Electrolytes and non-aqueous electrolytes for power storage devices

Abstract

To provide an enhanced power storage device capable of maintaining a high capacity even after charging and discharging are repeated while reducing electric resistance.SOLUTION: A power storage device comprises a positive electrode, a negative electrode, and an electrolyte between both electrodes. The electrolyte contains a lithium-containing complex compound expressed by, for example, the following formulas (1) to (3): (Li)m(A)n(UFx)y (1); (Li)m(Si)n(O)q(UFx)y (2) (in the formulas, A is O, S, P, or N. U is a boron atom or a phosphorus atom. m and n are independently 1 to 6. q is 1 to 12. x is 3 or 5. y is 1 to 6), and (Li)m(O)n(B)p(OWFq)x (3) (in the formula, W is a boron atom or a phosphorus atom. m, p, and x are independently 1 to 15. n is 0 to 15. and q is 3 or 5).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrolyte for an electricity storage device such as a lithium ion secondary battery, and a nonaqueous electrolyte solution for an electricity storage device containing the electrolyte. [Background technology]

[0002] In recent years, with the widespread use of various portable electronic devices, such as portable electronic terminals typified by mobile phones and laptop computers, secondary batteries have played an important role as their power sources. Examples of these secondary batteries include aqueous batteries and nonaqueous electrolyte batteries. Among these, nonaqueous electrolyte secondary batteries, which include a positive electrode and a negative electrode capable of absorbing and releasing lithium ions and a nonaqueous electrolyte, have various advantages over other secondary batteries, such as high voltage and high energy density, excellent safety, and environmental friendliness.

[0003] Examples of non-aqueous electrolyte secondary batteries currently in practical use include lithium-ion secondary batteries, which use a composite oxide of lithium and a transition metal as the positive electrode active material and a material capable of doping and dedoping lithium as the negative electrode active material. Carbon materials are known as negative electrode active materials with excellent cycle characteristics for lithium-ion secondary batteries. Among carbon materials, graphite is expected to be a material that can improve the energy density per unit volume.

[0004] Furthermore, to improve the performance of lithium secondary batteries, improvements are required not only in the performance of the negative and positive electrodes but also in the performance of the nonaqueous electrolyte responsible for the transport of lithium ions. Non-aqueous electrolytes used are non-aqueous solutions in which lithium salts such as LiBF, LiPF, LiClO, LiN(SOCF), and LiN(SOCFCF) are dissolved in an aprotic organic solvent (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).

[0005] On the other hand, non-aqueous electrolytes containing dissolved electrolytes such as LiBF4 and LiPF6 are known to have high conductivity, which indicates the transport of lithium ions, and are stable at high voltages due to the high oxidative decomposition voltages of LiBF4 and LiPF6, which contribute to bringing out the high voltage and high energy density characteristics of lithium secondary batteries. When non-aqueous electrolyte secondary batteries such as lithium secondary batteries are used as power sources, it is required to reduce the electrical resistance of the non-aqueous electrolyte to increase the conductivity of lithium ions, and to suppress the decrease in battery capacity even after repeated charging and discharging, thereby maintaining a high capacity, thereby improving so-called cycle characteristics and extending the life.

[0006] To achieve this goal, it has been proposed to modify the structure of the lithium salt, which is the electrolyte contained in the non-aqueous electrolyte, or to add a specific compound. For example, Patent Document 3 proposes adding a vinyl sulfone derivative having a specific structure to the non-aqueous electrolyte. Furthermore, Patent Document 4 proposes adding a lithium salt other than a bifunctional acid lithium salt having a specific structure, which does not contain a boron atom.

[0007] Meanwhile, all-solid-state lithium batteries have been known that are free from concerns about battery fires due to flammable organic solvents in non-aqueous electrolytes, and amorphous compounds obtained by reacting lithium salts such as lithium sulfide with boron sulfide, phosphorus sulfide, silicon sulfide, or the like are known as lithium ion conductive solid electrolytes for these batteries (Patent Documents 5 and 6). However, these lithium compounds generally lack solubility in non-aqueous electrolytes, making them difficult to use as electrolytes for power storage devices. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 4-184872 [Patent Document 2] Japanese Patent Application Publication No. 10-27625 [Patent Document 3] Japanese Patent Application Publication No. 11-329494 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-22334 [Patent Document 5] Japanese Patent Application Publication No. 11-219722 [Patent Document 6] Japanese Patent Application Laid-Open No. 2003-68361 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide an electrolyte for an electricity storage device such as a lithium secondary battery, which can be used in place of a lithium salt, which is a known electrolyte in a non-aqueous electrolyte solution of an electricity storage device, or can be used in combination with a known lithium salt, and further can be used as an all-solid-state solid electrolyte that does not use a non-aqueous solvent and is free from the risk of fire or the like. Another object of the present invention is to provide an electricity storage device such as a non-aqueous electrolyte type or all-solid-state type lithium secondary battery using the above electrolyte, as well as the non-aqueous electrolyte and solid electrolyte used therein. [Means for solving the problem]

[0010] The present inventors have conducted extensive research and have found a novel electrolyte for use in electricity storage devices that can achieve the above-mentioned object. This electrolyte is soluble in non-aqueous solvents for electricity storage devices such as lithium ion secondary batteries, and therefore a non-aqueous electrolyte solution with low electrical resistance can be obtained, and a lithium secondary battery with good initial characteristics and excellent cycle characteristics can be obtained. Furthermore, the present inventors have found that the electrolyte itself has excellent lithium ion conductivity, and therefore an all-solid-state lithium secondary battery can be obtained. This finding led to the present invention.

[0011] The present invention provides an electrolyte for an electricity storage device, characterized by containing a lithium-containing complex compound represented by the following formula (1), formula (2), formula (3), formula (4) or formula (5). (Li) m (A) n (UFx ) y (1) (Li) m (Si) n (O) q (UF x ) y (2) (In the formula, A is O, S, P, or N. U is a boron atom or a phosphorus atom. m and n each independently represent 1 to 6. q is 1 to 12. x is 3 or 5. y is 1 to 6.) (Li) m (O) n (B) p (OWF q ) x (3) (In the formula, W is a boron atom or a phosphorus atom; m, p, and x each independently represent an integer of 1 to 15; n represents an integer of 0 to 15; and q represents an integer of 3 or 5.) (Li) m (B) p (O)n(OR) y (OWF q ) x (4) (In the formula, W is a boron atom or a phosphorus atom; n is 0 to 15; p, m, x, and y each independently are 1 to 12; and q is 3 or 5. R is a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a carbonyl group, a sulfonyl group, or a silyl group, and these groups may have a fluorine atom, an oxygen atom, or other substituents.) (Li) m (O) n (B) p (OOC-(A) z -COO) y (OWF q ) x (5) (In the formula, W is a boron atom or a phosphorus atom. A is an alkylene group, alkenylene group, or alkynylene group having 1 to 6 carbon atoms, a phenylene group, or an alkylene group having an oxygen atom or a sulfur atom in the main chain. m, p, x, and y each independently are 1 to 20. n is 0 to 15. z is 0 or 1. q is 3 or 5.) [Effects of the Invention]

[0012] The electrolyte for an electricity storage device of the present invention has solubility in organic solvents for electricity storage devices such as lithium ion secondary batteries, and therefore a nonaqueous electrolyte solution having low electrical resistance can be obtained, and an electrolyte for an electricity storage device such as a lithium secondary battery having good initial characteristics and excellent cycle characteristics can be obtained.Furthermore, since the electrolyte itself has excellent lithium ion conductivity, an all-solid-state lithium secondary battery can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Electrolyte> The present invention provides an electrolyte for an electricity storage device, characterized by containing a lithium-containing complex compound represented by the following formula (1), formula (2), formula (3), formula (4) or formula (5). (Li) m (A) n (UF x ) y (1) (Li) m (Si) n (O) q (UF x ) y (2) (In the formula, A, U, m, n, q, x, and y are defined as above.) (Li) m (O) n (B) p (OWF q ) x (3) (In the formula, W, m, p, x, n, and q are defined as above.) (Li) m (B) p (O)n(OR) y (OWF q ) x (4) (In the formula, W, R, n, p, m, x, y, and q are defined as above.) (Li) m (O) n (B) p (OOC-(A) z -COO) y (OWF q )x (5) (In the formula, W, A, m, p, x, y, n, z, and q are defined as above.)

[0014] In the above formulas (1) and (2), A is preferably an oxygen atom, a sulfur atom, a phosphorus atom, or a nitrogen atom, and more preferably an oxygen atom or a sulfur atom, because it is easy to form a stable lithium salt and has good solubility in a solvent. U is preferably a boron atom, a phosphorus atom, or an arsenic atom, and more preferably a boron atom or a phosphorus atom, because it is easy to form a bond with an oxygen atom, a sulfur atom, or a nitrogen atom.

