JP2012094454A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte exhibiting excellent rate characteristics after high temperature storage, and to provide a lithium ion secondary battery using the nonaqueous electrolyte.SOLUTION: The nonaqueous electrolyte containing a nonaqueous solvent and an electrolyte dissolved into the nonaqueous solvent, further contains at least one kind of lithium salt selected from a group consisting of a difluorophosphoric acid lithium salt, a bis(fluorosulfonyl) amide lithium salt and a fluorosulfonic acid lithium salt, and a cyclic disulfonic acid ester.

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 non-aqueous solvents as electrolytes can achieve high energy density, so they can be used in a wide range of applications, from small power supplies such as mobile phones and laptop computers to large power supplies for automobiles and load leveling. Has been applied. However, in recent years, the demand for higher performance for non-aqueous electrolyte batteries is increasing, and there is a strong demand for improvement in characteristics.

Lithium non-aqueous electrolyte secondary batteries include cyclic carbonates such as ethylene carbonate and propylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; cyclic carboxylic acids such as γ-butyrolactone and γ-valerolactone Esters, chain carboxylic acid esters such as methyl acetate, ethyl acetate, and methyl propionate, and solutes such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ A nonaqueous electrolytic solution containing is used.

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

  In Patent Document 1, a nonaqueous electrolytic solution containing a cyclic disulfonic acid ester is used, and this additive is reacted in a nonaqueous electrolytic secondary battery to form a film at the electrode interface. A technique for suppressing decomposition is disclosed. In particular, when an oxide containing manganese is used for the positive electrode, it is possible to suppress the elution of manganese and prevent the eluted manganese from adhering to the negative electrode. It is said that cycle characteristics can be improved and resistance increase due to high temperature storage can be suppressed.

Non-Patent Documents 1 to 3 report that a cycloresone, which is a cyclic disulfonic acid ester, is added to an electrolytic solution to form a low-resistance SEI film, storage characteristics are improved, and cycle characteristics are improved.
Patent Document 2 discloses a technique for improving the capacity retention rate after a storage test by suppressing the decomposition of a non-aqueous electrolyte by using an electrolyte containing lithium difluorophosphate.

Patent Document 3 discloses a technique using a bis (fluorosulfonyl) amidolithium salt as an additive for improving output performance.
Patent Document 4 reports that the use of lithium fluorosulfonate as an electrolyte suppresses the decomposition reaction of the electrolytic solution and improves cycle characteristics.

JP 2004-281368 A Japanese Patent Laid-Open No. 11-67270 JP 2009-129797 A JP-A-7-296849

44th Battery Symposium Abstracts p. 526 Abstracts of the 45th Battery Symposium p. 392 Summary of 2005 Electrochemical Fall Conference p. 73

  However, demands for improving the characteristics of lithium non-aqueous electrolyte secondary batteries in recent years are increasing, and it is required to have all the performances such as energy density, output performance, lifetime, and high-temperature storage resistance at a high level. However, it has not been achieved yet, and in particular, there has been a problem that rate characteristics after high-temperature storage deteriorate.

The present invention has been made in view of the above-described problems. That is, it aims at improving the lifetime of a lithium non-aqueous electrolyte secondary battery, and improving the rate characteristic after high temperature storage.
As a result of intensive studies, the inventors of the present invention have found that the above-mentioned problems can be solved by including a specific compound in the electrolytic solution, and have completed the present invention.
The gist of the present invention is as follows.

In a non-aqueous electrolyte solution comprising a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent, at least one selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium fluorosulfonate A non-aqueous electrolyte containing a lithium salt and a disulfonic acid ester.
The disulfonic acid ester is preferably a cyclic disulfonic acid ester represented by the following general formula (1).

(However, in the above general formula _(1), R 1, _{R 2} is a hydrocarbon group of each branched carbon atoms and optionally 1 to 10.)
More preferably, the cyclic disulfonate represented by the general formula (1) is at least one cyclic disulfonate selected from methylenemethane disulfonate, dimethylenemethane disulfonate, and trimethylenemethane disulfonate.

Moreover, it is preferable to contain 0.01 mass% or more and 5 mass% or less of cyclic disulfonic acid ester shown by the said General formula (1) in nonaqueous electrolyte solution.
In addition, at least one lithium salt selected from the group consisting of the above-mentioned lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium lithium fluorosulfonate is contained in a non-aqueous electrolyte solution in an amount of 0.01 to 5 mass percent. It is preferable to contain.

  Another gist of the present invention is a non-aqueous electrolyte secondary battery comprising at least a positive electrode capable of inserting and extracting lithium ions, a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution. A nonaqueous electrolyte secondary battery is characterized in that the aqueous electrolyte is the above nonaqueous electrolyte.

  According to the present invention, even when stored at a high temperature, the overvoltage at the time of large current discharge is small and a characteristic capable of obtaining a large discharge capacity, that is, a favorable rate characteristic after storage at a high temperature can be maintained.

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. It contains at least one lithium salt selected from the group consisting of and a cyclic disulfonic acid ester.

<Action>
A non-aqueous electrolyte containing at least one lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium lithium fluorosulfonate in the present invention and a cyclic disulfonic acid ester at the same time The use and the principle that the non-aqueous electrolyte secondary battery exhibits high rate characteristics after high-temperature storage are not clear, but are considered as follows. However, the present invention is not limited to the following actions and principles.

  That is, it contains only at least one lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium fluorosulfonate as in Comparative Examples 3, 4, and 5 described later. However, a certain amount of high temperature storage rate characteristics can be obtained, but as shown in Comparative Example 2, when used alone, a rate after high temperature storage is surprisingly increased by using together with a cyclic disulfonic acid ester that deteriorates the high temperature storage rate characteristics. As one of the factors that further improve the characteristics, the cyclic disulfonic acid ester assists the effect of a lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium fluorosulfonate. It is thought that. Specifically, lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt, lithium fluorosulfonate, and cyclic disulfonate that improve high-temperature storage characteristics through interaction with the electrode act on the electrode in combination. Thus, it is considered that the surface state of the electrode active material is made more suitable for obtaining battery characteristics and maintained.

<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. In addition, when using the non-aqueous electrolyte of this invention for a non-aqueous electrolyte secondary battery, it is preferable to use lithium salt as electrolyte.
As a specific example of the electrolyte, for example,
Inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li ₂ CO ₃ , LiBF ₄ ;
LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), lithium cyclic 1,2-ethanedisulfonyl Imide, lithium cyclic 1,3-propanedisulfonylimide, lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, lithium cyclic 1,4-perfluorobutane disulfonyl Imide, 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 2 _{5) 2, LiBF 2 (CF} 3 SO 2) 2, LiBF 2 (C 2 F 5 fluorine-containing organic lithium salt of _{SO 2) 2} and the like;
Dicarboxylic acid complex lithium salts such as lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluoro (bisoxalato) phosphate, lithium tetrafluoro (oxalato) phosphate;
Sodium salts or potassium salts 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 (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium bis (Oxalato) borate is preferred, and LiPF ₆ or LiBF ₄ is particularly preferred.
One type of electrolyte may be used alone, or two or more types of electrolytes may be used in any combination and 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, LiCF 3} SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) _2, etc. The combined use with a fluorine-containing organic lithium salt is preferred.
When LiPF ₆ and LiBF ₄ are used in combination, the proportion of LiBF _{4 in} the entire electrolyte is preferably 0.01% by mass or more and 20% by mass or less. Within this range, the resistance of the non-aqueous electrolyte can be suppressed from increasing due to the low degree of dissociation of LiBF ₄ .

On the other hand, when an inorganic lithium salt such as LiPF ₆ or LiBF ₄ and a fluorine-containing organic lithium salt such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , or LiN (C ₂ F ₅ SO ₂ ) ₂ are used in combination The proportion of the inorganic lithium salt in the entire electrolyte is preferably 70% by mass or more and 99% by mass or less. Within this range, the ratio of the fluorine-containing organic lithium salt having a large molecular weight is generally too high compared to the inorganic lithium salt, and the ratio of the non-aqueous solvent in the entire non-aqueous electrolyte decreases, resulting in non-aqueous electrolysis. An increase in the resistance of the liquid can be suppressed.

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

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

<1-2. Lithium salt>
The non-aqueous electrolyte solution of the present invention contains at least one lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium fluorosulfonate as an essential component. In the non-aqueous electrolyte of the present invention, only one lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium lithium fluorosulfonate may be used. Although the above lithium salts may be used in any combination and ratio, it is preferable to use one type of lithium salt from the viewpoint of efficiently operating the non-aqueous electrolyte secondary battery. In addition, from the viewpoint of solubility in non-aqueous electrolytes, industrial availability, and suppression of overvoltage during large current discharge even after high temperature storage, and from the viewpoint of obtaining a large discharge capacity, bis (fluorosulfonyl) amide It is preferable to contain a lithium salt selected from a lithium salt and a lithium fluorosulfonic acid salt.

  The lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt, and lithium lithium fluorosulfonate in the non-aqueous electrolyte is preferably 0.01% by mass in the non-aqueous electrolyte. % Or more, more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more. Moreover, the upper limit of the content is preferably 5% by mass or less, more preferably 3% by mass or less. Rate characteristics after high-temperature storage when the concentration of a lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium fluorosulfonate in the non-aqueous electrolyte is within the above range It is easy to avoid a situation in which the improvement effect is not obtained or the charge / discharge efficiency is lowered.

  When a lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium lithium fluorosulfonate is actually used for non-aqueous electrolyte secondary battery production as its non-aqueous electrolyte, Even when the battery is disassembled and the non-aqueous electrolyte is extracted again, the content in the battery is often significantly reduced. Accordingly, a non-aqueous electrolyte extracted from a battery can detect even a small amount of at least one lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium and lithium fluorosulfonate Are considered to be included in the present invention. In addition, when the lithium salt is actually used as a non-aqueous electrolyte for the production of a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte obtained by disassembling the battery and extracting it again contains lithium difluorophosphate, bis (fluoro Even when the sulfonyl) amide lithium salt and the fluorosulfonic acid lithium salt are not contained, they are often detected on the positive electrode, the negative electrode, or the separator, which are other components of the non-aqueous electrolyte secondary battery. . Therefore, even when at least one lithium salt selected from lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt, and lithium lithium fluorosulfonate is detected from at least one constituent member of the positive electrode, the negative electrode, and the separator. It is considered to be included in the invention.

Further, a lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium lithium fluorosulfonate is contained in the non-aqueous electrolyte, and at least one constituent member of the positive electrode, the negative electrode, and the separator It is considered that it is included in this invention also when it is included in and used.
A lithium salt selected from the group consisting of a lithium difluorophosphate, a bis (fluorosulfonyl) amide lithium salt and a lithium fluorosulfonate is preliminarily placed in the positive electrode of the non-aqueous electrolyte secondary battery to be produced or on the surface of the positive electrode. It may be included. In this case, it is expected that a part or all of the lithium salt contained in advance is dissolved in the non-aqueous electrolyte and expresses its function, and that case is also considered to be included in the present invention.

  The means to be included in the positive electrode in advance or on the surface of the positive electrode is not particularly limited, but as a specific example, the lithium salt is dissolved in a slurry prepared at the time of preparing the positive electrode described later, or the positive electrode already prepared On the other hand, after applying or impregnating a solution prepared by dissolving the lithium salt in an arbitrary non-aqueous solvent in advance, the used solvent is dried and removed to contain the solution.

  In addition, when a non-aqueous electrolyte secondary battery is actually produced, it contains at least one lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide, and lithium fluorosulfonate A non-aqueous electrolyte may be included in the positive electrode or on the positive electrode surface. When producing a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution is impregnated into the positive electrode. Therefore, when a non-aqueous electrolyte solution containing a cyclic disulfonic acid ester is used, the lithium salt is contained in the positive electrode or on the positive electrode surface. It often happens. Therefore, the present invention can detect a lithium salt selected from the group consisting of at least a lithium difluorophosphate, a bis (fluorosulfonyl) amide lithium salt, and a lithium fluorosulfonate from a positive electrode recovered when the battery is disassembled. Is considered to be included.

  In addition, a lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium fluorosulfonate is present in the negative electrode or on the negative electrode surface of the nonaqueous electrolyte secondary battery to be produced. You may make it contain beforehand. In this case, a part or all of the lithium salt contained in advance is expected to be dissolved in the nonaqueous electrolytic solution and exhibit its function, and is considered to be included in the present invention. The means to be contained in the negative electrode in advance or on the surface of the negative electrode is not particularly limited, but as a specific example, the lithium salt is dissolved in a slurry prepared at the time of preparing the negative electrode, which will be described later, or an already prepared negative electrode On the other hand, after the solution prepared by dissolving the lithium salt in an arbitrary non-aqueous solvent is applied or impregnated, the solvent used is dried and removed to be contained.

