JP2017168344A - Nonaqueous electrolyte solution for power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a nonaqueous electrolyte solution for a power storage device, which is enhanced in cycle characteristic and which enables the decrease in electric resistance of a nonaqueous electrolyte solution and allows a high capacity to be retained even after the repetition of charge and discharge; and a power storage device.SOLUTION: A nonaqueous electrolyte solution for a power storage device comprises an electrolyte dissolved in a nonaqueous solvent, and an organic carboxylate represented by the formula (1) below, provided that the electrolyte is a lithium salt soluble in the nonaqueous solvent: ((MOOC)-X)-A-Y-B-(Z-(COOM))(1) (where X, Y and Z independently represent a phenylene group or an alkylene group with 1-6 carbon atoms; A and B independently represent a sulfur atom, a secondary amino group, or a cyano group; M is an alkali-metal ion, an ammonium ion, a polyvalent metal ion, an imidazolium ion or a pyridinium ion; w, e, p, q, t, m and n are each 0 or an integer of 1-4, and w+t≥1, e≤1, p+q≥1, and m+n≥1).SELECTED DRAWING: None

Description

  The present invention relates to a nonaqueous electrolytic solution for an electricity storage device such as a lithium ion secondary battery.

  In recent years, with the widespread use of various portable electronic devices such as portable electronic terminals typified by mobile phones, smartphones, notebook computers, etc., secondary batteries play an important role as their power source. Examples of these secondary batteries include an aqueous battery and a non-aqueous electrolyte battery. Among them, the non-aqueous electrolyte secondary battery including a positive electrode and a negative electrode that can occlude and release lithium ions and the like and a non-aqueous electrolyte has a high voltage and high energy density, excellent safety, environmental problems, etc. In this respect, it has various advantages compared with other secondary batteries.

  As non-aqueous electrolyte secondary batteries currently in practical use, for example, a composite oxide of lithium and a transition metal is used as a positive electrode active material, and a material capable of doping and dedoping lithium is used as a negative electrode active material. A lithium ion secondary battery is mentioned. In the negative electrode active material of a lithium ion secondary battery, a carbon material is mentioned as a material which has the outstanding cycling characteristics. Among carbon materials, graphite is expected as a material that can improve the energy density per unit volume.

Further, in order to improve the characteristics of the lithium secondary battery, not only the characteristics of the negative electrode / positive electrode but also the characteristics of the non-aqueous electrolyte responsible for transferring lithium ions are required. As such a non-aqueous electrolyte, a lithium salt such as LiBF ₄ , LiPF ₆ , LiClO ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ was dissolved in an aprotic organic solvent. A non-aqueous solution is used (Non-Patent Document 1). Carbonates are known as typical examples of aprotic organic solvents, and the use of various carbonate compounds such as ethylene carbonate, propylene carbonate, and dimethyl carbonate has been proposed (Patent Documents 1 and 2).

On the other hand, a non-aqueous electrolyte in which LiBF ₄ , LiPF _{6 and the} like are dissolved as an electrolyte of the non-aqueous electrolyte has high conductivity indicating the transfer of lithium ions, and the oxidative decomposition voltage of LiBF ₄ and LiPF ₆ is high. It is known to be stable at high voltage, and contributes to drawing out the characteristics of the lithium secondary battery such as high voltage and high energy density.

  On the other hand, when using a non-aqueous electrolyte secondary battery such as a lithium secondary battery as each power source, the electrical resistance of the non-aqueous electrolyte is lowered to increase the conductivity of lithium ions, and charging, Even after repeated discharges, there is a demand for a long life that suppresses a decrease in battery capacity and maintains a high capacity, so-called cycle characteristics.

In order to achieve such an object, various proposals have conventionally been made for non-aqueous electrolytes to specify the structure of a lithium salt that is an electrolyte or to add a specific compound. For example, Patent Document 3 proposes adding a vinyl sulfone derivative having a specific structure to a non-aqueous electrolyte, and Patent Document 4 discloses a method other than a bifunctional lithium salt having a specific structure. It has been proposed to add a lithium salt that does not have a boron atom.
However, conventional non-aqueous electrolytes are not always satisfactory, including the cost, and further techniques are required for non-aqueous electrolytes for power storage devices.

JP-A-4-184872 Japanese Patent Laid-Open No. 10-27625 JP 11-329494 A Japanese Patent Laid-Open No. 2014-22334

  The present invention improves the solubility of the electrolyte in the non-aqueous electrolyte, lowers the electrical resistance of the non-aqueous electrolyte, and maintains a high capacity even after repeated many times of charging and discharging, so-called cycle It aims at providing the nonaqueous electrolyte for electrical storage devices, such as a lithium secondary battery which improved the characteristic, and the electrical storage device using this nonaqueous electrolytic solution.

  As a result of various researches, the present inventors have found a non-aqueous electrolyte solution for an electricity storage device that can achieve the above-described object, and an electricity storage device that uses the non-aqueous electrolyte solution, and have reached the present invention. is there. The present invention has the following gist.

(1) A nonaqueous electrolytic solution for an electricity storage device obtained by dissolving an electrolyte in a nonaqueous solvent, wherein the electrolyte is a lithium salt dissolved in the nonaqueous solvent and represented by the following formula (1) A nonaqueous electrolytic solution for an electricity storage device, comprising an organic carboxylate.

