Non-aqueous electrolyte and non-aqueous electrolyte secondary cell

Abstract

Provided are a non-aqueous electrolyte and a non-aqueous electrolyte secondary cell containing a carbodiimide compound represented by formula (I) and a disulfonic acid ester compound represented by a specific formula. [In formula (I), each of R11 independently represents a hydrocarbon group having 1-12 carbon atoms or a trialkylsilyl group having 3-18 carbon atoms.]

Description

Non-aqueous electrolyte and non-aqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery.

[0002] In recent years, power storage devices such as lithium-ion secondary batteries, which are small, lightweight, and have high output, have become increasingly sophisticated. As a result, these batteries are increasingly being used not only in small electrical appliances but also in large products such as automobiles. Lithium-ion secondary batteries are required to meet specific requirements for various characteristics, such as output characteristics, charge / discharge characteristics, and gas generation. For example, a small decrease in output power when stored for a long period of time in a high-temperature environment is also a very important evaluation item. Patent Document 1 discloses a nonaqueous electrolyte containing lithium trifluoromethanesulfonate (TFMSLi), lithium difluorophosphate (LiDFP), and lithium bis(oxalato)borate (LiBOB), and reports that the use of this nonaqueous electrolyte reduces the resistance at −10° C. after storage at 60° C. for five days.

[0003] Lithium-ion secondary batteries are required to satisfy specific requirements for various characteristics, such as output power, charge / discharge power, and gas generation. Another important evaluation item is low battery resistance and sufficient output power in low-temperature environments, such as at −20°C. Meanwhile, with regard to positive electrode materials for lithium-ion secondary batteries and the like, so-called “high-Ni” materials have recently been attracting increasing attention from the perspective of achieving higher capacity, and research into nickel-cobalt-manganese oxide and nickel-cobalt-aluminum oxide (NCA) with high Ni content is progressing. For example, Patent Document 2 describes a nonaqueous electrolyte secondary battery that uses a lithium transition metal compound with a Ni / (Ni+Mn+Co) molar ratio of 0.45 or higher as the positive electrode active material, in which a monofluorophosphate, difluorophosphate, or the like is blended into the nonaqueous electrolyte.

[0004] International Publication No. WO 2018 / 181369 International Publication No. WO 2019 / 031508

[0005] There are cases where conventional nonaqueous electrolytes for batteries and nonaqueous electrolyte secondary batteries are required to have a further reduction in battery resistance after storage. Therefore, an object of a first aspect of the present disclosure is to provide a nonaqueous electrolyte that can suppress an increase in resistance after high-temperature storage of a lithium-ion secondary battery. Also, an object of a second aspect of the present disclosure is to provide a nonaqueous electrolyte that can be used in a nonaqueous electrolyte secondary battery that uses a nickel-containing lithium composite oxide as a positive electrode active material and that can suppress battery resistance, particularly initial battery resistance, and a nonaqueous electrolyte secondary battery that includes the nonaqueous electrolyte.

[0006] Means for solving the problems of the first aspect of the present disclosure include the following aspects.

[0007] <1> A nonaqueous electrolyte solution containing a carbodiimide compound represented by the following formula (I) and a disulfonic acid ester compound represented by the following formula (II-1) or (II-2).

[0008] [In formula (I), R １１ each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.

[0009] [In formulas (II-1) and (II-2), R ２１ and R ２２ each independently represents a substituent selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of ２３ each independently represents a substituent selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２) represents a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of: <2> The nonaqueous electrolyte solution according to <1>, wherein the content of the carbodiimide compound is 0.001% by mass to 5.0% by mass, based on the total amount of the nonaqueous electrolyte solution. <3> The nonaqueous electrolyte solution according to <1> or <2>, wherein the content of the disulfonic acid ester compound is 0.01% by mass to 5.0% by mass, based on the total amount of the nonaqueous electrolyte solution. <4> The nonaqueous electrolyte solution according to any one of <1> to <3>, further comprising a cyclic sulfate ester compound represented by the following formula (III):

