Non-aqueous electrolytes and energy devices

Abstract

Provided are: a non-aqueous electrolyte solution that can suppress the room-temperature and / or low-temperature discharge resistance growth of an energy device; and an energy device that includes the non-aqueous electrolyte solution. A non-aqueous electrolyte solution for an energy device that comprises a positive electrode and a negative electrode. The non-aqueous electrolyte solution is characterized by containing an electrolyte, a non-aqueous solvent, a linear sulfonic acid ester, and at least one compound selected from the group that consists of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, the mass ratio of the amount of the linear sulfonic acid ester to the amount of the at least one compound selected from the group that consists of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates being within a specific range.

Description

[Technical Field]

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

[0002] Energy devices such as lithium primary batteries, lithium secondary batteries, electric double layer capacitors, and lithium ion capacitors have been put to practical use in a wide range of applications, such as power sources for so-called small consumer devices such as mobile phones such as smartphones and laptop computers, and on-board power sources for driving electric vehicles, etc. However, in recent years, there has been an increasing demand for higher performance for energy devices.

[0003] In particular, many studies have been conducted in the fields of positive and negative electrode active materials and additives for non-aqueous electrolytes as means for improving the battery characteristics of non-aqueous electrolyte batteries.

[0004] For example, Patent Document 1 discloses a technology in which, by using an electrolyte solution for a lithium secondary battery containing an alkyl alkanesulfonate having 1 to 6 carbon atoms, a coating film is formed on the surface of a carbon electrode through a reaction between the alkyl alkanesulfonate and the carbon electrode, thereby suppressing decomposition of the electrolyte solution and improving cycle characteristics. Patent Document 2 discloses a technology for providing a nonaqueous electrolyte secondary battery that uses a nonaqueous electrolyte containing LiPF6 and a fluorosulfonate, and that improves the initial charge capacity, input / output characteristics, and impedance characteristics by setting the molar content of FSO3 relative to the molar content of PF6 to 0.001 to 1.2, thereby maintaining not only initial battery characteristics and durability, but also high input / output characteristics and impedance characteristics even after endurance. Patent Document 3 discloses a technology for providing a nonaqueous electrolyte secondary battery that uses an electrolyte containing vinylene carbonate, difluorophosphate, and the like, thereby suppressing deterioration in the repeated charge-discharge characteristics of the battery and also exhibiting excellent low-temperature discharge characteristics. Patent Document 4 discloses a technology for providing a non-aqueous electrolyte secondary battery using an electrolyte containing a boron-containing compound and a cyclic sulfonate ester, in which the content of the boron-containing compound is set to 0.1 to 2.0 mass %, thereby providing a secondary battery with high charge / discharge efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-245834 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-187440 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-141830 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-243461 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the trend toward higher-capacity lithium batteries has accelerated for use as power sources for electric vehicles and mobile phones such as smartphones, and the proportion of voids within the battery has become smaller than before. This has led to an increased demand for suppression of the rate of increase in discharge resistance at room temperature and low temperatures, particularly during durability tests such as high-temperature storage tests. In view of the above, an object of the present invention is to provide a nonaqueous electrolyte solution that can suppress the room-temperature and / or low-temperature discharge resistance increase rate of an energy device, and to provide an energy device in which the room-temperature and / or low-temperature discharge resistance increase rate is suppressed. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have found that the room temperature and low temperature discharge resistance increase rate of an energy device can be suppressed by using a non-aqueous electrolyte solution containing a chain sulfonate ester and at least one compound selected from the group consisting of fluorosulfonate, monofluorophosphate, difluorophosphate, imide salt, and oxalate, and containing the chain sulfonate ester in a specific ratio relative to the compound, thereby completing the present invention. The present invention provides the following specific aspects, etc.

[0008] [1] A non-aqueous electrolyte for an energy device having a positive electrode and a negative electrode, The non-aqueous electrolytic solution, together with an electrolyte and a non-aqueous solvent, A non-aqueous electrolyte solution comprising a chain sulfonic acid ester and at least one fluorophosphate selected from monofluorophosphates and difluorophosphates, wherein the mass ratio of the chain sulfonic acid ester content to the fluorophosphate content is 10 / 90 or more and 82 / 18 or less. [2] A non-aqueous electrolyte for an energy device having a positive electrode and a negative electrode, The non-aqueous electrolytic solution, together with an electrolyte and a non-aqueous solvent, (A) contains a chain sulfonic acid ester and at least one compound selected from the group consisting of a fluorosulfonate, an imide salt, and an oxalate, (B) The total content of at least one compound selected from the group consisting of fluorosulfonates, imide salts, and oxalates is 1.0 × 10 in 100 mass% of the nonaqueous electrolyte solution. -3 % by mass or more and 7% by mass or less, and (C) A non-aqueous electrolyte solution characterized in that the mass ratio of the content of at least one compound selected from the group consisting of fluorosulfonates, imide salts, and oxalates to the content of a chain sulfonate ester is 10 / 90 or more and 99.99 / 0.01 or less. [3] The nonaqueous electrolyte solution according to [1] or [2], wherein the chain sulfonic acid ester is a compound represented by formula (1). [ka] (In formula (1), R 1 represents a hydrocarbon group having 1 to 5 carbon atoms which may have a substituent, and R 2 represents a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent. [4] The nonaqueous electrolyte solution according to any one of [1] to [3], 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. [5] An energy device comprising a positive electrode, a negative electrode, and the nonaqueous electrolyte solution according to any one of [1] to [4]. [6] The energy device according to [5], wherein the positive electrode contains a positive electrode active material, and the positive electrode active material is a lithium transition metal composite oxide represented by composition formula (14): Li a1 Ni b1 Co c1 M d1 O2···(14) (In formula (14), a1, b1, c1, and d1 represent numerical values ​​of 0.90≦a1≦1.10, 0.50≦b1≦0.98, 0.01≦c1<0.50, and 0.01≦d1<0.50, respectively, and satisfy b1+c1+d1=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.) [Effects of the Invention]

[0009] According to the present invention, a nonaqueous electrolyte solution capable of suppressing the room temperature and / or low temperature discharge resistance increase rate of an energy device can be provided. Furthermore, by using such a nonaqueous electrolyte solution, an energy device in which the room temperature and / or low temperature discharge resistance increase rate is suppressed can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail. The following embodiments are examples (typical examples) of the present invention, and the present invention is not limited to these. Furthermore, the present invention can be implemented with any modifications within the scope of the gist thereof.

[0011] <1.Non-aqueous electrolyte> As described below, a nonaqueous electrolyte solution according to one embodiment of the present invention contains a chain sulfonate ester and at least one compound selected from the group consisting of a fluorosulfonate salt, a monofluorophosphate salt, a difluorophosphate salt, an imide salt, and an oxalate salt, and contains the chain sulfonate ester in a specific ratio relative to the compound.

[0012] Previous attempts have been made to improve the characteristics of energy devices by using chain sulfonic acid esters. For example, Patent Document 1 mentions that alkyl alkanesulfonates form a coating on the surface of carbon electrodes and suppress decomposition of the electrolyte. However, the coating formed here is highly soluble in the electrolyte, and may dissolve and disappear during durability tests such as high-temperature storage tests. As a result, side reactions of the electrolyte on the negative electrode during durability tests cannot be suppressed, and there is room for improvement in the discharge resistance retention rate after durability tests. On the other hand, at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates partially dissociates in the electrolyte to generate anions, which then act on the positive electrode to provide protective effects. However, these compounds simultaneously undergo side reactions on the positive electrode and are consumed, failing to provide the desired effect after durability testing. Furthermore, because fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates have oxygen-mediated double bonds, molecular orbital theory suggests that their increased electron acceptance may cause reduction side reactions on the negative electrode, inhibiting the formation of a coating. As a result, there is room for improvement in the discharge resistance retention rate after durability testing.

[0013] In response to such problems, the present inventors have found that the above problems can be solved by incorporating a chain sulfonate ester into a non-aqueous electrolyte solution and mixing at least one compound selected from the group consisting of fluorosulfonate salts, monofluorophosphate salts, difluorophosphate salts, imide salts, and oxalate salts into the non-aqueous electrolyte solution in a specific ratio relative to the chain sulfonate ester. The chain sulfonate ester generates an anion radical upon reduction, which immediately undergoes an addition reaction with the oxygen-mediated double bond of at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates. The resulting complex has low solubility and can exist as a stable coating on the negative electrode, thereby enhancing the protective ability of the negative electrode. Furthermore, even if a small amount of the complex (composite coating) is eluted, the components strongly and stably act on the positive electrode, thereby enhancing the protective effect on the positive electrode. Therefore, the rate of increase in discharge resistance at room temperature and / or low temperature can be suppressed. Furthermore, if the amount of at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates is insufficient relative to the chain sulfonate ester, an unstable coating derived from the chain sulfonate ester is likely to be formed. Therefore, it is necessary to contain the chain sulfonic acid ester and at least one compound selected from the group consisting of fluorosulfonate, monofluorophosphate, difluorophosphate, imide salt, and oxalate in a specific ratio. In addition, cyclic sulfonate esters are more easily reduced than chain sulfonate esters, and therefore tend to undergo unstable film-forming reactions by themselves. Furthermore, because the cyclic structure has low steric flexibility, it is less likely to undergo an addition reaction with at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates than highly flexible chain sulfonate esters. Therefore, composite film formation is also less likely to occur, resulting in insufficient effects.

[0014] There are no particular limitations on the method for incorporating an additive such as a chain sulfonate ester (hereinafter, chain sulfonate esters, fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates will also be referred to as "additives" or "co-additives") into a non-aqueous electrolyte solution according to one embodiment of the present invention. In addition to a method of directly adding the following compounds to the electrolyte solution, a method of generating the co-additive in an energy device or in the electrolyte solution can be used. Examples of methods for 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 the electrolyte solution. Another example is a method of generating the co-additive by fabricating an energy device and applying an electrical load such as charging and discharging.

[0015] Furthermore, when a co-additive is incorporated into 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 a non-aqueous electrolyte solution extracted from an energy device, it is considered to be included in the present invention. Furthermore, when a non-aqueous electrolyte solution is actually used to fabricate an energy device, even if the non-aqueous electrolyte solution extracted after disassembling the energy device contains only a very small amount of the co-additive, the co-additive is often detected on the positive electrode, negative electrode, or separator, which are other components of the energy device. Therefore, if the co-additive is detected on the positive electrode, negative electrode, or separator, it can be assumed that the combined amount was contained in the non-aqueous electrolyte. Under this assumption, it is preferable that the co-additive be contained within the range described below.

[0016] <1-1. Chain sulfonic acid esters>

[0017] The chain sulfonate ester in this embodiment is not particularly limited as long as it has at least one sulfonate ester structure in the molecule. The chain sulfonic acid ester is preferably a compound represented by the following formula (1). [ka] (In formula (1), R 1 represents a hydrocarbon group having 1 to 5 carbon atoms which may have a substituent, and R 2 represents a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent.

[0018] R in formula (1) 1 and R 2 may be the same group or different groups, but if they are different groups, the coating-forming reaction proceeds efficiently and a synergistic effect is more likely to be exhibited when the chain sulfonate ester is added in combination with one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, which will be described later.

[0019] R 1 is not particularly limited as long as it is a hydrocarbon group having from 1 to 5 carbon atoms, and may have a substituent. Examples of the substituent on the hydrocarbon group include halogen atom substitution (halogeno group), and preferably fluorine substitution (fluoro group). Furthermore, it is particularly preferred that the hydrocarbon group is an unsubstituted aliphatic saturated hydrocarbon group having from 1 to 5 carbon atoms. Examples of the unsubstituted aliphatic saturated hydrocarbon group include linear, branched, or cyclic aliphatic hydrocarbon groups, and preferably linear or branched aliphatic hydrocarbon groups, and more preferably linear aliphatic hydrocarbon groups.

[0020] Also, R 1 The number of carbon atoms in the main chain of the hydrocarbon group represented by R is usually 1 or more, and usually 5 or less, preferably 3 or less, and more preferably 2 or less. 1 When the number of carbon atoms in the main chain of the hydrocarbon group represented by the formula (I) is within this range, steric hindrance is reduced, making it easier for the action on the electrode to occur, and therefore a synergistic improving effect with one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, which will be described later, is more significantly exhibited.

[0021] R 1 Specific examples of the alkyl group include alkyl groups having 1 to 5 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, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 1,1-dimethylpropyl group, and a 1,2-dimethylpropyl group; a vinyl group, a 1-propenyl group, a 2-propenyl group, an isopentyl group, and the like. Examples thereof include alkenyl groups having 2 to 5 carbon atoms, such as propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, and 4-pentenyl groups; and alkynyl groups having 2 to 5 carbon atoms, such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl groups. Preferred are alkyl groups having 1 to 5 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1-methylbutyl, 2-methylbutyl, 1,1-dimethylpropyl, and 1,2-dimethylpropyl, more preferably methyl, ethyl, n-propyl, n-butyl, or n-pentyl, further preferably methyl or ethyl, and particularly preferably methyl, because this allows a protective coating to be efficiently formed on the negative electrode.

[0022] R 1As the hydrocarbon group, a hydrocarbon group substituted with a fluorine atom can also be preferably used. Specific 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. This is because the hydrocarbon group substituted with the fluorine atom mentioned above provides high stability to the compound.

