a non-aqueous electrolyte secondary battery can be avoided as it is below this upper limit. The content of the cyclic sulfonic acid ester is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 2.5% by mass or less. More preferably, it is 2.0 mass% or less, Most preferably, it is 1.8 mass% or less.

<1-4-2. Other additives>
Examples of additives other than the specific additive include an overcharge inhibitor, an auxiliary agent for improving capacity retention characteristics and cycle characteristics after high-temperature storage, and the like.

<1-4-2-1. Overcharge prevention agent>
Specific examples of the overcharge inhibitor include toluene derivatives such as toluene and xylene; biphenyl derivatives substituted with an unsubstituted or alkyl group such as biphenyl, 2-methylbiphenyl, 3-methylbiphenyl, and 4-methylbiphenyl; o- Terphenyl derivatives that are unsubstituted or substituted with alkyl groups such as terphenyl, m-terphenyl, p-terphenyl; partial hydrides of terphenyl derivatives that are unsubstituted or substituted with alkyl groups; cyclopentylbenzene, cyclohexylbenzene, etc. Cycloalkylbenzene derivatives of the following: alkylbenzene derivatives having a tertiary carbon directly bonded to a benzene ring such as cumene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene; t-butylbenzene, t-amylbenzene, t-hexyl Benzene rings such as benzene Alkylbenzene derivative having a quaternary carbon direct bond; diphenyl ether, aromatic compounds having an oxygen atom of dibenzofuran and the like; aromatic compounds, and the like.

  Furthermore, specific examples of other overcharge preventing agents include partially fluorinated products of the aromatic compounds such as fluorobenzene, fluorotoluene, benzotrifluoride, 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene and the like. And fluorinated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole and 1,6-difluoroanisole;

In addition, these overcharge inhibitors may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations. Moreover, when using together by arbitrary combinations, it may use together by the compound of the same classification illustrated above and may be used together by a compound of a different classification | category.
When blending the overcharge inhibitor, the blending amount of the overcharge inhibitor is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 0.001% by mass or more based on the whole non-aqueous electrolyte. It is the range of 10 mass% or less.

  If the non-aqueous electrolyte of the present invention contains an overcharge inhibitor within a range that does not significantly impair the effects of the present invention, the overcharge protection circuit such as an incorrect usage or an abnormality of the charging device should operate normally. Even if the battery is overcharged due to the situation, it is preferable because the safety of the non-aqueous electrolyte secondary battery is improved.

<1-4-2-2. Auxiliary>
On the other hand, specific examples of the auxiliary for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage include the following.
Dicarboxylic acid anhydrides such as succinic acid, maleic acid and phthalic acid; carbonate compounds other than those corresponding to carbonates having an unsaturated bond such as erythritan carbonate and spiro-bis-dimethylene carbonate; cyclic compounds such as ethylene sulfite Sulfite; Chain sulfonate such as methyl methanesulfonate and busulfan; Cyclic sulfone such as sulfolane and sulfolen; Chain sulfone such as dimethylsulfone, diphenylsulfone and methylphenylsulfone; Dibutyldisulfide, dicyclohexyldisulfide, tetramethylthiurammono Sulfides such as sulfides; sulfur-containing compounds such as sulfonamides such as N, N-dimethylmethanesulfonamide and N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1- Nitrogen-containing compounds such as til-2-piperidone, 3-methyl-2-oxazolidinone and 1,3-dimethyl-2-imidazolidinone; hydrocarbon compounds such as heptane, octane and cycloheptane; fluorobenzene, difluorobenzene and benzo And fluorine-containing aromatic compounds such as trifluoride.

In addition, these adjuvants may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
Further, when the non-aqueous electrolyte solution of the present invention contains these auxiliaries, it is optional as long as the effects of the present invention are not significantly impaired, but preferably 0.001% by mass or more based on the whole non-aqueous electrolyte solution. It is the range of 10 mass% or less.

<1-5. Method for producing non-aqueous electrolyte>
The non-aqueous electrolyte solution of the present invention can be prepared by dissolving the electrolyte, the specific compound, and, if necessary, the above-mentioned “additive” and “auxiliary” in the above-described non-aqueous solvent.
In preparing the non-aqueous electrolyte solution, it is preferable that each raw material of the non-aqueous electrolyte solution, that is, an electrolyte such as a lithium salt, a specific compound, a non-aqueous solvent, an additive, an auxiliary agent, and the like be dehydrated in advance. The degree of dehydration is usually 50 ppm or less, preferably 30 ppm or less.

  By removing moisture in the non-aqueous electrolyte, water electrolysis, water-lithium metal reaction, lithium salt hydrolysis, and the like are less likely to occur. The dehydration means is not particularly limited. For example, when the object to be dehydrated is a liquid such as a non-aqueous solvent, a desiccant such as molecular sieve may be used. In addition, when the object to be dehydrated is a solid such as an electrolyte, it may be dried by heating at a temperature lower than the temperature at which decomposition occurs.

[2. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode and a positive electrode that can occlude and release metal ions, and the non-aqueous electrolyte of the present invention.

<2-1. Battery configuration>
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 positive electrode described later and the non-aqueous electrolyte described above. A positive electrode and a negative electrode are laminated via a porous film (separator) impregnated with an aqueous electrolyte solution, and these are housed in a case (exterior body). Therefore, the shape of the nonaqueous 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.

<2-2. 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.

<2-3. Negative electrode>
The negative electrode active material used for the negative electrode is not particularly limited as long as it can electrochemically occlude and release metal ions. Specific examples thereof include carbonaceous materials, metal compound materials, lithium-containing metal composite oxide materials, and the like. One of these may be used alone, or two or more may be used in any combination.

<2-3-1. Carbonaceous material>
The carbonaceous material used as the negative electrode active material is not particularly limited, but a material selected from the following (A) to (D) is preferable because it has a good balance between initial irreversible capacity and high current density charge / discharge characteristics.
(A) Natural graphite (I) Artificial carbonaceous material and carbonaceous material obtained by heat treating artificial graphite material at least once in the range of 400 to 3200 ° C. (C) The negative electrode active material layer has at least two different crystallinities. (D) a negative electrode active material layer comprising carbonaceous materials having at least two different orientations, and / or a carbonaceous material having an interface with which the different crystalline carbonaceous materials are in contact. And / or the carbonaceous materials (a) to (d) having an interface with which the carbonaceous materials having different orientations are in contact may be used alone or in any combination of two or more. And may be used in combination in a ratio.

Specific examples of the artificial carbonaceous material or artificial graphite material of (i) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch and those pitch-oxidized, needle coke, Pitch coke and carbon materials partially graphitized thereof, furnace black, acetylene black, pyrolysis products of organic substances such as pitch-based carbon fibers, carbonizable organic substances and their carbides, and carbonizable organic substances as benzene, toluene, Examples include solution-like carbides dissolved in low-molecular organic solvents such as xylene, quinoline, and n-hexane.
As for the properties of the carbonaceous material, it is desirable that any one or a plurality of items (1) to (8) below be satisfied at the same time.

(1) 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 preferably 0.335 nm or more, and is usually 0.8. It is 360 nm or less, preferably 0.350 nm or less, and more preferably 0.345 nm or less. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, more preferably 1.5 nm or more, and still more preferably 2 nm or more.

(2) Volume-based average particle diameter The volume-based average particle diameter of the carbonaceous material is usually 1 μm or more, and more preferably 3 μm or more, based on the volume-based average particle diameter (median diameter) determined by the laser diffraction / scattering method. It is more preferably 5 μm or more, particularly preferably 7 μm or more, preferably 100 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, particularly preferably 30 μm or less, and particularly preferably 25 μm or less. When the volume reference average particle diameter is within the above range, the irreversible capacity does not increase excessively, and it is easy to avoid incurring loss of the initial battery capacity. In addition, when an electrode is produced by coating, it is easy to uniformly coat the surface, which is desirable in the battery manufacturing process. In order to measure the volume-based average particle size, a carbonaceous material powder is dispersed in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and laser diffraction / A scattering type particle size distribution meter (LA-700 manufactured by Horiba, Ltd.) is used. The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.

(3) Raman R value, Raman half value width The Raman R value of the carbonaceous material is preferably 0.01 or more, more preferably 0.03 or more, as measured using an argon ion laser Raman spectrum method. It is more preferably 0.1 or more, preferably 1.5 or less, more preferably 1.2 or less, still more preferably 1 or less, and particularly preferably 0.5 or less.

When the Raman R value is in the above range, the crystallinity of the particle surface is in an appropriate range, and it is possible to suppress a decrease in sites where Li enters between layers with charge / discharge, and charge acceptability is hardly lowered. Further, even when the negative electrode is densified by applying it to the current collector and then pressing it, it is difficult to cause a decrease in load characteristics. Furthermore, it is difficult to cause a decrease in efficiency and an increase in gas generation.
Moreover, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material is not particularly limited, but is 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and is usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.

