Nonaqueous electrolyte and energy device using same

Abstract

To provide a nonaqueous electrolyte solution which can achieve a high capacity and enhance the discharge characteristic (rate characteristic) under a high-current density condition in an energy device, and an energy device arranged by use of the nonaqueous electrolyte solution.SOLUTION: A nonaqueous electrolyte solution comprises: at least one compound (A) selected from a group consisting of a fluoro sulfonate anion-containing compound and an alkyl sulfate anion-containing compound; and at least one compound (B) selected from a group consisting of a linear ether compound (B-1) and a nitrile compound (B-2). In the nonaqueous electrolyte solution, a total content of the compound (B) is 1.0×10-5 mass% or more and below 1.0×10-1 mass%. The mass proportion [(A) / (B)] of a content of the compound (A) to the content of the compound (B) is no less than 98.000 / 2.000 and no more than 99.995 / 0.005.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Energy devices typified by nonaqueous electrolyte batteries such as lithium ion secondary batteries are being put to practical use in a wide range of applications, from so-called consumer power sources for mobile phones, laptop computers, etc. to on-board power sources for driving automobiles, etc. However, in recent years, there has been an increasing demand for higher performance for nonaqueous electrolyte batteries, and in particular, there has been a demand for improvements in various battery characteristics such as higher capacity, low-temperature usage characteristics, high-temperature storage characteristics, cycle characteristics, and safety during overcharge. To date, numerous technologies have been investigated for various battery components, including the active materials of the positive and negative electrodes and the nonaqueous electrolyte, as means for improving the high-temperature storage characteristics and cycle characteristics of nonaqueous electrolyte secondary batteries.

[0003] Patent Document 1 discloses a nonaqueous electrolyte solution containing LiPF6 and a fluorosulfonate, in which the molar content of FSO3 relative to the molar content of PF6 is 0.001 to 1.2, as a nonaqueous electrolyte solution that provides a secondary battery with improved initial charge capacity, input / output characteristics, and impedance characteristics. Patent Document 2 discloses a lithium battery with improved storage characteristics, which is provided with an electrolyte solution to which a nitrogen-containing compound such as alkylnitrile is added. Patent Document 3 discloses a nonaqueous electrolyte secondary battery having a high capacity and good charge / discharge cycle characteristics, which includes a negative electrode mainly composed of an amorphous chalcogen compound and / or an amorphous oxide, and a nonaqueous electrolyte containing a compound having an intramolecular ether bond. Patent Document 4 discloses a nonaqueous electrolyte solution containing 0.01 to 100 ppm of a diether compound such as 1,2-dimethoxypropane as a nonaqueous electrolyte solution that provides a nonaqueous electrolyte battery with excellent high-temperature continuous charging characteristics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-187440 [Patent Document 2] Japanese Patent Application Publication No. 10-189008 [Patent Document 3] Japanese Patent Application Publication No. 9-223517 [Patent Document 4] International Publication No. 2013 / 141165 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have found that the nonaqueous electrolyte solution described in Patent Document 1 has a problem in that a reduction side reaction also proceeds on the negative electrode, and LiF is by-produced on the negative electrode, inhibiting charge / discharge characteristics at high current densities, and the improving effect of fluorosulfonate is insufficient. Furthermore, the nonaqueous electrolyte solutions described in Patent Documents 2 to 4 also undergo an oxidation side reaction on the positive electrode, causing oxygen or metal ions to be extracted from the positive electrode, thereby deteriorating the positive electrode and causing a decrease in battery capacity, resulting in an insufficient improvement in battery characteristics.

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a nonaqueous electrolyte solution that can increase the capacity of an energy device and simultaneously improve the discharge characteristics (rate characteristics) under high current density, and an energy device that uses the nonaqueous electrolyte solution. [Means for solving the problem]

[0007] In view of the above circumstances, the present inventors have conducted extensive research and found that the above problems can be solved by using a nonaqueous electrolyte solution containing specific amounts of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds, and at least one compound (B) selected from the group consisting of specific chain ether compounds and specific nitrile compounds, and in which the mass ratio of compound (A) to compound (B) is adjusted to fall within a specific range, thereby completing the present invention. That is, the gist of the present invention is as follows.

[0008] [1] A composition comprising at least one compound (A) selected from the group consisting of a fluorosulfonate anion-containing compound and an alkylsulfate anion-containing compound, and at least one compound (B) selected from the group consisting of a chain ether compound (B-1) represented by the following formula (1) and a nitrile compound (B-2) represented by the following formula (2), The total content of the compound (B) in the non-aqueous electrolyte is 1.0 × 10 -5 Mass% or more 1.0×10 -1 is less than % by mass, a mass ratio [(A) / (B)] of the content of the compound (A) to the content of the compound (B) is 98.000 / 2.000 or more and 99.995 / 0.005 or less. R 1 O-(R 2 O) n -R 3 (1) [In formula (1), R 1 and R 3 each independently represents a hydrocarbon group having 1 to 4 carbon atoms, and R 2 represents a divalent hydrocarbon group having 1 to 3 carbon atoms, and n is an integer of 0 to 3. However, when n is 2 or more, multiple R 2 may be the same or different. R 4 -CN (2) [In formula (2), R 4 represents a hydrocarbon group having 1 to 4 carbon atoms. [2] The nonaqueous electrolyte solution according to [1], wherein the compound (A) is a fluorosulfonate and / or an alkyl sulfate. [3] The nonaqueous electrolyte solution according to [1] or [2], wherein the compound (A) is a fluorosulfonate. [4] The nonaqueous electrolyte solution according to any one of [1] to [3], wherein the compound (B) is a chain ether compound (B-1) represented by the formula (1). [5] R in the formula (1) 1 and R 3 are each independently a methyl group or an ethyl group, and R 2 The nonaqueous electrolyte solution according to any one of [1] to [4], wherein is an ethylene group, and n is an integer of 1 or more and 3 or less. [6] R in the formula (2) 4 The nonaqueous electrolyte solution according to any one of [1] to [5], wherein is a methyl group or an ethyl group. [7] The nonaqueous electrolyte solution according to any one of [1] to [6], further comprising at least one compound selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and fluorine-containing cyclic carbonates. [8] An energy device comprising: a positive electrode having a positive electrode active material capable of absorbing and desorbing lithium ions; a negative electrode having a negative electrode active material capable of absorbing and desorbing lithium ions; and the nonaqueous electrolyte solution according to any one of [1] to [7]. [9] The energy device according to [8], wherein the positive electrode contains, as a positive electrode active material, a lithium transition metal composite oxide represented by the following formula (13): Li a1 Ni b1 M c1 O2(13) [In formula (13), a1, b1, and c1 are 0.90≦a1≦1.10, 0.30≦b1≦0.98, and 0≦c1≦0.50, respectively, and b1+c1=1. M represents at least one element selected from the group consisting of Co, Mn, Al, Mg, Zr, Fe, Ti, and Er.]

[10] The energy device according to [9], wherein b1 in the formula (13) satisfies 0.55≦b1≦0.98. [Effects of the Invention]

[0009] The present invention provides a nonaqueous electrolyte solution for realizing an energy device that can have a high capacity and also has improved discharge characteristics (rate characteristics) under high current density, thereby achieving miniaturization, high performance, and improved safety of the energy device. DETAILED DESCRIPTION OF THE INVENTION

[0010] [1. Non-aqueous electrolyte] The nonaqueous electrolytic solution of the present invention contains at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds (including fluorosulfonates) and alkylsulfate anion-containing compounds (including alkyl sulfates), and at least one compound (B) selected from the group consisting of chain ether compounds (B-1) represented by formula (1) above and nitrile compounds (B-2) represented by formula (2) above, The total content of the compound (B) in the non-aqueous electrolyte is 1.0 × 10 -5 Mass% or more 1.0×10 -1 is less than % by mass, The mass ratio of the content of the compound (A) to the content of the compound (B) [(A) / (B)] is 98.000 / 2.000 or more and 99.995 / 0.005 or less. The nonaqueous electrolyte solution of the present invention may further contain, as an auxiliary agent, at least one compound selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and fluorine-containing cyclic carbonates. Here, the energy device refers to an electricity storage device or a power generation device, and examples thereof include lithium ion secondary batteries, lithium ion capacitors, electric double layer capacitors, solar cells, etc. Among these, the application to lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors is preferred, and the application to lithium ion secondary batteries is more preferred.

[0011] An energy device fabricated using the nonaqueous electrolyte solution of the present invention can achieve high capacity and simultaneously improve discharge characteristics (rate characteristics) under high current density. The action and principle thereof are not necessarily clear, but are presumed to be as follows. However, the present invention is not limited to the action and principle described below. Generally, when at least one compound selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds described in Patent Document 1 is used, the F of at least one compound selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds is obtained. ― The ions are released and the counter cations of nearby electrolytes or fluorosulfonate and alkylsulfate anions (e.g., Li + ions), fluoride salts and / or sulfates are by-produced and deposited on the negative electrode. However, fluoride salts and / or sulfates have strong ionic and intermolecular bonding forces, so they do not easily interact with cations (e.g., Li + The conductivity of Li ions is extremely low, especially during charging and discharging at high current densities. + Therefore, when fluoride salts and / or sulfates are generated on the negative electrode, they spread from that point to the entire negative electrode surface, reducing the effective specific surface area of ​​the negative electrode. As a result, there is a problem that the deintercalation and intercalation of cations from the negative electrode surface to the inside of the negative electrode during charging and discharging at high current densities is hindered. This problem is particularly noticeable when the electronegativity of the countercation is low, especially when the cation is Li + This is likely to occur when: Furthermore, the alkylnitriles described in Patent Document 2 and the ether compounds described in Patent Documents 3 and 4 have unshared electron pairs that are easily oxidized, and therefore have the problem of causing an oxidative decomposition reaction and deteriorating the positive electrode.

