JP2015195202A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for enhancement of a nonaqueous electrolyte secondary battery in high-load discharge characteristic and high-temperature cycle characteristic.SOLUTION: A nonaqueous electrolyte secondary battery comprises: a nonaqueous electrolyte containing a compound expressed by the formula (1); and a negative electrode including a negative electrode active material consisting of a carbonaceous material. (Rto Rindependently represent H, F or a fluorine-substituted/unsubstituted carbon hydride group; at least one of Rto Ris F or fluorine-substituted/unsubstituted carbon hydride group; if Rto Rinclude F, at least four or more of Rto Rinclude F; n is 0 or 1; if n=0, an aromatic ring and S are directly bonded with each other.)

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, the demand for higher performance of non-aqueous electrolyte batteries is increasing, and there is a strong demand for improvement of various characteristics of secondary batteries.

In lithium non-aqueous electrolyte secondary batteries, 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 are used. 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 nonaqueous electrolytic solution containing a solute (electrolyte) 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, non-aqueous solvents in non-aqueous electrolyte solutions Various studies have been made on electrolytes.

  For example, Patent Document 1 discloses a lithium manganese secondary battery including a positive electrode using a lithium manganese composite oxide as an active material, a negative electrode using metallic lithium or an alloy thereof, or a lithium compound, and a nonaqueous electrolytic solution. A technique for providing a lithium manganese secondary battery having excellent charge / discharge cycle characteristics by providing a dehydrating agent is disclosed. In this document, it is disclosed that by containing various dehydrating agents in the positive electrode in advance, the elution of manganese is small and the initial capacity and the capacity retention rate after 10 cycles are improved.

In Patent Document 2, after a cycle test at 25 ° C. and 45 ° C., using a mixed solvent of a chain carbonate ester, a saturated cyclic carbonate ester and an unsaturated cyclic carbonate ester, and a non-aqueous electrolyte containing a specific chain isocyanate compound. It is disclosed that the capacity retention rate of the battery is improved.
In Patent Document 3, in a secondary battery including a specific negative electrode having silicon as a constituent element, an initial charge / discharge characteristic at 23 ° C. is obtained by using an electrolyte solution containing an isocyanate compound having an isocyanate group and an electron-withdrawing group. It is disclosed that the cycle characteristics are improved while ensuring the above.

Patent Document 4 simultaneously uses a negative electrode active material made of a carbonaceous material having a specific surface oxygen content and a nonaqueous electrolytic solution containing a compound having an isocyanate group such as 1,6-diisocyanatohexane. Thus, a technique for improving the high-temperature cycle characteristics and realizing a battery with low degradation of the low-temperature discharge characteristics is disclosed.
Non-Patent Document 1 discloses a technique in which an electrolytic solution using a mixture of tetramethylene sulfone and paratoluenesulfonyl isocyanate is excellent in thermal stability and contributes to improvement in lithium ion battery characteristics.

JP 2000-285661 A JP 2006-164759 A JP 2009-245923 A JP 2013-38072 A

Journal of Power Sources 202 (2012) 322-331

  However, the demand for improving the characteristics of non-aqueous electrolyte secondary batteries in recent years is increasing, and various performances such as energy density, output performance, life, high temperature resistance, low temperature characteristics, and high load discharge characteristics are at a high level. Such secondary batteries have not been achieved yet, including the techniques disclosed in Patent Documents 1 to 4 and Non-Patent Document 1 described above. In particular, there is a problem that it is difficult to improve the high-temperature cycle characteristics while suppressing an increase in the initial impedance of the secondary battery. In use in automobiles and the like, the resistance of the battery is often a problem, and since long-term reliability exceeding 10 years is required as an application, it has been particularly a problem in recent years.

  Further, according to the study by the inventors of the present invention, in the method of incorporating the dehydrating material described in Patent Document 1 into the positive electrode, paratoluenesulfonyl isocyanate is water vapor in the air in the subsequent electrode manufacturing and battery manufacturing processes. It has been found that the quality changes. Moreover, when the electrolyte solution containing the benzenesulfonyl isocyanate described in Patent Document 2 and Patent Document 3 was used, a problem was found that the high-load discharge characteristics deteriorated. Furthermore, according to the study by the inventors of the present invention, when the electrolytic solution containing 1,6-diisocyanatohexane described in Patent Document 4 is used, the initial impedance is remarkably increased. It was found. An electrolyte solution containing para-toluenesulfonyl isocyanate described in Non-Patent Document 1 in tetramethylene sulfone has a very high viscosity, and the battery used for the electrolyte solution cannot be charged / discharged, so that there is a problem that it cannot be put into practical use. It was issued.

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 secondary battery that is excellent in high-load discharge characteristics and excellent in high-temperature cycle characteristics while suppressing an increase in initial impedance with respect to a non-aqueous electrolyte secondary battery.
As a result of intensive studies in order to solve the above problems, the present inventors have found that the above problems can be solved by including a specific compound in the non-aqueous electrolyte solution, and the present invention has been completed. .

The gist of the present invention is as follows.
[1]
A non-aqueous electrolyte solution comprising: a positive electrode capable of inserting and extracting metal ions; a negative electrode capable of storing and releasing metal ions; and a non-aqueous electrolyte solution including a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. A secondary battery,
The negative electrode active material of the negative electrode is a carbonaceous material,
The non-aqueous electrolyte contains at least one of a cyclic carbonate and a chain carbonate,
Furthermore, the non-aqueous electrolyte secondary battery characterized by containing the compound represented by following General formula (1).

(In formula (1), R ^{1 to} R ⁵ are each independently a hydrogen atom, a fluorine atom or a hydrocarbon group optionally substituted with fluorine, and at least one of R ^{1 to} R ⁵ is a fluorine atom. or when including fluorine substituted is also substituted hydrocarbon group .R ¹ to R ⁵ fluorine atoms, .n comprising at least four or more fluorine atoms of R ¹ to R ⁵ is 0 or 1 When n = 0, it means that the aromatic ring and S are directly bonded.)
[2]
The non-aqueous electrolyte contains the compound represented by the general formula (1) at a content of 0.01% by mass or more and 2% by mass or less with respect to the total amount of the non-aqueous electrolyte. The non-aqueous electrolyte secondary battery according to [1].
[3]
The non-aqueous electrolyte secondary battery according to [1] or [2], wherein the positive electrode contains at least one of a lithium manganese composite oxide or a lithium iron phosphate compound having a spinel structure.
[4]
The non-aqueous electrolyte secondary battery according to [3], wherein the positive electrode contains a lithium iron phosphate compound.
[5]
The nonaqueous electrolysis according to any one of [1] to [4], wherein at least one of R ^{1 to} R ^{5 in} the general formula (1) is a fluorine atom or a hydrocarbon group Liquid secondary battery.
[6]
The nonaqueous electrolyte secondary battery according to any one of [1] to [6], wherein the nonaqueous solvent contains a cyclic carbonate and a chain carbonate.
[7]
The nonaqueous electrolyte secondary battery according to [6], wherein the ratio of the cyclic carbonate to the total of the cyclic carbonate and the chain carbonate is 25% by volume or more with respect to the composition of the nonaqueous solvent.
[8]
The non-aqueous electrolyte solution according to any one of [1] to [7], wherein the chain carbonate contains an asymmetric chain carbonate.
[9]
The non-aqueous electrolyte is a cyclic carbonate having a fluorine atom, a cyclic carbonate having a carbon-carbon unsaturated bond, a difluorophosphate, a fluorosulfate, a compound having an isocyanate group other than that represented by the general formula (1), It contains at least one compound selected from the group consisting of a compound having a cyano group, a cyclic sulfonic acid ester, and a dicarboxylic acid complex salt, as described in any one of [1] to [8] Non-aqueous electrolyte secondary battery.

According to the non-aqueous electrolyte solution of the present invention, it is possible to provide a non-aqueous electrolyte secondary battery that is excellent in high-load discharge characteristics and excellent in high-temperature cycle characteristics while suppressing an increase in initial impedance.

  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 non-aqueous electrolyte solution of the present invention is a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent, and contains the compound represented by the general formula (1). Hereinafter, the electrolyte, the non-aqueous solvent, and the compound represented by the general formula (1) will be described in this order.

<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. Note that lithium salt is preferably used as the electrolyte.

Specific examples of the electrolyte include, for example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li
Inorganic lithium salts such as BF 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 ), L
iN (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-perfluoropropanedisulfonylimide, lithium cyclic 1,4-perfluorobutanedisulfonylimide, LiC (CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₃ (CF ₃ ), LiBF ₃ (C ₂ F ₅ ), LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C Fluorine-containing organic lithium salts such as ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ ;
Sodium or potassium salt such as KPF ₆ , NaPF ₆ , NaBF ₄ , CF ₃ SO ₃ Na;
Etc.

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,
In particular, LiPF ₆ , LiBF ₄ or LiN (CF ₃ SO ₂ ) ₂ is preferable.

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 0
. It is preferable that it is 001 mass% or more and 20 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, inorganic lithium salts such as LiPF ₆ and LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF _{3
SO 2) 2, LiN (C} 2 F 5 SO 2) When used in combination with a fluorine-containing organic lithium salt of _2, etc., the proportion of the inorganic lithium salt in the whole electrolyte is 70 mass% or more, 99.9% or less It is preferable that 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 can be easily obtained, and if it is lower than the upper limit, it is avoided that the viscosity increases excessively. As described above, it is easy to ensure good ion conductivity and performance of the secondary battery. The concentration of the electrolyte such as a 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, still more preferably 1.5 mol / L or less. It is.

In particular, when the non-aqueous solvent of the non-aqueous electrolyte is mainly a carbonate compound such as alkylene carbonate or dialkyl carbonate, LiPF ₆ may be used alone,
Use in combination with LiBF ₄ is preferable because capacity deterioration due to continuous charging is suppressed. 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 nonaqueous solvent contained in the nonaqueous electrolytic solution of the present invention is not particularly limited as long as it contains at least one of a cyclic carbonate and a chain carbonate. Among the nonaqueous solvents listed below, It is preferable that it is 1 or more types of these.

  Examples of non-aqueous solvents include cyclic carbonates and chain carbonates, chain carboxylic acid esters and cyclic carboxylic acid esters, chain ethers and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, boron-containing organic solvents, and the like. It is done.

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

Among these, since the dielectric constant is high, the resistance of the non-aqueous electrolyte secondary battery can be reduced. Therefore, ethylene carbonate or propylene carbonate is preferable as the cyclic carbonate, and ethylene carbonate is particularly preferable.
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, and more specifically, for example, 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). -8 fluorinated ethylene carbonates are preferred.