[0010] [In formula (III), R ３１ are each independently a group represented by formula (iii-1), a group represented by formula (iii-2), a hydrogen atom (—H), or a substituent selected from the group consisting of a fluoro group (—F), a chloro group (—Cl), a bromo group (—Br), an oxa group (—O—), a carbonyl group (>C═O), and a sulfonyl group (>S(═O) ２ R represents a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of ３２ is a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and as a substituent, a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ a hydrocarbon group having 1 to 12 carbon atoms, a fluorocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a group represented by formula (iii-3), which may contain at least one functional group selected from the group consisting of: <5> The nonaqueous electrolyte solution according to <4>, wherein the content of the cyclic sulfate ester compound is 0.01% by mass to 5.0% by mass with respect to the total amount of the nonaqueous electrolyte solution. <6> A nonaqueous electrolyte solution containing a carbodiimide compound represented by the following formula (I-2):

[0011] [In formula (I-2), R １２ each independently represents a hydrocarbon group having 1 to 6 carbon atoms.

[0012] Furthermore, as a result of extensive research into solving the problems of the second aspect of the present disclosure, the present inventors have found that by blending a specific carbodiimide compound with the nonaqueous electrolyte of a nonaqueous electrolyte secondary battery containing a nickel-containing lithium composite oxide as a positive electrode active material, it is possible to reduce battery resistance, particularly initial battery resistance, and have completed the present disclosure.

[0013] That is, the means for solving the problem of the second aspect of the present disclosure include the following aspects.

[0014] <7> A nonaqueous electrolyte used in a nonaqueous electrolyte secondary battery containing a nickel-containing lithium composite oxide as a positive electrode active material, the nonaqueous electrolyte containing a carbodiimide compound represented by the following formula (I):

[0015] [In formula (I), R １１ each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.] <8> The nonaqueous electrolyte solution according to <7>, wherein the total content of the carbodiimide compounds represented by formula (I) is 0.001% by mass to 5.0% by mass, based on the total amount of the nonaqueous electrolyte solution. <9> The nonaqueous electrolyte solution according to <7>, wherein the total content of the carbodiimide compounds represented by formula (I) is 0.001% by mass to 0.5% by mass, based on the total amount of the nonaqueous electrolyte solution. <10> The nonaqueous electrolyte solution according to <7>, wherein the total content of the carbodiimide compounds represented by formula (I) is 0.001% by mass to 0.2% by mass, based on the total amount of the nonaqueous electrolyte solution. <11> The nonaqueous electrolyte solution according to any one of <7> to <10>, wherein the nickel-containing lithium composite oxide is a composite oxide represented by the following formula (IV): Li ｘ Ni ｙ M ｚ O ２ ... (IV) (In formula (IV), M represents at least one atom selected from the group consisting of Co, Mn, and Al, x is a numerical value satisfying 0.95≦x≦1.15, and y and z are numerical values ​​satisfying 0.4≦y<1.0 and y+z=1.) <12> The nonaqueous electrolyte solution according to any one of <7> to <11>, further containing a cyclic carbonate compound represented by the following formula (V):

[0016] (In formula (V), X represents a fluoro group (—F), a chloro group (—Cl), a bromo group (—Br), or an iodo group (—I), and R ５１ each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), and an oxa group (-O-) as a substituent, and h represents an integer of 0 to 3. <13> A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a nonaqueous electrolyte solution, and a separator, wherein the nonaqueous electrolyte solution is the nonaqueous electrolyte solution according to any one of <1> to <12>. <14> The nonaqueous electrolyte secondary battery according to <13>, wherein the positive electrode comprises a positive electrode active material containing a nickel-containing lithium composite oxide. <15> The nonaqueous electrolyte secondary battery according to <14>, wherein the nickel-containing lithium composite oxide is a composite oxide represented by the following formula (IV): Li ｘ Ni ｙ M ｚ O ２ ... (IV) (In formula (IV), M represents at least one atom selected from the group consisting of Co, Mn, and Al, x is a numerical value satisfying 0.95≦x≦1.15, and y and z are numerical values ​​satisfying 0.4≦y<1.0 and y+z=1.) <16> The nonaqueous electrolyte secondary battery according to <15>, wherein the composite oxide represented by formula (IV) is a composite oxide represented by the following formula (IV-1): Li ｘ Ni ｙ M' ｚ’ Al ｚ” O ２ ...(IV-1) (In formula (IV-1), M' represents at least one atom selected from the group consisting of Co and Mn, x is a numerical value satisfying 0.95≦x≦1.15, and y, z', and z" are numerical values ​​satisfying 0.4≦y<1.0 and y+z'+z"=1.)