[0023] R 2 is not particularly limited as long as it is a hydrocarbon group having 1 to 10 carbon atoms, and may have a substituent. Examples of the substituent on the hydrocarbon group include halogen atom substitution (halogeno group), and preferably fluorine substitution (fluoro group). Furthermore, the hydrocarbon group is preferably an unsubstituted aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms. Examples of the unsubstituted aliphatic saturated hydrocarbon group include linear, branched, or cyclic aliphatic hydrocarbon groups, and preferably linear or branched aliphatic hydrocarbon groups, and more preferably linear aliphatic hydrocarbon groups.

[0024] Also, R 2 The number of carbon atoms in the main chain of the hydrocarbon group represented by R is usually 1 or more, preferably 2 or more, and usually 10 or less, preferably 5 or less, more preferably 3 or less. 2 When the number of carbon atoms in the main chain of the hydrocarbon group represented by the formula (I), preferably the number of carbon atoms in the main chain of the saturated hydrocarbon group, is within this range, steric hindrance is reduced, making it easier for the action on the electrode to occur, and therefore, a synergistic improvement effect is more significantly exhibited by using the chain sulfonate ester in combination with one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, which will be described later.

[0025] R 2Specific examples of the alkyl group include alkyl groups having 1 to 10 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, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group; a vinyl group, a 1-propenyl group, a 2-propenyl group, an isopropenyl group, a 1-butenyl group, and a 2-butenyl group. alkenyl groups having 2 to 10 carbon atoms such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentenyl, 4-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 1-nonenyl, and 1-decenyl; alkynyl groups having 2 to 10 carbon atoms such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 1-heptynyl, 1-octynyl, 1-nonynyl, and 1-decynyl; and the like. Preferred are alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, 1-methylbutyl, 2-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl, more preferably methyl, ethyl, n-propyl, n-butyl, and n-pentyl, with methyl and ethyl being even more preferred and ethyl being particularly preferred, since this allows for efficient formation of a protective coating on the negative electrode.

[0026] R 2As the hydrocarbon group, a hydrocarbon group substituted with a fluorine atom can also be preferably used. Specific 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. This is because the hydrocarbon group substituted with the fluorine atom mentioned above provides high stability to the compound.

[0027] Specific examples of chain sulfonic acid esters include the following:

[0028] methanesulfonate esters such as methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, pentyl methanesulfonate, heptyl methanesulfonate, hexyl methanesulfonate, octyl methanesulfonate, nonyl methanesulfonate, decyl methanesulfonate, 2-propynyl methanesulfonate, 3-butynyl methanesulfonate, busulfan, methyl 2-(methanesulfonyloxy)propionate, ethyl 2-(methanesulfonyloxy)propionate, 2-propynyl 2-(methanesulfonyloxy)propionate, 3-butynyl 2-(methanesulfonyloxy)propionate, methyl methanesulfonyloxyacetate, ethyl methanesulfonyloxyacetate, 2-propynyl methanesulfonyloxyacetate and 3-butynyl methanesulfonyloxyacetate; ethanesulfonic acid esters such as methyl ethanesulfonate, ethyl ethanesulfonate, propyl ethanesulfonate, butyl ethanesulfonate, pentyl ethanesulfonate, heptyl ethanesulfonate, hexyl ethanesulfonate, octyl ethanesulfonate, nonyl ethanesulfonate, decyl ethanesulfonate, 2-propynyl ethanesulfonate, 3-butynyl ethanesulfonate, methyl 2-(ethanesulfonyloxy)propionate, ethyl 2-(ethanesulfonyloxy)propionate, 2-propynyl 2-(ethanesulfonyloxy)propionate, 3-butynyl 2-(ethanesulfonyloxy)propionate, methyl ethanesulfonyloxyacetate, ethyl ethanesulfonyloxyacetate, 2-propynyl ethanesulfonyloxyacetate and 3-butynyl ethanesulfonyloxyacetate; alkenylsulfonic acid esters such as methyl vinylsulfonate, ethyl vinylsulfonate, allyl vinylsulfonate, propargyl vinylsulfonate, methyl allylsulfonate, ethyl allylsulfonate, allyl allylsulfonate, propargyl allylsulfonate, and 1,2-bis(vinylsulfonyloxy)ethane; Methoxycarbonylmethyl methanedisulfonate, ethoxycarbonylmethyl methanedisulfonate, 1-methoxycarbonylethyl methanedisulfonate, 1-ethoxycarbonylethyl methanedisulfonate, methoxycarbonylmethyl 1,2-ethanedisulfonate, ethoxycarbonylmethyl 1,2-ethanedisulfonate, 1-methoxycarbonylethyl 1,2-ethanedisulfonate, 1-ethoxycarbonylethyl 1,2-ethanedisulfonate, methoxy 1,3-propanedisulfonate alkyl disulfonate esters such as carbonylmethyl, ethoxycarbonylmethyl 1,3-propanedisulfonate, 1-methoxycarbonylethyl 1,3-propanedisulfonate, 1-ethoxycarbonylethyl 1,3-propanedisulfonate, methoxycarbonylmethyl 1,3-butanedisulfonate, ethoxycarbonylmethyl 1,3-butanedisulfonate, 1-methoxycarbonylethyl 1,3-butanedisulfonate, and 1-ethoxycarbonylethyl 1,3-butanedisulfonate. Among these, methanesulfonate esters such as methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, pentyl methanesulfonate, heptyl methanesulfonate, hexyl methanesulfonate, octyl methanesulfonate, nonyl methanesulfonate, decyl methanesulfonate, 2-propynyl methanesulfonate, 3-butynyl methanesulfonate, busulfan, methyl 2-(methanesulfonyloxy)propionate, ethyl 2-(methanesulfonyloxy)propionate, 2-propynyl 2-(methanesulfonyloxy)propionate, 3-butynyl 2-(methanesulfonyloxy)propionate, methyl methanesulfonyloxyacetate, ethyl methanesulfonyloxyacetate, 2-propynyl methanesulfonyloxyacetate and 3-butynyl methanesulfonyloxyacetate; ethanesulfonic acid esters such as methyl ethanesulfonate, ethyl ethanesulfonate, propyl ethanesulfonate, butyl ethanesulfonate, pentyl ethanesulfonate, heptyl ethanesulfonate, hexyl ethanesulfonate, octyl ethanesulfonate, nonyl ethanesulfonate, decyl ethanesulfonate, 2-propynyl ethanesulfonate, 3-butynyl ethanesulfonate, methyl 2-(ethanesulfonyloxy)propionate, ethyl 2-(ethanesulfonyloxy)propionate, 2-propynyl 2-(ethanesulfonyloxy)propionate, 3-butynyl 2-(ethanesulfonyloxy)propionate, methyl ethanesulfonyloxyacetate, ethyl ethanesulfonyloxyacetate, 2-propynyl ethanesulfonyloxyacetate and 3-butynyl ethanesulfonyloxyacetate; are preferred, and methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, pentyl methanesulfonate, heptyl methanesulfonate, hexyl methanesulfonate, octyl methanesulfonate, nonyl methanesulfonate, decyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, propyl ethanesulfonate, butyl ethanesulfonate, pentyl ethanesulfonate, heptyl ethanesulfonate, hexyl ethanesulfonate, octyl ethanesulfonate, nonyl ethanesulfonate, and decyl ethanesulfonate are more preferred, and methanesulfonate Methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, butyl methanesulfonate, pentyl methanesulfonate, heptyl methanesulfonate, hexyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, propyl ethanesulfonate, butyl ethanesulfonate, pentyl ethanesulfonate, heptyl ethanesulfonate, and hexyl ethanesulfonate are more preferred, methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, and butyl methanesulfonate are particularly preferred, and ethyl methanesulfonate and propyl methanesulfonate are extremely preferred. In the case of cyclic sulfonate esters, the reactivity is higher than that of chain sulfonate esters, and the probability of reaction between anion radicals of the cyclic sulfonate esters increases, so the amount of reaction with the compound selected from the group consisting of fluorosulfonate, monofluorophosphate, difluorophosphate, imide salt, and oxalate decreases. For this reason, in this embodiment, chain sulfonate esters are used.

[0029] The content of the chain sulfonic acid ester is not particularly limited, but the content of the chain sulfonic acid ester relative to the total amount of the nonaqueous electrolyte (i.e., in 100% by mass of the nonaqueous electrolyte) is usually 1.0 × 10 -3 % by mass or more, preferably 1.0 × 10 -2The chain sulfonate ester content is preferably 10% by mass or less, more preferably 5% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, especially preferably 2% by mass or less, and particularly preferably 1% by mass or less. When the chain sulfonate ester content is within this range, the increase in resistance is small and the effects of the invention are significantly exhibited. Identification and measurement of the amount of chain sulfonate esters can be performed by nuclear magnetic resonance (NMR) analysis or gas chromatography (GC) analysis. NMR analysis is usually performed, but GC analysis is also performed when the solvent peak makes it difficult to identify other compounds.

[0030] <1-2. Fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, oxalates> The non-aqueous electrolyte solution of the present invention contains at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates. In the case of a nonaqueous electrolyte solution containing a monofluorophosphate or a difluorophosphate, the electrolyte solution contains a chain sulfonate ester and a monofluorophosphate or a difluorophosphate, and the mass ratio of the content of the chain sulfonate ester to the content of the monofluorophosphate or the difluorophosphate is 10 / 90 or more and 82 / 18 or less. This range allows for efficient suppression of side reactions in the system and stable formation of a coating on the positive electrode, which is excellent in terms of suppressing the room-temperature discharge resistance increase rate. In addition, in the case of a non-aqueous electrolyte solution containing a compound selected from the group consisting of fluorosulfonates, imide salts, and oxalates, the total content of at least one compound selected from the group consisting of fluorosulfonates, imide salts, and oxalates is 1.0 × 10 -3The content of the chain sulfonate ester is from 10 / 90 to 99.99 / 0.01 by mass, and the mass ratio of the content of the chain sulfonate ester to the content of at least one compound selected from the group consisting of fluorosulfonates, imide salts, and oxalates is from 10 / 90 to 99.99 / 0.01 by mass. This range allows for efficient suppression of side reactions in the nonaqueous electrolyte secondary battery system for energy devices and stable formation of a coating on the positive electrode, which is excellent in terms of suppressing the rate of increase in discharge resistance at room temperature and / or low temperature. The mass ratio of the content of the chain sulfonic acid ester to the content of at least one compound selected from the group consisting of fluorosulfonates, imide salts, and oxalates is preferably 20 / 80 or more, more preferably 30 / 70 or more, even more preferably 40 / 60, particularly preferably 50 / 50, particularly preferably 65 / 35 or more, and most preferably 80 / 20 or more, while it is preferably 99.9 / 0.1 or less, more preferably 98.5 / 1.5 or less, even more preferably 95 / 5 or less, and particularly preferably 90 / 10 or less. When two or more compounds selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates are contained, the total content of the two or more compounds is used to calculate the mass ratio to the content of the chain sulfonate ester. The identification and content of fluorosulfonates, monofluorophosphates, difluorophosphates, imides, and oxalates can be measured by nuclear magnetic resonance (NMR) analysis or ion chromatography (IC) analysis. IC analysis is usually performed, but NMR analysis is also performed when it is difficult to identify the compounds from the peaks.

[0031] <1-2-1. Fluorosulfonates> The fluorosulfonate salt in this embodiment is not particularly limited as long as it is a salt having at least one fluorosulfonic acid structure in the molecule. By using the chain sulfonic acid ester and the fluorosulfonate salt in combination in the nonaqueous electrolyte solution of this embodiment, the durability characteristics of an energy device using this electrolyte solution can be improved, that is, the room temperature and / or low temperature discharge resistance increase rate can be improved (suppressed).

[0032] The counter cation in the fluorosulfonate salt 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. 131 ~R 134 The organic group having 1 to 12 carbon atoms represented by is not particularly limited, and examples thereof 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 134 are each 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 preferred.

[0033] Examples of fluorosulfonates include lithium fluorosulfonate, sodium fluorosulfonate, potassium fluorosulfonate, rubidium fluorosulfonate, and cesium fluorosulfonate, with lithium fluorosulfonate being preferred.

[0034] The fluorosulfonate may be used alone or in any combination and ratio of two or more. The content of the fluorosulfonate (total amount when two or more types are used) is usually 1.0 × 10 -3 The fluorosulfonate content is at least 0.05% by mass, preferably at least 0.1% by mass, more preferably at least 0.2% by mass, more preferably at least 0.3% by mass, more preferably at least 0.4% by mass, and is usually at most 10% by mass, preferably at most 8% by mass, more preferably at most 7% by mass, more preferably at most 6% by mass, more preferably at most 5% by mass, more preferably at most 4% by mass, even more preferably at most 3% by mass, more preferably at most 2% by mass, and more preferably at most 1% by mass. When the fluorosulfonate content is within this range, side reactions are less likely to occur in the energy device, and resistance is less likely to increase.

[0035] The mass ratio of the chain sulfonate content to the fluorosulfonate content (total amount when two or more types are used) (chain sulfonate / fluorosulfonate) is usually 10 / 90 or more, preferably 20 / 80 or more, more preferably 30 / 70 or more, even more preferably 40 / 60, especially preferably 50 / 50, particularly preferably 65 / 35 or more, and most preferably 80 / 20 or more. Meanwhile, it is usually 99.99 / 0.01 or less, preferably 99.9 / 0.1 or less, more preferably 98.5 / 1.5 or less, even more preferably 95 / 5 or less, and particularly preferably 90 / 10 or less. A mass ratio within this range can significantly improve energy device characteristics, particularly durability. While the underlying mechanism is unclear, it is believed that mixing at this ratio minimizes side reactions of the additive on the electrode. In particular, when the mass ratio is 50 / 50 or more, the reduction reaction of the chain sulfonate ester occurs more easily than the negative electrode side reaction of the fluorosulfonate, and a stable composite coating is suitably produced, which is preferable.