  More specifically, as fluorinated ethylene carbonate and derivatives thereof, 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-dimethyl ester Ren carbonate, 4,5-difluoro-4,5-dimethylethylene 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. The 4,5-difluoroethylene carbonate is preferably a trans isomer rather than a cis isomer. This is because high ion conductivity is imparted to the nonaqueous electrolytic solution, and an interface protective film is suitably formed on the electrode of the secondary battery.
The fluorinated cyclic carbonate is not only a solvent but also the following <1-4. Also effective as an additive described in <Additives>. There is no clear boundary in the blending amount when fluorinated cyclic carbonate is used as a solvent and additive, and in this specification, the blending amount described as the blending amount as a non-aqueous solvent and the blending amount of the additive is followed as it is. it can.

  The kind of the chain carbonate is not particularly limited, and examples thereof include dialkyl carbonate. Among these, the alkyl group constituting the dialkyl carbonate preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms. Specifically, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, and the like are preferable dialkyl carbonates.

Among these, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable from the viewpoint of industrial availability, and ethyl methyl carbonate, methyl-n-propyl carbonate, ethyl are preferable from the viewpoint of lowering the melting point of the electrolyte due to the asymmetry. -N-propyl carbonate is preferred.
Further, chain carbonates having a fluorine atom (hereinafter sometimes abbreviated 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. Specific 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.
Examples of the fluorinated ethyl methyl carbonate include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trimethyl Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

Examples of the fluorinated diethyl carbonate include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, and ethyl- (2,2,2-trifluoro). Ethyl) carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2,2, Examples include 2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.

  The fluorinated chain carbonate is not only a non-aqueous solvent but also the following <1-4. Also effective as an additive described in <Additives>. There is no clear boundary in the blending amount when the fluorinated chain carbonate is used as the solvent and additive, and in this specification, the blending amount described as the blending amount as the non-aqueous solvent and the blending amount of the additive is used as it is. You can follow.

  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.

  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.

Further, the cyclic carboxylic acid ester is not particularly limited, and examples thereof include γ-butyrolactone, γ-valerolactone, and δ-valerolactone.
Among these, γ-butyrolactone is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

The type of the 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.

  The phosphorus-containing organic solvent is not particularly limited. For example, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris phosphate (2,2,2-trifluoroethyl), trimethyl phosphite, triethyl phosphite, phosphorous acid. Examples thereof include triphenyl, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide and the like.

  The kind of the 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, Examples include dimethylsulfone, ethylmethylsulfone, diphenylsulfone, methylphenylsulfone, dibutyldisulfide, dicyclohexyldisulfide, tetramethylthiuram 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 the non-aqueous solvents described above, chain carbonates and cyclic carbonates or chain carboxylic acid esters and cyclic carboxylic acid esters are preferable in terms of various characteristics in the non-aqueous electrolyte non-aqueous electrolyte secondary battery, 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, acetic acid More preferred are ethyl, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, and γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, , 2,2-trifluoroethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, ethyl butyrate is 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, when a cyclic carbonate is used, it is preferably used in combination with a low viscosity solvent such as a chain carbonate or a chain ester.

  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 nonaqueous solvent is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more, and the cyclic carbonates. The volume of the cyclic carbonates with respect to the total of the chain carbonates is preferably 10% by volume or more, more preferably 15% by volume or more, still more preferably 20% by volume or more, particularly preferably 25% by volume or more, and most preferably 27% by volume or more, preferably 70% by volume or less, more preferably 60% by volume or less, still more preferably 50% by volume or less, still more preferably 40% by volume or less, particularly preferably 35% by volume or less, most preferably 32% by volume or less. In batteries made using a combination of these non-aqueous solvents, the electrolyte impregnation rate and high-temperature storage characteristics (particularly the remaining capacity and high-load discharge capacity after high-temperature storage) during non-aqueous electrolyte secondary battery preparation This is preferable because the balance 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 thereof 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.

  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, particularly preferably 95: 5 to 50:50. 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 combination characteristics 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 asymmetric chain carbonates as chain carbonates are more preferable,
In particular, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate,
Alternatively, those containing propylene carbonate in addition to these are preferable because the balance between the cycle characteristics and discharge load characteristics of the secondary battery 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 non-aqueous solvents preferable in the present invention are those containing chain carboxylic acid 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 secondary battery. In this case, the chain carboxylic acid ester As the class, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and methyl butyrate are particularly preferable. The capacity 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 represented by general formula (1)>
The non-aqueous electrolyte solution of the present invention contains a compound represented by the following general formula (1) (hereinafter sometimes referred to as “specific NCO compound”) as an essential component. In the non-aqueous electrolyte solution of the present invention, one type of the specific NCO compound may be used, or two or more types may be used in any combination and ratio.

(In formula (1), R ^{1 to} R ⁵ are each independently a hydrogen atom, a fluorine atom or a hydrocarbon group optionally substituted with fluorine, and at least one of R ^{1 to} R ⁵ is a fluorine atom. or when including fluorine substituted is also substituted hydrocarbon group .R ¹ to R ⁵ fluorine atoms, .n comprising at least four or more fluorine atoms of R ¹ to R ⁵ is 0 or 1 N =
In the case of 0, it means that the aromatic ring and S are directly bonded. )

  In the present invention, by using a non-aqueous electrolyte containing a specific NCO compound, it is possible to achieve both high-load discharge characteristics and high-temperature cycle characteristics of a non-aqueous electrolyte secondary battery. 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 NCO compound of the present invention is considered to protect the negative electrode by reducing the compound itself on the charged negative electrode and forming a film-like structure with the reduction product. This film-like structure suppresses the side reaction of electrolyte decomposition 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. Improve battery charge / discharge efficiency.
Thus, from the viewpoint of improving the charge / discharge efficiency, the reduction product has a polarizable functional group capable of appropriately interacting with a metal ion such as lithium, can be deposited with an appropriate density, and is formed on the negative electrode. A compound to be immobilized is preferred. If the structure on the film is not dense or detaches from the negative electrode, the continuous decomposition reaction of the electrolyte cannot be suppressed, leading to deterioration of cycle characteristics. This impedes the rapid conduction of the metal ions, thus impairing the high load discharge characteristics.
In this respect, since the specific NCO compound of the present invention has a polarizable functional group such as a sulfonyl group or an isocyanato group, it can appropriately interact with a metal ion such as lithium. At the same time, since the aryl group in the molecular structure has a substituent, when a carbonaceous material is used as the main component of the negative electrode active material, the π-π interaction with the aromatic ring in the carbonaceous material is appropriately strong. Thus, although the reduction product is fixed on the negative electrode, it is considered that the deposit is not too dense and not too rough and is in a suitable level.

In the general formula (1), n is 0 or 1, and is preferably 0 from the viewpoint of improving output characteristics and cycle characteristics. This is because when the compound represented by the general formula (1) is decomposed, no phenol derivative is generated, and various characteristics of the non-aqueous electrolyte secondary battery are not deteriorated.
R ^{1 to} R ⁵ in the general formula (1) are each independently a hydrogen atom, a fluorine atom or a hydrocarbon group which may be fluorine-substituted, and at least one of R ^{1 to} R ⁵ is The substituent is a fluorine atom or an optionally substituted hydrocarbon group. Among R ^{1 to} R ⁵ , at least R ³ is preferably substituted from the viewpoint of the stability of the compound.

Examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an alkenyl group, and an alkynyl group. Preferably they are an alkyl group, an alkenyl group, and an alkynyl group, More preferably, it is an alkyl group.
In the case of an alkyl group, it is usually an alkyl group having 6 or less carbon atoms which may be branched, preferably 3 or less, more preferably 2 or less carbon atoms, and most preferably 1 carbon atom. Further, the total number of carbon atoms of R ^{1 to} R ⁵ is preferably 10 or less, more preferably 5 or less, still more preferably 3 or less, particularly preferably 2 or less, and most preferably the total number of carbon atoms is 1. It is.

  Specific examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-pentyl group, t -An amyl group and a hexyl group are mentioned, A methyl group, an ethyl group, n-propyl group, and i-propyl group are preferable, A methyl group and an ethyl group are more preferable, A methyl group is the most preferable. Since the steric hindrance of the substituent is suitable for the above alkyl group, side reactions can be suppressed while minimizing the inhibition of the electrode reaction.

  In the above alkyl group, part or all of hydrogen may be substituted with fluorine. In the case of an alkyl group in which some or all of the hydrogen atoms are substituted with fluorine, the alkyl group is usually an alkyl group having 4 or less carbon atoms and optionally substituted with fluorine, preferably 2 or less carbon atoms, Preferred is the case of 1 carbon.

  Specific examples of the alkyl group in which some or all of the hydrogen atoms are substituted with fluorine include monofluoromethyl group, difluoromethyl group, trifluoromethyl group, 2-fluoroethyl group, 2,2-difluoroethyl group, 2 , 2,2-trifluoroethyl group, 3,3,3-trifluoropropyl group, 4,4,4-trifluorobutyl group, monofluoromethyl group, difluoromethyl group, trifluoromethyl group, 2 -A fluoroethyl group, a 2,2-difluoroethyl group, and a 2,2,2-trifluoroethyl group are preferable, a monofluoromethyl group, a difluoromethyl group, and a trifluoromethyl group are more preferable, and a trifluoromethyl group is particularly preferable. . This is because the above steric hindrance is appropriate and production is relatively easy when the alkyl group is substituted with fluorine.

Examples of hydrocarbon groups other than alkyl groups in which some or all of hydrogen may be substituted with fluorine include cycloalkyl groups, alkenyl groups, and alkynyl groups in which some or all of hydrogen may be substituted with fluorine. Can be mentioned.
Specific examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and a cyclohexyl group is preferable. In these, some or all or all of hydrogen may be substituted with fluorine. This is because the cycloalkyl group described above is suitable for steric hindrance and is relatively easy to produce.

Specific examples of the alkenyl group include an ethenyl group, a propenyl group, a butenyl group, and a pentenyl group, and an ethenyl group is preferable. In these, some or all or all of hydrogen may be substituted with fluorine. This is because the alkenyl group described above is suitable for steric hindrance and is relatively easy to produce.
Specific examples of the alkynyl group include an ethynyl group, a propynyl group, a butynyl group, and a pentynyl group, and an ethynyl group is preferable. In these, some or all or all of hydrogen may be substituted with fluorine. This is because the above-described alkynyl group has appropriate steric hindrance and is relatively easy to produce.

R ^{1 to} R ⁵ in the general formula (1) are preferably each independently hydrogen, a fluorine atom, or a hydrocarbon group. Among these, it is preferable that R ^{1 to} R ⁵ are each independently a fluorine atom or a methyl group. This is because, since the substituent has an appropriate size, the above-described film-like structure is appropriately deposited, and side reactions can be suppressed while minimizing the resistance.