[0017] According to an embodiment of the first aspect of the present disclosure, there are provided a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery that suppress an increase in resistance of a lithium-ion secondary battery after high-temperature storage. According to an embodiment of the second aspect of the present disclosure, the battery resistance, particularly the initial battery resistance, of the nonaqueous electrolyte secondary battery can be suppressed to a low level.

[0018] 1 is a schematic cross-sectional view showing a stacked-type lithium ion secondary battery precursor, which is an example of a lithium ion secondary battery precursor, and FIG. 2 is a schematic cross-sectional view showing a coin-type lithium ion secondary battery precursor, which is another example of a lithium ion secondary battery precursor.

[0019] The present disclosure will be described below. However, the present disclosure is not limited to the following embodiments and can be modified as appropriate within the scope of the purpose of the present disclosure. Unless otherwise specified, matters described as "of the present disclosure" or "in the present disclosure" are matters common to the first and second aspects.

[0020] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits. In numerical ranges described in stages in the present disclosure, the upper or lower limit described in one numerical range may be replaced with the upper or lower limit of another staged numerical range. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. In the present disclosure, when multiple substances corresponding to each component are present in the composition, the amount of each component refers to the total amount of those multiple substances present in the composition, unless otherwise specified. In the present disclosure, "mass" and "weight" are synonymous, and "mass%" and "wt%" are synonymous. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the description of a group (atomic group) in the present disclosure, a description that does not specify whether it is substituted or unsubstituted includes both those that do not contain a substituent and those that contain a substituent. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0021] <Non-aqueous Electrolyte Solution of First Aspect> A non-aqueous electrolyte solution that is a first embodiment in the first aspect of the present disclosure (hereinafter may be abbreviated as “the present non-aqueous electrolyte solution 1”) is characterized by containing a carbodiimide compound represented by formula (I) (hereinafter may be abbreviated as “carbodiimide compound”) and a disulfonic acid ester compound represented by formula (II-1) or formula (II-2) (hereinafter may be abbreviated as “disulfonic acid ester compound”).

[0022] The carbodiimide compound represented by formula (I) and the disulfonic acid ester compound represented by formula (II-1) or formula (II-2) are additives in the non-aqueous electrolyte solution. In addition, formula (II-1) and formula (II-2) may be collectively referred to as formula (II).

[0023]

[0024] [In formula (I), R １１ each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.

[0025]

[0026] [In formulas (II-1) and (II-2), R ２１ and R ２２ each independently represents a substituent selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of ２３ each independently represents a substituent selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ and represents a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of

[0027] The present inventors have conducted extensive research in order to provide a nonaqueous electrolyte solution that can suppress an increase in resistance after high-temperature storage of a lithium ion secondary battery. As a result, they have found that by using a nonaqueous electrolyte solution that combines at least one carbodiimide compound selected from the group consisting of compounds represented by formula (I) and at least one disulfonic acid ester compound selected from the group consisting of compounds represented by formula (II-1) or formula (II-2), an increase in resistance after high-temperature storage of a lithium ion secondary battery can be effectively suppressed.

[0028] Hereinafter, the "carbodiimide compound represented by formula (I)", the "disulfonic acid ester compound represented by formula (II-1) or formula (II-2)", etc. will be described in detail.

[0029] (Carbodiimide Compound Represented by Formula (I)) The carbodiimide compound is represented by the following formula (I).

[0030]

[0031] R １１ each independently represent a "hydrocarbon group having 1 to 12 carbon atoms" or a "trialkylsilyl group having 3 to 18 carbon atoms", but the "hydrocarbon group" is not limited to an aliphatic hydrocarbon group having a straight-chain structure, and may be a hydrocarbon group having at least one structure selected from the group consisting of a branched structure, a cyclic structure, and a carbon-carbon unsaturated bond structure (a carbon-carbon double bond structure and a carbon-carbon triple bond structure), and the number of these structures is not limited. Therefore, (acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, polycyclic aromatic hydrocarbon groups, etc. are all included in the "hydrocarbon group". Furthermore, naturally, alkyl groups, alkenyl groups, alkynyl groups, aryl groups, etc. are all included in the "hydrocarbon group". Furthermore, a "trialkylsilyl group having 3 to 18 carbon atoms" is a group represented by -SiR ３ As represented by the formula: Figure imgf000012_0001, it is a group in which three hydrocarbon groups are bonded to a silicon atom, and the number of carbon atoms represents the total number of carbon atoms in the three hydrocarbon groups.

