Non-aqueous electrolytic solution and non-aqueous electrolytic solution battery using the same

Abstract

To provide a nonaqueous electrolyte secondary battery having well-balanced overall performance in terms of durability, capacity, resistance, and output characteristics.SOLUTION: The nonaqueous electrolyte battery includes a positive electrode and a negative electrode capable of storing and releasing metal ions, and a nonaqueous electrolytic solution, wherein the nonaqueous electrolytic solution contains an electrolyte, a nonaqueous solvent, and at least one compound selected from the group consisting of lithium fluorosulfonate, lithium bis (fluorosulfonyl) imide, and lithium difluorophosphate, and the negative electrode contains a negative electrode active material containing Si or a Si metal oxide and graphite particles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte battery using the same. [Background technology]

[0002] With the rapid advancement of portable electronic devices such as mobile phones and laptop personal computers, there is a growing demand for higher capacity batteries to be used as their main power sources and backup power sources. As a result, non-aqueous electrolyte batteries such as lithium-ion secondary batteries, which have higher energy density than nickel-cadmium batteries and nickel-metal hydride batteries, are attracting attention. Representative examples of electrolytes for lithium ion secondary batteries include non-aqueous electrolytes in which an electrolyte such as LiPF6, LiBF4, LiN(CF3SO2)2, or LiCF3(CF2)3SO3 is dissolved in a mixed solvent of a high-dielectric-constant solvent such as ethylene carbonate or propylene carbonate and a low-viscosity solvent such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.

[0003] Furthermore, the negative electrode active material used in lithium-ion secondary batteries is primarily a carbonaceous material capable of absorbing and desorbing lithium ions, with typical examples including natural graphite, artificial graphite, and amorphous carbon. Furthermore, metal or alloy-based negative electrodes using silicon, tin, and other materials are also known for achieving higher capacity. The positive electrode active material is primarily a transition metal composite oxide capable of absorbing and desorbing lithium ions, with typical examples of transition metals including cobalt, nickel, manganese, and iron.

[0004] Such lithium ion secondary batteries use highly active positive and negative electrodes, and it is known that the charge / discharge capacity decreases due to side reactions between the electrodes and the electrolyte. Therefore, various studies have been conducted on non-aqueous solvents and electrolytes in order to improve battery characteristics. Patent Documents 1 and 2 attempt to improve the cycle characteristics of a battery by adding an isocyanate compound to a non-aqueous electrolyte solution.

[0005] Patent Document 3 attempts to improve the high-temperature storage characteristics of a battery by using an electrolyte solution containing lithium fluorophosphate salt. Patent Document 4 reports that the use of an electrolyte containing lithium fluorosulfonate improves the high-temperature storage characteristics, input / output characteristics, and impedance characteristics of a battery.

[0006] In Patent Document 5, an attempt is made to improve the cycle characteristics of a battery by using a material containing Si and O as constituent elements and a graphite material as the negative electrode active material, and using a halogenated cyclic carbonate or vinylene carbonate as the electrolyte. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2005-259641 [Patent Document 2] Japanese Patent Publication No. 2006-164759 [Patent Document 3] Japanese Patent Application Publication No. 11-67270 [Patent Document 4] Japanese Patent Application Publication No. 2011-187440 [Patent Document 5] Japanese Patent Application Publication No. 2011-233245 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] However, in recent years, there has been an increasing demand for improved performance of lithium nonaqueous electrolyte secondary batteries, and although there is a demand for batteries to have high levels of all performance, including high-temperature storage characteristics, energy density, output characteristics, lifespan, high-rate charge / discharge characteristics, and low-temperature characteristics, this has not yet been achieved. There is a trade-off between durability, including high-temperature storage characteristics, and performance such as capacity, resistance, and output characteristics, resulting in a poor balance of overall performance.

[0009] The present invention has been made in view of the above-mentioned problems, and has an object to provide a nonaqueous electrolyte secondary battery that has a good balance of overall performance in terms of durability and performance such as capacity, resistance, and output characteristics. [Means for solving the problem]

[0010] As a result of intensive research into achieving the above-mentioned object, the inventors of the present invention have found that the above-mentioned problems can be solved by using a nonaqueous electrolyte battery including a positive electrode and a negative electrode capable of absorbing and desorbing metal ions, and a nonaqueous electrolyte solution, wherein the nonaqueous electrolyte solution contains, together with an electrolyte and a nonaqueous solvent, at least one compound selected from the group consisting of compounds having a fluorosulfonyl structure (-SOF), difluorophosphates, and isocyanate compounds, and the negative electrode has a negative electrode active material containing metal particles capable of alloying with Li and graphite particles, and have completed the present invention, which will be described below.

[0011] The gist of the present invention is as follows. (a) A non-aqueous electrolyte battery comprising a positive electrode and a negative electrode capable of absorbing and releasing metal ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution contains, together with an electrolyte and a non-aqueous solvent, at least one compound selected from the group consisting of compounds having a fluorosulfonyl structure (-SOF), difluorophosphates, and isocyanate compounds, and the negative electrode has a negative electrode active material containing metal particles capable of alloying with Li and graphite particles.

[0012] (b) The nonaqueous electrolyte battery according to (a), wherein the metal particles capable of being alloyed with Li are at least one metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W, or a metal compound thereof. (c) The nonaqueous electrolyte battery according to (a) or (b), wherein the metal particles capable of being alloyed with Li are Si or Si metal oxide.

[0013] (d) The nonaqueous electrolyte battery according to any one of (a) to (c), wherein the negative electrode active material containing metal particles capable of being alloyed with Li and graphite particles is a composite of a metal and / or a metal compound and graphite particles. (e) The nonaqueous electrolyte battery according to any one of (a) to (d), wherein the content of the metal particles that can be alloyed with Li is 0.1 to 25 mass % relative to the total of the metal particles that can be alloyed with Li and the graphite particles. (f) The nonaqueous electrolyte battery according to any one of (a) to (e), wherein the content of the metal particles that can be alloyed with Li is 0.1 to 20 mass % relative to the total of the metal particles that can be alloyed with Li and the graphite particles. (g) The nonaqueous electrolyte battery according to any one of (a) to (f), wherein the content of the metal particles that can be alloyed with Li is 0.1 to 15 mass % relative to the total of the metal particles that can be alloyed with Li and the graphite particles. (h) The nonaqueous electrolyte battery according to any one of (a) to (g), wherein the content of the metal particles that can be alloyed with Li is 0.1 to 10 mass % relative to the total of the metal particles that can be alloyed with Li and the graphite particles.

[0014] (i) The compound having a fluorosulfonyl structure (-SOF) is selected from the group consisting of lithium fluorosulfonate, lithium bis(fluorosulfonyl)imide, and compounds represented by the following general formula (A): [ka] In formula (A), R1's are each independently an alkyl group, alkenyl group, or alkynyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aromatic hydrocarbon group having 6 to 20 carbon atoms which may be substituted with a halogen atom, and n represents an integer of 0 to 1. The nonaqueous electrolyte battery according to any one of (a) to (h), wherein the compound is a compound represented by the formula: (j) The nonaqueous electrolyte battery according to any one of (a) to (i), wherein the difluorophosphate salt is lithium difluorophosphate. (k) The isocyanate compound is a hydrocarbon diisocyanate compound represented by the following general formula (C): [ka] In formula (C), each R2 is independently an alkyl group, alkenyl group, or alkynyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aromatic hydrocarbon group having 6 to 20 carbon atoms which may be substituted with a halogen atom, or an isocyanato group or a halogen atom, and n represents an integer of 0 to 1. The nonaqueous electrolyte battery according to any one of (a) to (j), wherein the compound is represented by the formula: (l) The nonaqueous electrolyte battery according to any one of (a) to (k), wherein the at least one compound selected from the group consisting of a compound having a fluorosulfonyl structure (-SO2F), a difluorophosphate, and an isocyanate compound is present in an amount of 0.01% by mass or more and 10.0% by mass or less relative to the total amount of the nonaqueous electrolyte.

[0015] (m) The nonaqueous electrolyte battery according to any one of (a) to (l), wherein the nonaqueous electrolyte contains at least one compound selected from the group consisting of a cyclic carbonate having a carbon-carbon unsaturated bond, a cyclic carbonate having a fluorine atom, an acid anhydride compound, a cyclic sulfonic acid ester compound, and a compound having a cyano group. (n) The nonaqueous electrolyte battery according to (m), wherein the content of the at least one compound selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond, cyclic carbonates having a fluorine atom, acid anhydride compounds, cyclic sulfonate ester compounds, and compounds having a cyano group is 0.001% by mass or more and 10% by mass or less, based on the total amount of the nonaqueous electrolyte. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a lithium nonaqueous electrolyte secondary battery that has a good balance of overall performance in terms of durability and performance such as capacity, resistance, output characteristics, etc. Specifically, it is possible to provide a battery that suppresses capacity reduction and exhibits little battery swelling even after repeated charge-discharge cycles. The action and principle by which a nonaqueous electrolyte secondary battery produced using the nonaqueous electrolyte of the present invention and a nonaqueous electrolyte secondary battery of the present invention become a secondary battery with well-balanced overall performance is not clear, but is thought to be as follows: However, the present invention is not limited to the action and principle described below.

[0017] It has been reported that the compounds described in Patent Documents 1 to 4 act on the positive or negative electrode of a battery to improve the storage characteristics of the battery, but the effects are only observed when graphite or metallic lithium is used for the negative electrode, and no effect has been clarified on negative electrodes using Si, Sn, Pb, or oxides thereof. Patent Document 5 clarifies the effects of using a material containing Si and O as constituent elements and a graphite material as the negative electrode active material and using a halogenated cyclic carbonate or vinylene carbonate as the electrolyte solution, but does not clarify the effects of using an isocyanate compound, a fluorosulfonate, or a fluorophosphate / difluorophosphate compound as the electrolyte solution described in Patent Documents 1 to 4.

[0018] Si-based active materials have attracted attention as next-generation anodes due to their significantly higher theoretical capacity per mass and volume of anode active material compared to currently used carbon anodes. However, Si-based active materials undergo significant volumetric changes (100–300%) upon absorption and desorption of lithium ions, resulting in problems such as the disconnection of electronic conduction paths within the electrode and degradation of the electrode composite and active material due to particle pulverization. Repeated charge / discharge cycles result in particle pulverization, exposing highly active nascent surfaces (dangling bonds). Reaction of these exposed surfaces with the electrolyte alters the active material surface, resulting in a decrease in active material capacity, discrepancies in the depth of charge between the positive and negative electrodes, and poor cycle characteristics. To address this issue, the present invention incorporates an isocyanate compound, a compound with a fluorosulfonyl structure (-SO2F), or a difluorophosphate salt into the electrolyte. For example, in the case of isocyanate compounds, the molecular weight of the decomposition products of the solvent reacts with the isocyanate group, making them insoluble in the electrolyte. This deposits a film on the active material surface, suppressing the reductive decomposition of the electrolyte. Furthermore, because the isocyanate group is polarized, it reacts with the silicon surface, suppressing a decrease in surface activity and alteration of the active material. Compounds with a fluorosulfonyl structure (-SO2F) have a high degree of polarization due to the fluorine atoms bonded to the SO2 group, and the fluorine atoms are highly detachable. This allows lithium fluoride, which is insoluble in the electrolyte, to deposit on the active material surface, suppressing the reductive decomposition of the electrolyte, similar to isocyanate compounds. Furthermore, the reaction of the highly detachable fluorine atoms with the silicon surface also suppresses a decrease in surface activity and alteration of the active material, as described above. The effects of difluorophosphate compounds are similar to those of compounds with a fluorosulfonyl structure (-SO2F).

[0019] To solve the above problems, the present invention provides a nonaqueous electrolyte battery comprising a positive electrode and a negative electrode capable of absorbing and releasing metal ions, and a nonaqueous electrolyte solution, wherein the nonaqueous electrolyte solution contains, together with an electrolyte and a nonaqueous solvent, at least one compound selected from the group consisting of compounds having a fluorosulfonyl structure (-SO2F), difluorophosphates, and isocyanate compounds, and the negative electrode has a negative electrode active material containing metal particles capable of alloying with Li and graphite particles. As a result, the inventors have found that this battery can improve not only high-temperature storage characteristics but also various other characteristics such as cycle gas suppression, cycle characteristics, rate characteristics, and battery swelling, leading to the completion of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0020] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments and can be implemented in any modified form within the scope that does not deviate from the gist of the present invention. Herein, "% by weight", "ppm by weight", and "parts by weight" have the same meaning as "% by mass", "ppm by mass", and "parts by mass", respectively. Furthermore, when simply written as "ppm", it means "ppm by weight".

[0021] 1.Non-aqueous electrolyte 1-1. Non-aqueous electrolyte of the present invention The non-aqueous electrolytic solution of the present invention contains, in addition to an electrolyte and a non-aqueous solvent, at least one compound selected from the group consisting of compounds having a fluorosulfonyl structure (-SO2F), difluorophosphates, and isocyanate compounds.

[0022] When the nonaqueous electrolyte solution contains, in addition to an electrolyte and a nonaqueous solvent, at least one compound selected from the group consisting of a compound having a fluorosulfonyl structure (-SOF), a difluorophosphate, and an isocyanate compound, a nonaqueous electrolyte battery using this nonaqueous electrolyte solution is more likely to exhibit improved cycle characteristics, and also has improved high-temperature storage characteristics, reduces gas generation, and makes it easier to avoid battery swelling.

[0023] Here, "battery swelling" of a nonaqueous electrolyte battery refers to the occurrence of "battery swelling" when the initial battery thickness after initial conditioning is compared with the battery thickness after a high-temperature cycle test (e.g., 100 cycles). If the battery thickness after the high-temperature cycle test is thicker than the initial battery thickness, it can be evaluated that "battery swelling" has occurred. Battery swelling includes swelling due to changes in electrode thickness associated with cycles.

[0024] 1-1-1. Compounds with a fluorosulfonyl structure (-SO2F) Compounds having a fluorosulfonyl structure (-SO2F) are typified by fluorosulfonates, lithium bis(fluorosulfonyl)imide, and compounds represented by general formula (A).

[0025] I. Fluorosulfonates The non-aqueous electrolytic solution of the present invention may contain a fluorosulfonate salt in addition to the electrolyte and the non-aqueous solvent. The fluorosulfonate is represented by the general formula (D). X1(FSO3)n (D) In the formula, X1 represents a counter cation of the fluorosulfonate, and n represents the valence of the counter cation. The counter cation of the fluorosulfonate is not particularly limited, but may be lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, or NR 11 R 12 R 13 R 14 (In the formula, R 11 ~R 14 each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms.

[0026] The above ammonium R 11 ~R 14The organic group having 1 to 12 carbon atoms represented by is not particularly limited, but examples thereof include a hydrogen atom, an alkyl group which may be substituted with a halogen atom, a cycloalkyl group which may be substituted with a halogen atom or an alkyl group, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent. 11 ~R 14 are each independently preferably a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.

[0027] Specific examples of fluorosulfonates include lithium fluorosulfonate, sodium fluorosulfonate, potassium fluorosulfonate, rubidium fluorosulfonate, and cesium fluorosulfonate, with lithium fluorosulfonate being preferred. The fluorosulfonate may be used alone or in any combination and ratio of two or more. The amount of fluorosulfonate is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. It is typically 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and typically 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1% by mass or less, based on 100% by mass of the nonaqueous electrolyte solution. Within the above ranges, the nonaqueous electrolyte battery is likely to exhibit a sufficient improvement in cycle characteristics, and it is also likely to avoid situations such as a decrease in high-temperature storage characteristics, an increase in gas generation, a decrease in discharge capacity retention rate, and battery swelling.

[0028] II. Lithium bis(fluorosulfonylimide)

[0029] The structural formula is represented by the following formula (B). [ka]

[0030] The amount of lithium bis(fluorosulfonyl)imide blended is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1% by mass or less, based on 100% by mass of the nonaqueous electrolyte solution. Within this range, the nonaqueous electrolyte battery is likely to exhibit a sufficient effect of improving the cycle characteristics, and the high-temperature storage characteristics are improved, the amount of gas generation is reduced, and it is easy to avoid situations such as a decrease in the discharge capacity retention rate and battery swelling.

[0031] III. Compounds represented by general formula (A)

[0032] [ka]

[0033] In formula (A), R1's are each independently an alkyl group, alkenyl group, or alkynyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aromatic hydrocarbon group having 6 to 20 carbon atoms which may be substituted with a halogen atom, and n is an integer of 0 to 1. The halogen atom is preferably a fluorine atom.

[0034] In formula (A), when R1 is an alkyl group having 1 to 10 carbon atoms, specific examples of the alkyl group include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl, and cyclic alkyl groups such as cyclopropyl, cyclopentyl, and cyclohexyl. These groups may be substituted with a fluorine atom.

[0035] In formula (A), when R1 is an alkenyl group, R1 is preferably an alkenyl group having 2 to 6 carbon atoms. Specific examples of the alkenyl group include a vinyl group, an allyl group, a methallyl group, a 1-propenyl group, a butenyl group, and a pentenyl group. These groups may be substituted with a fluorine atom, and examples thereof include a fluorine-substituted vinyl group, an allyl group, and a methallyl group.

[0036] In formula (A), when R1 is an alkynyl group, R1 is preferably an alkynyl group having 2 to 6 carbon atoms. Specific examples of the alkynyl group include an ethynyl group, a propargyl group, a 1-propynyl group, a butynyl group, and a hexynyl group. These groups may be substituted with a fluorine atom, and examples thereof include a fluorine-substituted ethynyl group, a propargyl group, and a 1-propynyl group.

[0037] In formula (A), specific examples of the aromatic hydrocarbon group of 6 to 20 carbon atoms which may be substituted with a halogen atom, and which R1 represents, include a phenyl group, a tolyl group, a benzyl group, a phenethyl group, etc. These groups may be substituted with a fluorine atom, a trifluoromethyl group, etc., and examples thereof include a phenyl group, a tolyl group, a benzyl group, a phenethyl group, etc. substituted with a fluorine atom, a trifluoromethyl group, etc.

[0038] Examples of compounds represented by formula (A) include the following compounds: However, the present invention is not limited to the compounds shown below.

[0039] [ka] TIFF2026010062000006.tif200161

[0040] Among these, R1 in formula (A) is preferably a linear alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, or butyl, which may be substituted with fluorine; a phenyl group, tolyl group, or benzyl group, which may be substituted with fluorine, trifluoromethyl group, or the like; or a vinyl group, allyl group, methallyl group, ethynyl group, or propargyl group, which may be substituted with fluorine, from the viewpoint of properties such as cycle characteristics and battery swelling, and more preferably a linear alkyl group, such as methyl, ethyl, or butyl, which may be substituted with fluorine. Furthermore, n is preferably 0 from the viewpoint of improving properties.

