JP2016186915A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an excellent nonaqueous electrolyte that suppresses resistance increase and capacitance decrease during high temperature storage and a charge/discharge cycle of the battery; and a secondary battery employing the same.SOLUTION: A nonaqueous electrolyte contains an electrolyte and a nonaqueous solvent, where the nonaqueous electrolyte contains a compound represented by general formula (1) and a compound represented by general formula (2). Also provided is a nonaqueous electrolyte secondary battery employing the same.SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the same, and more specifically, a non-aqueous electrolyte for a lithium secondary battery containing a specific component and the same. The present invention relates to a lithium secondary battery.

Along with the downsizing of electronic equipment due to the rapid development of modern industry, there has been a strong demand for higher capacity of secondary batteries. Therefore, lithium secondary batteries having higher energy density than nickel / cadmium batteries and nickel / hydrogen batteries have been developed, and up to now, efforts to improve the performance have been repeated.
Components constituting the lithium secondary battery are mainly classified into a positive electrode, a negative electrode, a separator, and an electrolytic solution. Of these, electrolytes generally include electrolytes such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO ₃ , Cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl acetate and methyl propionate A non-aqueous electrolyte solution dissolved in a non-aqueous solvent such as a liquid is used.

In recent years, against the background of global issues such as environmental issues and energy issues, great expectations have been placed on the application of lithium secondary batteries to large-scale power sources such as in-vehicle power sources and stationary power sources. However, since such a battery is generally expected to be used for a long period of time, life performance and resistance performance higher than those of conventional lithium secondary batteries are required.
As one of efforts to further improve various characteristics of the lithium secondary battery, efforts are being made to add an arbitrary compound to the electrolytic solution.

For example, Patent Document 1 reports that the addition of a specific fluorosulfonate to the electrolyte of a non-aqueous electrolyte battery improves the battery impedance and the capacity retention rate during the charge / discharge cycle. ing.
Patent Document 2 discloses a capacity maintenance ratio and a resistance maintenance ratio during a charge / discharge cycle of a battery by adding a sulfonate ester having a specific SF bond to the electrolyte of a non-aqueous electrolyte battery. Has been reported to improve.

  Patent Document 3 reports that the addition of a specific sulfonic acid ester to the electrolyte of a non-aqueous electrolyte battery improves the discharge capacity maintenance rate after the battery charge / discharge cycle. .

JP 2011-187440 A JP 2014-183090 A International Publication No. 2009/113545

As described above, efforts have been made to improve battery durability, but this is not yet sufficient to achieve sufficient battery characteristics, and further improvements are required. Yes.
The present invention has been made in view of such background art, and is an excellent non-aqueous electrolyte solution that suppresses a decrease in capacity and an increase in resistance during charge / discharge cycles and high-temperature storage of a battery, and a secondary battery using the same Is to provide.

As a result of intensive studies to solve the above problems, the present inventors have improved the capacity retention ratio and resistance retention ratio after the battery charge / discharge cycle by containing a specific compound as the non-aqueous electrolyte. As a result, the present invention has been completed.
That is, the gist of the present invention is as follows.
(A) A non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent, wherein the non-aqueous electrolyte comprises a compound represented by the following general formula (1) and a compound represented by the following general formula (2) A non-aqueous electrolyte characterized by containing.

M (FSO ₃ ) _x (1)
[M is a metal atom, NR ¹ ₄ or PR ¹ ₄ (where R ¹ is an organic group having 1 to 12 carbon atoms or a hydrogen atom (provided that all four R ¹ are hydrogen atoms) A plurality of R ¹ may be the same as or different from each other, and some or all of the four R ¹ may form a ring together with the nitrogen atom or phosphorus atom to which they are bonded. is good), when M is a metal atom, x is an integer of 1 or more to a valence of the metal atom M, when M is ^NR _{1 4} or ^PR _{1 4,} x is 1]

(R ² represents a halogen atom or an organic group that may contain a C 1-6 hetero atom, and R ³ represents an organic group that may contain a C 3-12 hetero atom)
(B) In the general formula (1), M is a metal atom, and the nonaqueous electrolytic solution according to (a).
(C) The nonaqueous electrolytic solution according to (a), wherein in the general formula (1), M is any one of a lithium atom, a sodium atom, and a potassium atom.
(D) The non-aqueous electrolyte according to any one of (a) to (c), wherein R ² is a halogen atom in the general formula (2).
(E) The non-aqueous electrolyte according to (a) to (c), wherein R ² is a hydrocarbon group in the general formula (2) (f) In the general formula (2), R ² is a C1-C6 organic group containing a hetero atom, The non-aqueous electrolyte solution as described in (a)-(c) characterized by the above-mentioned.
(G) The non-aqueous electrolyte solution according to any one of (a) to (f), wherein R ³ is an organic group having 3 to 12 carbon atoms having an oxygen atom in the general formula (2).
(H) The non-aqueous electrolyte solution according to any one of (a) to (c), wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3).

(R ² represents a halogen atom or an organic group that may contain a C 1-6 hetero atom, and R ⁴ represents a C 1-5 alkylene group that may have a halogen atom. R ⁵ represents (It represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group, an alkynyl group, or an aryl group having 6 to 10 carbon atoms, which may have a halogen atom.)
(I) The content of the compound represented by the general formula (1) is 0.01% by mass or more and 10% by mass or less with respect to the whole non-aqueous electrolyte solution (a) to (h) The non-aqueous electrolyte solution described in 1.
(J) The content of the compound represented by the general formula (2) is 0.01% by mass or more and 10% by mass or less with respect to the entire non-aqueous electrolyte solution (a) to (i) The non-aqueous electrolyte solution described in 1.
(K) A non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of inserting and extracting metal ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte described in (a) to (j) is used. A non-aqueous electrolyte secondary battery characterized by the above.
(L) The non-aqueous electrolyte secondary battery according to (k), wherein the positive electrode capable of inserting and extracting metal ions includes at least one layered transition metal oxide.
(M) The non-aqueous electrolyte secondary battery according to (k) or (l), wherein the negative electrode capable of inserting and extracting metal ions contains at least a carbon compound.

  As shown in the examples described later, by using the present invention, the capacity retention rate and resistance retention rate after the charge / discharge cycle can be increased more than ever.

[1. Non-aqueous electrolyte]
<1-1. Compound represented by general formula (1)>
The non-aqueous electrolyte solution of the present invention contains a compound represented by the following general formula (1).
M (FSO ₃ ) _x (1)
[M is a metal atom, NR ¹ ₄ or PR ¹ ₄ (where R ¹ is an organic group having 1 to 12 carbon atoms or a hydrogen atom (provided that all four R ¹ are hydrogen atoms) A plurality of R ¹ may be the same as or different from each other, and some or all of the four R ¹ may form a ring together with the nitrogen atom or phosphorus atom to which they are bonded. is good), when M is a metal atom, x is an integer of 1 or more to a valence of the metal atom M, when M is ^NR _{1 4} or ^PR _{1 4,} x is 1]
In general formula (1), M represents any quaternary ammonium, quaternary phosphonium represented by ^PR _{1 4} represented by a metal atom, ^NR _{1 4.}

  In the general formula (1), when M is a metal atom, x is a valence of the metal atom and is an integer of 1 or more, specifically, 1, 2 or 3. Examples of the metal atom include alkali metal atoms such as lithium atom, sodium atom and potassium atom, alkaline earth metal atoms such as magnesium atom and calcium atom, transition metal atoms such as iron atom and copper atom, lithium atom, A sodium atom and a potassium atom are preferable, and a lithium atom is particularly preferable.

Preferred fluorosulfonates include LiFSO3, NaFSO3, KFSO3,
Examples thereof include CsFSO3, Mg (FSO3) 2, Ca (FSO3) 2, Fe (FSO3) 2, Cu (FSO3) 2, Al (FSO3) 3. Among these, LiFSO3, NaFSO3, and KFSO3 are particularly preferable, and LiFSO3 is most preferable from the viewpoint of solubility in the electrolytic solution.

In the general formula (1), when the quaternary phosphonium M is represented by quaternary ammonium or ^PR _{1 4} represented by ^NR _{1 4,} x is 1.
In NR ¹ ₄ or PR ¹ ₄ , R ¹ is an organic group having 1 to 12 carbon atoms or a hydrogen atom (provided that all four R ¹ are not hydrogen atoms) and are the same as each other And some or all of the four R ^{1 s} may form a ring together with the nitrogen atom or phosphorus atom to which they are bonded.

  Examples of the organic group having 1 to 12 carbon atoms include linear or branched chain alkyl groups, cyclic alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and aralkyl groups. These groups may be substituted with a halogen atom. Moreover, these groups can also contain hetero atoms, such as oxygen, nitrogen, sulfur, phosphorus, and silicon, and each group may be couple | bonded by the saturated or unsaturated bond by these atoms. Specifically, chain alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, sec-butyl group; cyclohexyl group, norbornanyl group, etc. Cyclic alkyl group; Alkenyl group such as vinyl group, 1-propenyl group, allyl group, butenyl group, 1,3-butadienyl group; Alkynyl group such as ethynyl group, propynyl group, butynyl group; An aryl group such as a phenyl group; an aralkyl group such as a benzyl group or a phenylethyl group; a halogenated alkyl group such as a trifluoromethyl group, a trifluoroethyl group or a hexafluoropropyl group; an ethoxycarbonylethyl group or the like; Carbonyl group-containing alkyl group; methoxyethyl group, phenoxymethyl group, ethoxyethyl group, allyloxy Ethyl group, methoxy ethoxy ethyl group, an ether group-containing alkyl groups such as ethoxyethoxy ethyl group; such a sulfonyl group-containing alkyl group such as a sulfonyl methyl group. Also included are trialkylsilyl groups such as a trimethylsilyl group. Preferred are methyl group, ethyl group, n-propyl group, n-butyl group, trifluoromethyl group, trifluoroethyl group, methoxyethyl group, methoxyethoxyethyl group, and trimethylsilyl group.

The preferred molecular structure of the NR ¹ _4, tetramethylammonium, tetraethylammonium, quaternary ammonium cation represented by tetrabutylammonium and the like;
Pyrrolidinium cations represented by dimethylpyrrolidinium, methylethylpyrrolidinium, diethylpyrrolidinium, etc .;
Piperidinium cations represented by dimethylpiperidinium, methylethylpiperidinium, diethylpiperidinium and the like;
Morpholinium cations represented by dimethylmorpholinium, methylethylmorpholinium, diethylmorpholinium and the like;
Pyridinium cations represented by 1-methylpyridinium, 1-ethylpyridinium and the like;
Pyridazinium cations represented by 1-methylpyridazinium, 1-ethylpyridazinium and the like;
Pyrimidinium cations represented by 1-methylpyrimidinium, 1-ethylpyrimidinium and the like;
Pyrazinium cations represented by 1-methylpyrazinium, 1-ethylpyrazinium and the like;
Imidazolium cations such as 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,2,3-trimethylimidazolium;
Oxazolium cations such as 1-methyloxazolium and 1-ethyloxazolium;
Thiazolium cations such as 1-methylthiazolium, 1-ethylthiazolium;
Pyrazolium cations such as 1-methylpyrazolium, 1-ethylpyrazolium;
Examples include triazolium cations such as 1-methyltriazolium and 1-ethyltriazolium.

  Preferred ammonium cation structures include tetramethylammonium, trimethylethylammonium, trimethylpropylammonium, trimethylbutylammonium, trimethylpentylammonium, trimethylhexylammonium, dimethyldiethylammonium, dimethylethylpropylammonium, dimethylethylbutylammonium, dimethylethylpentylammonium, Dimethylethylhexylammonium, dimethyldipropylammonium, dimethylpropylbutylammonium, dimethylpropylpentylammonium, dimethylpropylhexylammonium, dimethyldibutylammonium, dimethylbutylpentylammonium, dimethylbutylhexylammonium, dimethyldipentylammonium , Dimethylpentylhexylammonium, dimethyldihexylammonium, methyldiethylpropylammonium, methyldiethylbutylammonium, methyldiethylpentylammonium, methyldiethylhexylammonium, methylethyldipropylammonium, methylethylpropylbutylammonium, methylethylpropylpentylammonium, methyl Ethylpropylhexylammonium, methylethyldibutylammonium, methylethylbutylpentylammonium, methylethylbutylhexylammonium, methylethyldipentylammonium, methylethylpentylhexylammonium, methylethyldihexylammonium, methyltripropylammonium, methyldipropylbutylan Nitrogen, methyldipropylpentylammonium, methyldipropylhexylammonium, methylpropyldibutylammonium, methylpropylbutylpentylammonium, methylpropylbutylhexylammonium, methylpropyldipentylammonium, methylpropylpentylhexylammonium, methylpropyldihexylammonium, methyltributylammonium , Methyl dibutyl pentyl ammonium, methyl dibutyl hexyl ammonium, methyl butyl dipentyl ammonium, methyl butyl pentyl hexyl ammonium, methyl butyl dihexyl ammonium, methyl tripentyl ammonium, methyl dipentyl hexyl ammonium, methyl pentyl dihexyl ammonium, methyl trihexyl Cations of trimethylallylammonium, trimethylbutenyl, ammonium, triethylpropylammonium, triethylbutylammonium, triethylpentylammonium, triethylhexylammonium, etc., or compounds in which one or more hydrogen atoms in these alkyl groups are substituted with fluorine atoms Examples include ammonium, trimethylmethoxymethylammonium, trimethylmethoxyethylammonium, trimethylmethoxyethoxyethylammonium, and the like.