  In addition, when a non-aqueous electrolyte secondary battery is actually produced, it contains at least one lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide, and lithium fluorosulfonate You may make it contain in a negative electrode or the negative electrode surface from nonaqueous electrolyte solution. When making a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte is impregnated into the negative electrode. Therefore, when a non-aqueous electrolyte containing the lithium salt is used, the lithium salt is included in the negative electrode or on the negative electrode surface. In many cases. Therefore, what can detect at least this lithium salt from the negative electrode collect | recovered when a battery is disassembled is considered to be included in the present invention.

  Furthermore, the lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt and lithium fluorosulfonate is present in the separator of the non-aqueous electrolyte secondary battery to be produced or on the surface of the separator. You may make it contain beforehand. In this case, a part or all of the lithium salt contained in advance is expected to be dissolved in the nonaqueous electrolytic solution and exhibit its function, and is considered to be included in the present invention. There is no particular limitation on the means to be contained in the separator or on the surface of the separator in advance, but as a specific example, the lithium salt is mixed at the time of making the separator, or before the non-aqueous electrolyte secondary battery is made. In this separator, after applying or impregnating a solution prepared by dissolving the lithium salt in an arbitrary nonaqueous solvent in advance, the used solvent is dried and removed to contain the separator.

  In addition, when actually producing a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte solution containing a lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium fluorosulfonate To the inside of the separator or the separator surface. When producing a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution is impregnated into the separator. Therefore, when a non-aqueous electrolyte solution containing the lithium salt is used, the lithium salt is included in the separator or on the separator surface. In many cases. Therefore, what can detect at least this lithium salt from the separator collect | recovered when a battery is disassembled is considered to be included in the present invention.

<1-3. Nonaqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte solution of the present invention is not particularly limited as long as it does not adversely affect the battery characteristics when it is used as a battery. Preferably there is.
Examples of non-aqueous solvents include linear and cyclic carbonates, linear and cyclic carboxylic acid esters, linear and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and the like.

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

Among these, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.
The kind of cyclic carbonate is not particularly limited, and examples thereof include alkylene carbonate. Among them, the number of carbon atoms of the alkylene group constituting is preferably 2 to 6, particularly preferably 2 to 4. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate (2-ethylethylene carbonate, cis and trans 2,3-dimethylethylene carbonate), and the like.

Among these, ethylene carbonate or propylene carbonate is preferable in that various characteristics of the non-aqueous electrolyte non-aqueous electrolyte secondary battery are good.
The kind of 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- Acetates such as butyl;
Propionic acid esters such as methyl propionate, ethyl propionate, propionate-n-propyl, propionate-i-propyl, propionate-n-butyl, propionate-i-butyl, propionate-t-butyl;
And butyric acid esters such as methyl butyrate and ethyl butyrate.

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.
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 kind of chain ether is not particularly limited, and examples thereof include dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, ethoxymethoxyethane, and the like.

Of these, dimethoxyethane and diethoxyethane are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.
Moreover, the kind of cyclic ether is not specifically limited, For example, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, etc. are mentioned.
Furthermore, the type of the phosphorus-containing organic solvent is not particularly limited. For example, phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, and triphenyl phosphate; trimethyl phosphite, triethyl phosphite, triphosphite Phosphites such as phenyl; phosphine oxides such as trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide; and the like.

Moreover, the kind of sulfur-containing organic solvent is not particularly limited, and examples thereof include cyclic sulfites such as ethylene sulfite; cyclic sulfonic acid esters such as 1,3-propane sultone and 1,4-butane sultone; methyl methanesulfonate; Chain sulfonic acid esters such as busulfan; cyclic sulfones such as sulfolane and sulfolen; chain sulfones such as dimethyl sulfone, diphenyl sulfone and methylphenyl sulfone; sulfides such as dibutyl disulfide, dicyclohexyl disulfide and tetramethyl thiuram monosulfide; N, Sulfonamides such as N-dimethylmethanesulfonamide and N, N-diethylmethanesulfonamide;
Etc.

  Among these, a chain and cyclic carbonate or a chain and cyclic carboxylic acid ester is preferable in terms of various characteristics in the nonaqueous electrolyte nonaqueous electrolyte secondary battery, and among these, ethylene carbonate, propylene carbonate, Dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, and γ-butyrolactone are more preferable, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, Diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl butyrate, and γ-butyrolactone are more preferred.

These nonaqueous solvents may be used alone or in combination of two or more, but two or more of them are preferably used. For example, it is preferable to use a high dielectric constant solvent of cyclic carbonates in combination with a low viscosity solvent such as chain carbonates or chain esters.
One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among these, the total of the cyclic carbonates and the chain carbonates in the entire non-aqueous solvent is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more. The volume of the cyclic carbonates with respect to the total of the saccharides and the chain carbonates is preferably 5% by volume or more, more preferably 10% by volume or more, particularly preferably 15% by volume or more, preferably 50% by volume or less, more It is preferably 35% by volume or less, particularly preferably 30% by volume or less. A battery produced using a combination of these non-aqueous solvents is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) is improved.

Examples of preferred combinations of cyclic carbonates and chain carbonates include combinations of ethylene carbonate and chain carbonates, such as ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, Examples 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 asymmetrical chain carbonates as chain carbonates are more preferable, and in particular, ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate. Those containing ethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates, such as diethyl carbonate and ethyl methyl carbonate, or further containing propylene carbonate are preferred because of a good balance between cycle characteristics and discharge load characteristics. In particular, it is preferable that the asymmetric chain carbonate is ethyl methyl carbonate, and it is preferable that the alkyl group constituting the dialkyl carbonate has 1 to 2 carbon atoms.

  Other examples of preferred non-aqueous solvents are those containing chain carboxylic esters. In particular, those containing a chain carboxylic acid ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving the discharge load characteristics of the battery. In this case, as the chain carboxylic acid esters, Are particularly preferably methyl acetate, ethyl acetate, methyl propionate, methyl butyrate and ethyl butyrate. 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.

  Examples of other preferable non-aqueous solvents include one or more organic solvents selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone. It occupies 60% by volume or more. Such a non-aqueous solvent preferably has a flash point of 50 ° C. or higher, and particularly preferably 70 ° C. or higher. By using such a non-aqueous solvent, even if the non-aqueous electrolyte secondary battery is used at a high temperature, evaporation of the solvent and liquid leakage are reduced. Among these, the total of ethylene carbonate and γ-butyrolactone in the nonaqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5:95 to 45 : 55, or the total of ethylene carbonate and propylene carbonate is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to 80:20. It is preferable to use one because it generally improves the balance between cycle characteristics and discharge load characteristics.

<1-4. Cyclic disulfonic acid ester>
In addition to the above-described at least one lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium salt, and lithium lithium fluorosulfonate, the non-aqueous electrolyte solution of the present invention is further cyclic. Contains disulfonic acid ester. In the nonaqueous electrolytic solution of the present invention, at least one lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium lithium fluorosulfonate and a cyclic disulfonic acid ester are both present. Thus, a synergistic effect is exhibited, and the discharge characteristics after high temperature storage can be greatly improved.

  The cyclic disulfonic acid ester contained in the non-aqueous electrolyte solution in the present invention is preferably one represented by the following general formula (1).

(However, in the above general formula _(1), R 1, _{R 2} is a hydrocarbon group of each branched carbon atoms and optionally 1 to 10.)
Examples of the hydrocarbon group having 1 to 10 carbon atoms in which R ₁ and R ₂ may be branched include a methylene group, a dimethylene group, a trimethylene group, a tetramethylene group, and a pentamethylene group. Of these, those selected from a methylene group, a dimethylene group and a trimethylene group are preferred. R ₁ and R ₂ may be the same or different. Moreover, as said C1-C10 hydrocarbon group which may be branched, you may contain a fluorine atom.

Further, the cyclic disulfonate represented by the general formula (1) is particularly preferably at least one cyclic disulfonate selected from methylenemethane disulfonate, dimethylenemethane disulfonate, and trimethylenemethane disulfonate.
In the non-aqueous electrolyte solution of the present invention, only one type of cyclic disulfonic acid ester may be used, or two or more types may be used in any combination and ratio.

Moreover, there is no restriction | limiting in the molecular weight of cyclic | annular disulfonic acid ester, Although it is arbitrary unless the effect of this invention is impaired remarkably, Preferably it is 300 or less, More preferably, 250 or less is practical.
Moreover, there is no restriction | limiting in particular also in the manufacturing method of cyclic disulfonic acid ester, It is possible to select and manufacture a well-known method arbitrarily.

  The ratio of the cyclic disulfonic acid ester represented by the general formula (1) in the non-aqueous electrolyte is preferably 100 ppm or more (0.01% by mass or more) in total with respect to the whole non-aqueous electrolyte. Preferably it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more. Further, the upper limit is the sum of them, preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. If the concentration of the cyclic disulfonic acid ester is too low, the action at the electrode interface does not proceed favorably. On the other hand, if the concentration is too high, the interfacial reaction may proceed excessively, leading to a decrease in battery capacity.

When cyclic disulfonic acid ester is actually used as a non-aqueous electrolyte for the production of a non-aqueous electrolyte secondary battery, the content of the cyclic disulfonic acid ester is significantly reduced even if the battery is disassembled and the non-aqueous electrolyte is extracted again. There are many cases. Accordingly, it is considered that the present invention includes those in which at least one cyclic disulfonic acid ester can be detected even in a small amount from the non-aqueous electrolyte extracted from the battery. In addition, when the cyclic disulfonic acid ester is actually used as a non-aqueous electrolyte solution for the production of a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution disassembled and extracted again contains the cyclic disulfonic acid ester. Even if not, it is often detected on the positive electrode, the negative electrode, or the separator, which is another component of the non-aqueous electrolyte secondary battery. Accordingly, the present invention also includes a case where at least one cyclic disulfonate is detected from at least one constituent member of the positive electrode, the negative electrode, and the separator.

Further, it is considered that the present invention also includes a case where the cyclic disulfonic acid ester is included in the nonaqueous electrolytic solution and is included in at least one constituent member of the positive electrode, the negative electrode, and the separator.
The cyclic disulfonic acid ester may be contained in advance in the positive electrode of the non-aqueous electrolyte secondary battery to be produced or on the surface of the positive electrode. In this case, it is expected that a part or all of the cyclic disulfonic acid ester contained in advance is dissolved in the non-aqueous electrolyte and expresses the function, and that case is also considered to be included in the present invention.

  There is no particular limitation on the means to be included in the positive electrode or on the surface of the positive electrode in advance. As a specific example, a cyclic disulfonic acid ester is dissolved in a slurry to be prepared at the time of preparing the positive electrode described later, or a positive electrode that has already been prepared. On the other hand, after applying or impregnating a solution prepared by dissolving a cyclic disulfonic acid ester in an arbitrary non-aqueous solvent in advance, the solvent used is dried and removed to contain the solution.

  Further, when a non-aqueous electrolyte secondary battery is actually produced, the non-aqueous electrolyte containing at least one cyclic disulfonate may be contained in the positive electrode or on the surface of the positive electrode. When making a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution is impregnated into the positive electrode. Therefore, when a non-aqueous electrolyte solution containing a cyclic disulfonic acid ester is used, the cyclic disulfonic acid ester is contained in the positive electrode or on the positive electrode surface. In many cases. Therefore, what can detect at least cyclic disulfonic acid ester from the positive electrode collect | recovered when a battery is disassembled is considered to be included in the present invention.

  Moreover, the cyclic disulfonic acid ester may be previously contained in the negative electrode of the nonaqueous electrolyte secondary battery to be produced or on the surface of the negative electrode. In this case, it is expected that a part or all of the cyclic disulfonic acid ester contained in advance is dissolved in the non-aqueous electrolyte and expresses the function, and is considered to be included in the present invention. There are no particular restrictions on the means for inclusion in the negative electrode or on the surface of the negative electrode in advance, but as a specific example, a cyclic disulfonic acid ester is dissolved in a slurry prepared at the time of preparing the negative electrode, which will be described later, or has already been prepared. For example, after the negative electrode is coated or impregnated with a solution prepared by dissolving a cyclic disulfonic acid ester in an arbitrary non-aqueous solvent in advance, the solvent used is dried and removed to contain the negative electrode.

  Further, when a non-aqueous electrolyte secondary battery is actually created, it may be contained in the negative electrode or on the negative electrode surface from a non-aqueous electrolyte containing at least one cyclic disulfonic acid ester. When making a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution is impregnated into the negative electrode. Therefore, when a non-aqueous electrolyte solution containing a cyclic disulfonic acid ester is used, the cyclic disulfonic acid ester is contained in the negative electrode or on the negative electrode surface. In many cases. Therefore, what can detect at least cyclic disulfonic acid ester from the negative electrode collect | recovered when a battery is disassembled is considered to be included in the present invention.