[0041] The compound represented by formula (A) may be used alone or in any combination of two or more in any ratio. The amount of the compound represented by formula (A) in the nonaqueous electrolyte solution is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. The amount is typically 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and typically 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1% by mass or less, based on 100% by mass of the nonaqueous electrolyte solution. Within the above ranges, the nonaqueous electrolyte battery is likely to exhibit sufficient improvement in cycle characteristics, and it is also likely to avoid situations such as deterioration in high-temperature storage characteristics, increased gas generation, and a decrease in discharge capacity retention rate, as well as battery swelling.

[0042] Among compounds having a fluorosulfonyl structure (-SOF), preferred are fluorosulfonates and lithium bis(fluorosulfonyl)imide, more preferred are lithium fluorosulfonate and lithium bis(fluorosulfonyl)imide, and particularly preferred is lithium fluorosulfonate.

[0043] 1-1-2.Difluorophosphate Difluorophosphate salts are represented by the general formula (E). X2(F2PO2) m (E) In the formula, X2 represents a counter cation of the fluorophosphate, and m represents the valence of the counter cation. The counter cation of the difluorophosphate is not particularly limited, but may be lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, or NR 11 R 12 R 13 R 14 (In the formula, R 11 ~R 14 each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms.

[0044] The above ammonium R 11 ~R 14 The organic group having 1 to 12 carbon atoms represented by is not particularly limited, but examples thereof include a hydrogen atom, an alkyl group which may be substituted with a halogen atom, a cycloalkyl group which may be substituted with a halogen atom or an alkyl group, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent. 11 ~R 14 are each independently preferably a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.

[0045] Specific examples of difluorophosphates include lithium difluorophosphate, sodium difluorophosphate, and potassium difluorophosphate, with lithium difluorophosphate being preferred. The difluorophosphate may be used alone or in any combination and ratio of two or more. The amount of difluorophosphate is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. It is typically contained at a concentration of 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and typically 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1% by mass or less, based on 100% by mass of the nonaqueous electrolyte solution. Within the above range, the nonaqueous electrolyte battery is likely to exhibit a sufficient improvement in cycle characteristics. Furthermore, within the above range, high-temperature storage characteristics are improved, gas generation is reduced, and problems such as a decrease in discharge capacity retention rate and battery swelling are easily avoided.

[0046] 1-1-4. Isocyanate compounds The isocyanate compound is not particularly limited in type as long as it has an isocyanato group in the molecule.

[0047] I. Hydrocarbon monoisocyanate compounds

[0048] Specific examples of hydrocarbon monoisocyanate compounds include methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tert-butyl isocyanate, pentyl isocyanate, hexyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, and fluorophenyl isocyanate.

[0049] II. Hydrocarbon diisocyanate compounds

[0050] Specific examples of hydrocarbon diisocyanate compounds include monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-diisocyanatopropane, 1,4-diisocyanate, Diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4 ,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methyl isocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methyl isocyanate), isophorone diisocyanate, carbonyl diisocyanate, 1,4-diisocyanatobutane-1,4-dione, 1,5-diisocyanatopentane-1,5-dione, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, etc.

[0051] III. Isocyanate compounds with carbon-carbon unsaturated bonds

[0052] Specific examples of the isocyanate compound having a carbon-carbon unsaturated bond include monoisocyanate compounds having a carbon-carbon unsaturated bond, such as vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, and propynyl isocyanate.

[0053] IV. Isocyanate compounds represented by general formula (C) The isocyanate compound represented by general formula (C) has a -SO2-NCO structure.

[0054] [ka]

[0055] In formula (C), each R2 is independently an alkyl group, alkenyl group, or alkynyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or an aromatic hydrocarbon group having 6 to 20 carbon atoms which may be substituted with a halogen atom, or an isocyanato group or a halogen, and n is an integer of 0 to 1.

[0056] In formula (C), when R2 is an alkyl group having 1 to 10 carbon atoms, specific examples of the alkyl group include, for example, a linear or branched alkyl group such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, or an n-octyl group, or a fluorine-substituted alkyl group, or a cyclic alkyl group such as a cyclopropyl group, a cyclopentyl group, or a cyclohexyl group.

[0057] In formula (C), when R2 is an alkenyl group, R1 is preferably an alkenyl group having 2 to 6 carbon atoms. Specific examples of the alkenyl group include a vinyl group, an allyl group, a methallyl group, a 1-propenyl group, a butenyl group, a pentenyl group, and a fluorine-substituted vinyl group, an allyl group, or a methallyl group.

[0058] In formula (C), when R2 is an alkynyl group, R1 is preferably an alkynyl group having 2 to 6 carbon atoms. Specific examples of the alkynyl group include an ethynyl group, a propargyl group, a 1-propynyl group, a butynyl group, a hexynyl group, and a fluorine-substituted ethynyl group, a propargyl group, or a 1-propynyl group.

[0059] In formula (C), specific examples of R2 being an aromatic hydrocarbon group having 6 to 20 carbon atoms optionally substituted with a halogen atom include a phenyl group, a tolyl group, a benzyl group, a phenethyl group, or a phenyl group, a tolyl group, a benzyl group, a phenethyl group substituted with fluorine, a trifluoromethyl group, or the like.

[0060] Examples of compounds represented by formula (C) include the following compounds: However, the present invention is not limited to the compounds shown below.

[0061] [ka] TIFF2026010062000009.tif226161

[0062] Among these, monoisocyanate compounds having a branched and / or carbon-carbon unsaturated bond, such as isopropyl isocyanate, tert-butyl isocyanate, cyclohexyl isocyanate, vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, and propynyl isocyanate; Monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane hydrocarbon diisocyanate compounds such as hexane, dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methyl isocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methyl isocyanate), isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate; An isocyanate compound represented by general formula (C): is preferable from the viewpoint of improving cycle characteristics and storage characteristics.

[0063] More preferably, isopropyl isocyanate, tert-butyl isocyanate, cyclohexyl isocyanate, allyl isocyanate, hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and the isocyanate compound represented by general formula (C) is preferably a compound represented by the following structure: [ka]

[0064] Particularly preferred are tert-butyl isocyanate, hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, toluenesulfonyl isocyanate, and diisocyanatosulfone, and most preferred are tert-butyl isocyanate, hexamethylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, which have a good balance of battery characteristics.Furthermore, as the hydrocarbon diisocyanate compound, a branched isocyanate compound is preferred.

[0065] The isocyanate compound used in the present invention may be a trimer compound derived from a compound having at least two isocyanato groups in the molecule, or an aliphatic polyisocyanate obtained by adding a polyhydric alcohol to the trimer compound. Examples include biuret, isocyanurate, adduct, and bifunctional modified polyisocyanates represented by the basic structures of the following general formulas (3-1) to (3-4) (in the following general formulas (1-2-1) to (1-2-4), R and R' each independently represent any hydrocarbon group).

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] The compound having at least two isocyanato groups in the molecule used in the present invention also includes so-called blocked isocyanates, which have been blocked with a blocking agent to enhance storage stability. Examples of blocking agents include alcohols, phenols, organic amines, oximes, and lactams, and specific examples include n-butanol, phenol, tributylamine, diethylethanolamine, methyl ethyl ketoxime, and ε-caprolactam.

[0071] In order to promote the reaction based on a compound having at least two isocyanato groups in the molecule and to obtain a higher effect, it is also preferable to use a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo[5.4.0]undecene-7 in combination. Furthermore, the compound having an isocyanato group may be used alone or in any combination of two or more kinds in any ratio.

[0072] The amount of the compound having an isocyanato group relative to the entire nonaqueous electrolyte solution of the present invention is not limited, and may be any amount as long as it does not significantly impair the effects of the present invention. However, the compound is contained in a concentration of usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less, relative to the nonaqueous electrolyte solution of the present invention. When the above range is satisfied, the effects of the output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, and battery swelling can be further improved.

[0073] 1-2. Cyclic carbonates with carbon-carbon unsaturated bonds, cyclic carbonates with fluorine atoms, acid anhydride compounds, cyclic sulfonate ester compounds In terms of improving battery characteristics, the nonaqueous electrolyte solution of the present invention preferably further contains at least one compound selected from the group consisting of a cyclic carbonate having a carbon-carbon unsaturated bond, a cyclic carbonate having a fluorine atom, an acid anhydride compound, a cyclic sulfonate ester compound, and a compound having a cyano group, in addition to at least one compound selected from the group consisting of a compound having a fluorosulfonyl structure (-SOF), a difluorophosphate, and an isocyanate compound.

[0074] 1-2-1. Cyclic carbonates with carbon-carbon unsaturated bonds The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes referred to as "unsaturated cyclic carbonate") is not particularly limited, and any unsaturated carbonate can be used as long as it is a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond. Note that cyclic carbonates having an aromatic ring are also included in the unsaturated cyclic carbonate.

[0075] Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, and catechol carbonates. Vinylene carbonates include: vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, and the like.

[0076] Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include: Examples of the ethylene carbonate include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl-5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, and 4-methyl-5-allyl ethylene carbonate.

[0077] Among them, preferred unsaturated cyclic carbonates are: Examples of the vinylene carbonate include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, and 4-vinyl-5-ethynyl ethylene carbonate.

[0078] Vinylene carbonate, vinylethylene carbonate, and ethynylethylene carbonate are particularly preferred because they form a more stable interface protective film. The molecular weight of the unsaturated cyclic carbonate is not particularly limited and may be any as long as it does not significantly impair the effects of the present invention. The molecular weight is preferably 80 or more and 250 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte solution is easily ensured, and the effects of the present invention are easily exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more and more preferably 150 or less. The method for producing the unsaturated cyclic carbonate is not particularly limited and can be produced by any known method.

[0079] The unsaturated cyclic carbonate may be used alone or in any combination and ratio of two or more. The amount of the unsaturated cyclic carbonate is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. It is usually 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, based on 100% by mass of the nonaqueous electrolyte solution. The amount is usually 10% by mass or less, preferably 5% by mass or less, and more preferably 3% by mass or less. Within this range, the nonaqueous electrolyte battery is likely to exhibit a sufficient improvement in cycle characteristics, and it is also likely to avoid situations such as a decrease in high-temperature storage characteristics, an increase in gas generation, and a decrease in discharge capacity retention rate.

[0080] 1-2-2. Cyclic carbonates containing fluorine atoms Examples of cyclic carbonate compounds having fluorine atoms include fluorinated cyclic carbonates having an alkylene group with 2 to 6 carbon atoms and derivatives thereof, such as fluorinated ethylene carbonate and derivatives thereof. Examples of derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (e.g., an alkyl group with 1 to 4 carbon atoms). Among these, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.

[0081] in particular, Examples of the fluoroethylene carbonate include monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4-(fluoromethyl)-ethylene carbonate, 4-(difluoromethyl)-ethylene carbonate, 4-(trifluoromethyl)-ethylene carbonate, 4-(fluoromethyl)-4-fluoroethylene carbonate, 4-(fluoromethyl)-5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate, and 4,4-difluoro-5,5-dimethylethylene carbonate.

[0082] Among these, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate is more preferred in that it provides high ionic conductivity and favorably forms an interface protective coating. The fluorine atom-containing cyclic carbonate compound may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0083] The cyclic carbonate compound having a fluorine atom may be used alone, or two or more may be used in any combination and ratio. There is no limitation on the amount of halogenated cyclic carbonate to be added to the entire non-aqueous electrolyte solution of the present invention, and it is arbitrary as long as it does not significantly impair the effects of the present invention. In 100% by mass of the non-aqueous electrolyte solution, it is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and also usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. However, monofluoroethylene carbonate may be used as a solvent, and in that case, it is not limited to the above content.

[0084] 1-2-3. Acid anhydride compounds The acid anhydride compound is not limited to carboxylic acid anhydride, sulfuric acid anhydride, nitric acid anhydride, sulfonic acid anhydride, phosphoric acid anhydride, phosphorous acid anhydride, cyclic acid anhydride, chain acid anhydride, or the like, and the structure thereof is not particularly limited as long as it is an acid anhydride compound.

[0085] Specific examples of the acid anhydride compound include: Malonic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, maleic anhydride, citraconic anhydride, 2,3-dimethylmaleic anhydride, glutaconic anhydride, itaconic anhydride, phthalic anhydride, phenylmaleic anhydride, 2,3-diphenylmaleic anhydride, cyclohexane-1,2-dicarboxylic anhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 4,4'-oxydiphthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, phenylsuccinic anhydride, 2-phenyl Examples of the dianhydride include glutaric anhydride, allylsuccinic anhydride, 2-buten-11-ylsuccinic anhydride, (2-methyl-2-propenyl)succinic anhydride, tetrafluorosuccinic anhydride, diacetyl-tartaric anhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, methacrylic anhydride, acrylic anhydride, crotonic anhydride, methanesulfonic anhydride, trifluoromethanesulfonic anhydride, nonafluorobutanesulfonic anhydride, and acetic anhydride.

[0086] Of these, Particularly preferred are succinic anhydride, maleic anhydride, citraconic anhydride, phenylmaleic anhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, allylsuccinic anhydride, acetic anhydride, methacrylic anhydride, acrylic anhydride, and methanesulfonic anhydride.

[0087] The acid anhydride compounds may be used alone or in any combination of two or more in any ratio. The amount of the acid anhydride compound to be blended relative to the entire nonaqueous electrolyte solution of the present invention is not limited and may be any amount as long as it does not significantly impair the effects of the present invention. However, the amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, relative to 100% by mass of the nonaqueous electrolyte solution, and is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

[0088] When the above range is satisfied, the effects of the output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, etc. are further improved. 1-2-4. Cyclic sulfonate ester compounds The type of the cyclic sulfonate compound is not particularly limited. Specific examples of the cyclic sulfonate ester include, for example, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3- Sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2-methyl-1-propene-1,3-sultone, 3-methyl-1-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl-2-propene-1,3-sultone, 1,4-butane sultone, 1-fluoro-1,4-butane sultone, 2-fluoro-1,4-butane sultone, 3-fluoro-1,4-butane sultone sultone, 4-fluoro-1,4-butane sultone, 1-methyl-1,4-butane sultone, 2-methyl-1,4-butane sultone, 3-methyl-1,4-butane sultone, 4-methyl-1,4-butane sultone, 1-butene-1,4-sultone, 2-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro-1-butene-1,4-sultone, 3-fluoro-1-butene-1,4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-fluoro-2-butene-1,4-sultone, 2- Fluoro-2-butene-1,4-sultone, 3-fluoro-2-butene-1,4-sultone, 4-fluoro-2-butene-1,4-sultone, 1-fluoro-3-butene-1,4-sultone, 2-fluoro-3-butene-1,4-sultone, 3-fluoro-3-butene-1,4-sultone, 4-fluoro-3-butene-1,4-sultone, 1-methyl-1-butene-1,4-sultone, 2-methyl-1-butene-1,4-sultone, 3-methyl-1-butene-1,4-sultone, 4-methyl-1-butene-1,4-sultone, 1-methyl-2-butene-1,4-sultone, 2-methyl-2-butene-1,4-sultone, 3-methyl-2-butene-1,4-sultone, 4-methyl-2-butene-1,4-sultone, 1-methyl-3-butene-1,4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1,4-sultone, 4-methyl-3-butene-1,4-sultone, 1,5-pentane sultone, 1-fluoro-1,5-pentane sultone, 2-fluoro-1,5-pentane sultone, 3-fluoro-1,5-pentane sultone, 4-fluoro-1,5-pentane sultone, 5-Fluoro-1,5-pentane sultone, 1-methyl-1,5-pentane sultone, 2-methyl-1,5-pentane sultone, 3-methyl-1,5-pentane sultone, 4-methyl-1,5-pentane sultone, 5-methyl-1,5-pentane sultone, 1-pentene-1,5-sultone, 2-pentene-1,5-sultone, 3-pentene-1,5-sultone, 4-pentene-1,5-sultone, 1-fluoro-1-pentene-1,5-sultone, 2-fluoro-1-pentene-1,5-sultone, 3-fluoro-1-pentene-1,5-sultone , 4-fluoro-1-pentene-1,5-sultone, 5-fluoro-1-pentene-1,5-sultone, 1-fluoro-2-pentene-1,5-sultone, 2-fluoro-2-pentene-1,5-sultone, 3-fluoro-2-pentene-1,5-sultone, 4-fluoro-2-pentene-1,5-sultone, 5-fluoro-2-pentene-1,5-sultone, 1-fluoro-3-pentene-1,5-sultone, 2-fluoro-3-pentene-1,5-sultone, 3-fluoro-3-pentene-1,5-sultone, 4-fluoro-3-pentene-1, 5-sultone, 5-fluoro-3-pentene-1,5-sultone, 1-fluoro-4-pentene-1,5-sultone, 2-fluoro-4-pentene-1,5-sultone, 3-fluoro-4-pentene-1,5-sultone, 4-fluoro-4-pentene-1,5-sultone, 5-fluoro-4-pentene-1,5-sultone, 1-methyl-1-pentene-1,5-sultone, 2-methyl-1-pentene-1,5-sultone, 3-methyl-1-pentene-1,5-sultone, 4-methyl-1-pentene-1,5-sultone, 5-methyl-1-pentene-1,5-sultone, 1-methyl-2-pentene-1,5-sultone, 2-methyl-2-pentene-1,5-sultone, 3-methyl-2-pentene-1,5-sultone, 4-methyl-2-pentene-1,5-sultone, 5-methyl-2-pentene-1,5-sultone, 1-methyl-3-pentene-1,5-sultone, 2-methyl-3-pentene-1,5-sultone, 3-methyl-3-pentene Sultone compounds such as 1,5-sultone, 4-methyl-3-pentene-1,5-sultone, 5-methyl-3-pentene-1,5-sultone, 1-methyl-4-pentene-1,5-sultone, 2-methyl-4-pentene-1,5-sultone, 3-methyl-4-pentene-1,5-sultone, 4-methyl-4-pentene-1,5-sultone, and 5-methyl-4-pentene-1,5-sultone; Sulfate compounds such as methylene sulfate, ethylene sulfate, propylene sulfate, etc.; Disulfonate compounds such as methylenemethane disulfonate and ethylenemethane disulfonate; 1,2,3-Oxathiazolidine-2,2-dioxide, 3-methyl-1,2,3-oxathiazolidine-2,2-dioxide, 3H-1,2,3-oxathiazole-2,2-dioxide, 5H-1,2,3-oxathiazole-2,2-dioxide, 1,2,4-oxathiazolidine-2,2-dioxide, 4-methyl-1,2,4-oxathiazolidine-2,2-dioxide, 3H-1,2,4-oxathiazole-2,2-dioxide, 5H-1,2,4-oxathiazole-2,2-dioxide 1,2,5-oxathiazolidine-2,2-dioxide, 5-methyl-1,2,5-oxathiazolidine-2,2-dioxide, 3H-1,2,5-oxathiazole-2,2-dioxide, 5H-1,2,5-oxathiazole-2,2-dioxide, 1,2,3-oxathiazinane-2,2-dioxide, 3-methyl-1,2,3-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,3-oxathiazine-2,2-dioxide, 1,2,4-oxathiazinane-2,2-dioxide oxide, 4-methyl-1,2,4-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,4-oxathiazine-2,2-dioxide, 3,6-dihydro-1,2,4-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,4-oxathiazine-2,2-dioxide, 1,2,5-oxathiazinane-2,2-dioxide, 5-methyl-1,2,5-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,5-oxathiazine-2,2-dioxide, 3,6 -Nitrogen-containing compounds such as dihydro-1,2,5-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,5-oxathiazine-2,2-dioxide, 1,2,6-oxathiazinane-2,2-dioxide, 6-methyl-1,2,6-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,6-oxathiazine-2,2-dioxide, and 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide; 1,2,3-Oxathiafoslan-2,2-dioxide, 3-methyl-1,2,3-oxathiafoslan-2,2-dioxide, 3-methyl-1,2,3-oxathiafoslan-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiafoslan-2,2,3-trioxide, 1,2,4-oxathiafoslan-2,2-dioxide, 4-methyl-1,2,4-oxathiafoslan-2,2-dioxide, 4-methyl-1,2,4-oxathiafoslan-2,2,4-trioxide, 4-methoxy-1,2,4-oxathiafoslan-2,2,4 -trioxide, 1,2,5-oxathiafoslan-2,2-dioxide, 5-methyl-1,2,5-oxathiafoslan-2,2-dioxide, 5-methyl-1,2,5-oxathiafoslan-2,2,5-trioxide, 5-methoxy-1,2,5-oxathiafoslan-2,2,5-trioxide, 1,2,3-oxathiafosphinane-2,2-dioxide, 3-methyl-1,2,3-oxathiafosphinane-2,2-dioxide, 3-methyl-1,2,3-oxathiafosphinane-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiafosphinane Oxathiphosphinane-2,2,3-trioxide, 1,2,4-oxathiphosphinane-2,2-dioxide, 4-methyl-1,2,4-oxathiphosphinane-2,2-dioxide, 4-methyl-1,2,4-oxathiphosphinane-2,2,3-trioxide, 4-methyl-1,5,2,4-dioxathiphosphinane-2,4-dioxide, 4-methoxy-1,5,2,4-dioxathiphosphinane-2,4-dioxide, 3-methoxy-1,2,4-oxathiphosphinane-2,2,3-trioxide, 1,2,5-oxathiphosphinane 1,2,6-oxathiaphosphinane-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosphinane-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosphinane-2,2,3-trioxide, 5-methoxy-1,2,5-oxathiaphosphinane-2,2,3-trioxide, 1,2,6-oxathiaphosphinane-2,2-dioxide, 6-methyl-1,2,6-oxathiaphosphinane-2,2-dioxide, 6-methyl-1,2,6-oxathiaphosphinane-2,2,3-trioxide, 6-methoxy-1,2,6-oxathiaphosphinane-2,2,Phosphorus-containing compounds such as 3-trioxide; Of these, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1,4-butane sultone, methylenemethane disulfonate, and ethylenemethane disulfonate are preferred from the viewpoint of improving storage properties, and 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, and 1-propene-1,3-sultone are more preferred.