[0012] The present inventors have focused on these points and succeeded in suppressing the above-mentioned problems from a chemical viewpoint by incorporating specific amounts and specific ratios of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds, and at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2). Specifically, the chain ether compound (B-1) and the nitrile compound (B-2) have unshared electron pairs, which can act on fluoride salts and / or sulfate salts (e.g., LiF, Li2SO4) by-produced on the negative electrode when at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds is used, thereby alleviating the ionic and intermolecular bonding forces of the fluoride salts and / or sulfate salts. As a result, the degree of freedom of the cations is increased, improving the cation conductivity. Furthermore, by controlling the content of the chain ether compound (B-1) and the nitrile compound (B-2) and the content ratio relative to at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds within a specific range, side reactions on the positive electrode can be minimized. As a result, it is believed that high capacity can be achieved and discharge characteristics (rate characteristics) at high current densities can also be improved.

[0013] [1-1. At least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds, and at least one compound (B) selected from the group consisting of a chain ether compound (B-1) represented by formula (1), and a nitrile compound (B-2) represented by formula (2)] The method for incorporating at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds, the chain ether compound (B-1), and the nitrile compound (B-2) (hereinafter, these may also be referred to as "co-additives") into the nonaqueous electrolytic solution of the present invention is not particularly limited. In addition to the method of directly adding the compound to the non-aqueous electrolyte solution, there is also a method of generating the co-additive in an energy device or in a non-aqueous electrolyte solution, etc. Examples of the method of generating the co-additive include a method of adding a compound other than the co-additive and oxidizing or hydrolyzing an energy device component such as an electrolyte solution, and a method of producing an energy device and applying an electrical load such as charging and discharging to generate the co-additive.

[0014] When a co-additive is contained in a non-aqueous electrolyte solution and actually used to fabricate an energy device, even if the energy device is disassembled and the non-aqueous electrolyte solution is extracted again, the content of the co-additive therein is often significantly reduced. Therefore, even if a very small amount of the co-additive can be detected in the non-aqueous electrolyte solution extracted from the energy device, it is considered to be included in the present invention. Furthermore, when a non-aqueous electrolyte solution containing a co-additive is actually used to fabricate an energy device, even if the non-aqueous electrolyte solution extracted from the disassembled energy device contains only a very small amount of the co-additive, it is often detected on the positive electrode, negative electrode, and / or separator, which are other components of the energy device. Therefore, when a co-additive is detected on the positive electrode, negative electrode, and / or separator, it can be assumed that the total amount of the co-additive was contained in the non-aqueous electrolyte. It is preferable that each of the co-additives is contained within the range described below. In addition, if the counter cation of an anion in a non-aqueous electrolyte cannot be distinguished analytically, it is assumed that the counter cation is the same as the electrolyte. For example, in a non-aqueous electrolyte using LiPF6 as the electrolyte, if the counter cation of a detected anion cannot be distinguished, it is assumed that the counter cation is Li + considered as ions.

[0015] [1-1-1. At least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds] In the present invention, the at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds is preferably an anion having at least one fluorosulfonate or alkylsulfate structure in the molecule, and there are no other particular limitations. At least one compound selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds is usually contained in the non-aqueous electrolyte solution as an acid or a salt, but the present invention also includes at least one compound selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds that is generated in the system. The counter cation in the at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds is not particularly limited, and may be lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, or NR 131 R 132 R 133 R 134 (In the formula, R 131 ~R 134 are each independently a hydrogen atom or an organic group having 1 to 12 carbon atoms, and the like. At least one compound selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds preferably contains a salt, more preferably an alkali metal salt, and even more preferably a lithium salt. The above ammonium R 131 ~R 134 Examples of the organic group having 1 to 12 carbon atoms represented by the formula (I) include an alkyl group which may be substituted with a fluorine 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. 131 ~R 134are each independently preferably a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group, etc. As the counter cation, lithium, sodium, and potassium are preferred, and lithium is particularly more preferred.

[0016] The at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds includes lithium fluorosulfonate, sodium fluorosulfonate, potassium fluorosulfonate, rubidium fluorosulfonate, cesium fluorosulfonate, etc., and lithium fluorosulfonate is preferred. The alkyl group of the alkyl sulfate anion is not particularly limited, but is preferably a linear, branched, or cyclic alkyl group having from 1 to 20 carbon atoms. The number of carbon atoms in the alkyl group is more preferably from 1 to 12, more preferably from 1 to 8, and even more preferably from 1 to 4. The alkyl group may have a substituent, but is preferably unsubstituted. The at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds may be used singly or in combination of two or more in any ratio.

[0017] The content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds (the total amount when there are two or more compounds) in 100 mass% of the nonaqueous electrolyte solution is usually 1.0 × 10 -3 mass% or more, preferably 5.0 × 10 -2The content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds is generally 10% by mass or less, preferably 8% by mass or less, more preferably 7% by mass or less, even more preferably 6% by mass or less, even more preferably 5% by mass or less, even more preferably 4% by mass or less, even more preferably 3% by mass or less, even more preferably 2% by mass or less, and even more preferably 1% by mass or less. When the content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds is within this range, side reactions are less likely to occur in the energy device, and the resistance is less likely to increase.

[0018] When the non-aqueous electrolyte solution contains LiPF6, the mass ratio of the total content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds to the content of PF6 anions (at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds / PF6 anion) is usually 5.0 × 10 -5 or more, preferably 1.0 × 10 -4 More preferably, 1.0 × 10 -3 More preferably, 1.5 × 10 -3 The mass ratio is usually 0.5 or less, preferably 0.2 or less, more preferably 0.15 or less, even more preferably 0.1 or less, and even more preferably 0.05 or less. When the mass ratio is within this range, the energy device characteristics, particularly the rate characteristics, can be significantly improved. Although the mechanism behind this is unclear, it is thought that by mixing at this mass ratio, the decomposition side reaction of LiPF6 within the energy device system is minimized. The identification and content of at least one compound (A) selected from the group consisting of anion-containing compound salts and alkyl sulfate anion-containing compounds can be determined by nuclear magnetic resonance (NMR) analysis or ion chromatography (IC) analysis. NMR analysis is usually performed, but IC analysis is also performed when the solvent peak makes it difficult to identify other compounds.

[0019] [1-1-2. Chain ether compounds represented by formula (1) and nitrile compounds represented by formula (2)] The nonaqueous electrolyte solution of the present invention contains at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2). Among these, the chain ether compound (B-1) is preferred because it has multiple unshared electron pairs in one molecule and can form a stable chelate structure when acting on a fluoride salt and / or a sulfate salt, thereby further relaxing the ionic and intermolecular bonding forces of the fluoride salt and / or the sulfate salt and further improving the rate characteristics. The mass ratio [(A) / (B)] of the content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds to the content of compound (B) is, from the viewpoint of significantly exhibiting a synergistic effect of improving the problem of the present invention, 98,000 / 2,000 or more, preferably 99,000 / 1,000 or more, more preferably 99,500 / 0.500 or more, even more preferably 99,700 / 0.300 or more, even more preferably 99,800 / 0.200 or more, even more preferably 99,900 / 0.100 or more, and is 99.995 / 0.005 or less, preferably 99.990 / 0.010 or less, more preferably 99.980 / 0.020 or less. When the chain ether compound (B-1) and the nitrile compound (B-2) are used in combination, the content of the compound (B) is the total content of both compounds. The chain ether compound (B-1) and the nitrile compound (B-2) can be identified and their contents measured by nuclear magnetic resonance (NMR) analysis or gas chromatography (GC) analysis. NMR analysis is usually performed, but when the solvent peak makes it difficult to identify other compounds, GC analysis is also performed.

[0020] [1-1-2-1. Chain ether compound (B-1) represented by formula (1)] The chain ether compound (B-1) contained in the nonaqueous electrolyte solution of the present invention is represented by the following formula (1). R 1 O-(R 2 O) n -R 3 (1) [In formula (1), R 1 and R 3 each independently represents a hydrocarbon group having 1 to 4 carbon atoms, and R 2 represents a divalent hydrocarbon group having 1 to 3 carbon atoms, and n is an integer of 0 to 3. However, when n is 2 or more, multiple R 2 may be the same or different.

[0021] R in Equation (1) 1 and R 3 may have a substituent, and examples of the substituent of the hydrocarbon group include a halogen atom substitution (halogeno group), and preferably a fluorine atom substitution (fluoro group). The hydrocarbon group is preferably an unsubstituted saturated aliphatic hydrocarbon group having from 1 to 4 carbon atoms. Examples of the unsubstituted saturated aliphatic hydrocarbon group include linear, branched, and cyclic saturated aliphatic hydrocarbon groups, preferably linear or branched saturated aliphatic hydrocarbon groups, and more preferably linear saturated aliphatic hydrocarbon groups.

[0022] Also, R 1 and R 3 The number of carbon atoms in the main chain of the hydrocarbon group represented by R is 1 or more and 4 or less, preferably 3 or less, and more preferably 2. 1 and R 3 When the number of carbon atoms in the main chain is within this range, steric hindrance is reduced, and the compound (A) can act more efficiently on fluoride salts and / or sulfate salts, resulting in a more pronounced synergistic improvement effect with at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds.

[0023] R 1 and R 3Specific examples of the alkyl group include alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, and tert-butyl; alkenyl groups having 2 to 4 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-butenyl, 2-butenyl, and 3-butenyl; and alkynyl groups having 2 to 4 carbon atoms, such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, and 3-butynyl. Among these, from the viewpoint of efficiently acting on the fluoride salt and / or sulfate salt, alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, an i-butyl group, or a tert-butyl group are preferred, a methyl group, an ethyl group, an n-propyl group, or an n-butyl group is more preferred, a methyl group or an ethyl group is even more preferred, and a methyl group is particularly preferred.

[0024] R 1 and R 3 As the hydrocarbon group, a hydrocarbon group substituted with a fluorine atom can also be preferably used. From the viewpoint of the stability of the compound, preferred examples of the hydrocarbon group substituted with a fluorine atom include a fluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a perfluoroethyl group, a fluoro-n-propyl group, a difluoro-n-propyl group, a trifluoro-n-propyl group, a perfluoro-n-propyl group, a fluoro-n-butyl group, a difluoro-n-butyl group, a trifluoro-n-butyl group, and a perfluoro-n-butyl group. Furthermore, R 1 and R 3 are preferably the same group from the viewpoint of improving the symmetry of the molecule and allowing the ether oxygen site to act more efficiently on the fluoride salt and / or sulfate salt.