Furthermore, the cyclic disulfonic acid ester may be previously contained in the separator of the non-aqueous electrolyte secondary battery to be produced or on the surface of the separator. In this case, it is expected that a part or all of the cyclic disulfonic acid ester contained in advance is dissolved in the non-aqueous electrolyte and expresses the function, and is considered to be included in the present invention. There is no particular limitation on the means to be included in the separator or on the surface of the separator in advance. As a specific example, a cyclic disulfonic acid ester is mixed at the time of producing the separator, or a non-aqueous electrolyte secondary battery is produced. Examples include a method in which the previous separator is coated or impregnated with a solution prepared by previously dissolving a cyclic disulfonic acid ester in an arbitrary non-aqueous solvent, and then the solvent used is dried and removed.

  Further, when a non-aqueous electrolyte secondary battery is actually produced, the non-aqueous electrolyte solution containing a cyclic disulfonic acid ester may be contained in the separator or on the separator surface. When making a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte solution is impregnated in the separator. Therefore, when a non-aqueous electrolyte solution containing a cyclic disulfonic acid ester is used, the cyclic disulfonic acid ester is contained in the separator or on the surface of the separator. In many cases. Therefore, what can detect at least cyclic disulfonic acid ester from the separator collect | recovered when a battery is disassembled is considered to be included in the present invention.

<1-5. Additives>
The nonaqueous electrolytic solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. A conventionally well-known thing can be arbitrarily used for an additive. An additive may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the additive include an overcharge inhibitor and an auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage. Among these, carbonates having at least one of an unsaturated bond and a halogen atom as an aid for improving capacity retention characteristics and cycle characteristics after high-temperature storage (hereinafter sometimes abbreviated as “specific carbonate”) Is preferably added. Hereinafter, the specific carbonate and other additives will be described separately.

<1-5-1. Specific carbonate>
The specific carbonate is a carbonate having at least one of an unsaturated bond and a halogen atom. However, the specific carbonate may have only an unsaturated bond, may have only a halogen atom, and is unsaturated. It may have both a bond and a halogen atom.
The molecular weight of the specific carbonate 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 carbonate in the non-aqueous electrolyte is good, and the effect of addition can be sufficiently exhibited. The molecular weight of the specific carbonate is preferably 80 or more and 150 or less.

Moreover, there is no restriction | limiting in particular also in the manufacturing method of a specific carbonate, It is possible to select and manufacture a well-known method arbitrarily.
In addition, the specific carbonate may be included alone in the nonaqueous electrolytic solution of the present invention, or two or more may be combined in any combination and ratio.
Moreover, when using a specific carbonate, the compounding quantity of the specific carbonate of the non-aqueous electrolyte solution of the present invention is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. On the other hand, it is preferably 0.01% by mass or more and 70% by mass or less.

  When the blending amount of the specific carbonate is not less than this lower limit, a sufficient cycle characteristic improving effect can be brought about in the non-aqueous electrolyte secondary battery. In addition, if it is below this upper limit, it is possible to avoid deterioration of the high-temperature storage characteristics and continuous charge characteristics of the non-aqueous electrolyte non-aqueous electrolyte secondary battery, the amount of gas generation increases, and the capacity maintenance rate decreases. Can also be avoided. The blending amount of the specific carbonate is more preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

(1-5-1-1. Unsaturated carbonate)
Among specific carbonates, carbonates having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated carbonate”) include carbon-carbon unsaturated bonds such as carbon-carbon double bonds and carbon-carbon triple bonds. If it is the carbonate which has, it will not specifically limit, Arbitrary unsaturated carbonates can be used. In addition, the carbonate which has an aromatic ring shall also be contained in the carbonate which has an unsaturated bond.

Examples of the unsaturated carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, allyl carbonates, and the like.
Specific examples of vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, catechol carbonate, and the like.

Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include vinyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenylethylene carbonate and the like.
Specific examples of the phenyl carbonates include diphenyl carbonate, ethyl phenyl carbonate, methyl phenyl carbonate, t-butyl phenyl carbonate, and the like.

Specific examples of vinyl carbonates include divinyl carbonate and methyl vinyl carbonate.
Specific examples of allyl carbonates include diallyl carbonate, allyl methyl carbonate, and the like.
Among these, vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond are preferable, and in particular, vinylene carbonate, 4,5-diphenyl vinylene carbonate, 4,5-dimethyl vinylene carbonate. , Vinyl ethylene carbonate, ethynyl ethylene carbonate, and propargyl ethylene carbonate can form a stable interface protective film and are more preferably used.

(1-5-1-2. Halogenated carbonate)
Among the specific carbonates, a carbonate having a halogen atom (hereinafter sometimes abbreviated as “halogenated carbonate”) is not particularly limited as long as it has a halogen atom, and any halogenated carbonate is used. Can do.
Examples of the halogen atom contained in the halogenated carbonate include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among them, a fluorine atom or a chlorine atom is preferable, and a fluorine atom is particularly preferable. Further, the number of halogen atoms contained in the halogenated carbonate is not particularly limited as long as it is 1 or more, preferably 6 or less, more preferably 4 or less. When the halogenated carbonate has a plurality of halogen atoms, they may be the same as or different from each other.

Examples of halogenated carbonates include ethylene carbonate derivatives, dimethyl carbonate derivatives, ethyl methyl carbonate derivatives, diethyl carbonate derivatives and the like.
Specific examples of the ethylene carbonate derivatives include fluoroethylene carbonate, chloroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,4-dichloroethylene carbonate, 4,5-dichloroethylene carbonate, 4- Fluoro-4-methylethylene carbonate, 4-chloro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4,5-dichloro-4-methylethylene carbonate, 4-fluoro-5-methylethylene Carbonate, 4-chloro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4,4-dichloro-5-methylethylene carbonate, 4- (fluoromethyl) Ethylene carbonate, 4- (chloromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (dichloromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (trichloromethyl) -Ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (chloromethyl) -4-chloroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4- (chloromethyl)- 5-chloroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4-chloro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate, 4,5-dichloro- 4, - dimethyl carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate, 4,4-dichloro-5,5-dimethylethylene carbonate, and the like.

  Specific examples of dimethyl carbonate derivatives include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoro) methyl carbonate, chloromethyl Examples include methyl carbonate, dichloromethyl methyl carbonate, trichloromethyl methyl carbonate, bis (chloromethyl) carbonate, bis (dichloro) methyl carbonate, bis (trichloro) methyl carbonate, and the like.

  Specific examples of the ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2 -Trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, ethyl trifluoromethyl carbonate, 2-chloroethyl methyl carbonate, ethyl chloromethyl carbonate, 2,2-dichloroethyl methyl Carbonate, 2-chloroethyl chloromethyl carbonate, ethyl dichloromethyl carbonate, 2,2,2-trichloroethyl methyl carbonate , 2,2-dichloroethyl chloromethyl carbonate, 2-chloroethyl dichloromethyl carbonate, ethyl trichloromethyl carbonate, and the like.

  Specific examples of the diethyl carbonate derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2- Trifluoroethyl) carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2, 2,2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, ethyl- (2-chloroethyl) carbonate, ethyl- (2,2-dichloroethyl) ) Carbonate, bis (2-chloroethyl) carbonate, ethyl -(2,2,2-trichloroethyl) carbonate, 2,2-dichloroethyl-2'-chloroethyl carbonate, bis (2,2-dichloroethyl) carbonate, 2,2,2-trichloroethyl-2'- Examples include chloroethyl carbonate, 2,2,2-trichloroethyl-2 ′, 2′-dichloroethyl carbonate, bis (2,2,2-trichloroethyl) carbonate, and the like.

Among these halogenated carbonates, carbonates having fluorine atoms are preferable, ethylene carbonate derivatives having fluorine atoms are more preferable, and in particular, fluoroethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4,4-difluoroethylene carbonate. 4,5-difluoroethylene carbonate can form a stable interface protective film and is more preferably used.

(1-5-1-3. Halogenated unsaturated carbonate)
Furthermore, as the specific carbonate, a carbonate having both an unsaturated bond and a halogen atom (this may be abbreviated as “halogenated unsaturated carbonate” as appropriate) may be used. There is no restriction | limiting in particular as a halogenated unsaturated carbonate, As long as the effect of this invention is not impaired remarkably, arbitrary halogenated unsaturated carbonates can be used.

Examples of halogenated unsaturated carbonates include vinylene carbonate derivatives, ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, phenyl carbonate derivatives, vinyl carbonate derivatives, allyl carbonate derivatives And the like.
Specific examples of the vinylene carbonate derivatives include fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4- (trifluoromethyl) vinylene carbonate, chlorovinylene carbonate, 4- Examples include chloro-5-methyl vinylene carbonate, 4-chloro-5-phenyl vinylene carbonate, 4- (trichloromethyl) vinylene carbonate, and the like.

  Specific examples of the ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4,4 -Difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4-fluoro-4-ethynylethylene carbonate, 4-fluoro-5-ethynylethylene carbonate, 4,4-difluoro-4-ethynyl Ethylene carbonate, 4,5-difluoro-4-ethynylethylene carbonate, 4-chloro-5-vinylethylene carbonate, 4,4-dichloro-4-vinylethylene carbonate, 4,5-dichloro-4-vinylethylene carbonate, 4 -Fluoro-4,5 Divinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4-chloro-4,5-divinylethylene carbonate, 4,5-dichloro-4,5-divinylethylene carbonate, 4-fluoro-4- Phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, 4-chloro-4-phenylethylene carbonate, 4- Chloro-5-phenylethylene carbonate, 4,4-dichloro-5-phenylethylene carbonate, 4,5-dichloro-4-phenylethylene carbonate, 4,5-difluoro-4,5-diphenylethylene carbonate, 4,5- The Rollo 4,5-diphenylethylene carbonate, and the like.

  Specific examples of phenyl carbonate derivatives include fluoromethyl phenyl carbonate, 2-fluoroethyl phenyl carbonate, 2,2-difluoroethyl phenyl carbonate, 2,2,2-trifluoroethyl phenyl carbonate, chloromethyl phenyl carbonate, 2- Examples include chloroethyl phenyl carbonate, 2,2-dichloroethyl phenyl carbonate, 2,2,2-trichloroethyl phenyl carbonate, and the like.

Specific examples of vinyl carbonate derivatives include fluoromethyl vinyl carbonate, 2-fluoroethyl vinyl carbonate, 2,2-difluoroethyl vinyl carbonate, 2,2,2-trifluoroethyl vinyl carbonate, chloromethyl vinyl carbonate, 2- Examples include chloroethyl vinyl carbonate, 2,2-dichloroethyl vinyl carbonate, 2,2,2-trichloroethyl vinyl carbonate, and the like.

  Specific examples of allyl carbonate derivatives include fluoromethyl allyl carbonate, 2-fluoroethyl allyl carbonate, 2,2-difluoroethyl allyl carbonate, 2,2,2-trifluoroethyl allyl carbonate, chloromethyl allyl carbonate, 2- Examples include chloroethyl allyl carbonate, 2,2-dichloroethyl allyl carbonate, 2,2,2-trichloroethyl allyl carbonate, and the like.

Among the above-mentioned specific carbonates, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate and 4,5-difluoroethylene carbonate, or a combination of two or more of these, which are highly effective when used alone, are particularly preferable.
<1-5-2. Other additives>
Examples of additives other than the specific carbonate include overcharge inhibitors, auxiliary agents for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage, and the like.

<1-5-2-1. 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 the 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 such as

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

In addition, these overcharge inhibitors may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations. Moreover, when using together by arbitrary combinations, it may use together by the compound of the same classification illustrated above and may be used together by a compound of a different classification | category.
Specific examples of combinations in the case where compounds of different classes are used in combination include the following.