[0015] Among these, m and n are preferably 1 to 6, and particularly preferably 2 to 6. Among these, q is preferably 2 to 8, and particularly preferably 3 to 8, for the reason of solubility of the electrolyte in the solvent. Among these, x is preferably 3 or 5 for the reason of solubility in the electrolyte solvent. Among these, y is preferably 1 to 6, and particularly preferably 1 to 5, because it is easy to form a bond with an oxygen atom, a sulfur atom, a phosphorus atom, or a nitrogen atom.

[0016] Examples of the lithium-containing complex compound include O-(BF3Li)(Li), O-(BF3Li)2, S-(BF3Li)(Li), S-(BF3Li)2, N-(BF3Li)2(Li), N-(BF3Li)3, P-(BF3Li)2(Li), P-(BF3Li)3, SiO3(BF3Li)(Li), SiO3(BF3Li)2, O-(PF5Li)(Li), O-(PF5Li)2, S-(PF5Li)(Li), or S-(PF5Li)2. For convenience, the lithium-containing complex compound is described as above. For example, O-(BF3Li)(Li) is Li-O(-BF3 - Li + ) complexes with the structure, and others are similar.

[0017] Of these, the lithium-containing complex compound is preferably O-(BFLi)(Li), O-(BFLi)2, S-(BFLi)(Li), S-(BFLi)2, N-(BFLi)3, P-(BFLi)3, SiO3(BFLi)(Li), or SiO3(BFLi)2, and O-(BFLi)(Li), O-(BFLi)2, S-(BFLi)(Li), S-(BFLi)2, SiO3(BFLi)(Li), SiO3(BFLi)2, O-(PFLi)(Li), O-(PFLi)2, S-(PFLi)(Li), or S-(PFLi)2, or N-(PFLi)3 is particularly preferred, due to the stability of the lithium-containing complex compound and its solubility in a solvent.

[0018] The lithium-containing complex compound is obtained by reacting a lithium compound (A) represented by the following formula (6) or (7) with one or more boron fluoride compounds (B) selected from the group consisting of boron trifluoride and boron trifluoride complexes or one or more phosphorus fluoride compounds (C) selected from the group consisting of phosphorus pentafluoride and phosphorus pentafluoride complexes: (Li) m (A) n (6) (Li) m (Si) n (O) q (7) In formula (6) and formula (7), A, m, n, and q are defined the same as in formula (1) and formula (2) above, and the preferred values ​​are also the same.

[0019] Examples of the lithium compound (A) represented by formula (3) include lithium oxide, lithium carbonate, lithium sulfide, lithium phosphide, lithium nitride, etc. Of these, lithium oxide, lithium carbonate, and lithium sulfide are preferred.

[0020] Examples of the lithium compound (A) represented by formula (6) include chain lithium inosilicates such as lithium silicate, lithium metasilicate, and lithium disilicate, cyclic lithium cyclosilicate, layered lithium phyllosilicate, and three-dimensional lithium tectosilicate, etc. Among these, lithium silicate, lithium metasilicate, and lithium disilicate are preferred.

[0021] The boron fluoride compound (B) may be boron trifluoride or a boron trifluoride complex. The boron trifluoride complex is formed from the boron atom of boron trifluoride and the oxygen of an oxygen-containing compound, and is obtained by contacting boron trifluoride with an oxygen-containing compound. Examples of the oxygen-containing compound include water, methanol, ethanol, propanol, butanol, phenol, tetrahydrofuran, dimethyl ether, diethyl ether, dibutyl ether, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0022] Specific examples of the boron fluoride compound (B) include boron trifluoride, boron trifluoride dimethyl ether complex, boron trifluoride diethyl ether complex, boron trifluoride di-n-butyl ether complex, boron trifluoride di-tert-butyl ether complex, boron trifluoride tert-butyl methyl ether complex, boron trifluoride tetrahydrofuran complex, boron trifluoride methanol complex, boron trifluoride ethanol complex, boron trifluoride propanol complex, boron trifluoride butanol complex, boron trifluoride phenol complex, boron trifluoride ethylene carbonate complex, boron trifluoride ethyl methyl carbonate complex, boron trifluoride dimethyl carbonate complex, and boron trifluoride diethyl carbonate complex. Among these, boron trifluoride, boron trifluoride dimethyl ether complex, boron trifluoride diethyl ether complex, boron trifluoride methanol complex, boron trifluoride ethanol complex, boron trifluoride propanol complex, and the like are preferred.

[0023] The phosphorus pentafluoride compound (C) may be phosphorus pentafluoride or a phosphorus pentafluoride complex. The phosphorus pentafluoride complex is formed from phosphorus pentafluoride and oxygen from an oxygen-containing compound, and is obtained by contacting phosphorus pentafluoride with the oxygen-containing compound. Specific examples of the phosphorus pentafluoride compound (C) include phosphorus pentafluoride, phosphorus pentafluoride ethylene carbonate complex, phosphorus pentafluoride dimethyl methyl carbonate complex, phosphorus pentafluoride diethyl methyl carbonate complex, and phosphorus pentafluoride ethyl methyl carbonate complex. Among these, phosphorus pentafluoride, phosphorus pentafluoride dimethyl methyl carbonate complex, phosphorus pentafluoride diethyl methyl carbonate complex, and phosphorus pentafluoride ethyl methyl carbonate complex are preferred.

[0024] The lithium-containing complex compound can be obtained by contacting a lithium compound (A) with a boron fluoride compound (B) and / or a phosphorus fluoride compound (C) preferably in an inert atmosphere and reacting them at a temperature of preferably 0 to 80° C., more preferably 10 to 30° C. The solvent is not limited as long as it is inert to the reaction, and examples thereof include water, methanol, ethanol, propanol, butanol, phenol, tetrahydrofuran, dimethyl ether, diethyl ether, dibutyl ether, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0025] Specifically, for example, to a solution obtained by dissolving or dispersing a boron fluoride compound (B) and / or a phosphorus fluoride compound (C) in a solvent such as methanol, the lithium compound (A) is gradually added in an inert gas atmosphere such as argon, preferably at 0 to 50° C. The reaction is then carried out by stirring for 1 to 24 hours, preferably at 30 to 80° C. The reaction solution is concentrated to remove the solvent, methanol, to obtain a crude lithium-containing complex compound. The resulting crude lithium-containing complex compound is washed with ether or the like, and the resulting purified product is dried under reduced pressure to obtain a highly pure lithium-containing complex compound.

[0026] On the other hand, in formulas (3), (4), and (5), a complex bond can be formed with W via oxygen atoms bonded to some of the boron atoms, forming a stable boron-containing complex compound. Some or all of the boron atoms in the lithium-containing boron complex compound can form a complex. While the bonding form is not limited here, it is preferable that one or more W atoms are bonded to the eight boron atoms from the viewpoint of solubility in a solvent. Furthermore, one or more W atoms can form a complex bond on the same boron atom.

[0027] Among these, W is preferably a boron atom, a phosphorus atom, or an arsenic atom, and more preferably a boron atom or a phosphorus atom, because it easily forms a bond with an oxygen atom.Furthermore, the ratio of the number of moles of W to the number of moles of lithium atoms in the lithium-containing boron complex compound is preferably 30 to 100. Among these, A is preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkenylene group having 2 to 6 carbon atoms or an alkynylene group having 2 to 6 carbon atoms. Preferred examples of the alkylene group include methylene, ethylene, difluoromethylene, tetrafluoroethylene, hydroxyethylene, propylene, butylene, cyclopropylene, cyclobutylene, cyclohexylene, etc. Preferred examples of the alkylene group having an oxygen atom or a sulfur atom in the main chain are those in which an alkylene group having 1 to 4 carbon atoms is bonded to the oxygen atom or sulfur atom. Preferred examples of the alkenylene group include vinylene, propenylene, butenylene, pentenylene, etc. In particular, an alkenylene group having a double bond and 2 to 6 carbon atoms is preferred. Preferred examples of the alkynylene group include ethynylene, propynylene, butynylene, pentynylene, etc. In particular, an alkynylene group having 3 to 6 carbon atoms is preferred. Preferred examples of the phenylene group include phenylene and difluorophenylene. In formula (3), when A is an alkylene group, an alkenylene group, an alkynylene group, a phenylene group, or an alkylene group having an oxygen atom or a sulfur atom in the main chain, the hydrogen atoms of these groups may be optionally substituted with halogen, a hydroxyl group, a cyano group, a nitro group, or the like.

[0028] R is preferably an alkyl group, an alkenyl group, an aryl group, a carbonyl group, a sulfonyl group, a silyl group, a boron-containing group, or a phosphorus-containing group, and particularly preferably an alkyl group, a carbonyl group, a sulfonyl group, a phenyl group, a silyl group, a boron-containing group, or a phosphorus-containing group. n is preferably 0 to 15, and m, p, and y are each preferably 1 to 20, and particularly preferably 1 to 12. q is preferably 3 or 5. x is preferably 1 to 8, and particularly preferably 2 to 8, in view of the solubility of the electrolyte in the solvent.