Preferred pyrrolidinium cation structures include dimethylpyrrolidinium, methylethylpyrrolidinium, diethylpyrrolidinium, methylpropylpyrrolidinium, ethylpropylpyrrolidinium, dipropylpyrrolidinium, methylbutylpyrrolidinium, ethyl Cation of methylbutylpyrrolidinium, ethylvinylpyrrolidinium, propylbutylpyrrolidinium, propylbutylpyrrolidinium, dibutylpyrrolidinium, or a compound in which one or more of hydrogen atoms in these alkyl groups are substituted with fluorine atoms Ni, propyl vinyl pyrrolidinium, butyl vinyl pyrrolidinium, methyl allyl pyrrolidinium, ethyl allyl pyrrolidinium, propyl allyl pyrrolidinium, butyl allyl pyrrolidinium, diallyl pyrrolidinium, methyl buteni Pyrrolidinium, ethylbutenylpyrrolidinium, propylbutenylpyrrolidinium, butylbutenylpyrrolidinium, dibutenylpyrrolidinium, methylmethoxymethylpyrrolidinium, methylmethoxyethylpyrrolidinium, methylethoxyethylpyrrolidinium, Methylmethoxyethoxyethylpyrrolidinium, methylethoxyethoxyethylpyrrolidinium, ethylmethoxymethylpyrrolidinium, ethylmethoxyethylpyrrolidinium, ethylethoxyethylpyrrolidinium, ethylmethoxyethoxyethylpyrrolidinium, ethylethoxyethoxyethylpyrrole Dinium, propylmethoxymethylpyrrolidinium, propylmethoxyethylpyrrolidinium, propylethoxyethylpyrrolidinium, propylmethoxyethoxy Tyrpyrrolidinium, propylethoxyethoxyethylpyrrolidinium, butylmethoxymethylpyrrolidinium, butylmethoxyethylpyrrolidinium, butylethoxyethylpyrrolidinium, butylmethoxyethoxyethylpyrrolidinium, butylethoxyethoxyethylpyrrolidinium, etc. Is mentioned.

  Preferred piperidinium cation structures include dimethylpiperidinium, methylethylpiperidinium, diethylpiperidinium, methylpropylpiperidinium, ethylpropylpiperidinium, dipropylpiperidinium, methylbutylpiperidinium, ethyl Cation of methylbutylpiperidinium, propylbutylpiperidinium, dibutylpiperidinium, or a compound in which one or more hydrogen atoms in these alkyl groups are substituted with fluorine atoms, methylvinylpiperidinium, ethylvinylpiperidi Nium, propylvinylpiperidinium, butylvinylpiperidinium, methylallylpiperidinium, ethylallylpiperidinium, propylallylpiperidinium, butylallylpiperidinium, diallylpiperidinium, methylbuteni Piperidinium, ethylbutenylpiperidinium, propylbutenylpiperidinium, butylbutenylpiperidinium, dibutenylpiperidinium, methylmethoxymethylpiperidinium, methylmethoxyethylpiperidinium, methylethoxyethylpiperidinium, Methylmethoxyethoxyethylpiperidinium, methylethoxyethoxyethylpiperidinium, ethylmethoxymethylpiperidinium, ethylmethoxyethylpiperidinium, ethylethoxyethylpiperidinium, ethylmethoxyethoxyethylpiperidinium, ethylethoxyethoxyethylpiper Peridinium, propylmethoxymethylpiperidinium, propylmethoxyethylpiperidinium, propylethoxyethylpiperidinium, propylmethoxyethoxy Tilpiperidinium, propylethoxyethoxyethylpiperidinium, butylmethoxymethylpiperidinium, butylmethoxyethylpiperidinium, butylethoxyethylpiperidinium, butylmethoxyethoxyethylpiperidinium, butylethoxyethoxyethylpiperidinium, etc. Is mentioned.

Preferred morpholinium cation structures include dimethylmorpholinium, methylethylmorpholinium, diethylmorpholinium, methylpropylmorpholinium, ethylpropylmorpholinium, dipropylmorpholinium, methylbutylmorpholinium, ethyl Cation of butyl morpholinium, propyl butyl morpholinium, dibutyl morpholinium, or a compound in which one or more of hydrogen atoms in these alkyl groups is substituted with a fluorine atom, methyl vinyl morpholinium, ethyl vinyl morpholine Nitrogen, propylvinylmorpholinium, butylvinylmorpholinium, methylallylmorpholinium, ethylallylmorpholinium, propylallylmorpholinium, butylallylmorpholinium, diallylmorpholinium, methylbuteni Morpholinium, ethylbutenylmorpholinium, propylbutenylmorpholinium, butylbutenylmorpholinium, dibutenylmorpholinium, methylmethoxymethylmorpholinium, methylmethoxyethylmorpholinium, methylethoxyethylmorpholinium, Methylmethoxyethoxyethylmorpholinium, methylethoxyethoxyethylmorpholinium, ethylmethoxymethylmorpholinium, ethylmethoxyethylmorpholinium, ethylethoxyethylmorpholinium, ethylmethoxyethoxyethylmorpholinium, ethylethoxyethoxyethylmol Holinium, propylmethoxymethylmorpholinium, propylmethoxyethylmorpholinium, propylethoxyethylmorpholinium, propylmethoxyethoxy Tilmorpholinium, propylethoxyethoxyethylmorpholinium, butylmethoxymethylmorpholinium, butylmethoxyethylmorpholinium, butylethoxyethylmorpholinium, butylmethoxyethoxyethylmorpholinium, butylethoxyethoxyethylmorpholinium, etc. Is mentioned.

Preferred pyridinium cation structures include 1-ethylpyridinium, 1-propylpyridinium, 1-butylpyridinium, 1-pentylpyridinium, 1-hexylpyridinium, 1-allylpyridinium, 1-butenylpyridinium, 1-methoxymethylpyridinium, 1 -Methoxyethylpyridinium etc. are mentioned.
Preferred pyridazinium cation structures include 1-ethylpyridazinium, 1-propylpyridazinium, 1-butylpyridazinium, 1-pentylpyridazinium, 1-hexylpyridazinium, Examples include 1-allylpyridazinium, 1-butenylpyridazinium, 1-methoxymethylpyridazinium, 1-methoxyethylpyridazinium.

Preferred pyrimidinium cation structures include 1-ethylpyrimidinium, 1-propylpyrimidinium, 1-butylpyrimidinium, 1-pentylpyrimidinium, 1-hexylpyrimidinium, 1-allylpyrimidinium 1-butenylpyrimidinium, 1-methoxymethylpyrimidinium, 1-methoxyethylpyrimidinium, and the like.
Preferred pyrazinium cation structures include 1-ethylpyrazinium, 1-propylpyrazinium, 1-butylpyrazinium, 1-pentylpyrazinium, 1-hexylpyrazinium, 1-allylpyrazinium 1-butenyl pyrazinium, 1-methoxymethyl pyrazinium, 1-methoxyethyl pyrazinium and the like.

Preferred imidazolium cation structures include 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-pentyl- 3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-propylimidazolium, 1-ethyl-3-butylimidazolium, 1-ethyl-3- Pentylimidazolium, 1-ethyl-3-hexylimidazolium, 1,3-dipropylimidazolium, 1-propyl-3-butylimidazolium, 1-propyl-3-pentylimidazolium, 1-hexyl-3-butyl Imidazolium, 1,2,3-trimethylimidazolium, 1-ethyl 2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-pentyl-2,3-dimethylimidazolium, 1-hexyl-2, 3-dimethylimidazolium, 1,3-diethyl-2-methylimidazolium, 1-propyl-2-methyl-3-ethylimidazolium, 1-butyl-2-methyl-3-ethylimidazolium, 1-pentyl- 2-methyl-3-ethylimidazolium, 1-hexyl-2-methyl-3-ethylimidazolium, 1,2,3,4,5-hexamethylimidazolium, 1-ethyl-2,3,4,5 -Tetramethylimidazolium, 1-propyl-2,3,4,5-tetramethylimidazolium, 1-butyl-2,3,4,5-tetramethyl One or more of hydrogen atoms in imidazolium, 1-pentyl-2,3,4,5-tetramethylimidazolium, 1-hexyl-2,3,4,5-tetramethylimidazolium, or their alkyl groups 1-allyl-3-methylimidazolium, 1-allyl-3-ethylimidazolium, 1-allyl-3-propylimidazolium, 1-allyl-3-butylimidazolium 1-allyl-2,3-dimethylimidazolium, 1-allyl-2,3,4,5-tetramethylimidazolium, 1-butenyl-3-methylimidazolium, 1-butenyl-3-ethylimidazolium, 1-butenyl-3-propylimidazolium, 1-butenyl-3-butylimidazolium, 1-butenyl-2,3-dimethylimidazole Midazolium, 1-butenyl-2,3,4,5-tetramethylimidazolium, 1-methoxymethyl-3-methylimidazolium, 1-methoxymethyl-3-ethylimidazolium, 1-methoxymethyl-3-propylimidazo 1-methoxymethyl-3-butylimidazolium, 1-methoxymethyl-2,3-dimethylimidazolium, 1-methoxymethyl-2,3,4,5-tetramethylimidazolium, 1-methoxyethyl-3 -Methylimidazolium, 1-methoxyethyl-3-ethylimidazolium, 1-methoxyethyl-3-propylimidazolium, 1-methoxyethyl-3-butylimidazolium, 1-methoxyethyl-2,3-dimethylimidazolium 1-methoxyethyl-2,3,4,5-tetramethylimidazole Potassium, and the like.

  Preferred oxazolium cation structures include 1-ethyloxazolium, 1-propyloxazolium, 1-butyloxazolium, 1-pentyloxazolium, 1-hexyloxazolium, 1-allyloxazolium 1-butenyloxazolium, 1-methoxymethyloxazolium, 1-methoxyethyloxazolium, 1-ethyl-2,4,5-trimethyloxazolium, 1-propyl-2,4,5- Trimethyloxazolium, 1-butyl-2,4,5-trimethyloxazolium, 1-pentyl-2,4,5-trimethyloxazolium, 1-hexyl-2,4,5-trimethyloxazolium, 1-allyl-2,4,5-trimethyloxazolium, 1-butenyl-2,4,5-trimethyloxazolium, 1-methyl Kishimechiru 2,4,5-trimethyl oxazolium, 1-methoxyethyl-2,4,5-trimethyl oxazolium and the like.

  Preferred thiazolium cation structures include 1-ethylthiazolium, 1-propylthiazolium, 1-butylthiazolium, 1-pentylthiazolium, 1-hexylthiazolium, 1-allylthiazolium. 1-butenylthiazolium, 1-methoxymethylthiazolium, 1-methoxyethylthiazolium, 1-ethyl-2,4,5-trimethylthiazolium, 1-propyl-2,4,5- Trimethylthiazolium, 1-butyl-2,4,5-trimethylthiazolium, 1-pentyl-2,4,5-trimethylthiazolium, 1-hexyl-2,4,5-trimethylthiazolium, 1-allyl-2,4,5-trimethylthiazolium, 1-butenyl-2,4,5-trimethylthiazolium, 1-methoxymethyl-2,4,5-trimethyl Thiazolium, 1-methoxyethyl-2,4,5-trimethyl thiazolium, and the like.

  Preferred pyrazolium cation structures include 1-ethylpyrazolium, 1-propylpyrazolium, 1-butylpyrazolium, 1-pentylpyrazolium, 1-hexylpyrazolium, 1-allylpyrazolium 1-butenylpyrazolium, 1-methoxymethylpyrazolium, 1-methoxyethylpyrazolium, 1-ethyl-2,3,4,5-tetramethylpyrazolium, 1-propyl-2,3 , 4,5-tetramethylpyrazolium, 1-butyl-2,3,4,5-tetramethylpyrazolium, 1-pentyl-2,3,4,5-tetramethylpyrazolium, 1-hexyl -2,3,4,5-tetramethylpyrazolium, 1-allyl-2,3,4,5-tetramethylpyrazolium, 1-butenyl-2,3,4,5-tetramethylpyrazolium 1-methoxymethyl-2,3,4,5-tetramethyl-pyrazolium, 1-methoxyethyl-2,3,4,5-tetramethyl-pyrazolium, and the like.