Toluene derivatives and biphenyl derivatives; Toluene derivatives and terphenyl derivatives; Partial hydrides of toluene derivatives and terphenyl derivatives; Toluene derivatives and cycloalkylbenzene derivatives; Toluene derivatives and alkylbenzene derivatives having a tertiary carbon directly bonded to the benzene ring; Toluene Alkylbenzene derivatives having a quaternary carbon directly bonded to the derivative and the benzene ring; toluene derivatives and aromatic compounds having oxygen atoms; toluene derivatives and partially fluorinated products of aromatic compounds; toluene derivatives and fluorine-containing anisole compounds;
Biphenyl derivatives and terphenyl derivatives; Partial hydrides of biphenyl derivatives and terphenyl derivatives; Biphenyl derivatives and cycloalkylbenzene derivatives; Alkylbenzene derivatives having a tertiary carbon directly bonded to the biphenyl derivative and the benzene ring; Directly to the biphenyl derivative and the benzene ring Alkylbenzene derivatives having a quaternary carbon to be bonded; biphenyl derivatives and aromatic compounds having an oxygen atom; biphenyl derivatives and partially fluorinated products of aromatic compounds; biphenyl derivatives and fluorine-containing anisole compounds;
Terphenyl derivatives and partial hydrides of terphenyl derivatives; terphenyl derivatives and cycloalkylbenzene derivatives; terphenyl derivatives and alkylbenzene derivatives having a tertiary carbon directly bonded to the benzene ring; Alkylbenzene derivatives having quaternary carbons; terphenyl derivatives and aromatic compounds having oxygen atoms; terphenyl derivatives and partially fluorinated products of aromatic compounds; terphenyl derivatives and fluorinated anisole compounds; Alkyl benzene derivatives; alkyl benzene derivatives having tertiary carbon directly bonded to the hydride of the terphenyl derivative and benzene ring; alkyl benzene derivatives having quaternary carbon directly bonded to the hydride of the terphenyl derivative and benzene ring Rubenzen derivatives; aromatic compound having a partial hydride and oxygen atoms of terphenyl derivatives; partial hydride with a fluorinated anisole compound of terphenyl derivatives; partial fluoride of part hydride and an aromatic compound of terphenyl derivatives;
A cycloalkylbenzene derivative and an alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring; a cycloalkylbenzene derivative and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring; a cycloalkylbenzene derivative and an aromatic compound having an oxygen atom; Partially fluorinated products of cycloalkylbenzene derivatives and aromatic compounds; cycloalkylbenzene derivatives and fluorine-containing anisole compounds;
An alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring and an alkylbenzene derivative having a quaternary carbon directly bonded to the benzene ring; an alkylbenzene derivative having a tertiary carbon directly bonded to the benzene ring and an aromatic having an oxygen atom Alkyl compound; alkylbenzene derivative having tertiary carbon directly bonded to benzene ring and partially fluorinated product of aromatic compound; alkylbenzene derivative having tertiary carbon directly bonded to benzene ring and fluorine-containing anisole compound; directly to benzene ring Alkyl benzene derivative having quaternary carbon to be bonded and aromatic compound having oxygen atom; Alkyl benzene derivative having quaternary carbon directly bonded to benzene ring and partially fluorinated product of aromatic compound; Fourth bonded directly to benzene ring Alkyl benzene with secondary carbon Conductor and fluorine-containing anisole compounds;
An aromatic compound having an oxygen atom and a partially fluorinated product of the aromatic compound; an aromatic compound having an oxygen atom and a fluorine-containing anisole compound;
Partially fluorinated aromatic compounds and fluorinated anisole compounds;
Specific examples of these combinations are as follows.

A combination of biphenyl and o-terphenyl, a combination of biphenyl and m-terphenyl, a combination of biphenyl and a partial hydride of a terphenyl derivative, a combination of biphenyl and cumene, a combination of biphenyl and cyclopentylbenzene, Combination of cyclohexylbenzene, combination of biphenyl and t-butylbenzene, combination of biphenyl and t-amylbenzene, combination of biphenyl and diphenyl ether, combination of biphenyl and dibenzofuran, combination of biphenyl and fluorobenzene, and biphenyl Combination of benzotrifluoride, combination of biphenyl and 2-fluorobiphenyl, combination of biphenyl and o-fluorocyclohexylbenzene, combination of biphenyl and p-fluorocyclohexylbenzene Combination of biphenyl and 2,4-difluoro anisole,
a combination of o-terphenyl and a partial hydride of a terphenyl derivative, a combination of o-terphenyl and cumene, a combination of o-terphenyl and cyclopentylbenzene, a combination of o-terphenyl and cyclohexylbenzene, o- Combination of terphenyl and t-butylbenzene, combination of o-terphenyl and t-amylbenzene, combination of o-terphenyl and diphenyl ether, combination of o-terphenyl and dibenzofuran, o-terphenyl and fluoro Combination of benzene, combination of o-terphenyl and benzotrifluoride, combination of o-terphenyl and 2-fluorobiphenyl, o-terphenyl and o
A combination of -fluorocyclohexylbenzene, a combination of o-terphenyl and p-fluorocyclohexylbenzene, a combination of o-terphenyl and 2,4-difluoroanisole,
a combination of m-terphenyl and a partial hydride of a terphenyl derivative, a combination of m-terphenyl and cumene, a combination of m-terphenyl and cyclopentylbenzene, a combination of m-terphenyl and cyclohexylbenzene, m- Combination of terphenyl and t-butylbenzene, combination of m-terphenyl and t-amylbenzene, combination of m-terphenyl and diphenyl ether, combination of m-terphenyl and dibenzofuran, m-terphenyl and fluoro Combinations of benzene, combinations of m-terphenyl and benzotrifluoride, combinations of m-terphenyl and 2-fluorobiphenyl, combinations of m-terphenyl and o-fluorocyclohexylbenzene, m-terphenyl and p -In combination with fluorocyclohexylbenzene, - combination of terphenyl and 2,4-difluoro anisole,
Combinations of terphenyl derivative partially hydride and cumene, terphenyl derivative partially hydride and cyclopentylbenzene, terphenyl derivative partially hydride and cyclohexylbenzene, terphenyl derivative partially hydride and t A combination of butylbenzene, a partial hydride of a terphenyl derivative and t-amylbenzene, a combination of a partial hydride of a terphenyl derivative and diphenyl ether, a combination of a partial hydride of a terphenyl derivative and dibenzofuran, Combination of partial hydride of phenyl derivative and fluorobenzene, combination of partial hydride of terphenyl derivative and benzotrifluoride, combination of partial hydride of terphenyl derivative and 2-fluorobiphenyl, partial hydrogen of terphenyl derivative Conversion When the combination of the o- fluoro cyclohexylbenzene, a combination of a partial hydride with p- fluoro cyclohexylbenzene terphenyl derivatives, the combination of the partial hydride and 2,4-difluoro anisole terphenyl derivatives,
A combination of cumene and cyclopentylbenzene, a combination of cumene and cyclohexylbenzene, a combination of cumene and t-butylbenzene, a combination of cumene and t-amylbenzene, a combination of cumene and diphenyl ether, a combination of cumene and dibenzofuran, A combination of cumene and fluorobenzene, a combination of cumene and benzotrifluoride, a combination of cumene and 2-fluorobiphenyl, a combination of cumene and o-fluorocyclohexylbenzene, a combination of cumene and p-fluorocyclohexylbenzene, cumene And a combination of 2,4-difluoroanisole,
Combination of cyclohexylbenzene and t-butylbenzene, combination of cyclohexylbenzene and t-amylbenzene, combination of cyclohexylbenzene and diphenyl ether, combination of cyclohexylbenzene and dibenzofuran, combination of cyclohexylbenzene and fluorobenzene, cyclohexylbenzene and Combination of benzotrifluoride, combination of cyclohexylbenzene and 2-fluorobiphenyl, combination of cyclohexylbenzene and o-fluorocyclohexylbenzene, combination of cyclohexylbenzene and p-fluorocyclohexylbenzene, cyclohexylbenzene and 2,4-difluoro Combination with anisole,
Combination of t-butylbenzene and t-amylbenzene, combination of t-butylbenzene and diphenyl ether, combination of t-butylbenzene and dibenzofuran, combination of t-butylbenzene and fluorobenzene, t-butylbenzene and benzo Combination of trifluoride, combination of t-butylbenzene and 2-fluorobiphenyl, combination of t-butylbenzene and o-fluorocyclohexylbenzene, combination of t-butylbenzene and p-fluorocyclohexylbenzene, t-butyl A combination of benzene and 2,4-difluoroanisole,
Combination of t-amylbenzene and diphenyl ether, combination of t-amylbenzene and dibenzofuran, combination of t-amylbenzene and fluorobenzene, combination of t-amylbenzene and benzotrifluoride, t-amylbenzene and 2- A combination of fluorobiphenyl, a combination of t-amylbenzene and o-fluorocyclohexylbenzene, t
A combination of amylbenzene and p-fluorocyclohexylbenzene, a combination of t-amylbenzene and 2,4-difluoroanisole,
Combination of diphenyl ether and dibenzofuran, combination of diphenyl ether and fluorobenzene, combination of diphenyl ether and benzotrifluoride, combination of diphenyl ether and 2-fluorobiphenyl, combination of diphenyl ether and o-fluorocyclohexylbenzene, diphenyl ether and p-fluoro A combination of cyclohexylbenzene, a combination of diphenyl ether and 2,4-difluoroanisole,
Combinations of dibenzofuran and fluorobenzene, combinations of dibenzofuran and benzotrifluoride, combinations of dibenzofuran and 2-fluorobiphenyl, combinations of dibenzofuran and o-fluorocyclohexylbenzene, combinations of dibenzofuran and p-fluorocyclohexylbenzene, dibenzofuran And a combination of 2,4-difluoroanisole,
Combination of fluorobenzene and benzotrifluoride, combination of fluorobenzene and 2-fluorobiphenyl, combination of fluorobenzene and o-fluorocyclohexylbenzene, combination of fluorobenzene and p-fluorocyclohexylbenzene, fluorobenzene and 2, A combination with 4-difluoroanisole,
Combination of benzotrifluoride and 2-fluorobiphenyl, combination of benzotrifluoride and o-fluorocyclohexylbenzene, combination of benzotrifluoride and p-fluorocyclohexylbenzene, combination of benzotrifluoride and 2,4-difluoroanisole combination,
A combination of 2-fluorobiphenyl and o-fluorocyclohexylbenzene, a combination of 2-fluorobiphenyl and p-fluorocyclohexylbenzene, a combination of 2-fluorobiphenyl and 2,4-difluoroanisole,
A combination of o-fluorocyclohexylbenzene and p-fluorocyclohexylbenzene, a combination of o-fluorocyclohexylbenzene and 2,4-difluoroanisole, and a combination of p-fluorocyclohexylbenzene and 2,4-difluoroanisole.

When blending the overcharge inhibitor, the amount of the overcharge inhibitor is arbitrary as long as the effects of the present invention are not significantly impaired. More preferably, it is the range of 10 mass% or less.
If the non-aqueous electrolyte of the present invention contains an overcharge inhibitor within a range that does not significantly impair the effects of the present invention, the overcharge protection circuit such as an incorrect usage or an abnormality of the charging device should operate normally. Even if the battery is overcharged due to the situation, it is preferable because the safety of the non-aqueous electrolyte secondary battery is improved.

<1-5-2-2. 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 specific carbonates such as erythritan carbonate and spiro-bis-dimethylene carbonate; cyclic sulfites such as ethylene sulfite; 1 Cyclic sulfonates such as 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone; chain sulfonates such as methyl methanesulfonate and busulfan; Cyclic sulfone; chain sulfone such as dimethyl sulfone, diphenyl sulfone, methylphenyl sulfone; sulfides such as dibutyl disulfide, dicyclohexyl disulfide, tetramethylthiuram monosulfide; N, N-dimethylmethanesulfonami , Sulfur-containing compounds such as sulfonamides such as N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl- Nitrogen-containing compounds such as 2-imidazolidinone, N-methylsuccinimide, malononitrile, succinonitrile, adiponitrile, pimeonitrile, dodecandinitrile, lauronitrile; hydrocarbon compounds such as heptane, octane, cycloheptane; fluorobenzene, And fluorine-containing aromatic compounds such as 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.
When the non-aqueous electrolyte solution of the present invention contains these auxiliaries, it is optional as long as the effects of the present invention are not significantly impaired. Preferably it is the range of 10 mass% or less.

<1-6. Specific additive>
The non-aqueous electrolyte of the present invention contains the above-described “at least one lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium fluorosulfonate” and “cyclic disulfonate ester”. In addition to the above-mentioned other additives, electrolytes, and compounds exemplified as non-aqueous solvents, etc., in particular, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, ethynyl ethylene carbonate, and difluoroethylene carbonate. At least one carbonate selected from the group, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluoro (bisoxalato) phosphate It is preferable to include one or both of at least one lithium salt selected from the group consisting of fete and at least one selected from the group consisting of lithium tetrafluoro (oxalato) phosphate. Can be improved.

  When the non-aqueous electrolyte of the present invention further contains these carbonates and / or lithium salts (hereinafter, these may be referred to as “specific additives”), the content thereof is in the whole non-aqueous electrolyte. On the other hand, the total amount thereof is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more. Further, the upper limit is the total thereof, preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. If the concentration of the specific additive in the non-aqueous solvent is too low, the reaction at the electrode interface does not proceed favorably, and for example, it may be difficult to obtain an improvement effect on the cycle characteristics. Since the interfacial reaction proceeds excessively, the battery capacity may be reduced.

<1-7. Method for producing non-aqueous electrolyte>
The non-aqueous electrolyte solution of the present invention includes at least one lithium salt selected from the group consisting of an electrolyte, a lithium difluorophosphate, a bis (fluorosulfonyl) amido lithium salt, and a lithium fluorosulfonic acid salt in the above non-aqueous solvent. And the cyclic disulfonic acid ester and, if necessary, the above-mentioned “additives” and “auxiliaries” can be dissolved.

  In preparing the non-aqueous electrolyte solution, each raw material of the non-aqueous electrolyte solution, that is, an electrolyte such as a lithium salt, a difluorophosphate lithium salt, a bis (fluorosulfonyl) amide lithium salt, and a fluorosulfonate lithium salt is selected. At least one selected lithium salt, cyclic disulfonic acid ester, non-aqueous solvent, additive, auxiliary agent and the like are preferably dehydrated in advance. The degree of dehydration is usually 50 ppm or less, preferably 30 ppm or less.