_{((MOOC) m -X) w} -A p -Y e -B q - (Z- (COOM) n) t (1)

(However, X, Y, and Z are each independently a phenylene group or an alkylene group having 1 to 6 carbon atoms. A and B are each independently a sulfur atom, a secondary amino group, or a cyano group. M is an alkali metal ion, ammonium ion, polyvalent metal ion, imidazolium ion or pyridinium ion, w, e, p, q, t, m, n are 0 or an integer of 1 to 4, w + t ≧ 1, e ≦ 1, p + q ≧ 1, and m + n ≧ 1.)

(2) The nonaqueous electrolytic solution for an electricity storage device according to (1), wherein the organic carboxylate in formula (1) has A and B are sulfur atoms, and m + n ≧ 1.
(3) The nonaqueous electrolytic solution for an electricity storage device according to (1), wherein the organic carboxylate is p + q ≧ 1 in formula (1).
(4) The organic carboxylate is lithium cyanoacetate, dilithium iminoacetate, trilithium nitrilotriacetate, lithium acetylthioacetate, dilithium thiodiglycolate, dilithium 3,3′-thiodipropionate, 1, The nonaqueous electrolytic solution for an electricity storage device according to any one of (1) to (3), which is 2-ethylenebis (thioglycolic acid) dilithium or methylenebis (thioglycolic acid) dilithium.
(5) The nonaqueous electrolytic solution for an electricity storage device according to any one of (1) to (4), wherein the organic carboxylate is contained in an amount of 0.0001 to 10% by mass.

(6) The nonaqueous electrolysis for an electricity storage device according to any one of (1) to (5), wherein the nonaqueous solvent contains a chain carbonate ester, a saturated cyclic carbonate ester, and an unsaturated cyclic carbonate ester. liquid.
(7) The non-aqueous solvent contains 30 to 80% by mass, 10 to 50% by mass, and 0.01 to 5% by mass of chain carbonate ester, saturated cyclic carbonate ester, and unsaturated cyclic carbonate ester, respectively. The non-aqueous electrolyte for electrical storage devices as described in said (6) containing.
(8) The nonaqueous electrolytic solution for an electricity storage device according to any one of (1) to (7), further including a second additive comprising a sulfonate, a sulfur-containing compound, or a boron salt.
(9) The lithium salt is LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ ) and LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) are at least one lithium salt selected from the group of (1) to (8) above The non-aqueous electrolyte for electrical storage devices of any one of Claims 1.
(10) An electricity storage device comprising the nonaqueous electrolytic solution according to any one of (1) to (9) above.
(11) The livestock device according to (10), wherein the electricity storage device is a lithium ion secondary battery.

  The non-aqueous electrolyte according to the present invention not only lowers the electric resistance of the non-aqueous electrolyte by increasing the solubility of the lithium electrolyte in the non-aqueous electrolyte, but also maintains a high capacity even after repeated charging and discharging. However, so-called cycle characteristics are improved. For this reason, the non-aqueous electrolyte for electrical storage devices, such as a lithium secondary battery excellent in the favorable initial characteristic and cycling characteristics, is provided.

Hereinafter, the nonaqueous electrolytic solution of the present invention and the electricity storage device using the same will be described in detail.
<Nonaqueous solvent>
As the nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention, various solvents can be used. For example, an aprotic polar solvent is preferable. Specific examples thereof are ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate. And cyclic carbonates such as 4,5-difluoroethylene carbonate; lactones such as γ-ptilolactone and γ-valerolactone; cyclic sulfones such as sulfolane; cyclic ethers such as tetrahydrofuran and dioxane; ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate , Methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl Chain carbonates such as propyl carbonate and methyl trifluoroethyl carbonate; nitriles such as acetonitrile; chain ethers such as dimethyl ether; chain carboxylic acid esters such as methyl propionate; chain glycol ethers such as dimethoxyethane; , 2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (CF ₂ HCF ₂ CH ₂ OCF ₂ CF ₂ H), 1,1,2,2-tetrafluoroethyl-2,2 , 3,3,3-pentafluoro-propyl ether _{(CF 3 CF 2 CH 2 OCF} 2 CF 2 H), ethoxy-2,2,2-trifluoro-ethoxy - ethane _{(CF 3 CH 2 OCH 2 CH} 2 OCH 2 CH _And fluorine-containing ethers such as ₃ ). These can be used individually by 1 type or in combination of 2 or more types.

  As the non-aqueous solvent, it is more preferable to use a carbonate-based solvent such as cyclic carbonate and chain carbonate from the viewpoint of ion conductivity. It is more preferable to use a combination of a cyclic carbonate and a chain carbonate as the carbonate solvent. Among the above, as the cyclic carbonate, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are preferable. Among the above-mentioned chain carbonates, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate are preferable. In the case of using a carbonate-based solvent, another non-aqueous solvent such as a nitrile compound or a sulfone-based solvent can be further added as necessary from the viewpoint of improving battery physical properties.