[0025] R 2is not particularly limited as long as it is a divalent hydrocarbon group having from 1 to 3 carbon atoms, and may have a substituent. Examples of the substituent on the hydrocarbon group include a halogen atom substitution (halogeno group), and preferably a fluorine atom substitution (fluoro group). Furthermore, the hydrocarbon group is preferably an unsubstituted saturated aliphatic hydrocarbon group having from 1 to 3 carbon atoms. Examples of the unsubstituted saturated aliphatic hydrocarbon group include linear and branched saturated aliphatic hydrocarbon groups, and preferably a linear saturated aliphatic hydrocarbon group.

[0026] Also, R 2 The number of carbon atoms in the main chain of the divalent hydrocarbon group is 1 or more and 3 or less, preferably 2 or less, and more preferably 2. 2 When the number of carbon atoms in the main chain is within this range, steric hindrance is reduced, and the multiple ether oxygens can act efficiently on fluoride salts and / or sulfate salts, resulting in a more pronounced synergistic improvement effect with at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds.

[0027] R 2 Specific examples of include a methylene group, an ethylene group, a trimethylene group, an ethylidene group, an isopropylidene group, a propylene group, a vinylidene group, a vinylene group, and a propenylene group, etc. Among these, from the viewpoint of optimizing the distance between ether oxygen atoms and efficiently acting on a fluoride salt and / or a sulfate salt, a methylene group, an ethylene group, a trimethylene group, an ethylidene group, an isopropylidene group, and a propylene group are preferred, a methylene group, an ethylene group, and a trimethylene group are more preferred, a methylene group and an ethylene group are even more preferred, and an ethylene group is particularly preferred.

[0028] In formula (1), n ​​is an integer of 0 or more, preferably 1 or more, and an integer of 3 or less, preferably 2 or less, more preferably 1. When n is within this range, compatibility with the electrolyte is ensured, and the compound can act more stably on the fluoride salt and / or sulfate salt, thereby exhibiting an improving effect, which is preferable. Note that when n is 2 or more, the compound can be easily used with a plurality of R 2may be the same or different, and are preferably the same. From the above viewpoints, the chain ether compound (B-1) is a compound represented by the formula (1) below: 1 and R 3 are each independently a methyl group or an ethyl group, and R 2 is an ethylene group, and n is an integer of 1 or more and 3 or less.

[0029] Specific examples of the chain ether compound (B-1) represented by the formula (1) include the following.

[0030] [When n = 0 in formula (1)] CH3OCH3, CH3CH2OCH3, CH3CH2OCH2CH3, CH3(CH2)2OCH3, CH3(CH2)2OCH2CH3, CH3(CH2)2O(CH2)2CH3, (CH3)2CHOCH3, (CH3)2CHOCH2CH3, (CH3)2 CHO(CH2)2CH3, (CH3)2CHOCH(CH3)2, CH3(CH2)3O(CH2)3CH3, CH3CH2CH(CH3)OCH(CH3)CH2CH3, (CH3)2CHCH2OCH2CH(CH3)2 and (CH3)3COC(CH3)3.

[0031] [When n=1 in formula (1)] R such as CH3OCH2OCH3, CH3CH2OCH2OCH2CH3 and CH3CH2OCH2OCH3 2 is a methylene group (CH2 group); R such as CH3OCH(CH3)OCH3, CH3CH2OCH(CH3)OCH2CH3 and CH3CH2OCH(CH3)OCH3 2 is an ethylidene group (CH(CH3) group); R of CH3OCH(CH3CH2)OCH3, CH3CH2OCH(CH3CH2)OCH2CH3 and CH3CH2OCH(CH3CH2)OCH3, etc. 2 is a propylidene group (CH(CH3CH2) group); R such as CH3OCH(CH3)2OCH3, CH3CH2OCH(CH3)2OCH2CH3 and CH3CH2OCH(CH3)2OCH3 2 is an isopropylidene group (CH(CH3)2 group); R such as CH3OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH3 and CH3CH2OCH2CH2OCH3 2 is an ethylene group (CH2CH2 group); R such as CH3OCH2CH2CH2OCH3, CH3CH2OCH2CH2CH2OCH2CH3 and CH3CH2OCH2CH2CH2OCH3 2 is a trimethylene group (CH2CH2CH2 group); R of CH3OCH(CH3)CH2OCH3, CH3CH2OCH(CH3)CH2OCH2CH3 and CH3CH2OCH(CH3)CH2OCH3, CH3OCH(CH3)CH2OCH2CH3, etc. 2 is a propylene group (CH(CH3)CH2 group); R such as CH3OC(CH2)OCH3, CH3CH2OC(CH2)OCH2CH3 and CH3CH2OC(CH2)OCH3 2 is a vinylidene group (C(CH2) group); R of CH3OCHCHOCH3, CH3CH2OCHCHOCH2CH3 and CH3CH2OCHCHOCH3 etc. 2 is a vinylene group (CHCH group); R of CH3OC(CH3)CHOCH3, CH3CH2OC(CH3)CHOCH2CH3 and CH3CH2OC(CH3)CHOCH3, CH3OC(CH3)CHOCH2CH3, etc. 2 is a propenylene group (C(CH3)CH group).

[0032] [When n=2 in formula (1)] R such as CH3OCH2OCH2OCH3, CH3CH2OCH2OCH2OCH2CH3 and CH3CH2OCH2OCH2OCH3 2 is a methylene group (CH2 group); R of CH3OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH2CH3 and CH3CH2OCH2CH2OCH2CH2OCH3, etc. 2 is an ethylene group (CH2CH2 group); R of CH3OCH2CH2CH2OCH2CH2CH2OCH3, CH3CH2OCH2CH2CH2OCH2CH2CH2OCH2CH3 and CH3CH2OCH2CH2CH2OCH2CH2CH2OCH3, etc. 2 is a trimethylene group (CH2CH2CH2 group).

[0033] [When n = 3 in formula (1)] R of CH3OCH2OCH2OCH2OCH3, CH3CH2OCH2OCH2OCH2OCH2CH3 and CH3CH2OCH2OCH2OCH2OCH3, etc. 2 is a methylene group (CH2 group); R of CH3OCH2CH2OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH2CH2OCH2CH3 and CH3CH2OCH2CH2OCH2CH2OCH2CH2OCH3 2 is an ethylene group (CH2CH2 group); R of CH3OCH2CH2CH2OCH2CH2CH2OCH2CH2CH2OCH3, CH3CH2OCH2CH2CH2OCH2CH2CH2OCH2CH2CH2OCH2CH3 and CH3CH2OCH2CH2CH2OCH2CH2CH2OCH2CH2CH2OCH3, etc. 2 is a trimethylene group (CH2CH2CH2 group).

[0034] Among these, from the viewpoint of suppressing side reactions in the electrolyte and allowing it to act efficiently to significantly exhibit the resistance reducing effect, one or more selected from CH3OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH3, CH3CH2OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH2CH2OCH2CH2OCH3 and CH3CH2OCH2CH2OCH2CH2OCH2CH2OCH2CH2OCH3 are preferred, More preferred are one or more selected from 2CH2OCH2CH3, CH3CH2OCH2CH2OCH3, CH3OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH2OCH2CH3 and CH3CH2OCH2CH2OCH2CH2OCH2CH3, even more preferred are one or more selected from CH3OCH2CH2OCH3, CH3CH2OCH2CH2OCH2CH3, CH3OCH2CH2OCH2CH2OCH3 and CH3CH2OCH2CH2OCH2CH2OCH2CH3, and even more preferred are one or more selected from 1,2-dimethoxyethane (CH3OCH2CH2OCH3) and diethylene glycol dimethyl ether (CH3OCH2CH2OCH2CH2OCH3).

[0035] The content of the chain ether compound (B-1) in the total amount (100% by mass) of the non-aqueous electrolyte solution is 1.0 × 10 -5 % by mass or more, preferably 2.5 × 10 -5 mass% or more, more preferably 5.0 × 10 -5 % by mass or more, and more preferably 1.0 × 10 -4 mass% or more, and 1.0 × 10 -1 mass%, preferably less than 1.0 × 10 -2 mass% or less, more preferably 5.0 × 10 -3 mass% or less, more preferably 2.0 × 10 -3mass% or less, more preferably 1.0 × 10 -3 mass% or less, more preferably 5.0 × 10 -4 It is less than % by mass.

[0036] [1-1-2-2. Nitrile compound (B-2) represented by formula (2)] The nitrile compound (B-2) contained in the nonaqueous electrolyte solution of the present invention is represented by the following formula (2). R 4 -CN (2) [In formula (2), R 4 represents a hydrocarbon group having 1 to 4 carbon atoms.

[0037] R 4 is not particularly limited as long as it is a hydrocarbon group having from 1 to 4 carbon atoms, and may have a substituent. Examples of the substituent on the hydrocarbon group include a halogen atom substitution (halogeno group), and preferably a fluorine atom substitution (fluoro group). The hydrocarbon group is preferably an unsubstituted saturated aliphatic hydrocarbon group having from 1 to 4 carbon atoms. Examples of the unsubstituted saturated aliphatic hydrocarbon group include linear, branched, and cyclic aliphatic hydrocarbon groups, preferably linear or branched aliphatic hydrocarbon groups, and more preferably linear aliphatic hydrocarbon groups. Also, R 4 The number of carbon atoms in the main chain of the hydrocarbon group is 1 or more and 4 or less, preferably 3 or less, more preferably 2 or less, and even more preferably 1, from the viewpoints of reducing steric hindrance, accelerating the action on fluoride salts and / or sulfate salts, and more significantly exhibiting a synergistic improving effect with at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds.