[0089] The cyclic sulfonate ester compound may be used alone, or two or more may be used in any combination and ratio. There is no limitation on the amount of the cyclic sulfonate ester compound in the total non-aqueous electrolyte solution of the present invention, and it is arbitrary as long as it does not significantly impair the effects of the present invention. In 100% by mass of the non-aqueous electrolyte solution, it is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and also usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, particularly preferably 2% by mass or less, and most preferably 1% by mass or less. When the above range is satisfied, the effects of output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, etc. are further improved.

[0090] 1-2-5. Compounds containing a cyano group The compound having a cyano group is not particularly limited in type as long as it has a cyano group in the molecule. Specific examples of compounds having a cyano group include: Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2-hexenenitrile, fluoroacetonitrile, difluoroacetonitrile Compounds having one nitrile group such as fluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, and pentafluoropropionitrile Malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, 2,3,3-trimethylsuccinonitrile succinonitrile, 2,2,3,3-tetramethylsuccinonitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2-dicarbonitrile, bicyclohexyl-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2,3-diisobutyl-2,3-dimethylsuccinonitrile nitrile, 2,2-diisobutyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, maleonitrile, fumaronitrile, 1,4-dicyanopentane, Compounds having two nitrile groups such as 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy)dipropionitrile, 3,3'-(ethylenedithio)dipropionitrile, and 3,9-bis(2-cyanoethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane; Compounds with three cyano groups, such as cyclohexanetricarbonitrile, triscyanoethylamine, triscyanoethoxypropane, tricyanoethylene, pentanetricarbonitrile, propanetricarbonitrile, and heptanetricarbonitrile etc.

[0091] Among these, lauronitrile, crotononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, fumaronitrile, and 3,9-bis(2-cyanoethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane are preferred from the viewpoint of improving storage properties. Furthermore, dinitrile compounds such as succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile, undecanedinitrile, dodecanedinitrile, fumaronitrile, and 3,9-bis(2-cyanoethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane are particularly preferred.

[0092] The nitrile compound may be used alone or in any combination and ratio of two or more. There is no limitation on the amount of the nitrile compound in the total non-aqueous electrolyte solution of the present invention, and it is optional as long as it does not significantly impair the effects of the present invention. In 100% by mass of the non-aqueous electrolyte solution, the amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1% by mass or less. When the above range is satisfied, the effects of output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, etc. are further improved.

[0093] 1-3. Electrolytes <Lithium salt> As the electrolyte, a lithium salt is usually used. There are no particular limitations on the lithium salt, and any lithium salt can be used as long as it is known to be used for this purpose, and specific examples include the following:

[0094] For example, inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, LiWF7, etc.; Lithium tungstates such as LiWOF5; Lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; Lithium sulfonate salts such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li;

[0095] Lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiN(CF3SO2)(C4F9SO2); Lithium methide salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3; lithium oxalatoborate salts such as lithium difluorooxalatoborate and lithium bis(oxalato)borate; Lithium oxalatophosphate salts such as lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, and lithium tris(oxalato)phosphate; Other fluorine-containing organic lithium salts include LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; etc.

[0096] Among these, LiPF6, LiBF4, LiSbF6, LiTaF6, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobisoxalatophosphate, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, and the like are particularly preferred because of their effects of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like.

[0097] These lithium salts may be used alone or in combination of two or more. Preferred examples of the combination of two or more include LiPF6 and LiBF4, LiPF6 and LiN(FSO2)2, and LiPF6 and FSO3Li, which have the effect of improving load characteristics and cycle characteristics. In this case, the concentration of LiBF4 or FSO3Li relative to 100% by mass of the entire non-aqueous electrolyte solution is not limited and may be any amount as long as it does not significantly impair the effects of the present invention. However, the concentration is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less, relative to the non-aqueous electrolyte solution of the present invention.

[0098] Another example is the combined use of an inorganic lithium salt and an organic lithium salt, which has the effect of suppressing deterioration due to high-temperature storage. Preferred organic lithium salts include CF3SO3Li, LiN(FSO2), LiN(FSO2)(CF3SO2), LiN(CF3SO2), LiN(C2F5SO2), lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2), LiC(CF3SO2), LiC(C2F5SO2), lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobisoxalatophosphate, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. In this case, the proportion of the organic lithium salt relative to 100% by mass of the entire non-aqueous electrolyte solution is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and is preferably 30% by mass or less, particularly preferably 20% by mass or less.

[0099] The concentration of these lithium salts in the nonaqueous electrolyte solution is not particularly limited as long as it does not impair the effects of the present invention. However, from the viewpoint of keeping the electrical conductivity of the electrolyte solution in a good range and ensuring good battery performance, the total molar concentration of lithium in the nonaqueous electrolyte solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, even more preferably 0.5 mol / L or more, and is preferably 3 mol / L or less, more preferably 2.5 mol / L or less, even more preferably 2.0 mol / L or less. When the total molar concentration of lithium is within the above range, the electrical conductivity of the electrolyte becomes sufficient, and a decrease in electrical conductivity due to an increase in viscosity and a resulting decrease in battery performance are prevented.

[0100] 1-4.Non-aqueous solvents The non-aqueous solvent in the present invention is not particularly limited, and known organic solvents can be used, examples of which include fluorine-free cyclic carbonates, chain carbonates, cyclic and chain carboxylic acid esters, ether compounds, sulfone compounds, etc.

[0101] <Fluorine-free cyclic carbonate> Examples of cyclic carbonates that do not contain fluorine atoms include cyclic carbonates that contain an alkylene group having 2 to 4 carbon atoms. Specific examples of fluorine-free cyclic carbonates having an alkylene group with 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferred from the viewpoint of improving battery characteristics due to an improved degree of lithium ion dissociation.

[0102] The fluorine atom-free cyclic carbonate may be used alone or in any combination of two or more kinds in any ratio. The amount of the fluorine-free cyclic carbonate is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. However, when one type is used alone, the amount is 5% by volume or more, more preferably 10% by volume or more, based on 100% by volume of the nonaqueous solvent. By setting the amount within this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte can be avoided, and the large-current discharge characteristics, stability to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery can be easily maintained within good ranges. The amount is also 95% by volume or less, more preferably 90% by volume or less, and even more preferably 85% by volume or less. Setting the amount within this range allows the viscosity of the nonaqueous electrolyte to be within an appropriate range, suppresses a decrease in ionic conductivity, and ultimately facilitates maintaining good load characteristics of the nonaqueous electrolyte battery.

[0103] <Chain carbonate> As the chain carbonate, a chain carbonate having 3 to 7 carbon atoms is preferred, and a dialkyl carbonate having 3 to 7 carbon atoms is more preferred. Specific examples of chain carbonates include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, and t-butyl ethyl carbonate.

[0104] Of these, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate are preferred, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferred. Furthermore, chain carbonates containing fluorine atoms (hereinafter, sometimes referred to as "fluorinated chain carbonates") can also be suitably used.

[0105] The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, and preferably 4 or less. When the fluorinated chain carbonate has multiple fluorine atoms, the fluorine atoms may be bonded to the same carbon or different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate and derivatives thereof, fluorinated ethyl methyl carbonate and derivatives thereof, and fluorinated diethyl carbonate and derivatives thereof.

[0106] Examples of fluorinated dimethyl carbonate and derivatives thereof include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis(fluoromethyl)carbonate, bis(difluoro)methyl carbonate, and bis(trifluoromethyl)carbonate. Examples of fluorinated ethyl methyl carbonate and derivatives thereof include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

[0107] Examples of fluorinated diethyl carbonate and its derivatives include ethyl-(2-fluoroethyl)carbonate, ethyl-(2,2-difluoroethyl)carbonate, bis(2-fluoroethyl)carbonate, ethyl-(2,2,2-trifluoroethyl)carbonate, 2,2-difluoroethyl-2'-fluoroethylcarbonate, bis(2,2-difluoroethyl)carbonate, 2,2,2-trifluoroethyl-2'-fluoroethylcarbonate, 2,2,2-trifluoroethyl-2',2'-difluoroethylcarbonate, and bis(2,2,2-trifluoroethyl)carbonate.

[0108] The chain carbonate may be used alone or in any combination of two or more kinds in any ratio. The amount of the chain carbonate blended is preferably 5% by volume or more, more preferably 10% by volume or more, and even more preferably 15% by volume or more, based on 100% by volume of the nonaqueous solvent. By setting the lower limit in this manner, the viscosity of the nonaqueous electrolyte solution is kept within an appropriate range, a decrease in ionic conductivity is suppressed, and the large-current discharge characteristics of the nonaqueous electrolyte battery are more likely to be within a good range. Furthermore, the amount of the chain carbonate blended is preferably 90% by volume or less, more preferably 85% by volume or less, and particularly preferably 80% by volume or less, based on 100% by volume of the nonaqueous solvent. By setting the upper limit in this manner, a decrease in electrical conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte solution is avoided, and the large-current discharge characteristics of the nonaqueous electrolyte battery are more likely to be within a good range.

[0109] <Cyclic carboxylic acid ester> The cyclic carboxylic acid ester preferably has 3 to 12 carbon atoms. Specific examples include gamma-butyrolactone, gamma-valerolactone, gamma-caprolactone, epsilon-caprolactone, etc. Among these, gamma-butyrolactone is particularly preferred from the viewpoint of improving the battery characteristics resulting from the improvement in the degree of dissociation of lithium ions.

[0110] The cyclic carboxylic acid ester may be used alone or as a mixture of two or more kinds in any combination and ratio. The amount of the cyclic carboxylic acid ester is typically preferably 5% by volume or more, more preferably 10% by volume or more, based on 100% by volume of the nonaqueous solvent. This range improves the electrical conductivity of the nonaqueous electrolyte and facilitates the enhancement of the large-current discharge characteristics of the nonaqueous electrolyte battery. Furthermore, the amount of the cyclic carboxylic acid ester is preferably 50% by volume or less, more preferably 40% by volume or less. By setting the upper limit in this way, the viscosity of the nonaqueous electrolyte can be kept within an appropriate range, a decrease in electrical conductivity can be avoided, an increase in negative electrode resistance can be suppressed, and the large-current discharge characteristics of the nonaqueous electrolyte secondary battery can be easily maintained within a favorable range.

[0111] <Chain carboxylic acid ester> The chain carboxylic acid ester preferably has 3 to 7 carbon atoms. Examples thereof 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, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, and isopropyl isobutyrate.

[0112] Among these, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. are preferred from the viewpoint of improving ionic conductivity due to reduced viscosity. The chain carboxylic acid ester may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0113] The amount of the chain carboxylic acid ester blended is usually preferably 10% by volume or more, more preferably 15% by volume or more, based on 100% by volume of the nonaqueous solvent. By setting the lower limit in this manner, the electrical conductivity of the nonaqueous electrolyte is improved, and the large-current discharge characteristics of the nonaqueous electrolyte battery are likely to be improved. Furthermore, the amount of the chain carboxylic acid ester blended is preferably 60% by volume or less, more preferably 50% by volume or less, based on 100% by volume of the nonaqueous solvent. By setting the upper limit in this manner, an increase in negative electrode resistance is suppressed, and the large-current discharge characteristics and cycle characteristics of the nonaqueous electrolyte battery are likely to be within a favorable range.

[0114] <Ether compounds> As the ether-based compound, a chain ether having 3 to 10 carbon atoms, some of whose hydrogen atoms may be substituted with fluorine, and a cyclic ether having 3 to 6 carbon atoms are preferred. Examples of chain ethers with 3 to 10 carbon atoms include: Diethyl ether, di(2-fluoroethyl) ether, di(2,2-difluoroethyl) ether, di(2,2,2-trifluoroethyl) ether, ethyl(2-fluoroethyl) ether, ethyl(2,2,2-trifluoroethyl) ether, ethyl(1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl)(2,2,2-trifluoroethyl) ether, (2-fluoroethyl)(1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl)(1,1,2,2-tetrafluoroethyl) ether 2-fluoroethyl)-n-propyl ether, ethyl (3-fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n-propyl) ether, ethyl (2,2,3,3-tetrafluoro-n-propyl) ether, ethyl (2,2,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propyl ether, (2-fluoroethyl)(3-fluoro-n-propyl) ether, (2-fluoroethyl)(3,3,3-trifluoro-n-propyl) ether, 2-fluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (2-fluoroethyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, 2,2,2-trifluoroethyl-n-propyl ether, (2,2,2-trifluoroethyl)(3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl)(3,3,3-trifluoro-n-propyl) ether, (2,2,2-trifluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (2,2 ,2-trifluoroethyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl)(3-fluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl)(3,3,3-trifluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl)(2,2,3,3,3-Pentafluoro-n-propyl) ether, di-n-propyl ether, (n-propyl)(3-fluoro-n-propyl) ether, (n-propyl)(3,3,3-trifluoro-n-propyl) ether, (n-propyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (n-propyl)(2,2,3,3,3-pentafluoro-n-propyl) ether, di(3-fluoro-n-propyl) ether, (3-fluoro-n-propyl)(3,3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl di(3,3,3-trifluoro-n-propyl)ether, (3,3,3-trifluoro-n-propyl)(2,2,3,3-tetrafluoro-n-propyl)ether, (3,3,3-trifluoro-n-propyl)(2,2,3,3-tetrafluoro-n-propyl)ether, (3,3,3-trifluoro-n-propyl)(2,2,3,3,3-pentafluoro-n-propyl)ether, di(2,2,3,3-tetrafluoro-n-propyl)ether, (2,2,3,3-tetrafluoro-n-propyl)ether Di(2,2,3,3,3-pentafluoro-n-propyl) ether, di(2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy(2-fluoroethoxy)methane, methoxy(2,2,2-trifluoroethoxy)methane, methoxy(1,1,2,2-tetrafluoroethoxy)methane, diethoxymethane, ethoxy(2-fluoroethoxy)methane, ethoxy(2,2,2-trifluoroethoxy)methane, ethoxy(1,1,2 ,2-tetrafluoroethoxy)methane, di(2-fluoroethoxy)methane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)methane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane di(2,2,2-trifluoroethoxy)methane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)methane, di(1,1,2,2-tetrafluoroethoxy)methane, dimethoxyethane, methoxyethoxyethane, methoxy(2-fluoroethoxy)ethane, methoxy(2,2,2-trifluoroethoxy)ethane, methoxy(1,1,2,2-tetrafluoroethoxy)ethane, diethoxyethane, ethoxy(2-fluoroethoxy)ethane, ethoxy(2,2,2-trifluoroethoxy)ethane, ethoxy(1,1,2,2-tetrafluoroethoxy)ethane, di(2-fluoroethoxy)ethane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)ethane, (2-fluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(2,2,2-trifluoroethoxy)ethane, (2,2,2-trifluoroethoxy)(1,1,2,2-tetrafluoroethoxy)ethane, di(1,1,2,2-tetrafluoroethoxy)ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether etc.

[0115] Examples of cyclic ethers having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, and fluorinated compounds thereof. Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether are preferred in that they have a high ability to solvate lithium ions and improve ion dissociation properties, and dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred because they have low viscosity and provide high ionic conductivity.

[0116] The ether-based compounds may be used alone or in any combination of two or more in any ratio. The amount of the ether-based compound is usually, based on 100% by volume of the non-aqueous solvent, preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 15% by volume or more, and preferably 70% by volume or less, more preferably 60% by volume or less, even more preferably 50% by volume or less.