  As the nonaqueous solvent, in the present invention, it is particularly preferable to contain a chain carbonate ester, a saturated cyclic carbonate ester, and an unsaturated cyclic carbonate ester. In the case of containing these three kinds of carbonates, it is particularly preferable since the effects of the present invention are exhibited. In the nonaqueous solvent used in the present invention, the chain carbonate ester, the saturated cyclic carbonate ester, and the unsaturated cyclic carbonate ester are 30 to 80% by mass, 10 to 50% by mass, respectively. And 0.01 to 5% by mass, and 50 to 70% by mass, 20 to 30% by mass, and 0.1 to 2% by mass are more preferable.

When the chain ester carbonate is smaller than 30% by mass, the viscosity of the electrolytic solution is increased, and in addition, it is solidified at a low temperature, so that sufficient characteristics cannot be obtained. If it is large, the dissociation / solubility of the lithium salt will decrease, and the ionic conductivity of the electrolyte will decrease. When the saturated cyclic carbonate is less than 10% by mass, the dissociation / solubility of the lithium salt decreases, and the ionic conductivity of the electrolyte decreases, and conversely when it is greater than 50% by mass, the electrolyte In addition, the viscosity of the resin increases and, at the same time, solidifies at a low temperature, so that sufficient characteristics cannot be obtained.
Further, when the unsaturated cyclic carbonate is smaller than 0.01% by mass, a good film is not formed on the negative electrode surface, so that the cycle characteristics are deteriorated. Conversely, when the unsaturated cyclic carbonate is larger than 5% by mass, for example, When stored at a high temperature, the electrolyte solution is likely to generate gas, and the pressure in the battery is increased, which is undesirable in practice.

  Examples of the chain carbonate used in the present invention include a chain carbonate having 3 to 9 carbon atoms in total. Specifically, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, di-n-butyl carbonate, di-t-butyl carbonate, n-butyl isobutyl carbonate, n-butyl-t-butyl carbonate, isobutyl-t-butyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate, n-butyl-n-propyl carbonate, isobutyl-n- B pills carbonate, t- butyl -n- propyl carbonate, n- butyl isopropyl carbonate, isobutyl isopropyl carbonate, and t-butyl isopropyl carbonate. Among these, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable, but are not particularly limited. Two or more of these chain carbonates may be mixed.

  Examples of the saturated cyclic carbonate used in the present invention include ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate. Among these, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are more preferable. By using propylene carbonate, a stable nonaqueous electrolytic solution can be provided in a wide temperature range. Two or more of these saturated cyclic carbonates may be mixed.

Examples of the unsaturated cyclic carbonate used in the present invention include vinylene carbonate derivatives represented by the following general formula (I).

In the above general formula (I), R ₁ and R ₂ are each independently a hydrogen atom, a halogen atom, or an alkyl group that may contain a halogen atom having 1 to 12 carbon atoms. Among them, preferably R ₁ and R ₂ are hydrogen (a vinylene carbonate).

  Specific examples of the vinylene carbonate derivative include the following compounds. Vinylene carbonate, fluorovinylene carbonate, methyl vinylene carbonate, fluoromethyl vinylene carbonate, ethyl vinylene carbonate, propyl vinylene carbonate, butyl vinylene carbonate, dimethyl vinylene carbonate, diethyl vinylene carbonate, dipropyl vinylene carbonate, etc. are limited thereto. It is not a thing.

Among these compounds, vinylene carbonate is effective and advantageous in terms of cost. In addition, regarding the said vinylene carbonate derivative, it is at least 1 type, and it is also possible to be independent or to mix.
Moreover, as another unsaturated cyclic carbonate used by this invention, the alkenyl ethylene carbonate represented by the following general formula (II) is mentioned.

In the above formula (II), R _{3 to} R ₆ each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group that may contain a halogen atom having 1 to 12 carbon atoms, or a carbon number of 2 to 2. 12 alkenyl groups, at least one of which is an alkenyl group having 2 to 12 carbon atoms. Especially, when one of R < ₃ > -R < ₆ > is a vinyl group and the remainder is hydrogen (the compound of (II) is 4-vinyl ethylene carbonate), it is preferable.

  Specific examples of the alkenylethylene carbonate include compounds such as 4-vinylethylene carbonate, 4-vinyl-4-methylethylene carbonate, 4-vinyl-4-ethylethylene carbonate, 4-vinyl-4-n-propylethylene carbonate, and the like. Can be mentioned.

  The nonaqueous solvent used in the present invention may contain other various solvents in addition to the above components. Examples of these other various solvents include cyclic carboxylic acid esters, chain esters having 3 to 9 carbon atoms, and chain ethers having 3 to 6 carbon atoms. These other various solvents are preferably contained in the nonaqueous electrolytic solution in an amount of 0.2 to 10% by mass, particularly preferably 0.5 to 5% by mass.

  Examples of the cyclic carboxylic acid ester (lactone compound having 3 to 9 total carbon atoms) include γ-butyrolactone, γ-valerolactone, γ-caprolactone, ε-caprolactone, and the like. Among these, γ-butyrolactone and γ-valerolactone are more preferable, but not particularly limited. Two or more of these cyclic carboxylic acid esters may be mixed.