When the Raman half width is in the above range, the crystallinity of the particle surface is in an appropriate range, and the decrease in the sites where Li enters between the layers can be suppressed with charge / discharge, and the charge acceptability is hardly lowered. Further, even when the negative electrode is densified by applying it to the current collector and then pressing it, it is difficult to cause a decrease in load characteristics. Furthermore, it is difficult to cause a decrease in efficiency and an increase in gas generation.
The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity IA of a peak PA around 1580 cm ^-1, and measuring the intensity IB of the peak PB around 1360 cm ^-1, and calculates the intensity ratio R (R = IB / IA) . The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material. Moreover, the half width of the peak PA near 1580 cm ⁻¹ of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material.

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

(4) BET specific surface area As for the BET specific surface area of the carbonaceous material, the value of the specific surface area measured using the BET method is preferably 0.1 m ² · g ⁻¹ or more, and 0.7 m ² · g ^−1. The above is more preferable, 1.0 m ² · g ⁻¹ or more is further preferable, 1.5 m ² · g ⁻¹ or more is particularly preferable, and preferably 100 m ² · g ⁻¹ or less, and 25 m ² · g ^{−. 1} or less is more preferable, 15 m ² · g ⁻¹ or less is more preferable, and 10 m ² · g ⁻¹ or less is particularly preferable.

When the value of the BET specific surface area is within the above range, the acceptability of cations such as lithium is good at the time of charging when used as a negative electrode material, lithium and the like are difficult to precipitate on the electrode surface, and a decrease in stability is avoided. Cheap. further. The reactivity with the non-aqueous electrolyte can be suppressed, gas generation is small, and a preferable battery is easily obtained.
The specific surface area was measured by the BET method using a surface area meter (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 accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material.

(5) Circularity When the circularity is measured as a spherical degree 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. It is desirable that the circularity of particles having a carbonaceous material particle size in the range of 3 to 40 μm is closer to 1. Preferably it is 0.1 or more, 0.5 or more is more preferable, 0.8 or more is further more preferable, 0.85 or more is especially preferable, and 0.9 or more is especially preferable.

High current density charge / discharge characteristics generally improve as the 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 of the carbonaceous material is measured using a flow particle image analyzer (FPIA manufactured by Sysmex Corporation). Specifically, about 0.2 g of a sample is dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and an ultrasonic wave of 28 kHz is output at 60 W for 1 After irradiating for minutes, the detection range is specified as 0.6 to 400 μm, and the particle size is measured for particles in the range of 3 to 40 μm. The circularity determined by the measurement is defined as the circularity of the carbonaceous material.

  The method for improving the degree of circularity is not particularly limited, but a spheroidized 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 approximating a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by an adhesive force possessed by a binder or particles, etc. Is mentioned.

(6) The tap density of the tap density carbonaceous material, preferably at 0.1 g · ^{cm -3} or more, 0.5 g · ^{cm -3} or more, and more preferably 0.7 g · ^{cm -3} or more, 1 g · cm ⁻³ or more is particularly preferable. Moreover, 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 especially preferable.

When the tap density is within the above range, a sufficient packing density can be secured when used as a negative electrode, and a high-capacity battery can be obtained. Furthermore, voids between the particles in the electrode are not reduced too much, conductivity between the particles is ensured, and preferable battery characteristics are easily obtained.
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. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material.

(7) Orientation ratio The orientation ratio of the carbonaceous material is preferably 0.005 or more, more preferably 0.01 or more, still more preferably 0.015 or more, and preferably 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 of the carbonaceous material is obtained by measuring by X-ray diffraction after pressure-molding the sample. Specifically, a molded body obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing with a 58.8 MN · m ⁻² is flush with the surface of the measurement sample holder using clay. Then, the X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbonaceous material, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material.

The X-ray diffraction measurement conditions at this time 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 degrees 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

(8) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, more preferably 5 or less. If the aspect ratio is out of the above range, streaking may occur when forming an electrode plate, a uniform coated surface may not be obtained, and high current density charge / discharge characteristics may be deteriorated. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

  The aspect ratio of the carbonaceous material is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Specifically, arbitrary 50 carbonaceous material particles fixed to the end face of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted, and observed three-dimensionally. Then, the longest diameter A of the carbonaceous material particles and the shortest diameter B orthogonal thereto are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material.

<2-3-2. Metal compound materials>
The metal compound-based material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, and is a single metal or alloy that forms a lithium alloy, or oxides, carbides, nitrides, silicides thereof. Compounds such as oxides, sulfides and phosphides. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Among them, a single metal or an alloy that forms a lithium alloy is preferable, and a material containing a metal / metalloid element (that is, excluding carbon) of Group 13 or Group 14 of the periodic table is more preferable. A single metal of silicon (Si), tin (Sn), or lead (Pb) (hereinafter, these three elements may be referred to as “SSP metal elements”), an alloy containing these atoms, or a metal thereof (SSP) A compound of (metal element) is preferable. Most preferred is silicon. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the negative electrode active material having at least one atom selected from SSP metal elements include a single metal of any one SSP metal element, an alloy composed of two or more SSP metal elements, one or more kinds Alloys composed of SSP metal elements and other one or more metal elements, and compounds containing one or more SSP metal elements, or oxides, carbides, and nitrides of the compounds And composite compounds such as silicides, sulfides and phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

  Moreover, the compound which these complex compounds combined with several elements, such as a metal simple substance, an alloy, or a nonmetallic element, can also be mentioned as an example. More specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. In addition, for example, in the case of tin, a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element can also be used. .

  Among these negative electrode active materials, since the capacity per unit mass is large when a battery is formed, any one element of an SSP metal element, an alloy of two or more SSP metal elements, oxidation of an SSP metal element In particular, silicon and / or tin metal simple substance, alloy, oxide, carbide, nitride, etc. are preferable, and silicon metal simple substance, alloy, oxide, carbide, etc. per unit mass. The most preferable from the viewpoint of the capacity and environmental load.

In addition, although the capacity per unit mass is inferior to that of using a single metal or an alloy, the following compounds containing silicon and / or tin are also preferred because of excellent cycle characteristics.
The element ratio of silicon and / or tin to oxygen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin oxide” of 3 or less, more preferably 1.1 or less.

-Element ratio of silicon and / or tin and nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin nitride” of 3 or less, more preferably 1.1 or less.
The elemental ratio of silicon and / or tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Carbide of silicon and / or tin” of 3 or less, more preferably 1.1 or less.
In addition, any one of the above-described negative electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

<2-3-3. Lithium-containing metal composite oxide material>
The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but lithium-containing composite metal oxide materials containing titanium are preferable, and lithium and titanium composite oxidation (Hereinafter sometimes abbreviated as “lithium titanium composite oxide”) is particularly preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in a negative electrode active material for a lithium ion non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred.
The metal oxide as the negative electrode active material is a lithium-titanium composite oxide represented by the following general formula (5). In the general formula (5), 0.7 ≦ x ≦ 1.5, 1.5 It is preferable that ≦ y ≦ 2.3 and 0 ≦ z ≦ 1.6 because the structure upon doping and dedoping of lithium ions is stable.

_{Li x Ti y M z O 4} (5)
(In General Formula (5), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb.)
Among the compositions represented by the general formula (5),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.

Particularly preferred representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.
In addition to the above requirements, the lithium titanium composite oxide as the negative electrode active material in the present invention further satisfies at least one of the characteristics such as physical properties and shapes shown in the following [1] to [8]. It is preferable to satisfy a plurality of items at the same time.

[1] BET specific surface area The BET specific surface area of the lithium-titanium composite oxide used as the negative electrode active material is preferably 0.5 m ² · g ⁻¹ or more as measured by the BET method. 7 m ² · g ⁻¹ or more is more preferred, 1.0 m ² · g ⁻¹ or more is more preferred, 1.5 m ² · g ⁻¹ or more is particularly preferred, and 200 m ² · g ⁻¹ or less is preferred, 100 m ² · g ⁻¹ or less is more preferred, 50 m ² · g ⁻¹ or less is more preferred, and 25 m ² · g ⁻¹ or less is particularly preferred.

When the BET specific surface area is within the above range, the reaction area in contact with the non-aqueous electrolyte when used as the negative electrode material is unlikely to decrease, and the output resistance can be prevented from increasing. Furthermore, since the increase in the surface and end face portions of the metal oxide crystal containing titanium is suppressed and the resulting crystal distortion is less likely to occur, a preferable battery is easily obtained.
The specific surface area of the lithium-titanium composite oxide was preliminarily dried at 350 ° C. for 15 minutes under a nitrogen flow using a surface area meter (a fully automatic surface area measuring device manufactured by Rikura Okura) using a surface area meter. Thereafter, a nitrogen adsorption BET one-point method using a gas flow method is performed using a nitrogen helium mixed gas that is accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3. The specific surface area determined by the measurement is defined as the BET specific surface area of the lithium titanium composite oxide.