[0117] Within this range, the effect of improving ionic conductivity resulting from the improvement in the degree of lithium ion dissociation of the chain ether and the reduction in viscosity can be easily ensured, and when the negative electrode active material is a carbonaceous material, it is easy to avoid a situation in which the chain ether is co-intercalated with lithium ions, resulting in a decrease in capacity.

[0118] <Sulfone compounds> The sulfone-based compound is preferably a cyclic sulfone having 3 to 6 carbon atoms, or a chain sulfone having 2 to 6 carbon atoms. The number of sulfonyl groups in one molecule is preferably 1 or 2.

[0119] Examples of cyclic sulfones having 3 to 6 carbon atoms include: Monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones; Examples of disulfone compounds include trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones.

[0120] Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferred, and tetramethylene sulfones (sulfolanes) are particularly preferred. The sulfolanes are preferably sulfolane and / or sulfolane derivatives (hereinafter, sulfolane may also be referred to as "sulfolanes"). The sulfolane derivatives are preferably those in which one or more hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.

[0121] Among these, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane sulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoromethylsulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3-(trifluoromethyl)sulfolane, 3-fluoro-3-(trifluoromethyl)sulfolane, 4-fluoro-3-(trifluoromethyl)sulfolane, 5-fluoro-3-(trifluoromethyl)sulfolane, and the like are preferred in terms of high ionic conductivity and excellent input / output characteristics.

[0122] As chain sulfones having 2 to 6 carbon atoms, Dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n-butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl methyl sulfone Examples thereof include fluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di(trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl-n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl-n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, pentafluoroethyl-n-butyl sulfone, and pentafluoroethyl-t-butyl sulfone.

[0123] Among these, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t-butyl sulfone, and the like are preferred in terms of high ionic conductivity and excellent input / output characteristics.

[0124] The sulfone-based compounds may be used alone or in any combination of two or more in any ratio. The amount of the sulfone-based compound is usually, based on 100% by volume of the non-aqueous solvent, preferably 0.3% by volume or more, more preferably 1% by volume or more, and even more preferably 5% by volume or more, and is preferably 40% by volume or less, more preferably 35% by volume or less, and even more preferably 30% by volume or less.

[0125] Within this range, the effect of improving durability such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the nonaqueous electrolyte solution can be set within an appropriate range, thereby preventing a decrease in electrical conductivity and making it easier to avoid a situation in which the charge / discharge capacity retention rate decreases when charging / discharging the nonaqueous electrolyte battery at a high current density.

[0126] <When a fluorine atom-containing cyclic carbonate is used as a non-aqueous solvent> In the present invention, when a cyclic carbonate having a fluorine atom is used as a non-aqueous solvent, one of the non-aqueous solvents exemplified above may be used as a non-aqueous solvent other than the cyclic carbonate having a fluorine atom in combination with the cyclic carbonate having a fluorine atom, or two or more of them may be used in combination with the cyclic carbonate having a fluorine atom.

[0127] For example, one of the preferred combinations of non-aqueous solvents can be the combination mainly composed of fluorine atom-containing cyclic carbonate and chain carbonate.Among them, the total of fluorine atom-containing cyclic carbonate and chain carbonate that occupy in non-aqueous solvent is preferably 60% by volume or more, more preferably 80% by volume or more, even more preferably 90% by volume or more, and the proportion of fluorine atom-containing cyclic carbonate to the total of fluorine atom-containing cyclic carbonate and chain carbonate is 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 15% by volume or more, and usually 60% by volume or less, preferably 50% by volume or less, more preferably 40% by volume or less, even more preferably 35% by volume or less, particularly preferably 30% by volume or less, most preferably 20% by volume or less.

[0128] The use of a combination of these non-aqueous solvents may improve the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity after high-temperature storage and the high-load discharge capacity) of the battery produced using the same. For example, specific examples of preferred combinations of a fluorine atom-containing cyclic carbonate and a chain carbonate include: Examples include monofluoroethylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and diethyl carbonate, monofluoroethylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, and monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0129] Among the combinations of fluorine-containing cyclic carbonates and chain carbonates, those containing symmetric chain alkyl carbonates as the chain carbonate are more preferred, and in particular, those containing monofluoroethylene carbonate, symmetric chain carbonates, and asymmetric chain carbonates, such as monofluoroethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, and monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, are preferred because they have a good balance between cycle characteristics and large current discharge characteristics. Among these, it is preferable that the symmetric chain carbonate is dimethyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.

[0130] The combination of these cyclic carbonates with fluorine atoms and chain carbonates, and further the combination of cyclic carbonates with no fluorine atoms can also be mentioned as a preferred combination.Among them, the total of the cyclic carbonates with fluorine atoms and the cyclic carbonates with no fluorine atoms that occupy in non-aqueous solvent is preferably 10% by volume or more, more preferably 15% by volume or more, even more preferably 20% by volume or more, and the proportion of the cyclic carbonates with fluorine atoms to the total of the cyclic carbonates with fluorine atoms and the cyclic carbonates with no fluorine atoms is 1% by volume or more, preferably 3% by volume or more, more preferably 5% by volume or more, even more preferably 10% by volume or more, particularly preferably 20% by volume or more, and also preferably 95% by volume or less, more preferably 85% by volume or less, even more preferably 75% by volume or less, particularly preferably 60% by volume or less.

[0131] When the fluorine-free cyclic carbonate is contained in this concentration range, a stable protective film can be formed on the negative electrode while maintaining the electrical conductivity of the electrolyte. Specific examples of preferred combinations of a fluorine atom-containing cyclic carbonate, a fluorine atom-free cyclic carbonate, and a chain carbonate include: Monofluoroethylene carbonate, ethylene carbonate, and dimethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate and ethyl ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, and dimethyl carbonate, monofluoroethylene carbonate, propylene carbonate, and diethyl carbonate, monofluoroethylene carbonate, propylene carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate and propylene Carbonate, dimethyl carbonate, and diethyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, and di Methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate,Examples include monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl methyl carbonate, and monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0132] Among the combinations of a fluorine atom-containing cyclic carbonate, a fluorine atom-free cyclic carbonate, and a chain carbonate, those containing an asymmetric chain alkyl carbonate as the chain carbonate are more preferred, and in particular, Monofluoroethylene carbonate, ethylene carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene Ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate Those containing monofluoroethylene carbonate and asymmetric chain carbonates such as those listed above are preferred because they have a good balance between cycle characteristics and large current discharge characteristics. Among these, the asymmetric chain carbonate is preferably ethyl methyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.

[0133] When ethyl methyl carbonate is contained in the non-aqueous solvent, the proportion of ethyl methyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, even more preferably 25% by volume or more, and particularly preferably 30% by volume or more, and is preferably 95% by volume or less, more preferably 90% by volume or less, even more preferably 85% by volume or less, and particularly preferably 80% by volume or less, which may improve the load characteristics of the battery.

[0134] In the combination mainly comprising the fluorine atom-containing cyclic carbonate and the chain carbonate, other solvents such as cyclic carboxylic acid esters, chain carboxylic acid esters, cyclic ethers, chain ethers, sulfur-containing organic solvents, phosphorus-containing organic solvents, and fluorine-containing aromatic solvents may be mixed in addition to the fluorine atom-free cyclic carbonate.

[0135] <When a fluorine atom-containing cyclic carbonate is used as an auxiliary agent> In the present invention, when a cyclic carbonate having a fluorine atom is used as an auxiliary agent, the non-aqueous solvent other than the cyclic carbonate having a fluorine atom may be one of the non-aqueous solvents exemplified above, or two or more of them may be used in any combination and ratio.

[0136] For example, one of the preferred combinations of non-aqueous solvents is a combination mainly composed of a fluorine-free cyclic carbonate and a chain carbonate. In particular, the total amount of the fluorine-free cyclic carbonate and chain carbonate in the non-aqueous solvent is preferably 70% by volume or more, more preferably 80% by volume or more, and even more preferably 90% by volume or more, and the proportion of the fluorine-free cyclic carbonate to the total amount of the cyclic carbonate and chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and even more preferably 15% by volume or more, and is preferably 50% by volume or less, more preferably 35% by volume or less, even more preferably 30% by volume or less, and particularly preferably 25% by volume or less.

[0137] The use of a combination of these non-aqueous solvents may improve the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity after high-temperature storage and the high-load discharge capacity) of the battery produced using the same. For example, specific examples of preferred combinations of fluorine-free cyclic carbonates and chain carbonates include: Examples include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, propylene carbonate and ethyl methyl carbonate, propylene carbonate, ethyl methyl carbonate and diethyl carbonate, propylene carbonate, ethyl methyl carbonate and dimethyl carbonate, and propylene carbonate, ethyl methyl carbonate and dimethyl carbonate.

[0138] Among the combinations of fluorine-free cyclic carbonates and chain carbonates, those containing asymmetric chain alkyl carbonates as the chain carbonate are more preferred, and in particular, combinations such as ethylene carbonate and ethyl methyl carbonate, propylene carbonate and ethyl methyl carbonate, ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, propylene carbonate, ethyl methyl carbonate and dimethyl carbonate, and propylene carbonate, ethyl methyl carbonate and diethyl carbonate are preferred because they have a good balance between cycle characteristics and large-current discharge characteristics.

[0139] Among them, the asymmetric chain carbonate is preferably ethyl methyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms. When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, even more preferably 25% by volume or more, and particularly preferably 30% by volume or more, and is preferably 90% by volume or less, more preferably 80% by volume or less, even more preferably 75% by volume or less, and particularly preferably 70% by volume or less, which may improve the load characteristics of the battery.

[0140] Among these, it is preferable to contain dimethyl carbonate and ethyl methyl carbonate, with the content of dimethyl carbonate being higher than the content of ethyl methyl carbonate, since this can maintain the electrical conductivity of the electrolyte while improving the battery characteristics after high-temperature storage. The volume ratio of dimethyl carbonate to ethyl methyl carbonate in the total nonaqueous solvent (dimethyl carbonate / ethyl methyl carbonate) is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 2.5 or more, from the viewpoint of improving the electrical conductivity of the electrolyte and improving battery characteristics after storage. The volume ratio (dimethyl carbonate / ethyl methyl carbonate) is preferably 40 or less, more preferably 20 or less, even more preferably 10 or less, and particularly preferably 8 or less, from the viewpoint of improving battery characteristics at low temperatures.

[0141] In the above-mentioned combination mainly comprising a fluorine atom-free cyclic carbonate and a chain carbonate, other solvents such as cyclic carboxylic acid esters, chain carboxylic acid esters, cyclic ethers, chain ethers, sulfur-containing organic solvents, phosphorus-containing organic solvents, and aromatic fluorine-containing solvents may be mixed. In this specification, the volume of a non-aqueous solvent is a measurement value at 25°C, but for a substance that is solid at 25°C, such as ethylene carbonate, the measurement value at the melting point is used.

[0142] 1-5. Auxiliaries In addition to the substances described above, the nonaqueous electrolyte battery of the present invention may also contain auxiliary agents, such as aromatic compounds having 12 or fewer carbon atoms, fluorinated unsaturated cyclic carbonates, compounds having a triple bond, and other auxiliary agents, as shown below.

[0143] 1-5-1. Aromatic compounds with 12 or fewer carbon atoms The aromatic compound having 12 or less carbon atoms is not particularly limited in type as long as it has 12 or less carbon atoms in the molecule.

[0144] Specific examples of aromatic compounds having 12 or less carbon atoms include: Aromatic compounds such as biphenyl, alkylbiphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; partially fluorinated products of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; Fluorine-containing anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole Among them, Aromatic compounds such as biphenyl, alkylbiphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferred.

[0145] These may be used alone or in combination of two or more. When two or more are used in combination, it is particularly preferred to use a combination of cyclohexylbenzene with t-butylbenzene or t-amylbenzene, or a combination of at least one selected from oxygen-free aromatic compounds such as biphenyl, alkylbiphenyl, cyclohexylbenzene, t-butylbenzene, and t-amylbenzene with at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran, in terms of a balance of high-temperature storage properties.

[0146] The aromatic compound having 12 or less carbon atoms is not particularly limited and may be any as long as it does not significantly impair the effects of the present invention. The overcharge inhibitor is contained in a concentration of typically 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and typically 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, based on 100% by mass of the nonaqueous electrolyte solution. Within this range, the effects of the overcharge inhibitor are easily exerted and deterioration of battery properties such as high-temperature storage characteristics is easily avoided.

[0147] 1-5-2. Fluorinated unsaturated cyclic carbonates It is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter, sometimes referred to as a "fluorinated unsaturated cyclic carbonate"). The number of fluorine atoms in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, those having 6 or less fluorine atoms are usually preferred, preferably 4 or less, and most preferably 1 or 2 fluorine atoms.

[0148] Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives and fluorinated ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond. Examples of fluorinated vinylene carbonate derivatives include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, and 4-fluoro-5-vinylvinylene carbonate.

[0149] Examples of the fluorinated ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond include: 4-Fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5- Examples include divinyl ethylene carbonate, 4-fluoro-4,5-diallyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-diallyl ethylene carbonate, 4-fluoro-4-phenyl ethylene carbonate, 4-fluoro-5-phenyl ethylene carbonate, 4,4-difluoro-5-phenyl ethylene carbonate, and 4,5-difluoro-4-phenyl ethylene carbonate.

[0150] Among them, preferred fluorinated unsaturated cyclic carbonates include: 4-Fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro Among these, fluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, and 4,5-difluoro-4,5-diallylethylene carbonate are more preferably used because they form stable interface protective coatings.

[0151] The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and may be any as long as it does not significantly impair the effects of the present invention. The molecular weight is preferably 50 or more and 250 or less. Within this range, the solubility of the fluorinated cyclic carbonate in the nonaqueous electrolyte solution is easily ensured, and the effects of the present invention are easily exhibited. The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production. The molecular weight is more preferably 100 or more and more preferably 200 or less.

[0152] The fluorinated unsaturated cyclic carbonate may be used alone or in any combination and ratio of two or more kinds. The amount of the fluorinated unsaturated cyclic carbonate to be added is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. The amount of the fluorinated unsaturated cyclic carbonate is usually, relative to 100% by mass of the nonaqueous electrolyte solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2% by mass or less.

[0153] Within this range, the nonaqueous electrolyte battery is likely to exhibit a sufficient effect of improving cycle characteristics, and it is easy to avoid situations such as a decrease in high-temperature storage characteristics, an increase in gas generation, and a decrease in discharge capacity retention rate.

[0154] 1-5-3. Compounds with triple bonds The compound having a triple bond is not particularly limited in type as long as it has one or more triple bonds in the molecule.

[0155] Specific examples of the compound having a triple bond include the following compounds: hydrocarbon compounds such as 1-pentyne, 2-pentyne, 1-hexyne, 2-hexyne, 3-hexyne, 1-heptyne, 2-heptyne, 3-heptyne, 1-octyne, 2-octyne, 3-octyne, 4-octyne, 1-nonyne, 2-nonyne, 3-nonyne, 4-nonyne, 1-dodecyne, 2-dodecyne, 3-dodecyne, 4-dodecyne, 5-dodecyne, phenylacetylene, 1-phenyl-1-propyne, 1-phenyl-2-propyne, 1-phenyl-1-butyne, 4-phenyl-1-butyne, 4-phenyl-1-butyne, 1-phenyl-1-pentyne, 5-phenyl-1-pentyne, 1-phenyl-1-hexyne, 6-phenyl-1-hexyne, diphenylacetylene, 4-ethynyltoluene, and dicyclohexylacetylene;

[0156] Monocarbonates such as 2-propynyl methyl carbonate, 2-propynyl ethyl carbonate, 2-propynyl propyl carbonate, 2-propynyl butyl carbonate, 2-propynyl phenyl carbonate, 2-propynyl cyclohexyl carbonate, di-2-propynyl carbonate, 1-methyl-2-propynyl methyl carbonate, 1,1-dimethyl-2-propynyl methyl carbonate, 2-butynyl methyl carbonate, 3-butynyl methyl carbonate, 2-pentynyl methyl carbonate, 3-pentynyl methyl carbonate, 4-pentynyl methyl carbonate, etc.; Dicarbonates such as 2-butyne-1,4-diol dimethyl dicarbonate, 2-butyne-1,4-diol diethyl dicarbonate, 2-butyne-1,4-diol dipropyl dicarbonate, 2-butyne-1,4-diol dibutyl dicarbonate, 2-butyne-1,4-diol diphenyl dicarbonate, and 2-butyne-1,4-diol dicyclohexyl dicarbonate;

[0157] 2-Propynyl acetate, 2-Propynyl propionate, 2-Propynyl butyrate, 2-Propynyl benzoate, 2-Propynyl cyclohexylcarboxylate, 1,1-dimethyl-2-propynyl acetate, 1,1-dimethyl-2-propynyl propionate, 1,1-dimethyl-2-propynyl butyrate, 1,1-dimethyl-2-propynyl benzoate, 1,1-dimethyl-2-propynyl cyclohexylcarboxylate, 2-Butynyl acetate, 3-Butynyl acetate, 2-Pentynyl acetate, 3-Pentynyl acetate, 4-Pentynyl acetate, Methyl acrylate, ethyl acrylate, propyl acrylate, vinyl acrylate, 2-propenyl acrylate, 2-butenyl acrylate, 3-butenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propenyl methacrylate, 2-butenyl methacrylate, 3-butenyl methacrylate, methyl 2-propynoate, ethyl 2-propynoate, propyl 2-propynoate, vinyl 2-propynoate, 2-propenyl 2-propynoate, 2-butenyl 2-propynoate , 3-butenyl 2-propynoate, methyl 2-butynoate, ethyl 2-butynoate, propyl 2-butynoate, vinyl 2-butynoate, 2-propenyl 2-butynoate, 2-butenyl 2-butynoate, 3-butenyl 2-butynoate, methyl 3-butynoate, ethyl 3-butynoate, propyl 3-butynoate, vinyl 3-butynoate, 2-propenyl 3-butynoate, 2-butenyl 3-butynoate, 3-butenyl 3-butynoate, methyl 2-pentynoate, ethyl 2-pentynoate, propyl 2-pentynoate, vinyl 2-pentynoate monocarboxylic acid esters such as 2-propenyl pentanoate, 2-butenyl 2-pentanoate, 3-butenyl 2-pentanoate, methyl 3-pentanoate, ethyl 3-pentanoate, propyl 3-pentanoate, vinyl 3-pentanoate, 2-propenyl 3-pentanoate, 2-butenyl 3-pentanoate, 3-butenyl 3-pentanoate, methyl 4-pentanoate, ethyl 4-pentanoate, propyl 4-pentanoate, vinyl 4-pentanoate, 2-propenyl 4-pentanoate, 2-butenyl 4-pentanoate, and 3-butenyl 4-pentanoate; Dicarboxylic acid esters such as 2-butyne-1,4-diol diacetate, 2-butyne-1,4-diol dipropionate, 2-butyne-1,4-diol dibutyrate, 2-butyne-1,4-diol dibenzoate, and 2-butyne-1,4-diol dicyclohexanecarboxylate;