[0036] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total content of fluorosulfonates to the content of LiPF6 (fluorosulfonates / LiPF6) 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 particularly preferably 0.05 or less. When this mass ratio is within this range, the energy device characteristics, particularly durability characteristics, can be significantly improved. Although the mechanism behind this is unclear, it is thought that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0037] <1-2-2. Monofluorophosphates and difluorophosphates> The monofluorophosphate and difluorophosphate are not particularly limited as long as they are salts each having at least one monofluorophosphate or difluorophosphate structure in the molecule. In the nonaqueous electrolyte solution of this embodiment, by using the chain sulfonic acid ester in combination with one or more salts selected from monofluorophosphates and difluorophosphates, the durability of an energy device using this electrolyte solution can be improved, i.e., the room temperature discharge resistance increase rate can be improved (suppressed).

[0038] The counter cation in the monofluorophosphate and difluorophosphate is not particularly limited, and may be lithium, sodium, potassium, magnesium, calcium, NR 121 R 122 R 123 R 124 (In the formula, R 121 ~R 124 are independently a hydrogen atom or an organic group having 1 to 12 carbon atoms. 121 ~R 124The organic group having 1 to 12 carbon atoms represented by is not particularly limited, and examples thereof 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. 121 ~R 124 are each 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 preferred.

[0039] Examples of monofluorophosphates and difluorophosphates include lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, etc., with lithium monofluorophosphate and lithium difluorophosphate being preferred, and lithium difluorophosphate being more preferred. The monofluorophosphates and difluorophosphates may be used alone or in any combination and ratio of two or more.

[0040] The content of one or more fluorophosphates selected from monofluorophosphates and difluorophosphates (the total amount when there are two or more types) in 100% by mass of the non-aqueous electrolyte is usually 1.0 × 10 -3 The fluorophosphate content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and particularly preferably 0.3% by mass or more, and is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, especially preferably 1.5% by mass or less, and particularly preferably 1% by mass or less. When the fluorophosphate content is within this range, the effect of improving the initial irreversible capacity is significantly exhibited when the nonaqueous electrolyte solution is used in an energy device.

[0041] The mass ratio of the chain sulfonate ester to one or more fluorophosphates selected from monofluorophosphates and difluorophosphates (total amount when two or more types are used) {mass of chain sulfonate ester / (mass of one or more fluorophosphates selected from monofluorophosphates and difluorophosphates)} is usually 10 / 90 or more, preferably 20 / 80 or more, more preferably 30 / 70 or more, even more preferably 40 / 60 or more, and particularly preferably 50 / 50 or more, while it is usually 82 / 18 or less, preferably 80 / 20 or less, more preferably 75 / 25 or less, even more preferably 70 / 30 or less, and particularly preferably 60 / 40 or less. When the mass ratio is within this range, energy device characteristics, particularly durability, can be significantly improved. Although the underlying mechanism is unclear, it is thought that mixing at this ratio minimizes side reactions of the additive on the electrode. In particular, a mass ratio of 50 / 50 or more is preferable because the reduction reaction of the chain sulfonate ester occurs more easily than the negative electrode side reaction caused by the monofluorophosphate or difluorophosphate, and a stable composite coating is suitably produced. Note that, since the monofluorophosphate or difluorophosphate has a strong initial interaction with the positive electrode, the upper limit of the effective ratio with the chain sulfonate ester is thought to be different from that of the fluorosulfonate, imide salt, and oxalate.

[0042] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total content of one or more fluorophosphates selected from monofluorophosphates and difluorophosphates to the content of LiPF6 (fluorophosphate / LiPF6) is usually 5.0 × 10 -5 or more, preferably 1.0 × 10 -4 More preferably, 1.0 × 10 -3 More preferably, 1.5 × 10 -3The 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 particularly preferably 0.05 or less. When this mass ratio is within this range, the energy device characteristics, particularly durability characteristics, can be significantly improved. Although the mechanism behind this is unclear, it is thought that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0043] <1-2-3. Imide salts> Imide salts have a structure in which two sulfonyl groups are bonded to a nitrogen atom (-SO2N - SO2-) or a structure with two phosphoryl groups attached to a nitrogen atom (-P(O)N - The salt is not particularly limited as long as it is a salt of an anion having the formula (I) and a counter cation. In the nonaqueous electrolyte solution of the present embodiment, by using the chain sulfonic acid ester and the imide salt in combination, the durability of an energy device using this electrolyte solution can be improved, that is, the rate of increase in discharge resistance at room temperature and / or low temperature can be improved (suppressed). The counter cation in the imide salt is not particularly limited, and may be lithium, sodium, potassium, magnesium, calcium, NR 221 R 222 R 223 R 224 (In the formula, R 221 ~R 224 are independently a hydrogen atom or an organic group having 1 to 12 carbon atoms. 221 ~R 224 The organic group having 1 to 12 carbon atoms represented by is not particularly limited, and examples thereof 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. 221 ~R 224are each 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 preferred.

[0044] Examples of lithium imide salts include lithium carbonyl imide salts, lithium sulfonylimide salts such as lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethanesulfonyl)imide, and lithium bis(nonafluorobutanesulfonyl)imide, and lithium phosphonylimide salts such as lithium bis(difluorophosphonyl)imide. Among these, lithium bis(fluorosulfonyl)imide is more preferred because it causes fewer side reactions at the positive electrode.

[0045] The imide salt may be used alone or in any combination and ratio of two or more. The content of the imide salt (total amount when two or more types are used) is usually 1.0 × 10 -3 The imide salt content is at least 0.05% by mass, preferably at least 0.1% by mass, more preferably at least 0.2% by mass, more preferably at least 0.3% by mass, more preferably at least 0.4% by mass, and is usually at most 10% by mass, preferably at most 8% by mass, more preferably at most 7% by mass, more preferably at most 6% by mass, more preferably at most 5% by mass, more preferably at most 4% by mass, more preferably at most 3% by mass, more preferably at most 2% by mass, and more preferably at most 1% by mass. If the imide salt content is within this range, side reactions at the negative electrode are reduced.

[0046] The mass ratio of the chain sulfonate ester to the imide salt (total amount when two or more types are used) (chain sulfonate ester / imide salt) is typically 10 / 90 or more, preferably 20 / 80 or more, more preferably 30 / 70 or more, even more preferably 40 / 60 or more, and particularly preferably 50 / 50 or more. Meanwhile, the mass ratio is typically 99.99 / 0.01 or less, preferably 99.9 / 0.1 or less, more preferably 98.5 / 1.5 or less, even more preferably 95 / 5 or less, and particularly preferably 90 / 10 or less. Energy device characteristics, particularly durability, can be significantly improved. While the underlying mechanism is unclear, mixing at this ratio is thought to minimize side reactions of the additives on the electrode. A mass ratio of 50 / 50 or more is particularly preferred because the reduction reaction of the chain sulfonate ester is more likely to occur than the negative electrode side reaction caused by the imide salt, resulting in the formation of a stable composite coating.

[0047] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total content of imide salts to the content of LiPF6 (imide salt / LiPF6) 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 particularly preferably 0.05 or less. When this mass ratio is within this range, the energy device characteristics, particularly durability characteristics, can be significantly improved. Although the mechanism behind this is unclear, it is thought that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0048] <1-2-4. Oxalates> In this embodiment, the oxalate is not particularly limited as long as it is a compound having at least one oxalic acid structure in the molecule. By using a chain sulfonic acid ester and an oxalate in combination in the nonaqueous electrolyte solution of this embodiment, the durability characteristics, i.e., the room temperature and / or low temperature discharge resistance increase rate, of an energy device using this electrolyte solution can be improved. The oxalate is preferably a metal salt represented by the following formula (9): This salt has an oxalato complex as the anion.

[0049] [ka]

[0050] (In the formula, M 1 is an element selected from the group consisting of Groups 1 and 2 of the periodic table and aluminum (Al), and M 2 is an element selected from the group consisting of transition metals, groups 13, 14, and 15 of the periodic table, and R 91 represents a group selected from the group consisting of halogen, alkyl groups having from 1 to 11 carbon atoms, and halogen-substituted alkyl groups having from 1 to 11 carbon atoms, a and b are positive integers, c is 0 or a positive integer, and d is an integer from 1 to 3. M 1 In terms of the properties of an energy device such as a lithium secondary battery when the nonaqueous electrolyte solution of this embodiment is used in the energy device, lithium, sodium, potassium, magnesium, and calcium are preferred, and lithium is particularly preferred.

[0051] M 2 Among these, boron and phosphorus are particularly preferred in terms of electrochemical stability when used in lithium-based energy devices such as lithium secondary batteries and lithium ion capacitors. R 91 Examples of the alkyl group include fluorine, chlorine, methyl, trifluoromethyl, ethyl, pentafluoroethyl, propyl, isopropyl, butyl, sec-butyl, and tert-butyl, with fluorine and trifluoromethyl being preferred.

[0052] Examples of the metal salt represented by formula (9) include the following. lithium oxalatoborate salts such as lithium difluorooxalatoborate and lithium bis(oxalato)borate; lithium oxalatophosphate salts such as lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, and lithium tris(oxalato)phosphate; Of these, lithium bis(oxalato)borate and lithium difluorobis(oxalato)phosphate are preferred, with lithium bis(oxalato)borate being more preferred.

[0053] The oxalate may be used alone or in any combination and ratio of two or more. The content of the oxalate (total amount when two or more types are used) is usually 1.0 × 10 in 100 mass% of the non-aqueous electrolyte solution. -3 The oxalate content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, and is usually 10% by mass or less, preferably 7% by mass or less, more preferably 6% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, particularly preferably 2% by mass or less, and most preferably 1% by mass or less. When the oxalate content is within this range, it is easy to control the output characteristics, load characteristics, low-temperature characteristics, cycle characteristics, high-temperature storage characteristics, etc. of the energy device.

[0054] The mass ratio of the chain sulfonate ester to the oxalate (total amount when two or more types are used) (chain sulfonate ester / oxalate) is typically 10 / 90 or more, preferably 20 / 80 or more, more preferably 30 / 70 or more, even more preferably 40 / 60 or more, and particularly preferably 50 / 50 or more. Meanwhile, the mass ratio is typically 99.99 / 0.01 or less, preferably 99.9 / 0.1 or less, more preferably 98.5 / 1.5 or less, even more preferably 95 / 5 or less, and particularly preferably 90 / 10 or less. Energy device characteristics, particularly durability, can be significantly improved. While the underlying mechanism is unclear, mixing at this ratio is thought to minimize side reactions of the additive on the electrode. A mass ratio of 50 / 50 or more is particularly preferred because it favors the reduction reaction of the chain sulfonate over the negative electrode side reaction caused by the oxalate, resulting in the formation of a stable composite coating.

[0055] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total oxalate content to the LiPF6 content (oxalate / LiPF6) 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 particularly preferably 0.05 or less. When this mass ratio is within this range, the energy device characteristics, particularly durability characteristics, can be significantly improved. Although the mechanism behind this is unclear, it is thought that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0056] <1-2-5. Total concentration of additives used in combination, etc.> When the non-aqueous electrolyte solution contains LiPF6 in addition to at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, the mass ratio of the total content of the additives to the content of LiPF6 (total content of additives / LiPF6 content) is usually 5.0 × 10 -5 or more, preferably 1.0 × 10 -4 More preferably, 1.0 × 10 -3 The mass ratio is preferably 0.02 or more, more preferably 0.025 or more, and usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, and even more preferably 0.35 or less. When the mass ratio is within this range, the energy device characteristics, particularly the durability characteristics, can be significantly improved. Although the mechanism behind this is unclear, it is thought that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0057] When the non-aqueous electrolyte solution contains at least two compounds selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, the total content of the additives other than the chain sulfonate ester in 100% by mass of the non-aqueous electrolyte solution is usually 1.0 × 10 -3 The total content of the additives is 10% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, and particularly preferably 0.6% by mass or more, and is usually 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, and particularly preferably 5% by mass or less. If the total content of the additives is within this range, side reactions within the energy device system can be efficiently suppressed.

[0058] <1-3. Electrolytes> The nonaqueous electrolyte solution of this embodiment, like a general nonaqueous electrolyte solution, usually contains an electrolyte as a component. There are no particular restrictions on the electrolyte used in the nonaqueous electrolyte solution of this embodiment, and known electrolytes can be used. The total concentration of the electrolyte in the nonaqueous electrolyte solution is not particularly limited, but is usually greater than 8% by mass, preferably 8.5% by mass or more, and more preferably 9% by mass or more, relative to the total amount of the nonaqueous electrolyte solution. It is also usually 20% by mass or less, preferably 17% by mass or less, and more preferably 16% by mass or less. When the total concentration of the electrolyte is within the above range, the electrical conductivity is appropriate for the operation of a nonaqueous electrolyte secondary battery, and sufficient output characteristics tend to be obtained. Specific examples of the electrolyte are described in detail below.