[0029] Examples of the lithium-containing boron complex compound represented by the above formula (3) include BO(OBF3Li), B4O5(OBF3Li)2, LiB4O6(OBF3Li), and BO 13 (OBF3Li)4, B6O9(OBF3Li)2, B8O9(OBF3Li)2, B5O7(OBF3Li), B7O 10 (OBF3Li), BO(OBF3Li)3, LiBO(OBF3Li)2, Li2BO2(OBF3Li), B2O(OBF3Li)4, Li2B2O3(OBF3Li)2, B3O7(OBF3Li)5, B4O3(OBF3Li) 6, Li2B4O5(OBF3Li)4, Li2B2O(OBF3Li)6, Li3B2O2(OBF3Li)5, Li4B2O3(OBF3Li)4, Li5B2O4(OBF3Li)3, Li6B2O5(OBF3Li)2, Li2B 6O 7(OBF3Li)6, Li4B6O9(OBF3Li)4.

[0030] Examples of the lithium-containing boron complex compound represented by the above formula (4) include B(OC(=O)CH3)2(OBF3Li), B(OC(=O)CF3)2(OBF3Li), B2O(OCH3)2(OBF3Li)2, B2O(OCH2CH3)2(OBF3Li)2, B2O(OCF2CF3)2(OBF3Li)2, and B2O(OC(=O)CH3)2(OB F3Li)2, B2O(OC(=O)CF3)2(OBF3Li)2, LiB2O2(OC(=O)CF3)2(OBF3Li), B2O(OSO2CH3)2(OBF3Li) 2, B2OOSO2CF3)2(OBF3Li)2, LiB2O2(OSO2CF3)2(OBF3Li), and B2O(OSi(CH3)3)2(OBF3Li)2.

[0031] Examples of the lithium-containing boron complex compound represented by the above formula (5) include BO(OOC-COO)(OBF3Li), BO(OOCCH2COO)(OBF3Li), BO(OOC(CH2)2COO)(OBF3Li), BO(OOC(CF2)2COO)(OBF3Li), BO(OOC(CH2)3COO)(OBF3Li), BO(OOC(CH2C(=CH2))COO)(OBF3Li), BO(OOC(C(CH2)3)COO)(OBF3Li), BO(OOCCH2OCH2COO)(OBF3Li), BO(OOCCH2SCH2COO)(OBF3Li), BO(OOCC2H4SC2H4COO)(OBF3Li), BO4O3(O OC-COO)2(OBF3Li)2, lib4O4(OOC-COO)2(OBF3Li), B4O3(OOCCH2COO)2(OBF3Li)2, B4O3 (OOCCH2SCH2COO)2(OBF3Li)2, LiB4O4(OOCCH2SCH2COO)2(OBF3Li), B4O3(OOC(CH2C(=CH 2))COO)2(OBF3Li)2, Li2B2O(OOC-COO)2(OBF3Li)2, Li2B2O(OOCCH2COO)2(OBF3Li)2, Li Examples include 2B2O(OOCCH2SCH2COO)2(OBF3Li)2, Li2B2O(OOC(CH2C(=CH2))COO)2(OBF3Li)2, and the like. The above expression of the lithium-containing boron complex compound does not indicate the bonding structure of the complex, but the element ratio is described as above for convenience.

[0032] The content of the lithium-containing boron complex compound in the nonaqueous electrolyte solution of the present invention is preferably 0.01 to 30% by mass, more preferably 0.1 to 25% by mass, and particularly preferably 0.1 to 5% by mass. If the concentration is less than 0.01% by mass, the resistance-reducing effect is reduced. On the other hand, if the concentration exceeds 30% by mass, the resistance component increases, resulting in a shortened lifespan, which is undesirable.

[0033] The lithium-containing boron complex compound is obtained by reacting a lithium-containing boron compound (D) represented by the following formula (8), formula (9), or formula (10) with one or more boron fluoride compounds (E) selected from the group consisting of boron trifluoride and boron trifluoride complexes, or one or more phosphorus fluoride compounds (F) selected from the group consisting of phosphorus pentafluoride and phosphorus pentafluoride complexes. (Li)m(B)p(O)n (8) (Li)m(B)p(O)n(OR)y (9) (Li) m [(-O-) n B(OOC-(A)z-COO) p ] x [B(-O-) q ] y (10) In formulas (8), (9), and (10), A, R, m, n, p, q, x, y, and z are defined as in formulas (3), (4), and (5), respectively, and the preferred values ​​are also the same.

[0034] In the lithium-containing boron compound represented by formula (8), m, p, and n are each independently 1-20. Preferred specific examples of the lithium-containing boron compound represented by formula (8) include LiBO2, Li2B4O7, and Li4B8O 17 , Li2B6O 11 , Li2B8O 11 , LiB5O8, LiB7O11 , Li3BO3, Li4B2O5, Li5B3O7, Li6B4O9, Li8B2O7, Li8B6O 13 etc.

[0035] In the lithium-containing boron compound represented by formula (9), n, m, x, and y are each independently 1 to 12, and R is hydrogen, an alkyl group, an alkenyl group, an aryl group, a carbonyl group, a sulfonyl group, or a silyl group, and these groups may have a fluorine atom, an oxygen atom, or other substituents. R is preferably an alkyl group, an alkenyl group, an aryl group, a carbonyl group, a sulfonyl group, a silyl group, a boron-containing group, or a phosphorus-containing group, and particularly preferably an alkyl group, a carbonyl group, a sulfonyl group, a phenyl group, a silyl group, a boron-containing group, or a phosphorus-containing group.

[0036] The alkyl group is preferably a linear or cyclic alkyl group having 1 to 8 carbon atoms. Examples of the linear or cyclic alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a cyclopropyl group, a cyclobutyl group, a cyclohexyl group, a hydroxyethyl group, a trifluoromethyl group, and a hexafluoroethyl group. The alkenyl group is preferably an alkenyl group containing a double bond and having 2 to 5 carbon atoms, and examples thereof include a vinyl group, a propenyl group, a butenyl group, and a heptenyl group.

[0037] Preferred examples of the aryl group include a phenyl group, a benzyl group, a tolyl group, and a xylyl group. Preferred examples of the carbonyl group include a methylcarbonyl group, an ethylcarbonyl group, a propylcarbonyl group, a butylcarbonyl group, a cyclopropylcarbonyl group, a cyclobutylcarbonyl group, a trifluoromethylcarbonyl group, and a pentafluoroethylcarbonyl group.

[0038] Preferred examples of the sulfonyl group include a methylsulfonyl group, an ethylsulfonyl group, a propylsulfonyl group, a benzylsulfonyl group, a trifluoromethylsulfonyl group, and a pentafluoroethylsulfonyl group. Preferred examples of the silyl group include a trimethylsilyl group, a triethylsilyl group, a triisopropylsilyl group, and a butyldimethylsilyl group. Preferred examples of the boron-containing group include a dimethylboryl group and a dimethoxyboryl group.

[0039] Preferred specific examples of the lithium boron compound represented by formula (9) include LiBO(OC(=O)CH3)2, LiBO(OC(=O)CF3)2, Li2B2O3(OCH3)2, Li2B2O3(OCH2CH3)2, Li2B2O3(OCF2CF3)2, Li2B2O3(OC(=O)CH3)2, Li2B2O3(OC(=O)CF3)2, Li2B2O3(OSO2CH3)2, Li2B2O3(OSO2CF3)2, Li2B2O3(OSi(CH3)3)2, etc.

[0040] In the lithium-containing boron compound represented by formula (10), A is an alkylene group, alkenylene group, or alkynylene group having 1 to 6 carbon atoms, a phenylene group, or an alkylene group having an oxygen atom or a sulfur atom in the main chain. n and p each independently represent 1 or 2, q represents 0 to 3, and m, x, y, and z each independently represent 0 to 10. Among these, A is preferably an alkylene group, alkenylene group or alkynylene group having preferably 1 to 6 carbon atoms, more preferably 2 to 6 carbon atoms. Preferred examples of the alkylene group include methylene, ethylene, tetrafluoroethylene, hydroxyethylene, propylene, butylene, cyclopropylene, cyclobutylene, cyclohexylene, and the like.

[0041] The alkenylene group is preferably an alkenylene group having a double bond containing 2 to 5 carbon atoms. Examples of alkenylene groups having a double bond containing 2 to 4 carbon atoms include vinylene, propenylene, butenylene, and pentenylene. Preferred examples of the phenylene group include phenylene, difluorophenylene, etc. Preferred examples of the alkylene group having an oxygen atom or a sulfur atom in the main chain are those in which an alkylene group having 1 to 4 carbon atoms is bonded to the oxygen atom or sulfur atom, and examples of the alkylene group include methylene, ethylene, tetrafluoroethylene, propylene, butylene, cyclopropylene, cyclobutylene, etc.

[0042] When A is an alkylene group, an alkenylene group, an alkynylene group, a phenylene group, or an alkylene group having an oxygen atom or a sulfur atom in the main chain, the hydrogen atoms of these groups may be optionally substituted with halogen, a hydroxyl group, a cyano group, a nitro group, or the like. In the formula (6), n and p are each independently preferably 1 or 2, and m, x, y, and z are each independently preferably 0 to 10.