[0158] Oxalic acid diesters such as methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, propyl 2-propynyl oxalate, vinyl 2-propynyl oxalate, allyl 2-propynyl oxalate, di-2-propynyl oxalate, methyl 2-butynyl oxalate, ethyl 2-butynyl oxalate, propyl 2-propynyl oxalate, vinyl 2-butynyl oxalate, allyl 2-butynyl oxalate, di-2-butynyl oxalate, methyl 3-butynyl oxalate, ethyl 3-butynyl oxalate, propyl 3-butynyl oxalate, vinyl 3-butynyl oxalate, allyl 3-butynyl oxalate, and di-3-butynyl oxalate;

[0159] Phosphine oxides such as methyl(2-propynyl)(vinyl)phosphine oxide, divinyl(2-propynyl)phosphine oxide, di(2-propynyl)(vinyl)phosphine oxide, di(2-propenyl)2(-propynyl)phosphine oxide, di(2-propynyl)(2-propenyl)phosphine oxide, di(3-butenyl)(2-propynyl)phosphine oxide, and di(2-propynyl)(3-butenyl)phosphine oxide;

[0160] 2-propynyl methyl(2-propenyl)phosphinate, 2-propynyl 2-butenyl(methyl)phosphinate, 2-propynyl di(2-propenyl)phosphinate, 2-propynyl di(3-butenyl)phosphinate, 1,1-dimethyl-2-propynyl methyl(2-propenyl)phosphinate, 1,1-dimethyl-2-propynyl 2-butenyl(methyl)phosphinate, 1,1-dimethyl-2-propynyl di(2-propenyl)phosphinate, and phosphinic acid esters such as 1,1-dimethyl-2-propynyl di(3-butenyl)phosphinate, 2-propenyl methyl(2-propynyl)phosphinate, 3-butenyl methyl(2-propynyl)phosphinate, 2-propenyl di(2-propynyl)phosphinate, 3-butenyl di(2-propynyl)phosphinate, 2-propenyl 2-propynyl(2-propenyl)phosphinate, and 3-butenyl 2-propynyl(2-propenyl)phosphinate;

[0161] Methyl 2-propenylphosphonate 2-propynyl, methyl 2-butenylphosphonate (2-propynyl), 2-propenylphosphonic acid (2-propynyl) (2-propenyl), 3-butenylphosphonic acid (3-butenyl) (2-propynyl), 2-propenylphosphonic acid (1,1-dimethyl-2-propynyl) (methyl), 2-butenylphosphonic acid (1,1-dimethyl-2-propynyl) (methyl), 2-propenylphosphonic acid (1,1-dimethyl-2-propynyl) (2-propenyl), and 3-butenylphosphonic acid (3-butenyl) (1,1-dimethyl-2-propynyl), methylphosphonic acid ( phosphonic acid esters such as 2-propynyl) methylphosphonate (3-butenyl) (2-propynyl), methylphosphonate (1,1-dimethyl-2-propynyl) (2-propenyl), methylphosphonate (3-butenyl) (1,1-dimethyl-2-propynyl), ethylphosphonate (2-propynyl) (2-propenyl), ethylphosphonate (3-butenyl) (2-propynyl), ethylphosphonate (1,1-dimethyl-2-propynyl) (2-propenyl), and ethylphosphonate (3-butenyl) (1,1-dimethyl-2-propynyl);

[0162] phosphate esters such as (methyl)(2-propenyl)(2-propynyl)phosphate, (ethyl)(2-propenyl)(2-propynyl)phosphate, (2-butenyl)(methyl)(2-propynyl)phosphate, (2-butenyl)(ethyl)(2-propynyl)phosphate, (1,1-dimethyl-2-propynyl)(methyl)(2-propenyl)phosphate, (1,1-dimethyl-2-propynyl)(ethyl)(2-propenyl)phosphate, (2-butenyl)(1,1-dimethyl-2-propynyl)(methyl)phosphate, and (2-butenyl)(ethyl)(1,1-dimethyl-2-propynyl)phosphate; Among these, compounds having an alkynyloxy group are preferred because they form a more stable negative electrode coating in the electrolyte solution.

[0163] moreover, 2-Propynyl methyl carbonate, di-2-propynyl carbonate, 2-butyne-1,4-diol dimethyl dicarbonate, 2-propynyl acetate, 2-butyne-1,4-diol diacetate, 2-propynyl methyl oxalate, di-2-propynyl oxalate The compounds listed above are particularly preferred from the viewpoint of improving storage characteristics.

[0164] The compound having a triple bond may be used alone or in any combination and ratio of two or more. There is no limitation on the amount of the compound having a triple bond relative to the total amount of the non-aqueous electrolyte solution of the present invention, and it is optional as long as it does not significantly impair the effects of the present invention. However, it is usually contained in a concentration of 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, relative to the non-aqueous electrolyte solution of the present invention. When the above range is satisfied, the effects of output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, etc. are further improved.

[0165] 1-5-4. Other auxiliary agents As the other auxiliary agent, known auxiliary agents other than the above-mentioned auxiliary agents can be used. Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, and methoxyethyl-methyl carbonate; Spiro compounds such as 2,4,8,10-tetraoxaspiro[5.5]undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane; Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenyl sulfone, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide, methyl vinylsulfonate, ethyl vinylsulfonate, allyl vinylsulfonate, propargyl vinylsulfonate, methyl allylsulfonate, ethyl allylsulfonate, allyl allylsulfonate, propargyl allylsulfonate, 1,2-bis(vinylsulfonyloxy)ethane sulfur-containing compounds such as;

[0166] Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide; Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide Phosphorus-containing compounds such as;

[0167] Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane, etc.; Fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, and benzotrifluoride; These may be used alone or in combination of two or more. By adding these auxiliary agents, it is possible to improve the capacity retention characteristics and cycle characteristics after high-temperature storage.

[0168] The amount of the other auxiliary agent is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. The amount of the other auxiliary agent is usually 0.01% by mass or more and 10% by mass or less, based on 100% by mass of the non-aqueous electrolyte solution. Within this range, the effects of the other auxiliary agent are easily exerted, and it is easy to avoid a situation in which battery characteristics such as high-load discharge characteristics are deteriorated. The amount of other auxiliary agents is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass, and particularly preferably 1.0% by mass, and is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass, and particularly preferably 1% by mass or less.

[0169] The non-aqueous electrolyte solution described above also includes the one present inside the non-aqueous electrolyte battery described in the present invention. Specifically, this includes a case where the components of the nonaqueous electrolyte solution, such as lithium salt, solvent, and auxiliary agent, are separately synthesized and substantially isolated, and a nonaqueous electrolyte solution is prepared from the resultant solution, and then injected into a battery separately assembled by the method described below, to form a nonaqueous electrolyte solution in a nonaqueous electrolyte battery; a case where the components of the nonaqueous electrolyte solution of the present invention are individually placed in a battery and mixed in the battery to obtain the same composition as the nonaqueous electrolyte solution of the present invention; and a case where compounds constituting the nonaqueous electrolyte solution of the present invention are generated in the nonaqueous electrolyte battery to obtain the same composition as the nonaqueous electrolyte solution of the present invention.

[0170] 2. Battery configuration The nonaqueous electrolyte battery of the present invention is suitable for use as an electrolyte for secondary batteries, such as lithium secondary batteries, among other nonaqueous electrolyte batteries. Hereinafter, a nonaqueous electrolyte battery using the nonaqueous electrolyte of the present invention will be described. The nonaqueous electrolyte battery of the present invention can have a known structure and typically comprises a negative electrode and a positive electrode capable of absorbing and desorbing ions (for example, lithium ions), and the nonaqueous electrolyte of the present invention.

[0171] 2-1. Negative electrode The negative electrode active material used in the negative electrode will be described below. There are no particular limitations on the negative electrode active material as long as it is capable of electrochemically absorbing and releasing lithium ions. Specific examples include carbonaceous materials, alloy materials, and lithium-containing metal composite oxide materials. These may be used alone or in any combination of two or more.

[0172] <Negative electrode active material> Examples of the negative electrode active material include carbonaceous materials, alloy materials, and lithium-containing metal composite oxide materials. Examples of carbonaceous materials include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite.

[0173] (1) Examples of natural graphite include scaly graphite, flake graphite, soil graphite, and / or graphite particles obtained by treating these graphites as raw materials with processes such as spheroidization and densification. Among these, spherical or ellipsoidal graphite that has been subjected to a spheroidization process is particularly preferred from the viewpoints of particle packing properties and charge / discharge rate characteristics. The apparatus used for the spheronization treatment may be, for example, an apparatus that repeatedly applies mechanical actions to particles, such as compression, friction, shear force, etc., mainly impact force, including particle interactions. Specifically, a preferred device has a rotor with many blades installed inside a casing, and the rotor rotates at high speed to apply mechanical actions such as impact compression, friction, and shear force to the carbon material introduced inside, thereby carrying out spheroidization. Also, a device having a mechanism for repeatedly applying mechanical actions by circulating the carbon material is preferred.

[0174] For example, when spheronization is performed using the above-mentioned apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and even more preferably 50 to 100 m / sec. Although the treatment can be performed by simply passing the carbonaceous material through the apparatus, it is preferable to circulate or retain the material in the apparatus for 30 seconds or more, and more preferably to circulate or retain the material in the apparatus for 1 minute or more.

[0175] (2) Examples of artificial graphite include those produced by graphitizing organic compounds such as coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene silicide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin at temperatures typically above 2500°C and typically below 3200°C, followed by pulverization and / or classification as necessary. Silicon-containing compounds, boron-containing compounds, and the like can also be used as graphitization catalysts. Other examples include artificial graphite obtained by graphitizing mesocarbon microbeads separated during the heat treatment of pitch. Further examples include artificial graphite in the form of granulated particles composed of primary particles. Examples of such graphite particles include mesocarbon microbeads and graphite particles in which a plurality of flat particles are aggregated or bonded together so that their orientation planes are non-parallel, and which are obtained by mixing a graphitizable carbonaceous material powder such as coke with a graphitizable binder such as tar or pitch and a graphitization catalyst, graphitizing the mixture, and pulverizing the mixture as necessary.

[0176] (3) Examples of amorphous carbon include amorphous carbon particles obtained by using graphitizable carbon precursors such as tar and pitch as raw materials and heat-treating them at least once in a temperature range in which graphitization does not occur (400 to 2200°C), and amorphous carbon particles obtained by using non-graphitizable carbon precursors such as resin as raw materials and heat-treating them. (4) Examples of carbon-coated graphite include carbon-graphite composites in which natural graphite and / or artificial graphite are mixed with a carbon precursor, such as tar, pitch, or resin, and the mixture is heat-treated at least once in the range of 400 to 2300°C to obtain a core graphite, and the core graphite is coated with amorphous carbon. The composite may be in the form of a coating on the entire or partial surface, or a composite of multiple primary particles using carbon derived from the carbon precursor as a binder. Carbon-graphite composites can also be obtained by reacting natural graphite and / or artificial graphite with a hydrocarbon gas, such as benzene, toluene, methane, propane, or aromatic volatiles, at high temperature to deposit carbon on the graphite surface (CVD).

[0177] (5) Examples of graphite-coated graphite include graphite-coated graphite in which natural graphite and / or artificial graphite is mixed with a carbon precursor of an easily graphitizable organic compound such as tar, pitch, or resin, and the mixture is heat-treated at least once in the range of about 2400 to 3200°C to obtain natural graphite and / or artificial graphite as core graphite, and the graphitized material coats the entire or part of the surface of the core graphite. (6) Examples of resin-coated graphite include resin-coated graphite in which natural graphite and / or artificial graphite is mixed with resin or the like and dried at a temperature of less than 400°C to obtain natural graphite and / or artificial graphite as core graphite, and the core graphite is coated with resin or the like.

[0178] The carbonaceous materials (1) to (6) may be used singly or in any combination of two or more in any ratio. Examples of organic compounds such as tar, pitch, and resins used in the above (2) to (5) include coal-based heavy oil, direct current heavy oil, cracked petroleum heavy oil, aromatic hydrocarbons, N-ring compounds, S-ring compounds, polyphenylene, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins, which can be carbonized. Furthermore, the raw material organic compounds may be dissolved in a low-molecular-weight organic solvent to adjust the viscosity during mixing.

[0179] Furthermore, as the natural graphite and / or artificial graphite that is the raw material for the nuclear graphite, natural graphite that has been subjected to a spheroidizing treatment is preferred. The alloy-based material used as the negative electrode active material is not particularly limited, and may be any of lithium itself, elemental metals and alloys that form lithium alloys, or compounds such as oxides, carbides, nitrides, silicides, sulfides, or phosphides, as long as it is capable of absorbing and releasing lithium. The elemental metals and alloys that form lithium alloys are preferably materials containing metal or metalloid elements (i.e., excluding carbon) from Groups 13 and 14, and more preferably aluminum, silicon, and tin elemental metals, and alloys or compounds containing these elements. These may be used alone, or two or more may be used in any combination and ratio.

[0180] <Physical properties of carbonaceous materials> When a carbonaceous material is used as the negative electrode active material, it is desirable that the material have the following physical properties. (X-ray parameters) The d value (interlayer distance) of the lattice plane (002 plane) of the carbonaceous material determined by X-ray diffraction according to the Gakushin method is usually 0.335 nm or more and usually 0.360 nm or less, preferably 0.350 nm or less, and more preferably 0.345 nm or less. The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction according to the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

[0181] (Volume-based average particle size) The volume-based average particle size of the carbonaceous material is the volume-based average particle size (median diameter) determined by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and particularly preferably 7 μm or more, and is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less.

[0182] If the volume-based average particle size is below the above range, the irreversible capacity increases, which may result in a loss of initial battery capacity, whereas if it exceeds the above range, the coating surface tends to be non-uniform when the electrode is prepared by coating, which may be undesirable in the battery manufacturing process. The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by mass aqueous solution (approximately 10 mL) of polyoxyethylene (20) sorbitan monolaurate, a surfactant, and measuring the particle size using a laser diffraction / scattering particle size distribution analyzer (e.g., LA-700 manufactured by Horiba, Ltd.) The median diameter determined by this measurement is defined as the volume-based average particle size of the carbonaceous material of the present invention.

[0183] (Raman R value) The Raman R value of the carbonaceous material is a value measured using laser Raman spectroscopy, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and is usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

[0184] If the Raman R value is below the above range, the crystallinity of the particle surface becomes too high, which may result in fewer sites for Li to enter between layers during charge and discharge. In other words, charge acceptance may decrease. Furthermore, when the negative electrode is densified by pressing after application to a current collector, the crystals tend to orient in a direction parallel to the electrode plate, which may result in a decrease in load characteristics. On the other hand, if the thickness exceeds the above range, the crystallinity of the particle surface decreases, and the reactivity with the non-aqueous electrolyte increases, which may lead to a decrease in efficiency and an increase in gas generation.

[0185] The Raman spectrum is measured using a Raman spectrometer (e.g., a Raman spectrometer manufactured by JASCO Corporation) by filling the sample into a measurement cell by gravity, and then rotating the cell in a plane perpendicular to the laser light while irradiating the sample surface in the cell with argon ion laser light (or semiconductor laser light). The Raman spectrum obtained is characterized by the intensity IA of the peak PA around 1580 cm-1 and the peak IA of 1360 cm-1. -1 The intensity ratio R (R=IB / IA) of the peaks PB and IA is calculated. The Raman R value calculated by this measurement is defined as the Raman R value of the carbonaceous material of the present invention.

[0186] The Raman measurement conditions are as follows: Laser wavelength: Ar ion laser 514.5nm (semiconductor laser 532nm) Measurement range: 1100cm -1 ~1730cm -1 Raman R value: background processing, Smoothing process: Simple average, convolution 5 points

[0187] (BET specific surface area) The BET specific surface area of ​​a carbonaceous material is the value of the specific surface area measured using the BET method, and is usually 0.1 m 2 ·g -1 More than 0.7m 2 ·g -1 More than 1.0m is preferable. 2 ·g -1 More than 1.5m is more preferable. 2 ·g -1 More than 100m is particularly preferable. 2 ·g -1 Less than or equal to 25m 2 ·g -1 Less than 15m is preferable 2 ·g -1 Less than 10m is more preferable 2 ·g -1 The following are particularly preferred:

[0188] If the BET specific surface area is below this range, when used as a negative electrode material, the lithium acceptance during charging tends to be poor, lithium tends to precipitate on the electrode surface, and stability may decrease. On the other hand, if the BET specific surface area is above this range, when used as a negative electrode material, the reactivity with a non-aqueous electrolyte increases, gas generation tends to increase, and it may be difficult to obtain a desirable battery. The specific surface area is measured by the BET method using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken) by pre-drying the sample at 350°C for 15 minutes under a nitrogen flow, and then using a nitrogen-helium mixed gas precisely adjusted so that the relative pressure of nitrogen to atmospheric pressure is 0.3, using the nitrogen adsorption BET single-point method by gas flow.

[0189] (Circularity) When the circularity of a carbonaceous material is measured as the degree of sphericity, it is preferable that it falls within the following range: Circularity is defined as "circularity = (perimeter of an equivalent circle having the same area as the projected shape of the particle) / (actual perimeter of the projected shape of the particle)", and a circularity of 1 corresponds to a theoretical perfect sphere. The circularity of carbonaceous material particles having a particle size in the range of 3 to 40 μm is preferably as close to 1 as possible, and is preferably 0.1 or more, more preferably 0.5 or more, more preferably 0.8 or more, even more preferably 0.85 or more, and particularly preferably 0.9 or more. The higher the circularity, the better the high-current-density charge-discharge characteristics. Therefore, if the circularity is below the above range, the packing property of the negative electrode active material decreases, the resistance between particles increases, and the short-time high-current-density charge-discharge characteristics may deteriorate.

[0190] Circularity is measured using a flow particle image analyzer (e.g., Sysmex FPIA). Approximately 0.2 g of sample is dispersed in a 0.2% by mass aqueous solution (approximately 50 mL) of the surfactant polyoxyethylene (20) sorbitan monolaurate, and the dispersion is irradiated with 28 kHz ultrasound at 60 W for 1 minute. The detection range is set to 0.6 to 400 μm, and measurements are made for particles with diameters in the range of 3 to 40 μm.