[0059] <1-3-1. Lithium salts> As the electrolyte in the nonaqueous electrolytic solution of this embodiment, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and one or more of any lithium salts can be used. Specific examples include the following:

[0060] for example, Lithium fluorophosphate salts such as LiPF6, Li2PO3F, and LiPO2F2; Lithium tungstate salts such as LiWOF5; Lithium carboxylates such as CF3CO2Li; Lithium sulfonate salts such as CH3SO3Li and FSO3Li; Lithium imide salts such as LiN(FSO2)2 and LiN(CF3SO2)2; Lithium methide salts such as LiC(FSO2)3; lithium oxalate salts such as LiB(C2O4)2; Other fluorine-containing organic lithium salts such as LiPF4(CF3)2; etc. The lithium salts listed above may be used alone or in combination of two or more. However, when a lithium salt electrolyte corresponding to the co-additive is contained in the non-aqueous electrolyte solution, an electrolyte other than the lithium salt corresponding to the co-additive must be contained.

[0061] In order to improve the charge / discharge rate characteristics and impedance characteristics of an energy device in a high-temperature environment as well as improve its charge / discharge storage characteristics, the electrolyte in the nonaqueous electrolytic solution of this embodiment is preferably selected from inorganic lithium salts, lithium fluorophosphate salts, lithium sulfonate salts, imide salts, and lithium oxalate salts. Among these, when the content of lithium monofluorophosphate salts or lithium difluorophosphate salts is 7% by mass or less in 100% by mass of the nonaqueous electrolytic solution, the electrolyte is preferably at least one selected from LiPF6, LiBF4, LiClO4, LiB(C2O4)2, Li(FSO2)2N, and Li(CF3SO2)2N, more preferably at least one selected from LiPF6, LiBF4, Li(FSO2)2N, and Li(CF3SO2)2N, even more preferably at least one selected from LiPF6 and Li(FSO2)2N, and particularly preferably LiPF6. The total content of at least one lithium salt selected from the group consisting of lithium fluorosulfonate salts, imide salts, and lithium oxalate salts is 1.0 × 10 in 100 mass% of the non-aqueous electrolyte solution. -3 When the content is 7% by mass or more, it is preferably at least one selected from LiPF6, LiBF4, and LiClO4, more preferably at least one selected from LiPF6 and LiBF4, and particularly preferably LiPF6.

[0062] When a lithium salt is used as the main salt of a non-aqueous electrolyte solution, the concentration of the lithium salt is usually 8% by mass or more, preferably 8.5% by mass or more, and more preferably 9% by mass or more, based on the total amount of the non-aqueous electrolyte solution. It is also usually 20% by mass or less, preferably 17% by mass or less, and more preferably 16% by mass or less. When the concentration of the lithium salt as the main salt is within the above range, the electrical conductivity is appropriate for the operation of the energy device, and sufficient output characteristics tend to be obtained. When a lithium salt is used as the auxiliary salt of a non-aqueous electrolyte solution, the concentration of the lithium salt is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, particularly preferably 0.4% by mass or more, based on the total amount of the non-aqueous electrolyte solution, and is usually 2% by mass or less, particularly preferably 1% by mass or less. When the concentration of the lithium salt as the auxiliary salt is within this range, side reactions in the energy device are reduced, and resistance is less likely to increase.

[0063] If the non-aqueous electrolyte contains LiPF6, PF6 - All anions are considered to be derived from LiPF6, and the mass ratio of the total content of the chain sulfonate esters to the content of LiPF6 calculated from this (chain sulfonate esters / LiPF6) is usually 5.0 × 10 -5 or more, preferably 1.0 × 10 -3 The LiPF6 content is preferably 0.01 or more, more preferably 0.02 or more, and particularly preferably 0.025 or more, and is usually 0.3 or less, preferably 0.2 or less, more preferably 0.1 or less, even more preferably 0.09 or less, and particularly preferably 0.08 or less. When the LiPF6 content is within this range, the properties of the energy device, particularly its durability, can be significantly improved. While the underlying mechanism is unclear, it is believed that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system. Similarly, in the mass ratio to the additives other than the chain sulfonic acid ester, the mass of LiPF6 in the non-aqueous electrolyte is PF6 - All anions are assumed to be derived from LiPF6, and the mass is calculated from this.

[0064] <1-4. Non-aqueous solvents> Like common nonaqueous electrolytes, nonaqueous electrolytes typically contain a nonaqueous solvent as a main component, capable of dissolving the electrolyte. There are no particular limitations on the nonaqueous solvent, and known organic solvents can be used. The organic solvent is not particularly limited, and examples include saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, ether compounds, sulfone compounds (excluding chain sulfonic acid esters), and cyclic carboxylic acid esters. Among these, the organic solvent is preferably at least one selected from saturated cyclic carbonates, chain carbonates, and chain carboxylic acid esters. It is more preferable that the organic solvent contains at least a chain carboxylic acid ester, as this facilitates improving the initial capacity of the energy device. These organic solvents can be used alone or in combination of two or more. These organic solvents are described below.

[0065] <1-4-1. Saturated cyclic carbonates> The saturated cyclic carbonate typically includes one having an alkylene group having 2 to 4 carbon atoms, and saturated cyclic carbonates having 2 to 3 carbon atoms are preferably used from the viewpoint of improving the energy device properties resulting from an improved degree of lithium ion dissociation.

[0066] Examples of saturated cyclic carbonates include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferred, and ethylene carbonate, which is less susceptible to oxidation and reduction, is more preferred. The saturated cyclic carbonates may be used alone or in any combination and ratio of two or more.

[0067] The content of the saturated cyclic carbonate is not particularly limited and can be any amount as long as it does not significantly impair the effects of the present invention. However, when one type is used alone, the lower limit of the content is typically 3% by volume or more, preferably 5% by volume or more, based on the total amount of solvent in the non-aqueous electrolyte. Setting the lower limit of the saturated cyclic carbonate content within this range avoids a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte, and facilitates achieving favorable ranges for the large-current discharge characteristics, negative electrode stability, and cycle characteristics of energy devices such as non-aqueous electrolyte secondary batteries. Furthermore, the upper limit of the saturated cyclic carbonate content is typically 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less, based on the total amount of solvent in the non-aqueous electrolyte. Setting the content within this range tends to improve the oxidation-reduction resistance of the non-aqueous electrolyte and improve stability during high-temperature storage. In this embodiment, the volume % refers to the volume at 25° C. and 1 atmosphere.

[0068] <1-4-2. Chain carbonate> As the chain carbonate, 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.

[0069] Specific examples of chain carbonates include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, and t-butyl ethyl carbonate.

[0070] Of these, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate are preferred, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferred.

[0071] Furthermore, chain carbonates having fluorine atoms (hereinafter sometimes abbreviated as "fluorinated chain carbonate") 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, and preferably 4 or less. When the fluorinated chain carbonate has multiple fluorine atoms, they may be bonded to the same carbon or different carbons. Examples of fluorinated chain carbonates include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

[0072] Examples of fluorinated dimethyl carbonate derivatives include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis(fluoromethyl)carbonate, bis(difluoro)methyl carbonate, and bis(trifluoromethyl)carbonate.

[0073] Examples of fluorinated ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

[0074] Examples of fluorinated diethyl carbonate derivatives include ethyl-(2-fluoroethyl)carbonate, ethyl-(2,2-difluoroethyl)carbonate, bis(2-fluoroethyl)carbonate, ethyl-(2,2,2-trifluoroethyl)carbonate, 2,2-difluoroethyl-2'-fluoroethylcarbonate, bis(2,2-difluoroethyl)carbonate, 2,2,2-trifluoroethyl-2'-fluoroethylcarbonate, 2,2,2-trifluoroethyl-2',2'-difluoroethylcarbonate, and bis(2,2,2-trifluoroethyl)carbonate.

[0075] The chain carbonate may be used alone or in any combination of two or more kinds in any ratio.

[0076] The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, and usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less, relative to the total volume of the solvent in the nonaqueous electrolyte. By setting the content of the chain carbonate within the above range, the viscosity of the nonaqueous electrolyte can be set within an appropriate range, a decrease in ionic conductivity can be suppressed, and the output characteristics of energy devices such as nonaqueous electrolyte secondary batteries can be easily set within a good range.

[0077] Furthermore, by combining a specific chain carbonate with ethylene carbonate in a specific content, the performance of the energy device can be significantly improved.

[0078] For example, when dimethyl carbonate and ethyl methyl carbonate are selected as specific chain carbonates, the content of ethylene carbonate is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but 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 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. By setting the contents of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate within the above ranges, high temperature stability is excellent and gas generation tends to be suppressed.

[0079] <1-4-3. Chain carboxylic acid esters> The chain carboxylic acid ester preferably has 3 to 12 carbon atoms, and more preferably has 3 to 5 carbon atoms. Examples of chain carboxylic acid esters include: From the viewpoint of reducing side reactions at the negative electrode, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, n-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, n-butyl butyrate, methyl valerate, ethyl valerate, n-propyl valerate, n-butyl valerate, methyl pivalate, ethyl pivalate, n-propyl pivalate, or n-butyl pivalate is preferred; from the viewpoint of improving ionic conductivity due to a decrease in the viscosity of the electrolyte, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, or n-butyl propionate is more preferred; methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate are even more preferred, with methyl acetate or ethyl acetate being particularly preferred.

[0080] When a chain carboxylic acid ester is used as a 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, based on 100% by volume of the non-aqueous solvent. It can also be contained at 50% by volume or less, more preferably 45% by volume or less, and even more preferably 40% by volume or less. When the content of the chain carboxylic acid ester is within the above range, the electrical conductivity of the non-aqueous electrolyte is improved, and the input / output characteristics and charge / discharge rate characteristics of energy devices such as non-aqueous electrolyte secondary batteries are easily improved. Furthermore, an increase in negative electrode resistance is suppressed, and the input / output characteristics and charge / discharge rate characteristics of energy devices such as non-aqueous electrolyte secondary batteries are easily maintained within a favorable range.

[0081] When a chain carboxylic acid ester is used as a non-aqueous solvent, it is preferably used in combination with a cyclic carbonate, and more preferably in combination with a chain carbonate, because it lowers the low-temperature deposition temperature of the electrolyte while also lowering the viscosity of the non-aqueous electrolyte solution, improving ionic conductivity, enabling even higher input and output even at low temperatures, and further reducing swelling of energy devices, particularly batteries.

[0082] <1-4-4. Ether compounds> As the ether-based compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferred.

[0083] As the cyclic ethers having 3 to 10 carbon atoms, dimethoxymethane, diethoxymethane, methoxyethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether are preferred because they have a high ability to solvate lithium ions and improve ionic dissociation. Dimethoxymethane, diethoxymethane, and methoxyethoxymethane are particularly preferred because they have low viscosity and provide high ionic conductivity.

[0084] Examples of cyclic ethers having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, and fluorinated compounds thereof.

[0085] The content of the ether-based compound is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. However, it 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 100% by volume of the non-aqueous solvent. When the content of the ether-based compound is within the above-mentioned preferred range, it is easy to ensure the effects of improving the degree of lithium ion dissociation and improving ionic conductivity due to reduced viscosity. Furthermore, when the negative electrode active material is a carbon-based material, the phenomenon of co-insertion of chain ethers with lithium ions can be suppressed, thereby allowing the input / output characteristics and charge / discharge rate characteristics to be within appropriate ranges.

[0086] <1-4-5. Sulfone compounds> Examples of sulfone compounds (excluding chain sulfonate esters) include sulfolanes, and among these, sulfolane and sulfolane derivatives are preferred. 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.

[0087] In particular, 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.

[0088] The sulfone-based compounds may be used alone or in any combination of two or more in any ratio. The content of the sulfone-based compound is not particularly limited and can be any amount as long as it does not significantly impair the effects of the present invention. However, when one type is used alone, the lower limit of the content is typically 3% by volume or more, preferably 5% by volume or more, based on the total amount of solvent in the non-aqueous electrolyte solution. Setting the lower limit of the sulfone-based compound content within this range avoids a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte solution, and facilitates achieving good ranges for the large-current discharge characteristics, negative electrode stability, and cycle characteristics of non-aqueous electrolyte secondary batteries, such as non-aqueous electrolyte secondary batteries. Furthermore, the upper limit of the content of the saturated cyclic carbonate is typically 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less, based on the total amount of solvent in the non-aqueous electrolyte solution. Setting the content within this range tends to improve the oxidation-reduction resistance of the non-aqueous electrolyte solution and improve stability during high-temperature storage.

[0089] <1-4-6. Cyclic carboxylic acid esters> The cyclic carboxylic acid ester preferably has 3 to 12 carbon atoms. Specific examples include γ-butyrolactone, γ-valerolactone, γ-caprolactone, ε-caprolactone, etc. Among these, γ-butyrolactone is particularly preferred from the viewpoint of improving the energy device characteristics resulting from the improvement in the degree of lithium ion dissociation.

[0090] The cyclic carboxylic acid ester may be used alone or as a mixture of two or more kinds in any combination and ratio. The content of the cyclic carboxylic acid ester is preferably 5% by volume or more, more preferably 10% by volume or more, based on 100% by volume of the non-aqueous solvent. Within this range, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the large-current discharge characteristics of the energy device are likely to be improved. Furthermore, the content of the cyclic carboxylic acid ester is preferably 50% by volume or less, more preferably 40% by volume or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is kept within an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and the large-current discharge characteristics of the energy device are likely to be kept within a good range.