  Examples of the chain ester having 3 to 9 carbon atoms include methyl acetate, ethyl acetate, acetic acid-n-propyl, acetic acid-isopropyl, acetic acid-n-butyl, acetic acid isobutyl, acetic acid-t-butyl, propionic acid. Mention may be made of methyl, ethyl propionate, propionate-n-propyl, propionate-isopropyl, propionate-n-butyl, propionate isobutyl, propionate-t-butyl. Of these, ethyl acetate, methyl propionate, and ethyl propionate are preferred.

  Examples of the chain ether having 3 to 6 carbon atoms include dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, and ethoxymethoxyethane. Of these, dimethoxyethane and diethoxyethane are more preferable.

  Further, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene and the like can be used. .

<Lithium salt>
A lithium salt is used as the solute of the nonaqueous electrolytic solution of the present invention. The lithium salt is not particularly limited as long as it can be dissolved in the non-aqueous solvent. Specific examples thereof are as follows.
(A) Inorganic lithium salt:
LiPF _6, LiAsF _6, inorganic fluoride salts LiBF ₄ or the _{like, LiClO 4, LiBrO 4, LiIO} 4, perhalogenate etc. like.
(B) Organic lithium salt:
Organic sulfonates such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂₎ perfluoroalkylsulfonic acid imide salts such as, _LiC (CF 3 _{SO 2)} perfluoroalkylsulfonic acid methide salts such as _{3, LiPF (CF 3) 5} , LiPF 2 (CF 3) 4, LiPF 3 (CF ₃ ) ₃ , LiPF ₂ (C ₂ F ₅ ) ₄ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF (n-C ₃ F ₇ ) ₅ , LiPF ₂ (n-C ₃ F ₇ ) ₄ , LiPF ₃ ( _{n-C 3 F 7) 3} , LiPF (iso-C 3 F 7) 5, LiPF 2 (iso-C 3 F 7) 4, LiPF 3 (iso-C 3 F 7) 3, LiB (CF 3 _{4, LiBF (CF 3) 3} , LiBF 2 (CF 3) 2, LiBF 3 (CF 3), LiB (C 2 F 5) 4, LiBF (C 2 F 5) 3, LiBF 2 (C 2 F 5) ₂ , LiBF ₃ (C ₂ F ₅ ), LiB (n—C ₃ F ₇ ) ₄ , LiBF (n—C ₃ F ₇ ) ₃ , LiBF ₂ (n—C ₃ F ₇ ) ₂ , LiBF ₃ (n— _{C 3 F 7), LiB (} iso-C 3 F 7) 4, LiBF (iso-C 3 F 7) 3, LiBF 2 (iso-C 3 F 7) 2, LiBF 3 (iso-C 3 F 7) Inorganic fluoride salt fluorophosphate obtained by substituting a part of fluorine with a perfluoroalkyl group, and fluorine-containing organic lithium salt of perfluoroalkyl.

In the present invention, among the above, LiPF ₆ , LiBF ₄ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ( C ₂ F ₅ SO ₂ ) and LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) are more preferable. Two or more of these lithium salts may be mixed.

  The concentration of the lithium salt, which is the solute of the nonaqueous electrolytic solution of the present invention, is preferably 0.5 to 3 mol / liter, particularly 0.7 to 2 mol / liter. If this concentration is too low, the ionic conductivity of the non-aqueous electrolyte is insufficient due to an absolute concentration shortage. If the concentration is too high, the ionic conductivity decreases due to an increase in viscosity, and precipitation at a low temperature occurs. Since it is likely to occur and causes problems, the performance of the nonaqueous electrolyte battery is undesirably lowered.

<Organic carboxylate>
The nonaqueous electrolytic solution of the present invention contains an organic carboxylate represented by the following formula (1).

_{((MOOC) m -X) w} -A p -Y e -B q - (Z- (COOM) n) t (1)

In the above formula (1), X, Y, Z, A, B, M, and w, e, p, q, t, m, and n are as defined above.
Among these, X, Y, and Z are each independently preferably a phenylene group or an alkylene group having 1 to 6 carbon atoms. A and B are each independently preferably a sulfur atom, a secondary amino group, or a cyano group. M is preferably an alkali metal ion, particularly preferably a lithium ion.
Moreover, w, e, p, q, t, m, and n are 0 or an integer of 1 to 4, w + t ≧ 1, e ≦ 1, p + q ≧ 1, and m + n ≧ 1. )
In addition, when X, Y, and Z in Formula (1) are an alkylene group or a phenylene group, the hydrogen atom that these groups have is optionally substituted with a halogen atom, an alkyl group, or a silyl group. Also good. Moreover, when A and B in Formula (1) are secondary amino groups, the hydrogen atom which an amino group has may be arbitrarily substituted by the alkyl group or the silyl group.