[0038] R 4Specific examples of the alkyl group include alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, and tert-butyl; alkenyl groups having 2 to 4 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-butenyl, 2-butenyl, and 3-butenyl; and alkynyl groups having 2 to 4 carbon atoms, such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, and 3-butynyl. Among these, from the viewpoint of efficiently acting on fluoride salts and / or sulfate salts, R 4 is preferably an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, an i-butyl group, or a tert-butyl group, more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, still more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0039] R 4 As the alkyl group, a hydrocarbon group substituted with a fluorine atom is also preferred. From the viewpoint of compound stability, preferred examples of the hydrocarbon group substituted with a fluorine atom include a fluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a perfluoroethyl group, a fluoro-n-propyl group, a difluoro-n-propyl group, a trifluoro-n-propyl group, a perfluoro-n-propyl group, a fluoro-n-butyl group, a difluoro-n-butyl group, a trifluoro-n-butyl group, and a perfluoro-n-butyl group.

[0040] Specific examples of the nitrile compound (B-2) represented by formula (2) include CH3CN, CH3CH2CN, CH3(CH2)2CN, CH3(CH2)3CN, CH2CHCN, CH3CHCHCN, CH2CHCH2CN, CH2C(CH3)CN, CHCCN, CH3CCCN, and CHCCH2CN. Among these, from the viewpoint of efficiently acting on the fluoride salt and / or sulfate salt and suppressing side reactions on the positive electrode, one or more selected from CH3CN, CH3CH2CN, CH3(CH2)2CN and CH3(CH2)3CN are preferred, one or more selected from acetonitrile (CH3CN) and propionitrile (CH3CH2CN) are more preferred, and acetonitrile (CH3CN) is particularly preferred.

[0041] The content of the nitrile compound (B-2) in the total amount (100 mass%) of the non-aqueous electrolyte solution is usually 1.0 × 10 -5 mass% or more, preferably 2.5 × 10 -5 mass% or more, more preferably 5.0 × 10 -5 mass% or more, more preferably 1.0 × 10 -4 % by mass or more, and is usually 1.0 × 10 -1 mass%, preferably less than 1.0 × 10 -2 mass% or less, more preferably 5.0 × 10 -3 mass% or less, more preferably 2.0 × 10 -3 mass% or less, more preferably 1.0 × 10 -3 mass% or less, more preferably 5.0 × 10 -4 It is less than % by mass.

[0042] From the above viewpoints, the total content of at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2) is 1.0 × 10 -5 % by mass or more, preferably 2.5 × 10 -5 mass% or more, more preferably 5.0 × 10 -5 mass% or more, more preferably 1.0 × 10 -4 mass% or more, and 1.0 × 10 -1 mass%, preferably less than 1.0 × 10 -2 mass% or less, more preferably 5.0 × 10 -3 mass% or less, more preferably 2.0 × 10 -3 mass% or less, more preferably 1.0 × 10-3 mass% or less, more preferably 5.0 × 10 -4 It is less than % by mass.

[0043] [1-2. Electrolytes] <Lithium salt> The electrolyte used in the non-aqueous electrolytic solution is usually a lithium salt, and there are no particular limitations on the lithium salt, so any lithium salt can be used. Specific examples thereof include lithium fluoroborates, lithium fluorophosphates, lithium tungstates, lithium carboxylates, lithium sulfonates, lithium imide salts, lithium methide salts, lithium oxalate salts, and fluorine-containing organic lithium salts.

[0044] Among these, from the viewpoint of improving low-temperature output characteristics, high-rate charge / discharge characteristics, impedance characteristics, high-temperature storage characteristics, cycle characteristics, etc., lithium fluoroborates such as LiBF4; lithium fluorophosphates such as LiPF6, Li2PO3F, and LiPO2F2; lithium sulfonates such as LiFSO3 and CH3SO3Li; lithium imide salts such as LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, and LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, and lithium cyclic 1,3-perfluoropropionate. Preferred examples of the lithium methide salts include LiC(FSO2)3, LiC(CF3SO2)3, and LiC(C2F5SO2)3; and preferred examples of the lithium oxalate salts include lithium difluorooxalatoborate, lithium bis(oxalato)borate, lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, and lithium tris(oxalato)phosphate, with one or more selected from LiPF6, LiN(FSO2)2, lithium bis(oxalato)borate, and LiFSO3 being more preferred, and LiPF6 being particularly preferred.

[0045] The above electrolyte salts can be used alone or in combination of two or more kinds in any ratio. The combination of two or more electrolyte salts is not particularly limited, and examples include a combination of LiPF6 and LiN(FSO2)2, a combination of LiPF6 and LiBF4, a combination of LiPF6 and LiN(CF3SO2)2, a combination of LiBF4 and LiN(FSO2)2, a combination of LiBF4, LiPF6 and LiN(FSO2)2, etc. Among these, the combination of LiPF6 and LiN(FSO2)2, the combination of LiPF6 and LiBF4, and the combination of LiBF4, LiPF6 and LiN(FSO2)2 are preferred.

[0046] The total concentration of the electrolyte is not particularly limited, but from the viewpoint of ensuring that the electrical conductivity ensures proper battery operation and sufficient output characteristics, it is usually 8 mass% or more, preferably 8.5 mass% or more, and more preferably 9 mass% or more, relative to the total amount of the nonaqueous electrolyte solution, and is usually 18 mass% or less, preferably 17 mass% or less, and more preferably 16 mass% or less.

[0047] [1-3. Non-aqueous solvents] The non-aqueous electrolyte solution, like a general non-aqueous electrolyte solution, usually contains a non-aqueous solvent that dissolves the above-mentioned electrolyte as its main component. The non-aqueous solvent used is not particularly limited as long as it can dissolve the above-mentioned electrolyte, and a known organic solvent can be used. Examples of the organic solvent include, but are not limited to, saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, cyclic carboxylic acid esters, cyclic ether compounds, and sulfone compounds.

[0048] The organic solvents may be used singly or in combination of two or more kinds in any ratio. The combination of two or more organic solvents is not particularly limited, and examples thereof include a combination of a saturated cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carboxylic acid ester and a chain carbonate, and a combination of a saturated cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, etc. Among these, a combination of a saturated cyclic carbonate and a chain carbonate, and a combination of a saturated cyclic carbonate, a chain carbonate and a chain carboxylic acid ester are preferred.

[0049] [1-3-1. Saturated cyclic carbonates] Examples of saturated cyclic carbonates include those having an alkylene group having 2 to 4 carbon atoms, and saturated cyclic carbonates having 2 to 3 carbon atoms are preferred from the viewpoint of improving battery characteristics resulting from an improved degree of lithium ion dissociation. Specific examples of saturated cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, etc. Among these, ethylene carbonate or propylene carbonate is preferred, and ethylene carbonate, which is less susceptible to oxidation and reduction, is more preferred. The saturated cyclic carbonates can be used alone or in combination of two or more in any ratio.

[0050] The content of the saturated cyclic carbonate is not particularly limited and may be any content as long as it does not impair the effects of the present invention. The content of the saturated cyclic carbonate is usually 3% by volume or more, preferably 5% by volume or more, based on the total amount of the nonaqueous solvent, and is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting the content within this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte solution can be avoided, and the large-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the nonaqueous electrolyte secondary battery tend to be in good ranges, and the oxidation / reduction resistance of the nonaqueous electrolyte solution and stability during high-temperature storage tend to be improved. In this specification, "volume %" refers to volume % at 25°C and 1 atmosphere.

[0051] [1-3-2. Chain carbonate] As the chain carbonate, for example, one having 3 to 7 carbon atoms is usually used, and in order to adjust the viscosity of the electrolyte solution within an appropriate range, a chain carbonate having 3 to 5 carbon atoms is preferably used. 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, etc., and preferably one or more selected from dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Furthermore, chain carbonates having fluorine atoms (hereinafter also referred to as "fluorinated chain carbonates") can also be suitably used. 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, preferably 4 or less. When the fluorinated chain carbonate has multiple fluorine atoms, the multiple fluorine atoms may be bonded to the same carbon or different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives such as fluoromethyl methyl carbonate; fluorinated ethyl methyl carbonate derivatives such as 2-fluoroethyl methyl carbonate; and fluorinated diethyl carbonate derivatives such as ethyl-(2-fluoroethyl) carbonate. The chain carbonates can be used alone or in combination of two or more kinds in any ratio.

[0052] The content of the chain carbonate is not particularly limited, but from the viewpoint of keeping the viscosity of the nonaqueous electrolyte solution within an appropriate range, suppressing a decrease in ionic conductivity, and ultimately improving the output characteristics of the nonaqueous electrolyte secondary battery, the content is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more, relative to the total amount of the nonaqueous solvent in the nonaqueous electrolyte solution, and is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. Furthermore, by combining a specific chain carbonate with ethylene carbonate in a specific content, the battery performance can be significantly improved. For example, when dimethyl carbonate and ethyl methyl carbonate are selected as the specific chain carbonates, the content of ethylene carbonate is arbitrary as long as it does not impair the effects of the present invention, but from the viewpoint of improving high-temperature stability and suppressing gas generation, the content of ethylene carbonate is usually 15% by volume or more, preferably 20% by volume or more, and usually 45% by volume or less, preferably 40% by volume or less, based on the total amount of solvent in the non-aqueous electrolyte solution. The content of dimethyl carbonate is usually 20% by volume or more, preferably 30% by volume or more, and usually 50% by volume or less, preferably 45% by volume or less, based on the total amount of non-aqueous solvent in the non-aqueous electrolyte solution. The content of ethyl methyl carbonate is usually 20% by volume or more, preferably 30% by volume or more, and usually 50% by volume or less, preferably 45% by volume or less, based on the total amount of non-aqueous solvent in the non-aqueous electrolyte solution.

[0053] [1-3-3. Chain carboxylic acid esters] Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl valerate, methyl isobutyrate, ethyl isobutyrate, and methyl pivalate. Among these, methyl acetate, ethyl acetate, propyl acetate, and butyl acetate are preferred from the viewpoint of improving battery characteristics. Chain carboxylic acid esters in which some of the hydrogen atoms of the above compounds are substituted with fluorine atoms (e.g., methyl trifluoroacetate, ethyl trifluoroacetate, etc.) can also be suitably used. The amount of the chain carboxylic acid ester is usually 1% by volume or more, preferably 5% by volume or more, and more preferably 15% by volume or more, based on the total amount of the nonaqueous solvent, from the viewpoints of improving the electrical conductivity of the nonaqueous electrolyte and enhancing the large-current discharge characteristics of the nonaqueous electrolyte battery. The upper limit of the amount is usually 70% by volume or less, preferably 50% by volume or less, and more preferably 40% by volume or less, from the viewpoints of maintaining an appropriate viscosity of the nonaqueous electrolyte, avoiding a decrease in electrical conductivity, suppressing an increase in negative electrode resistance, and ensuring good large-current discharge characteristics of the nonaqueous electrolyte secondary battery.