[0091] <1-5. Auxiliaries> The non-aqueous electrolyte solution may contain the following auxiliary agents within the scope of the present invention. The auxiliary agents are not particularly limited, and examples thereof include cyclic carbonates having carbon-carbon unsaturated bonds, fluorine-containing cyclic carbonates, sulfur-containing organic compounds, phosphorus-containing organic compounds, organic compounds having cyano groups, organic compounds having isocyanate groups, silicon-containing compounds, borates, and aromatic carbonates. Of these, the auxiliary agent is preferably at least one selected from cyclic carbonates having carbon-carbon unsaturated bonds and fluorine-containing cyclic carbonates. These may be used alone or in combination of two or more. Specific auxiliary agents are described below.

[0092] <1-5-1. 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.

[0093] 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, or ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond, or a carbon-carbon triple bond are preferred.

[0094] 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; Among these, vinylene carbonate, vinylethylene carbonate, and ethynylethylene carbonate are preferred because they form a more stable interface protective film, with vinylene carbonate and vinylethylene carbonate being more preferred, and vinylene carbonate being even more preferred.

[0095] The unsaturated cyclic carbonate may be used alone or in any combination and ratio of two or more. The content of the unsaturated cyclic carbonate (total amount when two or more types are used) is 1.0 × 10 in 100 mass% of the nonaqueous electrolyte solution. -3 The content of the unsaturated cyclic carbonate can be 5% by mass or less, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and can be 5% by mass or less, preferably 4% by mass or less, 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.

[0096] The mass ratio of the chain sulfonate ester to the unsaturated cyclic carbonate (total amount when two or more types are used) (chain sulfonate ester / unsaturated cyclic carbonate) is typically 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 typically 10,000 / 100 or less, preferably 500 / 100 or less, and more preferably 300 / 100 or less. A mass ratio within this range can significantly improve energy device characteristics, particularly durability. While the underlying mechanism is unclear, it is believed that mixing at this ratio minimizes side reactions of the additive on the electrode.

[0097] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total content of unsaturated cyclic carbonate to the content of LiPF6 (unsaturated cyclic carbonate / LiPF6) is usually 5.0 x 10 -5 or more, preferably 1.0 × 10 -3 The mass ratio is preferably 0.5 or less, more preferably 0.01 or more, even more preferably 0.02 or more, and particularly preferably 0.025 or more, and is usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, and even more preferably 0.35 or less. When the mass ratio is within this range, the energy device characteristics, particularly the durability characteristics, can be significantly improved. While the underlying mechanism is unclear, it is believed that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0098] <1-5-2. 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 sometimes referred to as "fluorinated ethylene carbonate") and derivatives thereof. 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.

[0099] 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, monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate are preferred because they impart high ionic conductivity to the electrolyte and facilitate the formation of a stable interface protective film.

[0100] The fluorine-containing cyclic carbonate may be used alone or in any combination and ratio of two or more. The content of the fluorine-containing cyclic carbonate (total amount when two or more types are used) in 100 mass% of the nonaqueous electrolyte solution is preferably 1.0 × 10 -3The content of the fluorine-containing cyclic carbonate in the non-aqueous solvent is preferably 1% by volume or more, more preferably 0.01% by volume or more, even more preferably 0.1% by volume or more, even more preferably 0.5% by volume or more, particularly preferably 1% by volume or more, and most preferably 1.2% by volume or more, and is preferably 10% by volume or less, more preferably 7% by volume or less, even more preferably 5% by volume or less, particularly preferably 3% by volume or less, and most preferably 2% by volume or less, based on 100% by volume of the non-aqueous solvent.

[0101] The mass ratio of the chain sulfonate ester to the fluorine-containing cyclic carbonate (total amount when two or more types are used) (chain sulfonate ester / 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, and is usually 10,000 / 100 or less, preferably 500 / 100 or less, and more preferably 300 / 100 or less. When the mass ratio is within this range, the energy device characteristics, particularly durability, can be significantly improved. While the underlying mechanism is unclear, it is believed that mixing at this ratio minimizes side reactions of the additive on the electrode.

[0102] When the non-aqueous electrolyte contains LiPF6, the mass ratio of the total content of fluorine-containing cyclic carbonate to the content of LiPF6 (fluorine-containing cyclic carbonate / LiPF6) is usually 0.00005 or more, preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.02 or more, particularly preferably 0.025 or more, and usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less, and even more preferably 0.35 or less. When this mass ratio is within this range, energy device characteristics, particularly durability, can be significantly improved. Although the underlying mechanism is unclear, it is believed that mixing at this ratio minimizes the decomposition side reaction of LiPF6 within the energy device system.

[0103] <1-6. Method for producing non-aqueous electrolyte> The nonaqueous electrolytic solution can be prepared by dissolving an electrolyte, a chain sulfonic acid ester, and at least one compound selected from the group consisting of fluorosulfonate, monofluorophosphate, difluorophosphate, imide salt, and oxalate, and, if necessary, the above-mentioned "auxiliary agent" or the like, in the above-mentioned nonaqueous solvent.

[0104] When preparing a non-aqueous electrolyte solution, it is preferable to dehydrate in advance the raw materials of the non-aqueous electrolyte solution, i.e., electrolytes such as lithium salts, non-aqueous solvents, chain sulfonic acid esters, at least one compound selected from the group consisting of fluorosulfonates, monofluorophosphates, difluorophosphates, imide salts, and oxalates, and auxiliary agents, etc. The degree of dehydration is preferably such that the water content of the raw materials is usually 50 mass ppm or less, preferably 30 mass ppm or less.

[0105] Removing water from the non-aqueous electrolyte solution makes it difficult for water electrolysis, reactions between water and lithium metal, and hydrolysis of lithium salts to occur. There are no particular limitations on the dehydration method. For example, when the object to be dehydrated is a liquid such as a non-aqueous solvent, a desiccant such as a molecular sieve may be used. Furthermore, when the object to be dehydrated is a solid such as an electrolyte, it may be dried by heating below the temperature at which decomposition occurs.

[0106] <2. Energy devices using non-aqueous electrolytes> An energy device using a nonaqueous electrolyte solution includes a plurality of electrodes capable of absorbing and releasing metal ions and the nonaqueous electrolyte solution described above. Specific examples of types of energy devices include primary batteries, secondary batteries, and metal ion capacitors such as lithium ion capacitors. Among these, primary batteries or secondary batteries are preferred, secondary batteries are more preferred, and lithium secondary batteries are particularly preferred. The nonaqueous electrolyte solution used in these energy devices is also preferably a so-called gel electrolyte, which is pseudo-solidified with a polymer or filler. Nonaqueous electrolyte secondary batteries will be described below.

[0107] <2-1. Nonaqueous electrolyte secondary battery> <2-1-1. Battery configuration> A nonaqueous electrolyte secondary battery has the same configuration as conventionally known nonaqueous electrolyte secondary batteries except for the nonaqueous electrolyte, and typically has a configuration in which a positive electrode and a negative electrode are stacked via a porous membrane (separator) impregnated with a nonaqueous electrolyte, and these are housed in a case (exterior body). Therefore, the shape of the nonaqueous electrolyte secondary battery is not particularly limited, and may be any of a cylindrical type, a prismatic type, a laminate type, a coin type, a large type, etc.

[0108] <2-1-2. Non-aqueous electrolyte> As the nonaqueous electrolyte solution, the above-mentioned nonaqueous electrolyte solution is used. Note that, within the scope of the present embodiment, other nonaqueous electrolyte solutions may be mixed with the above-mentioned nonaqueous electrolyte solution.

[0109] <2-1-3. Negative electrode> The negative electrode active material used in the negative electrode is not particularly limited as long as it can electrochemically absorb and release metal ions. Specific examples include carbon-based materials, metal compound-based materials, and lithium-containing metal composite oxide materials. The negative electrode active material may be used alone or in any combination of two or more. Among these, carbonaceous materials and metal compound materials are preferred. Among metal compound materials, silicon-containing materials are preferred. Therefore, carbonaceous materials and silicon-containing materials are particularly preferred as negative electrode active materials.

[0110] <2-1-3-1. Carbon-based materials> The carbonaceous material used as the negative electrode active material is not particularly limited, but is preferably selected from the following (i) to (iv) because it provides a secondary battery with a good balance between initial irreversible capacity and high current density charge / discharge characteristics. (i) Natural graphite (ii) Carbonaceous materials obtained by heat treating artificial carbonaceous materials and artificial graphite materials at least once in the range of 400°C to 3200°C (iii) A carbonaceous material in which the negative electrode active material layer is made of at least two types of carbonaceous materials having different crystallinity and / or has an interface where the carbonaceous materials having different crystallinity are in contact with each other. (iv) A carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two different orientations and / or has an interface where the carbonaceous materials having different orientations are in contact with each other. The carbonaceous materials (i) to (iv) may be used singly or in any combination of two or more in any ratio.

[0111] Specific examples of the artificial carbonaceous material or artificial graphite material in (ii) above include coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, and those obtained by oxidizing these or natural graphite; Needle coke, pitch coke, and partially graphitized carbon materials; Pyrolysis products of organic substances such as furnace black, acetylene black, and pitch-based carbon fiber; Carbonizable organic substances and their carbonized products; and Examples include carbonized solutions of carbonizable organic materials dissolved in low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane;

[0112] The carbonaceous materials (i) to (iv) above are all well known, and their manufacturing methods are well known to those skilled in the art. These materials are also commercially available.

[0113] <2-1-3-2. Metal compound materials> The metal compound material used as the negative electrode active material is not particularly limited as long as it contains a metal capable of alloying with lithium. The form of the metal compound is not particularly limited as long as it is capable of absorbing and releasing metal ions, e.g., lithium ions. Examples of usable metal compound materials include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, and Zn. Materials containing metals and metalloid elements (i.e., excluding carbon; hereinafter, metals and metalloids are collectively referred to as "metals") from Group 13 or 14 of the periodic table are particularly preferred, and silicon (Si), tin (Sn), or lead (Pb) (hereinafter, these three elements may be referred to as "SSP metal elements"), alloys containing these atoms, or compounds of these metals (SSP metal elements) are particularly preferred. The most preferred metal that can be alloyed with lithium is silicon. These may be used alone or in any combination of two or more in any ratio.

[0114] <2-1-3-3. Lithium-containing metal composite oxide materials> The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can absorb and release lithium, but a lithium-containing composite metal oxide material containing titanium is preferred, and a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as "lithium titanium composite oxide") is particularly preferred. When a lithium titanium composite oxide having a spinel structure is contained in a negative electrode active material for a lithium ion nonaqueous electrolyte secondary battery and used, the output resistance of the secondary battery is significantly reduced, which is particularly preferred.

[0115] Also preferred are lithium-titanium composite oxides in which the lithium or titanium is substituted with another metal element, for example, at least one element selected from the group consisting of Na, K, Co, Al, Fe, Mg, Cr, Ga, Cu, Zn, and Nb.

[0116] A lithium titanium composite oxide preferred as the negative electrode active material is represented by the following general formula (2). Li x Ti y M z O4(2) (In general formula (2), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Mg, Cr, Ga, Cu, Zn, and Nb. In addition, in general formula (2), it is preferable that 0.7≦x≦1.5, 1.5≦y≦2.3, and 0≦z≦1.6, since the structure is stable during doping and dedoping of lithium ions.)

[0117] <2-1-3-4. Negative electrode structure, properties, and preparation method> The negative electrode containing the above-mentioned active material, the electrode fabrication method, and the current collector can adopt known technical configurations, but it is desirable that one or more of the following items (I) to (VI) be satisfied simultaneously.

[0118] (I) Preparation of negative electrode The negative electrode can be manufactured by any known method as long as it does not significantly limit the effects of the present invention. For example, a negative electrode can be manufactured by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry-like negative electrode material, applying this to a current collector, drying, and then pressing the current collector to form a negative electrode active material layer.

[0119] (II) 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. When the current collector is made of a metal material, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, or a foamed metal. Among these, a metal thin film or a metal foil is preferred. Copper foil is more preferred, and rolled copper foil produced by a rolling method and electrolytic copper foil produced by an electrolytic method are even more preferred.

[0120] (III) Thickness ratio of current collector to negative electrode active material layer The thickness ratio between the current collector and the negative electrode active material layer is not particularly limited, but the value of "(thickness of the negative electrode active material layer on one side immediately before the non-aqueous electrolyte solution injection step) / (thickness of the current collector)" is preferably 150 or less, more preferably 20 or less, and particularly preferably 10 or less, and is preferably 0.1 or more, more preferably 0.4 or more, and particularly preferably 1 or more. If the thickness ratio of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge of the secondary battery, whereas if it is below the above range, the volume ratio of the current collector to the negative electrode active material increases, which may reduce the capacity of the secondary battery.

[0121] (IV) Electrode density The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, and the density of the negative electrode active material present on the current collector is 1 g cm -3 More than 1.2 g cm is preferable. -3 More than 1.3 g cm is preferable. -3 More than 4g cm is more preferable. -3 Less than 3 g cm is preferred -3 Less than 2.5 g cm is preferable. -3 Less than 1.7 g cm is more preferable. -3The following is particularly preferred. When the density of the negative electrode active material present on the current collector is within the above range, the negative electrode active material particles are less likely to be destroyed, making it easier to prevent an increase in the initial irreversible capacity of the secondary battery and deterioration of high current density charge / discharge characteristics due to reduced permeability of the nonaqueous electrolyte solution near the current collector / negative electrode active material interface. Furthermore, conductivity between the negative electrode active materials can be ensured, and capacity per unit volume can be increased without increasing battery resistance.

[0122] (V) Binders, solvents, etc. The slurry for forming the negative electrode active material layer is usually prepared by adding a mixture of a solvent, a binder, a thickener, etc. to the negative electrode active material. The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable to the non-aqueous electrolyte solution and the solvent used in producing the electrode.