Examples of the organic carboxylate include lithium cyanoacetate, lithium acetamidoacetate, lithium N- (2-cyanoethyl) glycine, lithium dimethyloxamate, dilithium iminodiacetic acid, dilithium N-methyliminodiacetic acid, and nitrilotriacetic acid. Lithium, ethylenediamine-N, N′-dilithium diacetate, ethylenediaminetetraacetic acid tetralithium, lithium (acetylthio) acetate, lithium thiophenoxyacetate, lithium 3- (methylmercapto) propionate, 2-mercaptopropionic acid, 2,2 '-Lithium thiodiglycolate, tetralithium thiodisuccinate, S- (carboxymethyl) -L-cysteine dilithium, S- (carboxymethyl) -L-cysteine, dilithium 3,3'-thiodipropionate , Dilithium dithiodiglycolate, dilithium 2,2'-dithiodipropionate, methylenebis (thio Illustrative examples include dilithium glycolate, 1,2-ethylenebis (thioglycolate) dilithium, and bis (carboxymethyl) dilithium trithiocarbonate.
Among them, organic carboxylates include lithium cyanoacetate, dilithium iminoacetate, trilithium nitrilotriacetate, dilithium thiodiglycolate, dilithium 3,3′-thiodipropionate, 1,2-ethylenebis ( Thioglycolic acid) dilithium or methylenebis (thioglycolic acid) dilithium is preferred.

  The content of the organic carboxylate in the non-aqueous electrolyte of the present invention is preferably 0.0001 to 10% by mass, more preferably 0.001 to 2% by mass, and particularly preferably 0.01 to 1% by mass. It is. When the concentration is less than 0.0001% by mass, the resistance reduction effect is reduced. On the other hand, when it exceeds 10 mass%, film resistance becomes high and life performance deteriorates, which is not preferable.

<Second additive substance>
In the nonaqueous electrolytic solution of the present invention, a second additive substance may be contained in addition to the specific organic carboxylate in order to improve the life performance and resistance performance of the electricity storage device. The second additive substance includes a sulfur-containing compound (excluding the organic carboxylate represented by the formula (1)), a cyclic acid anhydride, a carboxylic acid compound, a sulfonate, and a boron-containing compound. One or more selected compounds can be used.

  Examples of the sulfur-containing compound include 1,3-propane sultone (PS), propene sultone, ethylene sulfite, 1,4-butane sultone, methyl methanesulfonate, ethyl methanesulfonate, dimethyl methanedisulfonate, diethyl methanedisulfonate, Dipropyl methanedisulfonate, bis (trifluoromethyl) methanedisulfonate, bis (trimethylsilyl) methanedisulfonate, methylenemethanedisulfonic acid, ethylene methanedisulfonate, propylenemethanemethanesulfonate, methyleneethylenedisulfonate, ethyleneethylenedisulfonate, ethanedisulfone Dimethyl acid, Diethyl ethanedisulfonate, Bis (trifluoromethyl) ethanedisulfonate, Bis (trimethylsilyl) ethanedisulfonate, Dimethylpropanedisulfonate , Diethyl propanedisulfonate, methylene propanedisulfonate, ethylene propanedisulfonate, dimethyl 1,5-naphthalenedisulfonate, dimethyl butanedisulfonate, diethyl butanedisulfonate, 5-vinyl-hexahydro1,3,2-benzodioxathiol -2-oxide, 1,4-butanediol dimethanesulfonate, 1,3-butanediol dimethanesulfonate, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, divinylsulfone, 1,2- Bis (vinyl sulfonyl) methane etc. are mentioned.

  Examples of the cyclic acid anhydride include glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, succinic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride 4-cyclohexene-1,2-dicarboxylic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, phenylsuccinic anhydride, 2- Carboxylic anhydride such as phenylglutaric anhydride, phthalic anhydride, pyromellitic anhydride, fluorosuccinic anhydride, tetrafluorosuccinic anhydride, 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfone Acid anhydride, 1,4-butanedisulfonic anhydride, 1,2-benzenedisulfonic anhydride, tetraf Oro-1,2-ethanedisulfonic anhydride, hexafluoro-1,3-propanedisulfonic anhydride, octafluoro-1,4-butanedisulfonic anhydride, 3-fluoro-1,2-benzenedisulfonic anhydride Products, 4-fluoro-1,2-benzenedisulfonic anhydride, 3,4,5,6-tetrafluoro-1,2-benzenedisulfonic anhydride, and the like.