[0043] Preferred specific examples of the lithium boron compound include LiBO(OOC-COO), LiBO(OOCCH2COO), LiBO(OOC(CH2)2COO), LiBO(OOC(CF2)2COO), LiBO(OOC(CH2)3COO), LiBO(OOC(CH2C(=CH2))COO), LiBO(OOC(C(CH2)3)COO), LiBO(OOCCH2OCH2COO), LiBO(OOCCH2SCH2COO), LiBO( OOCC2H4SC2H4COO), Li2B4O5(OOC-COO)2, Li2B4O5(OOCCH2COO)2, Li2B4O5(OOCCH2SCH2COO)2, Li2B4O5(OOC(CH2C(=CH2))COO)2, Li4B2O3(OOC-COO)2, Li4B2O3(OOCCH2COO)2, Li4B2O3(OOCCH2SCH2COO)2, Li4B2O3(OOC(CH2C(=CH2))COO)2.

[0044] The lithium boron compound can be easily obtained by the same production method as for lithium salts such as lithium tetraborate. For example, precursor crystals can be easily obtained by keeping an aqueous solution of boric acid, a lithium compound such as lithium hydroxide or lithium carbonate, and the corresponding carboxylic acid compound at 20 to 80°C. The obtained crystals are dehydrated under conditions of 200 to 400°C, and the lithium boron compound can be suitably obtained.

[0045] The boron fluoride compound (E) may be boron trifluoride or a boron trifluoride complex. The boron trifluoride complex is formed from the boron atom of boron trifluoride and the oxygen of an oxygen-containing compound, and is obtained by contacting boron trifluoride with an oxygen-containing compound. Examples of the oxygen-containing compound include water, methanol, ethanol, propanol, butanol, phenol, tetrahydrofuran, dimethyl ether, diethyl ether, dibutyl ether, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl butyl carbonate.

[0046] The phosphorus pentafluoride compound (F) may be phosphorus pentafluoride or a phosphorus pentafluoride complex, which is formed from phosphorus pentafluoride and oxygen from an oxygen-containing compound and is obtained by contacting phosphorus pentafluoride with the oxygen-containing compound. Specific examples of the phosphorus pentafluoride compound (F) include phosphorus pentafluoride, phosphorus pentafluoride ethylene carbonate complex, and phosphorus pentafluoride ethyl methyl carbonate complex, of which phosphorus pentafluoride and phosphorus pentafluoride ethyl methyl carbonate complex are preferred.

[0047] The lithium-containing boron complex compound can be obtained by contacting a lithium-containing boron compound (D) with a boron fluoride compound (E) and / or a phosphorus fluoride compound (F) preferably in an inert atmosphere and reacting them at a temperature of preferably 0 to 80° C., more preferably 10 to 30° C. The solvent is not limited as long as it is inert to the reaction, and examples thereof include water, methanol, ethanol, propanol, butanol, phenol, tetrahydrofuran, dimethyl ether, diethyl ether, dibutyl ether, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl butyl carbonate.

[0048] Specifically, for example, to a solution obtained by dissolving or dispersing a boron fluoride compound (E) and / or a phosphorus fluoride compound (F) in a solvent such as methanol, the lithium-containing boron compound (D) is gradually added in an inert gas atmosphere such as argon, preferably at 0 to 50° C. The reaction is then carried out by stirring for 1 to 24 hours, preferably at 30 to 80° C. The reaction solution is concentrated to remove the solvent methanol, thereby obtaining a crude lithium-containing boron complex compound. The resulting crude lithium-containing boron complex compound is washed with ether or the like, and the resulting purified product is dried under reduced pressure to obtain a highly pure lithium-containing boron complex compound.

[0049] <Non-aqueous solvent> When the electrolyte of the present invention is used as a non-aqueous electrolyte, various organic solvents can be used as the non-aqueous solvent. For example, aprotic polar solvents are preferred. Specific examples thereof include cyclic carbonates such as 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 4,5-difluoroethylene carbonate; lactones such as γ-butyrolactone 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, and methyl isopropyl carbonate. Examples of the fluorine-containing ethers include chain carbonates such as methyl ether, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl 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; and fluorine-containing ethers such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3,3-pentafluoropropyl ether, and ethoxy-2,2,2-trifluoroethoxyethane. These may be used alone or in combination of two or more.

[0050] As the non-aqueous solvent, from the viewpoint of ionic conductivity, it is more preferable to use a carbonate-based solvent such as a cyclic carbonate or a chain carbonate. As the carbonate-based solvent, it is even more preferable to use a combination of a cyclic carbonate and a chain carbonate. Among the above, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are preferred as the cyclic carbonate. Among the above, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate are preferred as the chain carbonate. When a carbonate-based solvent is used, another non-aqueous solvent such as a nitrile-based compound or a sulfone-based solvent can be further added as necessary to improve the battery properties.

[0051] The non-aqueous solvent preferably contains a chain carbonate, a saturated cyclic carbonate, and an unsaturated cyclic carbonate. It is particularly preferable to contain these three types of carbonate. The non-aqueous solvent preferably contains 30 to 80 wt %, 10 to 50 wt %, and 0.01 to 5 wt % of the chain carbonate, saturated cyclic carbonate, and unsaturated cyclic carbonate in the non-aqueous electrolyte, respectively, and more preferably contains 50 to 70 wt %, 20 to 30 wt %, and 0.1 to 2 wt %, respectively.

[0052] If the chain carbonate ester is less than 30% by weight, the viscosity of the electrolyte increases and solidifies at low temperatures, making it impossible to obtain sufficient properties. Conversely, if it is more than 80% by weight, the dissociation / solubility of the lithium salt decreases, reducing the ionic conductivity of the electrolyte. If the saturated cyclic carbonate ester is less than 10% by weight, the dissociation / solubility of the lithium salt decreases, reducing the ionic conductivity of the electrolyte. Conversely, if it is more than 50% by weight, the viscosity of the electrolyte increases and solidifies at low temperatures, making it impossible to obtain sufficient properties.

[0053] Furthermore, if the unsaturated cyclic carbonate content is less than 0.01% by weight, a good coating film will not be formed on the surface of the negative electrode, resulting in a deterioration in cycle characteristics. Conversely, if the content is more than 5% by weight, the electrolyte will be prone to gas generation during high-temperature storage, resulting in an increase in the pressure inside the battery, which is undesirable for practical use.

[0054] Examples of chain carbonate esters include chain carbonates having 3 to 9 carbon atoms. Specific examples include 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, Examples of suitable carbonates include 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-propyl 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 preferred, but are not particularly limited. Two or more of these chain carbonates may be mixed.

[0055] Examples of saturated cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate. Among these, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are more preferred, and the use of propylene carbonate can provide a stable nonaqueous electrolyte solution over a wide temperature range. Two or more of these saturated cyclic carbonates may be mixed.

[0056] Furthermore, examples of the unsaturated cyclic carbonate include vinylene carbonate derivatives represented by the following general formula (I). [ka] In the general formula (I), R1 and R2 are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 12 carbon atoms and optionally containing a halogen atom. Of these, it is preferable that R1 and R2 are hydrogen (vinylene carbonate).

[0057] Specific examples of the vinylene carbonate derivatives include, but are not limited to, the following compounds: vinylene carbonate, fluorovinylene carbonate, methylvinylene carbonate, fluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, butylvinylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate, and dipropylvinylene carbonate. Among these, vinylene carbonate is effective and advantageous in terms of cost. At least one of the vinylene carbonate derivatives is used, and they may be used alone or in combination. Another example of the unsaturated cyclic carbonate is alkenyl ethylene carbonate represented by the following general formula (II).

[0058] [ka]

[0059] In the above formula (II), R3 to R6 are each independently a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms which may contain a halogen atom, or an alkenyl group having 2 to 12 carbon atoms, at least one of which is an alkenyl group having 2 to 12 carbon atoms. In particular, when one of R3 to R6 is a vinyl group and the rest are hydrogen, specific examples of the alkenyl ethylene carbonate include compounds such as 4-vinyl ethylene carbonate, 4-vinyl-4-methyl ethylene carbonate, 4-vinyl-4-ethyl ethylene carbonate, and 4-vinyl-4-n-propyl ethylene carbonate.

[0060] The non-aqueous solvent may contain various other solvents in addition to the above components. Examples of these various other solvents include cyclic carboxylic acid esters, chain esters having 3 to 9 carbon atoms, and chain ethers having 3 to 6 carbon atoms. These various other solvents are contained in the non-aqueous electrolyte preferably in an amount of 0.2 to 10 wt %, and particularly preferably in an amount of 0.5 to 5 wt %.