[0054] [1-3-4. Cyclic carboxylic acid esters] Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone. Among these, γ-butyrolactone is more preferred. Cyclic carboxylic acid esters in which some of the hydrogen atoms of the above compounds are substituted with fluorine atoms can also be used suitably. The amount of the cyclic carboxylic acid ester is usually 1% by volume or more, preferably 5% by volume or more, and more preferably 15% by volume or more, based on the total amount of the nonaqueous solvent, from the viewpoints of improving the electrical conductivity of the nonaqueous electrolyte and enhancing the large-current discharge characteristics of the nonaqueous electrolyte battery. The upper limit of the amount is usually 70% by volume or less, preferably 50% by volume or less, and more preferably 40% by volume or less, from the viewpoints of maintaining an appropriate viscosity of the nonaqueous electrolyte, avoiding a decrease in electrical conductivity, suppressing an increase in negative electrode resistance, and ensuring good large-current discharge characteristics of the nonaqueous electrolyte secondary battery.

[0055] [1-3-5. Cyclic ether compounds] Examples of the cyclic ether compound include cyclic ethers having 3 to 6 carbon atoms, such as tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane. Some of the hydrogen atoms in the cyclic ether compound may be substituted with fluorine atoms. Among these, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, and the like are preferred from the viewpoint of providing high ionic conductivity.

[0056] The content of the cyclic ether compound is arbitrary as long as it does not impair the effects of the present invention, but is usually 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and usually 30% by volume or less, preferably 25% by volume or less, more preferably 20% by volume or less, based on the total amount of nonaqueous solvent in the nonaqueous electrolyte. When the content of the cyclic ether compound is within the above range, it is easy to ensure the effect of improving the degree of lithium ion dissociation by the cyclic ether compound and improving ionic conductivity due to the reduced viscosity of the nonaqueous electrolyte. Furthermore, when the negative electrode active material is a carbon-based material, the phenomenon of chain ethers being co-inserted with lithium ions can be suppressed, thereby allowing the input / output characteristics and charge / discharge rate characteristics to be within appropriate ranges.

[0057] [1-3-6. Sulfone compounds] The sulfone compound is not particularly limited and may be a cyclic sulfone or a chain sulfone. In the case of a cyclic sulfone, the carbon number is usually 3 to 6, preferably 3 to 5, and in the case of a chain sulfone, the carbon number is usually 2 to 6, preferably 2 to 5. In addition, the number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, but is usually 1 or 2. Examples of cyclic sulfones include monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones, and disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones. Among these, from the viewpoints of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferred, and tetramethylene sulfones (sulfolanes) are even more preferred. Preferred sulfolanes are sulfolane and sulfolane derivatives, and preferred sulfolane derivatives are those in which one or more hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with a fluorine atom, an alkyl group, or a fluorine-substituted alkyl group. Among these, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,3-difluorosulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, and the like are preferred because they have high ionic conductivity and high input / output.

[0058] Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, pentafluoroethyl methyl sulfone, etc. Among these, dimethyl sulfone, ethyl methyl sulfone, and monofluoromethyl methyl sulfone are preferred in terms of improving the high-temperature storage stability of the electrolyte solution. The content of the sulfone-based compound is arbitrary as long as it does not impair the effects of the present invention. From the viewpoint of improving high-temperature storage stability, the content is usually 0.3 vol% or more, preferably 0.5 vol% or more, more preferably 1 vol% or more, relative to the total amount of the nonaqueous solvent in the nonaqueous electrolyte solution, and is usually 40 vol% or less, preferably 35 vol% or less, more preferably 30 vol% or less.

[0059] [1-4. Auxiliaries] The non-aqueous electrolyte solution of the present invention may contain various auxiliary agents within the range that does not impair the effects of the present invention. As the auxiliary agent, any conventionally known agent can be used. The auxiliary agent can be used alone or in combination of two or more in any ratio. Examples of the auxiliary include cyclic carbonates having a carbon-carbon unsaturated bond, fluorine-containing cyclic carbonates, compounds having an isocyanate group, compounds having an isocyanuric acid skeleton, sulfur-containing organic compounds, phosphorus-containing organic compounds, silicon-containing compounds, aromatic compounds, organic compounds having a cyano group other than the nitrile compound represented by the formula (2), fluorine-free carboxylic acid esters, cyclic ether compounds, carboxylic acid anhydrides, borates, oxalates, monofluorophosphates, difluorophosphates, etc. Examples include compounds described in WO 2015 / 111676. The cyclic ether compound can be used as an auxiliary agent in the non-aqueous electrolyte solution, and some of them can also be used as a non-aqueous solvent as described in [1-3. Non-aqueous solvent]. When a cyclic ether compound is used as an auxiliary agent, it is preferably used in an amount of less than 4% by mass. Borates, oxalates, monofluorophosphates, and difluorophosphates can be used as auxiliary agents in nonaqueous electrolyte solutions, and as described in [1-2. Electrolyte], some of these compounds can also be used as electrolytes. When these compounds are used as auxiliary agents, it is preferably used in an amount of less than 3% by mass. Among these, cyclic carbonates having a carbon-carbon unsaturated bond and fluorine-containing cyclic carbonates are preferred from the viewpoint of easily forming a stable interface protective coating.

[0060] [1-4-1. Cyclic carbonates having carbon-carbon unsaturated bonds, fluorine-containing cyclic carbonates] In the non-aqueous electrolyte solution, at least one compound selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and fluorine-containing cyclic carbonates is preferred, and it is more preferred to use them in combination, as long as the effects of the present invention are exhibited. These can be used alone or in combination of two or more in any ratio.

[0061] [1-4-1-1. Cyclic carbonates having carbon-carbon unsaturated bonds] The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter also referred to as "unsaturated cyclic carbonate") is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond. Cyclic carbonates having an aromatic ring are also included in the unsaturated cyclic carbonate.

[0062] Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond, or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, catechol carbonates, etc. Among these, vinylene carbonates and ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond, or a carbon-carbon triple bond are preferred.

[0063] Specific examples of the unsaturated cyclic carbonate include vinylene carbonates such as vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, and 4,5-diallyl vinylene carbonate; Ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond, such as 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; and the like. Among these, vinylene carbonate, vinylethylene carbonate, and ethynylethylene carbonate are preferred because they form a more stable interface protective coating, and one or more selected from vinylene carbonate and vinylethylene carbonate are more preferred, with vinylene carbonate being even more preferred. The unsaturated cyclic carbonates can be used alone or in combination of two or more kinds in any ratio.

[0064] The content of the unsaturated cyclic carbonate (total amount when two or more types are used) in 100 mass% of the nonaqueous electrolyte solution is preferably 1.0 × 10 -3 The content of the unsaturated cyclic carbonate is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. When the content of the unsaturated cyclic carbonate is within this range, energy devices such as non-aqueous electrolyte batteries are likely to exhibit a sufficient effect of improving the cycle characteristics, and it is also 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.

[0065] The mass ratio of the content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds to the content of the unsaturated cyclic carbonate (total amount when two or more types are used) (at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds / unsaturated cyclic carbonate) is usually 1 / 100 or more, preferably 10 / 100 or more, more preferably 20 / 100 or more, and even more preferably 25 / 100 or more, and is usually 10,000 / 100 or less, preferably 500 / 100 or less, and more preferably 300 / 100 or less. A mass ratio within this range is believed to significantly improve energy device properties, particularly rate performance, and minimize side reactions of the additive on the electrode.

[0066] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total content of unsaturated cyclic carbonate to the content of PF6 anion (unsaturated cyclic carbonate / PF6 anion) is usually 5.0 × 10 -5 or more, preferably 1.0 × 10 -3The mass ratio is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.025 or more, and is usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, even more preferably 0.35 or less. If the mass ratio is within this range, it is believed that the energy device characteristics, particularly the rate characteristics, can be significantly improved, and the decomposition side reaction of LiPF6 in the energy device system can be minimized.

[0067] [1-4-1-2. Fluorine-containing cyclic carbonates] The fluorine-containing cyclic carbonate is not particularly limited as long as it has a cyclic carbonate structure and contains a fluorine atom. Examples of fluorine-containing cyclic carbonates include fluorinated cyclic carbonates having an alkylene group with 2 to 6 carbon atoms, and derivatives thereof, such as fluorinated ethylene carbonate (hereinafter also referred to as "fluorinated ethylene carbonate") and derivatives thereof. Examples of derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (for example, an alkyl group with 1 to 4 carbon atoms). Among these, fluorinated ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.

[0068] Examples of fluorinated ethylene carbonates having 1 to 8 fluorine atoms and derivatives thereof 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. Among these, from the viewpoint of imparting high ionic conductivity to the electrolyte and facilitating the formation of a stable interface protective coating, one or more selected from monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate are preferred. The fluorine-containing cyclic carbonates can be used alone or in combination of two or more kinds in any ratio.

[0069] The content of the fluorine-containing cyclic carbonate (total amount when two or more types are used) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, relative to 100% by mass of the nonaqueous electrolyte solution, and is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less. When the fluorine-containing cyclic carbonate is used as the non-aqueous solvent, the content thereof is preferably 1% by volume or more, more preferably 5% by volume or more, and even more preferably 10% by volume or more, and is preferably 50% by volume or less, more preferably 35% by volume or less, and even more preferably 25% by volume or less, based on 100% by volume of the non-aqueous solvent.

[0070] The mass ratio of the content of the at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds to the content of the fluorine-containing cyclic carbonate (the total amount when two or more types are used) (at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds / fluorine-containing cyclic carbonate) is usually 1 / 100 or more, preferably 10 / 100 or more, more preferably 20 / 100 or more, and even more preferably 25 / 100 or more, from the viewpoints of improving energy device characteristics, particularly rate characteristics, and minimizing side reactions of the additive on the electrode, and is usually 10,000 / 100 or less, preferably 500 / 100 or less, and more preferably 300 / 100 or less.