[2] Volume-based average particle size The volume-based average particle size of the lithium-titanium composite oxide (secondary particle size when primary particles are aggregated to form secondary particles) is determined by the laser diffraction / scattering method. It is defined by the obtained volume-based average particle diameter (median diameter).
The volume-based average particle diameter of the lithium titanium composite oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, further preferably 0.7 μm or more, more preferably 50 μm or less, more preferably 40 μm or less, and 30 μm. The following is more preferable, and 25 μm or less is particularly preferable.

Specifically, the volume-based average particle diameter of the lithium-titanium composite oxide was measured by adding a lithium-titanium composite oxide to a 0.2% by mass aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant. The powder is dispersed and the measurement is performed using a laser diffraction / scattering particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the lithium titanium composite oxide.
When the volume average particle size of the lithium-titanium composite oxide is within the above range, the amount of the binder can be suppressed during the production of the negative electrode, and as a result, it becomes easy to prevent the battery capacity from being lowered. Furthermore, when forming a negative electrode plate, a uniform coating surface is likely to be obtained, which is desirable in the battery manufacturing process.

[3] Average primary particle diameter When primary particles are aggregated to form secondary particles, the average primary particle diameter of the lithium titanium composite oxide is preferably 0.01 μm or more, more preferably 0.05 μm or more. Preferably, 0.1 μm or more is more preferable, 0.2 μm or more is particularly preferable, 2 μm or less is preferable, 1.6 μm or less is more preferable, 1.3 μm or less is further preferable, and 1 μm or less is particularly preferable. When the volume-based average primary particle diameter is within the above range, spherical secondary particles are easily formed and the specific surface area is easily secured, so that it is easy to prevent a decrease in battery performance such as output characteristics.

  In addition, the primary particle diameter of lithium titanium complex oxide is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification at which particles can be confirmed, for example, a magnification of 10,000 to 100,000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is determined for any 50 primary particles. Obtained and obtained by taking an average value.

[4] Shape The shape of the lithium-titanium composite oxide particles may be any of lump shape, polyhedron shape, spherical shape, elliptical spherical shape, plate shape, needle shape, columnar shape, etc. as used in the past. Thus, it is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, it is possible to relieve the stress of expansion and contraction and prevent deterioration when the primary particles are aggregated to form secondary particles, rather than being a single particle active material consisting of only primary particles.
In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so there is less expansion and contraction of the electrode during charge and discharge, and an electrode is produced. The mixing with the conductive material is also preferable because it can be easily mixed uniformly.

[5] The tap density of the tap density lithium-titanium composite oxide is preferably from ^{0.05g · cm -3, 0.1g · cm} -3 or more, and more preferably 0.2 g · ^{cm -3} or more, 0 particularly preferred .4g · ^{cm -3} or higher, and is preferably 2.8 g · ^{cm -3} or less, more preferably 2.4 g · ^{cm -3} or less, particularly preferably 2 g · ^{cm -3} or less. When the tap density of the lithium-titanium composite oxide is within the above range, a sufficient packing density can be secured when used as a negative electrode, and a contact area between the particles can be secured, so that the resistance between the particles hardly increases. It is easy to prevent the output resistance from increasing. Furthermore, since the space between the particles in the electrode is also appropriate, the flow path of the non-aqueous electrolyte solution can be secured, so that it is easy to prevent an increase in output resistance.

To measure the tap density of the lithium-titanium composite oxide, the sample is passed through a sieve having a mesh size of 300 μm, dropped into a 20 cm ³ tapping cell and filled up to the upper end surface of the cell, and then a powder density measuring device. Using, for example, a tap denser manufactured by Seishin Enterprise Co., Ltd., tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the lithium titanium composite oxide.

[6] Circularity When the circularity is measured as the spherical degree of the lithium titanium composite oxide, 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 lithium-titanium composite oxide is preferably closer to 1. Preferably, it is 0.10 or more, more preferably 0.80 or more, still more preferably 0.85 or more, and particularly preferably 0.90 or more. High current density charge / discharge characteristics generally improve as the circularity increases. Therefore, when the circularity is within the above range, the filling property of the negative electrode active material is not lowered, the increase in resistance between particles can be prevented, and the short time high current density charge / discharge characteristics can be prevented.

  The circularity of the lithium titanium composite oxide is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). Specifically, about 0.2 g of a sample is dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and an ultrasonic wave of 28 kHz is output at 60 W for 1 After irradiating for minutes, the detection range is specified as 0.6 to 400 μm, and the particle size is measured for particles in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the lithium titanium composite oxide in the present invention.

[7] Aspect ratio The aspect ratio of the lithium titanium composite oxide is preferably 1 or more, preferably 5 or less, more preferably 4 or less, still more preferably 3 or less, and particularly preferably 2 or less. When the aspect ratio is within the above range, streaking is less likely to occur when forming an electrode plate, and a uniform coated surface can be easily obtained. Therefore, it is possible to prevent deterioration of high current density charge / discharge characteristics for a short time. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the lithium titanium composite oxide.

  The aspect ratio of the lithium titanium composite oxide is measured by magnifying and observing the particles of the lithium titanium composite oxide with a scanning electron microscope. When 50 arbitrary lithium-titanium composite oxide particles fixed to the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted, and three-dimensional observation is performed. The longest diameter A of the particles and the shortest diameter B orthogonal to the same are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the lithium titanium composite oxide.

[8] Method for producing lithium-titanium composite oxide The method for producing lithium-titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention. A general method is used.
For example, a method of obtaining an active material by uniformly mixing a titanium source material such as titanium oxide, a source material of another element and a Li source of LiOH, Li ₂ CO ₃ , or LiNO ₃ as necessary, and firing at a high temperature. Can be mentioned.

In particular, various methods are conceivable for producing a spherical or elliptical active material. As an example, a titanium precursor material such as titanium oxide and, if necessary, a raw material material of another element are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create a spherical precursor. There is a method in which the active material is obtained by recovering and drying it as necessary, and then adding a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ and baking at a high temperature.

As another example, a titanium raw material such as titanium oxide and, if necessary, a raw material of another element are dissolved or pulverized and dispersed in a solvent such as water. A method of obtaining an active material by adding a Li source such as LiOH, Li ₂ CO ₃ , LiNO _{3 and the} like to an elliptical spherical precursor and baking at a high temperature can be mentioned.
As yet another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ and LiNO ₃ and a raw material of another element as necessary are dissolved or pulverized in a solvent such as water. There is a method in which it is dispersed and dried by a spray dryer or the like to obtain a spherical or elliptical precursor, which is then fired at a high temperature to obtain an active material.

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

<2-3-4. Structure, physical properties and preparation method of negative electrode>
About the negative electrode containing the said negative electrode active material, an electrode-izing method, a collector, and a nonaqueous electrolyte secondary battery, any one item or a plurality of items of (i) to (vi) shown below are simultaneously applied. It is desirable to satisfy.

(I) Negative electrode production Any known method can be used for the production of the negative electrode as long as the effects of the present invention are not significantly limited. 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.

(Ii) Current collector As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.
In addition, the shape of the current collector may be, for example, 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, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, and a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.

(Iii) Ratio of thickness of current collector and negative electrode active material layer The ratio of thickness of current collector and negative electrode active material layer is not particularly limited, but “(one side just before the non-aqueous electrolyte injection step) Negative electrode active material layer thickness) / (current collector thickness) "is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, and more preferably 0.1 or more. 4 or more is more preferable, and 1 or more is particularly preferable.

  When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

(Iv) Electrode density The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, and the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more. .2g · ^{cm -3} or more preferably, 1.3 g · ^{cm -3} or more, and also preferably 4g · ^{cm -3} or less, more preferably 3 g · ^{cm -3} or less, 2.5 g · cm ^{- 3} or less is more preferable, and 1.7 g · cm ⁻³ or less is particularly preferable. When the density of the negative electrode active material existing on the current collector is within the above range, the negative electrode active material particles are less likely to be destroyed, and the increase in initial irreversible capacity and the vicinity of the current collector / negative electrode active material interface It becomes easy to prevent deterioration of high current density charge / discharge characteristics due to a decrease in permeability of the non-aqueous electrolyte. Further, the conductivity between the negative electrode active materials can be secured, and the capacity per unit volume can be earned without increasing the battery resistance.

(V) Binder / Solvent, etc. The slurry for forming the negative electrode active material layer is usually prepared by adding a binder (binder), a thickener and the like to the solvent with respect to the negative electrode active material.
The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.

  Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile / butadiene rubber), rubbery polymers such as ethylene / propylene rubber; styrene / butadiene / styrene block copolymers or hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymer such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as vinyl acetate copolymer and propylene / α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymer Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. .