Preferred triazolium cation structures include 1-ethyltriazolium, 1-propyltriazolium, 1-butyltriazolium, 1-pentyltriazolium, 1-hexyltriazolium, 1-allyltriazolium. 1-butenyltriazolium, 1-methoxymethyltriazolium, 1-methoxyethyltriazolium, 1-ethyl-2,3,4,5-tetramethyltriazolium, 1-propyl-2,3 , 4,5-tetramethyltriazolium, 1-butyl-2,3,4,5-tetramethyltriazolium, 1-pentyl-2,3,4,5-tetramethyltriazolium, 1-hexyl -2,3,4,5-tetramethyltriazolium, 1-allyl-2,3,4,5-tetramethyltriazolium, 1-butenyl-2,3,4 5-tetramethyl-triazolium, 1-methoxymethyl-2,3,4,5-tetramethyl-triazolium, 1-methoxyethyl -2,3,4,5
-Tetramethyltriazolium etc. are mentioned.

Also these NR ¹ ₄ in the fluorosulfonic acid salt with a cation structure, fluorosulfonic acid tetramethylammonium, fluorosulfonic acid tetraethylammonium, fluorosulfonic acid tetrabutylammonium, fluorosulfonic acid dimethyl pyrrolidinium, fluorosulfonic acid-methylethyl Pyrrolidinium, diethylpyrrolidinium fluorosulfonate, dimethylpiperidinium fluorosulfonate, methylethylpiperidinium fluorosulfonate, diethylpiperidinium fluorosulfonate, dimethylmorpholinium fluorosulfonate, methylethyl fluorosulfonate Morpholinium, diethylmorpholinium fluorosulfonate is easy to obtain and handle, lowers internal battery impedance and improves input / output characteristics Particularly preferred from the point.

Preferred cation structure of PR ¹ _4, triethyl butyl phosphonium, triethyl pentyl phosphonium, tri-ethylhexyl phosphonium, triethyl heptyl phosphonium, triethyl octyl phosphonium, diethyl propyl butyl phosphonium, diethyl propyl pentyl phosphonium, diethyl propyl hexyl phosphonium, diethyl propyl heptyl phosphonium, Diethylpropyloctylphosphonium, diethylbutylpentylphosphonium, diethylbutylhexylphosphonium, diethylbutylheptylphosphonium, diethylbutyloctylphosphonium, diethylpentylhexylphosphonium, diethylpentylheptylphosphonium, diethylpentyloctylphosphonium, diethylhexylhept Ruphosphonium, diethylhexyloctylphosphonium, diethylheptyloctylphosphonium, diethyldioctylphosphonium, ethyldipropylbutylphosphonium, ethyldipropylpentylphosphonium, ethyldipropylhexylphosphonium, ethyldipropylheptylphosphonium, ethyldipropyloctylphosphonium, ethylpropyldibutyl Phosphonium, ethylpropylbutylpentylphosphonium, ethylpropylbutylhexylphosphonium, ethylpropylbutylheptylphosphonium, ethylpropylbutyloctylphosphonium, ethylpropyldipentylphosphonium, ethylpropylpentylhexylphosphonium, ethylpropylpentylheptylphosphonium, ethylpropylpentylio Octylphosphonium, ethylpropyldihexylphosphonium, ethylpropylhexylheptylphosphonium, ethylpropylhexyloctylphosphonium, ethylpropyldiheptylphosphonium, ethylpropylheptyloctylphosphonium, ethylpropyldioctylphosphonium, ethyltributylphosphonium, ethyldibutylpentylphosphonium, ethyldibutylhexylphosphonium , Ethyl dibutyl heptyl phosphonium, ethyl dibutyl octyl phosphonium, ethyl butyl dipentyl phosphonium, ethyl butyl pentyl hexyl phosphonium, ethyl butyl pentyl heptyl phosphonium, ethyl butyl pentyl octyl phosphonium, ethyl butyl dihexyl phosphonium, ethyl butyl hexyl heptyl Suphonium, ethyl butyl hexyl octyl phosphonium, ethyl butyl heptyl octyl phosphonium, ethyl butyl dioctyl phosphonium, ethyl tripentyl phosphonium, ethyl dipentyl hexyl phosphonium, ethyl dipentyl heptyl phosphonium, ethyl dipentyl octyl phosphonium, ethyl pentyl dihexyl phosphonium, ethyl pentyl hexyl heptyl phosphonium, Ethylpentylhexyloctylphosphonium, ethylpentyldiheptylphosphonium, ethylpentylheptyloctylphosphonium, ethylpentyldioctylphosphonium, ethyltrihexylphosphonium, ethyldihexylheptylphosphonium, ethyldihexyloctylphosphonium, ethylhexyldiheptylphosphoni Ethyl hexyl heptyl octyl phosphonium, ethyl hexyl dioctyl phosphonium, ethyl triheptyl phosphonium, ethyl diheptyl octyl phosphonium, ethyl heptyl dioctyl phosphonium, ethyl trioctyl phosphonium, tripropyl butyl phosphonium, tripropylpentyl phosphonium, tripropyl hexyl phosphonium, tripropyl heptyl Phosphonium, tripropyloctylphosphonium, dipropyldibutylphosphonium, dipropylbutylpentylphosphonium, dipropylbutylhexylphosphonium, dipropylbutylheptylphosphonium, dipropylbutyloctylphosphonium, dipropyldipentylphosphonium, dipropylpentylhexylphosphonium, dipropylpen Tilheptylphosphonium, dipropylpentyloctylphosphonium, dipropyldihexylphosphonium, dipropylhexylheptylphosphonium, dipropylhexyloctylphosphonium, dipropyldiheptylphosphonium, dipropylheptyloctylphosphonium, dipropyldioctylphosphonium, propyltributylphosphonium, propyldibutyl Pentyl phosphonium, propyl dibutyl hexyl phosphonium, propyl dibutyl heptyl phosphonium, propyl dibutyl octyl phosphonium, propyl butyl dipentyl phosphonium, propyl butyl pentyl hexyl phosphonium, propyl butyl pentyl heptyl phosphonium, propyl butyl pentyl octyl phosphonium, propyl butyl diheptyl Suphonium, propylbutylheptyloctylphosphonium, propylbutyldioctylphosphonium, propyltripentylphosphonium, propyldipentylhexylphosphonium, propyldipentylheptylphosphonium, propyldipentylhexylphosphonium, propylpentylhexylheptylphosphonium, propylpentylhexyloctylphosphonium, propylpentyldiheptyl Phosphonium, propylpentylheptyloctylphosphonium, propylpentyldioctylphosphonium, propyltrihexylphosphonium, propyldihexylheptylphosphonium, propyldihexyloctylphosphonium, propylhexyldiheptylphosphonium, propylhexylheptyloctylphosphonium , Propylhexyl dioctyl phosphonium, propyl triheptyl phosphonium, propyl diheptyl octyl phosphonium, propyl heptyl dioctyl phosphonium, propyl trioctyl phosphonium, tetrabutyl phosphonium, tributyl pentyl phosphonium, tributyl hexyl phosphonium, tributyl heptyl phosphonium, tributyl octyl phosphonium, tetrapentyl phosphonium , Tripentylhexylphosphonium, tripentylheptylphosphonium, tripentyloctylphosphonium, tetrahexylphosphonium, trihexylheptylphosphonium, trihexyloctylphosphonium, tetraheptylphosphonium, triheptyloctylphosphonium, tetraoctylphosphonium, etc., or Cation of compounds in which one or more hydrogen atoms in these alkyl groups are substituted with fluorine atoms, triethylallylphosphonium, triethylbutenylphosphonium, tripropylallylphosphonium, tripropylbutenylphosphonium, tributylallylphosphonium, tributylbutenyl Examples include phosphonium, triethylmethoxyethylphosphonium, triethylmethoxyethoxyethylphosphonium, tripropylmethoxyethylphosphonium, tripropylmethoxyethoxyethylphosphonium, tributylmethoxyethylphosphonium, tributylmethoxyethoxyethylphosphonium, and the like.

Also these PR ¹ ₄ in the fluorosulfonic acid salt with a cation structure, fluorosulfonic acid tetramethyl phosphonium, fluorosulfonic acid tetraethyl phosphonium, fluoro sulfonic acid tetrabutylphosphonium, particularly preferred from the viewpoint of ease of availability and handling .
The method for synthesizing and obtaining the fluorosulfonate represented by the general formula (1) used in the non-aqueous electrolyte solution according to the present invention is not particularly limited, and any method may be used. Or even obtained ones can be used.

Examples of the method for synthesizing a metal salt of fluorosulfonic acid represented by the general formula (1) include a method of obtaining a metal salt of fluorosulfonic acid by reacting a metal fluoride or a metal fluoride silicon compound with SO3, A method of obtaining a metal salt of fluorosulfonic acid by reacting a sulfonic acid and a metal by ion exchange, a method of obtaining a metal salt of fluorosulfonic acid by reacting an ammonium salt of fluorosulfonic acid and a metal, fluorosulfonic acid and acetic acid And a method of obtaining a metal salt of fluorosulfonic acid by reacting with the metal salt and ion-exchanged, and a method of obtaining a metal salt of fluorosulfonic acid by reacting fluorosulfonic acid with a metal halide. In addition, as a method for synthesizing the ammonium salt or phosphonium salt of fluorosulfonic acid represented by the general formula (1), a fluorosulfonic acid ester is reacted with a tertiary amine, phosphine, or the like to form a tertiary amine or phosphine. Examples thereof include a method for obtaining a fluorosulfonate by a grading reaction, a method for obtaining an ammonium or phosphonium salt of fluorosulfonic acid by ion exchange of a metal salt of fluorosulfonic acid and a halide of quaternary ammonium or phosphonium salt, and the like. .

  In the non-aqueous electrolyte solution of the present invention, the fluorosulfonate represented by the general formula (1) may be contained in at least one kind, or one kind may be used alone or two or more kinds may be used in combination. May be. When using 2 or more types, it is preferable that one of them is LiFSO3. In particular, LiFSO3, NaFSO3, KFSO3, tetraalkylammonium fluorosulfonate (eg, methylammonium, tetraethylammonium fluorosulfonate, tetrabutylammonium fluorosulfonate), dimethylpyrrolidinium fluorosulfonate, methylethylpyrrolidifluorosulfonate Nitrogen, diethylpyrrolidinium fluorosulfonate, dimethylpiperidinium fluorosulfonate, methylethylpiperidinium fluorosulfonate, diethylpiperidinium fluorosulfonate, dimethylmorpholinium fluorosulfonate, methylethylmorpholine fluorosulfonate Nitrogen, diethylmorpholinium fluorosulfonate, tetramethylphosphonium fluorosulfonate, fluorosulfonate It is preferably a combination of one or more selected from La ethyl phosphonium and fluorosulfonic acid tetrabutylphosphonium.

  Specifically, LiFSO3 and NaFSO3, LiFSO3 and KFSO3, LiFSO3 and tetramethylammonium fluorosulfonate, LiFSO3 and tetraethylammonium fluorosulfonate, LiFSO3 and tetrabutylammonium fluorosulfonate, LiFSO3 and dimethylpyrrolidinium fluorosulfonate, LiFSO3 And methyl ethyl pyrrolidinium fluorosulfonate, LiFSO3 and diethylpyrrolidinium fluorosulfonate, LiFSO3 and dimethylpiperidinium fluorosulfonate, LiFSO3 and methylethylpiperidinium fluorosulfonate, LiFSO3 and diethylpiperidinium fluorosulfonate LiFSO3 and dimethylmorpholinium fluorosulfonate, LiFSO3 and fluorosulfone Combination of methyl ethyl morpholinium phosphate, LiFSO3 and diethylmorpholinium fluorosulfonate, LiFSO3 and tetramethylphosphonium fluorosulfonate, LiFSO3 and tetraethylphosphonium fluorosulfonate, LiFSO3 and tetrabutylphosphonium fluorosulfonate are non-aqueous electrolysis This is preferable in terms of increasing the lithium concentration in the liquid.

  The content of the compound represented by the general formula (1) with respect to the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and still more preferably. It is 0.2% by mass or more, usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. By being in the said range, it suppresses that these compounds exist excessively in electrolyte solution. Moreover, since the compound represented by the general formula (1) is used for the purpose of modifying the interface such as the positive electrode / electrolyte interface, the negative electrode / electrolyte interface, etc. Preferably there is. If an unreacted compound is excessively present in the electrolytic solution, the battery characteristics may be deteriorated.

<1-2. Compound represented by general formula (2)>
The non-aqueous electrolyte solution of the present invention contains a compound represented by the following general formula (2).

(R ² represents a halogen atom or an organic group that may contain a C 1-6 hetero atom, and R ³ represents an organic group that may contain a C 3-12 hetero atom)
In general formula (2), R ² represents a halogen atom, or an organic group which may contain a hetero atom having 1 to 6 carbon atoms.
Specific examples of the halogen atom include a fluorine atom and a chlorine atom, and among them, a fluorine atom is preferable.

As an organic group which may contain a C1-C6 hetero atom, a C1-C6 hydrocarbon group and a C1-C6 organic group containing a hetero atom are mentioned.
Specific examples of the hydrocarbon group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a phenyl group. Among them, a methyl group, an ethyl group, and a phenyl group are preferable, and a methyl group An ethyl group is more preferable, and a methyl group is still more preferable.