[0123] Specific examples thereof include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; Rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber; Thermoplastic elastomeric polymers such as styrene-butadiene-styrene block copolymers or hydrogenated products thereof, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymers, styrene-isoprene-styrene block copolymers or hydrogenated products thereof; Soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, and tetrafluoroethylene-ethylene copolymers; A polymer composition having ionic conductivity for alkali metal ions (especially lithium ions); etc. These may be used alone or in any combination of two or more in any ratio.

[0124] The solvent for forming the slurry is not particularly limited as long as it is capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as needed, and either an aqueous solvent or an organic solvent may be used.

[0125] Examples of the aqueous solvent include water and alcohol, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, and hexane. In particular, when an aqueous solvent is used, it is preferable to add a dispersant and the like together with the thickener, and form a slurry using a latex such as SBR. These solvents may be used alone or in any combination of two or more in any ratio.

[0126] The ratio of the binder to 100 parts by mass of the negative electrode active material is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.6 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less. When the ratio of the binder to the negative electrode active material is within the above range, the proportion of the binder that does not contribute to the battery capacity is not increased, so that a decrease in battery capacity is unlikely to occur. Furthermore, a decrease in the strength of the negative electrode is unlikely to occur.

[0127] In particular, when the slurry that is the negative electrode forming material contains a rubber-like polymer typified by SBR as a main component, the ratio of the binder to 100 parts by mass of the negative electrode active material is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.6 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less.

[0128] Furthermore, when the slurry contains a fluorine-based polymer typified by polyvinylidene fluoride as a main component, the ratio of the binder to 100 parts by mass of the negative electrode active material is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less.

[0129] Thickeners are usually used to adjust the viscosity of the slurry. There are no particular limitations on the thickener, but specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used alone or in any combination and ratio of two or more.

[0130] When a thickener is used, the ratio of the thickener to 100 parts by mass of the negative electrode active material is typically 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 0.6 parts by mass or more. Furthermore, the ratio is typically 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less. When the ratio of the thickener to the negative electrode active material is within the above range, the coating properties of the slurry are improved. Furthermore, the ratio of the negative electrode active material in the negative electrode active material layer is also appropriate, making it less likely that problems such as a decrease in battery capacity or an increase in resistance between the negative electrode active materials will occur.

[0131] (VI) Area of ​​negative electrode plate The area of ​​the negative electrode (also referred to as "negative electrode plate") is not particularly limited, but is preferably designed to be slightly larger than the opposing positive electrode (also referred to as "positive electrode plate") so that the positive electrode plate does not protrude beyond the negative electrode plate. Furthermore, from the viewpoint of suppressing the cycle life of the secondary battery when repeatedly charged and discharged and deterioration due to high-temperature storage, it is preferable to make the area as close as possible to the positive electrode, since this increases the proportion of electrodes that work more uniformly and effectively, improving characteristics. In particular, when the secondary battery is used at a large current, the design of the area of ​​this negative electrode plate is important.

[0132] <2-1-4. Positive electrode> The positive electrode used in the non-aqueous electrolyte secondary battery will be described below.

[0133] <2-1-4-1. Positive electrode active material> The positive electrode active material used in the positive electrode will be described below.

[0134] (1) Composition The positive electrode active material is not particularly limited as long as it can electrochemically absorb and release metal ions, but for example, it is preferably a material that can electrochemically absorb and release lithium ions, and is preferably a material containing lithium and at least one transition metal. Specific examples include lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, lithium-containing transition metal silicate compounds, and lithium-containing transition metal borate compounds.

[0135] The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples of the lithium transition metal composite oxide include lithium-cobalt composite oxides such as LiCoO2; lithium-nickel composite oxides such as LiNiO2; lithium-manganese composite oxides such as LiMnO2, LiMn2O4, and Li2MnO4; and lithium transition metal composite oxides in which a portion of the transition metal atoms that constitute the main components of these lithium transition metal composite oxides have been substituted with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W.

[0136] Specific examples of the substituted groups include LiNi 0.5 Mn 0.5 O2, LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiMn 1.8 Al 0.2 O4, Li 1.1 Mn 1.9 Al 0.1 O4, LiMn 1.5 Ni 0.5 Examples include O4. Among these, a lithium transition metal composite oxide containing lithium, nickel, and cobalt is more preferred, because a lithium transition metal composite oxide containing cobalt and nickel can provide a large capacity when used at the same potential.

[0137] On the other hand, cobalt is a scarce and expensive metal, and large batteries requiring high capacity, such as those for automobiles, require a large amount of active material, making them undesirable from a cost perspective. Therefore, it is desirable to use manganese as the main component, which is a cheaper transition metal. In other words, lithium-nickel-cobalt-manganese composite oxide is particularly preferable.

[0138] In addition, considering the stability of the compound and the procurement cost due to the ease of production, lithium-manganese composite oxides having a spinel structure and lithium-manganese composite oxides in which a portion of the manganese is substituted are also preferred. 1.8 Al 0.2 O4, Li 1.1 Mn 1.9 Al 0.1 O4, LiMn 1.5 Ni 0.5 O4 and the like can also be mentioned as preferred specific examples.

[0139] The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples of the lithium-containing transition metal phosphate compound include iron phosphates such as LiFePO4, Li3Fe2(PO4)3, and LiFeP2O7; cobalt phosphates such as LiCoPO4; manganese phosphates such as LiMnPO4; and lithium-containing transition metal phosphate compounds in which a portion of the transition metal atoms that constitute the main components of these compounds have been substituted with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. Among these, iron phosphates (lithium iron phosphate compounds) are preferred because iron is an abundant, inexpensive metal and has little toxicity. That is, among the above specific examples, LiFePO4 can be cited as a more preferred specific example.

[0140] The transition metal of the lithium-containing transition metal silicate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples of the lithium-containing transition metal silicate compound include iron silicates such as LiFeSiO; cobalt silicates such as LiCoSiO; and lithium-containing transition metal silicate compounds in which a portion of the transition metal atoms that constitute the main components of these compounds have been substituted with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc.

[0141] The transition metal of the lithium-containing transition metal borate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples of the lithium-containing transition metal borate compound include iron borates such as LiFeBO3; cobalt borates such as LiCoBO3; and lithium-containing transition metal borate compounds in which a portion of the transition metal atoms that constitute the main components of these compounds have been substituted with other metals such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc.

[0142] As the positive electrode active material contained in the positive electrode used in the nonaqueous electrolyte secondary battery, a lithium transition metal composite oxide represented by composition formula (14) is preferred in terms of positive electrode capacity. Li a1 Ni b1 Co c1 M d1 O2···(14) (In formula (14), a1, b1, c1, and d1 represent numerical values ​​of 0.90≦a1≦1.10, 0.50≦b1≦0.98, 0.01≦c1<0.50, and 0.01≦d1<0.50, respectively, and satisfy b1+c1+d1=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

[0143] A preferred example of the lithium transition metal composite oxide represented by the composition formula (14) is LiNi 0.85 Co 0.10 Al 0.05 O2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.50 Mn 0.29 Co 0.21 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 Examples include O2.

[0144] From the viewpoint of improving electrochemical stability and extending battery life, among the transition metal composite oxides represented by composition formula (14), the transition metal composite oxide represented by the following composition formula (15) is more preferred. Li a2 Ni b2 Co c2 M d2 O2···(15) (In formula (15), a2, b2, c2, and d2 represent numerical values ​​within the range of 0.90≦a2≦1.10, 0.50≦b2≦0.90, 0.05≦c2≦0.30, and 0.05≦d2≦0.30, respectively, and satisfy the relationship of b2+c2+d2=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

[0145] Of the transition metal composite oxides represented by composition formula (14), those represented by the following composition formula (16) are more preferred, from the viewpoint that the chemical stability is improved and phase transition due to side reactions on the oxide surface is suppressed, and therefore the interaction between the chain sulfonate ester and the poorly soluble composite coating made of a fluorosulfonate, a monofluorophosphate, a difluorophosphate, an imide salt, or an oxalate is not inhibited. Li a3 Ni b3 Co c3 M d3 O2···(16) (In formula (16), a3, b3, c3, and d3 represent numerical values ​​of 0.90≦a3≦1.10, 0.50≦b3≦0.90, 0.10≦c3≦0.30, and 0.10≦d3≦0.30, respectively, and satisfy b3+c3+d3=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

[0146] A preferred example of the lithium transition metal oxide represented by the composition formula (16) is LiNi 0.5 Co 0.2 Mn 0.3 O2, Li 1.05 Ni 0.50 Mn 0.29 Co 0.21 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 Examples include O2. Of the transition metal composite oxides represented by composition formula (14), the transition metal composite oxide represented by the following composition formula (17) is particularly preferred from the viewpoint of excellent positive electrode capacity and electrochemical and chemical stability. Li a4 Ni b4 Co c4 M d4 O2···(17) (In formula (17), a4, b4, c4, and d4 represent numerical values ​​of 0.90≦a4≦1.10, 0.55≦b4≦0.90, 0.10≦c4≦0.30, and 0.10≦d4≦0.30, respectively, and satisfy b4+c4+d4=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

[0147] In the composition formulas (14) to (17), M preferably contains Mn or Al, and M is preferably Mn or Al. This is because the structural stability of the transition metal composite oxide is improved and structural deterioration during repeated charge and discharge is suppressed. Among these, M is more preferably Mn.

[0148] Two or more of the above positive electrode active materials may be mixed and used. Similarly, at least one of the above positive electrode active materials may be mixed and used with another positive electrode active material. Examples of the other positive electrode active material include transition metal oxides, transition metal phosphate compounds, transition metal silicate compounds, and transition metal borate compounds not listed above.

[0149] When two or more positive electrode active materials are used in combination, the above-mentioned lithium-manganese composite oxide having a spinel structure or the lithium-containing transition metal phosphate compound having an olivine structure is preferred. The transition metal of the lithium-containing transition metal phosphate compound may be any of those mentioned above, and the preferred embodiments are also the same.

[0150] (2) Manufacturing method of positive electrode active material The method for producing the positive electrode active material is not particularly limited as long as it does not deviate from the gist of the invention according to this embodiment, but several methods can be mentioned, and a general method for producing an inorganic compound can be used. In particular, various methods can be considered for producing spherical or oval-spherical active materials. One example is a method in which a transition metal raw material such as a transition metal nitrate or sulfate, and optionally raw materials of other elements, are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is then dried as necessary, and a Li source such as LiOH, Li2CO3, or LiNO3 is added and the mixture is fired at a high temperature to obtain a positive electrode active material.

[0151] Another example of such a method is to dissolve or pulverize and disperse a transition metal raw material such as a transition metal nitrate, sulfate, hydroxide, or oxide, and, if necessary, raw materials of other elements, in a solvent such as water, and then dry and mold the resulting mixture using a spray dryer or the like to form a spherical or ellipsoidal precursor, to which a Li source such as LiOH, Li2CO3, or LiNO3 is added and calcined at a high temperature to obtain a positive electrode active material.

[0152] Yet another example of such a method is to dissolve or pulverize and disperse a transition metal raw material such as a transition metal nitrate, sulfate, hydroxide, or oxide, a Li source such as LiOH, Li2CO3, or LiNO3, and, if necessary, raw materials of other elements, in a solvent such as water, and then dry and mold the resulting mixture using a spray dryer or the like to form a spherical or oval-spherical precursor, which is then calcined at a high temperature to obtain a positive electrode active material.

[0153] <2-1-4-2. Positive electrode structure and manufacturing method> The structure of the positive electrode and the method for producing it will be described below.

[0154] (Positive electrode manufacturing method) The positive electrode using the positive electrode active material can be produced by any known method. The positive electrode is usually produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. More specifically, for example, the positive electrode active material and the binder, and optionally a conductive material and a thickener, etc. 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 to form a slurry, which is applied to the positive electrode current collector and dried, thereby forming a positive electrode active material layer on the current collector, thereby obtaining a positive electrode.

[0155] The content of the positive electrode active material in the positive electrode active material layer is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 99.9% by mass or less, more preferably 99% by mass or less. When the content of the positive electrode active material is within the above range, the electric capacity of the nonaqueous electrolyte secondary battery can be sufficiently ensured. Furthermore, the strength of the positive electrode is also sufficient. The positive electrode active material powder may be used singly, or two or more types with different compositions or different powder properties may be used in any combination and ratio. When two or more active materials are used in combination, it is preferable to use the composite oxide containing lithium and manganese as a powder component. As mentioned above, cobalt and nickel are expensive metals with limited resources. Therefore, large batteries requiring high capacity, such as those for automotive applications, require a large amount of active material, which is undesirable from a cost perspective. Therefore, it is desirable to use manganese as a cheaper transition metal as the main component.

[0156] (Conductive material) 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. These materials may be used alone or in any combination and ratio of two or more.

[0157] The content of the conductive material in the positive electrode active material layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, and is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 15% by mass or less. When the content of the conductive material is within the above range, sufficient conductivity can be ensured. Furthermore, a decrease in battery capacity can also be easily prevented.

[0158] (binder) The binder used in producing the positive electrode active material layer is not particularly limited as long as it is a material that is stable to the non-aqueous electrolyte solution and the solvent used in producing the electrode.