In the general formula ^(1), when containing a fluorine atom in R 1 to R ^5, it includes at least four or more fluorine atoms of R 1 to R ^5, preferably fluorine to all five of _R 1 to R ₅ Contains atoms. On the other hand, in the case of the hydrocarbon group or a fluorine-substituted hydrocarbon group in R ¹ to R ^5, preferably contains 3 or less hydrocarbon group or a fluorine-substituted hydrocarbon group of R ¹ to R ^5, and more preferably Two or less of R ^{1 to} R ⁵ contain a hydrocarbon group or a fluorine-substituted hydrocarbon group, and most preferably one of R ^{1 to} R ⁵ contains a hydrocarbon group or a fluorine-substituted hydrocarbon group. This is because the number range of the substituent is because of the size of the substituent, and the fluorine atom is extremely smaller than the hydrocarbon group or the fluorine-substituted hydrocarbon group. If it is said range, since the deposit of the above-mentioned film-like structure is not too dense, it is not too coarse, and it can adjust to a suitable grade, it is preferable.

In the general formula (1), the number of fluorine atoms contained in R ^{1 to} R ⁵ is preferably 10 or less, more preferably 8 or less, particularly preferably 6 or less, and 5 or less. Most preferably. This is because when the number of fluorine atoms contained in R ^{1 to} R ⁵ is too large, the solubility of the specific NCO compound in the non-aqueous solvent decreases.

There is no particular limitation on the molecular weight of the specific NCO compound in the present invention, and it is arbitrary as long as the effects of the present invention are not significantly impaired. Is. When the molecular weight is within the above range, the solubility in the non-aqueous electrolyte solution is excellent, and it becomes easier to achieve more effective effects.
Preferable specific examples of the specific NCO compound represented by the general formula (1) include the following. This is because the specific NCO compound is excellent in solubility in the non-aqueous electrolyte and the productivity is easily increased.

  More preferable examples include the following. This is because the steric hindrance is small and the reactivity on the electrode surface is optimal.

  Particularly preferred examples include the following compounds. This is because the denseness of the film-like deposit due to the reduction product can be adjusted to a suitable level.

  Most preferred is a specific NCO compound represented by the following structural formula (3). This is because it is easy to obtain industrially, and the manufacturing process of the non-aqueous electrolyte solution can be simplified.

There is no restriction | limiting in particular in the manufacturing method regarding the said specific NCO compound, It is possible to select and manufacture a well-known method arbitrarily.
The ratio of the specific NCO compound in the nonaqueous electrolytic solution is arbitrary as long as the effects of the present invention are not significantly impaired, but is generally 0.01% by mass or more, preferably 0.1% by mass or more, more preferably It is 0.2% by mass or more, more preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, most preferably 0.6% by mass or more, and usually 2% by mass or less, preferably 1. It is 4% by mass or less, more preferably 1.3% by mass or less, particularly preferably 1.2% by mass or less, and most preferably 1.1% by mass or less. If it is said density | concentration, since a reduction | restoration product will cover the negative electrode surface moderately and the effect | action in an electrode interface will advance more suitably, it will become possible to optimize a battery characteristic.

  When a specific NCO 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 remarkably high. In many cases, it is decreasing. Therefore, what can be detected even in a very small amount of the specific NCO compound from the non-aqueous electrolyte extracted from the battery is considered to be included in the present invention. In addition, when the specific NCO compound is actually used as a non-aqueous electrolyte solution for producing a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution disassembled and extracted again does not contain the specific NCO compound. Even in such a case, 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 NCO compound is detected from at least one constituent member of the positive electrode, the negative electrode, and the separator, the total amount is assumed to be contained in the non-aqueous electrolyte solution, and the content is determined as the content in the non-aqueous electrolyte solution. It is considered appropriate to calculate.

<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 of the secondary battery after high temperature storage. Among these, as an auxiliary agent for suppressing capacity maintenance characteristics and resistance increase after high-temperature storage, cyclic carbonate having fluorine atom, cyclic carbonate having carbon-carbon unsaturated bond, difluorophosphate, fluorosulfate, At least one compound selected from the group consisting of a compound having an isocyanate group other than that represented by the general formula (1), a compound having a cyano group, a cyclic sulfonic acid ester, and a dicarboxylic acid complex salt (hereinafter referred to as “specific additive”) It may be abbreviated as “)”. 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 NCO 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) a cyclic carbonate having a fluorine atom, (ii) a cyclic carbonate having a carbon-carbon unsaturated bond, (iii) a difluorophosphate, (iv) a fluorosulfate, (v) represented by the general formula (1) Nucleophilic species formed on the negative electrode surface by reduction of a specific NCO compound with respect to a compound having an isocyanato group other than (vi) a compound having a cyano group, (vii) a cyclic sulfonate ester, and (viii) a dicarboxylic acid complex salt The estimated reaction mechanism with Nu ⁻ is shown in the following reaction formula (1).

(In the reaction formula, Cat is a cation constituting a salt. Q ¹ is a divalent organic group containing fluorine, Q ² is a divalent organic group containing a carbon-carbon unsaturated bond, and Q ⁵ and Q ⁶ are Monovalent organic group, Q ⁷ represents a divalent organic group, Q ⁸ represents a single bond or a divalent organic group, and X represents a divalent organic group containing a complex center element.)
As shown in the above reaction formula (1), each of the specific additives contains a nucleophilic attack accepting site, and each of the indicated reactions is used as a starting reaction, and an electrode using the specific NCO compound and the specific additive as raw materials. It is presumed that a film-like structure that favorably supports the reaction is formed in concert.

Among specific additives, cyclic carbonates having fluorine atoms, difluorophosphates, fluorosulfates, compounds having isocyanate groups other than those represented by the general formula (1), compounds having cyano groups, cyclic sulfonates, dicarboxylic acids An acid complex salt is preferred, more preferably a cyclic carbonate having a fluorine atom, a difluorophosphate, a fluorosulfate, a compound having a cyano group, a cyclic sulfonic acid ester, or a dicarboxylic acid complex salt, particularly preferably a difluorophosphorus. Acid salts, fluorosulfates, and dicarboxylic acid complex salts, and most preferred are dicarboxylic acid complex salts. This is because the electrophilicity of the nucleophilic attack accepting site in the compound is preferable, and the reactivity with the nucleophilic species Nu ⁻ derived from the specific NCO compound is preferable.

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 solution 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. 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 may be arbitrary as long as the effects of the present invention are not significantly impaired, but in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more. 0% by mass or less.

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 most preferably 0.5% by mass or more. More preferably, it is 8.0 mass% or less, More preferably, it is 6.0 mass% or less, Most preferably, it is 3.0 mass% or less, Most preferably, it is 2.0 mass% or less.
In addition, the fluorinated carbonate not only includes the additive, but also <1-2. It also exhibits an effective function as a non-aqueous solvent described in Non-aqueous solvent>. There is no clear boundary in the blending amount when the fluorinated carbonate is used as the solvent and additive, and in this specification, the blending amount described as the blending amount as the non-aqueous solvent and the blending amount of the additive can be followed as it is. .

<1-4-1-2. Cyclic carbonate having a carbon-carbon unsaturated bond>
Among specific additives, cyclic carbonates having a carbon-carbon unsaturated bond (hereinafter sometimes abbreviated as “unsaturated carbonate”) include 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 may be arbitrary as long as the effects of the present invention are not significantly impaired, but in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more. 0% by mass or less.

  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.

<1-4-1-3. 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 more preferably used because it can contribute to the formation of a stable film-like structure.
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. However, in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more, 2 0.0 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, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and most preferably 0.3% by mass or more. More preferably, it is 1.5 mass% or less, More preferably, it is 1.2 mass% or less, Most preferably, it is 1.1 mass% or less.

<1-4-1-4. 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 more preferably used because it can contribute to the formation of a stable film-like structure.
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, but in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more. 0% by mass or less.

  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, most preferably 0.3% by mass or more, More preferably, it is 3.0 mass% or less, More preferably, it is 2.5 mass% or less, Most preferably, it is 2.0 mass% or less.

<1-4-1-5. Compounds having isocyanato groups other than those represented by the general formula (1)>
Among the specific additives, a compound having an isocyanate group other than that represented by the general formula (1) (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 the monoisocyanates include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1 Isocyanatooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl Examples thereof include isocyanate and fluorosulfonyl isocyanate.

Specific examples of the diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-di- Isocyanatooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,3-diisocyanatopropene, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluoro Butane, 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-difluo Hexane, 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), bicyclo [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 the 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, etc. Is mentioned.

  Among these, 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 available This is preferable because the manufacturing cost of the non-aqueous electrolyte solution of the present invention can be kept low. Moreover, since it can contribute to formation of a stable film-like structure also from a technical viewpoint, these isocyanates are used more suitably.

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, but in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more and 1.0% by mass. % Or less.
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, still more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, most preferably 0.3% by mass or more, and more preferably Is 0.8% by mass or less, more preferably 0.7% by mass or less, particularly preferably 0.6% by mass or less, and most preferably 0.5% by mass or less.

<1-4-1-6. 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 the 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-diph Oropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3′- Examples thereof include oxydipropionitrile, 3,3′-thiodipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, pentafluoropropionitrile and the like.

  Specific examples of the dinitriles include malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, 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-tetramethylsuccin Sinonitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2 - Rubonitrile, 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, - Gigi anode benzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3 '- (ethylenedioxy) dipropionate nitrile, 3,3' - (ethylene dithio) dipropionate nitrile, and the like.

Among the above, dinitriles such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, and dodecandinitrile contribute to the formation of a stable film-like structure. Therefore, it is used more suitably.
The content of nitrile is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more and 5.0% by mass. % Or less.

  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.

<1-4-1-7. 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 and unsaturated cyclic sulfonic acid esters.

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 , 3-methyl-1,4-butane sultone, 4-methyl-1,4-butane sultone, and the like.

  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 , 4-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-but 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- 1,4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1,4-sultone, 4-methyl-3-butene-1,4-sultone, etc. It is done.

Among these, 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 is arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more, 3 0.0 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, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and most preferably 0.5% by mass or more. More preferably, it is 2.5 mass% or less, More preferably, it is 2.0 mass% or less, Especially preferably, it is 1.8 mass% or less, Most preferably, it is 1.5 mass% or less.

<1-4-1-8. 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 these, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate are readily available and stable coatings From the point which can contribute to formation of a shaped structure, it is used more suitably.

The content of the dicarboxylic acid complex salt is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by mass of the nonaqueous electrolytic solution of the present invention, preferably 0.001% by mass or more, 2 .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, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and most preferably 0.5% by mass or more. More preferably, it is 2.0 mass% or less, More preferably, it is 1.5 mass% or less, Especially preferably, it is 1.2 mass% or less, Most preferably, it is 1.0 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 and ratios. 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 the overcharge inhibitor is blended, the amount of the overcharge inhibitor is arbitrary as long as the effects of the present invention are not significantly impaired, but the total amount of non-aqueous electrolyte is preferably 0.1%. It is the range of 001 mass% or more and 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. It is preferable because the safety of the non-aqueous electrolyte secondary battery can be improved so that there is no problem even if the battery is overcharged.