If water is present in the non-aqueous electrolyte, electrolysis of water, reaction between water and lithium metal, hydrolysis of lithium salt, and the like may occur, which is not preferable. 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 comprises a negative electrode and a positive electrode capable of inserting and extracting lithium ions and the non-aqueous electrolyte of the present invention.
<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present invention is the same as the conventionally known non-aqueous electrolyte non-aqueous electrolyte secondary battery except for the non-aqueous electrolyte, and usually the non-aqueous electrolyte of the present invention. The positive electrode and the negative electrode are laminated via a porous film (separator) impregnated with a liquid, 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 is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like.

<2-3-1. Carbonaceous material>
Although it does not specifically limit as a carbonaceous material used as a negative electrode active material, What was chosen from following (1)-(4) has good balance of initial irreversible capacity | capacitance and a high current density charge / discharge characteristic, and is preferable.
(1) Natural graphite (2) Artificial carbonaceous material and carbonaceous material obtained by heat treating artificial graphite material at least once in the range of 400 to 3200 ° C. (3) The negative electrode active material layer has at least two different crystallinities. (4) The negative electrode active material layer is composed of carbonaceous materials having at least two or more different orientations and / or has an interface where the different crystalline carbonaceous materials are in contact with each other. Or the carbonaceous material which has the interface which the carbonaceous of the different orientation has contacted (1)-(4) carbonaceous material may be used individually by 1 type, and arbitrary combinations and ratios of 2 or more types You may use together.

  Specific examples of the artificial carbonaceous material or artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch and those pitch-oxidized, needle coke, Pitch coke and carbon materials partially graphitized thereof, furnace black, acetylene black, pyrolysis products of organic substances such as pitch-based carbon fibers, carbonizable organic substances and their carbides, and carbonizable organic substances as benzene, toluene, Examples include solution-like carbides dissolved in low-molecular organic solvents such as xylene, quinoline, and n-hexane.

Specific examples of the above carbonizable organic substances include coal-based heavy oil such as coal tar pitch from soft pitch to hard pitch, dry distillation liquefied oil, etc., normal pressure residual oil, and DC heavy oil such as vacuum residual oil. , Heavy petroleum oils such as ethylene tar by-produced during thermal decomposition of crude oil, naphtha, etc., aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, phenanthrene, and nitrogen atom-containing heterocyclic compounds such as phenazine and acridine, Sulfur atom-containing heterocyclic compounds such as thiophene and bithiophene, polyphenylenes such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products of these, nitrogen-containing polyacrylonitrile, polypyrrole, etc. Organic polymer, sulfur-containing polythiophene, organic polymer such as polystyrene, cellulosic Natural polymers such as polysaccharides such as lignin, mannan, polygalacturonic acid, chitosan, saccharose, thermoplastic resins such as polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin, etc. And thermosetting resin.

<2-3-2. Configuration, physical properties, preparation method of carbonaceous negative electrode>
About the property about a carbonaceous material, the negative electrode containing a carbonaceous material, an electrode-forming method, a current collector, and a non-aqueous electrolyte secondary battery, any one of the following items (1) to (21) or It is desirable to satisfy several items 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 preferably 0. 360 nm or less, more preferably 0.350 nm or less, and still more preferably 0.345 nm or less. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, more preferably 1.5 nm or more, and still more preferably 2 nm or more.

  The graphite surface coated with amorphous carbon is preferably graphite having a d-value of 0.335 to 0.338 nm on the lattice plane (002 plane) in X-ray diffraction as a core material. A carbonaceous material having a larger d-value on the lattice plane (002 plane) in X-ray diffraction than the core material is attached, and the d-value on the lattice plane (002 plane) in X-ray diffraction is greater than that of the core material and the core material. The ratio with respect to the carbonaceous material having a large mass ratio is 99: 1 to 80:20. When this is used, a negative electrode having a high capacity and hardly reacting with the electrolytic solution can be produced.

(2) Ash content The ash content in the carbonaceous material is preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass with respect to the total mass of the carbonaceous material. % Or less, and preferably 1 ppm or more. If the mass ratio of ash exceeds the above range, deterioration of battery performance due to reaction with the non-aqueous electrolyte during charge / discharge may not be negligible. On the other hand, if it falls below the above range, the production requires a lot of time, energy and equipment for preventing contamination, which may increase the cost.

(3) Volume-based average particle diameter The volume-based average particle diameter of the carbonaceous material is usually 1 μm or more, and more preferably 3 μm or more, based on the volume-based average particle diameter (median diameter) determined by the laser diffraction / scattering method. It is more preferably 5 μm or more, particularly preferably 7 μm or more, preferably 100 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, particularly preferably 30 μm or less, and particularly preferably 25 μm or less. If the volume-based average particle size is below the above range, the irreversible capacity may increase, leading to loss of initial battery capacity. On the other hand, when the above range is exceeded, when an electrode is produced by coating, an uneven coating surface tends to be formed, which may be undesirable in the battery production process.

In order to measure the volume-based average particle size, a carbonaceous material powder is dispersed in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and laser diffraction / A scattering type particle size distribution meter (LA-700 manufactured by Horiba, Ltd.) is used. The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.
(4) Raman R value, Raman half value width The Raman R value of the carbonaceous material is preferably 0.01 or more, more preferably 0.03 or more, as measured using an argon ion laser Raman spectrum method. It is more preferably 0.1 or more, preferably 1.5 or less, more preferably 1.2 or less, still more preferably 1 or less, and particularly preferably 0.5 or less.

  When the Raman R value is less than the above range, the crystallinity of the particle surface becomes too high, and there are few sites where Li enters between layers due to charge / discharge, and charge acceptability may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

Moreover, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material is not particularly limited, but is 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and is usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.
When the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters between layers decreases with charge / discharge, and the charge acceptability may decrease. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, when the above range is exceeded, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be reduced and the gas generation may be increased.

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 PB around 1360 cm ^-1, the intensity ratio R of the _{(R =} I B / _{I A)} calculate. 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: 1100 cm ^{−1 to} 1730 cm ⁻¹
・ Raman R value, Raman half-width analysis: Background treatment ・ Smoothing treatment: Simple average, 5 points of convolution (5) BET specific surface area The BET specific surface area of carbonaceous material is the value of the specific surface area measured using the BET method but it is preferably 0.1 m ² · ^{g -1} or more, more preferably 0.7 m ² · ^{g -1} or more, more preferably 1.0 m ² · ^{g -1} or more, 1.5 m ² · ^{g -1} above are particularly preferred, also preferably at most 100 m ² · ^{g -1,} 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 is particularly preferable.

  If the value of the BET specific surface area is less than this range, the acceptability of cations such as lithium is likely to deteriorate during charging when used as a negative electrode material, and lithium and the like are likely to precipitate on the electrode surface, which may reduce stability. There is sex. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.

  The specific surface area 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.

(6) Pore size distribution The pore size distribution of the carbonaceous material is calculated by measuring the mercury intrusion amount. By using mercury porosimetry (mercury intrusion method), pores with a diameter of 0.01 to 1 μm are formed by voids in the particles of the carbonaceous material, irregularities due to steps on the particle surface, and contact surfaces between the particles. carbonaceous material to be measured and the corresponding preferably 0.01 cm ³ · ^{g -1} or more, more preferably 0.05 cm ³ · ^{g -1} or more, more preferably 0.1 cm ³ · ^{g -1} or more, , Preferably 0.6 cm ³ · g ⁻¹ or less, more preferably 0.4 cm ³ · g ⁻¹ or less, still more preferably 0. It has a pore size distribution of 3 cm ³ · g ⁻¹ or less.

If the pore size distribution exceeds the above range, a large amount of binder may be required when forming an electrode plate. On the other hand, if it falls below the above range, the high current density charge / discharge characteristics may be deteriorated, and the effect of relaxing the expansion and contraction of the electrode during charge / discharge may not be obtained.
Further, the total pore volume, which is obtained by mercury porosimetry (mercury intrusion method) and corresponds to pores having a diameter of 0.01 to 100 μm or less, is preferably 0.1 cm ³ · g ⁻¹ or more, and 0 more preferably .25cm ³ · ^{g -1} or more, more preferably 0.4 cm ³ · ^{g -1} or higher, and preferably at 10 cm ³ · ^{g -1} or less, more preferably ^{5 cm} 3 · ^{g -1} or less, 2 cm ³ · g ⁻¹ or less is more preferable. If the total pore volume exceeds the above range, a large amount of binder may be required when forming an electrode plate. On the other hand, if it falls below the above range, the effect of dispersing the thickener or the binder may not be obtained when forming an electrode plate.

  The average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, further preferably 0.5 μm or more, and preferably 50 μm or less, more preferably 20 μm or less, and more preferably 10 μm or less. Further preferred. If the average pore diameter exceeds the above range, a large amount of binder may be required. Moreover, when it is less than the above range, the high current density charge / discharge characteristics may deteriorate.

  The mercury intrusion is measured using a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) as an apparatus for mercury porosimetry. As a pretreatment, about 0.2 g of a sample is sealed in a powder cell and deaerated for 10 minutes at room temperature under vacuum (50 μmHg or less). Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa). The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step.

The pore size distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation. The surface tension (γ) of mercury is 485 dyne · cm ⁻¹ ( ¹ dyne = 10 μN) and the contact angle (ψ) is 140 °. As the average pore diameter, the pore diameter when the cumulative pore volume is 50% is used.
(7) 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)”. Become a true sphere.

It is desirable that the circularity of particles having a carbonaceous material particle size in the range of 3 to 40 μm is closer to 1.
Preferably it is 0.1 or more, 0.5 or more is more preferable, 0.8 or more is further more preferable, 0.85 or more is especially preferable, and 0.9 or more is especially preferable.
High current density charge / discharge characteristics generally improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

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

True density of (8) True Density carbonaceous material is preferably not 1.4 g · ^{cm -3} or more, 1.6 g · ^{cm -3} or more, and more preferably 1.8 g · ^{cm -3} or more, 2.0 g · ^{cm -3} or more are particularly preferred, also preferably not more than 2.26 g · ^{cm -3.} When the true density is below the above range, the crystallinity of carbon is too low, and the initial irreversible capacity may increase. The upper limit of the above range is the theoretical upper limit of the true density of graphite.

The true density of the carbonaceous material is measured by a liquid phase substitution method (pycnometer method) using butanol. The value obtained by the measurement is defined as the true density of the carbonaceous material in the present invention.
(9) Tap Density 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 preferred, 2 g · cm ⁻³ or less is preferred, 1.8 g · cm ⁻³ or less is more preferred, and 1.6 g · cm ⁻³ or less is particularly preferred.

When the tap density is below the above range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, when the above range is exceeded, there are too few voids between the particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.
The tap density is measured by passing through a sieve having an opening of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material in the present invention.

(10) Orientation ratio The orientation ratio of the carbonaceous material is preferably 0.005 or more, more preferably 0.01 or more, still more preferably 0.015 or more, and preferably 0.67 or less. When the orientation ratio is below the above range, the high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

The orientation ratio of the carbonaceous material is obtained by measuring by X-ray diffraction after pressure-molding the sample. Specifically, a molded body obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing with a 58.8 MN · m ⁻² is flush with the surface of the measurement sample holder using clay. Then, the X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbonaceous material, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material 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) face: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) face: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds (11) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is preferably 1 or more, preferably 10 or less, more preferably 8 or less, and still more preferably 5 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

  The aspect ratio 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.

(12) Secondary material mixing The secondary material mixing means that two or more carbonaceous materials having different properties are contained in the negative electrode and / or the negative electrode active material. The property here is selected from the group of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. It exhibits one or more characteristics.

As a particularly preferred example of mixing these secondary materials, the volume-based particle size distribution is not symmetrical when centered on the median diameter, and contains two or more carbonaceous materials having different Raman R values, And X-ray parameters are different.
As an example of the effect of the auxiliary material mixing, carbonaceous materials such as graphite (natural graphite, artificial graphite and the like), carbon black such as acetylene black, and amorphous carbon such as needle coke are contained as a conductive material. Reducing electrical resistance.

  When mixing a conductive material as a secondary material mixture, one type may be mixed alone, or two or more types may be mixed in any combination and ratio. The mixing ratio of the conductive material to the carbonaceous material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and usually 45% by mass or less. Preferably, 40 mass% or less is preferable. If the mixing ratio is less than the above range, it may be difficult to obtain the effect of improving conductivity. On the other hand, exceeding the above range may increase the initial irreversible capacity.

(13) 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, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.

  In the production of the non-aqueous electrolyte secondary battery, the thickness of the negative electrode active material layer per side of the current collector at the stage immediately before the non-aqueous electrolyte injection step is preferably 15 μm or more, more preferably 20 μm or more. 30 μm or more is more preferable, 150 μm or less is preferable, 120 μm or less is more preferable, and 100 μm or less is more preferable. When the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

In addition, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.
(14) Current collector As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.