Examples of the carboxylic acid compound include lithium oxalate, lithium malonate, lithium difluoromalonate, lithium succinate, lithium tetrafluorosuccinate, lithium adipate, lithium glutarate, lithium acetonedicarboxylate, lithium 2-oxobutyrate, and oxal. Lithium acetate, lithium 2-oxoglutarate, lithium acetoacetate, 3-oxocyclobutanecarboxylic acid, 3-oxocyclopentanecarboxylic acid, lithium 2-oxovalerate, lithium pyruvate, lithium glyoxylate, 3,3-dimethyl-2 -Lithium oxobutyrate, lithium 2-hydroxypropionate, 2-methyl lithium lactate, lithium tartrate, lithium cyanoacetate, lithium 2-mercaptopropionate, lithium methylenebis (thioglycolate) thiosuccinate, 3- (methylthio) propiate Lithium phosphate, 3,3'-thiodipropionic lithium, lithium dithiodiglycolic acid, lithium 2,2'-thio diglycolic acid, 2,4-lithium-dicarboxylic acid, lithium acetylthio acetate.
As the sulfonate, a compound that is soluble in a non-aqueous solvent used in a lithium ion secondary battery is preferable. As long as there is solubility, the kind of the salt is not asked. For example, alkali metal salts such as lithium, sodium and potassium; polyvalent metal salts such as calcium, magnesium, manganese and iron; ammonium salts such as tetramethylammonium, tetraethylammonium, tetrapropylammonium and tetrabutylammonium; dimethylimidazolium, Imidazolium salts such as dimethylimidazolium and ethylmethylimidazolium; pyrididium salts such as methylpyridium and ethylpyridium can be used. Among the above, alkali metal salts such as lithium, sodium and potassium are preferable, and lithium salts are particularly preferable. Lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium hexafluoromethanesulfonate, lithium 1,3-propanesulfonate, lithium 1,4-butanesulfonate, dilithium 1,1-methanedisulfonate, 1,2-ethane Dilithium disulfonate, dilithium 1,3-propanedisulfonate, dilithium 1-methyl-1,3-propanedisulfonate, dilithium 1,4-butanedisulfonate, dilithium methoxymethanedisulfonate, dilithium ethoxymethanedisulfonate, 1,1 -Dilithium prop-2-yldisulfonate, disodium 1,1-methanedisulfonate, disodium 1,2-ethanedisulfonate, disodium 1,3-propanedisulfonate, disodium 1,4-butanedisulfonate, Disodium toximethanedisulfonate, disodium ethoxymethanedisulfonate, disodium 1,1-prop-2-yldisulfonate, magnesium 1,1-methanedisulfonate, magnesium 1,2-ethanedisulfonate, 1,3- Examples thereof include magnesium propanedisulfonate, magnesium 1,4-butanedisulfonate, lithium aniline-2,5-disulfonate, lithium 4,4′-biphenyldisulfonate, and the like.

Examples of the boron-containing compound include LiBF ₂ (C ₂ O ₄ ), LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (CO ₂ CH ₂ CO ₂ ), LiB (CO ₂ CH ₂ CO ₂ ) ₂ , LiB (CO ₂ CF ₂ CO ₂ ) ₂ , LiBF ₂ (CO ₂ CF ₂ CO ₂ ), LiBF ₃ (CO ₂ CH ₃ ), LiBF ₃ (CO ₂ CF ₃ ), LiBF ₂ (CO ₂ CH ₃ ) ₂ , LiBF ₂ ( _{CO 2 CF 3) 2, LiBF} (CO 2 CH 3) 3, LiBF (CO 2 CF 3) 3, LiB (CO 2 CH 3) 4, LiB (CO 2 CF 3) 4, Li 2 B 2 O 7, li ₂ B ₂ O ₄ and the like.

  As said 2nd additive substance, each 1 type may be used independently and 2 or more types may be used together. In addition, when the water electrolyte adds the second additive substance, the content of the second additive substance in the non-aqueous electrolyte is 0.01 to 5% by mass, although it varies depending on the second additive substance. Preferably, it is 0.1-2 mass%.

<Power storage device>
The non-aqueous electrolyte of the present invention can be used in various power storage devices such as a lithium ion secondary battery, an electric double layer capacitor, a hybrid battery in which one of a positive electrode and a negative electrode is a battery and the other is a double layer. Will describe a typical lithium ion secondary battery.
As the negative electrode active material constituting the negative electrode, carbon materials capable of doping / de-doping lithium ions, metallic lithium, lithium-containing alloys, silicon capable of being alloyed with lithium, silicon alloys, tin, Tin alloy, tin oxide capable of doping / de-doping lithium ions, silicon oxide, transition metal oxide capable of doping / de-doping lithium ions, doping / desorption of lithium ions Any of the transition metal nitrogen compounds which can be doped, or a mixture thereof can be used. The negative electrode generally has a configuration in which a negative electrode active material is formed on a current collector such as a copper foil or expanded metal. In order to improve the adhesion of the negative electrode active material to the current collector, for example, it may contain a polyvinylidene fluoride binder, a latex binder, etc., and carbon black, amorphous whisker carbon, etc. are added as a conductive aid. May be used.

As the carbon material constituting the negative electrode active material, for example, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, organic polymer compound fired bodies (phenol resin, furan resin, etc.) are suitable. And carbonized by firing at a suitable temperature), carbon fiber, activated carbon and the like. The carbon material may be graphitized. As the carbon material, a carbon material having a (002) plane spacing (d002) of 0.340 nm or less, particularly measured by X-ray diffraction, is preferable, or a graphite having a true density of 1.70 g / cm ³ or more or close thereto. A highly crystalline carbon material having properties is desirable. When such a carbon material is used, the energy density of the nonaqueous electrolyte battery can be increased.
Further, those containing boron in the carbon material, those coated with a metal such as gold, platinum, silver, copper, Sn, Si, or those coated with amorphous carbon can be used. One type of these carbon materials may be used, or two or more types may be used in combination as appropriate.
Silicon, silicon alloy, tin, tin alloy that can be alloyed with lithium, tin oxide that can be doped / undoped with lithium ions, silicon oxide, transition metals that can be doped / undoped with lithium ions In the case of using an oxide, any of the above-described carbonaceous materials has a higher theoretical capacity per weight and is a suitable material.