<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 sulfites such as ethylene sulfite;
Chain sulfonate esters such as methyl methanesulfonate and busulfan;
Cyclic sulfones such as sulfolane and sulfolene;
Chain sulfones such as dimethyl sulfone, diphenyl sulfone, and methylphenyl sulfone;
Sulfides such as dibutyl disulfide, dicyclohexyl disulfide, tetramethylthiuram monosulfide;
Sulfur-containing compounds such as sulfonamides such as N, N-dimethylmethanesulfonamide and N, N-diethylmethanesulfonamide;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone;
Hydrocarbon compounds such as heptane, octane, cycloheptane;
Examples thereof include fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, and benzotrifluoride.

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.
Moreover, when the non-aqueous electrolyte solution of the present invention contains these auxiliaries, the content thereof is arbitrary as long as the effects of the present invention are not significantly impaired, but with respect to the entire non-aqueous electrolyte solution (100% by mass). The range is preferably 0.001% by mass or more and 10% by 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 NCO compound, and, if necessary, the above-mentioned “specific additive” and “other additives” in the above-described non-aqueous solvent. it can.
When preparing a non-aqueous electrolyte, each raw material of the non-aqueous electrolyte, that is, an electrolyte such as a lithium salt, a specific NCO compound, a non-aqueous solvent, a specific additive, other additives, etc. should be dehydrated in advance. Is preferred. 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. Further, when the object to be dehydrated is a solid such as an electrolyte, it may be heated and dried 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 includes a positive electrode capable of occluding and releasing metal ions, a negative electrode capable of occluding and releasing metal ions, a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. A non-aqueous electrolyte secondary battery comprising an aqueous electrolyte, wherein the negative electrode active material of the negative electrode is a carbonaceous material, and the non-aqueous electrolyte is the non-aqueous electrolyte of the present invention. It is a liquid secondary battery.

<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 negative electrode and the non-aqueous electrolyte. Usually, the non-aqueous electrolyte of the present invention is the same as the non-aqueous electrolyte secondary battery. A positive electrode and a negative electrode are laminated via an impregnated porous film (separator), and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

<2-2. 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 of this invention consists of a carbonaceous material demonstrated below.

<2-3-1. Carbonaceous material>
Although it does not specifically limit as a carbonaceous material used as a negative electrode active material, The thing chosen from the following (a)-(e) gives a secondary battery with a good balance of initial irreversible capacity and high current density charge / discharge characteristics. Therefore, it is preferable.
(A) Natural graphite (A) Carbonaceous material obtained by heat-treating artificial carbonaceous material and artificial graphite material at least once in the range of 400 ° C. to 3200 ° C. (C) There are at least two types of negative electrode active material layers Carbonaceous material composed of carbonaceous materials having different crystallinity and / or having an interface where the crystalline carbonaceous materials having different crystalline properties are in contact with each other. (D) Carbonaceous material in which the negative electrode active material layer has at least two different orientations And / or carbonaceous materials (a) to (d) having an interface where carbonaceous materials having different orientations are in contact with each other may be used alone or in combination of two or more. You may use together in arbitrary combinations and ratios.

Specific examples of the artificial carbonaceous material or artificial graphite material in (i) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, and those obtained by oxidizing these pitches;
Needle coke, pitch coke and carbon materials partially graphitized from these;
Thermal decomposition products of organic substances such as furnace black, acetylene black and pitch-based carbon fiber;
Carbonizable organics and their carbides; and
Carbonized solution in which carbonizable organic material is dissolved in a low molecular organic solvent such as benzene, toluene, xylene, quinoline, n-hexane;
Etc.
In addition, the carbonaceous materials (a) to (d) above are conventionally known, and their production methods are well known to those skilled in the art, and these commercial products can also be purchased. And it is desirable for the carbonaceous material as the negative electrode active material, including those specifically described above, to satisfy one or more of the following items (1) to (8) 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. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, more preferably 1.5 nm or more, and further preferably 2 nm or more.

(2) Volume-based average particle diameter The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) determined by a laser diffraction / scattering method, and is usually 1 μm or more, more preferably 3 μm or more. 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 size is within the above range, the irreversible capacity of the secondary battery does not increase excessively, and it is easy to avoid incurring loss of the initial battery capacity. Further, as described later, when a negative electrode is produced by coating, it is easy to uniformly coat the surface, which is desirable in the battery manufacturing process.

  The volume-based average particle size is measured by dispersing the carbonaceous material powder in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and using a laser diffraction / scattering method. This is performed using a particle size distribution meter (LA-700, manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.

(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 a value 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. In addition, even when a negative electrode forming material (slurry), which will be described later, is applied to the current collector and then pressed to increase the density of the negative electrode, it is difficult to reduce the load characteristics of the secondary battery. Furthermore, it is difficult to cause a decrease in efficiency and an increase in gas generation.
Further, 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 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 the negative electrode forming material to the current collector and then pressing it, it is difficult to cause a reduction in load characteristics of the secondary battery. 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 I _A of the peak P _A in the vicinity of 1580 cm ^-1, and measuring the intensity I _B of a peak P _B in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material in the present invention. Further, the half width of the peak P _A in the vicinity of 1580 cm ^-1 of the resulting Raman spectrum was measured, which is defined as the Raman half-value width of the carbonaceous material in the present invention.

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: 1100cm ^{−1 to} 1730cm ⁻¹・ Raman R value, Raman half-value analysis: Background processing ・ Smoothing processing: Simple average, convolution 5 points

(4) BET specific surface area The BET specific surface area of the carbonaceous material is preferably 0.1 m ² · g ^-1 or more as a value of the specific surface area measured using the BET method, and 0.7 m ² · g ^-1. More preferably, 1.0m ² ·
g ^-1 or more is more preferable, 1.5 m ² · g ^-1 or more is particularly preferable, and preferably 10 m
0 m ² · g ^-1 or less, more preferably 25 m ² · g ^-1 or less, more preferably 15 m ² · g ^-1 or less, 10 m ² · g ^-1 or less are especially preferred.

  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 the carbonaceous material is used as the negative electrode forming material, and lithium or the like is difficult to precipitate on the electrode surface. It is easy to avoid a decrease in battery stability. Furthermore. The reactivity with the non-aqueous electrolyte can be suppressed, gas generation is small, and a preferable secondary 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 in the present invention.

(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.
The high current density charge / discharge characteristics of the secondary battery generally improve as the circularity increases. Accordingly, 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 short-time high current density charge / discharge characteristics of the secondary battery may be lowered.

  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 obtained by the measurement is defined as the circularity of the carbonaceous material in the present invention.

  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. And is preferably 2 g · cm ^-3 or less, more preferably 1.8 g · cm ^-3 or less, 1.6 g · cm ^-3 or less are particularly preferred.

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 secondary 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 as follows. After passing the sample 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, a powder density measuring device (for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.) is used. Using this, 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 in the present invention.

(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 of the secondary battery may be deteriorated. 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, 0.47 g of a sample is filled in a molding machine having a diameter of 17 mm, and the molded body obtained by compressing with 58.8 MN · m ⁻² is placed on the same surface as 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 in the present invention.

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, streaks of the negative electrode forming material may occur during electrode plate formation, a uniform coated surface may not be obtained, and the high current density charge / discharge characteristics of the secondary battery may deteriorate. . The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

  The aspect ratio 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 in the present invention.

<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 / release metal ions, and single metals or alloys that form alloys with the metal ions, or oxides, carbides thereof, Compounds such as nitrides, silicides, sulfides and phosphides are listed. From the viewpoint of the energy density of the non-aqueous electrolyte secondary battery, lithium ions are preferably used as the metal ions. 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 an alloy with lithium is preferable, and a metal / metalloid element of group 13 or 14 of the periodic table (that is, carbon is excluded. It is more preferable that the material includes a material including silicon (Si), tin (Sn), or lead (Pb) (hereinafter, these three elements may be referred to as “SSP metal elements”). It is preferable that it is the simple metal of these, the alloy containing these atoms, or the compound of those metals (SSP metal element). 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 kind of 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 kind or two 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 secondary battery can be increased.

  In addition, a compound in which these complex compounds are complexly bonded to several elements such as a simple metal, an alloy, or a nonmetallic element is also an example of a negative electrode active material having one kind of atom selected from the SSP metal elements. Can be mentioned. 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 secondary battery is formed, any one element of an SSP metal element, an alloy of two or more SSP metal elements, an SSP metal element Oxides, carbides, nitrides, and the like of silicon and / or tin are preferable, in particular, silicon and / or tin simple metals, alloys, oxides, carbides, nitrides, etc. are preferable, and silicon simple metals, alloys, oxides, carbides, etc. are the most. preferable.

In addition, although the capacity per unit mass of the secondary battery is inferior to that of using a single metal or an alloy, the following compounds containing silicon and / or tin are also preferable 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, as for the metal compound type material demonstrated above, any 1 type may be used independently and 2 or more types may be used together by arbitrary combinations and a 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 of the secondary battery 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.
As a lithium titanium composite oxide preferable as the negative electrode active material, a lithium titanium composite oxide represented by the following general formula (5) can be given.

Li _x Ti _y M _z O ₄ (5)
(In the 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. In the general formula (5), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, and 0 ≦ z ≦ 1.6, the structure at the time of doping / dedoping with lithium ions Is preferable because it is stable.)
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), 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 [7]. 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 a specific surface area value measured using the BET method. 7 m ² · g ^-1 or more is more preferable, 1.0 m ² · g ^-1 or more is more preferable, 1.5 m ² · g ^-1 or more is particularly preferable, and 200 m ² · g ^-1 or less is preferable, and 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 solution of the negative electrode active material is difficult to decrease, and an increase in output resistance of the secondary battery can be prevented. 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 secondary 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 in the present invention.

[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 tends 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 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 average 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. The average temporary particle diameter is determined by determining the 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. Then, secondary particles are formed, and the shape of the secondary particles is preferably 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, since the orientation of the spherical or oval spherical particles is less during the molding of the electrode than the axially oriented particles such as a plate shape, the expansion and shrinkage of the electrode during charging and discharging is also small. Mixing with a conductive material at the time of manufacturing 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 0.05 g · cm ^-3 or more, 0.1 g · cm ^-3 or more, and more preferably 0.2 g · cm ^-3 or more, 0.4 g · cm ^-3 or more are particularly preferred, 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, it is possible to secure a flow path for the non-aqueous electrolyte solution, and thus it is easy to prevent an increase in the output resistance of the secondary battery. Furthermore, since the space between the particles in the electrode is also appropriate, it is possible to secure a flow path for the non-aqueous electrolyte solution and to easily prevent an increase in the output resistance of the secondary battery.