[0032] R １１When R is a hydrocarbon group, the number of carbon atoms is preferably 2 or more, more preferably 3 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. １１ When is a trialkylsilyl group, it preferably has 12 or less carbon atoms, more preferably 9 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0033] R １１ The hydrocarbon group is a methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), i-propyl group (—CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ２ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ) and the like, and R １１ The trialkylsilyl group includes a trimethylsilyl group (—Si(CH ３ ) ３ ), triethylsilyl group (—Si(CH ２ CH ３ ) ３ ), and the like, but an i-propyl group (—CH(CH ３ ) ２ ), a cyclohexyl group (-C ６ H １１ ), or a trimethylsilyl group (—Si(CH ３ ) ３ ) is particularly preferred.

[0034] Examples of the carbodiimide compound represented by formula (I) include N,N'-di-i-propylcarbodiimide represented by the following formula (IA), N,N'-dicyclohexylcarbodiimide represented by (IB), and N,N'-bis(trimethylsilyl)carbodiimide represented by (IC). Note that the nonaqueous electrolyte solution 1 may contain two or more types of carbodiimide compounds represented by formula (I).

[0035]

[0036] The content of the carbodiimide compound in the non-aqueous electrolyte 1 is usually 0.001% by mass or more and 5.0% by mass or less, with the lower limit being preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, and the upper limit being preferably 3.0% by mass or less, more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less, relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is 100% by mass). When the content of the carbodiimide compound is within the above range, the low-temperature resistance value after high-temperature storage is easily reduced.

[0037] (Disulfonic acid ester compound represented by formula (II-1) or formula (II-2)) The disulfonic acid ester compound is represented by the following formula (II-1) or formula (II-2).

[0038]

[0039] R ２１ and R ２２ are each independently a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２The term "divalent hydrocarbon group" refers to a hydrocarbon group having two bonding positions, and is not limited to aliphatic hydrocarbon groups having a straight-chain structure, but may be a hydrocarbon group having at least one structure selected from the group consisting of a branched structure, a cyclic structure, and a carbon-carbon unsaturated bond structure (a carbon-carbon double bond structure and a carbon-carbon triple bond structure). The number of these structures is not limited, and therefore (acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, polycyclic aromatic hydrocarbon groups, etc. are all included in the term "hydrocarbon group." Naturally, alkylene groups, alkenylene groups, alkynylene groups, arylene groups, etc. are also all included in the term "divalent hydrocarbon group." In addition, "substituents include fluoro (-F), chloro (-Cl), bromo (-Br), oxa (-O-), carbonyl (>C=O), and sulfonyl (>S(=O) ２ ) may contain at least one functional group selected from the group consisting of R １１ This is equivalent to the case where

[0040] R ２１ The number of carbon atoms in the hydrocarbon group of R is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less. ２２ The number of carbon atoms in the hydrocarbon group is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less.

[0041] R ２１ Examples of the methyl group include a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), n-propylene group (-CH ２ CH ２ CH ２ -), n-butylene group (-CH ２ CH ２ CH ２ CH ２ -), and a methylene group (-CH ２ -) is particularly preferred. ２２Examples of the methyl group include a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), n-propylene group (-CH ２ CH ２ CH ２ -), n-butylene group (-CH ２ CH ２ CH ２ CH ２ -), and a methylene group (-CH ２ -) is particularly preferred.

[0042] R ２３ are each independently a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ ) which may contain at least one functional group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ The terms "may contain at least one functional group selected from the group consisting of R １１ This is equivalent to the case where

[0043] R ２３ The hydrocarbon group preferably has 10 or less carbon atoms, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0044] R ２３ As examples, methyl groups (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), i-propyl group (—CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ) etc.

[0045] Examples of the disulfonic acid ester compound represented by formula (II-1) or formula (II-2) include compounds represented by the following formulas (II-A) to (II-M). Note that the nonaqueous electrolyte solution 1 may contain two or more disulfonic acid ester compounds represented by formula (II-1) or formula (II-2).