[0071] When the non-aqueous electrolyte solution contains LiPF6, the mass ratio of the total content of fluorine-containing cyclic carbonate to the content of PF6 anion (fluorine-containing cyclic carbonate / PF6 anion) is usually 0.00005 or more, preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.02 or more, and even more preferably 0.025 or more, from the viewpoint of improving the energy device characteristics, particularly the rate characteristics, and minimizing the decomposition side reaction of LiPF6 within the energy device system, and is also usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, and even more preferably 0.35 or less.

[0072] [2. Energy Devices] The energy device of the present invention is characterized by comprising a positive electrode having a positive electrode active material capable of absorbing and desorbing lithium ions, a negative electrode having a negative electrode active material capable of absorbing and desorbing lithium ions, and the nonaqueous electrolyte solution of the present invention. The energy device of the present invention is preferably a nonaqueous electrolyte battery, a polyvalent cation battery, a metal-air secondary battery, a secondary battery using an s-block metal other than those mentioned above, a lithium ion capacitor, or an electric double layer capacitor, more preferably a nonaqueous electrolyte battery or a lithium ion capacitor, and even more preferably a lithium secondary battery. The non-aqueous electrolyte solution used in these energy devices may be a so-called gel electrolyte, which is a pseudo-solidified solution made with a polymer, a filler, or the like.

[0073] [2-1. Non-aqueous electrolyte battery] The nonaqueous electrolyte battery according to one embodiment of the present invention is a nonaqueous electrolyte battery including a positive electrode having a positive electrode active material capable of absorbing and desorbing lithium ions and a negative electrode having a negative electrode active material capable of absorbing and desorbing lithium ions, and is preferably a lithium battery including the nonaqueous electrolyte solution of the present invention. Note that, within the scope of the present invention, it is also possible to mix the nonaqueous electrolyte solution of the present invention with other nonaqueous electrolyte solutions.

[0074] [2-1-1. Lithium battery] The lithium battery according to the present invention comprises a positive electrode having a current collector and a positive electrode active material layer provided on the current collector, a negative electrode having a current collector and a negative electrode active material layer provided on the current collector and capable of absorbing and releasing lithium ions, and the nonaqueous electrolyte solution according to the present invention. In the present invention, the term "lithium battery" is a general term for lithium ion primary batteries and lithium ion secondary batteries. The lithium battery according to the present invention is similar to conventionally known lithium batteries in terms of its configuration except for the non-aqueous electrolyte solution of the present invention. Typically, a positive electrode and a negative electrode are stacked via a porous membrane (separator) impregnated with a non-aqueous electrolyte solution, and these are housed in a case (exterior body). The lithium battery will be described below.

[0075] [2-2. Positive electrode] The positive electrode has a positive electrode active material capable of absorbing and desorbing lithium ions on at least a portion of the surface of a current collector. The positive electrode active material preferably contains a lithium transition metal compound. [2-2-1. Positive electrode active material]

[0076] [2-2-1-1. Lithium transition metal compounds] The lithium transition metal compound is a compound having a structure capable of desorbing and inserting lithium ions, and examples thereof include sulfides, phosphate compounds, silicate compounds, borate compounds, lithium transition metal composite oxides, etc. Among these, lithium transition metal composite oxides are preferred. Examples of lithium transition metal composite oxides include those having a spinel structure that allows three-dimensional diffusion and those having a layered structure that allows two-dimensional diffusion of lithium ions.

[0077] A lithium transition metal composite oxide having a spinel structure is generally represented by the following formula (11). Li x M2O4(11) [In formula (11), x is 1≦x≦1.5, and M represents one or more transition metal elements.] Specific examples of the oxide represented by formula (11) include LiMn2O4, LiCoMnO4, and LiNi 0.5 Mn 1.5 O4, LiCoVO4, etc.

[0078] A lithium transition metal composite oxide having a layered structure is generally represented by the following composition formula (12). Li 1+x MO2(12) (In formula (12), x is −0.1≦x≦0.5, and M represents one or more transition metal elements.) Specific examples of oxides represented by formula (12) include LiCoO2, LiNiO2, and LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.33 Co0.33 Mn 0.33 O2, Li 1.05 Ni 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.91 Co 0.06 Mn 0.03 O2, LiNi 0.91 Co 0.06 Al 0.03 O2, LiNi 0.90 Co 0.03 Al 0.07 Examples include O2.

[0079] Among these, from the viewpoint of improving battery capacity, lithium transition metal composite oxides having a layered structure are preferred, and lithium transition metal composite oxides represented by the following formula (13) are more preferred. Li a1 Ni b1 M c1 O2(13) [In formula (13), a1, b1, and c1 are 0.90≦a1≦1.10, 0.30≦b1≦0.98, and 0≦c1≦0.50, respectively, and b1+c1=1. M represents at least one element selected from the group consisting of Co, Mn, Al, Mg, Zr, Fe, Ti, and Er.] In formula (13), b1 is preferably 0.50 or more, and more preferably 0.60 or more.

[0080] In particular, from the viewpoint of the structural stability of the lithium transition metal composite oxide, a lithium transition metal composite oxide represented by the following formula (14) is preferred. Li a2 Ni b2 Co c2 Md2 O2(14) [In formula (14), a2, b2, c2, and d2 are 0.90≦a2≦1.10, 0.30≦b2≦0.98, 0.01≦c2≦0.05, and 0.01≦d2≦0.50, respectively, and b2+c2+d2=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.] In the above formula (14), b2 is preferably 0.50 or more, more preferably 0.60 or more, and d2 is preferably 0.01 or more, more preferably 0.10 or more. A suitable example of the lithium transition metal composite oxide represented by the above formula (14) is LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.91 Co 0.06 Mn 0.03 O2, LiNi 0.91 Co 0.06 Al 0.03 O2, LiNi 0.90 Co 0.03 Al 0.07 Examples include O2. In the above formulas (11) to (13), from the viewpoint of increasing the structural stability of the lithium transition metal composite oxide and suppressing structural deterioration during repeated charge and discharge, M preferably contains Mn or Al, and more preferably contains Mn. In the above formula (14), M preferably contains Mn or Al, from the viewpoint of increasing the structural stability of the lithium transition metal composite oxide and suppressing structural deterioration during repeated charge and discharge.

[0081] [2-2-1-2. Introduction of different elements] The lithium transition metal composite oxide may also contain elements (foreign elements) other than the elements contained in any of the above formulas (11) to (14).

[0082] [2-2-1-3. Surface coating] The positive electrode may be one in which a substance (surface-adhering substance) having a different composition from the positive electrode active material is attached to the surface of the positive electrode active material. Examples of the surface-attaching substance include oxides such as aluminum oxide, sulfates such as lithium sulfate, carbonates such as lithium carbonate, etc. These surface-attaching substances can be attached to the surface of the positive electrode active material by, for example, dissolving or suspending them in a solvent, adding them to the positive electrode active material by impregnation, and drying them. The amount of the surface-adhering substance is preferably 1 μmol / g or more, more preferably 10 μmol / g or more, and usually preferably 1 mmol / g or less, relative to the positive electrode active material. In this specification, a positive electrode active material having the above-mentioned surface-adhering substance attached to its surface is also referred to as a "positive electrode active material."

[0083] [2-2-1-4. Blend] The positive electrode active material may be used alone or in combination of two or more kinds in any ratio.

[0084] [2-2-2. Positive electrode structure and manufacturing method] The positive electrode using the positive electrode active material can be manufactured by a conventional method. That is, the positive electrode active material and a binder, and optionally a conductive material and a thickener, are mixed in a dry state to form a sheet, which is then pressed onto the positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium such as an aqueous solvent or an organic solvent to form a slurry, which is then applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector. A positive electrode can also be obtained by a coating method. For example, the above-mentioned positive electrode active material may be roll-molded into a sheet electrode, or may be compression-molded into a pellet electrode. Hereinafter, the case where the slurry is sequentially applied to the positive electrode current collector and then dried will be described.

[0085] [2-2-2-1. Content of positive electrode active material] The content of the positive electrode active material in the positive electrode active material layer is usually 80% by mass or more and 99.5% by mass or less.

[0086] [2-2-2-2. Electrode density] The positive electrode active material layer obtained by coating and drying is preferably compacted by a hand press, a roller press, or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer present on the current collector is usually 1.5 g / cm. 3 More than 4.5g / cm 3 The following is the result.

[0087] [2-2-2-3.Conductive materials] Any known conductive material can be used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon-based materials such as amorphous carbon such as needle coke. The conductive material can be used alone or in combination of two or more types in any ratio. The conductive material is typically used so that it is contained in the positive electrode active material layer in an amount of 0.01% by mass to 50% by mass.

[0088] [2-2-2-4. Binder] When forming the positive electrode active material layer by a coating method, the binder used in producing the positive electrode active material layer is not particularly limited as long as it is a material that can be dissolved or dispersed in a liquid medium for the slurry. For example, in view of weather resistance, chemical resistance, heat resistance, flame retardancy, etc., fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, etc.; CN group-containing polymers such as polyacrylonitrile, polyvinylidene cyanide, etc. are preferred. Also usable are mixtures, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, etc. The binder may be used alone or in combination of two or more kinds in any ratio. Furthermore, when a resin is used as a binder, the weight-average molecular weight of the resin is optional as long as it does not impair the effects of the present invention, and is usually from 10,000 to 3,000,000. When the molecular weight is in this range, the strength of the electrode is improved, and the electrode can be suitably formed. The proportion of the binder in the positive electrode active material layer is usually 0.1 mass % or more and 80 mass % or less.

[0089] [2-2-2-5. Current collector] The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, with aluminum being preferred. The current collector may be in the form of a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, a foamed metal, or the like. Among these, a metal foil or a metal thin film is preferred. The metal thin film may be suitably formed into a mesh shape. When the current collector of the positive electrode is in the form of a plate or film, the thickness of the current collector is optional, but is usually 1 μm or more and 1 mm or less.