The tap density of the lithium titanium composite oxide is measured as follows. After passing the sample 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, a powder density measuring device (for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.) is used. The 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 in the present invention.

[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. The high current density charge / discharge characteristics of the secondary battery 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 irradiation for a minute, the detection range is 0.6 to 4
Measured for particles in the range of 3 to 40 μm, designated as 00 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 is easily obtained, thereby preventing a reduction in short-time high current density charge / discharge characteristics of the secondary battery. be able to. 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) determined by the measurement is defined as the aspect ratio of the lithium titanium composite oxide in the present invention.

(Production method of lithium titanium composite oxide)
Although it does not restrict | limit especially as a manufacturing method of lithium titanium complex oxide in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.
For example, a method of obtaining an active material by uniformly mixing a titanium raw material such as titanium oxide and a raw material of another element and a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ as necessary, and firing at a high temperature Is mentioned.

In particular, various methods are conceivable for producing a spherical or ellipsoidal 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 in a solvent such as water, and the pH is adjusted while stirring to produce a spherical precursor. There is a method in which the active material is obtained by recovering and drying it if necessary, and then adding a Li source such as LiOH, Li ₂ CO ₃ , LiNO _{3 and the} like 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. Or an elliptical precursor, and LiOH such as LiOH, Li ₂ CO ₃ and LiNO ₃
A method of obtaining an active material by adding a source and baking at a high temperature can be mentioned.
As another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ , or 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.

  In addition, during the steps in the various methods mentioned above, elements other than Ti, such as Al, Mn, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn, and Ag may be present in the metal oxide structure containing titanium and / or in contact with the oxide containing titanium. By making these elements exist in the above-described form and contained in the negative electrode active material, the operating voltage and capacity of the secondary battery can be controlled.

<2-3-2. Structure, physical properties and preparation method of negative electrode>
For the negative electrode, the electrode forming method, and the current collector containing the active material, a known technical configuration can be adopted, and any one or a plurality of items (i) to (vi) shown below can be adopted. It is desirable to satisfy

(I) Production of negative electrode Any known method can be used for production of the negative electrode as long as the effects of the present invention are not significantly limited. For example, a negative electrode active material is added with a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to form a slurry-like negative electrode forming material, which is applied to a current collector, dried and then pressed. Thus, a negative electrode active material layer can be formed.

(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 these, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable.

(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.
If 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 of the secondary battery. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material may increase, and the capacity of the secondary battery may decrease.

(Iv) Electrode density The electrode structure when the negative electrode active material is converted 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, preferably 1 .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. If the density of the negative electrode active material present on the current collector is within the above range, the negative electrode active material particles are less likely to be destroyed, increasing the initial irreversible capacity of the secondary battery, and the current collector / negative electrode active material It becomes easy to prevent deterioration of high current density charge / discharge characteristics due to a decrease in permeability of the non-aqueous electrolyte to the vicinity of the interface. Further, the conductivity between the negative electrode active materials can be ensured, 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 mixture of a binder (binder), a thickener and the like to the negative electrode active material. The
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 copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene -Thermoplastic elastomeric polymers such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. Fluoropolymers; polymer compositions having ionic conductivity of alkali metal ions (especially lithium ions). 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 and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine. N, N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. Can be mentioned.

In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it 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 100 parts by mass of the negative electrode active material is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, further preferably 0.6 parts by mass or more, and preferably 20 parts by mass or less. 15 parts by mass or less is more preferable, 10 parts by mass or less is more preferable, and 8 parts by mass or less is particularly 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 lowered. Furthermore, the strength of the negative electrode is hardly lowered.

In particular, when the slurry as the negative electrode forming material contains a rubbery polymer typified by SBR as a main component, the ratio of the binder to 100 parts by mass of the negative electrode active material is preferably 0.1 parts by mass or more. More preferably 5 parts by mass or more, more preferably 0.6 parts by mass or more, more preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and still more preferably 2 parts by mass or less.
When the slurry contains a fluorine-based polymer typified by polyvinylidene fluoride as a main component, the ratio of the binder to 100 parts by mass of the negative electrode active material is preferably 1 part by mass or more and more preferably 2 parts by mass or more. Preferably, 3 parts by mass or more is more preferable, 15 parts by mass or less is preferable, 10 parts by mass or less is more preferable, and 8 parts by 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 100 parts by mass of the negative electrode active material is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 0.6 parts by mass or more. Moreover, the said ratio is 5 mass parts or less normally, 3 mass parts or less are preferable, and 2 mass parts or less are more preferable. When the ratio of the thickener to the negative electrode active material is within the above range, the coating property of the slurry becomes 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. In addition, from the viewpoint of suppressing cycle life when recharging and discharging secondary batteries and deterioration due to high temperature storage, it is possible to increase the proportion of electrodes that work more uniformly and effectively, and to improve the characteristics, as close as possible to the area equal to the positive electrode. Since it improves, it is preferable. In particular, when the secondary battery is 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 not particularly limited as long as it can electrochemically occlude and release metal ions. For example, a material that can electrochemically occlude and release lithium ions is preferable. Substances containing lithium and at least one transition metal are preferred. Specific examples include lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, lithium-containing transition metal silicate compounds, and lithium-containing transition metal borate compounds.

As the transition metal of the lithium transition metal composite oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable. As a specific example of the composite oxide, lithium-cobalt composite oxide such as LiCoO ₂ is used. , Lithium nickel composite oxides such as LiNiO ₂ , lithium manganese composite oxides such as LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO ₄ , and part of transition metal atoms that are the main components of these lithium transition metal composite oxides And other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. It is done.

As specific examples of the substituted ones, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 C
o _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.9 Al _0.1 O ₄ , L
Examples include iMn _1.8 Al _0.2 O ₄ and LiMn _1.5 Ni _0.5 O ₄ .
Among these, a composite oxide containing lithium and manganese is more preferable. 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. It is desirable to use manganese as the main transition metal. That is, among the above specific examples, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.9 Al _0.1 O ₄ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _4, etc. Can be mentioned as a more preferred specific example.

Among these, lithium manganese composite oxide having a spinel structure is most preferable. This is because the lithium manganese composite oxide has the most stable structure, hardly releases oxygen even when the non-aqueous electrolyte secondary battery is abnormal, and is excellent in safety. That is, among the above specific examples, LiMn ₂ O ₄ , LiMn _1.8 Al _0.2 O ₄ , Li _1.1 Mn _1.9 Al _0.1 O ₄ , LiMn _1.5 Ni _0.5 O _4, etc. Can be mentioned as a particularly preferred specific example.
As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, F
e, Co, Ni, Cu and the like are preferable. Specific examples of the phosphoric acid compound include iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ and LiFeP ₂ O ₇ , and phosphoric acid such as LiCoPO _4. Cobalt, 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.

As the transition metal of the lithium-containing transition metal silicate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples of the silicate compound include Li ₂ FeSiO _{4 and the} like. Iron silicates, cobalt silicates such as Li ₂ CoSiO ₄ , some of the transition metal atoms that are the main components of these lithium transition metal silicate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Examples include those substituted with other metals such as Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W.

As the transition metal of the lithium-containing transition metal borate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable. Specific examples of the borate compound include boron such as LiFeBO _3. Iron oxides, cobalt borates such as LiCoBO ₃ , and some of transition metal atoms that are the main components of these lithium transition metal borate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Examples include those substituted with other metals such as Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W.

  Among lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, lithium-containing transition metal silicate compounds, and lithium-containing transition metal borate compounds, lithium transition metal composite oxides or lithium-containing transition metal phosphate compounds are preferred. . This is because the manufacturing is relatively easy. Particularly preferred from the viewpoint of battery performance is a lithium transition metal composite oxide. This is because the voltage of the nonaqueous electrolyte secondary battery can be increased because the potential for insertion and extraction of lithium is sufficiently noble. On the other hand, lithium-containing transition metal phosphate compounds are particularly preferred from the standpoint of technology sustainability. As described above, iron is an abundant resource, a very inexpensive metal, and is less harmful.

(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) is attached to the surface of the positive electrode active material. It can also be used as a positive electrode active material. Examples of the 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. And 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, or a surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material. 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, with respect to the total mass of the positive electrode active material and the mass of the surface adhering substance. The above is more preferable. 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. Further, when the adhesion amount is within the above range, the effect can be sufficiently exhibited, and the resistance of the secondary battery is hardly increased without inhibiting the entry / exit of lithium ions.

(3) Shape The shape of the positive electrode active material particles can be a lump shape, polyhedron shape, spherical shape, elliptical spherical shape, plate shape, needle shape, columnar shape, or the like as used conventionally. Further, the primary particles may aggregate 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 positive electrode active material 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 the binder is also appropriate. For this reason, the filling rate of the positive electrode active material into the positive electrode active material layer is not restricted, and the influence on the battery capacity is reduced.

The tap density of the positive electrode active material is measured as follows. After passing the sample through a sieve with an opening of 300 μm and dropping the sample into a 20 cm ³ tapping cell to fill the cell volume, the stroke is measured using a powder density measuring instrument (eg, tap denser manufactured by Seishin Enterprise Co., Ltd.). Tapping with a 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 is difficult to obtain a high bulk density product, and further, it does not take time to diffuse lithium in the particles, so that the battery characteristics are hardly deteriorated. In addition, when producing a positive electrode for a secondary battery, 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 0.1% by weight sodium hexametaphosphate aqueous solution as a dispersion medium, and a particle size distribution meter (for example, LA-920 manufactured by Horiba, Ltd.) is used for the dispersion of the positive electrode active material. Then, 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 the average value is taken. Desired.

(7) BET specific surface area The BET specific surface area of the positive electrode active material is preferably 0.2 m ² · g ^-1 or more, preferably 0.3 m ² · g ^{-1 in} terms of the specific surface area measured using the BET method. More preferably, 0.4 m ² · g ^-1
Or more, and also preferably not more than 4.0m ² · g ^-1, 2.5m more preferably ² · g ^-1 or less, more preferably 1.5 m ² · g ^-1 or less. 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 when forming the positive electrode active material layer is improved.

  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. The specific surface area 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 _A method of obtaining an active material by adding a Li source such as ₃ and baking at a high temperature can be mentioned.

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 then fired 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 and oxides, Li sources such as LiOH, Li ₂ CO ₃ and LiNO ₃ , and other elements as required. The raw material is dissolved or pulverized and dispersed in a solvent such as water, and is then dried by a spray dryer or the like to form 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, but 2 or more types may be used. These active materials are preferably used in combination. Among these, the lithium manganese composite oxide is preferably used as a powder component. As described above, cobalt or nickel is an expensive metal with a small amount of resources, and is not preferable in terms of cost because the amount of active material used is large in large batteries that require a high capacity such as automotive applications. Therefore, it is desirable to use manganese as a main component as a cheaper transition metal.