[0061] Examples of cyclic carboxylic acid esters (lactone compounds having 3 to 9 carbon atoms) include γ-butyrolactone, γ-valerolactone, γ-caprolactone, and ε-caprolactone. Among these, γ-butyrolactone and γ-valerolactone are more preferred. Two or more of these cyclic carboxylic acid esters may be mixed.

[0062] Examples of chain esters having 3 to 9 carbon atoms include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, isobutyl propionate, and t-butyl propionate. Of these, ethyl acetate, methyl propionate, and ethyl propionate are preferred.

[0063] Furthermore, examples of chain ethers having 3 to 6 carbon atoms include dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, ethoxymethoxyethane, etc. Among these, dimethoxyethane and diethoxyethane are more preferable.

[0064] Additionally, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, and the like can be used.

[0065] <Lithium salt> The non-aqueous electrolyte may contain a conventionally known lithium salt dissolved therein together with the electrolyte of the present invention. Specific examples of such lithium salts are as follows: (A) Inorganic lithium salt: Inorganic fluoride salts such as LiPF6, LiAsF6, LiBF4, etc., perhalogenates such as LiClO4, LiBrO4, LiIO4, etc.

[0066] (B) Organic lithium salts: Organic sulfonates such as LiCF3SO3; perfluoroalkylsulfonate imide salts such as LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2)(C4F9SO2); perfluoroalkylsulfonate methide salts such as LiC(CF3SO2)3; LiPF(CF3)5, LiPF2(CF3)4, LiPF3(CF3)3, LiPF2(C2F5)4, LiPF3(C2F5)3, LiPF(n-C3F7)5, LiPF2(n-C3F7)4, LiPF3(n-C3F7)3, LiPF(iso-C3F7)5, LiPF2(iso-C3F7)4, LiPF3(iso-C3F73, LiB Examples include inorganic fluoride salt fluorophosphates in which some of the fluorine atoms are substituted with perfluoroalkyl groups, such as (CF3)4, LiBF(CF3)3, LiBF2(CF3)2, LiBF3(CF3), LiB(C2F5)4, LiBF(C2F5)3, LiBF2(C2F5)2, LiBF3(C2F5), LiB(n-C3F7)4, LiBF(n-C3F7)3, LiBF2(n-C3F7)2, LiBF3(n-C3F7), LiB(iso-C3F7)4, LiBF(iso-C3F7)3, LiBF2(iso-C3F7)2, and LiBF3(iso-C3F7), and fluorine-containing organic lithium salts of perfluoroalkyl groups.

[0067] Among the above, LiPF6, LiBF4, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2)(C2F5SO2) or LiN(CF3SO2)(C4F9SO2) are more preferred. Two or more of these lithium salts may be mixed.

[0068] The content of the electrolyte of the present invention in the nonaqueous electrolyte is preferably 0.01 to 10 mol / L, particularly preferably 0.01 to 3.0 mol / L. If this concentration is too low, the ionic conductivity of the nonaqueous electrolyte will be insufficient due to an absolute lack of concentration, whereas if the concentration is too high, the ionic conductivity will decrease due to an increase in viscosity, and problems such as increased susceptibility to precipitation at low temperatures will arise, undesirably reducing the performance of the nonaqueous electrolyte battery.

[0069] Furthermore, when the non-electrolyte contains the known lithium compound described above, the lithium salt is preferably present in the non-aqueous electrolyte at a concentration of 0.5 to 3 mol / L, particularly 0.7 to 2 mol / L. If this concentration is too low, the ionic conductivity of the non-aqueous electrolyte will be insufficient due to an absolute lack of concentration, whereas if the concentration is too high, the ionic conductivity will decrease due to an increase in viscosity, and problems such as increased susceptibility to precipitation at low temperatures will also occur, resulting in a decrease in the performance of the non-aqueous electrolyte battery, which is undesirable.

[0070] <Other additives> In addition to the lithium salt and lithium boron compound, the nonaqueous electrolyte may contain other additives to improve the life and resistance of the power storage device, such as at least one selected from the group consisting of sulfur-containing compounds, cyclic acid anhydrides, carboxylic acid compounds, and boron-containing compounds.

[0071] Examples of the sulfur-containing compound include 1,3-propane sultone (PS), propene sultone, ethylene sulfite, hexahydrobenzo[1,3,2]dioxathiolane-2-oxide (also known as 1,2-cyclohexanediol cyclic sulfite), 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, 1,4-butanediol dimethanesulfonate, 1,3-butanediol dimethanesulfonate, methylenemethane disulfonic acid, ethylenemethane disulfonic acid, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide, divinyl sulfone, and 1,2-bis(vinylsulfonyl)methane.

[0072] Examples of the cyclic acid anhydrides 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-phenylglutaric anhydride, phthalic anhydride, pyromellitic anhydride, fluorosuccinic anhydride, and tetrafluorosuccinic anhydride. Examples of the sulfonic anhydride include carboxylic acid anhydrides such as 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfonic anhydride, 1,4-butanedisulfonic anhydride, 1,2-benzenedisulfonic anhydride, tetrafluoro-1,2-ethanedisulfonic anhydride, hexafluoro-1,3-propanedisulfonic anhydride, octafluoro-1,4-butanedisulfonic anhydride, 3-fluoro-1,2-benzenedisulfonic anhydride, 4-fluoro-1,2-benzenedisulfonic anhydride, and 3,4,5,6-tetrafluoro-1,2-benzenedisulfonic anhydride.

[0073] 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, lithium oxalacetate, lithium 2-oxoglutarate, lithium acetoacetate, 3-oxocyclobutanecarboxylic acid, 3-oxocyclopentanecarboxylic acid, lithium 2-oxovalerate, lithium pyruvate, lithium glyoxylate, and lithium 3, Examples of such an acid include lithium 3-dimethyl-2-oxobutyrate, lithium 2-hydroxypropionate, lithium 2-methyllactate, lithium tartrate, lithium cyanoacetate, lithium 2-mercaptopropionate, lithium methylenebis(thioglycolic acid)thiodisuccinate, lithium 3-(methylthio)propionate, lithium 3,3'-thiodipropionate, lithium dithiodiglycolate, lithium 2,2'-thiodiglycolate, lithium thiazolidine-2,4-dicarboxylate, and lithium acetylthioacetate.

[0074] Examples of the boron-containing compounds include LiBF2(C2O4), LiB(C2O4)2, LiBF2(CO2CH2CO2), LiB(CO2CH2CO2)2, LiB(CO2CF2CO2)2, LiBF2(CO2CF2CO2), LiBF3(CO2CH3), LiBF3(CO2CF3), LiBF2(CO2CH3)2, LiBF2(CO2CF3)2, LiBF(CO2CH3)3, LiBF(CO2CF3)3, LiB(CO2CH3)4, LiB(CO2CF3)4, Li2B2O7, and Li2B2O4. The other additives mentioned above may be used alone or in combination of two or more. When the non-aqueous electrolyte contains an additive, the content thereof in the non-aqueous electrolyte is preferably 0.01 to 5 mass %, and more preferably 0.1 to 2 mass %.

[0075] <Electricity storage device> As described above, the electrolyte of the present invention can be used in both non-aqueous electrolyte-based electricity storage devices and all-solid-state electricity storage devices. Examples of electricity storage devices include various devices such as lithium (ion) secondary batteries, electric double-layer capacitors, and hybrid batteries in which one of the positive and negative electrodes is a battery and the other electrode is a double layer. The electrolyte of the present invention can be used in any of these electricity storage devices by known methods and systems. A typical example of such a battery is a non-aqueous electrolyte lithium ion secondary battery.

[0076] As the negative electrode active material constituting the negative electrode in a lithium ion secondary battery, any of the following can be used: a carbon material that can be doped / dedoped with lithium ions; metallic lithium; a lithium-containing alloy; silicon that can be alloyed with lithium; silicon alloy; tin; tin alloy; tin oxide; silicon oxide that can be doped / dedoped with lithium ions; a transition metal oxide that can be doped / dedoped with lithium ions; a transition metal nitrogen compound that can be doped / dedoped with lithium ions; or a mixture of these.

[0077] The negative electrode generally has a configuration in which a negative electrode active material is formed on a current collector such as copper foil or expanded metal, etc. To improve the adhesion of the negative electrode active material to the current collector, the negative electrode may contain, for example, a polyvinylidene fluoride binder or a latex binder, and may also contain, as a conductive additive, carbon black, amorphous whisker carbon, etc.

[0078] Examples of carbon materials constituting the negative electrode active material include pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, fired organic polymer compounds (phenolic resin, furan resin, etc., fired at an appropriate temperature to carbonize), carbon fiber, activated carbon, etc. The carbon material may be graphitized. As the carbon material, a carbon material having a (002) plane interplanar spacing (d002) of 0.340 nm or less as measured by X-ray diffraction and a true density of 1.70 g / cm3 is particularly preferred. 3 Graphite or a highly crystalline carbon material having similar properties to graphite is desirable. The use of such a carbon material can increase the energy density of a non-aqueous electrolyte battery.