[0159] When the positive electrode is produced by the coating method, the binder is not particularly limited as long as it is a material that can be dissolved or dispersed in the liquid medium used in producing the electrode. Specific examples thereof include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; Rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; Thermoplastic elastomeric polymers such as styrene-butadiene-styrene block copolymers or hydrogenated products thereof, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers or hydrogenated products thereof; Soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer; Fluoropolymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and tetrafluoroethylene-ethylene copolymers; Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions); and the like. The binder may be used alone or in any combination of two or more kinds in any ratio.

[0160] The binder content in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 40% by mass or less, and particularly preferably 10% by mass or less. When the binder content is within the above range, the positive electrode active material can be sufficiently retained and the mechanical strength of the positive electrode can be ensured, resulting in good battery performance such as cycle characteristics. Furthermore, this also helps to avoid a decrease in battery capacity and conductivity.

[0161] (liquid medium) The liquid medium used to prepare the slurry for forming the positive electrode active material layer is not particularly limited in type, and either an aqueous solvent or an organic solvent may be used, as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the binder, and the thickener used as needed.

[0162] Examples of the aqueous solvent include water, a mixture of alcohol and water, etc. Examples of the organic solvent include aliphatic hydrocarbons such as hexane; Aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; Heterocyclic compounds such as quinoline and pyridine; Ketones such as acetone, methyl ethyl ketone, and cyclohexanone; Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); Amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphamide and dimethyl sulfoxide; The following can be mentioned: These may be used alone or in any combination of two or more in any ratio.

[0163] (thickener) When using an aqueous medium as the liquid medium for forming the slurry, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) to form the slurry. The thickener is usually used to adjust the viscosity of the slurry.

[0164] There are no limitations on the thickener as long as it does not significantly limit the effects of the present invention, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used alone or in any combination and ratio of two or more.

[0165] When a thickener is used, the proportion of the thickener relative to the total mass of the positive electrode active material and the thickener is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.6% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. When the proportion of the thickener is within the above range, the coating properties of the slurry are good, and furthermore, the proportion of the active material in the positive electrode active material layer is sufficient, making it easier to avoid problems such as a decrease in the capacity of the secondary battery and an increase in resistance between the positive electrode active materials.

[0166] (Consolidation) The positive electrode active material layer obtained by applying the above slurry to the current collector and drying it is preferably compacted using a hand press, roller press, or the like to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is 1 g cm -3 More than 1.5g cm is preferable. -3 More than 2g cm is more preferable. -3 Above 4g cm is particularly preferable. -3 Less than 3.5 g cm is preferred -3 Less than 3g cm is more preferable. -3 The following are particularly preferred: When the density of the positive electrode active material layer is within the above range, the permeability of the nonaqueous electrolyte solution near the current collector / active material interface is not reduced, and the charge / discharge characteristics of the secondary battery, particularly at high current densities, are improved. Furthermore, the conductivity between the active materials is less likely to decrease, and the battery resistance is less likely to increase.

[0167] (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; and carbon-based materials such as carbon cloth and carbon paper. Among these, metal materials, especially aluminum, are preferred.

[0168] The shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, or a foamed metal, for a metal material, or a carbon plate, a carbon thin film, or a carbon cylinder, for example. Of these, a metal foil or a metal thin film is preferred. The metal foil or thin film may be formed into a mesh as appropriate.

[0169] The thickness of the current collector is optional, but is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, and is preferably 1 mm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. When the thickness of the current collector is within the above range, the strength required as a current collector can be sufficiently ensured. Furthermore, handling is also improved.

[0170] The thickness ratio between the current collector and the positive electrode active material layer is not particularly limited, but (thickness of the active material layer on one side immediately before the injection of the nonaqueous electrolyte solution) / (thickness of the current collector) is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, and is also preferably 0.1 or more, more preferably 0.4 or more, particularly preferably 1 or more. When the thickness ratio of the current collector to the positive electrode active material layer is within the above range, the current collector is less likely to generate heat due to Joule heat during high current density charge / discharge of the secondary battery, and the volume ratio of the current collector to the positive electrode active material is less likely to increase, thereby preventing a decrease in battery capacity.

[0171] (electrode area) From the viewpoint of enhancing high output and stability at high temperatures, the area of ​​the positive electrode active material layer is preferably larger than the outer surface area of ​​the battery outer case. Specifically, the total electrode area of ​​the positive electrode relative to the surface area of ​​the outer case of the nonaqueous electrolyte secondary battery is preferably 20 times or more, more preferably 40 times or more, in terms of area ratio. In the case of a rectangular outer case with a bottom, the outer surface area refers to the total area calculated from the length, width, and thickness of the case portion filled with the power generating elements, excluding the terminal protrusions. In the case of a cylindrical outer case with a bottom, the outer surface area refers to the geometric surface area of ​​the case portion filled with the power generating elements, excluding the terminal protrusions, approximated as a cylinder. The total electrode area of ​​the positive electrode refers to the geometric surface area of ​​the positive electrode composite layer facing the composite layer containing the negative electrode active material. In a structure in which positive electrode composite layers are formed on both sides via a current collector foil, the total area refers to the sum of the areas calculated separately for each side.

[0172] (discharge capacity) When a non-aqueous electrolyte is used, it is preferable that the electric capacity of the battery element housed in one battery exterior of the non-aqueous electrolyte secondary battery (the electric capacity when the battery is discharged from a fully charged state to a discharged state) is 1 ampere-hour (Ah) or more, since this greatly improves the low-temperature discharge characteristics. Therefore, the positive electrode plate is designed so that the discharge capacity at full charge is preferably 3 Ah (ampere-hour) or more, more preferably 4 Ah or more, and preferably 20 Ah or less, more preferably 10 Ah or less. Within the above range, the voltage drop due to electrode reaction resistance during large current draw is prevented from becoming too large, preventing a deterioration in power efficiency. Furthermore, the temperature distribution due to internal heat generation during pulse charge / discharge is prevented from becoming too large, avoiding phenomena such as poor durability during repeated charge / discharge and poor heat dissipation efficiency in response to sudden heat generation during abnormalities such as overcharging or internal short circuit.

[0173] (Positive electrode thickness) The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, 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 preferably 10 μm or more, more preferably 20 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less, on one side of the current collector.

[0174] <2-1-5. Separator> In non-aqueous electrolyte secondary batteries, 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.

[0175] The separator is not particularly limited in material or shape, and any known material may be used as long as it does not significantly impair the effects of the present invention. Among these, it is preferable to use a material that is stable against a non-aqueous electrolyte solution, such as a resin, glass fiber, or inorganic material, and that is in the form of a porous sheet or nonwoven fabric with excellent liquid retention.

[0176] <2-1-6.Battery design> (electrode group) The electrode group may have either a laminated structure formed by sandwiching the positive and negative electrode plates with the separator therebetween, or a structure formed by spirally winding the positive and negative electrode plates with the separator therebetween. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is preferably 40% or more, more preferably 50% or more, and is preferably 95% or less, more preferably 90% or less. When the electrode group occupancy rate is within the above range, the battery capacity is less likely to decrease. In addition, since an appropriate amount of void space can be secured, it is possible to prevent the battery from becoming hot and causing components to expand or the vapor pressure of the nonaqueous electrolyte components to increase, resulting in an increase in internal pressure and a decrease in various characteristics of the secondary battery, such as the charge / discharge cycle performance and high-temperature storage characteristics, as well as the activation of a gas release valve that releases internal pressure.

[0177] (current collection structure) Although the current collection structure is not particularly limited, in order to more effectively realize the improvement of discharge characteristics by the non-aqueous electrolyte, it is preferable to use a structure that reduces the resistance of wiring parts and joint parts. When the internal resistance is reduced in this way, the effect of using the non-aqueous electrolyte is particularly well exhibited.

[0178] When the electrode group has the aforementioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to a terminal is preferably used. When the area of ​​a single electrode is large, the internal resistance increases, so it is also preferable to provide multiple terminals within the electrode to reduce the resistance. 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 and negative electrodes and bundling them to a terminal.

[0179] (protective element) Examples of protective elements include PTC (Positive Temperature Coefficient) elements whose resistance increases with heat generation due to excessive current, etc., thermal fuses, thermistors, valves (current cutoff valves) that cut off the current flowing in the circuit due to a sudden rise in the battery's internal pressure or temperature during abnormal heat generation, etc. It is preferable to select protective elements that will not operate under normal high-current use, and it is even more preferable to design a battery that will not experience abnormal heat generation or thermal runaway even without protective elements.

[0180] (exterior body) A non-aqueous electrolyte secondary battery is usually constructed by housing the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator, etc. in an exterior body (exterior case). There are no limitations on this exterior body, and any known exterior body can be used as long as it does not significantly impair the effects of the present invention.

[0181] The material of the outer case is not particularly limited as long as it is stable against the non-aqueous electrolyte solution used. Specifically, metals such as nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, magnesium alloy, nickel, titanium, etc., or a laminate film of resin and aluminum foil (laminate film) are used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloy or laminate film are preferably used. Examples of exterior cases using the above metals include those in which the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed and airtight structure, or those in which the metals are used via a resin gasket to form a crimped structure. Examples of exterior cases using the above laminate film include those in which the resin layers are heat-sealed to form a sealed and airtight structure. In order to improve the sealing properties, a resin different from the resin used in the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed via a current collecting terminal to form a sealed structure, the metal and the resin are joined, so a resin having a polar group or a modified resin into which a polar group has been introduced is preferably used as the interposed resin.

[0182] The shape of the exterior case is also arbitrary, and may be, for example, cylindrical, rectangular, laminated, coin-shaped, large, or the like. [Example]

[0183] The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples as long as it does not depart from the gist of the invention.

[0184] The compounds used in the present examples and comparative examples are shown below.

[0185] [ka] Ethyl methanesulfonate [ka] 1,3-Propane Sultone

[0186] <Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-7> [Examples 1-1 to 1-5] [Preparation of non-aqueous electrolyte] In a dry argon atmosphere, a mixed solvent (mixing volume ratio 2:4:4) consisting of ethylene carbonate (also referred to as "EC"), ethyl methyl carbonate (also referred to as "EMC"), and dimethyl carbonate (also referred to as "DMC") was added with LiPF6 as an electrolyte, vinylene carbonate (also referred to as "VC") as an additive, Compound 1 as a chain lithium sulfonate, and lithium fluorosulfonate (LiFSO3) as a fluorosulfonate salt, adjusted to the concentrations shown in Table 1, to prepare the nonaqueous electrolyte solutions of Examples 1-1 to 1-5. Note that the "content (mass%)" in the table is the content when the entire nonaqueous electrolyte solution is taken as 100 mass%. In Table 1, the "mass ratio" is the mass ratio of the content of the sulfonate ester (Compound 1 or Compound 2) to the lithium fluorosulfonate, and is shown as a ratio when the total content of the sulfonate ester (Compound 1 or Compound 2) and lithium fluorosulfonate is taken as 100. For example, the mass ratio in Example 1-1 was calculated using the following formula. Example 1-1: {1 / (1+0.002)x100} / {0.002 / (1+0.002)x100}=99.80 / 0.20 [Preparation of positive electrode] Lithium cobalt nickel manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 94% by mass of O2, 3% by mass of acetylene black as a conductive material, and 3% by mass of polyvinylidene fluoride (PVdF) as a binder were mixed in N-methylpyrrolidone solvent using a disperser to form a slurry. This was evenly applied to one side of a 15 μm thick aluminum foil, dried, and pressed to form a positive electrode.

[0187] [Preparation of negative electrode] Amorphous coated graphite powder was used as the negative electrode active material, an aqueous dispersion of sodium carboxymethylcellulose (1% by mass of sodium carboxymethylcellulose) was used as a thickener, and an aqueous dispersion of styrene-butadiene rubber (50% by mass of styrene-butadiene rubber) was used as a binder. 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 in the dried negative electrode was 98:1:1.

[0188] [Fabrication of lithium secondary batteries] A battery element was fabricated by stacking the above positive electrode, negative electrode, and polypropylene separator in the following order: negative electrode, separator, positive electrode, separator, negative electrode. 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 fabricate a sheet-shaped lithium secondary battery.

[0189] [Initial conditioning] The lithium secondary battery was sandwiched between glass plates and pressurized. It was then charged at a constant current of 0.05 C for 10 hours at 25°C, and then discharged at a constant current of 0.2 C to 2.8 V. It was then subjected to constant current-constant voltage charging (also known as "CC-CV charging") at a current of 0.2 C (0.05 C cut) to 4.1 V, and then left at 60°C for 24 hours. After allowing the battery to cool sufficiently, it was discharged at a constant current of 0.2 C to 2.8 V. It was then CC-CV charged at 0.2 C to 4.3 V (0.05 C cut), and then discharged again at 0.2 C to 2.8 V to stabilize the initial battery characteristics. 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.

[0190] [Initial discharge resistance evaluation test] The lithium secondary battery that had undergone initial conditioning was CC-CV charged at 0.2 C (cut at 0.05 C) at 25°C to 3.72 V, and then discharged for 10 seconds at a current of 1 C. The resistance was calculated from the difference between the battery voltage before discharge and the voltage immediately after 10 seconds of discharge (10 seconds after discharge began) according to Ohm's law: R (resistance) = V (voltage) ÷ I (current), and this was taken as the initial room temperature discharge resistance. Furthermore, the battery was discharged at a current of 1 C for 10 seconds at -20°C, and the resistance was calculated from the difference between the battery voltage before discharge and the voltage immediately after 10 seconds of discharge according to Ohm's law: R (resistance) = V (voltage) ÷ I (current), and this was used as the initial low-temperature discharge resistance.