[0046]

[0047] The content of the disulfonic acid ester compound in the non-aqueous electrolyte 1 is typically 0.01% by mass or more and 5.0% by mass or less, with the lower limit being preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, and the upper limit being preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less, relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is taken as 100% by mass). When the content of the disulfonic acid ester compound is within the above range, the low-temperature resistance value after high-temperature storage is easily reduced.

[0048] The nonaqueous electrolyte 1 preferably further contains a cyclic sulfate ester compound represented by formula (III) (hereinafter, sometimes abbreviated as "cyclic sulfate ester compound"). That is, one embodiment of the nonaqueous electrolyte 1 preferably contains a carbodiimide compound represented by formula (I), a disulfonic acid ester compound represented by formula (II-1) or formula (II-2), and a cyclic sulfate ester compound represented by formula (III). The cyclic sulfate ester compound represented by formula (III) is also an additive in the nonaqueous electrolyte, and by incorporating the cyclic sulfate ester compound represented by formula (III), it is possible to more effectively suppress an increase in resistance of a lithium ion secondary battery after high-temperature storage.

[0049]

[0050] [In formula (III), R ３１ are each independently a group represented by formula (iii-1), a group represented by formula (iii-2), a hydrogen atom (—H), or a substituent selected from the group consisting of a fluoro group (—F), a chloro group (—Cl), a bromo group (—Br), an oxa group (—O—), a carbonyl group (>C═O), and a sulfonyl group (>S(═O) ２ R represents a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of ３２ is a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and as a substituent, a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ a hydrocarbon group having 1 to 12 carbon atoms, a fluorocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a group represented by formula (iii-3), which may contain at least one functional group selected from the group consisting of: a hydrocarbon group having 1 to 12 carbon atoms, a fluorocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a group represented by formula (iii-3).] Hereinafter, the "cyclic sulfate ester compound represented by formula (III)" will be described in detail.

[0051] (Cyclic sulfate ester compound represented by formula (III)) The cyclic sulfate ester compound is represented by the following formula (III).

[0052]

[0053] R ３１ are each independently "a group represented by formula (iii-1)", "a group represented by formula (iii-2)", "a hydrogen atom (-H)", or "a group having as a substituent a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ The wavy lines in formula (iii-1) and formula (iii-2) represent the R ３１ The end of the wavy line is bonded to the ethylene group of the five-membered ring of the cyclic sulfate ester. １１ In addition, "substituents include fluoro (-F), chloro (-Cl), bromo (-Br), oxa (-O-), carbonyl (>C=O), and sulfonyl (>S(=O) ２ The phrase "may contain at least one functional group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), etc., in which a hydrogen atom of the hydrocarbon group is substituted with an oxa group (-O-), a carbonyl group (>C=O), a sulfonyl group (>S(=O) ２ ) and the like. ３１ At least one of R is preferably a "group represented by formula (iii-1)" or a "group represented by formula (iii-2)". For example, R ３１ When one of the groups is a hydrogen atom (—H), the other is preferably a group represented by formula (iii-1) or a group represented by formula (iii-2).

[0054] R ３１ is a hydrocarbon group, R ３１ The number of carbon atoms is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less.

[0055] R ３１ Examples of the alkyl group include a group represented by formula (iii-1), a group represented by formula (iii-2), a hydrogen atom (—H), a methyl group (—CH ３ ), ethyl group (-CH ２CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), i-propyl group (—CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ) and so on. Two R ３１ The combination of the group represented by formula (iii-1) and a hydrogen atom (—H), an n-propyl group (—CH ２ CH ２ CH ３ A combination of a group represented by formula (iii-1) and a hydrogen atom (-H), and a combination of a hydrogen atom (-H) and a hydrogen atom (-H) are preferred, and a combination of a group represented by formula (iii-1) and a hydrogen atom (-H) is particularly preferred.

[0056] R ３２ is a "fluoro group (-F)", a "chloro group (-Cl)", a "bromo group (-Br)", and "substituted with a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ "a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of "a hydrocarbon group having 1 to 12 carbon atoms," "a fluorocarbon group having 1 to 12 carbon atoms," "an alkoxy group having 1 to 12 carbon atoms," or "a group represented by formula (iii-3)." The wavy line in formula (iii-3) represents R ３２The tip of the wavy line is an oxysulfonyl group (-OS(=O) ２ ) is bonded to the sulfur atom. In addition, "substituents include fluoro (-F), chloro (-Cl), bromo (-Br), oxa (-O-), carbonyl (>C=O), and sulfonyl (>S(=O) ２ The terms "may contain at least one functional group selected from the group consisting of R １１ The term "fluorocarbon group" refers to a hydrocarbon group in which all hydrogen atoms have been substituted with fluoro groups (--F).