[0191] The method for improving the circularity is not particularly limited, but spherical particles obtained by spheronization are preferred because the shape of the interparticle voids is uniform when the particles are made into an electrode body. Examples of spheronization include a method of mechanically approaching a spherical shape by applying shear force or compression force, and a mechanical or physical treatment method of granulating multiple fine particles using a binder or the adhesive force of the particles themselves.

[0192] (tap density) The tap density of carbonaceous materials is typically 0.1 g cm -3 is greater than or equal to 0.5 g cm -3 More than 0.7 g cm is preferable. -3 More than 1 g cm is more preferable. -3 More than 2g cm is particularly preferable.-3 Preferably less than 1.8 g cm -3 Less than 1.6 g cm is more preferable. -3 The following is particularly preferred. If the tap density is below the above range, it may be difficult to increase the packing density when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if the tap density exceeds the above range, the gap between particles in the electrode becomes too small, making it difficult to ensure conductivity between particles, and it may be difficult to obtain desirable battery characteristics.

[0193] The tap density was measured by passing the sample through a sieve with a mesh size of 300 μm. 3 After dropping the sample into the tapping cell and filling it up to the top of the cell, a powder density measuring device (e.g., Tap Denser manufactured by Seishin Enterprise Co., Ltd.) is used to perform tapping 1,000 times with a stroke length of 10 mm, and the tap density is calculated from the volume and mass of the sample at that time.

[0194] (orientation ratio) The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. If the orientation ratio is below the above range, high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit of the orientation ratio of the carbonaceous material. The orientation ratio is measured by X-ray diffraction after the sample is pressure-molded. 0.47 g of sample is filled into a 17 mm diameter molding machine and compressed at 58.8 MN m-2 to obtain a molded body. The molded body is then set flush with the surface of the measurement sample holder using clay, and X-ray diffraction measurements are performed. The ratio of (110) diffraction peak intensity to (004) diffraction peak intensity is calculated from the obtained carbon (110) diffraction and (004) diffraction peak intensities.

[0195] The conditions for the X-ray diffraction measurement are as follows: "2θ" indicates the diffraction angle. Target: Cu (Kα line) graphite monochromator Slit: Divergence slit = 0.5 degrees Receiving slit = 0.15 mm Scattering slit = 0.5 degrees Measurement range and step angle / measurement time: (110) plane: 75 degrees ≦2θ≦80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦2θ≦57 degrees 1 degree / 60 seconds

[0196] (Aspect ratio (powder)) The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaks may occur during electrode formation, or a uniform coating surface may not be obtained, resulting in a deterioration in high current density charge / discharge characteristics. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

[0197] The aspect ratio is measured by magnifying and observing carbonaceous material particles with a scanning electron microscope. 50 randomly selected graphite particles are fixed to the edge of a metal with a thickness of 50 μm or less. The stage on which the sample is fixed is rotated and tilted for each sample, and the longest diameter A of the carbonaceous material particle and the shortest diameter B perpendicular to it are measured when observed in three dimensions. The average value of A / B is calculated.

[0198] (coverage rate) The negative electrode active material of the present invention may be coated with a carbonaceous material or graphite material. Among these, coating with an amorphous carbonaceous material is preferred from the viewpoint of lithium ion acceptability, and the coating rate is usually 0.5% to 30%, preferably 1% to 25%, and more preferably 2% to 20%. If this content is too high, the amorphous carbon portion of the negative electrode active material increases, tending to reduce the reversible capacity when assembled into a battery. If the content is too low, the amorphous carbon portion does not uniformly coat the core graphite particles, and strong granulation does not occur, tending to result in too small particle sizes when pulverized after firing. The content (coverage) of the organic compound-derived carbonized material in the final negative electrode active material can be calculated using the following formula based on the amount of the negative electrode active material, the amount of the organic compound, and the carbon residue rate measured by a micro method in accordance with JIS K 2270. Formula: Coating rate (%) of carbide derived from organic compound = (mass of organic compound × residual carbon rate × 100) / {mass of negative electrode active material + (mass of organic compound × residual carbon rate)}

[0199] (Internal void fraction) The internal void fraction of the negative electrode active material is usually 1% or more, preferably 3% or more, more preferably 5% or more, and still more preferably 7% or more. Also, it is usually less than 50%, preferably 40% or less, more preferably 30% or less, and still more preferably 20% or less. If this internal void fraction is too small, the amount of liquid inside the particles decreases, and the charge-discharge characteristics tend to deteriorate. If the internal void fraction is too large, when made into an electrode, the inter-particle gaps are small, and the diffusion of the electrolytic solution tends to be insufficient. Also, in this void, substances such as amorphous carbon, graphite-like substances, resins, etc., which buffer the expansion and contraction of metal particles capable of alloying with Li, may be present in the void or the void may be filled by being clogged.

[0200] <Metal particles capable of alloying with Li> As a method for confirming that the metal particles are metal particles capable of alloying with Li, examples include identification of the metal particle phase by X-ray diffraction, observation of the particle structure and elemental analysis by electron microscopy, elemental analysis by X-ray fluorescence, etc. Any conventionally known metal particles capable of alloying with Li can be used. However, from the viewpoints of capacity and cycle life, the metal particles are preferably a metal or its compound selected from the group consisting of, for example, Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Cu, Zn, Ge, In, Ti, etc. Also, an alloy composed of two or more metals may be used, or the metal particles may be alloy particles formed by two or more metal elements. Among these, a metal or its metal compound selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W is preferable. Examples of the metal compound include metal oxides, metal nitrides, metal carbides, etc. Also, an alloy composed of two or more metals may be used.

[0201] Among metal particles that can be alloyed with Li, Si or Si metal compounds are preferred. The Si metal compound is preferably a Si metal oxide. Si or Si metal compounds are preferred in terms of increasing capacity. In this specification, Si or Si metal compounds are collectively referred to as Si compounds. Specific examples of Si compounds include SiO x ,SiN x ,SiC x , SiZ x O y (Z=C, N), etc. The Si compound is preferably a Si metal oxide, which can be represented by the general formula SiO x This general formula is SiO x is obtained from silicon dioxide (SiO2) and metallic silicon (Si), and the value of x is usually 0≦x<2. SiO x has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals allow alkaline ions such as lithium ions to easily enter and exit, making it possible to obtain a high capacity. The Si metal oxide is specifically SiO x where x is 0≦x<2, more preferably 0.2 or more and 1.8 or less, even more preferably 0.4 or more and 1.6 or less, particularly preferably 0.6 or more and 1.4 or less, and it is particularly preferable that X = 0. Within this range, it is possible to achieve high capacity and simultaneously reduce irreversible capacity due to bonding between Li and oxygen.

[0202] Average particle size (d50) of metal particles that can be alloyed with Li From the viewpoint of cycle life, the average particle size (d50) of the metal particles that can be alloyed with Li is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.3 μm or more, and usually 10 μm or less, preferably 9 μm or less, and more preferably 8 μm or less. When the average particle size (d50) is within this range, volume expansion during charge and discharge is reduced, and good cycle characteristics can be obtained while maintaining charge and discharge capacity. The average particle size (d50) can be determined by a laser diffraction / scattering particle size distribution measurement method or the like.

[0203] · BET specific surface area of metal particles capable of alloying with Li The specific surface area of metal particles capable of alloying with Li by the BET method is usually 0.5 to 60 m 2 / g, preferably 1 to 40 m 2 / g. When the specific surface area of metal particles capable of alloying with Li by the BET method is within the above range, the charge-discharge efficiency and discharge capacity of the battery are high, the lithium insertion / extraction is fast in high-rate charge-discharge, and the rate characteristics are excellent, which is preferable.

[0204] · Oxygen content of metal particles capable of alloying with Li The oxygen content of metal particles capable of alloying with Li is not particularly limited, but is usually preferably 0.01 to 8% by mass, more preferably 0.05 to 5% by mass. The oxygen distribution state in the particles may be present near the surface, inside the particles, or uniformly inside the particles, but it is particularly preferable to be present near the surface. When the oxygen content of metal particles capable of alloying with Li is within the above range, the volume expansion accompanying charge-discharge is suppressed due to the strong bond between Si and O, and the cycle characteristics are excellent, which is preferable.

[0205] <Negative electrode active material containing metal particles capable of alloying with Li and graphite particles> The negative electrode active material containing Li-alloyable metal particles and graphite particles referred to in the present invention may be a mixture in which the Li-alloyable metal particles and graphite particles are mixed in the state of independent particles, or a composite in which the Li-alloyable metal particles are present on the surface or inside of graphite particles. In this specification, the composite (also referred to as composite particles) is not particularly limited as long as it contains Li-alloyable metal particles and a carbonaceous material, but is preferably a particle in which the Li-alloyable metal particles and the carbonaceous material are integrated by physical and / or chemical bonding. A more preferred form is one in which the Li-alloyable metal particles and the carbonaceous material are dispersed within the particles to such an extent that each solid component is present at least on the surface and inside the bulk of the composite particle, and the carbonaceous material is present to integrate them by physical and / or chemical bonding. A more specific preferred embodiment is a composite material comprising at least metal particles capable of being alloyed with Li and graphite particles, characterized in that the graphite particles, preferably natural graphite particles, have a curved, folded structure, and the metal particles capable of being alloyed with Li are present in gaps within the curved, folded structure. The gaps may be voids, or may contain a material, such as amorphous carbon, graphite, or resin, that buffers the expansion and contraction of the metal particles capable of being alloyed with Li.

[0206] · Content of metal particles that can be alloyed with Li The content of the metal particles capable of being alloyed with Li relative to the total of the metal particles capable of being alloyed with Li and the graphite particles is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and particularly preferably 5% by mass or more. Also, it is usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 20% by mass or less, particularly preferably 15% by mass or less, and most preferably 10% by mass or less. This range is preferable in that sufficient capacity can be obtained.

[0207] The alloy-based material negative electrode can be manufactured using any known method. Specifically, examples of methods for manufacturing a negative electrode include a method in which a binder, a conductive material, etc. are added to the above-mentioned negative electrode active material, and the resulting mixture is roll-molded into a sheet electrode, or a method in which the mixture is compression-molded into a pellet electrode. However, a more common method involves forming a thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material on a negative electrode current collector (hereinafter sometimes referred to as the "negative electrode current collector") by a coating method, vapor deposition method, sputtering method, plating method, or other method. In this case, a binder, a thickener, a conductive material, a solvent, etc. are added to the above-mentioned negative electrode active material to form a slurry, which is then applied to the negative electrode current collector, dried, and then pressed to densify, thereby forming a negative electrode active material layer on the negative electrode current collector.

[0208] Examples of the material for the negative electrode current collector include steel, copper alloy, nickel, nickel alloy, stainless steel, etc. Among these, copper foil is preferred from the viewpoints of ease of processing into a thin film and cost. The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be too low, and conversely, if it is too thin, it may be difficult to handle.

[0209] In order to improve the bonding effect with the negative electrode active material layer formed on the surface, it is preferable to roughen the surface of these negative electrode current collectors in advance. Examples of surface roughening methods include blasting, rolling with a rough-surface roll, mechanical polishing in which the current collector surface is polished with an abrasive cloth or paper having abrasive particles fixed thereto, a grindstone, an emery buff, a wire brush equipped with a steel wire, or the like, electrolytic polishing, and chemical polishing.

[0210] In addition, to reduce the mass of the negative electrode current collector and improve the energy density per unit mass of the battery, a perforated negative electrode current collector such as an expanded metal or a punched metal can be used. The mass of this type of negative electrode current collector can also be freely changed by changing its aperture ratio. Furthermore, when negative electrode active material layers are formed on both sides of this type of negative electrode current collector, the rivet effect through the holes makes the negative electrode active material layers even less likely to peel off. However, if the aperture ratio is too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes smaller, which may actually reduce the adhesive strength.

[0211] The slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener, etc. to the negative electrode material. In this specification, the term "negative electrode material" refers to a material in which the negative electrode active material and the conductive material are combined. The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, particularly 95% by mass or less. If the content of the negative electrode active material is too low, the capacity of a secondary battery using the resulting negative electrode tends to be insufficient. If the content of the negative electrode active material is too high, the content of the conductive agent tends to be relatively insufficient, making it difficult to ensure the electrical conductivity of the negative electrode. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials should be set to satisfy the above range.

[0212] Examples of conductive materials used in the negative electrode include metal materials such as copper and nickel; and carbon materials such as graphite and carbon black. These may be used alone, or two or more may be used in any combination and ratio. Using a carbon material as the conductive material is particularly preferred because the carbon material also functions as an active material. The content of the conductive material in the negative electrode material is usually 3% by mass or more, particularly 5% by mass or more, and usually 30% by mass or less, particularly 25% by mass or less. If the content of the conductive material is too low, the conductivity tends to be insufficient. If the content is too high, the content of the negative electrode active material, etc., will be relatively insufficient, which tends to reduce the battery capacity and strength. When two or more conductive materials are used in combination, the total amount of the conductive materials should be within the above range.

[0213] Any binder can be used for the negative electrode as long as it is safe against the solvents and electrolytes used in electrode production. Examples include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber-isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer. These may be used alone, or two or more may be used in any combination and ratio. The binder content is typically 0.5 parts by mass or more, particularly 1 part by mass or more, per 100 parts by mass of negative electrode material, and typically 10 parts by mass or less, particularly 8 parts by mass or less. If the binder content is too low, the resulting negative electrode tends to have insufficient strength. If the binder content is too high, the relative content of the negative electrode active material, etc., will be insufficient, resulting in insufficient battery capacity and conductivity. When two or more binders are used in combination, the total amount of the binders should be within the above range.

[0214] Examples of thickeners used in the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphated starch, and casein. These may be used alone or in any combination and ratio of two or more. A thickener may be used as needed, but when used, it is preferable that the content of the thickener in the negative electrode active material layer is generally in the range of 0.5 mass % or more and 5 mass % or less.

[0215] The slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive agent, a binder, and a thickener as needed, and using an aqueous or organic solvent as a dispersion medium. Water is typically used as the aqueous solvent, but organic solvents such as alcohols (e.g., ethanol) and cyclic amides (e.g., N-methylpyrrolidone) can also be used in combination with water in an amount of up to 30% by mass. Examples of organic solvents include cyclic amides (e.g., N-methylpyrrolidone), linear amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide), aromatic hydrocarbons (e.g., anisole, toluene, xylene), and alcohols (e.g., butanol, cyclohexanol). Among these, cyclic amides (e.g., N-methylpyrrolidone), linear amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide), and the like are preferred. These solvents may be used alone or in any combination and ratio of two or more.

[0216] The obtained slurry is applied to the above-mentioned negative electrode current collector, dried, and then pressed to form a negative electrode active material layer. The application method is not particularly limited, and any known method can be used. The drying method is also not particularly limited, and any known method such as natural drying, heat drying, or reduced pressure drying can be used.

[0217] <Negative electrode structure and manufacturing method> The electrode can be manufactured by any known method as long as it does not significantly impair the effects of the present invention. For example, the electrode can be formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, applying the slurry to a current collector, drying it, and then pressing it. When an alloy-based material is used, a method of forming a thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material by a method such as vapor deposition, sputtering, or plating may also be used.

[0218] (electrode density) There are no particular restrictions on the electrode structure when the negative electrode active material is made into an electrode, but the density of the negative electrode active material present on the current collector must be 1 g cm -3More than 1.2 g cm is preferable. -3 More preferably, 1.3 g cm -3 More than 2.2 g cm is particularly preferable. -3 Preferably less than 2.1 g cm -3 Less than 2.0 g cm is preferable. -3 Even better is 1.9 g cm -3 The following is particularly preferred. If the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles may be destroyed, increasing the initial irreversible capacity and possibly leading to deterioration of high current density charge / discharge characteristics due to reduced permeability of the nonaqueous electrolyte solution near the current collector / negative electrode active material interface. If the density is below the above range, the conductivity between the negative electrode active materials may decrease, increasing the battery resistance and reducing the capacity per unit volume.

[0219] 2-2. Positive electrode <Cathode active material> The positive electrode active material (lithium transition metal compound) used in the positive electrode will be described below. <Lithium transition metal compounds> Lithium transition metal compounds are compounds that have a structure that allows for the desorption and insertion of Li ions, and examples of such compounds include sulfides, phosphate compounds, and lithium transition metal composite oxides. Sulfides include compounds with a two-dimensional layer structure such as TiS2 and MoS2, and compounds with the general formula Me x Examples of suitable lithium transition metal oxides include those with a spinel structure that allows three-dimensional diffusion, and those with a layered structure that allows two-dimensional diffusion of lithium ions. Those with a spinel structure are generally represented as LiMe2O4 (Me is at least one or more transition metals), and specifically include LiFePO4, LiCoPO4, LiNiPO4, LiMnPO4, etc. Those with a spinel structure are generally represented as LiMe2O4 (Me is at least one or more transition metals), and specifically include LiMn2O4, LiCoMnO4, LiNi 0.5 Mn 1.5O4, LiCoVO4, etc. Those with a layered structure are generally expressed as LiMeO2 (Me is at least one or more transition metals). Specifically, LiCoO2, LiNiO2, LiNi 1-x Co x O2, LiNi 1-x-y Co x Mn y O2, LiNi 0.5 Mn 0.5 O2, Li 1.2 Cr 0.4 Mn 0.4 O2, Li 1.2 Cr 0.4 Ti 0.4 O2, LiMnO2, etc.

[0220] <composition> The lithium-containing transition metal compound may be, for example, a lithium transition metal compound represented by the following composition formula (F) or (G). 1) In the case of a lithium transition metal compound represented by the following composition formula (F): Li 1+x MO2…(F) However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn, or Ni, Mn, and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. The Li-rich portion represented by x may be substituted by the transition metal site M.

[0221] In the composition formula (F), the atomic ratio of oxygen is described as 2 for convenience, but some degree of non-stoichiometry is acceptable. Furthermore, x in the composition formula is the charge composition during the manufacturing stage of the lithium transition metal compound. Batteries on the market are usually aged after assembly. Therefore, the amount of Li in the positive electrode may be lost during charging and discharging. In such cases, composition analysis may reveal that x is greater than or equal to -0.65 and less than 1 when the battery is discharged to 3 V.

[0222] Furthermore, lithium transition metal compounds that are calcined at high temperatures in an oxygen-containing gas atmosphere to enhance the crystallinity of the positive electrode active material have excellent battery characteristics. Furthermore, the lithium transition metal compound represented by composition formula (F) may be a solid solution with Li2MO3, called the 213 layer, as shown in the following general formula (F'). αLi2MO3·(1-α)LiM'O2···(F') In the general formula, α is a number that satisfies 0<α<1.