  In particular, it is preferable to simultaneously contain a lithium manganese composite oxide having a spinel structure and a lithium nickel composite oxide having a layered structure. Combination of lithium manganese composite oxide with spinel structure with the highest safety among lithium manganese composite oxide and lithium nickel composite oxide with layered structure with the highest energy density among lithium transition metal composite oxides This is because both safety and energy density can be achieved.

(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 producing a positive electrode by a coating method, the binder 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 thereof include polyethylene, polypropylene, polyethylene terephthalate, and polymethyl. Resin polymers such as methacrylate, aromatic polyamide, cellulose, nitrocellulose; rubbers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber Polymer: Styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene /
Diene terpolymers, thermoplastic elastomeric polymers such as styrene / ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2- Soft resinous polymers such as polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetra Fluoropolymers such as fluoroethylene / ethylene copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. 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 the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; acetone, methyl ethyl ketone, and cyclohexanone. Ketones; 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 dimethyl Examples include amides such as formamide and 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 form 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 using a thickener, the ratio of the thickener to the total mass of the positive electrode active material and the thickener is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, 0.6 mass% or more is still more preferable, Preferably it is 5 mass% or less, 3 mass% or less is more preferable, and 2 mass% or less is still more preferable. When the content is within the above range, the coating property of the slurry becomes good, and further, the ratio of the active material in the positive electrode active material layer becomes sufficient. It becomes easy to avoid the problem that the resistance increases.

(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, charging / discharging at a high current density of the secondary battery, in particular, does not decrease the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface. Good characteristics. 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 is unlikely to generate heat due to Joule heat during high current density charge / discharge of the secondary battery. 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, 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 is designed so that the discharge capacity is fully charged, preferably 3 Ah (ampere hour), more preferably 4 Ah or more, preferably 20 Ah or less, more preferably 10 Ah or less.

  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 is not 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>
In the non-aqueous electrolyte secondary battery of the present invention, a separator is usually 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 the rate characteristics of the secondary battery 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 membrane resistance does not increase too much, and the rate characteristics of the secondary battery can be prevented from being lowered.
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. A thin-film separator having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is 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 porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both sides of the positive electrode and using 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 may be used. 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 a moderate gap space can be secured, the internal pressure rises as the member expands or the vapor pressure of the liquid component of the non-aqueous electrolyte increases due to the high temperature of the battery. Various characteristics such as charge / discharge repeatability and high-temperature storage characteristics can be reduced, and further, it is possible to avoid a case where the gas release valve that releases the internal pressure to the outside operates.

(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 whose resistance increases when abnormal heat or excessive current flows, temperature fuse, valve that shuts off the current flowing in the circuit due to sudden rise in battery internal pressure or internal temperature at abnormal heat generation (Current cutoff valve) and the like. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable to design a battery that does not cause abnormal heat generation or thermal runaway without a 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, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily.
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, an aluminum or aluminum alloy metal 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.
In addition, the compound used as a structural component of a non-aqueous electrolyte solution in an Example and a comparative example is the following compounds.

<< Examples 1-1 to 1-4, Comparative Examples 1-1 to 1-3 >>
[Preparation of non-aqueous electrolyte secondary battery]
<Preparation of non-aqueous electrolyte solution>
[Example 1-1]
Under a dry argon atmosphere, a sufficiently dried LiPF ₆ was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte), and The compound (a) shown in Table 1 was dissolved in an amount of 0.34% 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.

[Example 1-2]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the concentration of the compound (a) was 0.68% by mass, and the following evaluation was performed.
[Example 1-3]
The compound (a) was not dissolved in the non-aqueous electrolyte solution, but the compound (b) shown in Table 1 was dissolved in 0.50% by mass (as a concentration in the non-aqueous electrolyte solution) in the non-aqueous electrolyte solution. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1, and the following evaluation was performed.

[Example 1-4]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-3 except that the concentration of the compound (b) was 1.00% by mass, 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 the compound (a) was not dissolved in the non-aqueous electrolyte, and the following evaluation was performed.

[Comparative Example 1-2]
The compound (a) is not dissolved in the nonaqueous electrolytic solution, but the compound (c) shown in Table 1 is dissolved in the nonaqueous electrolytic solution at a concentration of 0.32% by mass (as the concentration in the nonaqueous electrolytic solution). A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1-1, and the following evaluation was performed.
[Comparative Example 1-3]
A non-aqueous electrolyte secondary battery was produced in the same manner as Comparative Example 1-2 except that the concentration of the compound (c) was 0.64% by mass, and the following evaluation was performed.

<Preparation of positive electrode>
72 parts by mass of aluminum-substituted 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 _1.15 as the second positive electrode active material)
18 parts by mass of Ni _0.45 Mn _0.45 Co _0.10 O ₂ ), 5 parts by mass of carbon black as a conductive material, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder, in N-methyl-2-pyrrolidone The slurry was mixed and slurried and uniformly applied to a 15 μm thick aluminum foil and dried, followed by roll pressing to obtain a positive electrode.

<Production of negative electrode>
93 parts by mass of graphite powder as an active material, 1 part by mass of carbon black as a conductive material, and 120 parts by mass of KF polymer L # 9305 (concentration of vinylidene fluoride polymer as a binder) as a binder , Mixed and slurried in N-methyl-2-pyrrolidone, the obtained slurry was uniformly applied to a copper foil having a thickness of 10 μm, 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, and after injecting the non-aqueous electrolytes of the above-described Examples and Comparative Examples, vacuum sealing was performed 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 of 25 ° C., sheet-like non-aqueous electrolyte secondary battery is 0.1 C (the rated capacity with a discharge capacity of 1 hour rate is 1 C. The current value is 1 C. The same applies hereinafter. )) To a constant current-constant voltage up to 4.2V, and then discharged to 2.7V at 0.1C. Subsequently, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.3 C, and then discharged to 2.7 V at 0.3 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. Thereafter, charge and discharge were performed at 0.3 C, and the discharge capacity was measured to obtain an initial capacity.

-High-load discharge test The high-load discharge test was conducted at 2C, which is considered to be the high load of the upper limit of actual use in electric vehicles. A battery charged with a constant current-constant voltage up to 4.2 V at 0.3 C is discharged to 2.7 V at a constant current value corresponding to 2 C, and using the discharge capacity and the initial capacity described above,
(High load capacity loss) = (2C discharge capacity)-(initial capacity)
The high load capacity loss represented by

In Table 2 below, high load capacity loss is expressed as a relative value when Comparative Example 1-1 is taken as 100%. That is, it can be said that the smaller the value of the high load capacity loss shown in Table 2, the better the capacity does not decrease even under high load conditions. As can be seen from the molecular weight shown in Table 1,
-Example 1-1, Example 1-3, and Comparative Example 1-2
-Example 1-2, Example 1-4, and Comparative Example 1-3
Are respectively compared at the same mass molar concentration.

  As is apparent from Table 2, when a non-aqueous electrolyte containing a compound that is not a specific NCO compound is used, the high load capacity loss increases, whereas the non-aqueous electrolyte contains the specific NCO compound. It has been shown that the use of this non-aqueous electrolyte solution can provide a non-aqueous secondary battery having a high load capacity loss that is less than that of using a non-aqueous electrolyte solution that does not contain a compound and excellent in high-load discharge characteristics.

<< Examples 2-1 to 2-6, Comparative Examples 2-1 to 2-5 >>
[Preparation of non-aqueous electrolyte secondary battery]
<Preparation of non-aqueous electrolyte solution>
[Example 2-1]
Under a dry argon atmosphere, 0.9 mol / L of LiPF ₆ sufficiently dried in a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate (volume ratio 3: 6: 1, hereinafter referred to as “carbonate solvent”) In addition, the compound (a) shown in Table 1 is dissolved in an amount of 1.2% by mass (as the concentration in the non-aqueous electrolyte solution), and non-aqueous electrolysis is performed. A liquid was prepared. Using this non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was produced by the following method, and the following evaluation was performed.

[Example 2-2]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that the concentration of the compound (a) was 1.3% by mass, and the following evaluation was performed.
[Example 2-3]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that the concentration of the compound (a) was 1.4% by mass, and the following evaluation was performed.

[Example 2-4]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that the concentration of the compound (a) was 1.5% by mass, and the following evaluation was performed.

[Example 2-5]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that the concentration of the compound (a) was 2.5% by mass, and the following evaluation was performed.

[Example 2-6]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that the concentration of the compound (a) was 3.0% by mass, 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 the compound (a) was not dissolved in the non-aqueous electrolyte, and the following evaluation was performed.

[Comparative Example 2-2]
Other than not dissolving the compound (a) in the non-aqueous electrolyte solution but dissolving 0.5% by mass (as a concentration in the non-aqueous electrolyte solution) of the compound (d) shown in Table 1 in the non-aqueous electrolyte solution. Produced a non-aqueous electrolyte secondary battery in the same manner as in Example 2-1, and performed the following evaluation.
[Comparative Example 2-3]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Comparative Example 2-2 except that the concentration of the compound (d) was 1.0% by mass, and the following evaluation was performed.

[Comparative Example 2-4]
Without using a carbonate solvent in the non-aqueous electrolyte, tetramethylene sulfone (hereinafter referred to as “TMS solvent”) was sufficiently dried with 0.9 mol / L of LiPF ₆ (as the concentration in the non-aqueous electrolyte). Furthermore, the compound (a) shown in Table 1 was dissolved in an amount of 1.2% by mass (as a concentration in the non-aqueous electrolyte solution) to prepare a non-aqueous electrolyte solution. A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that this non-aqueous electrolyte was used, and the following evaluation was performed.

[Comparative Example 2-5]
A non-aqueous electrolyte secondary battery was produced in the same manner as Comparative Example 2-4 except that the concentration of the compound (a) was 1.5% by mass, and the following evaluation was performed.

<Preparation of positive electrode>
67.5 parts by mass of aluminum-substituted 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 as the second positive electrode active material (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, 5 polyvinylidene fluoride (PVdF) as a binder A mass part was 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, and after injecting the non-aqueous electrolytes of the above-described Examples and Comparative Examples, vacuum sealing was performed 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. Of the number of test batteries, the ratio of the batteries that could not be charged / discharged is shown in Table 3 as the ratio of defective cells.

  Subsequently, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.3 C, and then discharged to 2.7 V at 0.3 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. Then, it charged to 4.2V at 0.3C, discharged to 2.7V, the discharge capacity was measured, and it was set as the initial stage capacity. Furthermore, the battery was charged to exactly half the initial capacity, and a 50% charged battery was obtained.