In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and make a slurry using a latex such as SBR.
In addition, these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.
The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable. When the ratio of the binder to the negative electrode active material is within the above range, the ratio of the binder that does not contribute to the battery capacity does not increase, so that the battery capacity is hardly reduced. Furthermore, the strength of the negative electrode is hardly lowered.

In particular, when the main component contains a rubbery polymer typified by SBR, the ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and 0% 6 mass% or more is more preferable, 5 mass% or less is preferable, 3 mass% or less is more preferable, and 2 mass% or less is still more preferable.
When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio of the binder to the negative electrode active material is preferably 1% by mass or more, more preferably 2% by mass or more, and 3% by mass. The above is more preferable, 15 mass% or less is preferable, 10 mass% or less is more preferable, and 8 mass% or less is still more preferable.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  When using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.6% by mass or more. Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is within the above range, the coating property is good. Furthermore, the ratio of the negative electrode active material in the negative electrode active material layer is also moderate, and the problem of a decrease in battery capacity and a problem of an increase in resistance between the negative electrode active materials are less likely to occur.

(Vi) Area of Negative Electrode Plate The area of the negative electrode plate is not particularly limited, but it is preferably designed to be slightly larger than the opposing positive electrode plate so that the positive electrode plate does not protrude from the negative electrode plate. Further, from the viewpoint of suppressing the life of a cycle in which charge and discharge are repeated and deterioration due to high temperature storage, it is preferable that the area be as close to the positive electrode as possible, because the ratio of electrodes that work more uniformly and effectively is increased and the characteristics are improved. In particular, when used with a large current, the design of the area of the negative electrode plate is important.

<2-4. Positive electrode>
The positive electrode used for the non-aqueous electrolyte secondary battery of the present invention will be described below.
<2-4-1. Cathode active material>
The positive electrode active material used for the positive electrode will be described below.

(1) Composition The positive electrode active material is a transition metal oxide containing at least Ni and Co, and more than 50 mol% of the transition metal is Ni and Co, and can electrochemically occlude and release metal ions. There is no particular limitation as long as it is, but, for example, a material that can electrochemically occlude and release lithium ions is preferable. It contains lithium, at least Ni, and Co, and more than 50 mol% of the transition metal is Ni. A transition metal oxide which is Co is preferred. This is because Ni and Co are suitable for use as a positive electrode material of a secondary battery because of the oxidation-reduction potential, and are suitable for high capacity applications.

The transition metal component of the lithium transition metal oxide includes Ni and Co as essential elements, but other metals include Mn, V, Ti, Cr, Fe, Cu, Al, Mg, Zr, Er, and the like. Mn, Ti, Fe, Al, Mg, Zr and the like are preferable. Specific examples of the lithium transition metal oxide include, for example, LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.80 Co _0.15 Al _0.05 O _2, LiNi _0.33 Co _{0. 33} Mn _0.33 O ₂ , Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , Li _1.05 Ni _0.50 Mn _0.29 Co _0.21 O ₂ etc. are mentioned.

Among these, a transition metal oxide represented by the following composition formula (2) is preferable.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ (2)
(In formula (2), 0.9 ≦ a1 ≦ 1.1, 0.3 ≦ b1 ≦ 0.9, 0.1 ≦ c1 ≦ 0.5, 0.0 ≦ d1 ≦ 0.5 are shown. 0.5 ≦ b1 + c1 and b1 + c1 + d1 = 1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)
In the composition formula (2), it is preferable to show a numerical value of 0.1 ≦ d1 ≦ 0.5.
Since the composition ratio of Ni and Co and the composition ratio of other metal species are as specified, the transition metal is difficult to elute from the positive electrode, and even if it elutes, Ni and Co are not contained in the non-aqueous secondary battery. This is because the adverse effect of is small.

Among these, a transition metal oxide represented by the following composition formula (3) is more preferable.
Li _a2 Ni _b2 Co _c2 M _d2 O ₂ (3)
(In formula (3), 0.9 ≦ a2 ≦ 1.1, 0.3 ≦ b2 ≦ 0.9, 0.1 ≦ c2 ≦ 0.5, 0.0 ≦ d2 ≦ 0.5 C2 ≦ b2 and 0.6 ≦ b2 + c2 and b2 + c2 + d2 = 1, where M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
In the composition formula (3), it is preferable to show a numerical value of 0.1 ≦ d2 ≦ 0.5.
When Ni and Co are the main components and the composition ratio of Ni is the same as or larger than the composition ratio of Co, it is stable and takes out a high capacity when used as a positive electrode for a non-aqueous secondary battery. Because it becomes possible.

Among these, a transition metal oxide represented by the following composition formula (4) is more preferable.
Li _a3 Ni _b3 Co _c3 M _d3 O ₂ (4)
(In formula (4), 0.9 ≦ a3 ≦ 1.1, 0.35 ≦ b3 ≦ 0.9, 0.1 ≦ c3 ≦ 0.5, 0.0 ≦ d3 ≦ 0.5 are shown. C3 <b3 and 0.6 ≦ b3 + c3 and b3 + c3 + d3 = 1, where M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
In the composition formula (4), it is preferable to show a numerical value of 0.1 ≦ d3 ≦ 0.5.

Among these, a transition metal oxide represented by the following composition formula (6) is particularly preferable.
Li _a4 Ni _b4 Co _c4 M _d4 O ₂ (6)
(In formula (6), 0.9 ≦ a4 ≦ 1.1, 0.45 ≦ b4 ≦ 0.9, 0.1 ≦ c4 ≦ 0.5, 0.0 ≦ d4 ≦ 0.5 are shown. C4 <2 + b4 and 0.6 ≦ b4 + c4 and b4 + c4 + d4 = 1, where M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.
In the composition formula (6), it is preferable to show a numerical value of 0.1 ≦ d4 ≦ 0.5.
It is because it becomes possible to take out especially high capacity | capacitance when it is used as a non-aqueous secondary battery positive electrode because it is said composition.

Further, two or more of the positive electrode active materials may be mixed and used. Similarly, at least one of the positive electrode active materials may be mixed with another positive electrode active material. Examples of other positive electrode active materials include transition metal oxides, transition metal phosphate compounds, transition metal silicate compounds, and transition metal borate compounds not listed above.
Among these, lithium manganese composite oxide having a spinel structure and a lithium-containing transition metal phosphate compound having an olivine structure are preferable. Specific examples of the lithium manganese composite oxide having a spinel structure include LiMn ₂ O ₄ , LiMn _1.8 Al _0.2 O ₄ , and LiMn _1.5 Ni _0.5 O ₄ . This is because the structure is most stable, oxygen is not easily released even when the non-aqueous electrolyte secondary battery is abnormal, and safety is excellent.
Further, as the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO _{4 3} ) Iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , manganese phosphates such as LiMnPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and the like substituted with other metals.

Among them, a lithium iron phosphate compound is preferable because iron is a very inexpensive metal with abundant resources and less harmful. That is, among the above specific examples, LiFePO ₄ can be given as a more preferable specific example.

(2) Surface coating A material having a composition different from that of the main constituent of the positive electrode active material (hereinafter referred to as “surface adhering substance” as appropriate) may be used on the surface of the positive electrode active material. . Examples of surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Examples thereof include sulfates such as calcium sulfate and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate, and carbon.

  These surface adhering substances are, for example, a method in which they are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, and then dried. Then, it can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously. In addition, when attaching carbon, the method of attaching carbonaceous material mechanically later, for example in the form of activated carbon etc. can also be used.

The mass of the surface adhering substance adhering to the surface of the positive electrode active material is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more with respect to the mass of the positive electrode active material. Further, it is preferably 20% or less, more preferably 10% or less, still more preferably 5% or less.
The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material, and can improve the battery life. Moreover, when the adhesion amount is within the above range, the effect can be sufficiently exhibited, and resistance is hardly increased without inhibiting the entry and exit of lithium ions.

(3) Shape As the shape of the positive electrode active material particles, a lump shape, a polyhedron shape, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, and the like, which are conventionally used, are used. The primary particles may be aggregated to form secondary particles, and the shape of the secondary particles may be spherical or elliptical.

(4) Tap Density Tap density positive electrode active material, preferably at 0.5 g · ^{cm -3} or more, more preferably 1.0 g · ^{cm -3} or more, 1.5 g · ^{cm -3} or more is more preferable. Further, it is preferably 4.0 g · cm ⁻³ or less, and more preferably 3.7 g · cm ⁻³ or less.

  By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. When the tap density of the positive electrode active material is within the above range, the amount of the dispersion medium necessary for forming the positive electrode active material layer becomes appropriate, and the amount of the conductive material and binder is also appropriate. The positive electrode active material filling rate is not limited, and the battery capacity is less affected.

The tap density of the positive electrode active material is measured by passing a sieve having a mesh size of 300 μm, dropping a sample onto a 20 cm ³ tapping cell to fill the cell volume, Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the positive electrode active material in the present invention.