On the other hand, the positive electrode active material constituting the positive electrode can be formed from various materials that can be charged and discharged. Examples thereof include lithium-containing transition metal oxides, lithium-containing transition metal composite oxides using one or more transition metals, transition metal oxides, transition metal sulfides, metal oxides, and olivine-type metal lithium salts. For _example, in _{LiCoO 2, LiNiO 2, LiMn 2} O 4, LixMO 2 such as LiMnO ₂ (where, M is one or more transition metals, x is different according to the charge and discharge state of the battery, usually 0.05 ≦ x ≦ 1.20), a composite oxide of lithium and one or more transition metals (lithium transition metal composite oxide), or a transition metal atom that is a main component of these lithium transition metal composite oxides. Composite oxides partially substituted with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Yb, FeS ₂ , TiS ₂ , chalcogenide of transition elements such as V ₂ 0 ₅ , MoO ₃ , MoS ₂ or polymers such as polyacetylene and polypyrrole can be used. Possible lithium transition metal composite oxides and metal composite oxide materials in which transition metal atoms are partially substituted are preferred.

In addition, a material in which a substance having a composition different from that of the substance constituting the main cathode active material is attached to the surface of the cathode active material can be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, etc .; 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.
The positive electrode generally has a configuration in which a positive electrode active material is formed on a current collector such as an aluminum, titanium, or stainless steel foil, or an expanded metal. In order to improve the adhesion of the positive electrode active material to the current collector, for example, polyvinylidene fluoride binder and latex binder, carbon black, amorphous whisker, graphite etc. to improve the electron conductivity in the positive electrode It may contain.

The separator is preferably a membrane that electrically insulates the positive electrode from the negative electrode and is permeable to lithium ions. For example, a porous membrane such as a microporous polymer film is used. As the microporous polymer film, a porous polyolefin film is particularly preferable, and more specifically, a porous polyethylene film, a porous polypropylene film, or a multilayer film of a porous polyethylene film and a polypropylene film is preferable. Furthermore, a polymer electrolyte can also be used as a separator. As the polymer electrolyte, for example, a polymer material in which a lithium salt is dissolved, a polymer material swollen with an electrolytic solution, and the like can be used, but the polymer electrolyte is not limited thereto.
The non-aqueous electrolyte of the present invention may be used for the purpose of obtaining a polymer electrolyte by swelling a polymer substance with the non-aqueous electrolyte, or a separator having a combination of a porous polyolefin film and a polymer electrolyte. A non-aqueous electrolyte may be soaked in the liquid.
The shape of the lithium ion secondary battery using the non-aqueous electrolyte of the present invention is not particularly limited, and may be various shapes such as a cylindrical shape, a square shape, an aluminum laminate type, a coin shape, and a button shape. it can.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples, and can be modified within the scope of the present invention.

<Preparation of electrolytes 1-1 to 1-8>
As the reference electrolyte 1-1, a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and fluoroethylene carbonate (FEC) (volume mixing ratio is 30: 68: 2), and LiPF6 as a lithium salt is 1 mol / liter. It was prepared by containing and dissolving at a concentration of 1 liter.
Next, a predetermined amount of the compound shown in Table 1 was added to the reference electrolyte solution 1-1 to prepare electrolyte solutions 1-2 to 1-8.

<Preparation of electrolytic solutions 2-1 to 2-13>
As a reference electrolyte solution 2-1, a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) (volume mixing ratio is 30: 68: 2), and 1 mol of LiPF ₆ as a lithium salt After adding to a concentration of 1 / liter, 0.5% vinylene carbonate (VC) was added and dissolved.
Next, a predetermined amount of lithium thiodipropionate was added to this reference electrolytic solution 2-1, to prepare electrolytic solutions 2-2 to 2-7.
Subsequently, 0.1% of lithium thiodipropionate was added to the reference electrolyte solution 2-1, and a predetermined amount of the compounds shown in Table 2 was added to prepare electrolyte solutions 2-8 to 2-13.

<Production of battery>
A flat wound electrode group in which a positive electrode formed by applying a positive electrode mixture to an aluminum current collector and a negative electrode formed by applying a negative electrode mixture to a copper current collector via a separator and a non-aqueous electrolyte And a battery cell having a shape of width 30 mm × height 30 mm × thickness 3.0 mm.
The positive electrode is made of 5% by mass of polyvinylidene fluoride as a binder, 4% by mass of acetylene black as a conductive agent, and a positive electrode active material LiNi _0.5 Mn ₀ that is a composite oxide powder of lithium-nickel-manganese-cobalt. _.3 Co _0.2 O ₂ 91% by mass of N-methylpyrrolidone was added to a positive electrode mixture prepared to prepare a paste, which was applied to both sides of an aluminum foil current collector having a thickness of 18 μm. Then, after removing the solvent by drying, it was produced by rolling with a roll press.

  The negative electrode is a slurry prepared by mixing 95.8% by mass of artificial graphitizable carbon powder, 2.0% by mass of styrene butadiene rubber (SBR) as a binder and 2.2% by mass of carboxymethyl cellulose and using water as a dispersion medium. The slurry was applied to both sides of a copper foil having a thickness of 12 μm, and the solvent was dried and removed, followed by rolling with a roll press. A polyethylene microporous membrane was used for the separator.

Using the battery cell produced above, a battery was produced in the following procedure.
a. 0.7 g of various electrolytes were weighed out, poured into the injection port of the battery cell, and after reducing the pressure, the injection port was sealed.
b. In a state where the sealed battery cell was maintained in a 45 ° C. atmosphere, the battery cell was charged at 12 mA up to 4.3 V, and then discharged at 12 mA up to 3.0 V.
c. The internal gas of the battery cell discharged to 3.0 V was removed under reduced pressure to produce a battery.