  In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, and a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.

In addition, when the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.
A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

The following physical properties are desired for the current collector substrate.
(14-1) Average surface roughness (Ra)
The average surface roughness (Ra) of the negative electrode active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is preferably 0.05 μm or more, more preferably 0.1 μm or more. Preferably, 0.15 μm or more is more preferable, 1.5 μm or less is preferable, 1.3 μm or less is more preferable, and 1.0 μm or less is further preferable. When the average surface roughness (Ra) of the current collector substrate is within the above range, good charge / discharge cycle characteristics can be expected. Further, the area of the interface with the negative electrode active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit value of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally available as foils having a practical thickness as a battery. Since it is difficult, those of 1.5 μm or less are usually used.

(14-2) Tensile strength The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method).
The tensile strength of the current collector substrate is not particularly limited, but is preferably 100 N · mm ⁻² or more, more preferably 250 N · mm ⁻² or more, further preferably 400 N · mm ⁻² or more, and 500 N · mm ⁻² or more. Particularly preferred. The tensile strength is preferably as high as possible, but is usually 1000 N · mm ⁻² or less from the viewpoint of industrial availability. If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(14-3) 0.2% proof stress 0.2% proof stress is the magnitude of a load required to give a plastic (permanent) strain of 0.2%. It means that 0.2% deformation has occurred even when loaded. The 0.2% yield strength is measured with the same equipment and method as the tensile strength.
0.2% proof stress of the current collector substrate is not particularly limited, but is preferably 30 N · ^{mm -2} or more, more preferably 150 N · ^{mm -2} or more, and particularly preferably 300N · ^{mm -2} or more. The 0.2% resistance value is preferably as high as possible, but is usually 900 N · mm ⁻² or less from the viewpoint of industrial availability. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. Can do.

(14-4) Thickness of current collector 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, preferably 100 μm or less. More preferably, it is 30 μm or less. When the thickness of the current collector is thinner than 1 μm, the strength may be reduced, which may make application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The current collector may be mesh.

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

When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.
(16) Electrode density The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, and the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more. .2g · ^{cm -3} or more preferably, 1.3 g · ^{cm -3} or more, and also preferably 2 g · ^{cm -3} or less, more preferably 1.9 g · ^{cm -3} or less, 1.8 g · cm ⁻³ or less is more preferable, and 1.7 g · cm ⁻³ or less is particularly preferable. When the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases or non-aqueous system near the current collector / negative electrode active material interface. There is a case where high current density charge / discharge characteristics are deteriorated due to decrease in permeability of the electrolytic solution. On the other hand, if the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

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

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

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

In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and 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 the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable. When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio from which the amount of binders does not contribute to battery capacity may increase, and the fall of battery capacity may be caused. On the other hand, below the above range, the strength of the negative electrode may be reduced.

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

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

  When a thickener is used, the ratio of the thickener to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and 5% It is preferably at most 3 mass%, more preferably at most 3 mass%, still more preferably at most 2 mass%. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and the problem that the capacity | capacitance of a battery falls and the resistance between negative electrode active materials may increase.

(18) Electrode orientation ratio The electrode orientation ratio is preferably 0.001 or more, more preferably 0.005 or more, still more preferably 0.01 or more, and preferably 0.67 or less. When the electrode plate orientation ratio is below the above range, the high-density charge / discharge characteristics may be deteriorated. The upper limit of the above range is the theoretical upper limit of the electrode plate orientation ratio of the carbonaceous material.

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

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
-Target: Cu (Kα ray) graphite monochromator-Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree-Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds Sample preparation: (19) Impedance The resistance of the negative electrode when charged from a discharged state to 60% of the nominal capacity is preferably 100Ω or less, more preferably 50Ω or less, and 20Ω or less. Is more preferable, and / or the double layer capacity is preferably 1 × 10 ⁻⁶ F or more, more preferably 1 × 10 ⁻⁵ F or more, and further preferably 1 × 10 ⁻⁴ F. This is because when the negative electrode in the above range is used, the output characteristics are good and preferable.

To measure the resistance and double layer capacity of the negative electrode, after charging the non-aqueous electrolyte secondary battery to be measured at a current value at which the nominal capacity can be charged in 5 hours, the state of not charging / discharging for 20 minutes is maintained, Next, a capacitor having a capacity of 80% or more of the nominal capacity when discharged at a current value capable of discharging the nominal capacity in one hour is used.
About the non-aqueous electrolyte secondary battery in the above discharge state, the nominal capacity is charged to 60% of the nominal capacity at a current value that can be charged in 5 hours, and the non-aqueous electrolyte secondary battery is immediately put into a globe under an argon gas atmosphere. Move into the box. Here, the non-aqueous electrolyte secondary battery is quickly disassembled and taken out in a state where the negative electrode does not discharge or short-circuit, and if it is a double-sided coated electrode, the negative electrode active material on one side is peeled off without damaging the negative electrode active material on the other side Then, two negative electrodes are punched out to 12.5 mmφ, and are opposed to each other so that the surface of the negative electrode active material does not shift through the separator. 60μL of non-aqueous electrolyte used in the battery was dropped between the separator and both negative electrodes, and kept in close contact with the outside air, and the current collector of both negative electrodes was made conductive and the AC impedance method was carried out. To do.

The measurement is performed at a temperature of 25 ° C., and a complex impedance measurement is performed in a frequency band of 10 ⁻² to 10 ⁵ Hz. The surface resistance (R) is obtained by approximating the arc of the negative resistance component of the obtained Nyquist plot with a semicircle. The double layer capacity (Cdl) is determined.
(20) Area of negative electrode plate The area of the negative electrode plate is not particularly limited, but is preferably designed to be slightly larger than the opposing positive electrode plate so that the positive electrode plate does not protrude from the negative electrode plate. Further, from the viewpoint of suppressing the life of a cycle in which charge and discharge are repeated and deterioration due to high temperature storage, it is preferable that the area be as close to the positive electrode as possible, because the ratio of electrodes that work more uniformly and effectively is increased and the characteristics are improved. In particular, when used with a large current, the design of the area of the negative electrode plate is important.

<2-3-3. Structure, physical properties, preparation method of negative electrode using metal compound material and metal compound material>
The metal compound-based material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, and is a single metal or alloy that forms a lithium alloy, or oxides, carbides, nitrides, silicides thereof. Compounds such as oxides, sulfides and phosphides. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Especially, it is preferable that it is a single metal or alloy which forms a lithium alloy, and it is more preferable that there is a material containing a metal / metalloid element (that is, excluding carbon) of Group 13 or Group 14 of the periodic table. (Si), tin (Sn), or lead (Pb) (hereinafter, these three elements may be referred to as “SSP metal elements”), simple metals, alloys containing these atoms, or their metals (SSP metals) 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 , Compound compounds such as silicides, sulfides and phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

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

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

In addition, although the capacity per unit weight is inferior to that of 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. “Oxides of silicon and / or tin” of 3 or less, more preferably 1.1 or less.

-Element ratio of silicon and / or tin and nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin nitride” of 3 or less, more preferably 1.1 or less.
The elemental ratio of silicon and / or tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Carbide of silicon and / or tin” of 3 or less, more preferably 1.1 or less.

In addition, any one of the above-described negative electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.
The negative electrode in the non-aqueous electrolyte secondary battery of the present invention can be manufactured using any known method. Specifically, as a method for producing a negative electrode, for example, a method in which a material obtained by adding a binder or a conductive material to the above-described negative electrode active material is roll-molded as it is to form a sheet electrode, or a method in which compression molding is performed to obtain a pellet electrode In general, a coating method, a vapor deposition method, a sputtering method, a plating method, or the like on a current collector for a negative electrode (hereinafter sometimes referred to as “negative electrode current collector”), preferably by a coating method. A method of forming a thin film layer (negative electrode active material layer) containing the negative electrode active material described above is used. In this case, a binder, a thickener, a conductive material, a solvent, and the like are added to the above-described negative electrode active material to form a slurry, which is applied to the negative electrode current collector, dried and then pressed to increase the density. A negative electrode active material layer is formed on the current collector.

Examples of the material of the negative electrode current collector include steel, copper alloy, nickel, nickel alloy, and stainless steel. Of these, copper foil is preferred from the viewpoint of easy processing into a thin film and cost.
When using a metal compound-based material as the negative electrode active material, the thickness of the negative electrode current collector is preferably 1 μm or more, more preferably 5 μm or more, and preferably 100 μm or less, more preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, and conversely, if it is too thin, handling may be difficult.

  In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, the surface of these negative electrode current collectors is preferably subjected to a roughening treatment in advance. Surface roughening methods include blasting, rolling with a rough surface roll, abrasive cloth paper with abrasive particles fixed, grinding wheel, emery buff, machine that polishes the current collector surface with a wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  Further, in order to reduce the weight of the negative electrode current collector and improve the energy density per weight of the battery, a perforated negative electrode current collector such as an expanded metal or a punching metal can be used. This type of negative electrode current collector can be freely changed in weight by changing its aperture ratio. Further, when a negative electrode active material layer is formed on both surfaces of this type of negative electrode current collector, the negative electrode active material layer is further less likely to peel due to the rivet effect through the hole. However, when the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, and thus the adhesive strength may be lowered.

The slurry for forming the negative electrode active material layer is prepared by adding a binder, a thickener, and the like to the negative electrode active material and the conductive material.
The content of the negative electrode active material in the total of the negative electrode active material and the conductive material is preferably 70% by mass or more, more preferably 75% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass. It is as follows. If the content of the negative electrode active material is too small, the capacity of the non-aqueous electrolyte secondary battery tends to be insufficient, and if it is too large, the content of the binder or the like is relatively insufficient, resulting in the strength of the obtained negative electrode. It tends to run short. In addition, when using 2 or more types of negative electrode active materials together, what is necessary is just to make it the total amount of a negative electrode active material satisfy | fill the said range.

  Examples of the conductive material include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material acts as an active material. The content of the conductive material in the total of the negative electrode active material and the conductive material is preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less. It is. When the content of the conductive material is too small, the conductivity tends to be insufficient. When the content is too large, the content of the negative electrode active material or the like is relatively insufficient, which tends to decrease the battery capacity and strength. . In addition, when using 2 or more types of electrically conductive materials together, what is necessary is just to make it the total amount of an electrically conductive material satisfy | fill the said range.

The binder can be selected on the same basis as when a carbonaceous material is used as the negative electrode active material. Moreover, the specific example of a binder and the ratio of the binder with respect to a negative electrode active material are the same as that of the case of a carbonaceous material.
The thickener is used on the same basis as when a carbonaceous material is used as the negative electrode active material. Moreover, the specific example of a thickener and the ratio of the thickener with respect to a negative electrode active material are the same as that of the carbonaceous material.

  The slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive material, a binder, and a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. As the aqueous solvent, water is usually used, but a solvent other than water such as alcohols such as ethanol or cyclic amides such as N-methylpyrrolidone is used in combination at a ratio of about 30% by mass or less with respect to water. You can also As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. . Any one of these may be used alone, or two or more may be used in any combination and ratio.

The viscosity of the slurry is not particularly limited as long as it is a viscosity that can be applied onto the current collector. What is necessary is just to prepare suitably by changing the usage-amount of a solvent etc. at the time of preparation of a slurry so that it may become the viscosity which can be apply | coated.
The obtained slurry is applied onto the above-described negative electrode current collector, dried, and then pressed to form a negative electrode active material layer. The method of application is not particularly limited, and a method known per se can be used. The drying method is not particularly limited, and a known method such as natural drying, heat drying, or reduced pressure drying can be used.

The electrode structure when the negative electrode active material is made into an electrode by the above method is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more is more preferable, 1.3 g · cm ⁻³ or more is particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.9 g · cm ⁻³ or less is more preferable, and 1.8 g · cm ⁻³ or less. Is more preferable, and 1.7 g · cm ⁻³ or less is particularly preferable.

If the density of the active material present on the current collector exceeds the above range, the active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous electrolyte solution near the current collector / active material interface There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability. On the other hand, below the above range, the conductivity between the active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.
<2-3-4. Lithium-containing metal composite oxide material, and negative electrode configuration, physical properties, and preparation method using lithium-containing metal composite oxide material>
The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but lithium-containing composite metal oxide materials containing titanium are preferable, and lithium and titanium composite oxidation (Hereinafter sometimes abbreviated as “lithium titanium composite oxide”) is particularly preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in a negative electrode active material for a lithium ion non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

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

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

Particularly preferred representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.
In addition to the above requirements, the lithium titanium composite oxide as the negative electrode active material in the present invention further satisfies at least one of the characteristics such as physical properties and shapes shown in the following [1] to [16]. It is preferable to satisfy a plurality of items at the same time.

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

When the BET specific surface area is less than the above range, the reaction area in contact with the non-aqueous electrolyte when used as the negative electrode material may decrease, and the output resistance may increase. On the other hand, if it exceeds the above range,
The surface of the metal oxide crystal containing titanium and the portion of the end face increase, and due to this, distortion of the crystal also occurs, so the irreversible capacity cannot be ignored, and a preferable battery may be difficult to obtain. .