(5) Median diameter d50
The median diameter d50 (secondary particle diameter when primary particles are aggregated to form secondary particles) of the positive electrode active material particles can be measured using a laser diffraction / scattering particle size distribution analyzer. it can.
The median diameter d50 is preferably 0.1 μm or more, more preferably 0.5 μm or more, further preferably 1 μm or more, particularly preferably 3 μm or more, preferably 30 μm or less, more preferably 20 μm or less, and more preferably 16 μm. The following is more preferable, and 15 μm or less is particularly preferable. When the median diameter d50 is within the above range, it becomes easy to obtain a high bulk density product, and further, it does not take time for the diffusion of lithium in the particles, so that the battery characteristics are hardly deteriorated. In addition, when the positive electrode of a battery is produced, that is, when an active material, a conductive material, a binder, and the like are slurried with a solvent and applied in a thin film form, streaking is less likely to occur.

In addition, the filling property at the time of positive electrode preparation can be further improved by mixing two or more positive electrode active materials having different median diameters d50 in an arbitrary ratio.
The median diameter d50 of the positive electrode active material is measured using a 0.1 mass% sodium hexametaphosphate aqueous solution as a dispersion medium, and using a particle size distribution meter (for example, LA-920 manufactured by Horiba, Ltd.) In contrast, after the ultrasonic dispersion for 5 minutes, the measurement refractive index is set to 1.24 and measured.

(6) Average primary particle diameter When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.01 μm or more, more preferably 0.05 μm or more, It is more preferably 0.08 μm or more, particularly preferably 0.1 μm or more, and preferably 3 μm or less, more preferably 2 μm or less, still more preferably 1 μm or less, and particularly preferably 0.6 μm or less. Within the above range, it becomes easy to form spherical secondary particles, the powder filling property becomes appropriate, and a sufficient specific surface area can be secured, so that deterioration of battery performance such as output characteristics can be suppressed. .
The average primary particle size of the positive electrode active material is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

(7) BET specific surface area As for the BET specific surface area of the positive electrode active material, the value of the specific surface area measured using the BET method is preferably 0.2 m ² · g ⁻¹ or more, and 0.3 m ² · g ^−1. or more, and further preferably 0.4 m ² · ^{g -1} or higher, and preferably not more than 4.0m ² · ^{g -1,} 2.5m more preferably ² · ^{g -1} or less, 1.5 m ² · g ⁻¹ or less is more preferable. When the value of the BET specific surface area is within the above range, it is easy to prevent a decrease in battery performance. Furthermore, a sufficient tap density can be ensured, and the applicability at the time of forming the positive electrode active material becomes good.

  The BET specific surface area of the positive electrode active material is measured using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken). Specifically, the sample was pre-dried for 30 minutes at 150 ° C. under a nitrogen flow, and then the nitrogen-helium mixed gas accurately adjusted so that the relative pressure of nitrogen to the atmospheric pressure was 0.3. Is measured by a nitrogen adsorption BET one-point method using a gas flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the positive electrode active material in the present invention.

(8) Method for Producing Positive Electrode Active Material The method for producing the positive electrode active material is not particularly limited as long as it does not exceed the gist of the present invention, but there are several methods, which are common as methods for producing inorganic compounds. The method is used.
In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, transition metal source materials such as transition metal nitrates and sulfates, and source materials of other elements as necessary. Is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO There is a method in which an active material is obtained by adding a Li source such as ₃ and baking at a high temperature.

In addition, as an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides and the like, and if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dry-molded with a spray dryer or the like to obtain a spherical or oval spherical precursor, and a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ is added to the precursor and calcined at a high temperature to obtain an active material Is mentioned.

Examples of other methods include transition metal source materials such as transition metal nitrates, sulfates, hydroxides, oxides, Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and other elements as necessary. The raw material is dissolved or pulverized and dispersed in a solvent such as water, and then dried and molded with a spray drier or the like to obtain a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material. Can be mentioned.

<2-4-2. Positive electrode structure and fabrication method>
Below, the structure of the positive electrode used for this invention and its preparation method are demonstrated.
(Production method of positive electrode)
The positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be produced by any known method. For example, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are dissolved in a liquid medium Alternatively, a positive electrode can be obtained by forming a positive electrode active material layer on the current collector by dispersing it as a slurry, applying this to a positive electrode current collector and drying it.

  The content of the positive electrode active material in the positive electrode active material layer is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and preferably 99.9% by mass or less. Yes, 99 mass% or less is more preferable. When the content of the positive electrode active material is within the above range, a sufficient electric capacity can be secured. Furthermore, the strength of the positive electrode is sufficient. In addition, the positive electrode active material powder in this invention may be used individually by 1 type, and may use together 2 or more types of a different composition or different powder physical properties by arbitrary combinations and ratios. When two or more active materials are used in combination, the composite oxide containing lithium and manganese is preferably used as a powder component. Cobalt or nickel is an expensive metal with a small amount of resources, and it is not preferable in terms of cost because it uses a large amount of active material in large batteries that require high capacity, such as for automobiles. This is because it is desirable to use manganese as a main transition metal.

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

  The content of the conductive material in the positive electrode active material layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 1% by mass or more, and preferably 50% by mass or less. 30 mass% or less is more preferable, and 15 mass% or less is still more preferable. When the content is within the above range, sufficient conductivity can be secured. Furthermore, it is easy to prevent a decrease in battery capacity.

(binder)
The binder used for manufacturing the positive electrode active material layer is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used when manufacturing the electrode.
In the case of the coating method, it is not particularly limited as long as it is a material that is dissolved or dispersed in a liquid medium used at the time of electrode production. Specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, and cellulose. Resin polymers such as nitrocellulose; rubbery polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber; styrene butadiene Styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof etc Thermoplastic elastomeric polymers; soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF) ), Fluorinated polymers such as polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer; polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions), etc. It is done. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The binder content in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, further preferably 3% by mass or more, and preferably 80% by mass or less. 60 mass% or less is more preferable, 40 mass% or less is still more preferable, and 10 mass% or less is especially preferable. When the ratio of the binder is within the above range, the positive electrode active material can be sufficiently retained, and the mechanical strength of the positive electrode can be secured, so that battery performance such as cycle characteristics is improved. Furthermore, it also leads to avoiding a decrease in battery capacity and conductivity.

(Liquid medium)
The liquid medium used for preparing the slurry for forming the positive electrode active material layer is a solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. If it exists, 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 medium include water, a mixed medium of alcohol and water, and the like. Examples of organic media include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

(Thickener)
When an aqueous medium is used as the liquid medium for forming the slurry, it is preferable to make a slurry using a thickener and a latex such as styrene butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry.
The thickener is not limited as long as the effect of the present invention is not significantly limited. Specifically, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof Etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  When a thickener is used, the ratio of the thickener to the positive electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further 0.6% by mass or more. It is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. When the content is within the above range, the coating property is improved, and further, the ratio of the active material in the positive electrode active material layer becomes sufficient, so that the problem that the battery capacity decreases and the resistance between the positive electrode active materials increases. It is easier to avoid problems.

(Consolidation)
In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by applying the slurry to the current collector and drying is preferably consolidated by a hand press, a roller press or the like. The density of the positive electrode active material layer is preferably 1 g · cm ⁻³ or more, more preferably 1.5 g · cm ⁻³ or more, particularly preferably 2 g · cm ⁻³ or more, and preferably 4 g · cm ⁻³ or less. 3.5 g · cm ⁻³ or less is more preferable, and 3 g · cm ⁻³ or less is particularly preferable.
When the density of the positive electrode active material layer is within the above range, the non-aqueous electrolyte solution permeation into the vicinity of the current collector / active material interface does not decrease, and the charge / discharge characteristics particularly at a high current density are good. Become. Furthermore, the electrical conductivity between the active materials is difficult to decrease, and the battery resistance is difficult to increase.

(Current collector)
There is no restriction | limiting in particular as a material of a positive electrode electrical power collector, A well-known thing can be used arbitrarily. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc. A carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape.
The thickness of the current collector is arbitrary, but is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and preferably 1 mm or less, more preferably 100 μm or less, and further preferably 50 μm or less. preferable. When the thickness of the current collector is within the above range, sufficient strength required for the current collector can be ensured. Furthermore, the handleability is also improved.

The thickness ratio between the current collector and the positive electrode active material layer is not particularly limited, but (active material layer thickness on one side immediately before non-aqueous electrolyte injection) / (current collector thickness) is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, preferably 0.1 or more, more preferably 0.4 or more, and particularly preferably 1 or more.
When the ratio of the thickness of the current collector to the positive electrode active material layer is within the above range, the current collector hardly generates heat due to Joule heat during high current density charge / discharge. Furthermore, it becomes difficult for the volume ratio of the current collector to the positive electrode active material to increase, and a decrease in battery capacity can be prevented.