-Initial impedance measurement After implementing initial charging / discharging, about the non-aqueous electrolyte secondary battery adjusted to 50% of charge condition, alternating current impedance measurement was performed at -10 degreeC. The absolute value of the impedance at 0.01 Hz was defined as the initial impedance of the battery.
Table 3 shows the initial impedance as a relative value when the value of Comparative Example 2-1 is 100%. A smaller initial impedance is preferable because the capacity of the battery can be used without waste.

-High-temperature cycle test The high-temperature cycle test was conducted in a high-temperature environment of 55 ° C, which is regarded as the actual use upper limit temperature of the non-aqueous electrolyte secondary battery. In a constant temperature bath at 55 ° C., a constant current-constant voltage charge at 1 C to 4.2 V was performed, and a process of discharging to 2.7 V at a constant current of 1 C was regarded as 99 cycles. The capacity at the 99th cycle was defined as “cycle remaining capacity”.
Table 3 shows the cycle remaining capacity as a relative value when the initial capacity of Comparative Example 2-1 is 100%. The cycle remaining capacity is preferably a large value.

  As is apparent from Table 3, normal charge / discharge can be achieved by containing cyclic carbonate or chain carbonate as the solvent of the non-aqueous electrolyte solution. Further, by using the non-aqueous electrolyte solution of the present invention containing a specific NCO compound in the non-aqueous electrolyte solution, a non-aqueous electrolyte solution containing no compound or a non-aqueous electrolyte solution containing a compound that is not a specific NCO compound is used. Unlike the above, it is possible to provide a battery that suppresses an increase in initial impedance and has a large remaining capacity even when repeatedly charged and discharged at a high temperature.

<< Example 3-1 and Comparative Examples 3-1 to 3-3 >>
[Preparation of non-aqueous electrolyte secondary battery]
<Preparation of non-aqueous electrolyte solution>
[Example 3-1]
Under a dry argon atmosphere, a sufficiently dried LiPF ₆ was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte), and The compound (a) shown in Table 1 was dissolved in an amount of 0.7% 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 3-1]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 3-1, except that the compound (a) was not dissolved in the non-aqueous electrolyte, and the following evaluation was performed.

[Comparative Example 3-2]
The compound (a) is not dissolved in the non-aqueous electrolyte solution, and the compound (e) shown in Table 1 is dissolved in the non-aqueous electrolyte solution in an amount of 0.7% by mass (as the concentration in the non-aqueous electrolyte solution). A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 3-1, and the following evaluation was performed.
[Comparative Example 3-3]
The compound (a) is not dissolved in the non-aqueous electrolyte solution, and the compound (f) shown in Table 1 is dissolved in the non-aqueous electrolyte solution in an amount of 0.5% by mass (as the concentration in the non-aqueous electrolyte solution). Example 3 except that
A non-aqueous electrolyte secondary battery was prepared in the same manner as in -1, and the following evaluation was performed.

<Preparation of positive electrode>
67.5 parts by mass of aluminum-substituted 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 as the second positive electrode active material (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, 5 polyvinylidene fluoride (PVdF) as a binder A mass part was 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, and after injecting the non-aqueous electrolytes of the above-described Examples and Comparative Examples, vacuum sealing was performed 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 0.3 C, and then discharged to 2.7 V at 0.3 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.

-High-temperature cycle test The high-temperature cycle test was conducted in a high-temperature environment of 55 ° C, which is regarded as the actual use upper limit temperature of the non-aqueous electrolyte secondary battery. In a constant temperature bath at 55 ° C., a constant current-constant voltage charge at 1 C to 4.2 V was performed, and a process of discharging to 2.7 V at a constant current of 1 C was defined as one cycle, and 100 cycles were performed.

-Impedance measurement after durability After performing a high-temperature cycle test, the alternating current impedance measurement was performed at -10 degreeC about the non-aqueous electrolyte secondary battery adjusted to 50% of charge condition. The absolute value of the impedance at 0.01 Hz was defined as the impedance after durability of the battery.
Table 4 shows the impedance after endurance as a relative value when the value of Comparative Example 3-1 is 100%. As the post-endurance impedance is smaller, it can be used without damaging the voltage and capacity of the battery.

  As is clear from Table 4, the non-aqueous electrolyte containing a compound that is not a specific NCO compound (Comparative Example 3-2, Comparative Example 3-3) is a non-aqueous electrolyte containing no compound (Comparative Example 3-1). Rather, the impedance after endurance increases. On the other hand, the non-aqueous electrolyte solution of the present invention containing the specific NCO compound (Example 3-1) has lower endurance impedance and durability than the non-aqueous electrolyte solution containing no compound (Comparative Example 3-1). It has been shown that a non-aqueous secondary battery having excellent characteristics can be provided.

<< Examples 4-1 to 4-3, Comparative Examples 4-1 to 4-5 >>
<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>
A positive electrode described later, the negative electrode, and a polyolefin separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The battery element thus obtained was wrapped in an aluminum laminate film, and after injecting the nonaqueous electrolytes of Examples and Comparative Examples described later, vacuum sealing was performed to produce a sheet-like nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery thus obtained was evaluated as described below.

[Example 4-1]
<Preparation of positive electrode>
83.5 parts by mass of lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material, 10 parts by mass of carbon black as a conductive material, and 6.5 parts by mass of polyvinylidene fluoride (PVdF) as a binder, After mixing and slurrying in N-methyl-2-pyrrolidone, 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. (Hereinafter, the positive electrode is described as LFP)

<Preparation of non-aqueous electrolyte solution>
Subsequently, LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte) in a dry argon atmosphere. Furthermore, the compound (a) shown in Table 1 was dissolved in an amount of 0.35% by mass (as a concentration in the non-aqueous electrolyte) to prepare a non-aqueous electrolyte.

<High-temperature cycle evaluation of non-aqueous electrolyte secondary battery>
-Initial charge / discharge After charging the battery produced by the above method using this positive electrode and the non-aqueous electrolyte in a constant temperature bath at 25 ° C to 3.8V at 0.2C, at 0.3C The battery was discharged to 2.5V. Subsequently, the battery was charged at a constant current-constant voltage to 3.8 V at 0.3 C, and then discharged to 2.5 V at 0.3 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 12 hours to perform aging.
-High-temperature cycle evaluation After charging the battery after aging to a constant current-constant voltage to 3.8 V at 1 C in a constant temperature bath at 55 ° C., the process of discharging to 2.5 V at a constant current of 1 C is defined as 20 cycles. Cycled.

[Example 4-2]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 4-1, except that the concentration of the compound (a) was 0.70% by mass.

[Example 4-3]
<Preparation of positive electrode>
67.5 parts by mass of aluminum-substituted 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 as the second positive electrode active material (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, 5 polyvinylidene fluoride (PVdF) as a binder A mass part was 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. (Hereinafter, the positive electrode is described as LMO + NMC)
<Preparation of non-aqueous electrolyte solution>
Subsequently, LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte) in a dry argon atmosphere. Furthermore, the compound (a) shown in Table 1 was dissolved in an amount of 0.70% by mass (as a concentration in the non-aqueous electrolyte solution) to prepare a non-aqueous electrolyte solution.

<High-temperature cycle evaluation of non-aqueous electrolyte secondary battery>
-Initial charging / discharging The battery produced by the above method using the positive electrode and the non-aqueous electrolyte solution was charged at a constant current of 0.1 C to 4.2 V in a thermostatic bath at 25 ° C., and then 2.7 V at 0.1 C. Discharged until. Subsequently, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.3 C, and then discharged to 2.7 V at 0.3 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.
-High-temperature cycle evaluation The battery after the above aging was charged in a constant temperature-constant voltage to 4.2V at 1C in a constant temperature bath at 55 ° C, and then discharged to 2.7V at a constant current of 1C as one cycle. Cycled.

[Example 4-4]
<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. (Hereinafter, the positive electrode is described as NMC)
<Preparation of non-aqueous electrolyte solution>
Subsequently, LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte) in a dry argon atmosphere. Furthermore, the compound (a) shown in Table 1 was dissolved in an amount of 0.35% by mass (as a concentration in the non-aqueous electrolyte) to prepare a non-aqueous electrolyte.

<High-temperature cycle evaluation of non-aqueous electrolyte secondary battery>
-Initial charging / discharging After charging the secondary battery produced by the above method using the positive electrode and the non-aqueous electrolyte in a constant temperature bath at 25 C to 4.1 V in a thermostatic chamber at 25 ° C, Discharged to 3V at 3C. Subsequently, the battery was charged at a constant current-constant voltage to 4.1 V at 0.3 C, and then discharged to 3 V at 0.3 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 12 hours to perform aging.
-High-temperature cycle evaluation The battery after the above aging was charged in a constant temperature-constant voltage to 4.2V at 1C in a constant temperature bath at 55 ° C, and then discharged to 2.7V at a constant current of 1C as one cycle. Cycled.

[Example 4-5]
A non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 4-4 except that 0.70% by mass (as a concentration in the non-aqueous electrolyte) of the compound (a) was dissolved in the non-aqueous electrolyte. The following evaluation was carried out.

[Comparative Example 4-1]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 4-1, except that the compound (a) was not dissolved in the non-aqueous electrolyte.

[Comparative Example 4-2]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 4-3 except that the compound (a) was not dissolved in the non-aqueous electrolyte, and the following evaluation was performed.

[Comparative Example 4-3]
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 4-4 except that the compound (a) was not dissolved in the non-aqueous electrolyte, and the following evaluation was performed.

  Table 5 shows the ratio of the capacity at the 20th cycle to the capacity at the first cycle as a capacity retention rate. Moreover, it shows together about the improvement degree of the capacity | capacitance maintenance factor by having contained the compound (a).

  As is apparent from Table 5, high-temperature cycle characteristics are shown to be improved when a non-aqueous electrolyte solution containing a specific NCO compound is used. In particular, in a non-aqueous electrolyte secondary battery using a specific positive electrode. It has been shown that a significant improvement in properties can be seen.

<< Examples 5-1 to 5-2, Comparative Examples 5-1 to 5-5 >>
<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>
A positive electrode described later, the negative electrode, and a polyolefin separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The battery element thus obtained was wrapped in an aluminum laminate film, and after injecting nonaqueous electrolytes of Examples and Comparative Examples described later, vacuum sealing was performed to produce a sheet-like nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery thus obtained was evaluated as described below.

[Example 5-1]
<Preparation of positive electrode>
83.5 parts by mass of lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material, 10 parts by mass of carbon black as a conductive material, and 6.5 parts by mass of polyvinylidene fluoride (PVdF) as a binder, After mixing and slurrying in N-methyl-2-pyrrolidone, 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. (Hereinafter, the positive electrode is described as LFP)

<Preparation of non-aqueous electrolyte solution>
Subsequently, LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte) in a dry argon atmosphere. Furthermore, the compound (a) shown in Table 1 was dissolved in an amount of 0.35% by mass (as a concentration in the non-aqueous electrolyte) to prepare a non-aqueous electrolyte.