[0079] Furthermore, the carbon material may contain boron, be coated with a metal such as gold, platinum, silver, copper, Sn, or Si, or be coated with amorphous carbon, etc. These carbon materials may be used alone or in combination of two or more.

[0080] Furthermore, when silicon, silicon alloys, tin, tin alloys that can be alloyed with lithium, tin oxide, silicon oxide that can be doped and dedoped with lithium ions, and transition metal oxides that can be doped and dedoped with lithium ions are used, they all have a higher theoretical capacity per weight than the above-mentioned carbonaceous materials and are therefore suitable materials.

[0081] 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 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. Examples include composite oxides of lithium and one or more transition metals (lithium transition metal composite oxides) represented by LixMO2 (where M is one or more transition metals, x varies depending on the charge / discharge state of the battery and is usually 0.05≦x≦1.20), such as LiCoO2, LiNiO2, LiMn2O4, and LiMnO2.

[0082] Furthermore, composite oxides in which some of the transition metal atoms that form the main part of the lithium transition metal composite oxides are substituted with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, and Yb, chalcogenides of transition elements such as FeS2, TiS2, V2O5, MoO3, and MoS2, and polymers such as polyacetylene and polypyrrole can be used. Of these, lithium transition metal composite oxides that can be doped and undoped with Li and metal composite oxide materials in which some of the transition metal atoms are substituted are preferred.

[0083] Furthermore, a substance having a different composition from the substance constituting the main positive electrode active material may be attached to the surface of the positive electrode active material. Examples of the surface-attached substance include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

[0084] The positive electrode generally has a configuration in which a positive electrode active material is formed on a current collector such as aluminum, titanium, or stainless steel foil, or expanded metal, etc. To improve the adhesion of the positive electrode active material to the current collector, the positive electrode may contain, for example, a polyvinylidene fluoride binder or a latex binder, or to improve the electronic conductivity within the positive electrode, carbon black, amorphous whiskers, graphite, etc.

[0085] The separator is preferably a membrane that electrically insulates the positive electrode and the negative electrode and is permeable to lithium ions, such as a porous membrane such as a microporous polymer film. As the microporous polymer film, a porous polyolefin film is particularly preferred, 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 preferred. Furthermore, a polymer electrolyte can also be used as the separator. Examples of the polymer electrolyte that can be used include, but are not limited to, polymeric substances in which lithium salts are dissolved and polymeric substances swollen with an electrolytic solution.

[0086] The non-aqueous electrolyte may be used for the purpose of swelling a polymeric substance with the non-aqueous electrolyte to obtain a polymer electrolyte, or the non-aqueous electrolyte may be impregnated into a separator in which a porous polyolefin film and a polymer electrolyte are combined. The shape of the lithium ion secondary battery using the nonaqueous electrolyte of the present invention is not particularly limited, and it can be in various shapes such as a cylindrical shape, a square shape, a laminated shape, a coin shape, or a button shape. [Example]

[0087] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples and can be modified within the scope of the present invention. <Battery construction> A flat wound electrode group in which the positive electrode and negative electrode described below were wound with a 23 μm thick separator (F23DHA, manufactured by Toray Battery Separator Film Co., Ltd.) interposed therebetween was housed in a case to produce a battery cell having a rectangular parallelepiped shape of 30 mm long x 30 mm wide x 2.0 mm thick. Positive electrode: 5% by mass of polyvinylidene fluoride as a binder, 4% by mass of acetylene black as a conductive agent, and LiNi as a positive electrode active material, which is a composite oxide powder of lithium, nickel, manganese, and cobalt. 0.6 Mn 0.2 Co 0.2 N-methylpyrrolidone was added to a positive electrode composite material prepared by mixing 91% by mass of O2 and the above to prepare a paste. This paste was then applied to both sides of an 18 μm-thick aluminum foil current collector, the solvent was dried off, and the current collector was then rolled using a roll press to produce a cathode.

[0088] Negative electrode: A slurry was 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 a 2.2% by mass aqueous solution of carboxymethyl cellulose, and using water as a dispersion medium. This slurry was applied to both sides of a 12 μm thick copper foil, the solvent was dried off, and then the foil was rolled using a roll press.

[0089] Using the battery cell produced above, a lithium ion secondary battery was produced according to the following steps a to c. a. 0.55 g of each electrolyte was weighed out and poured into the inlet of the battery cell. After the pressure was reduced, the inlet was sealed. b. The sealed battery cell was kept in an atmosphere of 25°C and charged to 4.2V at 8mA, and then discharged to 3.0V at 8mA. c. The internal gas of the battery cell discharged to 3.0 V was removed under reduced pressure to prepare a battery.

[0090] <Battery evaluation> The charge-discharge characteristics of the battery prepared above were measured as follows. a. Resistance change rate Before the high-temperature cycle test, the batteries were charged at 25°C to a SOC (State of Charge) of 50%, and then discharged for 10 seconds at 0.2C, 0.5C, 1.0C, and 2.0C under each environment to determine the initial DC resistance. The battery was charged to 4.2 V at a 1 C rate in a 45°C atmosphere, and then discharged to 3.0 V at a 1 C rate in the same atmosphere. This cycle was repeated until 200 cycles were reached, and the DC resistance after the cycles was determined under the same conditions as before the high-temperature cycle test. The resistance change rate (%) was calculated from the initial DC resistance and the DC resistance after the cycles using the following formula (1). Resistance change rate = (resistance value after cycling / initial resistance value) x 100 (1)

[0091] b.Capacity retention rate The battery was charged to 4.2 V at a 1 C rate in a 45°C atmosphere, and then discharged to 3.0 V at a 1 C rate in the same atmosphere. The discharge capacity value was recorded as the initial capacity value. The same conditions were then repeated until 200 cycles were reached. The capacity retention rate (%) was calculated from the initial capacity value and the capacity value after cycling using the following formula (2). Capacity retention rate = (capacity after cycling / initial capacity) x 100 (2) <Example A Series>

[0092] <Production Example 1> Under an argon atmosphere, 100 ml of methanol was placed in a 500 ml Erlenmeyer flask, and 30 g of lithium oxide was added, and the mixture was then cooled to 10° C. with stirring. Next, while maintaining the mixture at 10° C., 290 g of boron trifluoride methanol complex was added over 5 hours with stirring, and the reaction mixture was then maintained at 50° C. and stirred for 3 hours. The reaction mixture was then concentrated to remove the methanol, yielding a crude lithium oxide / 2BF3 complex. The resulting crude lithium oxide / 2BF3 complex was washed three times with 50 ml of dibutyl ether to remove excess boron trifluoride methanol complex. The resulting solid was then dried under reduced pressure at 110°C for 10 hours, yielding 157 g of lithium oxide / 2BF3 complex, O-(BF3Li)2. The solid obtained was analyzed using ICP, and the boron content was 99.5 relative to 100% lithium.

[0093] <Production Example 2> The same procedure as in Production Example 1 was carried out except that 132 g of boron trifluoride methanol complex was used instead of 290 g of boron trifluoride methanol complex, thereby obtaining 91 g of a lithium oxide / BF complex (O-(BFLi)(Li)). The solid obtained was analyzed using ICP, and the boron content was 48 parts by mass relative to 100 parts by mass of lithium.

[0094] <Production Example 3> Under an argon atmosphere, 100 ml of methanol was placed in a 500 ml Erlenmeyer flask, and 23 g of lithium sulfide was added thereto, and the mixture was then cooled to 10°C with stirring. Next, the mixture was kept at 10°C, and 155 g of boron trifluoride diethyl ether complex was added over 5 hours, and then the reaction mixture was kept at 50°C and stirred for 3 hours. Next, diethyl ether was removed from the reaction solution to obtain a crude lithium sulfide / 2BF3 complex. The obtained crude lithium sulfide / 2BF3 complex was washed three times, each with 50 ml of dibutyl ether. The obtained solid was then dried under reduced pressure at 110°C for 10 hours to obtain 87 g of lithium sulfide / 2BF3 complex (S-(BF3Li)2). Analysis of the obtained solid using ICP revealed that the boron content was 99.8 relative to 100% lithium.

[0095] <Production Example 4> Under an argon atmosphere, 53 g of lithium sulfide / BF complex (S-(BFLi)(Li)) was obtained by carrying out the same procedure as in Production Example 3, except that 76 g of boron trifluoride diethyl ether complex was used instead of 155 g of boron trifluoride diethyl ether complex. The solid obtained was analyzed using ICP, and the boron content was 51 parts per 100 parts of lithium.

[0096] <Production Example 5> 50 ml of methanol and 44 g of boron trifluoride methanol complex were placed in a 300 ml beaker to prepare a mixed solution. Next, this mixture was kept at 10° C. under an argon atmosphere, and 3.4 g of lithium nitride was added thereto over 5 hours with stirring. The reaction mixture was then concentrated to remove the methanol, yielding a crude lithium nitride / 3BF3 complex. The resulting crude lithium nitride / 3BF3 complex was washed three times, each with 20 ml of dibutyl ether. The resulting solid was then dried under reduced pressure at 110°C for 10 hours, yielding 18 g of lithium nitride / 3BF3 complex (N-(BF3Li)3). Analysis of the resulting solid using ICP revealed that the boron content was 98.5 relative to 100% lithium.