Examples of the hetero atom of the organic group having 1 to 6 carbon atoms including a hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom, and among them, a nitrogen atom is preferable. Specific examples of the organic group having 1 to 6 carbon atoms containing a hetero atom include a dimethylamino group and a diethylamino group, and among them, a dimethylamino group is preferable.
Among these, R ² is preferably a fluorine atom, a chlorine atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a phenyl group, a dimethylamino group, or a diethylamino group. And a dimethylamino group are preferred from the viewpoint of increasing the reactivity of the compound represented by the general formula (1).

In general formula (2), R ³ represents an organic group which may contain a hetero atom having 3 to 12 carbon atoms. Examples of the hetero atom of the organic group which may contain a hetero atom having 3 to 12 carbon atoms include a nitrogen atom, an oxygen atom, and a sulfur atom. Among them, an oxygen atom and a sulfur atom are preferable, and an oxygen atom is more preferable.
Specific examples of the organic group that may contain a hetero atom having 3 to 12 carbon atoms include n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, phenyl group, tolyl group, and benzyl. And groups represented by the following structural formulas.

  Among these, an organic group having 3 to 12 carbon atoms having an oxygen atom is preferable, and a group represented by the following structural formula is more preferable.

  The compound represented by the general formula (2) is preferably a compound represented by the following general formula (3).

(R ² represents a halogen atom or an organic group that may contain a C 1-6 hetero atom, and R ⁴ represents a C 1-5 alkylene group that may have a halogen atom. R ⁵ represents (It represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group, an alkynyl group, or an aryl group having 6 to 10 carbon atoms, which may have a halogen atom.)
In Formula (3), R ⁴ represents an alkylene group having 1 to 5 carbon atoms which may have a halogen atom.

Examples of the alkylene group having 1 to 5 carbon atoms which may have a halogen atom include a methylene group, a methylmethylene group, a dimethylmethylene group, and the like, and is preferably a methylmethylene group or a dimethylmethylene group. More preferably.
In Formula (3), R ⁵ represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group, an alkynyl group, or an aryl group having 6 to 10 carbon atoms, which may have a halogen atom.
Among these, it is preferable that it is a C1-C5 alkyl group which may have a halogen atom, As a specific example, a methyl group, an ethyl group, n-propyl group, an isopropyl group etc. are mentioned, Of these, a methyl group and an ethyl group are preferable, a methyl group and an ethyl group are more preferable, and an ethyl group is still more preferable.

  From the above, specific examples of the compound represented by the general formula (2) include those obtained by combining the structures specifically mentioned above, and among them, the compound shown below is the reaction of the compound. It is preferable from the viewpoint of enhancing the properties.

  Among these, the following compounds are more preferable from the viewpoint of increasing the reactivity of the compound.

In addition, R ³ is an organic group containing a hetero atom having 3 to 12 carbon atoms, and examples of the compound containing an oxygen atom and a sulfur atom as the hetero atom include the following compounds, from the viewpoint of increasing the reactivity of the compound. preferable.

  The content of the compound represented by the general formula (2) with respect to the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and still more preferably. It is 0.2% by mass or more, usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and particularly preferably 1% by mass or less. By being in the said range, it suppresses that these compounds exist excessively in electrolyte solution. Moreover, since the compound represented by the general formula (1) is used for the purpose of modifying the interface such as the positive electrode / electrolyte interface, the negative electrode / electrolyte interface, etc. Preferably there is. If an unreacted compound is excessively present in the electrolytic solution, the battery characteristics may be deteriorated.

As a cause of such an improvement effect, the compound represented by the general formula (1) and the compound represented by the general formula (2) in the present invention coexist in the non-aqueous electrolyte solution.
When these compounds react on the positive electrode or the negative electrode, a hybrid film of both is formed, and it is presumed that a more stable and preferable film is formed as compared with conventional individual films. As the effect of the general formula (2) R ³ in the compound represented by is also good organic group optionally containing a hetero atom having from 3 to 12 carbon atoms, when R ³ does not contain a hetero atom Because of the steric hindrance due to the relatively long carbon number, a low resistance film is maintained without the film density becoming too high, and when R ³ contains a hetero atom, the carbon number is relatively long. It is considered that the reactivity of the functional group containing a hetero atom is enhanced and the effect of the compound represented by the general formula (2) can be more effectively exhibited.

<1-2. Electrolyte>
<Lithium salt>
As the electrolyte, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.

For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, inorganic lithium salts LiTaF 6, LiWF ₇ and the like;
Lithium tungstates such as LiWOF ₅ ;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Carboxylic acid lithium salts such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;
_{CH 3 SO 3 Li, CH 2} FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li, CF 3 CF 2 CF 2 SO 3 Li, CF 3 CF 2 CF 2 CF 2 Sulfonic acid lithium salts such as SO ₃ Li;
LiN (FCO) ₂ , LiN (FCO) (FSO ₂ ), LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium imide salts such as lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ;
Lithium metide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ;
Lithium oxalatoborate salts such as lithium difluorooxalatoborate and lithium bis (oxalato) borate;
Lithium oxalate phosphate salts such as lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphate;
In addition, 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 3 C 3} F 7, LiBF 2 (CF 3) 2, LiBF 2 (C 2 F 5) 2, LiBF 2 (CF 3 SO 2) 2, LiBF 2 (C 2 F 5 SO 2) 2 Fluorine-containing organic lithium salts such as;

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN ( _{C 2 F 5 SO 2) 2} , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic _{1,3-perfluoropropanedisulfonylimide, LiC (FSO 2) 3,} LiC (CF 3 SO 2) 3 , LiC (C ₂ F ₅ SO ₂ ) ₃ , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobisoxalatophosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F _{5 , LiPF 3 (CF 3) 3} , LiPF (C ₂ F _{5) 3} or the like is output characteristics and high-rate discharge characteristics, high-temperature storage characteristics, particularly preferred from the viewpoint that an effect of improving the cycle characteristics and the like.

These lithium salts may be used alone or in combination of two or more. A preferable example in the case of using two or more kinds in combination is a combination of LiPF ₆ and LiBF _{4 and the} like, which has an effect of improving load characteristics and cycle characteristics.
In this case, the concentration of LiBF ₄ with respect to 100% by mass of the entire non-aqueous electrolyte solution is not limited in the blending amount and is arbitrary as long as the effects of the present invention are not significantly impaired. 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less.

Another example is the combined use of an inorganic lithium salt and an organic lithium salt, and the combined use of both has the effect of suppressing deterioration due to high-temperature storage. As the organic lithium salt, CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalate phosphate, lithium difluorobisoxalatophosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ LiPF ₃ (C ₂ F ₅ ) ₃ or the like is preferable. In this case, the ratio of the organic lithium salt to 100% by mass of the entire non-aqueous electrolyte is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and preferably 30% by mass or less. Especially preferably, it is 20 mass% or less.

The concentration of these lithium salts in the non-aqueous electrolyte solution is not particularly limited as long as the effects of the present invention are not impaired. Therefore, the total molar concentration of lithium in the non-aqueous electrolyte is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and further preferably 0.5 mol / L or more. Preferably it is 3 mol / L or less, More preferably, it is 2.5 mol / L or less, More preferably, it is 2.0 mol / L or less.
If the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, resulting in decreased battery performance. There is a case.

<1-3. Nonaqueous solvent>
There is no restriction | limiting in particular about the nonaqueous solvent in this invention, It is possible to use a well-known organic solvent. Examples thereof include cyclic carbonates having no fluorine atom, chain carbonates, cyclic and chain carboxylic acid esters, ether compounds, sulfone compounds, and the like.

<Cyclic carbonate not having fluorine atoms>
Examples of the cyclic carbonate having no fluorine atom include cyclic carbonates having an alkylene group having 2 to 4 carbon atoms.
Specific examples of the cyclic carbonate having an alkylene group having 2 to 4 carbon atoms and having no fluorine atom include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

The cyclic carbonate which does not have a fluorine atom may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
The blending amount of the cyclic carbonate not having a fluorine atom is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. However, the blending amount when one kind is used alone is 100 volumes of a non-aqueous solvent. %, 5% by volume or more, more preferably 10% by volume or more. By setting this range, the decrease in electrical conductivity due to the decrease in the dielectric constant of the non-aqueous electrolyte is avoided, and the high current discharge characteristics, stability against the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery are in a good range. And it will be easier. Moreover, it is 95 volume% or less, More preferably, it is 90 volume% or less, More preferably, it is 85 volume% or less. By setting it as this range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, the decrease in ionic conductivity is suppressed, and the load characteristics of the non-aqueous electrolyte battery are easily set in a favorable range.

<Chain carbonate>
As the chain carbonate, a chain carbonate having 3 to 7 carbon atoms is preferable, and a dialkyl carbonate having 3 to 7 carbon atoms is more preferable.
Specific examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl. Examples include carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate, and the like.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
Further, chain carbonates having a fluorine atom (hereinafter sometimes referred to as “fluorinated chain carbonate”) can also be suitably used.

The number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons.
Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate and derivatives thereof, fluorinated ethyl methyl carbonate and derivatives thereof, and fluorinated diethyl carbonate and derivatives thereof.

Fluorinated dimethyl carbonate and derivatives thereof include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate, and the like. It is done.
Fluorinated ethyl methyl carbonate and derivatives thereof 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, etc. are mentioned.

Fluorinated diethyl carbonate and its 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, Examples include 2,2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.

A chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The amount of the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, the decrease in ionic conductivity is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte battery are easily set in a favorable range. Further, the chain carbonate is preferably 90% by volume or less, more preferably 85% by volume or less, in 100% by volume of the nonaqueous solvent. By setting the upper limit in this way, it is easy to avoid a decrease in electrical conductivity resulting from a decrease in dielectric constant of the nonaqueous electrolyte solution, and to make the large current discharge characteristics of the nonaqueous electrolyte solution battery in a favorable range.

<Cyclic carboxylic acid ester>
The cyclic carboxylic acid ester is preferably one having 3 to 12 carbon atoms.
Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

A cyclic carboxylic acid ester may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The amount of the cyclic carboxylic acid ester is usually 5% by volume or more, more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent. If it is this range, it will become easy to improve the electrical conductivity of a non-aqueous electrolyte solution, and to improve the large current discharge characteristic of a non-aqueous electrolyte battery. Moreover, the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 50 volume% or less, More preferably, it is 40 volume% or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and a large current discharge of the non-aqueous electrolyte secondary battery is performed. It becomes easy to make a characteristic into a favorable range.

<Chain carboxylic acid ester>
The chain carboxylic acid ester is preferably one having 3 to 7 carbon atoms. Specifically, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl acetate-n-butyl acetate, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improvement of ionic conductivity.
A chain carboxylic acid ester may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The amount of the chain carboxylic acid ester is usually 10% by volume or more, more preferably 15% by volume or more, in 100% by volume of the nonaqueous solvent. By setting the lower limit in this way, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte battery are easily improved. The amount of the chain carboxylic acid ester is preferably 60% by volume or less, more preferably 50% by volume or less in 100% by volume of the non-aqueous solvent. By setting the upper limit in this way, an increase in negative electrode resistance is suppressed, and the large current discharge characteristics and cycle characteristics of the non-aqueous electrolyte battery are easily set in a favorable range.

<Ether compound>
As the ether compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms in which part of hydrogen may be substituted with fluorine is preferable.
As the chain ether having 3 to 10 carbon atoms,
Diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2, 2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2-trifluoroethyl) ether, (2-fluoroethyl) ) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, ethyl-n-propyl ether, ethyl (3-Fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n-propyl) ether, ethyl (2,2,3,3-teto Fluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propylether, (2-fluoroethyl) (3-fluoro- n-propyl) ether, (2-fluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) Ether, (2-fluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, 2,2,2-trifluoroethyl-n-propyl ether, (2,2,2- (Trifluoroethyl) (3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2, , 2-trifluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3,3-pentafluoro- n-propyl) ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl) (3-fluoro-n-propyl) ether, (1, 1,2,2-tetrafluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3-tetrafluoro -N-propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-propyl ether, (n- Propyl) (3-fluoro (Ro-n-propyl) ether, (n-propyl) (3,3,3-trifluoro-n-propyl) ether, (n-propyl) (2,2,3,3-tetrafluoro-n-propyl) Ether, (n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3-fluoro-n-propyl) ether, (3-fluoro-n-propyl) (3 , 3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3,3,3-trifluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) ether ) (2, 2, 3, 3- Trifluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (2,2,3) , 3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di ( 2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy (2-fluoroethoxy) methane, methoxy (2,2,2-tri Fluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fluoroethoxy) methane, ethoxy (2,2 2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, di (2-fluoroethoxy) methane, (2-fluoroethoxy) (2,2,2-trifluoroethoxy) Methane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2,2-trifluoroethoxy) (1,1 , 2,2-tetrafluoroethoxy) methane, di (1,1,2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) ethane, methoxy (2,2,2 -Trifluoroethoxy) ethane, methoxy (1,1,2,2-tetrafluoroethoxy) ethane, diethoxyethane, ethoxy Ci (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoroethoxy) ethane, ethoxy (1,1,2,2-tetrafluoroethoxy) ethane, di (2-fluoroethoxy) ethane, (2 -Fluoroethoxy) (2,2,2-trifluoroethoxy) ethane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (2,2,2-trifluoroethoxy) Ethane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (1,1,2,2-tetrafluoroethoxy) ethane, ethylene glycol di-n- Examples include propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.

Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve ion dissociation. Of these, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable because they have low viscosity and give high ionic conductivity.

An ether type compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The compounding amount of the ether compound is usually in 100% by volume of the non-aqueous solvent, preferably 5% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, and preferably 70% by volume or less. More preferably, it is 60 volume% or less, More preferably, it is 50 volume% or less.
If it is this range, it is easy to ensure the improvement effect of the lithium ion dissociation degree of chain ether, and the improvement of the ionic conductivity derived from a viscosity fall. It is easy to avoid a situation where the capacity is reduced due to co-insertion.

<Sulfone compound>
As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.
As cyclic sulfone having 3 to 6 carbon atoms,
Monosulfone compounds trimethylene sulfones, tetramethylene sulfones, hexamethylene sulfones;
Examples include disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones.

Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.
As the sulfolanes, sulfolane and / or sulfolane derivatives (hereinafter sometimes referred to as “sulfolanes” including sulfolane) are preferable. The sulfolane derivative is preferably one in which one or more hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.

  Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methyl Sulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro Methyl sulfolane, 2- Trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4-fluoro-3- (trifluoromethyl) sulfolane , 5-fluoro-3- (trifluoromethyl) sulfolane and the like are preferable in terms of high ionic conductivity and high input / output characteristics.

In addition, as the chain sulfone having 2 to 6 carbon atoms,
Dimethylsulfone, ethylmethylsulfone, diethylsulfone, n-propylmethylsulfone, n-propylethylsulfone, di-n-propylsulfone, isopropylmethylsulfone, isopropylethylsulfone, diisopropylsulfone, n-butylmethylsulfone, n-butylethyl Sulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, trifluoroethylmethylsulfone, pentafluoro Ethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perf Oroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di (trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl- n-propylsulfone, fluoromethylisopropylsulfone, difluoromethylisopropylsulfone, trifluoromethylisopropylsulfone, trifluoroethyl-n-propylsulfone, trifluoroethylisopropylsulfone, pentafluoroethyl-n-propylsulfone, pentafluoroethylisopropylsulfone , Trifluoroethyl-n-butylsulfone, trifluoroethyl-t-butylsulfone, pentafluoroethyl- - butyl sulfone, pentafluoroethyl -t- butyl sulfone, and the like.

Among them, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone , Monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoro Ethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, tri Ruoroechiru -n- butyl sulfone, trifluoroethyl -t- butyl sulfone, trifluoromethyl -n- butyl sulfone, trifluoromethyl -t- butyl sulfone is high ion conductivity, preferable because the input-output characteristic is high.

A sulfone compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The compounding amount of the sulfone compound is usually 0.3% by volume or more, more preferably 1% by volume or more, further preferably 5% by volume or more in 100% by volume of the nonaqueous solvent, and preferably 40%. Volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 30 volume% or less.
Within this range, durability improvement effects such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte can be set to an appropriate range to avoid a decrease in electrical conductivity. When charging / discharging an aqueous electrolyte battery at a high current density, it is easy to avoid a situation in which the charge / discharge capacity retention rate decreases.

<When using a cyclic carbonate having a fluorine atom as a non-aqueous solvent>
In the present invention, when a cyclic carbonate having a fluorine atom is used as a non-aqueous solvent, as the non-aqueous solvent other than the cyclic carbonate having a fluorine atom, one of the exemplified non-aqueous solvents is combined with the cyclic carbonate having a fluorine atom. Two or more kinds may be used in combination with a cyclic carbonate having a fluorine atom.

  For example, one preferred combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having a fluorine atom and a chain carbonate. Among them, the total of the cyclic carbonate having a fluorine atom and the chain carbonate in the non-aqueous solvent is preferably 60% by volume or more, more preferably 80% by volume or more, and further preferably 90% by volume or more, and the fluorine atom. The ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a chain and the chain carbonate is 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more. Further, it is preferably 60% by volume or less, more preferably 50% by volume or less, still more preferably 40% by volume or less, and particularly preferably 35% by volume or less.

When a combination of these non-aqueous solvents is used, the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent may be improved.
For example, as a specific example of a preferable combination of a cyclic carbonate having a fluorine atom and a chain carbonate,
Monofluoroethylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and diethyl carbonate, monofluoroethylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, monofluoro Examples thereof include ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

Among the combinations of cyclic carbonates having a fluorine atom and chain carbonates, those containing symmetric chain alkyl carbonates as chain carbonates are more preferable, and in particular, monofluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, Cycle characteristics include monofluoroethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates such as fluoroethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. And a large current discharge characteristic are preferable. Among these, the symmetric chain carbonate is preferably dimethyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.

  A combination in which a cyclic carbonate not having a fluorine atom is further added to the combination of the cyclic carbonate having a fluorine atom and the chain carbonate is also a preferable combination. Among them, the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom in the non-aqueous solvent is preferably 10% by volume or more, more preferably 15% by volume or more, and further preferably 20% by volume or more. The ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom is 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume. % Or more, more preferably 25% by volume or more, preferably 95% by volume or less, more preferably 85% by volume or less, still more preferably 75% by volume or less, and particularly preferably 60% by volume or less.

When the cyclic carbonate which does not have a fluorine atom is contained in this concentration range, the electrical conductivity of the electrolytic solution can be maintained while forming a stable protective film on the negative electrode.
As a specific example of a preferable combination of a cyclic carbonate having a fluorine atom and a cyclic carbonate having no fluorine atom and a chain carbonate,
Monofluoroethylene carbonate and ethylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and ethylene carbonate and diethyl carbonate, monofluoroethylene carbonate and ethylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and ethylene carbonate, dimethyl carbonate and diethyl carbonate, monofluoro Ethylene carbonate, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate Monofluoroethylene carbonate and propylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and propylene carbonate and diethyl carbonate, monofluoroethylene carbonate and propylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and propylene carbonate, dimethyl carbonate and diethyl carbonate, Monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate Tylmethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, monofluoroethylene Carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate and propylene carbonate Examples include diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

Among the combinations of a cyclic carbonate having a fluorine atom and a cyclic carbonate having no fluorine atom and a chain carbonate, those containing a symmetric chain alkyl carbonate as the chain carbonate are more preferred,
Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoro Ethylene carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate Nate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, and dimethyl carbonate It is preferable to use monofluoroethylene carbonate, symmetric chain carbonates, and asymmetric chain carbonates such as sodium carbonate, diethyl carbonate, and ethyl methyl carbonate because the balance between cycle characteristics and large current discharge characteristics is good. Among these, the symmetric chain carbonate is preferably dimethyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.

  When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. Preferably, the content is 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, still more preferably 75% by volume or less, and particularly preferably 70% by volume or less. The load characteristics may be improved.

Above all, it contains dimethyl carbonate and ethyl methyl carbonate, and by increasing the content ratio of dimethyl carbonate over the content ratio of ethyl methyl carbonate, the electric conductivity of the electrolyte can be maintained, but the battery characteristics after high temperature storage are improved. Therefore, it is preferable.
The volume ratio of dimethyl carbonate to ethyl methyl carbonate in all non-aqueous solvents (dimethyl carbonate / ethyl methyl carbonate) is 1.1 or more in terms of improving the electric conductivity of the electrolyte and improving the battery characteristics after storage. Is preferable, 1.5 or more is more preferable, and 2.5 or more is more preferable.

The volume ratio (dimethyl carbonate / ethyl methyl carbonate) is preferably 40 or less, more preferably 20 or less, still more preferably 10 or less, and particularly preferably 8 or less, from the viewpoint of improving battery characteristics at low temperatures.
In the combination mainly composed of the cyclic carbonate having a fluorine atom and the chain carbonate, in addition to the cyclic carbonate having no fluorine atom, a cyclic carboxylic acid ester, a chain carboxylic acid ester, a cyclic ether, Other solvents such as chain ethers, sulfur-containing organic solvents, phosphorus-containing organic solvents, and fluorine-containing aromatic solvents may be mixed.

<When using a cyclic carbonate having a fluorine atom as an auxiliary agent>
In the present invention, when a cyclic carbonate having a fluorine atom is used as an auxiliary agent, as the non-aqueous solvent other than the cyclic carbonate having a fluorine atom, one of the exemplified non-aqueous solvents may be used alone, or two or more thereof. May be used in any combination and ratio.
For example, one preferred combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having no fluorine atom and a chain carbonate.

  Among them, the total of cyclic carbonate and chain carbonate having no fluorine atom in the non-aqueous solvent is preferably 70% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more, The ratio of the cyclic carbonate having no fluorine atom to the total of the cyclic carbonate and the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more. Preferably it is 50 volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 30 volume% or less, Most preferably, it is 25 volume% or less.

When a combination of these non-aqueous solvents is used, the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent may be improved.
For example, as a specific example of a preferable combination of a cyclic carbonate having no fluorine atom and a chain carbonate,
Ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate And dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

  Among the combinations of cyclic carbonates and chain carbonates not having a fluorine atom, those containing asymmetric chain alkyl carbonates as chain carbonates are more preferable, in particular, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Those containing ethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates such as ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate have cycle characteristics and large current discharge characteristics. This is preferable because of a good balance.

Among them, the asymmetric chain carbonate is preferably ethyl methyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.
A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination.
In the case of containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Further, the proportion of propylene carbonate in the whole non-aqueous solvent is preferably 0.1% by volume or more, more preferably 1% by volume or more, further preferably 2% by volume or more, and preferably 20% by volume or less, more preferably Is 8% by volume or less, more preferably 5% by volume or less.

It is preferable to contain propylene carbonate in this concentration range because the low temperature characteristics may be further improved while maintaining the combination characteristics of ethylene carbonate and chain carbonate.
When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. Preferably it is 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, further preferably 75% by volume or less, and particularly preferably 70% by volume or less. The load characteristics of the battery may be improved.

Above all, it contains dimethyl carbonate and ethyl methyl carbonate, and by increasing the content ratio of dimethyl carbonate over the content ratio of ethyl methyl carbonate, the electric conductivity of the electrolyte can be maintained, but the battery characteristics after high temperature storage are improved. This is preferable.
The volume ratio of dimethyl carbonate to ethyl methyl carbonate in all non-aqueous solvents (dimethyl carbonate / ethyl methyl carbonate) is 1.1 or more in terms of improving the electric conductivity of the electrolyte and improving the battery characteristics after storage. Is preferable, 1.5 or more is more preferable, and 2.5 or more is more preferable. The volume ratio (dimethyl carbonate / ethyl methyl carbonate) is preferably 40 or less, more preferably 20 or less, still more preferably 10 or less, and particularly preferably 8 or less, from the viewpoint of improving battery characteristics at low temperatures.

In the combination mainly composed of a cyclic carbonate having no fluorine atom and a chain carbonate, a cyclic carboxylic acid ester, a chain carboxylic acid ester, a cyclic ether, a chain ether, a sulfur-containing organic solvent, You may mix other solvents, such as a phosphorus organic solvent and an aromatic fluorine-containing solvent.
In this specification, the volume of the non-aqueous solvent is a measured value at 25 ° C., but the measured value at the melting point is used for a solid at 25 ° C. such as ethylene carbonate.

<1-4. Auxiliary>
In the non-aqueous electrolyte battery of the present invention, an auxiliary agent may be appropriately used depending on the purpose. Examples of the auxiliary agent include unsaturated carbonates, unsaturated cyclic carbonates having fluorine atoms, overcharge inhibitors, and other auxiliary agents shown below.

<Unsaturated carbonate>
Among the specific carbonates according to the present invention, as a carbonate having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated carbonate”), a carbon-carbon such as a carbon-carbon double bond or a carbon-carbon triple bond is used. There is no other limitation as long as it is a carbonate having an unsaturated bond, and any unsaturated carbonate 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 unsaturated carbonates include vinylene carbonate derivatives, ethylene carbonate derivatives 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 the vinylene carbonate derivatives 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 the ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate. Etc.
Specific examples of 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 and allyl methyl carbonate.
Among these unsaturated carbonates, as the specific carbonate, vinylene carbonate derivatives, ethylene derivatives 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, and vinyl ethylene carbonate are more preferably used because they form a stable interface protective film.

<Fluorinated unsaturated cyclic carbonate>
As the fluorinated cyclic carbonate, it is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes referred to as “fluorinated unsaturated cyclic carbonate”). The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the fluorine atom is usually 6 or less, preferably 4 or less, and most preferably 1 or 2.

Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon double bond.
Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

As the fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond,
4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene Carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fu Oro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate.