[0223] M is at least one metal element having an average oxidation number of 4+, and specifically at least one metal element selected from the group consisting of Mn, Zr, Ti, Ru, Re, and Pt. M' is at least one metal element having an average oxidation number of 3+, preferably at least one metal element selected from the group consisting of V, Mn, Fe, Co, and Ni, and more preferably at least one metal element selected from the group consisting of Mn, Co, and Ni.

[0224] 2) A lithium transition metal compound represented by the following general formula (B): Li a M b Mn 2-b-a ]O 4+δ (G) Here, M is an element composed of at least one transition metal selected from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg. The value of b is usually greater than or equal to 0.4 and less than or equal to 0.6. If the value of b is within this range, the energy density per unit mass of the lithium transition metal compound is high.

[0225] The value of a is usually between 0 and 0.3. In the above formula, a is the charge composition of the lithium transition metal compound during manufacturing. Batteries on the market are usually aged after assembly. Therefore, the amount of Li in the positive electrode may be lost during charging and discharging. In this case, a may be measured as between -0.65 and 1 when discharged to 3V in a composition analysis.

[0226] If the value of a is within this range, the energy density per unit mass of the lithium transition metal compound is not significantly impaired, and good load characteristics are obtained. Furthermore, the value of δ is typically in the range of ±0.5. If the value of δ is within this range, the stability of the crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode made using this lithium transition metal compound are good.

[0227] The chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound, will be explained in more detail below. To determine a and b in the composition formula of the lithium transition metal compounds, each transition metal and lithium are analyzed using an inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the Li / Ni / Mn ratio.

[0228] From a structural point of view, it is thought that the lithium related to a is substituted into the same transition metal site. Here, the lithium related to a makes the average valence of M and manganese greater than 3.5 due to the principle of charge neutrality. The lithium transition metal compound may be fluorinated, and may be LiMnO 4-x F 2x It is written as follows.

[0229] <blend> Specific examples of the lithium transition metal compound having the above composition include Li 1+x Ni 0.5 Mn 0.5 O2, Li 1+xNi 0.85 Co 0.10 Al 0.05 O2, Li 1+x Ni 0.33 Mn 0.33 Co 0.33 O2, Li 1+x Ni 0.45 Mn 0.45 Co 0.1 O2, Li 1+x Mn 1.8 Al 0.2 O4, Li 1+x Mn 1.5 Ni 0.5 O4, etc. These lithium transition metal compounds may be used alone or in combination of two or more.

[0230] <Introduction of different elements> The lithium transition metal compound may contain a foreign element selected from one or more of B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te, Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si, and Sn. The foreign element may be incorporated into the crystalline structure of the lithium transition metal compound, or may be distributed as a single element or a compound on the particle surface, grain boundaries, or the like without being incorporated into the crystalline structure of the lithium transition metal compound.

[0231] [Positive electrodes for lithium secondary batteries] The positive electrode for a lithium secondary battery is obtained by forming a positive electrode active material layer containing the above-mentioned lithium transition metal compound powder for a lithium secondary battery positive electrode material and a binder on a current collector. The positive electrode active material layer is usually produced by dry-mixing a positive electrode material, a binder, and optionally a conductive material, a thickener, and the like into a sheet, which is then pressed onto the positive electrode current collector, or by dissolving or dispersing these materials in a liquid medium to form a slurry, which is then applied to the positive electrode current collector and dried.

[0232] The positive electrode current collector is typically made of a metal material such as aluminum, stainless steel, nickel plating, titanium, or tantalum, or a carbon material such as carbon cloth or carbon paper. Metallic materials may have shapes such as metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, or foamed metal, while carbon materials may have shapes such as carbon plate, carbon thin film, or carbon cylinder. The thin film may be formed into a mesh, as appropriate.

[0233] When a thin film is used as a positive electrode current collector, its thickness is not limited, but is preferably in the range of 1 μm to 100 mm. If the thickness is less than this range, the strength required as a current collector may be insufficient, while if the thickness is greater than this range, handling may be impaired. The binder used in manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material may be used as long as it is stable in the liquid medium used in manufacturing the electrode. Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and their hydrogenated products; and EPDM (ethylene-propylene copolymer). Examples of suitable polymers include thermoplastic elastomeric polymers such as styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, and their hydrogenated derivatives; soft resinous polymers such as syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions having ionic conductivity for alkali metal ions (especially lithium ions). These materials may be used singly or in any combination and ratio of two or more.

[0234] The proportion of the binder in the positive electrode active material layer is usually 0.1 mass % or more and 80 mass % or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently held, resulting in insufficient mechanical strength of the positive electrode and possibly deteriorating battery performance such as cycle characteristics. On the other hand, if the proportion is too high, it may lead to a decrease in battery capacity and conductivity. The positive electrode active material layer typically contains a conductive material to enhance conductivity. While there are no particular limitations on the type of conductive material, specific examples include metal materials such as copper and nickel, graphite (e.g., natural graphite and artificial graphite), carbon black (e.g., acetylene black), and carbon materials (e.g., amorphous carbon (e.g., needle coke)). These materials may be used alone or in any combination and ratio of two or more. The proportion of the conductive material in the positive electrode active material layer is typically 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, while if it is too high, the battery capacity may decrease.

[0235] The liquid medium for forming the slurry is not particularly limited as long as it can dissolve or disperse the lithium transition metal compound powder (positive electrode material), binder, and optional conductive material and thickener. Either an aqueous or organic solvent can be used. Examples of aqueous solvents include water and alcohol. Examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, and hexane. When using an aqueous solvent, a dispersant is added along with the thickener, and a slurry is formed using a latex such as SBR. These solvents may be used alone or in any combination of two or more in any ratio.

[0236] The content of the lithium transition metal compound powder as the positive electrode material in the positive electrode active material layer is usually 10 mass % or more and 99.9 mass % or less. If the content of the lithium transition metal compound powder in the positive electrode active material layer is too high, the strength of the positive electrode tends to be insufficient, and if it is too low, the capacity may be insufficient. The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

[0237] The electrode density after pressing of the positive electrode is usually 2.2 g / cm 3 More than 4.2g / cm 3 The following is the result. The positive electrode active material layer obtained by coating and drying is preferably compacted by a roller press or the like in order to increase the packing density of the positive electrode active material. In this way, a positive electrode for a lithium secondary battery can be prepared.

[0238] 2-3.Separator A separator is usually interposed between the positive electrode and the negative electrode to prevent short-circuiting, and in this case, the nonaqueous electrolyte solution of the present invention is usually impregnated into the separator before use. The separator is not particularly limited in material or shape, and any known material may be used as long as it does not significantly impair the effects of the present invention. Among these, it is preferable to use a material that is stable to the nonaqueous electrolyte solution of the present invention, such as a resin, glass fiber, or inorganic material, and that is in the form of a porous sheet or nonwoven fabric having excellent liquid retention.

[0239] Examples of materials that can be used for the resin and glass fiber separator include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. Among these, glass filters and polyolefins are preferred, and polyolefins are even more preferred. These materials may be used alone or in any combination and ratio of two or more.

[0240] The thickness of the separator is optional, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is thinner than the above range, the insulating properties and mechanical strength may be reduced. On the other hand, if the separator is thicker than the above range, not only may the battery performance such as rate characteristics be reduced, but also the energy density of the nonaqueous electrolyte secondary battery as a whole may be reduced.

[0241] Furthermore, when a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is optional, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, and is usually 90% or less, preferably 85% or less, more preferably 75% or less. If the porosity is too low below the above range, the membrane resistance tends to increase, resulting in poor rate performance. If the porosity is too high above the above range, the mechanical strength of the separator tends to decrease, and its insulating properties tend to deteriorate.

[0242] The average pore size of the separator can also be any value, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore size exceeds the above range, short circuits are likely to occur. If the average pore size is below the above range, the membrane resistance increases, which may result in a decrease in rate characteristics. On the other hand, inorganic materials include, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and these are used in particulate or fibrous form.

[0243] As for the form, a thin film such as a nonwoven fabric, a woven fabric, or a microporous film is used. A thin film with a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the above-mentioned independent thin film, a separator can be used in which a composite porous layer containing the above-mentioned inorganic particles is formed on the surface layer of the positive electrode and / or negative electrode using a resin binder. For example, a porous layer can be formed on both sides of the positive electrode using alumina particles with a 90% particle size of less than 1 μm and a fluororesin as a binder.

[0244] The separator's performance in non-electrolyte secondary batteries can be assessed by its Gurley value. The Gurley value indicates the resistance to air permeation in the film thickness direction. It is expressed as the number of seconds required for 100 ml of air to pass through the film. A smaller value indicates easier air permeation, while a larger value indicates less air permeation. In other words, a smaller value indicates better interconnectivity in the film thickness direction, while a larger value indicates poorer interconnectivity in the film thickness direction. Interconnectivity refers to the degree of connection of pores in the film thickness direction. A separator of the present invention with a low Gurley value can be used for a variety of applications. For example, when used as a separator for a non-aqueous lithium secondary battery, a low Gurley value indicates easy lithium ion migration, which is desirable because it leads to excellent battery performance. The Gurley value of the separator can be any value, but is preferably 10 to 1,000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and even more preferably 20 to 500 seconds / 100 ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, and this is preferable as a separator.

[0245] 2-4.Battery design <Electrode group> The electrode group may have either a laminated structure of the positive electrode plate and the negative electrode plate sandwiched between the separator, or a structure of the positive electrode plate and the negative electrode plate spirally wound with the separator sandwiched between them. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less.

[0246] If the electrode group occupancy rate is below the above range, the battery capacity will be small, whereas if it exceeds the above range, the void space will be small, and the battery will become hot, causing the components to expand and the vapor pressure of the electrolyte liquid components to increase, resulting in an increase in internal pressure, which will degrade various battery characteristics such as repeated charge / discharge performance and high-temperature storage, and may even activate the gas release valve that releases the internal pressure to the outside.

[0247] <Outer case> The material of the outer case is not particularly limited as long as it is a substance that is stable against the non-aqueous electrolyte solution used. Specifically, metals such as nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminate film of resin and aluminum foil (laminate film) can be used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloy and laminate film are preferably used.

[0248] Examples of exterior cases using metals include those in which metals are welded together to form a sealed, airtight structure by laser welding, resistance welding, or ultrasonic welding, or those in which the metals are used via a resin gasket to form a crimped structure. Examples of exterior cases using the above-mentioned laminate film include those in which resin layers are heat-sealed to form a sealed, airtight structure. In order to improve sealing properties, a resin different from the resin used in the laminate film may be interposed between the resin layers. In particular, when a sealed structure is formed by heat-sealing the resin layers via a current collecting terminal, a resin having a polar group or a modified resin into which a polar group has been introduced is preferably used as the interposed resin, since the metal and the resin are bonded together.

[0249] <Protection element> The protective element may be a PTC (Positive Temperature Coefficient), whose resistance increases when abnormal heat is generated or excessive current flows, a thermal fuse, a thermistor, or a valve (current cutoff valve) that cuts off the current flowing in the circuit due to a sudden rise in the internal pressure or temperature of the battery when abnormal heat is generated. It is preferable to select the above protective element so that it will not operate under normal use at high current, and it is even more preferable to design it so that abnormal heat generation or thermal runaway does not occur even without the protective element.

[0250] (exterior body) The nonaqueous electrolyte secondary battery of the present invention is generally constructed by housing the above-mentioned nonaqueous electrolyte, negative electrode, positive electrode, separator, etc. in an exterior body (exterior case). There are no limitations on this exterior body, and any known exterior body can be used as long as it does not significantly impair the effects of the present invention. The material of the outer case is not particularly limited as long as it is stable against the non-aqueous electrolyte solution used. Specifically, metals such as nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, magnesium alloy, nickel, titanium, etc., or a laminate film of resin and aluminum foil (laminate film) are used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloy and laminate film are preferably used.

[0251] Examples of exterior cases using the above metals include those in which the metals are welded together to form a sealed, airtight structure by laser welding, resistance welding, or ultrasonic welding, or those in which the metals are used via a resin gasket to form a crimped structure. Examples of exterior cases using the above laminate film include those in which the resin layers are heat-sealed to form a sealed, airtight structure. In order to improve sealing properties, a resin different from the resin used in the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed via a current collecting terminal to form a sealed structure, the metal and the resin are joined, so a resin having a polar group or a modified resin into which a polar group has been introduced is preferably used as the interposed resin.

[0252] The shape of the exterior case may also be arbitrary, and may be, for example, cylindrical, rectangular, laminated, coin-shaped, large, or the like. [Example]

[0253] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The abbreviations for the compounds used in the examples are shown below. Lithium fluorosulfonate; FSLi Lithium difluorophosphate;DFPLi Hexamethylene diisocyanate; HMDI 1,3-Bis(isocyanatomethyl)cyclohexane; BIMCH Lithium bis(fluorosulfonyl)imide; LiFSI p-Toluenesulfonyl isocyanate;TSI Diisocyanatosulfone;DIS Fluorosulfonylmethane; FSO2Me Ethyl isocyanate; EtNCO Isopropyl isocyanate; iso-PrNCO tert-Butyl isocyanate; tert-BuNCO Methyl fluorosulfonate; FSO3Me Benzenesulfonyl fluoride; FSO2Ph Benzylsulfonyl fluoride; FSO2CH2Ph 1,3-Propane sultone: PS Maleic anhydride: MAL Vinylene carbonate: VC Vinyl ethylene carbonate: VEC

[0254] <Examples 1-1 to 1-7, Comparative Example 1-1> [Preparation of positive electrode] 85% by mass of lithium-nickel-cobalt-manganese composite oxide (NMC) as the positive electrode active material, 10% by mass of acetylene black as the conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as the binder were mixed in N-methylpyrrolidone solvent using a disperser to form a slurry. This slurry was evenly applied to both sides of a 21 μm thick aluminum foil, dried, and pressed to form a positive electrode.

[0255] [Preparation of negative electrode] 50 g of Si microparticles with an average particle size of 0.2 μm were dispersed in 2000 g of flake graphite with an average particle size of 35 μm, and then placed in a hybridization system (manufactured by Nara Machinery Works). The mixture was circulated or retained in the system for 180 seconds at a rotor rotation speed of 7000 rpm to obtain a composite of Si and graphite particles. The resulting composite was mixed with coal tar pitch as an organic compound to form a carbonaceous material, so that the coverage after firing would be 7.5%, and then kneaded and dispersed using a twin-screw kneader. The resulting dispersion was introduced into a firing furnace and fired at 1000°C for 3 hours under a nitrogen atmosphere. The resulting fired material was further pulverized in a hammer mill and sieved (45 μm) to produce a negative electrode active material. The silicon element content (Si content), average particle size d50, tap density, and specific surface area measured using the above-mentioned measurement methods were 2.0 mass%, 20 μm, and 1.0 g / cm, respectively. 3 , 7.2m 2 / g. Negative electrode active materials 1 to 4 with various Si contents shown in Table 1 were prepared using the same method as above. The Si content is the mass concentration (mass%) determined by analysis of the Si fine particles relative to the total (100 mass%) of the Si fine particles and graphite particles. In other examples, the Si contents shown as 2.0 wt%, 7.3 wt%, 12.5 wt%, and 17.4 wt% were obtained by using negative electrode active materials 1, 2, 3, and 4 shown in Table 1 below, respectively.

[0256] [Table 1]

[0257] 97.5 parts by mass of the negative electrode active material, 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose: 1% by mass) as a thickener, and 1.5 parts by mass of an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) were added as a thickener and binder, respectively, and mixed in a disperser to form a slurry. This slurry was uniformly applied to one side of a 10 μm thick copper foil, dried, and then pressed to form a negative electrode.

[0258] [Preparation of non-aqueous electrolyte] Under a dry argon atmosphere, thoroughly dried LiPF6 was dissolved at 1.2 mol / L (as the concentration in the non-aqueous electrolyte) in a mixture of ethylene carbonate (EC), fluoroethylene carbonate (MFEC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (volume ratio: 2:1:4:3) (this solution is referred to as Reference Electrolyte 1). Compounds (additives) were added to the total Reference Electrolyte 1 in the proportions listed in Table 2 below to prepare the electrolyte. Comparative Example 1-1 is Reference Electrolyte 1 itself.

[0259] [Manufacturing non-aqueous electrolyte batteries (laminated type)] The positive electrode, negative electrode, and polyolefin separator were stacked in this order, and the resulting battery element was wrapped in an aluminum laminate film, and the electrolyte solution described below was injected into the battery element, followed by vacuum sealing to prepare a sheet-shaped nonaqueous electrolyte secondary battery.

[0260] <Evaluation of non-aqueous electrolyte secondary batteries> [High temperature cycle test] In a thermostatic chamber at 25°C, a laminated cell nonaqueous electrolyte secondary battery was charged at a constant current of 0.05 C to 4.0 V (hereinafter referred to as "CC charging") and then discharged at a constant current of 0.05 C to 2.75 V (hereinafter referred to as "CC discharging"). It was then charged at a constant current and constant voltage of 0.2 C to 4.1 V (hereinafter referred to as "CC-CV charging") (0.05 C cut), and then discharged at 0.2 C to 2.75 V. This cycle of CC-CV charging to 4.2 V at 0.2 C and then discharged at 0.2 C to 2.75 V was repeated twice for conditioning. Here, 1 C refers to the current value required to discharge the battery to its reference capacity in 1 hour; for example, 0.2 C refers to 1 / 5 of that current value.

[0261] After conditioning, the cell was charged in a constant temperature bath at 45°C by CCCV charging at 0.5C up to 4.2V, and then discharged at a constant current of 0.5C down to 2.75V. This cycle was repeated 100 and 200 times.

[0262] The capacity retention rate at the 100th cycle was calculated as follows. Capacity retention rate at 100 cycles =100th cycle capacity / 1st cycle capacity x 100 Furthermore, the capacity retention rate at the 100th cycle of the nonaqueous electrolyte secondary battery using reference electrolyte 1 of Comparative Example 1-1 itself was set to 100, and the capacity retention rate at the 100th cycle of each battery having a negative electrode active material with a predetermined Si content of Examples 1-1 to 1-7 was calculated relative to this. These values ​​are shown in Table 2. In the table, the "%" of the compound (additive) indicates the mass % of the compound (additive) in 100 mass % of the non-aqueous electrolyte solution.

[0263] In Examples 1-1 to 1-7 and Comparative Example 1-1, silicon powder was used as the negative electrode active material, and batteries were fabricated and tested as follows: In the tables, the Si content is expressed as 100 mass %. [Preparation of non-aqueous electrolyte] Under a dry argon atmosphere, thoroughly dried LiPF was dissolved at 1 mol / L (as the concentration in the non-aqueous electrolyte) in a mixture of monofluoroethylene carbonate and ethyl methyl carbonate (EMC) (volume ratio: 2:8) (this is referred to as reference electrolyte 1'"). Electrolytes were prepared by adding compounds to the total amount of reference electrolyte 1' in the proportions shown in Table 2 below. However, in Comparative Example 1-1, the Si content of which is indicated as 100 mass % is an example in which reference electrolyte 1' itself was used.