[0097] <Production Example 6> The same procedure as in Production Example 5 was carried out except that 29.5 g of boron trifluoride methanol complex was used instead of 44 g of boron trifluoride methanol complex, to obtain 14.5 g of lithium nitride / 2BF complex (N-(BFLi)(Li)). The solid obtained was analyzed using ICP, and the boron content was 68 relative to 100 for lithium.

[0098] <Production Example 7> A mixed solution was prepared by placing 50 ml of methanol and 44 g of boron trifluoride methanol complex in a 300 ml beaker. Next, this mixture was kept at 10°C under an argon atmosphere, and 5.2 g of trilithium phosphide was added over 5 hours while stirring. The reaction mixture was then concentrated to remove the methanol, yielding a crude lithium phosphide / 3BF3 complex. The resulting crude lithium phosphide / 3BF3 complex was washed three times with 20 ml of dibutyl ether. The resulting solid was then dried under reduced pressure at 110°C for 10 hours, yielding 19 g of lithium phosphide / 3BF3 complex (P-(BF3Li)3). Analysis of the resulting solid using ICP revealed that the boron content was 90:100 for lithium.

[0099] <Production Example 9> Under an argon atmosphere, 50 ml of methanol was placed in a 300 ml Erlenmeyer flask, and 27 g of lithium metasilicate was added thereto, and the mixture was then cooled to 10° C. with stirring. Next, the mixture was kept at 10°C, and 86 g of boron trifluoride methanol complex was added over 5 hours, and then the reaction mixture was kept at 50°C and stirred for 3 hours. Next, methanol was removed from the reaction solution to obtain a crude lithium metasilicate / 2BF3 complex. The obtained crude lithium metasilicate / 2BF3 complex was washed three times, each with 50 ml of dibutyl ether. The obtained solid was then dried under reduced pressure at 110°C for 10 hours to obtain 62 g of lithium metasilicate / 2BF3 complex (SiO3-(BF3Li)2). Analysis of the obtained solid using ICP revealed that the boron content was 99.5 relative to 100% lithium.

[0100] <Production Example 10> The same procedure as in Production Example 9 was carried out except that 43 g of boron trifluoride methanol complex was used instead of 86 g of boron trifluoride methanol complex, to obtain 14.5 g of lithium metasilicate / 2BF complex ((SiO-(BFLi)(Li)). The solid obtained was analyzed using ICP, and the boron content was 49 relative to 100 for lithium.

[0101] <Examples 1 to 4> When the electrolyte, O-(BF3Li)2 or S-(BF3Li)2, was added to a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and vinylene carbonate (VC) (volume ratio 30:68:2), it dissolved well, and the respective electrolyte solutions used in Examples 1 to 4 shown in Table 1 were prepared. Using each of the electrolyte solutions prepared above, the batteries of Examples 1 to 4 were fabricated according to the battery fabrication procedure described above, and then the resistance change rate and capacity retention rate were determined. The results are shown in Table 1.

[0102] [Table 1] As shown in Table 1, the batteries of Examples 1 to 4 exhibited the effect of maintaining a high cycle capacity retention rate and suppressing the rate of resistance change to a low level.

[0103] <Examples 5 to 8, Comparative Example 1> A reference electrolyte 1 was prepared by dissolving LiPF6 as a lithium salt in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 30:70) to a concentration of 1 mol / L. Next, O-(BFLi) was added to this reference electrolyte solution 1 to prepare each electrolyte solution in the amount shown in Table 2. The amount (%) added in Table 2 is the mass % of the added electrolyte relative to the total mass (100 mass %) of reference electrolyte solution 1 and the electrolyte. Using each of the electrolyte solutions prepared above, laminate batteries of Examples 5 to 8 were produced according to the battery production procedure described above, and then the resistance change rate and capacity retention rate were determined. The results are shown in Table 2.

[0104] [Table 2]

[0105] As shown in Table 2, the addition of a lithium compound and a boron trifluoride complex significantly reduces the resistance change rate during high-temperature cycling and also improves the capacity retention rate after cycling.

[0106] <Examples 9 to 17, Comparative Example 2> LiPF6 was added as a lithium salt to a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) (volume ratio 30:67:3) to a concentration of 1 mol / L, and then dissolved to prepare reference electrolyte 2. Next, each electrolyte shown in Table 3 was added to this reference electrolyte solution 2 in the amount shown in Table 3 to prepare each electrolyte solution. The amount (%) added in Table 3 is the mass % of the added electrolyte relative to the total mass (100 mass %) of reference electrolyte solution 1 and the electrolyte.

[0107] After preparing laminate batteries using electrolyte solutions 9 to 17 and Comparative Example 2 shown in Table 3, the resistance change rate and capacity retention rate were determined.

[0108] [Table 3]

[0109] As shown in Table 3, the addition of the lithium-containing complex compound significantly reduced the rate of resistance change during high-temperature cycles, and in particular, Examples 7, 8, 12, and 13 showed a large improvement. In addition, the capacity retention rate after cycling is improved. Among them, Compound A containing O, S, and Si elements can significantly improve the capacity retention rate.

[0110] <Examples 18 to 17> LiPF6 as a lithium salt was added to a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 30:70) to a concentration of 1 mol / L, and then dissolved to prepare reference electrolyte 3. Next, S-(BF3Li)2 was added to the above-mentioned reference electrolyte 3 so that the amount added was 0.3 mass %, and further, the additives shown in Table 4 were added so that the amount added (%) was shown in Table 4, to prepare each of the electrolytes of Examples 18 to 21. Note that no S-(BF3Li)2 was added to the electrolyte of Comparative Example 3. The amount added is in mass % relative to the total mass (100 mass %) of the reference electrolyte 3, S-(BF3Li)2, and additives.

[0111] Using the electrolytes 14 to 17 and the reference electrolyte 3 shown in Table 4, laminate batteries of Examples 14 to 17 and Comparative Example 3 were fabricated according to the above-described battery fabrication procedure, and the resistance change rate and capacity retention rate were then determined. The results are shown in Table 4.

[0112] [Table 4]

[0113] As shown in Table 4, the addition of lithium compound A and boron trifluoride complex significantly improves the capacity retention rate during high-temperature cycling and significantly reduces the rate of resistance change after cycling.

[0114] <Example B Series> <Production Example 1> 50 ml of ion-exchanged water was placed in a 200 ml beaker, and 6.2 g of boric acid was added, and the mixture was heated to 60° C. with stirring. Next, the mixture was kept at 60° C., and 72 g of 10% by mass lithium hydroxide was added with stirring, and the mixture was further stirred for 12 hours while maintaining the temperature at 60° C. The reaction solution was then concentrated to dryness and dried under reduced pressure at 200°C for 12 hours, after which it was pulverized to obtain a white powder of trilithium borate. Then, under an argon atmosphere, the white powder of trilithium borate and 30 ml of diethyl ether were placed in a 100 ml Erlenmeyer flask, and the mixed solution was cooled to 10° C. with stirring. Next, the mixed solution was kept at 20° C. and 45 g of boron trifluoride diethyl ether complex was added over 3 hours with stirring, and then the reaction solution was kept at 50° C. and stirred for 3 hours. The diethyl ether was then removed to obtain a crude B-(OBF3Li)3 complex. The crude product was washed three times with 10 ml of dibutyl ether to remove excess boron trifluoride diethyl ether complex. The resulting solid was then dried under reduced pressure at 110°C for 10 hours to obtain B-(OBF3Li)3, a complex of lithium borate and 3BF3. The solid obtained was analyzed by ICP, and the ratio of lithium atoms to boron atoms was found to be 3:4.

[0115] <Production Example 2> LiBO-(OBFLi)2, a complex of lithium borate and 2BF3, was obtained by carrying out the same procedure as in Production Example 1, except that 29 g of boron trifluoride diethyl ether complex was used instead of 45 g of boron trifluoride diethyl ether complex. The solid obtained was analyzed using ICP, and the ratio of lithium atoms to boron atoms was found to be 1:1.

[0116] <Production Example 3> A white powder of dilithium borate was obtained in the same manner as in Production Example 1, except that 50 g of 10 mass % lithium hydroxide was used instead of 72 g of 10 mass % lithium hydroxide. The procedure of Production Example 1 was repeated except that 29 g of boron trifluoride diethyl ether complex was used instead of 45 g of boron trifluoride diethyl ether complex, to obtain dilithium borate and 2BF3 complex, BO-(OBF3Li)4. The solid obtained was analyzed using ICP, and the ratio of lithium atoms to boron atoms was found to be 2:3.