<Battery evaluation>
About the battery produced above, the charge / discharge characteristic was measured as follows.
(1) Resistance evaluation Charged to SOC 50% at 25 ° C, discharged for 10 seconds at 0.2C, 0.5C, 1.0C, and 2.0C, respectively, under each environment, and DC resistance value Asked.
(2) Capacity maintenance rate After charging to 4.2 V at 1 C rate in a 45 ° C. atmosphere, the battery was discharged to 3.0 V at 1 C rate in the same atmosphere, and the discharge capacity value was taken as the initial capacity value. Next, 300 times were repeated under the same conditions, and the discharge capacity value at the 300th time was taken as the post-cycle capacity value. The capacity retention rate was determined from the initial capacity value and the post-cycle capacity value using the following formula.
Capacity retention rate (%) = (Capacity value after cycle / Initial capacity value) × 100 (1)

<Examples 1 to 19>
Using the non-aqueous electrolyte solution 1-1 to 1-8 shown in Table 1 and the non-aqueous electrolyte solution 2-1 to 2-13 shown in Table 2, Laminated batteries of Examples 1 to 7 and Comparative Example 1, Examples 8 to 19 and Comparative Example 2 were prepared, and initial resistance values were determined at 25 ° C. in an atmosphere, and the initial resistance values are shown in Table 3.
Next, in an atmosphere of 45 ° C., charging up to 4.2 V and discharging up to 3.0 V at a 1 C rate is repeated 300 times, and a capacity maintenance ratio is obtained from the initial capacity value and the post-cycle discharge capacity value after 300 times. The results are shown in Table 3.

  As shown in Table 3, the addition of lithium carboxylate has the effect of reducing direct current resistance and the effect of improving the cycle capacity retention rate. Furthermore, there is a further improvement in capacity retention when combined with other additives.

  The water electrolyte of the present invention is widely used for power storage devices such as power supplies for various consumer devices such as mobile phones, smartphones, notebook personal computers, industrial power supplies, storage batteries, and automotive power supplies.

Claims (11)

An organic carboxylic acid represented by the following formula (1), which is a nonaqueous electrolytic solution for an electricity storage device obtained by dissolving an electrolyte in a nonaqueous solvent, wherein the electrolyte is a lithium salt dissolved in the nonaqueous solvent. A nonaqueous electrolytic solution for an electricity storage device, comprising a salt.

_{((MOOC) m -X) w} -A p -Y e -B q - (Z- (COOM) n) t (1)

(However, X, Y, and Z are each independently a phenylene group or an alkylene group having 1 to 6 carbon atoms. A and B are each independently a sulfur atom, a secondary amino group, or a cyano group. M is an alkali metal ion, ammonium ion, polyvalent metal ion, imidazolium ion or pyridinium ion, w, e, p, q, t, m, n are 0 or an integer of 1 to 4, w + t ≧ 1, e ≦ 1, p + q ≧ 1, and m + n ≧ 1.)   The non-aqueous electrolytic solution for an electricity storage device according to claim 1, wherein the organic carboxylate has A and B in the formula (1) are sulfur atoms, and m + n ≧ 1.   The non-aqueous electrolyte for an electricity storage device according to claim 1, wherein the organic carboxylate is p + q ≧ 2 in formula (1).   The organic carboxylate is lithium cyanoacetate, dilithium iminoacetate, trilithium nitrilotriacetate, lithium acetylthioacetate, dilithium thiodiglycolate, dilithium 3,3′-thiodipropionate, 1,2-ethylene The nonaqueous electrolytic solution for an electricity storage device according to any one of claims 1 to 3, which is bis (thioglycolic acid) dilithium or methylene bis (thioglycolic acid) dilithium.   The non-aqueous electrolyte for electrical storage devices of any one of Claims 1-4 which contains the said organic carboxylate 0.0001-10 mass%.   The nonaqueous electrolytic solution for an electricity storage device according to any one of claims 1 to 5, wherein the nonaqueous solvent contains a chain carbonate ester, a saturated cyclic carbonate ester, and an unsaturated cyclic carbonate ester.   The non-aqueous solvent contains 30 to 80% by mass, 10 to 50% by mass, and 0.01 to 5% by mass of chain carbonate, saturated cyclic carbonate, and unsaturated cyclic carbonate, respectively. Item 7. A nonaqueous electrolytic solution for an electricity storage device according to Item 6.   Furthermore, the non-aqueous electrolyte for electrical storage devices of any one of Claims 1-7 containing the 2nd additive consisting of a sulfonate, a sulfur-containing compound, or a boron salt. The lithium salt is LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ). _{(C 2 F 5 SO 2)} , and _{LiN (CF 3 SO 2) (} C 4 F 9 SO 2) according to any one of claims 1 to 8 is at least one lithium salt selected from the group of Non-aqueous electrolyte for electricity storage devices.   The electrical storage device which uses the non-aqueous electrolyte of any one of Claims 1-9.   The livestock device according to claim 9, wherein the electricity storage device is a lithium secondary battery.