[0264] [Preparation of positive electrode] 85% by mass of lithium-nickel-cobalt-manganese composite oxide (NMC) as the positive electrode active material, 10% by mass of acetylene black as the conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as the binder were mixed in N-methylpyrrolidone solvent using a disperser to form a slurry. This slurry was evenly applied to both sides of a 21 μm thick aluminum foil, dried, and pressed to form a positive electrode.

[0265] [Preparation of negative electrode] Silicon powder as the negative electrode active material, graphite powder as the conductive agent, and a binder were mixed, and then N-methylpyrrolidone solution was added and mixed using a disperser to form a slurry. The resulting slurry was uniformly coated on a 20 μm thick copper foil negative electrode current collector to form a negative electrode, and the active material was cut into a 30 mm wide and 40 mm long negative electrode. This negative electrode was then dried under reduced pressure at 60°C for 12 hours before use.

[0266] [Manufacturing non-aqueous electrolyte batteries (laminated type)] The positive electrode, negative electrode, and polyolefin separator were stacked in this order, and the resulting battery element was wrapped in an aluminum laminate film, and the electrolyte solution described below was injected into the battery element, followed by vacuum sealing to prepare a sheet-shaped nonaqueous electrolyte secondary battery.

[0267] <Evaluation of non-aqueous electrolyte secondary batteries> [High temperature cycle test] In a thermostatic bath at 25°C, a coin-type nonaqueous electrolyte secondary battery was charged at a constant current of 0.05 C for 4 hours (hereinafter referred to as "CC charging"), followed by constant current-constant voltage charging at 0.2 C to 4.0 V (hereinafter referred to as "CC-CV charging"). It was then discharged at 0.2 C to 2.75 V. It was then CC-CV charged at 0.2 C to 4.0 V, and then discharged at 0.2 C to 2.75 V to stabilize the nonaqueous electrolyte secondary battery. It was then CC-CV charged at 0.2 C to 4.2 V, followed by discharging at 0.2 C to 2.75 V for initial conditioning.

[0268] After conditioning, the cell was subjected to CCCV charging at 0.5 C to 4.2 V in a constant temperature bath at 45° C., and then discharged at a constant current of 0.5 C to 2.75 V. This cycle was repeated 200 times.

[0269] [Table 2]

[0270] The capacity retention rate at the 200th cycle was calculated as follows. Capacity retention rate at 200 cycles = 200th cycle capacity / 1st cycle capacity x 100 Furthermore, the capacity retention rate at the 200th cycle of the nonaqueous electrolyte secondary battery using reference electrolyte 1 or reference electrolyte 1' in Comparative Example 1-1 was set to 100, and the capacity retention rate at the 200th cycle of each battery having a negative electrode active material with a predetermined Si content in Examples 1-1 to 1-7 was calculated relative to this. These values ​​are shown in Table 3. In the table, the "%" of the compound (additive) indicates the mass % of the compound (additive) in 100 mass % of the non-aqueous electrolyte solution.

[0271] [Table 3]

[0272] As shown in Tables 2 and 3, while the capacity retention rate of the nonaqueous electrolyte secondary battery (Comparative Example 1-1) in which no specific compound was added to the nonaqueous electrolyte was 100, the capacity retention rates of the nonaqueous electrolyte secondary batteries of Examples 1-1 to 1-7 all exceeded 100. Table 2 shows that the cycle characteristics were improved regardless of the Si content in the negative electrode active material.

[0273] <Examples 2-1 to 2-14, Comparative Example 2-1> [Preparation of positive and negative electrodes] The positive and negative electrode active materials prepared in Example 1 were used.

[0274] [Preparation of non-aqueous electrolyte] Under a dry argon atmosphere, thoroughly dried LiPF6 was dissolved in a mixture of EC and DEC (volume ratio 3:7) at 1.0 mol / L (as the concentration in the non-aqueous electrolyte), and then vinylene carbonate (VC) and fluoroethylene carbonate were added at 2.0 mass% each (this is referred to as reference electrolyte 2). The compounds were added to the total amount of reference electrolyte 2 in the proportions listed in Table 4 below to prepare the electrolyte. Comparative Example 2-1 is reference electrolyte 2 itself.

[0275] <Evaluation of non-aqueous electrolyte secondary batteries> [High temperature cycle test] In a thermostatic chamber at 25°C, the laminated cell nonaqueous electrolyte secondary battery was subjected to constant current-constant voltage charging at a current equivalent to 0.05 C up to 4.0 V. It was then discharged to 2.5 V at 0.05 C. CC-CV charging was then performed at 0.2 C up to 4.0 V, followed by discharging at 0.2 C to 2.5 V to stabilize the nonaqueous electrolyte secondary battery. CC-CV charging was then performed at 0.2 C up to 4.2 V, followed by discharging at 0.2 C to 2.5 V for initial conditioning.

[0276] After the initial conditioning, the cell was subjected to CC-CV charging at 0.5 C to 4.2 V in a constant temperature bath at 45° C., and then discharged at a constant current of 0.5 C to 2.5 V. This cycle was repeated 100 times.

[0277] The capacity retention rate at the 100th cycle was calculated as follows. Capacity retention rate at 100 cycles =100th cycle capacity / 1st cycle capacity x 100 Furthermore, the capacity retention rate at the 100th cycle of the nonaqueous electrolyte secondary battery using reference electrolyte 2 itself in Comparative Example 2-1 was set to 100, and the capacity retention rate at the 100th cycle of each battery having a negative electrode active material with a predetermined Si content in Examples 2-1 to 2-14 was calculated relative to this. These values ​​are shown in Table 4. In the table, the "%" of the compound (additive) indicates the mass % of the compound (additive) in 100 mass % of the non-aqueous electrolyte solution.

[0278] [Table 4]

[0279] As shown in Table 4, while the capacity retention rate after the high-temperature cycle test of the nonaqueous electrolyte secondary battery (Comparative Example 2-1) in which no specific compound was added to the nonaqueous electrolyte was 100, the capacity retention rates of the nonaqueous electrolyte secondary batteries of Examples 2-1 to 2-14 all exceeded 100. Furthermore, as shown in Examples 2-1, 2-4, and 2-5, it can be seen that the cycle characteristics were improved regardless of the Si content in the negative electrode active material.

[0280] <Examples 3-1 to 3-7, Comparative Example 3-1> [Preparation of positive and negative electrodes] The positive and negative electrode active materials prepared in Example 1 were used.

[0281] [Preparation of non-aqueous electrolyte] The electrolyte used was standard electrolyte 1. The electrolytes were prepared by adding compounds to the total amount of standard electrolyte 1 in the proportions shown in Table 5 below. However, Comparative Example 3-1 was standard electrolyte 1 itself. [Manufacturing non-aqueous electrolyte batteries (laminated type)] In the same manner as in Example 1, a sheet-shaped non-aqueous electrolyte secondary battery was produced.

[0282] For batteries labeled as having a 100% Si content by mass, the batteries were fabricated under the same conditions as those for the battery fabrication and high-temperature cycle test described for the battery labeled as having a 100% Si content in Example 1, and a high-temperature cycle test was performed. Comparative Example 3-1 labeled as having a 100% Si content is an example in which the reference electrolyte 1' itself was used. However, for the positive electrode of the battery labeled as having a 100% Si content in Example 3-5, a positive electrode fabricated as follows was used. 94% by mass of lithium cobalt oxide (LiCoO2) as the positive electrode active material, 3% by mass of acetylene black as the conductive material, and 3% by mass of polyvinylidene fluoride (PVdF) as the binder were mixed in N-methylpyrrolidone solvent using a disperser to form a slurry, which was then uniformly applied to both sides of a 21 μm thick aluminum foil, dried, and pressed to form a positive electrode.

[0283] <Evaluation of non-aqueous electrolyte secondary batteries> [Battery swelling] The thickness of the battery was measured after initial conditioning under the same conditions as in Example 1, and then a high-temperature cycle test (200 cycles) was performed in the same manner as in Example 2. The change in battery thickness was then measured in the same manner as after initial conditioning, and the change in electrode thickness of the battery due to cycling was defined as "battery swelling." The evaluated battery can store gas generated during cycling in a gas reservoir within the cell. Therefore, it can be seen that the "electrode swelling" described here does not refer to swelling due to generated gas, but rather to swelling due to changes in electrode thickness due to cycling.

[0284] The numerical values ​​in Table 5 were calculated by setting the "battery swelling" of the nonaqueous electrolyte secondary battery using reference electrolyte 1 or reference electrolyte 1' of Comparative Example 3-1 after a high-temperature cycle test (200 cycles) as 100, and calculating the numerical value of "battery swelling" of each battery having a negative electrode active material with a predetermined Si content in Examples 3-1 to 3-7 relative to the "battery swelling" of Comparative Example 3-1 as 100. In Table 5, the "%" of the compound (additive) indicates the mass % of the compound (additive) in 100 mass % of the nonaqueous electrolyte.

[0285] [Table 5]

[0286] As shown in Table 5, the nonaqueous electrolyte secondary battery (Comparative Example 3-1) in which no specific compound was added to the nonaqueous electrolyte had a "battery swelling" of 100 after the high-temperature cycle test (200 cycles), while the nonaqueous electrolyte secondary batteries of Examples 3-1 to 3-7 all had "battery swelling" values ​​below or only slightly above 100, demonstrating that cycle characteristics were improved regardless of the Si content in the negative electrode active material. In particular, significant improvements were observed when the Si content was 7.3 mass % and 12.5 mass %.

[0287] <Examples 4-1 to 4-14, Comparative Example 4-1> [Preparation of positive and negative electrodes] The positive and negative electrode active materials prepared in Example 1 were used.

[0288] [Preparation of non-aqueous electrolyte] The electrolyte used was standard electrolyte 2. The electrolyte was prepared by adding compounds to the total amount of standard electrolyte 2 in the proportions shown in Table 6 below. However, Comparative Example 4-1 was standard electrolyte 2 itself.

[0289] <Evaluation of non-aqueous electrolyte secondary batteries> [Battery swelling] The thickness of the battery was measured after initial conditioning under the same conditions as in Example 2, and then a high-temperature cycle test (200 cycles) was performed in the same manner as in Example 2. The change in battery thickness was then measured in the same manner as after initial conditioning, and the change in electrode thickness of the battery with cycling was recorded as "battery swelling." The values ​​in Table 6 are the "battery swelling" values ​​for each battery having a negative electrode active material with a specified Si content in Examples 4-1 to 4-14, relative to the "battery swelling" of Comparative Example 4-1, which is set to 100, after the high-temperature cycle test (200 cycles) of the nonaqueous electrolyte secondary battery using reference electrolyte 2 itself in Comparative Example 4-1. In Table 6, the "%" for the compound (additive) indicates the mass % of the compound (additive) in 100 mass % of the nonaqueous electrolyte.

[0290] [Table 6]

[0291] As shown in Table 6, the "battery swelling" of the nonaqueous electrolyte secondary battery (Comparative Example 4-1) in which no specific compound was added to the nonaqueous electrolyte after the high-temperature cycle test (200 cycles) was 100, while the "battery swelling" of the nonaqueous electrolyte secondary batteries of Examples 4-1 to 4-14 was all less than 100, indicating improved cycle characteristics.

[0292] <Examples 5-1 to 5-5 and Comparative Examples 5-1 to 5-5> [Preparation of positive electrode] 97% by mass of lithium cobalt oxide (LiCoO2) as the positive electrode active material, 1.5% by mass of acetylene black as the conductive material, and 1.5% by mass of polyvinylidene fluoride (PVdF) as the binder were mixed in N-methylpyrrolidone solvent using a disperser to form a slurry, which was then uniformly applied to both sides of a 21 μm thick aluminum foil, dried, and pressed to form a positive electrode.

[0293] [Preparation of negative electrode] 97.5 parts by mass of negative electrode active material (graphite:SiO = 95:5; mass ratio), 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose: 1% by mass) and 1.5 parts by mass of an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) were added as thickener and binder, respectively, and mixed in a disperser to form a slurry. This slurry was uniformly applied to one side of a 10 μm thick copper foil, dried, and then pressed to form a negative electrode.

[0294] [Preparation of non-aqueous electrolyte] The electrolyte used was standard electrolyte 1. The electrolytes were prepared by adding compounds to the total amount of standard electrolyte 1 in the proportions shown in Table 7 below. However, Comparative Example 5-1 was standard electrolyte 1 itself.

[0295] [Manufacturing non-aqueous electrolyte batteries (laminated type)] The positive electrode, negative electrode, and polyolefin separator were stacked in this order: negative electrode, separator, positive electrode, separator, negative electrode. The battery element thus obtained was wrapped in an aluminum laminate film, and after injecting an electrolyte solution described below, the resulting structure was vacuum-sealed to prepare a sheet-shaped nonaqueous electrolyte secondary battery.

[0296] <Evaluation of non-aqueous electrolyte secondary batteries> [High temperature cycle test] In a 25°C thermostatic chamber, the laminated cell nonaqueous electrolyte secondary battery was charged at a constant current equivalent to 0.05 C for 10 hours, then discharged at 0.2 C to 2.75 V. CC-CV charging was performed at 0.2 C to 4.1 V and discharged at 0.2 C to 2.75 V to stabilize the nonaqueous electrolyte secondary battery. CC-CV charging was then performed at 0.2 C to 4.2 V, followed by discharge at 0.2 C to 2.75 V for initial conditioning. The battery thickness was then measured, and a high-temperature cycle test (200 cycles) was performed in a 45°C thermostatic chamber, with one cycle consisting of CCCV charging at 0.5 C to 4.2 V and then discharged at a constant current of 0.5 C to 2.5 V.

[0297] The capacity retention rate at the 200th cycle was calculated as follows. Capacity retention rate at 200 cycles = 200th cycle capacity / 1st cycle capacity x 100 Furthermore, the capacity retention rate at the 200th cycle of the nonaqueous electrolyte secondary battery using reference electrolyte 1 of Comparative Example 5-1 was set to 100, and the capacity retention rate at the 200th cycle of each battery having a negative electrode active material with a predetermined Si content in Examples 5-1 to 5-5 was calculated relative to this. These values ​​are shown in Table 7. In the table, the "%" of the compound (additive) represents the mass % of the compound (additive) in 100 mass % of the nonaqueous electrolyte.

[0298] [Battery swelling] As in the case after the initial conditioning, the change in battery thickness after 200 cycles was measured, and the change in electrode thickness of the battery due to the cycles was recorded as "battery swelling." The numerical values ​​in Table 7 are set to 100 for the "battery swelling" after the high-temperature cycle test (200 cycles) of the nonaqueous electrolyte secondary battery using reference electrolyte 1 of Comparative Example 5-1, and the "battery swelling" values ​​of each battery having a negative electrode active material with a predetermined Si content in Examples 5-1 to 5-5 are shown relative to this.

[0299] [Table 7]

[0300] As shown in Table 6, while the capacity retention rate after the high-temperature cycle test of the nonaqueous electrolyte secondary battery (Comparative Example 5-1) in which no specific compound was added to the nonaqueous electrolyte was 100, the capacity retention rates of the nonaqueous electrolyte secondary batteries of Examples 5-1 to 5-5 all exceeded 100. While the battery swelling after the high-temperature cycle test of the battery of Comparative Example 5-1 was 100, the battery swelling of the nonaqueous electrolyte secondary batteries of Examples 5-1 to 5-5 was all below 100, demonstrating a significant improvement effect. The nonaqueous electrolyte secondary batteries containing only the additives specified in the present invention (Comparative Examples 5-2 to 5-5) were all inferior to the batteries of Examples 5-1 to 5-5 in terms of capacity retention rate, and the battery swelling was not improved as well, with Comparative Example 5-2 showing a worsening of the problem. [Industrial Applicability]

[0301] The nonaqueous electrolyte solution of the present invention can improve the capacity degradation and cycle characteristics of nonaqueous electrolyte batteries during high-temperature storage. Therefore, the nonaqueous electrolyte solution can be suitably used in all fields, such as electronic devices, in which nonaqueous electrolyte secondary batteries are used. The nonaqueous electrolyte solution can also be suitably used in electrolytic capacitors, such as lithium ion capacitors, that use nonaqueous electrolyte solutions. The applications of the nonaqueous electrolyte and nonaqueous electrolyte secondary battery of the present invention are not particularly limited, and they can be used in a variety of known applications, including laptop computers, electronic book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, mobile audio players, small video cameras, LCD televisions, handheld vacuum cleaners, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, automobiles, motorcycles, mopeds, bicycles, lighting equipment, toys, game devices, watches, power tools, strobes, and cameras.

Claims

1. A non-aqueous electrolyte battery comprising a positive electrode and a negative electrode capable of absorbing and releasing metal ions, and a non-aqueous electrolyte solution, the non-aqueous electrolyte solution containing lithium bis(fluorosulfonyl)imide together with an electrolyte and a non-aqueous solvent, The non-aqueous electrolyte battery is characterized in that the negative electrode has a negative electrode active material containing Si or Si metal oxide and graphite particles.

2. 2. The nonaqueous electrolyte battery according to claim 1, wherein the negative electrode active material containing Si or Si metal oxide and graphite particles is a composite of Si or Si metal oxide and graphite particles.

3. 3. The nonaqueous electrolyte battery according to claim 1, wherein the content of said Si or Si metal oxide is 0.1 to 25 mass % based on the total of said Si or Si metal oxide and graphite particles.

4. 4. The nonaqueous electrolyte battery according to claim 1, wherein the content of the Si or Si metal oxide is 0.1 to 10 mass% with respect to the total of the Si or Si metal oxide and the graphite particles.

5. 5. The non-aqueous electrolyte battery according to claim 1, wherein the content of the lithium bis(fluorosulfonyl)imide is 0.01% by mass or more and 10.0% by mass or less with respect to the total amount of the non-aqueous electrolyte.

6. 6. The nonaqueous electrolyte battery according to claim 1, wherein the nonaqueous electrolyte contains at least one compound selected from the group consisting of a cyclic carbonate having a carbon-carbon unsaturated bond, a cyclic carbonate having a fluorine atom, an acid anhydride compound, a cyclic sulfonic acid ester compound, and a compound having a cyano group.

7. 7. The nonaqueous electrolyte battery according to claim 6, wherein the content of the at least one compound selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond, cyclic carbonates having a fluorine atom, acid anhydride compounds, cyclic sulfonate ester compounds, and compounds having a cyano group is 0.001% by mass or more and 10% by weight or less, based on the total amount of the nonaqueous electrolyte.

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