[0117] <Production Example 4> 100 ml of ion-exchanged water was placed in a 300 ml beaker, and 31 g of boric acid was added. The mixture was then heated to 60° C. with stirring. Next, while the mixture was kept at 60° C. and stirred, 30 g of 10% by mass lithium hydroxide was added, and the mixture was further stirred for 12 hours while maintaining the temperature at 60° C. Next, the reaction solution was concentrated to dryness, dried under reduced pressure in an atmosphere of 200° C. for 12 hours, and then pulverized to obtain a white powder. Then, under an argon atmosphere, the obtained white powder and 50 ml of diethyl ether were placed in a 300 ml Erlenmeyer flask, and the mixed solution was cooled to 10° C. with stirring. Next, the mixed solution was kept at 20° C. and 16 g of boron trifluoride diethyl ether complex was added over 3 hours with stirring, and then the reaction solution was kept at 50° C. and stirred for 3 hours. Then, the diethyl ether was removed to obtain a crude B5O7-(OBF3Li) complex. The resulting crude complex was washed three times with 50 ml of dibutyl ether to remove excess boron trifluoride diethyl etherate, and the resulting solid was dried under reduced pressure at 110°C for 10 hours to obtain the B5O7-(OBF3Li) complex. The solid obtained was analyzed using ICP, and the ratio of lithium atoms to boron atoms was found to be 1:6.

[0118] <Production Example 5> In a 200 ml beaker, 50 ml of ion-exchanged water was placed, and 6.2 g of boric acid was added. The mixture was kept at 25°C, and 22.8 g of trifluoroacetic acid was slowly added while stirring. The mixture was then stirred for 12 hours while maintaining the temperature at 60°C. The reaction solution was then kept at 25° C. and 24 g of 10% by mass lithium hydroxide was added, followed by stirring for 12 hours while maintaining the temperature at 60° C. The reaction solution was then concentrated to dryness, dried under reduced pressure in an atmosphere at 120° C. for 6 hours, and pulverized to obtain a white powder. Then, under an argon atmosphere, the obtained white powder and 50 ml of diethyl ether were placed in a 200 ml Erlenmeyer flask, and the mixed solution was cooled to 10° C. with stirring. Next, the mixed solution was kept at 20° C. and 16 g of boron trifluoride diethyl ether complex was added over 3 hours with stirring, and then the reaction solution was kept at 50° C. and stirred for 3 hours.

[0119] Next, the diethyl ether was removed to obtain a crude B(OC(=O)CF3)2(OBF3Li) complex. The obtained crude was washed three times with 50 ml of dibutyl ether to remove excess boron trifluoride diethyl ether complex. The obtained solid was then dried under reduced pressure at 110°C for 10 hours to obtain the B(OC(=O)CF3)2(OBF3Li) complex. The solid obtained was analyzed using ICP, and the ratio of lithium atoms to boron atoms was found to be 1:2.

[0120] <Production Examples 6 to 8> The same procedures as in Production Example 1 were carried out except that 9 g of oxalic acid (Production Example 6), 10.4 g of malonic acid (Production Example 7), and 15 g of thiodiacetic acid (Production Example 8) were used instead of 22.8 g of trifluoroacetic acid, to obtain a B(OOC-COO)(OBFLi) complex (Production Example 6), a B(OOCCHCOO)(OBFLi) complex (Production Example 7), and a B(OOCCHSCHCOO)(OBFLi) complex (Production Example 8). The solid obtained was analyzed using ICP, and the ratio of lithium atoms to boron atoms was found to be 1:2.

[0121] <Examples 1 to 6> Each electrolyte shown in Table 5 was added to a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and vinylene carbonate (VC) (volume ratio 30:30:38:2) in the amount shown in Table 5 to prepare each of the electrolytes used in Examples 1 to 4 shown in Table 5. The amount of electrolyte added in Table 5 is in moles / liter based on lithium. Using each of the electrolyte solutions prepared above, the batteries of Examples 1 to 6 were fabricated according to the battery fabrication procedure described above, and then the resistance change rate and capacity retention rate were determined. The results are shown in Table 5.

[0122] [Table 5] As shown in Table 5, the batteries of Examples 1 to 6 exhibited the effect of maintaining a high cycle capacity retention rate and suppressing the rate of resistance change to a low level.

[0123] <Examples 7 to 19> Reference electrolyte 1 was prepared by dissolving LiPF6 as a lithium salt in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 30:70) to a concentration of 1 mol / L in 99 g of solution, and then adding 1 g of vinylene carbonate. Next, the lithium-containing boron complex compound shown in Table 6 was added to this reference electrolyte solution 1 in the amount shown in Table 6 to prepare each of the electrolyte solutions used in Examples 7 to 20 and Comparative Example 1. The amount added (%) in Table 6 is the mass % relative to the total mass (100 mass %) of the reference electrolyte 1 and the compound in question.

[0124] Using each of the electrolyte solutions prepared above, batteries of Examples 7 to 20 and Comparative Example 1 were fabricated according to the above battery fabrication procedure, and then the resistance change rate and capacity retention rate were determined according to the above procedures for determining the resistance change rate and capacity retention rate, respectively. The results are shown in Table 6.

[0125] [Table 6]

[0126] As shown in Table 6, the addition of the lithium-containing boron complex compound significantly reduced the resistance change rate during high-temperature cycling and also improved the capacity retention rate after cycling.

[0127] <Examples 21 to 24> Reference electrolyte 2 was prepared by adding and dissolving LiPF6 as a lithium salt in a mixed solvent (volume ratio 30:70) of ethylene carbonate (EC) and diethyl carbonate (DEC) to a concentration of 1 mol / L. Next, B-(OBF3Li)3 was added to the above-mentioned reference electrolyte 2 so that the amount added was 0.5 mass %, and further, the additives shown in Table 7 were added so that the amount added was the % in Table 7, to prepare each of the electrolytes of Examples 20 to 23. Note that no B-(OBF3Li)3 was added to the electrolyte of Comparative Example 2. The amount added is in mass % relative to the total mass (100 mass %) of the reference electrolyte 2, B-(OBF3Li)3, and additives.

[0128] Using the electrolytes 21 to 24 and the reference electrolyte 2 shown in Table 7, the batteries of Examples 21 to 24 and Comparative Example 2 were fabricated according to the above-mentioned battery fabrication procedure, and then the resistance change rate and capacity retention rate were determined. The results are shown in Table 7.

[0129] [Table 7]

[0130] As shown in Table 7, the addition of the lithium-containing boron complex compound improved the capacity retention rate during high-temperature cycling and significantly reduced the rate of resistance change after cycling. [Industrial Applicability]

[0131] The nonaqueous electrolyte solution type or all-solid electrolyte type lithium secondary battery using the electrolyte for an electricity storage device of the present invention is widely used in electricity storage devices such as power sources for various consumer appliances such as mobile phones and laptop computers, power sources for industrial equipment, storage batteries, and automobile power sources.

Claims

1. 1. An electricity storage device comprising a positive electrode, a negative electrode, and an electrolyte disposed between the electrodes, wherein the electrolyte contains a lithium-containing complex compound represented by the following formula (1), (2), (3), (4), or (5); the negative electrode contains at least one negative electrode active material selected from the group consisting of carbon materials, tin, tin alloys, and tin oxides; and the carbon material is selected from pyrolytic carbons, cokes, graphites, baked organic polymer compounds, carbon fiber, activated carbon, or a mixture thereof, or a carbon material coated with gold, platinum, silver, copper, Sn, or Si, or the gold, platinum, silver, copper, Sn, or Si coated with amorphous carbon. ((Li) ｍ (A) ｎ (UF ｘ ) ｙ (1) (Li) ｍ (Yes) ｎ (O) ｑ (UF) ｘ ) ｙ (2) (In the formula, A is O, S, P, or N. U is a boron atom or a phosphorus atom. m and n each independently represent 1 to 6. q represents 1 to 12. x represents 3 or 5. y represents 1 to 6.) (Li) ｍ (O) ｎ (B) ｐ (OTF ｑ ) ｘ (3) (In the formula, W is a boron atom or a phosphorus atom; m, p, and x each independently represent 1 to 15; n represents 0 to 15; and q represents 3 or 5.) (Li) ｍ (B) ｐ (O) ｎ (OR) ｙ (OWF ｑ ) ｘ (4) (In the formula, W is a boron atom or a phosphorus atom; n is 0 to 15; p, m, x, and y each independently are 1 to 12; q is 3 or 5; R is a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a carbonyl group, or a sulfonyl group, and these groups may have a fluorine atom, an oxygen atom, and other substituents.) (Li) ｍ (O) ｎ (B) ｐ (OOC-(A) ｚ -COO) ｙ (OWF ｑ ) ｘ (5) (In the formula, W is a boron atom or a phosphorus atom; A is an alkylene group, alkenylene group, or alkynylene group having 1 to 6 carbon atoms, a phenylene group, or an alkylene group having an oxygen atom or a sulfur atom in the main chain; m, p, x, and y each independently are 1 to 20; n is 0 to 15; z is 0 or 1; and q is 3 or 5.)

2. 2. The electricity storage device according to claim 1, which is a lithium ion secondary battery.

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