Among these, as a particularly preferred fluorinated unsaturated cyclic carbonate,
4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro- 4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate 4,5-difluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-diallyl ethylene carbonate, because it forms a stable interface protective coating, more preferably used.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed.
The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Moreover, the compounding quantity of a fluorinated unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary.
The compounding amount of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, in 100% by mass of the nonaqueous electrolytic solution. Moreover, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less.
Within this range, the non-aqueous electrolyte battery tends to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics deteriorate, the amount of gas generated increases, and the discharge capacity maintenance ratio decreases. Easy to avoid.

<Overcharge prevention agent>
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively prevent the battery from bursting or igniting when the non-aqueous electrolyte battery is overcharged.

As an overcharge prevention agent,
Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p A partially fluorinated product of the aromatic compound such as cyclohexylfluorobenzene;
Examples thereof include fluorine-containing anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole. Above all,
Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferred.

  These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge preventing property and a high temperature storage property. From the standpoint of balance.

The amount of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The overcharge inhibitor is preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. If it is this range, it will be easy to fully express the effect of an overcharge inhibiting agent, and it will be easy to avoid the situation where the characteristics of batteries, such as a high temperature storage characteristic, fall.
The overcharge inhibitor is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, still more preferably. Is 2% by mass or less.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. As other auxiliaries,
Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride Carboxylic acid anhydrides such as cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride;
Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane;
Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, etc. Sulfur-containing compounds;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide;
Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane;
Fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride;
Etc. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

The blending amount of other auxiliary agents is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Within this range, the effects of other auxiliaries can be sufficiently exhibited, and it is easy to avoid a situation in which battery characteristics such as high-load discharge characteristics deteriorate.
The blending amount of other auxiliaries is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and further preferably 1% by mass or less. .

As mentioned above, what exists in the inside of the non-aqueous electrolyte battery as described in this invention is also contained in the above-mentioned non-aqueous electrolyte.
Specifically, the components of the non-aqueous electrolyte solution such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte solution is prepared from what is substantially isolated by the method described below. In the case of a nonaqueous electrolyte solution in a nonaqueous electrolyte battery obtained by pouring into a separately assembled battery, the components of the nonaqueous electrolyte solution of the present invention are individually placed in the battery, In order to obtain the same composition as the non-aqueous electrolyte solution of the present invention by mixing in a non-aqueous electrolyte battery, the compound constituting the non-aqueous electrolyte solution of the present invention is further generated in the non-aqueous electrolyte battery. The case where the same composition as the aqueous electrolyte is obtained is also included.

[2. Non-aqueous electrolyte secondary battery]
<2-1. Non-aqueous electrolyte>
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix | blend and use other nonaqueous electrolyte solutions with respect to the nonaqueous electrolyte solution of this invention.

<2-2. Positive electrode>
The positive electrode active material (lithium transition metal compound) used for the positive electrode is described below.
<Lithium transition metal compound>
A lithium transition metal compound is a compound having a structure capable of desorbing and inserting lithium ions. For example, sulfide, phosphate compound, silicic acid compound, boric acid compound, lithium transition metal composite oxidation Thing etc. are mentioned. Examples of sulfides include compounds having a two-dimensional layered structure such as TiS ₂ and MoS ₂ , and solid compounds represented by the general formula M _x Mo ₆ S ₈ (M is various transition metals including Pb, Ag, and Cu). Examples thereof include a chevrel compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMPO ₄ (M is at least one transition metal), specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO _4, and the like. Examples of the silicic acid compound include LiMSiO ₄ , and examples of the boric acid compound include LiMBO ₄ . Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiM ₂ O ₄ (M is at least one transition metal), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like. Those having a layered structure are generally expressed as LiMO ₂ (M is at least one transition metal). LiCoO _{2 Specifically, LiNiO 2, LiNi 1-x} Co x O 2, LiNi 1-x-y Co x Mn y O 2, LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0. _{4 Mn 0.4 O 2, Li 1.2} Cr 0.4 Ti 0.4 O 2, LiMnO 2 , and the like.

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

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

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

M is at least one metallic element average oxidation number of 4 ^+, specifically, at least one metal element Mn, Zr, Ti, Ru, selected from the group consisting of Re and Pt.
M 'is at least one metallic element average oxidation number of 3 ^+, preferably, V, Mn, Fe, at least one metallic element selected from the group consisting of Co and Ni,
More preferably, it is at least one metal element selected from the group consisting of Mn, Co and Ni.
2) A lithium transition metal compound represented by the following general formula (B).
_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)
However, M is an element comprised from at least 1 sort (s) of the transition metals chosen from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg.

The value of b is usually 0.4 or more and 0.6 or less.
If the value of b is this range, the energy density per unit mass in a lithium transition metal type compound will be high.
The value of a is usually 0 or more and 0.3 or less. Moreover, a in the said composition formula is the preparation composition in the manufacture stage of a lithium transition metal type compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, a may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

When the value of a is within this range, the energy density per unit mass in the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.
Furthermore, the value of δ is usually in the range of ± 0.5.
If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are good.

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

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

Specific examples of the lithium transition metal compound having the above composition include, for example, Li _{1 + x} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + x} Ni _0.85 Co _0.10 Al _0.05 O ₂ , Li _{1 + x} Ni _0.33 Mn _0.33 Co _0.33 O ₂ , Li _{1 + x} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + x} Mn _1.8 Al _0.2 O ₄ , Li _{1 + x} Mn _1.5 Ni _0.5 O ₄ and the like. These lithium transition metal compounds may be used alone or in a blend of two or more.

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

<Surface coating>
Moreover, you may use what the substance of the composition different from this adhered to the surface of the said positive electrode active material. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

  For example, these surface adhering substances are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, and dried. After the surface adhering substance precursor is dissolved or suspended in a solvent and added to the positive electrode active material, It can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

The amount of the surface adhering substance is by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably, as the lower limit. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material, and can improve the battery life. Within the above range, the resistance associated with the inhibition of the entry and exit of lithium ions can be suppressed, while the effect can be sufficiently exhibited.
In the present invention, a material in which a material having a different composition is attached to the surface of the positive electrode active material is also referred to as “positive electrode active material”.

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

<Tap density>
The tap density of the positive electrode active material is preferably 0.5 g / cm ³ or more, more preferably 1.0 g / cm ³ or more, still more preferably 1.5 g / cm ³ or more, and most preferably 1.7 g / cm ³ or more. It is. When the tap density of the positive electrode active material is within the above range, it is possible to suppress the amount of the dispersion medium and the necessary amount of conductive material and binder required when forming the positive electrode active material layer. Capacity can be secured. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as high as possible, and there is no particular upper limit, but it is preferably 2.8 g / cm ³ or less, more preferably 2.7 g / cm ³ or less, and even more preferably 2.5 g / cm ³ or less. When it is within the above range, it is possible to suppress a decrease in load characteristics.
In the present invention, the tap density is defined as the powder packing density (tap density) g / cc when 5 to 10 g of the positive electrode active material powder is put in a 10 ml glass measuring cylinder and tapped 200 times with a stroke of about 20 mm. Ask.

<Median diameter d50>
The median diameter d50 of the positive electrode active material particles (secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 1.2 μm or more, and even more preferably. Is 1.5 μm or more, most preferably 2 μm or more, and the upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, and most preferably 15 μm or less. Within the above range, a high tap density product can be obtained and battery performance degradation can be suppressed. On the other hand, when forming a positive electrode for a battery, that is, when an active material, a conductive material, a binder, etc. are slurried with a solvent and applied in a thin film form It is possible to prevent problems such as drawing streaks. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d50, it is possible to further improve the filling property when forming the positive electrode.
In the present invention, the median diameter d50 is measured by a known laser diffraction / scattering particle size distribution measuring device. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

<Average primary particle size>
When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.8 μm. The upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, and most preferably 1 μm or less. When it is in the above range, powder filling property and specific surface area can be secured and deterioration of battery performance can be suppressed, while reversibility of charge and discharge can be secured by obtaining appropriate crystallinity. .
In the present invention, the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

<Average secondary particle size>
Further, the average secondary particle size of the positive electrode active material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.2 μm or more, preferably 0.3 μm or more, and usually 20 μm or less, preferably 10 μm or less. It is. If the average secondary particle size is too small, the cycle deterioration of the lithium secondary battery may be increased and handling may be difficult. If the average secondary particle size is too large, the internal resistance of the battery may be increased and output may be difficult to output.

<BET specific surface area>
The BET specific surface area of the positive electrode active material is preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more, further preferably 0.5 m ² / g or more, and most preferably 0.6 m ² / g. The upper limit is 50 m ² / g or less, preferably 40 m ² / g or less, more preferably 30 m ² / g or less. When the BET specific surface area is in the above range, the battery performance can be secured and the applicability of the positive electrode active material can be kept good.
In the present invention, the BET specific surface area is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 150 ° C. for 30 minutes under nitrogen flow, and then atmospheric pressure. This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to 0.3 is 0.3.

<Method for producing positive electrode active material>
Although it does not restrict | limit especially as a manufacturing method of a positive electrode active material in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.

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.

<Blend>
In addition, these positive electrode active materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

<Composition and manufacturing method of positive electrode>
The structure of the positive electrode will be described below. In the present invention, the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry. Further, for example, the positive electrode active material described above may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.
Hereinafter, a case where the slurry is applied to the positive electrode current collector and dried will be described.

<Active material content>
The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. The upper limit is preferably 98% by mass or less, more preferably 95% by mass or less, and particularly preferably 93% by mass or less. Within the above range, the electric capacity of the positive electrode active material in the positive electrode active material layer can be secured, and the strength of the positive electrode can be maintained.

The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1.5 g / cm ³ or more as a lower limit, more preferably 2 g / cm ³ , further preferably 2.2 g / cm ³ or more, and preferably 3.8 g as an upper limit. / Cm ³ or less, more preferably 3.5 g / cm ³ or less, even more preferably 3.0 g / cm ³ or less, and particularly preferably 2.8 g / cm ³ or less. If it exceeds this range, the permeability of the electrolyte solution to the vicinity of the current collector / active material interface decreases, and the charge / discharge characteristics particularly at a high current density decrease, and a high output may not be obtained. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and a high output may not be obtained.

<Conductive material>
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. Sufficient electrical conductivity and battery capacity can be ensured within the above range.

<Binder>
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, the type is not particularly limited as long as it is a material that can be dissolved or dispersed in the liquid medium used during electrode production. However, it is preferable to select in consideration of weather resistance, chemical resistance, heat resistance, flame retardancy, and the like. Specific examples include inorganic compounds such as silicate and water glass, alkane polymers such as polyethylene, polypropylene and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene and polymethylstyrene. , Polymers having rings such as polyvinyl pyridine, poly-N-vinyl pyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, Acrylic derivative polymers such as polyacrylamide; Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; Polyvinyl chloride, halogen-containing polymers of polyvinylidene chloride; polyvinyl alcohol polymers such as polyvinyl alcohol conductive polymer such as polyaniline or the like can be used.

In addition, mixtures of the above-described polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, preferred binders are a fluororesin and a CN group-containing polymer. In addition, a binder may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
When a resin is used as the binder, the mass average molecular weight of the resin is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 10,000 or more, preferably 100,000 or more, and usually 300. 10,000 or less, preferably 1,000,000 or less. If the molecular weight is too low, the strength of the electrode tends to decrease. On the other hand, if the molecular weight is too high, the viscosity becomes high and it may be difficult to form an electrode.

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 ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60%. It is not more than mass%, more preferably not more than 40 mass%, most preferably not more than 10 mass%. Within the above range, the mechanical strength of the positive electrode can be ensured, and deterioration of battery performance such as cycle characteristics can be suppressed, while deterioration of battery capacity and conductivity can be suppressed.

<Slurry forming solvent>
As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent capable of dissolving or dispersing the thickener used as necessary may be used. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran; N-methylpyrrolidone, dimethylformamide and dimethylacetamide Amides such as aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide.

<Thickener>
In particular, when an aqueous medium is used, it is preferable to make a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. When a thickener is further added, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. The upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Within the above range, good coatability can be obtained, and a decrease in battery capacity and an increase in resistance can be suppressed.

<Current collector>
The material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A 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. Although the thickness of the thin film is arbitrary, from the viewpoint of strength and handleability as a current collector, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is usually 1 mm or less, preferably 100 μm or less. More preferably, it is 50 μm or less.

Moreover, it is also preferable from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer that a conductive additive is applied to the surface of the current collector. Examples of the conductive assistant include noble metals such as carbon, gold, platinum, and silver.
Furthermore, in order to improve the binding effect between the current collector and the active material layer formed on the surface, the surface of these current collectors may be roughened in advance. The surface roughening method includes a method such as rolling with a blasting process or a rough roll, a polishing cloth with a fixed abrasive particle, a grinding wheel, emery buff, a wire brush equipped with a steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of the current collector) is 20 The lower limit is preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Within the above range, heat generation of the current collector during high current density charge / discharge can be suppressed, and battery capacity can be secured.

<Electrode area>
When using the non-aqueous electrolyte of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 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. , The sum of the areas where each surface is calculated separately.

<Thickness of positive electrode plate>
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is preferably as a lower limit with respect to one side of the current collector. Is 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 500 μm or less, more preferably 450 μm or less.