  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 below the above range, a large amount of binder is required at the time of producing the negative electrode, and as a result, the battery capacity may be reduced. On the other hand, if the above range is exceeded, a non-uniform coating surface tends to be formed when forming the negative electrode plate, which may be undesirable 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. If the volume-based average primary particle diameter exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder packing property and the specific surface area greatly decreases. There is a possibility that performance is likely to deteriorate. On the other hand, if it falls below the above range, the performance of the non-aqueous electrolyte secondary battery may be deteriorated, for example, the reversibility of charge / discharge is inferior due to the undeveloped crystals.

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

[4] Shape The shape of the lithium-titanium composite oxide particles may be any of lump shape, polyhedron shape, spherical shape, elliptical spherical shape, plate shape, needle shape, columnar shape, etc. as used in the past. do it,
It is preferably formed by forming secondary particles, and the shape of the secondary particles is spherical or elliptical.

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

[5] The tap density of the tap density lithium-titanium composite oxide is preferably from 0.05 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 is particularly preferable, 2.8 g · cm ⁻³ or less is preferable, 2.4 g · cm ⁻³ or less is further preferable, and 2 g · cm ⁻³ or less is particularly preferable. If the tap density of the lithium-titanium composite oxide is below the above range, the packing density is difficult to increase when used as a negative electrode, and the contact area between particles decreases, so the resistance between particles increases, and the output resistance increases. May increase. On the other hand, if the above range is exceeded, the voids between the particles in the electrode may become too small, and the output resistance may increase due to a decrease in the flow path of the non-aqueous electrolyte solution.

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

  The circularity of the lithium-titanium composite oxide is preferably closer to 1. Preferably, it is 0.10 or more, more preferably 0.80 or more, still more preferably 0.85 or more, and particularly preferably 0.90 or more. High current density charge / discharge characteristics generally improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

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

[7] Aspect ratio The aspect ratio of the lithium titanium composite oxide is preferably 1 or more, preferably 5 or less, more preferably 4 or less, still more preferably 3 or less, and particularly preferably 2 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and high current density charge / discharge characteristics may be deteriorated for a short time. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the lithium titanium composite oxide.

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

[8] Method for producing lithium-titanium composite oxide The method for producing lithium-titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention. A general method is used.
For example, a method of obtaining an active material by uniformly mixing a titanium source material such as titanium oxide and a source 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 elliptical active material. As an example, a titanium precursor material such as titanium oxide and, if necessary, a raw material material of another element are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create a spherical precursor. There is a method in which the active material is obtained by recovering and drying it as necessary, and then adding a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ and baking at a high temperature.

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

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

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

[10] Current collector As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is particularly preferable from the viewpoint of ease of processing and cost.
The shape of the current collector includes, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal when the current collector is a metal material. Among them, a metal foil film containing copper (Cu) and / or aluminum (Al) is preferable, copper foil and aluminum foil are more preferable, rolled copper foil by a rolling method, and electrolytic copper by an electrolytic method are more preferable. There are foils, both of which can be used as current collectors.

In addition, when the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used. Moreover, since the specific gravity of aluminum foil is light, when it is used as a current collector, the weight of the battery can be reduced and can be preferably used.
A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

Further, the following physical properties are desired for the current collector substrate.
[10-1] Average surface roughness (Ra) of current collector
The average surface roughness (Ra) of the active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, and is preferably 0.01 μm or more and 0.03 μm or more. More preferably, it is 1.5 μm or less, more preferably 1.3 μm or less, and further preferably 1.0 μm or less.

  This is because when the average surface roughness (Ra) of the current collector substrate is within the above range, good charge / discharge cycle characteristics can be expected. Further, the area of the interface with the active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. The upper limit value of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally available as foils having a practical thickness as a battery. Since it is difficult, those of 1.5 μm or less are usually used.

[10-2] Tensile strength of current collector The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method).
The tensile strength of the current collector substrate is not particularly limited, preferably at 50 N · ^{mm -2} or more, more preferably 100 N · ^{mm -2} or more, more preferably 150 N · ^{mm -2} or more. The tensile strength is preferably as high as possible, but usually 1000 N · mm ⁻² or less is desirable from the viewpoint of industrial availability.

If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.
[10-3] 0.2% proof stress 0.2% proof stress is the magnitude of a load necessary to give a plastic (permanent) strain of 0.2%. It means that 0.2% deformation has occurred even when loaded. The 0.2% yield strength is measured by the same apparatus and method as the tensile strength.

0.2% proof stress of the current collector substrate is not particularly limited, but is preferably 30 N · ^{mm -2} or more, more preferably 100 N · ^{mm -2} or more, more preferably 150 N · ^{mm -2} or more. The 0.2% proof stress is preferably as high as possible, but usually 900 N · mm ⁻² or less is desirable from the viewpoint of industrial availability.
If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. This is because it can.

[10-4] Thickness of current collector 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. 100 μm or less is more preferable, and 50 μm or less is still more preferable. When the thickness of the current collector is less than 1 μm, the strength decreases, and thus it may be difficult to apply the slurry for forming the negative electrode active material layer. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The current collector may be mesh.

[11] Thickness ratio of current collector and negative electrode active material layer The ratio of the thickness of the current collector to the active material layer is not particularly limited, but “(active material layer on one side immediately before non-aqueous electrolyte injection) ) / (Current collector thickness) ”is preferably 150 or less, more preferably 20 or less, still more preferably 10 or less, and preferably 0.1 or more. 4 or more is more preferable, and 1 or more is more preferable.

When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.
[12] Electrode density The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g More preferably, cm ⁻³ or more, 1.3 g · cm ⁻³ or more is further preferable, 1.5 g · cm ⁻³ or more is particularly preferable, 3 g · cm ⁻³ or less is preferable, and 2.5 g · cm ^{−. 3} or less is more preferable, 2.2 g · cm ⁻³ or less is more preferable, and 2 g · cm ⁻³ or less is particularly preferable.

When the density of the active material present on the current collector exceeds the above range, the binding between the current collector and the negative electrode active material becomes weak, and the electrode and the active material may be separated. On the other hand, below the above range, the conductivity between the negative electrode active materials may decrease, and the battery resistance may increase.
[13] Binder, solvent, etc. As described above, the slurry for forming the negative electrode active material layer is usually prepared by adding a binder (binder), a thickener, etc. to the solvent 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 polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer and hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly 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 that can dissolve or disperse the negative electrode active material, binder, thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexameryl phosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like.

In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed using a latex such as SBR.
In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.
The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and preferably 20% by mass or less. 15 mass% or less is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable.

When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio in which the amount of binders does not contribute to battery capacity may increase, and battery capacity may fall. On the other hand, if it is below the above range, the strength of the negative electrode is lowered, which may be undesirable in the battery production process.
In particular, when a rubbery polymer typified by SBR is contained in the main component, the ratio of the binder to the active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and 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 main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the active material is preferably 1% by mass or more, more preferably 2% by mass or more, and further more preferably 3% by mass or more. It is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less.
A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  When using a thickener, the ratio of the thickener to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.6% by mass or more. Moreover, it is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the active material which occupies for a negative electrode active material layer will fall, the problem that the capacity | capacitance of a battery falls, and the resistance between negative electrode active materials may increase.

[14] Impedance The resistance of the negative electrode when charged from the discharged state to 60% of the nominal capacity is preferably 500Ω or less, more preferably 100Ω or less, still more preferably 50Ω or less, and / or the double layer capacity is 1 × 10 ^{−. 6} F or more is preferable, 1 × 10 ⁻⁵ F or more is more preferable, and 3 × 10 ⁻⁵ F or more is more preferable. When the negative electrode in the above range is used, the output characteristics are good and preferable.

For the negative electrode resistance and double layer capacity, after charging the non-aqueous electrolyte secondary battery to be measured at a current value that can charge the nominal capacity in 5 hours, maintain the state of not charging / discharging for 20 minutes, A capacitor having a capacity of 80% or more of the nominal capacity when discharged at a current value capable of discharging the nominal capacity in one hour is used.
About the non-aqueous electrolyte secondary battery in the above-mentioned discharge state, the nominal capacity is charged to 60% of the nominal capacity at a current value that can be charged in 5 hours, and the non-aqueous electrolyte secondary battery is immediately put into a globe under an argon gas atmosphere. Move into the box. Here, the non-aqueous electrolyte secondary battery is quickly disassembled and taken out without the negative electrode being discharged or short-circuited, and if it is a double-sided coated electrode, the electrode active material on one side is peeled off without damaging the electrode active material on the other side. The two negative electrodes are punched out to 12.5 mmφ, and are opposed to each other so that the negative electrode active material surface does not shift through the separator. 60μL of non-aqueous electrolyte used in the battery was dropped between the separator and both negative electrodes, and kept in close contact with the outside air, and the current collector of both negative electrodes was made conductive and the AC impedance method was carried out. To do.

The measurement is performed at a temperature of 25 ° C. and a complex impedance measurement is performed in a frequency band of 10 ⁻² to 10 ⁵ Hz, and the arc of the negative resistance component of the obtained Nyquist plot is approximated by a semicircle to obtain a surface resistance (impedance Rct). The double layer capacitance (impedance Cdl) is obtained.
[15] Area of negative electrode plate Although the area of the negative electrode plate is not particularly limited, it should be 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. Is preferred. Further, from the viewpoint of suppressing the life of a cycle in which charge and discharge are repeated and deterioration due to high temperature storage, it is preferable that the area be as close to the positive electrode as possible, because the ratio of electrodes that work more uniformly and effectively is increased and the characteristics are improved. In particular, when the electrode is used at a large current, the design of the electrode area is important.

[16] Thickness of negative electrode plate The thickness of the negative electrode plate is designed according to the positive electrode plate used, and is not particularly limited, but the thickness of the negative electrode active material layer obtained by subtracting the thickness of the current collector is The thickness is preferably 15 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, and preferably 150 μm or less, more preferably 120 μm or less, still more preferably 100 μm or less.

<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 lithium ions. For example, a material containing lithium and at least one transition metal is preferable. 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.

V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO ₂ and LiNiO ₂ . Lithium / nickel composite oxides, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4 and} other lithium / manganese composite oxides, Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and those substituted with other metals such as Si.

As specific examples of the substituted ones, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4 and the} like.
As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

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

These surface adhering substances are, for example, a method in which they are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, and then dried. Then, it can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously.
The mass of the surface adhering substance adhering to the surface of the positive electrode active material is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more with respect to the mass of the positive electrode active material. Is 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. However, when the adhesion amount is less than the above range, the effect is not sufficiently exhibited. When the adhesion amount is more than the above range, the resistance may increase in order to inhibit the entry / exit of lithium ions, so the above range is preferable.
(3) Shape As the shape of the positive electrode active material particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. It is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material having only primary particles, so that the stress of expansion and contraction is relieved and deterioration is prevented.
In addition, spherical or oval spherical particles are less oriented at the time of forming the electrode than the plate-like equiaxially oriented particles, so there is less expansion and contraction of the electrode during charge and discharge, and when creating the electrode Also in the mixing with the conductive material, it is preferable because it is easily mixed uniformly.

(4) Tap Density Tap density positive electrode active material, preferably at 1.3 g · ^{cm -3} or more, 1.5 g · ^{cm -3} or more, and more preferably 1.6 g · ^{cm -3} or more, 1.7 g · cm ⁻³ or more is particularly preferable, preferably 2.5 g · cm ⁻³ or less, and more preferably 2.4 g · cm ⁻³ or less.

  By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. When the tap density of the positive electrode active material is lower than the above range, the amount of the dispersion medium necessary for forming the positive electrode active material layer is increased, and the necessary amount of the conductive material and the binder is increased. There are cases where the filling rate is restricted and the battery capacity is restricted. In general, the tap density is preferably as large as possible, but there is no particular upper limit. However, if the tap density is less than the above range, diffusion of lithium ions in the positive electrode active material layer using the non-aqueous electrolyte solution as a medium becomes rate-determining, and load characteristics are likely to deteriorate. There is a case.

The tap density of the positive electrode active material is measured by passing a sieve having a mesh size of 300 μm, dropping the sample onto a 20 cm ³ tapping cell to fill the cell volume, and then measuring a powder density measuring device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the weight 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 20 μm or less, more preferably 18 μm or less, and more preferably 16 μm. The following is more preferable, and 15 μm or less is particularly preferable. If the median diameter d50 is below the above range, a high bulk density product may not be obtained. If the median diameter d50 is above the above range, it takes time to diffuse lithium in the particles. That is, when an active material, a conductive material, a binder, or the like is slurried with a solvent and applied in a thin film shape, streaks may occur.