[0090] [2-2-2-6. Thickness of the positive electrode plate] The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the positive electrode active material layer obtained by subtracting the thickness of the current collector from the thickness of the positive electrode plate is usually 10 μm or more and 500 μm or less on one side of the current collector.

[0091] [2-2-2-7. Surface coating of positive electrode plate] The positive electrode plate may have a substance of a different composition from the positive electrode plate attached to its surface, and the substance may be the same as the surface-attached substance that may be attached to the surface of the positive electrode active material.

[0092] [2-3. Negative electrode] The negative electrode has a negative electrode active material on at least a portion of the surface of a current collector. [2-3-1. Negative electrode active material] The negative electrode active material used in the negative electrode is not particularly limited as long as it can electrochemically absorb and release lithium ions. Specific examples include (i) carbon-based materials, (ii) particles containing a metal capable of alloying with Li, (iii) lithium-containing metal composite oxide materials, and (iv) mixtures thereof. Among these, the use of (i) carbon-based materials, (ii) particles containing a metal capable of alloying with Li, and (v) mixtures of particles containing a metal capable of alloying with Li and graphite particles is preferred, in terms of good cycle characteristics and safety, as well as excellent continuous charge characteristics. These may be used alone or in combination of two or more in any ratio.

[0093] [2-3-1-1. Carbon-based materials] (i) Examples of carbonaceous materials include natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. Of these, natural graphite is preferred. The carbonaceous materials can be used alone or in combination of two or more in any ratio. Examples of natural graphite include scaly graphite, flake graphite, and / or graphite particles obtained by subjecting such graphite to treatment such as spheroidization or densification. Among these, spherical or ellipsoidal graphite particles that have been subjected to spheroidization treatment are preferred from the viewpoint of particle packing properties or charge / discharge rate characteristics. The average particle size (d50) of the graphite particles is usually 1 μm or more and 100 μm or less.

[0094] [2-3-1-2. Physical properties of carbon-based materials] The carbonaceous material as the negative electrode active material preferably satisfies at least one of the characteristics such as physical properties and shape shown in the following items (1) to (4), and more preferably satisfies several items at the same time. (1) X-ray diffraction parameters The d value (interlayer distance) of the lattice plane (002 plane) of carbon-based materials determined by X-ray diffraction using the Gakushin method is usually 0.335 nm or more and 0.360 nm or less. Also, the crystallite size (Lc) of carbon-based materials determined by X-ray diffraction using the Gakushin method is 1.0 nm or more. (2) Volume-based average particle size The volume-based average particle size of the carbon-based material is the volume-based average particle size (median diameter) determined by a laser diffraction / scattering method, and is usually 1 μm or more and 100 μm or less. (3) Raman R value, Raman half-width The Raman R value of a carbon-based material is a value measured using argon ion laser Raman spectroscopy, and is usually 0.01 or more and 1.5 or less. In addition, the 1580 cm -1 The Raman half-width in the vicinity is not particularly limited, but is usually 10 cm -1 More than 100cm -1 The following is the result. (4) BET specific surface area The BET specific surface area of ​​a carbon-based 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 100m 2 ·g -1 The following is the result. The negative electrode active material may contain two or more carbonaceous materials with different properties, where the properties refer to one or more characteristics selected from the group consisting of X-ray diffraction parameters, volume-based average particle size, Raman R value, Raman half-width, and BET specific surface area. Examples of containing two or more carbon-based materials with different properties include a case where the volume-based particle size distribution is not symmetrical about the median diameter, a case where two or more carbon-based materials with different Raman R values ​​are contained, and a case where X-ray diffraction parameters are different.

[0095] [2-3-1-3. Particles containing metals that can be alloyed with Li] (ii) Although any conventionally known particles containing a metal capable of being alloyed with Li can be used, from the viewpoints of capacity and cycle life, particles of a metal selected from the group consisting of Sb, Si, Sn, Al, As, and Zn or a compound thereof are preferred. Furthermore, when the particles containing a metal capable of being alloyed with Li contain two or more types of metal, the particles may be alloy particles made of an alloy of these metals. In addition, examples of the compound of a metal capable of alloying with Li include metal oxides, metal nitrides, metal carbides, etc. The compound may contain two or more metals capable of alloying with Li. Among these, metal Si (hereinafter also referred to as "Si") or a Si-containing inorganic compound is preferable in terms of achieving a high capacity. In addition, the compound of a metal capable of alloying with Li may already be alloyed with Li during the production of the negative electrode described later. As the compound, Si or a Si-containing inorganic compound is preferable in terms of achieving a high capacity. In this specification, Si or a Si-containing inorganic compound is collectively referred to as a Si compound. Examples of the Si compound include SiO x (0 ≦ x ≦ 2), etc. Examples of the metal compound alloyed with Li include Li y Si(0 < y ≦ 4.4), Li 2z SiO 2+z (0 < z ≦ 2), etc. Examples of the Si compound include Si metal oxides (SiO x1 , 0 < x1 ≦ 2), which are preferable in terms of having a larger theoretical capacity compared to graphite, and amorphous Si or nano-sized Si crystals are preferable in terms of allowing easy entry and exit of alkali ions such as lithium ions and being able to obtain a high capacity. The average particle diameter (d 50 ) of the particles containing a metal capable of alloying with Li is usually 0.01 μm or more and 10 μm or less from the perspective of cycle life.

[0096] [2 - 3 - 1 - 4. Mixture of Particles Containing a Metal Capable of Alloying with Li and Graphite Particles] (v) The mixture of particles containing a metal capable of alloying with Li and graphite particles may be a mixture in which the particles containing a metal capable of alloying with Li in the above (ii) and the graphite particles are mixed in a state of independent particles, or a composite in which the particles containing a metal capable of alloying with Li are present on the surface or inside of the graphite particles. The content ratio of the particles containing a metal capable of alloying with Li to the total of the particles containing a metal capable of alloying with Li and graphite particles is usually 1 mass% or more and 99 mass% or less.

[0097] [2-3-1-5. Lithium-containing metal composite oxide materials] (iii) The lithium-containing metal composite oxide material is not particularly limited as long as it can absorb and release lithium ions. Specifically, from the viewpoint of high current density charge / discharge characteristics, a lithium-containing metal composite oxide material containing titanium is preferred, a composite oxide of lithium and titanium (hereinafter also referred to as "lithium-titanium composite oxide") is more preferred, and a lithium-titanium composite oxide having a spinel structure is even more preferred because it significantly reduces output resistance. Furthermore, the lithium and / or titanium of the lithium titanium composite oxide may be substituted with another metal element, for example, at least one element selected from the group consisting of Al, Ga, Cu, and Zn. As a lithium titanium composite oxide, Li 4 / 3 Ti 5 / 3 O4, Li1Ti2O4 and Li 4 / 5 Ti 11 / 5 O4 is preferred. In addition, examples of lithium titanium composite oxides in which part of lithium and / or titanium is substituted with other elements include Li 4 / 3 Ti 4 / 3 Al 1 / 3 O4 is also preferred.

[0098] [2-3-2. Negative electrode structure and manufacturing method] The negative electrode may be produced by any known method as long as it does not impair the effects of the present invention. For example, the negative electrode may be produced by adding a binder, a liquid medium such as an aqueous solvent or an organic solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, which is then applied to a current collector, dried, and pressed to form a negative electrode active material layer.

[0099] [2-3-2-1. Content of negative electrode active material] The content of the negative electrode active material in the negative electrode active material layer is usually 80% by mass or more and 99.5% by mass or less.

[0100] [2-3-2-2. Electrode density] The negative electrode active material layer obtained by coating and drying is preferably compacted by a hand press, a roller press or the like in order to increase the packing density of the negative electrode active material. 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 layer on the current collector is usually 1 g cm -3 More than 2.2g cm -3 The following is the result.

[0101] [2-3-2-3. Thickener] Thickeners are usually used to adjust the viscosity of the slurry. Examples of thickeners include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, etc. These may be used alone or in combination of two or more in any ratio. When a thickener is used, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more and 5% by mass or less.

[0102] [2-3-2-4. Binder] The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable in the non-aqueous electrolyte solution and the liquid medium used in producing the electrode. Specific examples thereof include rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber, as well as fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and tetrafluoroethylene-ethylene copolymers. These may be used alone or in combination of two or more in any ratio. The ratio of the binder to the negative electrode active material is usually 0.1 mass % or more and 20 mass % or less. In particular, when the binder contains a rubber-like polymer such as SBR as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass to 5% by mass, and when the binder contains a fluorine-based polymer such as polyvinylidene fluoride as a main component, the ratio of the binder to the negative electrode active material is usually 1% by mass to 15% by mass.

[0103] [2-3-2-5. Current collector] Any known current collector can be used to support the negative electrode active material. Examples of the negative electrode current collector include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferred from the standpoints of ease of processing and cost. The negative electrode current collector may be in the form of a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, a foamed metal, or the like. Among these, a metal foil or a metal thin film is preferred. The metal thin film may be suitably formed into a mesh shape. When the negative electrode current collector is in the form of a plate or film, the thickness of the current collector is not limited, but is usually 1 μm or more and 1 mm or less.

[0104] [2-3-2-6. Thickness of negative electrode plate] The thickness of the negative electrode (negative electrode plate) is designed to match the positive electrode (positive electrode plate) to be used and is not particularly limited, but the thickness of the negative electrode active material layer, obtained by subtracting the thickness of the current collector from the thickness of the negative electrode material, is usually 15 μm or more and 300 μm or less.

[0105] [2-3-2-7. Surface coating of negative electrode plate] The negative electrode plate may have a surface to which a substance (surface-attached substance) having a different composition from the negative electrode active material is attached. Examples of the surface-attached substance include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate.

[0106] [2-4. Separator] A separator is usually interposed between the positive electrode and the negative electrode to prevent short circuits, and in this case, the non-aqueous electrolyte is usually impregnated into the separator before use. There are no particular restrictions on the material or shape of the separator, and any known material can be used as long as it does not impair the effects of the present invention.

[0107] [2-5.Battery design] [2-5-1. 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 (electrode group occupancy rate) is usually 40% to 90%.