<Surface coating of positive electrode plate>
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

<2-3. Negative electrode>
The negative electrode active material used for the negative electrode is not particularly limited as long as it can electrochemically occlude and release metal ions. Specific examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. Among these, it is most preferable to use a carbonaceous material in terms of good cycle characteristics and safety and excellent continuous charge characteristics. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.

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

  As an apparatus used for the spheroidization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and mechanical action such as impact compression, friction, shearing force, etc. on the carbon material introduced inside the rotor by rotating at high speed. And a device for performing the spheroidizing treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the carbon material.

For example, when the spheroidizing treatment is performed using the above-described apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 50 m / sec.
More preferably, the speed is 100 m / second. The treatment can be performed by simply passing a carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is preferable to circulate or stay in the apparatus for 1 minute or longer. More preferred.

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

  (3) As amorphous carbon, amorphous carbon that has been heat-treated at least once in a temperature range (400 to 2200 ° C.) in which no graphitizable carbon precursor such as tar or pitch is used as a raw material. Examples thereof include amorphous carbon particles obtained by heat treatment using particles or a non-graphitizable carbon precursor such as a resin as a raw material.

(4) Carbon-coated graphite can be obtained by mixing natural graphite and / or artificial graphite with a carbon precursor that is an organic compound such as tar, pitch, or resin, and heat-treating it at least once in the range of 400 to 2300 ° C. Examples thereof include a carbon graphite composite in which natural graphite and / or artificial graphite is used as nuclear graphite, and amorphous carbon coats the nuclear graphite. The composite form may be the whole or part of the surface coated, or a composite of a plurality of primary particles using carbon originating from the carbon precursor as a binder. Carbon can also be deposited (CVD) by reacting natural graphite and / or artificial graphite with hydrocarbon gases such as benzene, toluene, methane, propane, and aromatic volatiles at a high temperature to deposit carbon on the graphite surface. A graphite composite can also be obtained.

  (5) As graphite-coated graphite, natural graphite and / or artificial graphite and a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin are mixed and once in a range of about 2400 to 3200 ° C. Examples thereof include graphite-coated graphite in which natural graphite and / or artificial graphite obtained by heat treatment is used as nuclear graphite, and graphitized material covers the entire surface or a part of the nuclear graphite.

  (6) As the resin-coated graphite, natural graphite and / or artificial graphite obtained by mixing natural graphite and / or artificial graphite with a resin and drying at a temperature of less than 400 ° C. is used as nuclear graphite, and the resin is nuclear graphite. And resin-coated graphite covering the surface.

Moreover, the carbonaceous material of (1)-(6) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
Examples of organic compounds such as tar, pitch and resin used in the above (2) to (5) include coal-based heavy oil, direct-current heavy oil, cracked heavy oil, aromatic hydrocarbon, N-ring compound , S ring compounds, polyphenylene, organic synthetic polymers, natural polymers, organic compounds that can be carbonized selected from the group consisting of thermoplastic resins and thermosetting resins. The raw material organic compound may be used after being dissolved in a low molecular organic solvent in order to adjust the viscosity at the time of mixing.
Moreover, as natural graphite and / or artificial graphite used as a raw material of nuclear graphite, natural graphite subjected to spheroidization treatment is preferable.

<Physical properties of carbonaceous materials>
In addition to the above-described requirements, the carbonaceous material 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 (9). It is particularly preferable to satisfy a plurality of items simultaneously.

(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. It is 360 nm or less, preferably 0.350 nm or less, and more preferably 0.345 nm or less. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, more preferably 1.5 nm or more, especially 2 nm or more. More preferably it is.

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

If the volume reference average particle diameter is in the above range, loss of the initial battery capacity due to the increase in irreversible capacity can be suppressed, and uniform electrode application is possible when the electrode preparation step by application is included.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This can be performed using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(3) Raman R value, Raman half-value width The Raman R value of the carbonaceous material is a value measured by using an argon ion laser Raman spectrum method, usually 0.01 or more, preferably 0.03 or more, 0 .1 or more is more preferable, and is usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.
The Raman R value and the Raman half-value width are indices indicating the crystallinity of the surface of the carbonaceous material. The carbonaceous material has an appropriate crystallinity from the viewpoint of chemical stability, but is an interlayer into which lithium enters by charge / discharge. It is preferable that the crystallinity is such that it does not disappear. In the case where the density of the negative electrode is increased by press after applying to the current collector, it is preferable to take account of this because crystals tend to be oriented in a direction parallel to the electrode plate.

When the Raman R value or the Raman half-value width is in the above range, the reaction between the carbonaceous material and the nonaqueous electrolytic solution can be suppressed, and the deterioration of the load characteristics due to the disappearance of the site can be suppressed.
The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and measuring the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of 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 of the present invention.

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

(4) BET specific surface area of the BET specific surface area carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m @ 2 · ^{g -1} or more, 0.7 m ² · ^{g -1} or more 1.0 m ² · g ⁻¹ or more is more preferable, 1.5 m ² · g ⁻¹ or more is particularly preferable, and usually 100 m ² · g ⁻¹ or less, and 25 m ² · g ⁻¹ or less is preferable. Preferably, 15 m ² · g ⁻¹ or less is more preferable, and 10 m ² · g ⁻¹ or less is particularly preferable.

When the value of the BET specific surface area is within the above range, precipitation of lithium on the electrode surface can be suppressed, while gas generation due to reaction with the non-aqueous electrolyte can be suppressed.
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 of the present invention.

(5) Circularity When the circularity is measured as a spherical degree of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere. The circularity of the particles having a particle size of 3 to 40 μm in the range of the carbonaceous material is desirably closer to 1, and is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more, 0.85 or more is more preferable, and 0.9 or more is particularly preferable.

The greater the degree of circularity of the carbonaceous material, the better the filling property and the resistance between particles, so that the high current density charge / discharge characteristics are improved. Therefore, it is preferable that the circularity is as high as the above range.
The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity determined by the measurement is defined as the circularity of the carbonaceous material of the present invention.

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

(6) Tap density The tap density of the carbonaceous material is usually 0.1 g · cm ⁻³ or more, preferably 0.5 g · cm ⁻³ or more, more preferably 0.7 g · cm ⁻³ or more, and 1 g · cm ⁻³ or more is particularly preferable, 2 g · cm ⁻³ or less is preferable, 1.8 g · cm ⁻³ or less is more preferable, and 1.6 g · cm ⁻³ or less is particularly preferable. When the tap density is in the above range, the battery capacity can be ensured and the increase in resistance between the particles can be suppressed.

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 of the present invention.

(7) Orientation ratio The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is within the above range, excellent high-density charge / discharge characteristics can be ensured. The upper limit of the range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material of 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 = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(8) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. When the aspect ratio is within the above range, streaking at the time of forming an electrode plate is suppressed, and more uniform coating is possible. Therefore, excellent high current density charge / discharge characteristics can be ensured. The lower limit of the range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

The aspect ratio is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Carbonaceous material particles when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A and the shortest diameter B orthogonal thereto are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material of the present invention.

(9) Secondary material mixing 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 properties referred to here are selected from the group consisting 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. Shows more than one characteristic.

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, containing two or more carbonaceous materials having different Raman R values, And X-ray parameters are different.
As an example of the effect of the admixture of secondary materials, carbonaceous material such as graphite (natural graphite, artificial graphite), carbon black such as acetylene black, and amorphous carbon such as needle coke is 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 usually 0.1% by mass or more and 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 45% by mass or less. Yes, 40 mass% or less is preferable. When the mixing ratio is within the above range, the effect of reducing electric resistance can be ensured and an increase in initial irreversible capacity can be suppressed.

<Alloy-based materials>
As an alloy material used as the negative electrode active material, as long as lithium can be occluded / released, lithium alone, simple metals and alloys forming lithium alloys, or oxides, carbides, nitrides, silicides, sulfides thereof Any of compounds such as products or phosphides may be used and is not particularly limited. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably aluminum, silicon and tin (hereinafter referred to as “ Simple metals) and alloys or compounds containing these atoms (sometimes abbreviated as “specific metal elements”). These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

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

  In addition, a compound in which these complex compounds are complexly bonded to several kinds of elements such as a simple metal, an alloy, or a nonmetallic element is also included. 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. 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 may be used. it can.

Among these negative electrode active materials, since the capacity per unit mass is large when a battery is formed, any one simple metal of a specific metal element, an alloy of two or more specific metal elements, oxidation of a specific 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 mass and environmental load.

<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 a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics, A lithium-containing composite metal oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as “lithium titanium composite oxide”) is more 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 non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

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

LixTiyMzO ₄ (A)
[In the general formula (A), 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 (A),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.

A particularly preferred representative composition of the compound is Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.
Although it does not restrict | limit especially as a manufacturing method of lithium titanium complex oxide in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.

For example, a method of obtaining an active material by uniformly mixing a titanium 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.

<Physical properties of lithium titanium composite oxide>
In addition to the above requirements, the lithium titanium composite oxide as the negative electrode active material in the present invention further satisfies at least one of the characteristics such as physical properties and shapes shown in the following (1) to (7). It is preferable to satisfy a plurality of items at the same time.

(1) BET specific surface area As for the BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material, the specific surface area value measured using the BET method is preferably 0.5 m ² · g ⁻¹ or more. 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 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, crystal distortion also occurs, irreversible capacity can not be ignored, it is preferable It may be difficult to obtain a battery.

  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 diameter The volume-based average particle diameter of lithium-titanium composite oxide (secondary particle diameter when primary particles are aggregated to form secondary particles) is determined by 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 it exceeds the above range, 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. When 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, below the above range, there is a case where the performance of the secondary battery is deteriorated, for example, reversibility of charge / discharge is inferior because crystals are underdeveloped.

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

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

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

(5) Tap Density 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 the particles decreases, so that the resistance between the 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 mass of the sample. The tap density calculated by the measurement is defined as the tap density of the lithium titanium composite oxide in the present invention.

(6) Circularity When the circularity is measured as the spherical degree of the lithium titanium composite oxide, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere.

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

<Configuration and production method of negative electrode>
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.
In the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.

<Current collector>
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.

Further, the current collector of the negative electrode may be roughened in advance.
Furthermore, when the current collector is a metal material, examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.
The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less, from the viewpoint of securing battery capacity and handling properties.

(Thickness ratio between current collector and negative electrode active material layer)
The ratio of the thickness of the current collector to the negative electrode active material layer is not particularly limited, but the value of “(the thickness of the negative electrode active material layer on one side immediately before the nonaqueous electrolyte injection) / (thickness of the current collector)” However, 150 or less is preferable, 20 or less is more preferable, 10 or less is particularly preferable, 0.1 or more is preferable, 0.4 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 is within the above range, battery capacity can be secured and heat generation of the current collector during high current density charge / discharge can be suppressed.

<Binder>
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 during electrode production.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or 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 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, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10% by mass or less is further preferable, and 8% by mass or less is particularly 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 a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

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

<Thickener>
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.

  Further, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is within the above range, it is possible to suppress a decrease in battery capacity and an increase in resistance, and it is possible to ensure an appropriate coatability.

<Electrode density>
The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more. but more preferably, particularly preferably 1.3 g · ^{cm -3} or more, preferably 2.2 g · ^{cm -3} or less, more preferably 2.1 g · ^{cm -3} or less, 2.0 g · ^{cm -3} or less Further preferred is 1.9 g · cm ⁻³ or less. When the density of the negative electrode active material present on the current collector is within the above range, the negative electrode active material particles are prevented from being destroyed, and an increase in initial irreversible capacity or to the vicinity of the current collector / negative electrode active material interface. While the deterioration of the high current density charge / discharge characteristics due to the reduced permeability of the non-aqueous electrolyte solution can be suppressed, the decrease in battery capacity and the increase in resistance can be suppressed.

<Thickness of negative electrode plate>
The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. However, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, preferably 20 μm or more. More preferably, it is 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

<Surface coating of negative electrode plate>
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

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

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

<Material>
As materials for the resin and glass fiber separator, for example, polyolefin such as polyethylene and polypropylene, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, polyimide, polyester, polyoxyalkylene, glass filter and the like can be used. Among them, preferred are glass filters and polyolefins, more preferred are polyolefins, and particularly preferred are polyethylene and polypropylene. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Further, the above materials may be laminated.

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

<Porosity>
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 usually 20% or more, preferably 35% or more, more preferably 45% or more, Usually, it is 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

<Average pore size>
The average pore diameter of the separator is also arbitrary, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm 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.

<Inorganic separator>
On the other hand, as the inorganic material, for example, oxides such as alumina, titania 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.

<Form>
As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, 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 a fluorine resin such as PVdF as a binder.

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

<Production method>
Specific examples of the method for obtaining the separator main body and the porous film include the following methods.
(1) A low molecular weight material that is compatible with the polyolefin resin and can be extracted in a later step is added to the polyolefin resin, melt kneaded and formed into a sheet, and the low molecular weight material is extracted after stretching or before stretching. (2) Stretching method in which low-temperature stretching and high-temperature stretching are added to a highly elastic sheet prepared by forming a crystalline resin into a sheet with a high draft ratio to make it porous (3) The thermoplastic resin is inorganic or organic. Interfacial exfoliation method in which filler is added to melt knead and form a sheet, and the interface between the resin and filler is exfoliated by stretching to make it porous. The β crystal nucleating agent method in which the sheet on which the β crystal is formed is stretched and made porous by utilizing the crystal transition, and the manufacturing method is not limited to a wet type or a dry type.