[0191] [High temperature storage durability test] The lithium secondary batteries subjected to the initial discharge resistance evaluation test were CC-CV charged at 0.2 C (cut by 0.05 C) at 25°C to 4.3 V, and then stored at high temperature at 60°C for 14 days. After the batteries were thoroughly cooled, they were discharged at a constant current of 0.2 C to 2.8 V at 25°C. Next, they were CC-CV charged at 0.2 C (cut by 0.05 C) to 4.3 V, and then discharged again at 0.2 C to 2.8 V.

[0192] [Discharge resistance evaluation test after high temperature storage] The lithium secondary batteries that underwent the high-temperature storage durability test were CC-CV charged at 0.2 C (cut off at 0.05 C) at 25°C to 3.72 V, and then discharged at a current of 1 C for 10 seconds. Resistance was calculated from the difference between the battery voltage before discharge and the voltage immediately after 10 seconds of discharge according to Ohm's law: R (resistance) = V (voltage) ÷ I (current), and this was defined as the room-temperature discharge resistance after storage. Furthermore, the ratio of the room-temperature discharge resistance after storage to the initial room-temperature discharge resistance (room-temperature discharge resistance after storage ÷ initial room-temperature discharge resistance) was calculated, and this was defined as the room-temperature discharge resistance increase rate (%). The battery was discharged at -20°C for 10 seconds at a current of 1 C, and the resistance was calculated from the difference between the battery voltage before discharge and the voltage immediately after 10 seconds of discharge according to Ohm's law: R (resistance) = V (voltage) ÷ I (current), and this was defined as the low-temperature discharge resistance after storage. Furthermore, the ratio of the low-temperature discharge resistance after storage to the initial low-temperature discharge resistance (low-temperature discharge resistance after storage ÷ initial low-temperature discharge resistance) was calculated, and this was defined as the low-temperature discharge resistance increase rate (%).

[0193] The lithium secondary batteries fabricated above were subjected to the above-mentioned initial conditioning, initial discharge resistance evaluation test, high-temperature storage durability test, and post-high-temperature storage discharge resistance evaluation test. The evaluation results are shown in Table 1 as relative values ​​when Comparative Example 1-1 described below is set to 100.00%. The same applies to Comparative Examples 1-2 to 1-7 below.

[0194] [Comparative Example 1-1] A non-aqueous electrolyte solution of Comparative Example 1-1 was prepared in the same manner as in Example 1-1, except that Compound 1 and lithium fluorosulfonate were not added to the electrolyte solution of Example 1-1. A lithium secondary battery was produced in the same manner as in Example 1-1, except that the non-aqueous electrolyte solution of Comparative Example 1-1 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0195] [Comparative Example 1-2] A nonaqueous electrolyte solution of Comparative Example 1-2 was prepared in the same manner as in Example 1-1, except that Compound 1 was not added to the electrolyte solution of Example 1-1. A lithium secondary battery was produced in the same manner as in Example 1-1, except that the nonaqueous electrolyte solution of Comparative Example 1-2 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0196] [Comparative Example 1-3] A nonaqueous electrolyte solution of Comparative Example 1-3 was prepared in the same manner as in Example 1-2, except that Compound 1 was not added to the electrolyte solution of Example 1-2. A lithium secondary battery was produced in the same manner as in Example 1-2, except that the nonaqueous electrolyte solution of Comparative Example 1-3 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0197] [Comparative Example 1-4] A nonaqueous electrolyte solution of Comparative Example 1-4 was prepared in the same manner as in Example 1-3, except that Compound 1 was not added to the electrolyte solution of Example 1-3. A lithium secondary battery was produced in the same manner as in Example 1-3, except that the nonaqueous electrolyte solution of Comparative Example 1-4 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0198] [Comparative Example 1-5] A non-aqueous electrolyte solution of Comparative Example 1-5 was prepared in the same manner as in Example 1-1, except that lithium fluorosulfonate was not added to the electrolyte solution of Example 1-1. A lithium secondary battery was fabricated in the same manner as in Example 1-1, except that the non-aqueous electrolyte solution of Comparative Example 1-5 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0199] [Comparative Examples 1-6] A nonaqueous electrolyte solution of Comparative Example 1-6 was prepared in the same manner as in Example 1-1, except that in the electrolyte solution of Example 1-1, the content of lithium fluorosulfonate was changed as shown in Table 1. In addition, a lithium secondary battery was produced in the same manner as in Example 1-1, except that the nonaqueous electrolyte solution of Comparative Example 1-6 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0200] [Comparative Example 1-7] A nonaqueous electrolyte solution of Comparative Example 1-7 was prepared in the same manner as in Example 1-3, except that in the electrolyte solution of Example 1-3, compound 2, which is a cyclic sulfonic acid ester, was used instead of compound 1, which is a chain sulfonic acid ester. In addition, a lithium secondary battery was produced in the same manner as in Example 1-3, except that the nonaqueous electrolyte solution of Comparative Example 1-7 was used as the electrolyte solution, and initial conditioning, an initial discharge resistance evaluation test, a high-temperature storage durability test, and a discharge resistance evaluation test after high-temperature storage were performed.

[0201] [Table 1]

[0202] <Examples 2-1 to 2-2, Comparative Examples 2-1 to 2-3> In Example 1-1, the lithium fluorosulfonate was replaced with lithium bis(fluorosulfonyl)imide (LiFSI), and an electrolyte solution was prepared with the contents shown in Table 2 below. Furthermore, a lithium secondary battery was fabricated in the same manner as in Example 1-1, except that the obtained electrolyte solution was used, and the above-mentioned initial conditioning, initial discharge resistance evaluation test, high-temperature storage durability test, and post-high-temperature storage discharge resistance evaluation test were carried out. The evaluation results are shown in Table 2 as relative values ​​when Comparative Example 2-1 is defined as 100.00%. In Table 2, the "mass ratio" refers to the mass ratio of the content of sulfonate ester (compound 1 or compound 2) to the content of lithium bis(fluorosulfonyl)imide, and is expressed as a ratio when the total content of lithium bis(fluorosulfonyl)imide and sulfonate ester (compound 1 or compound 2) is defined as 100.

[0203] [Table 2]

[0204] <Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4> In Example 1-1, the lithium fluorosulfonate salt was replaced with lithium bis(oxalato)borate (LiBOB), and an electrolyte solution was prepared with the contents shown in Table 3 below. A lithium secondary battery was fabricated in the same manner as in Example 1-1, except that the obtained electrolyte solution was used, and the above-mentioned initial conditioning, initial discharge resistance evaluation test, high-temperature storage durability test, and post-high-temperature storage discharge resistance evaluation test were carried out. The evaluation results are shown in Table 3 as relative values ​​when Comparative Example 3-1 is defined as 100.00%. In Table 3, the "mass ratio" refers to the mass ratio of the content of sulfonate ester (compound 1 or compound 2) to the content of lithium bis(oxalato)borate, and is expressed as a ratio when the total content of lithium bis(oxalato)borate and sulfonate ester (compound 1 or compound 2) is defined as 100.

[0205] [Table 3]

[0206] <Examples 4-1 to 4-6, Comparative Examples 4-1 to 4-2> In Example 1-1, the lithium fluorosulfonate salt was changed to lithium difluorophosphate (LiPO2F2), which is a difluorophosphate salt, and an electrolyte solution was prepared so that the content would be as shown in Table 4 below. Except for using the obtained electrolyte solution, a lithium secondary battery was fabricated in the same manner as in Example 1-1, and the above-mentioned initial conditioning, initial discharge resistance evaluation test, high-temperature storage durability test, and post-high-temperature storage discharge resistance evaluation test were performed. The results of the room-temperature discharge resistance increase rate are shown in Table 4 as a relative value when Comparative Example 4-2 is set to 100.00%. In Table 4, the "mass ratio" is the mass ratio of the content of sulfonate ester (compound 1) to the content of lithium difluorophosphate, and is shown as a ratio when the total content of lithium difluorophosphate and sulfonate ester (compound 1) is set to 100.

[0207] [Table 4]

[0208] Tables 1 to 3 show that the use of the nonaqueous electrolyte solutions of Examples 1-1 to 1-5, 2-1 to 2-2, and 3-1 to 3-6 simultaneously suppresses the discharge resistance increase rate of lithium secondary batteries at room temperature and low temperature, compared to cases where both a chain sulfonic acid ester and at least one compound selected from the group consisting of fluorosulfonate, imide salt, and oxalate are not contained (Comparative Examples 1-1, 2-1, and 3-1). Furthermore, in the case of a combination of a chain sulfonic acid ester and a fluorosulfonate, or a combination of a chain sulfonic acid ester and an imide salt, when the fluorosulfonate or imide salt is contained in the nonaqueous electrolyte solution in an amount exceeding a predetermined amount (Comparative Examples 1-6 and 2-2), the effects are insufficient. On the other hand, it was found that the discharge resistance increase rate of the secondary battery at room temperature and low temperature was simultaneously suppressed when an electrolyte solution containing a chain sulfonate ester in the same ratio was used, compared to when the electrolyte solution contained a cyclic sulfonate ester and at least one compound selected from the group consisting of a fluorosulfonate salt, an imide salt, and an oxalate salt (Comparative Examples 1-7, 2-3, and 3-2 to 3-4). In the case of non-aqueous electrolyte solutions containing only fluorosulfonate (Comparative Examples 1-2 to 1-4), the rate of increase in discharge resistance at room temperature and low temperature was higher than in Comparative Example 1-1, indicating that the inclusion of fluorosulfonate increases the rate of increase in discharge resistance at room temperature and low temperature, resulting in insufficient battery performance. Furthermore, in the case of non-aqueous electrolyte solutions containing only chain sulfonate (Comparative Example 1-5), the rate of increase in discharge resistance at low temperature was suppressed, but the improvement effect was small. Furthermore, the rate of increase in discharge resistance at room temperature was higher than in Comparative Example 1-1, indicating insufficient battery performance compared to when chain sulfonate ester was not included. Therefore, it is clear that lithium secondary batteries using non-aqueous electrolyte solutions according to one embodiment of the present invention have superior characteristics.

[0209] From Table 4, it was found that when the nonaqueous electrolyte solutions of Examples 4-1 to 4-6 were used, the discharge resistance increase rate of the lithium secondary battery at room temperature was suppressed compared to when neither the chain sulfonic acid ester nor lithium difluorophosphate was contained (Comparative Example 4-2). It was also found that when the mass ratio of the chain sulfonic acid ester to the difluorophosphate was relatively high, the effect was insufficient (Comparative Example 4-1). Therefore, it is clear that the lithium secondary battery using the nonaqueous electrolyte solution according to one embodiment of the present invention has superior characteristics.

[0210] In the examples and comparative examples shown in Tables 1 to 4, the various durability tests were conducted for relatively short periods as a model, but significant differences were observed. Since actual nonaqueous 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.

[0211] This application is based on a Japanese patent application (Patent Application No. 2019-226955) filed on December 17, 2019, the contents of which are incorporated herein by reference.

Claims

1. A non-aqueous electrolyte solution for an energy device having a positive electrode and a negative electrode, The non-aqueous electrolytic solution, together with an electrolyte and a non-aqueous solvent, 1. A nonaqueous electrolyte solution comprising a chain sulfonic acid ester represented by formula (1) and at least one fluorophosphate selected from monofluorophosphates and difluorophosphates, wherein the mass ratio of the content of the chain sulfonic acid ester represented by formula (1) to the content of the fluorophosphate is 10 / 90 or more and 82 / 18 or less. 【Chemistry 1】 (In formula (1), R １ represents an aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms which may be substituted with halogen; R ２ represents an aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms which may be substituted with halogen.

2. A non-aqueous electrolyte solution for an energy device having a positive electrode and a negative electrode, The non-aqueous electrolytic solution, together with an electrolyte and a non-aqueous solvent, (A) a chain sulfonic acid ester represented by formula (1) and at least one compound selected from the group consisting of a fluorosulfonic acid salt and an imide salt, (B) The total content of at least one compound selected from the group consisting of fluorosulfonates and imide salts is 1.0 × 10 based on 100 mass% of the nonaqueous electrolyte solution. －３ % by mass or more and 7% by mass or less, and (C) at least one compound selected from the group consisting of fluorosulfonate salts and imide salts; a mass ratio of the content of the compound to the content of the chain sulfonic acid ester represented by formula (1) being 10 / 90 or more and 99.99 / 0.01 or less. 【Chemistry 2】 (In formula (1), R １ represents an aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms, and R ２ represents an aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms which may be substituted with halogen.

3. In the formula (1), R １ represents a linear aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms, and R ２ The nonaqueous electrolyte solution according to claim 1 or 2, wherein represents a linear aliphatic saturated hydrocarbon group having 1 to 5 carbon atoms.

4. The nonaqueous electrolyte solution according to any one of claims 1 to 3, 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.

5. An energy device comprising a positive electrode, a negative electrode, and the nonaqueous electrolyte solution according to any one of claims 1 to 4.

6. 6. The energy device according to claim 5, wherein the positive electrode comprises a positive electrode active material, and the positive electrode active material is a lithium transition metal composite oxide represented by composition formula (14): Li ａ１ Ni ｂ１ Co ｃ１ M ｄ１ O ２ ・・・(14) (In formula (14), a1, b1, c1, and d1 represent numerical values ​​within the ranges 0.90≦a1≦1.10, 0.50≦b1≦0.98, 0.01≦c1<0.50, and 0.01≦d1<0.50, respectively, and satisfy b1+c1+d1=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

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