In addition, the filling property at the time of positive electrode preparation can be further improved by mixing two or more types of positive electrode active materials having different median diameters d50 at an arbitrary ratio.
The median diameter d50 of the positive electrode active material was measured using a 0.1% by mass sodium hexametaphosphate aqueous solution as a dispersion medium and LA-920 manufactured by Horiba, Ltd. as a particle size distribution meter. Measured by setting the refractive index to 1.24 after ultrasonic dispersion for 1 minute.

(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. If the above range is exceeded, it may be difficult to form spherical secondary particles, which may adversely affect the powder filling property, or the specific surface area will be greatly reduced, which may increase the possibility that the battery performance such as output characteristics will deteriorate. is there. On the other hand, below the above range, the performance of the non-aqueous electrolyte secondary battery may be deteriorated, for example, the reversibility of charge / discharge is inferior because the crystals are undeveloped.

The average primary particle size of the positive electrode active material is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.
(7) BET specific surface area As for the BET specific surface area of the positive electrode active material, the value of the specific surface area measured using the BET method is preferably 0.2 m ² · g ⁻¹ or more, and 0.3 m ² · g ^−1. or more, and further preferably 0.4 m ² · ^{g -1} or higher, and preferably not more than 4.0m ² · ^{g -1,} 2.5m more preferably ² · ^{g -1} or less, 1.5 m ² · g ⁻¹ or less is more preferable. When the value of the BET specific surface area is below the above range, the battery performance tends to be lowered. Moreover, when it exceeds the said range, a tap density becomes difficult to raise and the applicability | paintability at the time of positive electrode active material formation may fall.

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

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

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

Examples of other methods include transition metal source materials such as transition metal nitrates, sulfates, hydroxides, oxides, Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and other elements as necessary. The raw material is dissolved or pulverized and dispersed in a solvent such as water, and 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 10% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, and preferably 99.9% by mass or less. Yes, 99 mass% or less is more preferable. This is because if the content of the positive electrode active material is below the above range, the electric capacity may be insufficient. Moreover, it is because the intensity | strength of a positive electrode may be insufficient when it exceeds the said range. 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.

(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. If the content is lower than the above range, the conductivity may be insufficient. Moreover, when it exceeds the said range, battery capacity may fall.

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

The binder content in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, further preferably 3% by mass or more, and preferably 80% by mass or less. 60 mass% or less is more preferable, 40 mass% or less is still more preferable, and 10 mass% or less is especially preferable. When the ratio of the binder is less than the above range, the positive electrode active material cannot be sufficiently retained, the positive electrode has insufficient mechanical strength, and battery performance such as cycle characteristics may be deteriorated. Moreover, when it exceeds the said range, it may lead to a battery capacity or electroconductivity fall.

(Liquid medium)
The liquid medium used for preparing the slurry for forming the positive electrode active material layer is a solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. If it exists, there is no restriction | limiting in particular in the kind, You may use either an aqueous solvent or an organic solvent.

  Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of organic media include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

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

  When a thickener is used, the ratio of the thickener to the positive electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further 0.6% by mass or more. It is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. If it falls below the above range, applicability may be remarkably reduced, and if it exceeds the above range, the ratio of the active material in the positive electrode active material layer is lowered, the battery capacity is reduced, and the resistance between the positive electrode active materials. May increase.

(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.

If the density of the positive electrode active material layer exceeds the above range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface may decrease, and the charge / discharge characteristics at a high current density may decrease. Moreover, when less than the said range, the electroconductivity between active materials may fall and battery resistance may 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. If the thickness of the current collector is thinner than the above range, the strength required for the current collector may be insufficient. Moreover, when the thickness of the current collector is thicker than the above range, the handleability may be impaired.

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

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

(Discharge capacity)
When the non-aqueous electrolyte of the present invention is used, the electric capacity of the battery element housed in one battery exterior of the non-aqueous electrolyte secondary battery (electric capacity when the battery is discharged from a fully charged state to a discharged state) ) Is 3 ampere hours (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.

  If it falls below the above range, the voltage drop due to the electrode reaction resistance becomes large when taking out a large current, and the power efficiency may deteriorate. If the above range is exceeded, the electrode reaction resistance is reduced and the power efficiency is improved, but the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge is large, the durability of repeated charge / discharge is inferior, and overcharge and internal short circuit In some cases, the heat radiation efficiency may be deteriorated due to the sudden heat generation at the time of abnormality.

(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 obtained by subtracting the thickness of the current collector is preferably 10 μm or more, more preferably 20 μm or more, more preferably 200 μm or less, and more preferably 100 μm or less with respect to one surface of the current collector. .

<2-5. Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
There is no restriction | limiting in particular about the material and shape of a separator, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  As materials for the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, 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. . If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when 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. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, Preferably it is 0.5 micrometer or less, 0.2 micrometer or less is more preferable, Preferably it is 0.05 micrometer or more. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Things are used.

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

<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 any of the structures which wound the above-mentioned positive electrode plate and negative electrode plate spirally through the above-mentioned separator may be sufficient. The ratio of the volume of the electrode group to the volume in the battery (hereinafter referred to as electrode group occupancy) is preferably 40% or more, more preferably 50% or more, and preferably 90% or less, 80% The following is more preferable. When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, a gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

(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.

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

  The non-aqueous electrolyte of the present invention is effective in reducing reaction resistance related to lithium insertion / extraction with respect to the electrode active material, which is a factor that can realize good low-temperature discharge characteristics. However, in a battery having a normal DC resistance greater than 10 mΩ, the effect of reducing the reaction resistance may not be reflected 100% in the low-temperature discharge characteristics because of inhibition by the DC resistance. Therefore, this can be improved by using a battery having a small DC resistance component, and the effect of the non-aqueous electrolyte solution of the present invention can be sufficiently exhibited.

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

(Protective element)
Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation And the like (current cutoff valve). It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable that the protective element is designed so as not to 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.
[Preparation of non-aqueous electrolyte secondary battery]
<Preparation of positive electrode>
85 parts by mass of lithium manganate (Li _1.04 Mn _1.84 Al _0.12 O ₄ ) as a positive electrode active material, 10 parts by mass of carbon black as a conductive agent, polyvinylidene fluoride (PVdF) as a binder 5 parts by mass 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>
98 parts by mass of graphite powder, 100 parts by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of carboxymethylcellulose sodium) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber) as a binder 50 mass%) 2 parts by weight was added and mixed with a disperser to form a slurry. The obtained slurry was uniformly applied to a copper foil having a thickness of 12 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 in an aluminum laminate film, injected with an electrolyte solution described later, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to increase the adhesion between the electrodes, the sheet battery was sandwiched between glass plates and pressed.

[Evaluation of non-aqueous electrolyte secondary battery]
<Storage test>
-Initial charging / discharging 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 3.0 V at 0.1 C. Subsequently, the battery was charged at a constant current-constant voltage to 0.3 V at 0.33 C, and then discharged to 3.0 V at 0.33 C. This was carried out for 2 cycles for a total of 3 cycles to stabilize the non-aqueous electrolyte secondary battery.

-Aging The battery which carried out initial charging / discharging was hold | maintained at 60 degreeC for 24 hours. Thereafter, the battery was charged at a constant current-constant voltage up to 4.2 V at 0.33 C, and then discharged to 3.0 V at 0.33 C.
-High temperature storage test The aged battery was charged at a constant current-constant voltage at 0.33 C to 4.2 V at 25 ° C and then held at 75 ° C for 24 hours.

<Rate test after storage>
-Rate characteristic measurement after storage A rate test was performed on the battery after storage in an environment of 25 ° C. That is, a battery that had been charged at a constant current-constant voltage to 4.2 V at 0.33 C in an environment of 25 ° C. in advance was discharged at a constant current value corresponding to 8 C, and the storage capacity was 8 C after storage. Divided by the discharge capacity of Comparative Example 1 and normalized.

[Example 1]
Under a dry argon atmosphere, 1 mol / L (as a concentration in the non-aqueous electrolyte) of LiPF ₆ sufficiently dried was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4). Furthermore, 0.5% by mass of dimethylenemethane disulfonate (as the concentration in the non-aqueous electrolyte) and 0.5% by mass of lithium difluorophosphate (as the concentration in the non-aqueous electrolyte) sufficiently dried were dissolved. Then, a non-aqueous electrolyte solution was prepared. A battery was prepared by the above-described method using this non-aqueous electrolyte, and the rate characteristics after storage were measured. The results are shown in Table 1.

[Example 2]
A battery was prepared in the same manner as in Example 1 except that 2% by mass of bis (fluorosulfonyl) amidolithium was dissolved in the nonaqueous electrolytic solution instead of lithium difluorophosphate, and the rate characteristics were measured after storage. The results are shown in Table 1.
[Example 3]
A battery was prepared in the same manner as in Example 1 except that 0.1% by mass of lithium fluorosulfonate was dissolved in the non-aqueous electrolyte instead of lithium difluorophosphate, and the rate characteristics were measured after storage. The results are shown in Table 1.

[Comparative Example 1]
A battery was prepared in the same manner as in Example 1 except that dimethylenemethane disulfonate and lithium difluorophosphate were not dissolved in the nonaqueous electrolytic solution, and the rate characteristics were measured after storage. The results are shown in Table 1.
[Comparative Example 2]
A battery was prepared in the same manner as in Example 1 except that lithium difluorophosphate was not dissolved in the nonaqueous electrolytic solution, and the rate characteristics after storage were measured. The results are shown in Table 1.

[Comparative Example 3]
A battery was prepared in the same manner as in Example 1 except that dimethylenemethane disulfonate was not dissolved in the nonaqueous electrolytic solution, and the rate characteristics after storage were measured. The results are shown in Table 1.
[Comparative Example 4]
A battery was prepared and stored in the same manner as in Example 1 except that 2% by mass of bis (fluorosulfonyl) amidolithium was dissolved in place of lithium difluorophosphate without dissolving dimethylenemethane disulfonate in the non-aqueous electrolyte. The post-rate characteristics were measured. The results are shown in Table 1.

[Comparative Example 5]
A battery was prepared in the same manner as in Example 1 except that 0.1% by mass of lithium fluorosulfonate was dissolved in place of lithium difluorophosphate without dissolving dimethylenemethane disulfonate in the nonaqueous electrolytic solution. Rate characteristics were measured. The results are shown in Table 1.

  As apparent from Table 1, in the non-aqueous electrolyte, at least one lithium salt selected from the group consisting of lithium difluorophosphate, bis (fluorosulfonyl) amide lithium and lithium fluorosulfonate, and cyclic disulfone In the non-aqueous electrolyte secondary battery prepared using the non-aqueous electrolyte solution of the present invention containing an acid ester, a non-aqueous electrolyte solution containing one of these compounds or not containing both of these compounds is used. Compared with the non-aqueous electrolyte secondary battery prepared in this way, the rate characteristics after high-temperature storage are improved. Moreover, when only the cyclic disulfonic acid ester is added, the rate characteristics after storage are rather deteriorated, and this effect is not a simple addition of the two but an effect obtained only by the simultaneous use of both.

According to the non-aqueous electrolyte solution of the present invention, a non-aqueous electrolyte secondary battery having excellent discharge characteristics after high-temperature storage can be produced, so that any electronic device or the like in which the non-aqueous electrolyte secondary battery is used can be manufactured. It can be suitably used in the field.
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 uses include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini Discs, walkie-talkies, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorbikes, motorbikes, bicycles, lighting equipment, toys, game equipment, watches, electric tools, strobes, cameras, etc. Can be mentioned.

Claims (6)

  In a non-aqueous electrolyte solution comprising a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent, at least one selected from the group consisting of lithium difluorophosphate, lithium bis (fluorosulfonyl) amide and lithium fluorosulfonate A non-aqueous electrolytic solution comprising a lithium salt and a cyclic disulfonic acid ester. The non-aqueous electrolyte solution according to claim 1, wherein the cyclic disulfonic acid ester is a cyclic disulfonic acid ester represented by the following general formula (1).

(However, in the above general formula _(1), R 1, _{R 2} is a hydrocarbon group of each branched carbon atoms and optionally 1 to 10.)   The non-aqueous electrolysis characterized in that the cyclic disulfonate represented by the general formula (1) is at least one cyclic disulfonate selected from methylenemethane disulfonate, dimethylenemethane disulfonate, and trimethylenemethane disulfonate. liquid.   The nonaqueous system according to any one of claims 1 to 3, wherein the cyclic disulfonic acid ester represented by the general formula (1) is contained in the nonaqueous electrolytic solution in an amount of 0.01 mass% to 5 mass%. Electrolytic solution.   At least one lithium salt selected from the group consisting of the above lithium difluorophosphate, bis (fluorosulfonyl) amido lithium salt and lithium fluorosulfonic acid salt is contained in a non-aqueous electrolyte solution in an amount of 0.01 to 5 mass percent. The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous electrolyte solution is a non-aqueous electrolyte solution.   A non-aqueous electrolyte secondary battery comprising at least a positive electrode capable of inserting and extracting lithium ions, a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution comprises: A non-aqueous electrolyte secondary battery, which is the non-aqueous electrolyte solution according to any one of -5.