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

(Discharge capacity)
When the non-aqueous electrolyte of the present invention is used, the electric capacity of the battery element housed in one battery exterior of the non-aqueous electrolyte secondary battery (electric capacity when the battery is discharged from a fully charged state to a discharged state) ) Is 1 ampere hour (Ah) or more, since the effect of improving the low temperature discharge characteristics is increased. Therefore, the positive electrode plate has a fully charged discharge capacity, preferably 3 Ah (ampere hour), more preferably 4 Ah or more, preferably 100 Ah or less, more preferably 70 Ah or less, and particularly preferably 50 Ah. Design to be as follows.

  Within the above range, the voltage drop due to the electrode reaction resistance does not become excessive when a large current is taken out, and the deterioration of the power efficiency can be prevented. Furthermore, the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge does not become too large, the durability of repeated charge / discharge is inferior, and the heat dissipation efficiency is poor against sudden heat generation during abnormalities such as overcharge and internal short circuit. The phenomenon of becoming can be avoided.

(Thickness of positive plate)
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, the thickness of the positive electrode active material layer minus the thickness of the current collector is relative to one side of the current collector. 10 μm or more is preferable, 20 μm or more is more preferable, 200 μm or less is preferable, and 100 μm or less is more preferable.

<2-5. 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.
There is no restriction | limiting in particular about the material and shape of a separator, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily. 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 properties is used. Is preferred.

  As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aramid resins, 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 preferably 1 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, and preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. . When the thickness of the separator is within the above range, the insulation and mechanical strength are good. Furthermore, the battery performance such as rate characteristics can be prevented from being lowered, and the energy density of the non-aqueous electrolyte secondary battery as a whole can be prevented from being lowered.

  Furthermore, when a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary, but is preferably 20% or more, more preferably 35% or more, and further 45% or more. Preferably, it is 90% or less, more preferably 85% or less, and further preferably 75% or less. When the porosity is within the above range, the membrane resistance does not increase excessively, and deterioration of rate characteristics can be suppressed. Furthermore, the mechanical strength of the separator becomes appropriate, and a decrease in insulation can be suppressed.

Moreover, although the average pore diameter of a separator is also arbitrary, Preferably it is 0.5 micrometer or less, 0.2 micrometer or less is more preferable, Preferably it is 0.05 micrometer or more. When the average pore diameter is within the above range, short circuit is difficult to occur. Furthermore, the film resistance does not increase too much, and the rate characteristics can be prevented from deteriorating.
On the other hand, as the inorganic material, 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. Things are used.

  As a form of the separator, a thin film shape such as a nonwoven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing 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 separator obtained by forming a porous layer on both surfaces of a positive electrode using alumina particles having a 90% particle diameter of less than 1 μm and a fluororesin as a binder.

<2-6. Battery design>
(Electrode group)
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as electrode group occupancy) is preferably 40% or more, more preferably 50% or more, and preferably 95% or less, 90% The following is more preferable. When the electrode group occupancy is within the above range, the battery capacity is hardly reduced. In addition, since an appropriate gap space can be secured, the member expands due to the high temperature of the battery or the vapor pressure of the liquid component of the electrolyte increases, and the internal pressure rises. Various characteristics such as high-temperature storage can be deteriorated, and further, a case where a gas release valve that releases the internal pressure to the outside can be avoided.

(Current collection structure)
The current collecting structure is not particularly limited, but in order to more effectively realize the improvement of the discharge characteristics by the non-aqueous electrolyte solution of the present invention, it is necessary to make the structure to reduce the resistance of the wiring part and the joint part preferable. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.

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

(Protective element)
As a protective element, PTC (Positive Temperature Coefficient) thermistor that increases resistance when abnormal heat generation or excessive current flows, thermal fuse, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature at abnormal heat generation Examples thereof include a valve (current cutoff valve). 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 has a design that does not 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 (exterior case). There is no restriction | limiting in this exterior body, A well-known thing can be arbitrarily employ | adopted unless the effect of this invention is impaired remarkably.
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 or an aluminum alloy, a magnesium alloy, nickel, titanium, or a metal, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, a metal such as aluminum or an aluminum alloy, or a laminate film is preferably used.

In the outer case using the above metals, the metal is welded to each other by laser welding, resistance welding, ultrasonic welding, or a sealed sealing structure, or a caulking structure using the above metals through a resin gasket To do. 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.
The shape of the outer case 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.
Abbreviations of the compounds used in this example are shown below.

[Example 1-1, Comparative example 1-1]
[Preparation of non-aqueous electrolyte secondary battery]
<Preparation of non-aqueous electrolyte solution>
[Example 1-1]
In a dry argon atmosphere, 1 mol / L (as a concentration in a non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). Furthermore, 0.5% by mass of the sufficiently dried compound 1 (as a concentration in the non-aqueous electrolyte solution) was dissolved to prepare a non-aqueous electrolyte solution.
Using this non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced by the following method, and the following evaluation was performed.

[Comparative Example 1-1]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that Compound 1 was not dissolved, and the following evaluation was performed.

<Preparation of positive electrode>
90 parts by mass of lithium nickel manganese cobalt composite oxide (Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O ₂ ) as a positive electrode active material, 7 parts by mass of carbon black as a conductive material, binder 3 parts by mass of polyvinylidene fluoride (PVdF) as a mixture and slurried in N-methyl-2-pyrrolidone, uniformly applied to an aluminum foil having a thickness of 15 μm, dried, and then subjected to a roll press. A positive electrode was obtained.

<Production of negative electrode>
97.5 parts by mass of graphite powder, 150 parts by mass of an aqueous dispersion of carboxymethylcellulose sodium (concentration of 1% by mass of carboxymethylcellulose sodium) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (styrene-butadiene rubber) as a binder 2 parts by mass) and mixed with a disperser to form a slurry. The obtained slurry was uniformly applied to a 10 μm thick copper foil, dried, and roll-pressed to obtain a negative electrode.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the polyolefin separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The battery element thus obtained was wrapped with an aluminum laminate film, injected with the non-aqueous electrolyte solution described above, and then vacuum-sealed to produce a sheet-like non-aqueous electrolyte secondary battery.

[Evaluation of non-aqueous electrolyte secondary battery]
Initial charge / discharge In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery is 0.05 C (the current value at which the rated capacity based on the discharge capacity at 1 hour rate is discharged in 1 hour. The same applies hereinafter. The battery was charged for 10 hours and then rested for 3 hours, and then charged at a constant current of 0.2 C to 4.1 V. Further, after resting for 3 hours, constant current-constant voltage charging was performed at 0.2 C up to 4.1 V, and then constant current discharging was performed up to 3.0 V at 0.33 C. Thereafter, a charge / discharge cycle of 0.33 C constant current-constant voltage charge up to 4.1 V and a subsequent 0.33 C constant current discharge up to 3.0 V as one cycle was performed.
Furthermore, after charging with constant current-constant voltage at 0.33 C to 4.1 V, the battery was stabilized by storing it at 60 ° C. for 12 hours. Thereafter, a charge / discharge cycle of 0.33 C constant current-constant voltage charge up to 4.2 V at 25 ° C. and subsequent 0.33 C constant current discharge up to 3.0 V was performed.

-60 ° C cycle test After charging the battery that had been initially charged / discharged to 4.2V by 2C constant current method at 60 ° C, 500 cycles of charge / discharge to discharge to 3.0V by 2C constant current method were performed. It was. The ratio of the 500th cycle discharge capacity to the first cycle discharge capacity at this time was defined as “60 ° C. cycle capacity maintenance rate”.
Table 1 shows the 60 ° C. cycle capacity maintenance rate. That is, it can be said that the larger the value of the 60 ° C. cycle capacity retention rate shown in Table 1, the smaller the capacity deterioration and the better.

  As is clear from Table 1, in a non-aqueous electrolyte secondary battery using a positive electrode containing a transition metal oxide containing at least Ni and Co and 50 mol% or more of transition metals being Ni and Co, When the specific compound is contained in the non-aqueous electrolyte, the high-temperature cycle capacity retention rate increases.

[Example 2-1 and Comparative example 2-1]
[Preparation of non-aqueous electrolyte secondary battery]
<Preparation of non-aqueous electrolyte solution>
[Example 2-1]
Under a dry argon atmosphere, 1 mol / L (as a concentration in the non-aqueous electrolyte) of LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7). The dried compound 1 was dissolved in 0.3% by mass (as a concentration in the non-aqueous electrolyte solution) to prepare a non-aqueous electrolyte solution. Using this non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced by the following method, and the following evaluation was performed.

[Comparative Example 2-1]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that Compound 1 was not dissolved, and the following evaluation was performed.