<2-5. Battery design>
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as electrode group occupancy) is usually 40% or more, preferably 50% or more, and usually 90% or less.
80% or less is preferable.

  When the electrode group occupancy falls below the above range, the battery capacity becomes small. In addition, when the above range is exceeded, there are few void spaces, and when the battery becomes high temperature, the member expands or the vapor pressure of the liquid component of the electrolyte increases, so that the internal pressure rises, and the charge / discharge repetition performance as a battery In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

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

<Protective element>
Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element has a design that does not cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body (exterior case). There is no restriction | limiting in this exterior body, A well-known thing can be arbitrarily employ | adopted unless the effect of this invention is impaired remarkably.
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum or an aluminum alloy, a magnesium alloy, nickel, titanium, or a metal, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In the outer case using the metals, a metal is welded together by laser welding, resistance welding, ultrasonic welding to form a sealed sealed structure, or a caulking structure using the metals through a resin gasket To do. Examples of the outer case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve 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.

<Shape>
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.

Hereinafter, the present invention will be described more specifically with reference to examples and reference examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.
[Production of secondary battery]
<Preparation of positive electrode>
Lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 as a positive electrode active material
90 parts by mass of O ₂ ), 7 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride are mixed, and N-methyl-2-pyrrolidone is added to form a slurry, which is uniformly applied to both sides of an aluminum foil having a thickness of 15 μm. After coating and drying so as to be 11.85 mg · cm ⁻² , the positive electrode active material layer was pressed so as to have a density of 2.6 g · cm ⁻³ to obtain a positive electrode.

<Production of negative electrode>
To graphite, an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber of 50% by mass) as a binder are added. The slurry was mixed with a disperser. The obtained slurry was applied uniformly to one side of a copper foil having a thickness of 12 μm so as to be 6.0 mg · cm ⁻² and dried, and then the density of the negative electrode active material layer was 1.36 g · cm ⁻³ . It pressed so that it might become a negative electrode. The graphite used has a d50 value of 10.9 μm, a specific surface area of 3.41 m ² / g, and a tap density of 0.985 g / cm ³ . Further, the slurry was prepared so that the mass ratio of graphite: sodium carboxymethyl cellulose: styrene-butadiene rubber = 97.5: 1.5: 1 was obtained in the negative electrode after drying.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The separator was made of polypropylene, had a thickness of 20 μm, and a porosity of 54%. The battery element thus obtained was wrapped in a cylindrical 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 improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.

[Battery evaluation]
<Initial charge / discharge test>
In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery was charged at 0.05 C for 10 hours, then rested for 3 hours, and then charged at constant current at 0.2 C to 4.1 V. Further, after a rest of 3 hours, constant current-constant voltage charging was performed at 0.2 C to 4.1 V, and then constant current discharging was performed to 3.0 V at 1/3 C. After that, two charging / discharging cycles were carried out, in which 1 / 3C constant current-constant voltage charging up to 4.1V and subsequent 1 / 3C constant current discharging up to 3.0V were taken as one cycle. Furthermore, after charging at a constant current-constant voltage at 1/3 C to 4.1 V, the battery was stored at 60 ° C. for 12 hours to stabilize the battery. Then, the charge / discharge cycle of 1 / 3C constant current-constant voltage charge up to 4.2V at 25 ° C. and subsequent 1 / 3C constant current discharge up to 3.0V was performed. The last discharge capacity at this time was defined as the initial capacity. In addition, 1C is a current value when discharging the entire capacity of the battery in one hour.

<Capacity maintenance rate evaluation test after cycle>
The battery that had been initially charged and discharged was charged to 4.2 V by a 2C constant current method at 60 ° C., and then charged and discharged to discharge to 3.0 V by a 2C constant current method. Thereafter, this battery was charged and discharged at 25 ° C. for 3 cycles of 1/3 C constant current-constant voltage charging up to 4.2 V, followed by 1/3 C constant current discharging up to 3.0 V. The ratio of the last discharge capacity to the initial capacity at this time was defined as the capacity retention rate (%) after 100 cycles. Thereafter, an additional 400 cycles under the same conditions and the subsequent capacity check at 25 ° C. were performed, and the ratio of the final discharge capacity to the initial capacity at this time was defined as the capacity retention rate (%) after 500 cycles.

<Resistance maintenance rate evaluation test>
The battery at the initial stage and after 500 cycles was adjusted to 3.72 V, and from that state, constant current discharge was performed at −30 ° C. at various current values for 10 seconds. The voltage after 10 seconds was plotted against various current values, and the current value was determined such that the voltage after 10 seconds was 3V. The slope of the straight line obtained by connecting the point thus obtained and the point of the initial value (open circuit state) is defined as the low temperature resistance, and the ratio of the low temperature resistance after 500 cycles to the initial low temperature resistance is 500. The resistance retention rate after cycling (%) was used.

[Example 1]
Under a dry argon atmosphere, fully dried LiPF ₆ was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4) so that the total amount of the non-aqueous electrolyte was 1 mol / L. (This electrolyte solution may be referred to as “reference electrolyte solution”). LiFSO3 is added to the reference electrolyte solution in an amount of 0.25% by mass with respect to the non-aqueous electrolyte solution, and a compound of the following formula (i) is further added so as to be 0.25% by mass with respect to the non-aqueous electrolyte solution. A liquid was prepared. A battery was prepared by the above-described method using this electrolytic solution, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Example 2]
A battery was prepared in the same manner as in Example 1 except that the compound of the following formula (ii) was added so as to be 0.25% by mass with respect to the non-aqueous electrolyte instead of the compound of the formula (i). The capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Example 3]
Instead of the compound of formula (i), the compound of the following formula (iii) is 0.2
A battery was prepared in the same manner as in Example 1 except that the amount was 5% by mass, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Example 4]
Instead of the compound of the formula (i), a compound of the following formula (iv) is added to the non-aqueous electrolyte solution at 0.25.
A battery was prepared in the same manner as in Example 1 except that it was added so as to be mass%, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Comparative Example 1]
A battery was prepared in the same manner as in Example 1 except that LiFSO3 was not added to the nonaqueous electrolytic solution, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Comparative Example 2]
A battery was prepared in the same manner as in Example 2 except that LiFSO3 was not added to the non-aqueous electrolyte, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Comparative Example 3]
A battery was prepared in the same manner as in Example 3 except that LiFSO3 was not added to the nonaqueous electrolytic solution, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Comparative Example 4]
A battery was prepared in the same manner as in Example 4 except that LiFSO3 was not added to the non-aqueous electrolyte, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

[Comparative Example 5]
A battery was prepared in the same manner as in Example 1 except that the compound of formula (i) was not added to the nonaqueous electrolytic solution, and the capacity retention rate after 100 cycles and the capacity retention rate after 500 cycles were measured. Moreover, the improvement rate (%) with respect to these comparative examples 5 was calculated. The results thus obtained are shown in Table 1.

  From Table 1, in Examples 1 to 4 using the non-aqueous electrolyte of the present invention, excellent post-cycle capacity retention rates were obtained, and these were obtained by comparing conventional non-aqueous electrolytes (Comparative Examples 1 to 5). Compared with the case of using it, it was shown that it is a remarkable improvement effect to the extent that it cannot be explained by simple addition of individual performances.

[Example 5]
The resistance retention rate after 500 cycles of the battery prepared in Example 1 was measured. The results are shown in Table 2.
[Example 6]
The resistance retention rate after 500 cycles of the battery prepared in Example 2 was measured. The results are shown in Table 2.
[Comparative Example 6]
The resistance retention rate after 500 cycles of the battery prepared in Comparative Example 1 was measured. The results are shown in Table 2.

[Comparative Example 7]
The resistance retention rate after 500 cycles of the battery prepared in Comparative Example 2 was measured. The results are shown in Table 2.
[Comparative Example 8]
The resistance retention rate after 500 cycles of the battery prepared in Comparative Example 4 was measured. The results are shown in Table 2.

[Comparative Example 9]
The resistance maintenance rate of the battery prepared in Comparative Example 5 was measured after 500 cycles. The results are shown in Table 2.

From Table 2, in Examples 5 and 6 using the non-aqueous electrolyte of the present invention, excellent resistance maintenance ratios after 500 cycles were obtained, which are conventional non-aqueous electrolytes (Comparative Examples 6 to 9). Compared to the case of using, it was shown that the remarkable improvement effect cannot be explained by simple addition of individual performances.
As a cause of such an improvement effect, the compound represented by the general formula (1) and the compound represented by the general formula (2) in the present invention coexist in the non-aqueous electrolyte solution. When these compounds react on the positive electrode or the negative electrode, a hybrid film of both is formed, and it is presumed that a more stable and preferable film is formed as compared with conventional individual films.

  Since this cycle test is performed in a high temperature atmosphere of 60 ° C., it means that the effect of the present invention is effective not only for improving the cycle capacity retention rate but also for maintaining the capacity during high temperature storage. Yes.

According to the non-aqueous electrolyte solution of the present invention, both the cycle capacity maintenance rate and the resistance maintenance rate of the non-aqueous electrolyte secondary battery can be improved at the same time. Therefore, the non-aqueous electrolyte solution of the present invention and the non-aqueous electrolyte secondary battery using the same can be used for various known applications.
Specific examples include notebook computers, tablet computers, electronic book players, mobile phones, smartphones, lithium ion capacitors, portable CD / DVD / BD players, portable LCD TVs, handy cleaners, transceivers, electronic notebooks, calculators, Memory cards, radios, backup power supplies, motors, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game machines, watches, power tools, cameras, load leveling power supplies, natural energy storage power supplies, etc.

Claims (13)

A non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent, the non-aqueous electrolyte containing a compound represented by the following general formula (1) and a compound represented by the following general formula (2) A non-aqueous electrolyte characterized by
M (FSO ₃ ) _x (1)
[M is a metal atom, NR ¹ ₄ or PR ¹ ₄ (where R ¹ is an organic group having 1 to 12 carbon atoms or a hydrogen atom (provided that all four R ¹ are hydrogen atoms) A plurality of R ¹ may be the same as or different from each other, and some or all of the four R ¹ may form a ring together with the nitrogen atom or phosphorus atom to which they are bonded. is good), when M is a metal atom, x is an integer of 1 or more to a valence of the metal atom M, when M is ^NR _{1 4} or ^PR _{1 4,} x is 1]

(R ² represents a halogen atom or an organic group that may contain a C 1-6 hetero atom, and R ³ represents an organic group that may contain a C 3-12 hetero atom)   In the said General formula (1), M is a metal atom, The non-aqueous electrolyte solution of Claim 1 characterized by the above-mentioned.   2. The non-aqueous electrolyte solution according to claim 1, wherein in the general formula (1), M is any one of a lithium atom, a sodium atom, and a potassium atom. 4. The non-aqueous electrolyte solution according to claim 1, wherein R ² is a halogen atom in the general formula (2). 5. The nonaqueous electrolytic solution according to any one of claims 1 to 3, wherein R ² in the general formula (2) is a hydrocarbon group. 4. The nonaqueous electrolytic solution according to claim 1, wherein, in the general formula (2), R ² is a C 1-6 organic group containing a hetero atom. 7. The non-aqueous electrolyte solution according to claim 1, wherein in the general formula (2), R ³ is an organic group having 3 to 12 carbon atoms having an oxygen atom. The non-aqueous electrolyte solution according to any one of claims 1 to 3, wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3).

(R ² represents a halogen atom or an organic group that may contain a C 1-6 hetero atom, and R ⁴ represents a C 1-5 alkylene group that may have a halogen atom. R ⁵ represents (It represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group, an alkynyl group, or an aryl group having 6 to 10 carbon atoms, which may have a halogen atom.)   The content of the compound represented by the general formula (1) is 0.01% by mass or more and 10% by mass or less with respect to the entire non-aqueous electrolyte solution. The non-aqueous electrolyte solution described in 1.   The content of the compound represented by the general formula (2) is 0.01% by mass or more and 10% by mass or less with respect to the whole non-aqueous electrolyte solution. The non-aqueous electrolyte solution described in 1.   It is a non-aqueous electrolyte secondary battery provided with the negative electrode and positive electrode which can occlude and discharge | release metal ion, and a non-aqueous electrolyte solution, Comprising: The non-aqueous electrolyte solution as described in any one of Claims 1 thru | or 10 is used. A non-aqueous electrolyte secondary battery characterized by the above.   The non-aqueous electrolyte secondary battery according to claim 11, wherein the positive electrode capable of inserting and extracting metal ions contains at least one layered transition metal oxide.   The non-aqueous electrolyte secondary battery according to claim 11 or 12, wherein the negative electrode capable of inserting and extracting metal ions contains at least a carbon compound.