[0108] [2-5-2. Current collection structure] When the electrode group has the aforementioned laminated structure, a structure in which the metal core portions of each electrode layer are bundled and welded to a terminal is preferably used. A structure in which multiple terminals are provided within the electrode to reduce resistance is also preferably used. When the electrode group has the aforementioned wound structure, the internal resistance can be reduced by providing multiple lead structures on each of the positive electrode and negative electrode and bundling them to a terminal.

[0109] [2-5-3.Protection elements] The protective element may be a PTC (Positive Temperature Coefficient) element whose resistance increases with heat generation due to excessive current, 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.

[0110] [2-5-4. Exterior body] An energy device, such as a nonaqueous electrolyte battery, preferably a lithium battery, is usually constructed by housing the nonaqueous electrolyte of the present invention, a negative electrode, a positive electrode, a 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 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 nonaqueous electrolyte solution used, but from the viewpoints of weight reduction and cost, metals such as iron, aluminum, and aluminum alloys, or laminate films are preferably used. Iron is particularly preferred from the viewpoint of pressure resistance required to operate the current cutoff valve. Examples of exterior cases using the above metals include those in which metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed, airtight structure, and those in which the above metals are used via a resin gasket to form a crimped structure.

[0111] [2-5-5. Shape] 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]

[0112] EXAMPLES 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.

[0113] Example 1 [Preparation of non-aqueous electrolyte] In a dry argon atmosphere, 1.0 mol / L of LiPF was dissolved as an electrolyte in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio: 3:4:3). 1.0 mass % of vinylene carbonate and 1.0 mass % of monofluoroethylene carbonate were then dissolved as auxiliary agents to prepare a base electrolyte solution. Furthermore, to this basic electrolyte, 0.5 mass % of lithium fluorosulfonate (LiFSO3) and 1.0 × 10 1,2-dimethoxyethane were added as additives. -4 % by mass was added to prepare a non-aqueous electrolyte solution.

[0114] [Preparation of positive electrode] Lithium cobalt nickel manganese oxide (LiNi 0.6 Co 0.2 Mn 0.290% by mass of O2, 7% by mass of acetylene black as a conductive material, and 3% by mass of polyvinylidene fluoride as a binder were mixed in N-methylpyrrolidone solvent using a disperser to form a slurry, which was then uniformly applied to both sides of a 15 μm thick aluminum foil, dried, and pressed to form a positive electrode.

[0115] [Preparation of negative electrode] The negative electrode active material was natural graphite powder, the thickener was an aqueous dispersion of sodium carboxymethylcellulose (1% by mass of sodium carboxymethylcellulose), and the binder was an aqueous dispersion of styrene-butadiene rubber (50% by mass of styrene-butadiene rubber). These materials were mixed in a disperser to form a slurry. This slurry was evenly applied to one side of a 10 μm thick copper foil, dried, and then pressed to form the negative electrode. The mass ratio of natural graphite:sodium carboxymethylcellulose:styrene-butadiene rubber after drying was 98:1:1.

[0116] [Fabrication of lithium secondary batteries] The positive electrode, negative electrode, and polypropylene separator were stacked in this order to prepare a battery element. This battery element was inserted into a bag made of a laminate film of aluminum (40 μm thick) coated on both sides with a resin layer, with the positive and negative electrode terminals protruding. A nonaqueous electrolyte solution was then poured into the bag, which was then vacuum-sealed to prepare a sheet-shaped lithium secondary battery.

[0117] [Charge / discharge test] The lithium secondary battery was sandwiched between glass plates and pressurized, and then charged at a constant current of 0.2 C for 2.5 hours at 25°C, followed by constant current discharge at 0.2 C to 2.8 V. The battery was then subjected to constant current-constant voltage charging (also known as "CC-CV charging") at a current equivalent to 0.2 C (cut off at 0.05 C) to 4.1 V, followed by discharge at a constant current of 0.2 C to 2.8 V. The battery was then subjected to CC-CV charging at 0.2 C to 4.3 V (cut off at 0.05 C), followed by discharge at 0.2 C to 2.8 V, which was designated the 0.2 C capacity. Furthermore, after CC-CV charging at 0.2 C to 4.3 V (cut by 0.05 C), the battery was discharged at 1 C to 2.8 V, which was defined as the 1.0 C capacity. The ratio of the 1.0 C capacity to the 0.2 C capacity at this time was calculated and defined as the rate characteristic (%). Here, 1C represents the current value that discharges the standard capacity of the battery in 1 hour, and for example, 0.2C represents 1 / 5 of that current value.

[0118] The above-mentioned charge-discharge test was carried out using the lithium secondary battery prepared as described above. The evaluation results are shown in Table 1 as relative values ​​when the result of Comparative Example 1 described later is set to 100.0%. In Table 1, the "mass ratio" means "the content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds / the content of at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2)," and is expressed as a ratio when the total content of at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkyl sulfate anion-containing compounds, the chain ether compound (B-1), and the nitrile compound (B-2) is taken as 100. The same applies to the following Examples 2 to 7 and Comparative Examples 1 to 10.

[0119] <Examples 2 to 7 and Comparative Examples 1 to 10> A non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 1, except that the conditions in Example 1 were changed to those shown in Table 1, and the above evaluations were carried out.

[0120] [Table 1] EtSO4 - : Ethyl sulfate anion PO2F2 - :Difluorophosphate anion CF3SO3 - : Trifluoromethylsulfonate anion DO: 1,3-dioxane DME: 1,2-dimethoxyethane AN: Acetonitrile

[0121] Table 1 shows that when the nonaqueous electrolyte solutions of Examples 1 to 7 are used, the 0.2C capacity is superior and the discharge capacity ratio (rate characteristics) at high current densities is improved compared to a case (Comparative Example 1) in which at least one compound (A) selected from the group consisting of a fluorosulfonate anion-containing compound and an alkylsulfate anion-containing compound, and at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2) are not contained. When at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2) was used alone (Comparative Examples 4 and 5), the 0.2C capacity decreased and no improvement in rate characteristics was observed. Furthermore, when at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds was used alone (Comparative Examples 2 and 3), improvements in 0.2C capacity and rate characteristics were observed, but the improvements were small and inferior to those in Examples 1 to 7. When at least one compound (B) selected from the group consisting of the chain ether compound (B-1) and the nitrile compound (B-2) is contained but is outside the content and mass ratio ranges of the present invention (Comparative Examples 6 and 10), the rate characteristics are improved but the 0.2C capacity is reduced. Furthermore, even with the combinations used in the prior art (Comparative Examples 7 to 9), the rate characteristics are improved but the 0.2C capacity is reduced. Therefore, it is clear that the lithium secondary battery using the nonaqueous electrolyte solution of the present invention has superior characteristics.

[0122] It should be noted that, although the charge / discharge tests were conducted as a model in the Examples and Comparative Examples shown in Table 1, significant differences were confirmed. Since actual non-aqueous electrolyte secondary batteries may be used for several years, it can be understood that the differences in these results become even more significant when long-term use is assumed. [Industrial Applicability]

[0123] By using the nonaqueous electrolyte solution of the present invention as an electrolyte solution for an energy device, the capacity of the energy device can be increased and the discharge characteristics under high current density can be improved. Therefore, the nonaqueous electrolyte solution of the present invention can be suitably used in all fields, such as electronic devices, in which energy devices are used. The nonaqueous electrolyte solution of the present invention and the energy device using the same can be used in various known applications. Specific examples of applications include notebook computers, pen-input personal computers, mobile personal computers, electronic book players, mobile phones, mobile fax machines, mobile copiers, mobile printers, mobile audio players, small video cameras, headphone stereos, video movie cameras, LCD televisions, handheld vacuum cleaners, portable CDs, minidiscs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting equipment, toys, game machines, clocks, power tools, flash devices, cameras, home backup power supplies, business backup power supplies, load-leveling power supplies, and natural energy storage power supplies.

Claims

1. The composition contains at least one compound (A) selected from the group consisting of fluorosulfonate anion-containing compounds and alkylsulfate anion-containing compounds, and a chain ether compound (B-1) represented by the following formula (1): The total content of the compound (B-1) in the non-aqueous electrolyte solution is 1.0 × 10 －５ Mass% or more 1.0×10 －１ is less than % by mass, The mass ratio [(A) / (B-1)] of the content of the compound (A) to the content of the compound (B-1) is 98.000 / 2.000 or more and 99.995 / 0.005 or less. R １ O-(R ２ O) ｎ -R ３ (1) [In formula (1), R １ and R ３ each independently represents a hydrocarbon group having 1 to 4 carbon atoms; R ２ represents a divalent hydrocarbon group having 1 to 3 carbon atoms, and n is an integer of 1 to 3. However, when n is 2 or more, there are multiple R ２ may be the same or different.

2. The nonaqueous electrolyte solution according to claim 1 , wherein the compound (A) is a fluorosulfonate and / or an alkyl sulfate.

3. The nonaqueous electrolyte solution according to claim 1 or 2, wherein the compound (A) is a fluorosulfonate.

4. R in the formula (1) １ and R ３ are each independently a methyl group or an ethyl group, and R ２ The nonaqueous electrolyte solution according to any one of claims 1 to 3, wherein is an ethylene group and n is 1.

5. The nonaqueous electrolyte solution according to any one of claims 1 to 4, further comprising at least one compound selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and fluorine-containing cyclic carbonates.

6. An energy device comprising: a positive electrode having a positive electrode active material capable of absorbing and desorbing lithium ions; a negative electrode having a negative electrode active material capable of absorbing and desorbing lithium ions; and the nonaqueous electrolyte solution according to any one of claims 1 to 5.

7. 7. The energy device according to claim 6, wherein the positive electrode contains, as a positive electrode active material, a lithium transition metal composite oxide represented by the following formula (13): Li ａ１ Ni ｂ１ M ｃ１ O ２ (13) [In formula (13), a1, b1, and c1 are 0.90≦a1≦1.10, 0.30≦b1≦0.98, and 0≦c1≦0.50, respectively, and b1+c1=1. M represents at least one element selected from the group consisting of Co, Mn, Al, Mg, Zr, Fe, Ti, and Er.]

8. The energy device according to claim 7, wherein b1 in the formula (13) satisfies 0.55≦b1≦0.98.

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