<Preparation of positive electrode>
67.5 parts by mass of lithium manganate (Li _1.1 Mn _1.9 Al _0.1 O ₄ ) as the first positive electrode active material, lithium nickel manganese cobalt composite oxide (Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O ₂ ) 22.5 parts by mass, 5 parts by mass of carbon black as a conductive material, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder Were mixed and slurried in N-methyl-2-pyrrolidone, and this was uniformly applied to an aluminum foil having a thickness of 15 μm and dried, followed by roll pressing to obtain a positive electrode.

<Production of negative electrode>
97.5 parts by mass of graphite powder, 150 parts by mass of an aqueous dispersion of carboxymethylcellulose sodium (concentration of 1% by mass of carboxymethylcellulose sodium) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (styrene-butadiene rubber) as a binder 2 parts by mass) and mixed with a disperser to form a slurry. The obtained slurry was uniformly applied to a 10 μm thick copper foil, dried, and roll-pressed to obtain a negative electrode.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the polyolefin separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The battery element thus obtained was wrapped with an aluminum laminate film, injected with the non-aqueous electrolyte solution described above, and then vacuum-sealed to produce a sheet-like non-aqueous electrolyte secondary battery.

[Evaluation of non-aqueous electrolyte secondary battery]
-Initial charge / discharge In a 25 degreeC thermostat, the sheet-like non-aqueous electrolyte secondary battery was charged at constant current-constant voltage to 4.2 V at 0.1 C, and then discharged to 2.7 V at 0.1 C. Subsequently, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C, and then discharged to 2.7 V at 0.33 C. This was carried out for 2 cycles for a total of 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was kept at 60 ° C. for 24 hours to perform aging.

-55 degreeC cycle test In the 55 degreeC thermostat, after charging at constant current-constant voltage to 4.2V at 1C, the process of discharging to 2.7V at constant current of 1C was carried out for 199 cycles. The ratio of the capacity at the 199th cycle to the capacity at the first cycle was defined as “55 ° C. cycle capacity maintenance rate”.
Table 2 below shows the 55 ° C. cycle capacity maintenance rate.

  As is clear from Table 2, in the non-aqueous electrolyte secondary battery using a positive electrode containing at least Ni and Co, and a transition metal oxide in which 50 mol% or more of the transition metals is Ni and Co, When the specific compound is contained in the non-aqueous electrolyte, the high-temperature cycle capacity retention rate increases.

[Examples 3-1 to 3-6, Comparative example 3-1]
[Preparation of non-aqueous electrolyte secondary battery]
<Production of negative electrode>
97.5 parts by mass of graphite powder, 150 parts by mass of an aqueous dispersion of carboxymethylcellulose sodium (concentration of 1% by mass of carboxymethylcellulose sodium) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (styrene-butadiene rubber) as a binder 2 parts by mass) and mixed with a disperser to form a slurry. The obtained slurry was uniformly applied to a 10 μm thick copper foil, dried, and roll-pressed to obtain a negative electrode.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode of each Example and Comparative Example to be described later, the above negative electrode, and a polyolefin separator pre-impregnated with the non-aqueous electrolyte of each Example and Comparative Example to be described later were laminated in the order of positive electrode, separator and negative electrode. . The battery element thus obtained was placed in a 2032 coin-type battery can body and caulked with a caulking machine to produce a coin-type non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery thus obtained was evaluated as described below.

[Example 3-1]
<Preparation of positive electrode>
90 parts by mass of lithium nickel manganese cobalt composite oxide (Li _1.05 Ni _0.33 Mn _0.33 Co _0.33 O ₂ , hereinafter sometimes referred to as NMC333) as a positive electrode active material, carbon black as a conductive material 7 parts by mass and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed and slurried in N-methyl-2-pyrrolidone, and this was uniformly applied to an aluminum foil having a thickness of 15 μm. After drying, a roll press was performed to obtain a positive electrode.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, 1 mol / L (as a concentration in a non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). In addition, 0.3% by mass (as a concentration in the non-aqueous electrolyte solution) of the sufficiently dried compound 1 was dissolved to prepare a non-aqueous electrolyte solution.

<High temperature storage characteristics evaluation of non-aqueous electrolyte secondary battery>
Initial Charging / Discharging In a constant temperature bath at 25 ° C., a coin-type non-aqueous electrolyte secondary battery was charged at a constant current-constant voltage to 0.3 V at 0.33 C, and then discharged to 2.5 V at 0.33 C. This was performed for 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C to obtain a fully charged state.

-60 degreeC leaving test The non-aqueous electrolyte secondary battery of a full charge state was left to stand in a 60 degreeC thermostat for 6 days.

・ Large current tolerance measurement The non-aqueous electrolyte secondary battery after the 60 ° C. standing test was charged at a constant current-constant voltage to 0.3 V at 0.33 C, discharged to 2.5 V at a constant current of 1 C, and then 0 again. The battery was charged at a constant current-constant voltage to 4.2 V at 0.33 C, and then discharged to 2.5 V at a constant current of 2 C. The ratio (%) of the discharge capacity at 2C to the discharge capacity at 1C was defined as “high current resistance”.

[Example 3-2]
The same as Example 3-1 except that 0.3% by mass of the sufficiently dried compound 1 was added and 0.2% by mass of the sufficiently dried compound 2 was dissolved. A non-aqueous electrolyte secondary battery was prepared and evaluated.

[Example 3-3]
<Preparation of positive electrode>
67.5 parts by mass of lithium manganate (Li _1.1 Mn _1.9 Al _0.1 O ₄ ) as the first positive electrode active material, lithium nickel manganese cobalt composite oxide (NMC333) as the second positive electrode active material 22.5 parts by mass, 5 parts by mass of carbon black as a conductive material, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed and slurried in N-methyl-2-pyrrolidone, This was uniformly applied to a 15 μm-thick aluminum foil and dried, followed by roll pressing to obtain a positive electrode.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, 1 mol / L (as a concentration in a non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). In addition, 0.3% by mass (as a concentration in the non-aqueous electrolyte solution) of the sufficiently dried compound 1 was dissolved to prepare a non-aqueous electrolyte solution.

<High temperature storage characteristics evaluation of non-aqueous electrolyte secondary battery>
Initial Charging / Discharging In a constant temperature bath at 25 ° C., a coin-type non-aqueous electrolyte secondary battery was charged at a constant current-constant voltage to 0.3 V at 0.33 C, and then discharged to 2.5 V at 0.33 C. This was performed for 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C to obtain a fully charged state.

-60 degreeC leaving test The non-aqueous electrolyte secondary battery of a full charge state was left to stand in a 60 degreeC thermostat for 6 days.

・ Large current tolerance measurement The non-aqueous electrolyte secondary battery after the 60 ° C. standing test was charged at a constant current-constant voltage to 0.3 V at 0.33 C, discharged to 2.5 V at a constant current of 1 C, and then 0 again. The battery was charged at a constant current-constant voltage to 4.2 V at 0.33 C, and then discharged to 2.5 V at a constant current of 2 C. The ratio (%) of the discharge capacity at 2C to the discharge capacity at 1C was defined as “high current resistance”.

[Example 3-4]
The same as Example 3-3, except that the fully dried compound 1 was added to 0.3% by mass, and the non-aqueous electrolyte solution in which 0.2% by mass of the sufficiently dried compound 2 was dissolved was used. A non-aqueous electrolyte secondary battery was prepared and evaluated.

[Example 3-5]
<Preparation of positive electrode>
90 parts by mass of lithium nickel manganese cobalt composite oxide (Li _1.05 Ni _0.50 Mn _0.29 Co _0.21 O ₂ , hereinafter sometimes referred to as NMC532) as a positive electrode active material, carbon black as a conductive material 7 parts by mass and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed and slurried in N-methyl-2-pyrrolidone, and this was uniformly applied to an aluminum foil having a thickness of 15 μm. After drying, a roll press was performed to obtain a positive electrode.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, 1 mol / L (as a concentration in a non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). In addition, 0.3% by mass (as a concentration in the non-aqueous electrolyte solution) of the sufficiently dried compound 1 was dissolved to prepare a non-aqueous electrolyte solution.

<High temperature storage characteristics evaluation of non-aqueous electrolyte secondary battery>
Initial Charging / Discharging In a constant temperature bath at 25 ° C., a coin-type non-aqueous electrolyte secondary battery was charged at a constant current-constant voltage to 0.3 V at 0.33 C, and then discharged to 2.5 V at 0.33 C. This was performed for 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C to obtain a fully charged state.

-60 degreeC leaving test The non-aqueous electrolyte secondary battery of a full charge state was left to stand in a 60 degreeC thermostat for 6 days.

・ Large current tolerance measurement The non-aqueous electrolyte secondary battery after the 60 ° C. standing test was charged at a constant current-constant voltage to 0.3 V at 0.33 C, discharged to 2.5 V at a constant current of 1 C, and then 0 again. The battery was charged at a constant current-constant voltage to 4.2 V at 0.33 C, and then discharged to 2.5 V at a constant current of 2 C. The ratio (%) of the discharge capacity at 2C to the discharge capacity at 1C was defined as “high current resistance”.