<High temperature resistance evaluation of non-aqueous electrolyte secondary battery>
-Initial charge / discharge After charging the battery produced by the above method using this positive electrode and the non-aqueous electrolyte in a constant temperature bath at 25 ° C to 3.8V at 0.2C, at 0.3C The battery was discharged to 2.5V. Subsequently, the battery was charged at a constant current-constant voltage to 3.8 V at 0.3 C, and then discharged to 2.5 V at 0.3 C. This was carried out for 2 cycles for a total of 3 cycles to stabilize the non-aqueous electrolyte secondary battery.
-High temperature tolerance evaluation After charging the above battery at a constant current-constant voltage to 3.8 V at 1 C in a constant temperature bath at 25 ° C, the battery was left in a constant temperature bath at 60 ° C for 12 hours.

[Example 5-2]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 5-1, except that the concentration of the compound (a) was 0.70% by mass.

[Example 5-3]
<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. (Hereinafter, the positive electrode is described as NMC)
<Preparation of non-aqueous electrolyte solution>
Subsequently, LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte) in a dry argon atmosphere. Furthermore, the compound (a) shown in Table 1 was dissolved in an amount of 0.35% by mass (as a concentration in the non-aqueous electrolyte) to prepare a non-aqueous electrolyte.

<High temperature resistance evaluation of non-aqueous electrolyte secondary battery>
-Initial charge / discharge After charging the battery produced by the above method using this positive electrode and the non-aqueous electrolyte in a constant temperature bath at 25 ° C to 4.1V at 0.2C, then at 0.3C Discharged to 3V. Subsequently, the battery was charged at a constant current-constant voltage to 4.1 V at 0.3 C, and then discharged to 3 V at 0.3 C. This was carried out for 2 cycles for a total of 3 cycles to stabilize the non-aqueous electrolyte secondary battery.
-High temperature tolerance evaluation After charging the above-mentioned battery at a constant current-constant voltage at 1 C to 4.1 V in a constant temperature bath at 25 ° C, it was left in a constant temperature bath at 60 ° C for 12 hours.

[Example 5-4]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 5-3 except that the concentration of the compound (a) was 0.70% by mass.

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

[Comparative Example 5-2]
A non-aqueous electrolyte secondary battery was prepared and evaluated in the same manner as in Example 5-3 except that the compound (a) was not dissolved in the non-aqueous electrolyte.

  Table 6 shows the difference between the OCV at 25 ° C. of the battery immediately before being left and the OCV at 25 ° C. of the battery immediately after being left, that is, the decrease in OCV at the time of leaving, with the content of the compound (a) being 0% by mass for each positive electrode type. The numerical values normalized with time (Comparative Example 5-1 and Comparative Example 5-2) as 100 are shown.

  As is clear from Table 6, in the evaluation using the non-aqueous electrolyte solution containing the specific NCO compound, the non-aqueous electrolyte secondary battery whose positive electrode is the LFP positive electrode suppresses the influence on the OCV decrease when left as it is. can do.

<< Example 6-1 and Comparative Examples 6-1 to 6-4 >>
<Preparation of positive electrode>
85 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, 10 parts by mass of carbon black as a conductive material, binder 5 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 roll-pressed. A positive electrode was obtained.

<Production of negative electrode>
(Preparation of Si-containing negative electrode)
50 g of Si fine particles having an average particle size of 0.2 μm are dispersed in 2000 g of scaly graphite having an average particle size of 35 μm, and are introduced into a hybridization system (manufactured by Nara Machinery Co., Ltd.). It was made to stay and processed, and the composite_body | complex of Si and a graphite particle was obtained. The obtained composite was mixed with coal tar pitch as an organic compound to be a carbonaceous material so that the coverage after firing was 7.5%, and kneaded and dispersed by a biaxial kneader. The obtained dispersion was introduced into a firing furnace and fired at 1000 ° C. for 3 hours in a nitrogen atmosphere. The fired product obtained was further pulverized with a hammer mill and then sieved (45 μm) to prepare a negative electrode active material. The silicon element content, average particle size (d50), tap density, and specific surface area measured by the above measurement methods were 2.0% by mass, 20 μm, 1.0 g cm ⁻³ , and 7.2 m ² g ^{−1, respectively.} Met.
An aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of carboxymethylcellulose sodium) and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber), respectively, as the above-described negative electrode active material, thickener and binder 50% by mass) and mixed with a disperser to form a slurry. This slurry was uniformly applied to one side of a 10 μm thick copper foil, dried, and then pressed to obtain a negative electrode. In addition, in the negative electrode after drying, it produced so that it might become mass ratio of negative electrode active material: Carboxymethylcellulose sodium: styrene butadiene rubber = 97.5: 1: 1.5.
Negative electrode active materials 1 to 4 having a carbonaceous material content shown in Table 7 were produced by the same method as described above. The carbonaceous material content is calculated from the mass concentration (% by mass) based on the analysis result of the Si particles with respect to the total (100% by mass) of the Si particles and the graphite particles.

(Production of graphite negative electrode)
Graphite powder, thickener, and binder as aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) and aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber of 50% by mass), respectively. And mixed with a disperser to form a slurry. This slurry was uniformly applied to one side of a 10 μm thick copper foil, dried, and then pressed to obtain a negative electrode. In addition, in the negative electrode after drying, it produced so that it might become mass ratio of negative electrode active material: Carboxymethylcellulose sodium: styrene butadiene rubber = 97.5: 1: 1.5.

<Preparation of non-aqueous electrolyte solution>
Subsequently, LiPF ₆ that was sufficiently dried was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) at a concentration of 1 mol / L (as a concentration in the non-aqueous electrolyte) in a dry argon atmosphere. Furthermore, vinylene carbonate (VC) and fluoroethylene carbonate were added in amounts of 2.0% by mass (as the concentration in the non-aqueous electrolyte solution), respectively (this is referred to as a reference electrolyte solution). The compound (a) shown in Table 1 was dissolved in an amount of 2.0% by mass (as a concentration in the nonaqueous electrolyte solution) with respect to the entire reference electrolyte solution to prepare a nonaqueous electrolyte solution.

<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 in an aluminum laminate film, and the above non-aqueous electrolyte solution was injected, followed by vacuum sealing to produce a sheet-like non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery thus obtained was evaluated as described below.

<45 ° C cycle evaluation of non-aqueous electrolyte secondary battery>
-Initial charging / discharging In a 25 degreeC thermostat, the non-aqueous electrolyte secondary battery of the lamination type cell was charged by constant current-constant voltage charge to 4.0V with the electric current equivalent to 0.05C. Then, constant current discharge was carried out to 0.05V at 0.05C. Subsequently, after constant current-constant voltage charging to 4.0 V at 0.2 C, 2 at 0.2 C
. The battery was discharged at a constant current to 5 V, charged at a constant current-constant voltage to 4.2 V at 0.2 C, and then discharged at a constant current to 2.5 V at 0.2 C to stabilize the non-aqueous electrolyte secondary battery. Then, after performing constant current-constant voltage charge to 4.3V at 0.2C, it was discharged at constant current to 2.5V at 0.2C.
Subsequently, the process of discharging the non-aqueous electrolyte secondary battery to a constant current-constant voltage at 0.5 C to 4.2 V in a 45 ° C. thermostatic chamber, and then discharging to 2.5 V at a constant current of 0.5 C 1 As a cycle, 10 cycles were performed, and initial conditioning was performed.
-45 ° C cycle evaluation After charging the above battery in a 45 ° C constant temperature bath to a constant current-constant voltage at 0.5C to 4.2V, the process of discharging to 2.5V at a constant current of 0.5C is one cycle. As a result, 50 cycles were carried out.

  The ratio of the capacity at the 50th cycle to the capacity at the first cycle is shown as a capacity maintenance rate.

  As is apparent from Table 8, in the secondary battery in which the Si content in the negative electrode is a predetermined amount, the high temperature cycle capacity maintenance rate can be kept high by using a non-aqueous electrolyte solution containing a specific NCO compound. It becomes possible.

  According to the non-aqueous electrolyte solution of the present invention, it is possible to provide a battery having characteristics such as low impedance and low capacity reduction even when repeatedly charged and discharged at high temperatures. It can be suitably used in all fields such as electronic devices in which secondary batteries are 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 (9)

A non-aqueous electrolyte solution comprising: a positive electrode capable of inserting and extracting metal ions; a negative electrode capable of storing and releasing metal ions; and a non-aqueous electrolyte solution including a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. A secondary battery,
The negative electrode active material of the negative electrode is a carbonaceous material,
The non-aqueous electrolyte contains at least one of a cyclic carbonate and a chain carbonate,
Furthermore, the compound represented by following General formula (1) is contained, The non-aqueous electrolyte solution secondary battery characterized by the above-mentioned.

(In formula (1), R ^{1 to} R ⁵ are each independently a hydrogen atom, a fluorine atom or a hydrocarbon group optionally substituted with fluorine, and at least one of R ^{1 to} R ⁵ is a fluorine atom. or when including fluorine substituted is also substituted hydrocarbon group .R ¹ to R ⁵ fluorine atoms, .n comprising at least four or more fluorine atoms of R ¹ to R ⁵ is 0 or 1 When n = 0, it means that the aromatic ring and S are directly bonded.)   The non-aqueous electrolyte contains the compound represented by the general formula (1) at a content of 0.01% by mass or more and 2% by mass or less with respect to the total amount of the non-aqueous electrolyte. The non-aqueous electrolyte secondary battery according to claim 1.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode contains at least one of a lithium manganese composite oxide or a lithium iron phosphate compound having a spinel structure.   The non-aqueous electrolyte secondary battery according to claim 3, wherein the positive electrode contains a lithium iron phosphate compound. 5. The non-aqueous electrolyte secondary solution according to claim 1, wherein at least one of R ^{1 to} R ^{5 in} the general formula (1) is a fluorine atom or an alkyl group. battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous solvent contains a cyclic carbonate and a chain carbonate.   The nonaqueous electrolyte secondary battery according to claim 6, wherein the ratio of the cyclic carbonate to the total of the cyclic carbonate and the chain carbonate is 25% by volume or more with respect to the composition of the nonaqueous solvent.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the chain carbonate contains an asymmetric chain carbonate. The non-aqueous electrolyte in the previous period is a cyclic carbonate having a fluorine atom, a cyclic carbonate having a carbon-carbon unsaturated bond, a difluorophosphate, a fluorosulfate, a compound having an isocyanate group other than that represented by the general formula (1), The non-aqueous system according to claim 1, comprising at least one compound selected from the group consisting of a compound having a cyano group, a cyclic sulfonic acid ester, and a dicarboxylic acid complex salt. Electrolyte secondary battery.