[Example 3-6]
<Preparation of positive electrode>
95 parts by mass of lithium nickel cobalt aluminum composite oxide (Li _0.98 Ni _0.81 Co _0.15 Al _0.04 O ₂ , hereinafter sometimes referred to as NCA) as a positive electrode active material, carbon black as a conductive material 3 parts by mass and 2 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed and slurried in N-methyl-2-pyrrolidone, and this was uniformly applied to an aluminum foil having a thickness of 15 μm. After drying, a roll press was performed to obtain a positive electrode.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, 1 mol / L (as a concentration in a non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). In addition, 0.3% by mass (as a concentration in the non-aqueous electrolyte solution) of the sufficiently dried compound 1 was dissolved to prepare a non-aqueous electrolyte solution.

<High temperature storage characteristics evaluation of non-aqueous electrolyte secondary battery>
Initial Charging / Discharging In a constant temperature bath at 25 ° C., a coin-type non-aqueous electrolyte secondary battery was charged at a constant current-constant voltage to 0.3 V at 0.33 C, and then discharged to 2.5 V at 0.33 C. This was performed for 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C to obtain a fully charged state.

-60 degreeC leaving test The non-aqueous electrolyte secondary battery of a full charge state was left to stand in a 60 degreeC thermostat for 6 days.

・ Large current tolerance measurement The non-aqueous electrolyte secondary battery after the 60 ° C. standing test was charged at a constant current-constant voltage to 0.3 V at 0.33 C, discharged to 2.5 V at a constant current of 1 C, and then 0 again. The battery was charged at a constant current-constant voltage to 4.2 V at 0.33 C, and then discharged to 2.5 V at a constant current of 2 C. The ratio (%) of the discharge capacity at 2C to the discharge capacity at 1C was defined as “high current resistance”.

[Comparative Example 3-1]
<Preparation of positive electrode>
97 parts by mass of lithium cobalt composite oxide (Li _1.02 Co _0.98 Mg _0.01 Al _0.01 O ₂ , hereinafter sometimes referred to as LCO) as a positive electrode active material, 1 carbon black as a conductive material .5 parts by mass and 1.5 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed and slurried in N-methyl-2-pyrrolidone, and this was uniformly formed into an aluminum foil having a thickness of 15 μm. After coating and drying, a roll press was performed to obtain a positive electrode.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, 1 mol / L (as a concentration in a non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). In addition, 0.3% by mass (as a concentration in the non-aqueous electrolyte solution) of the sufficiently dried compound 1 was dissolved to prepare a non-aqueous electrolyte solution.

<High temperature storage characteristics evaluation of non-aqueous electrolyte secondary battery>
Initial Charging / Discharging In a constant temperature bath at 25 ° C., a coin-type non-aqueous electrolyte secondary battery was charged at a constant current-constant voltage to 0.3 V at 0.33 C, and then discharged to 2.5 V at 0.33 C. This was performed for 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C to obtain a fully charged state.

-60 degreeC leaving test The non-aqueous electrolyte secondary battery of a full charge state was left to stand in a 60 degreeC thermostat for 6 days.

・ Large current tolerance measurement The non-aqueous electrolyte secondary battery after the 60 ° C. standing test was charged at a constant current-constant voltage to 0.3 V at 0.33 C, discharged to 2.5 V at a constant current of 1 C, and then 0 again. The battery was charged at a constant current-constant voltage to 4.2 V at 0.33 C, and then discharged to 2.5 V at a constant current of 2 C. The ratio (%) of the discharge capacity at 2C to the discharge capacity at 1C was defined as “high current resistance”.

[Reference Example 3-1]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 3-1, except that Compound 1 was not dissolved in the non-aqueous electrolyte.

[Reference Example 3-2]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 3-3 except that Compound 1 was not dissolved in the non-aqueous electrolyte.

[Reference Example 3-3]
A non-aqueous electrolyte secondary battery was produced and evaluated in the same manner as Example 3-5 except that Compound 1 was not dissolved in the non-aqueous electrolyte.

[Reference Example 3-4]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 3-6 except that Compound 1 was not dissolved in the non-aqueous electrolyte.

[Reference Example 3-5]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as Comparative Example 3-1, except that Compound 1 was not dissolved in the non-aqueous electrolyte.

  Table 3 below shows the ratio of deterioration due to the addition of Compound 1 for large current resistance. That is, for Examples 3-1 and 3-2, the deterioration from the large current resistance of Reference Example 3-1 was observed. For Examples 3-3 and 3-4, the deterioration from the large current resistance of Reference Example 3-2 was observed. For Example 3-5, the deterioration from the large current resistance of Reference Example 3-3, and for Example 3-6, the deterioration from the high current resistance of Reference Example 3-4, Comparative Example About 3-1, the deterioration part from the large current tolerance of the reference example 3-5 is shown.

For example, the large current resistance deterioration value of Example 3-1 is
{Value of Reference Example 3-1 (%)}-{Value of Example 3-1 (%)}
And the value is preferably small.

  As apparent from Table 3, in the non-aqueous electrolyte secondary battery using the positive electrode containing at least Ni and Co, and containing no transition metal oxide in which 50 mol% or more of the transition metals is Ni and Co, When a specific compound is included in the non-aqueous electrolyte, the large current resistance is remarkably impaired, whereas in the non-aqueous electrolyte secondary battery using the positive electrode containing the transition metal oxide, Even if it contains a specific compound, the large current resistance hardly deteriorates.

According to the non-aqueous electrolyte solution of the present invention, it is possible to provide a battery that achieves both high-temperature life and suppression of deterioration of a large current capacity after being left at high temperature. Therefore, the non-aqueous electrolyte solution is a non-aqueous electrolyte secondary battery. Can be suitably used in all fields such as an electronic device in which is used. Moreover, it can utilize suitably also in electrolytic capacitors, such as a lithium ion capacitor using a non-aqueous electrolyte solution.
The application of the non-aqueous electrolyte solution 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 of applications include laptop computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, mobile audio players, small video cameras, LCD TVs, handy cleaners, transceivers, electronic notebooks, calculators, and memories. Cards, portable tape recorders, radios, backup power supplies, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game machines, watches, electric tools, strobes, cameras, etc.

Claims (7)

The metal ions A capable of absorbing and desorbing transition metal oxide contains at least Ni and Co, Ri is Ni and Co der least 50 mole% of the transition metals, Ru is represented by the following formula (4) A positive electrode containing a transition metal oxide;

(In formula (4), 0.9 ≦ a3 ≦ 1.1, 0.35 ≦ b3 ≦ 0.9, 0.1 ≦ c3 ≦ 0.5, 0.0 ≦ d3 ≦ 0.5 are shown. C3 <b3 and 0.6 ≦ b3 + c3 and b3 + c3 + d3 = 1, where M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
A negative electrode capable of occluding and releasing metal ions;
A nonaqueous electrolyte secondary batteries and a nonaqueous electrolyte solution containing an electrolyte dissolved in the nonaqueous solvent and the nonaqueous solvent,
The non-aqueous electrolyte secondary battery includes a compound having a structure represented by the following general formula (1).

(In the formula ^(1), R 1 ~R ^3, which may be the being the same or different, is an organic group having 1 to 20 carbon atoms that may have a substituent. However, R ¹ at least one of to R ³ is a carbon - carbon unsaturated bond or a cyano group). 2. In the general formula (1), R ^{1 to} R ³ may be the same as or different from each other, and are an organic group having 1 to 10 carbon atoms that may have a substituent. The non-aqueous electrolyte secondary battery described in 1. ^3. The non-aqueous electrolyte secondary battery according to claim 1, wherein in the general formula (1), at least one of R ^{1 to} R ³ is an organic group having a carbon-carbon unsaturated bond. 4. The non-aqueous system according to claim 1, wherein in the general formula (1), the organic group having a carbon-carbon unsaturated bond is a group selected from the group consisting of an allyl group and a methallyl group. Electrolyte secondary battery . The non-aqueous electrolyte solution, a compound having a structure represented by the general formula (1), wherein for the non-aqueous electrolyte solution the total amount, contains at least 0.01 wt% 10.0 wt% or less, claims The non-aqueous electrolyte secondary battery according to any one of 1 to 4. The non-aqueous electrolyte includes a cyclic carbonate having a fluorine atom, a cyclic carbonate having a carbon-carbon unsaturated bond, a difluorophosphate, a fluorosulfate, a compound having an isocyanato group, a compound having a cyano group, and a cyclic sulfonate ester. And a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, comprising at least one compound selected from the group consisting of dicarboxylic acid complex salts. The non-aqueous electrolyte solution contains a cyclic carbonate and a chain carbonate as the non-aqueous solvent, and contains at least two types of chain carbonates as the chain carbonate. Non-aqueous electrolyte secondary battery .