[0057] R ３２ is a hydrocarbon group, R ３２ The number of carbon atoms in R is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less. ３２ is a fluorocarbon group, R ３２ The number of carbon atoms in R is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less. ３２ is an alkoxy group, R ３２ The number of carbon atoms is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less.

[0058] R ３２ Examples of the fluoro group (-F), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), i-propyl group (—CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２CH ２ CH ２ CH ２ CH ３ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ), a trifluoromethyl group (—CF ３ ), a pentafluoroethyl group (—CF ２ CF ３ ), n-heptafluoropropyl group (—CF ２ CF ２ CF ３ ), a methoxy group (—OCH ３ ), ethoxy group (—OCH ２ CH ３ ), n-propoxy group (—OCH ２ CH ２ CH ３ ), a group represented by formula (iii-3), and the like.

[0059] Examples of the cyclic sulfate ester compound represented by formula (III) include compounds represented by the following formulas (III-A), (III-B), (III-C), and (III-D). Note that the nonaqueous electrolyte solution 1 may contain two or more types of cyclic sulfate ester compounds represented by formula (III).

[0060]

[0061] The content of the cyclic sulfate ester compound in the non-aqueous electrolyte 1 is typically 0.01% by mass or more and 5.0% by mass or less, with the lower limit being preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, and the upper limit being preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less, relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is taken as 100% by mass). When the content of the cyclic sulfate ester compound is within the above range, the low-temperature resistance value after high-temperature storage is easily reduced.

[0062] A nonaqueous electrolyte solution according to a second embodiment of the first aspect of the present disclosure (hereinafter sometimes abbreviated as “the present nonaqueous electrolyte solution 2”) is characterized by containing a carbodiimide compound represented by the following formula (I-2):

[0063]

[0064] R １２ Each independently represents a "hydrocarbon group having 1 to 6 carbon atoms", but the "hydrocarbon group" is １１ This is equivalent to the case where

[0065] R １２ The hydrocarbon group is a methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), i-propyl group (—CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ２ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ) etc.

[0066] Examples of the carbodiimide compound represented by formula (I-2) include N,N'-bis(trimethylsilyl)carbodiimide represented by the following formula (IC): The nonaqueous electrolyte solution 2 may contain two or more types of carbodiimide compounds represented by formula (I).

[0067]

[0068] The content of the carbodiimide compound represented by formula (I-2) in the non-aqueous electrolyte 2 is typically 0.001% by mass or more and 5.0% by mass or less, with the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is 100% by mass), with the lower limit preferably being 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, and the upper limit preferably being 3.0% by mass or less, more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. When the content of the carbodiimide compound is within the above range, it is easier to reduce the low-temperature resistance value after high-temperature storage.

[0069] <Non-aqueous Electrolyte Solution of Second Aspect> A non-aqueous electrolyte solution according to an embodiment of the second aspect of the present disclosure (hereinafter sometimes abbreviated as "the present non-aqueous electrolyte solution 3") is used in a non-aqueous electrolyte secondary battery containing a nickel-containing lithium composite oxide as a positive electrode active material, and is characterized by containing a carbodiimide compound represented by the following formula (I). Note that the "carbodiimide compound represented by formula (I)" in the present non-aqueous electrolyte solution 3 is the same as the "carbodiimide compound represented by formula (I)" in the present non-aqueous electrolyte solution 1, and therefore a detailed description thereof will be omitted. [In formula (I), R １１ each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.

[0070] The present nonaqueous electrolyte 3 exhibits the effect of reducing battery resistance, particularly initial battery resistance, by incorporating a carbodiimide compound represented by formula (I) into a nonaqueous electrolyte used in a nonaqueous electrolyte secondary battery containing a nickel-containing lithium composite oxide as a positive electrode active material. While the details of the mechanism by which the incorporation of the carbodiimide compound represented by formula (I) reduces initial battery resistance have not been specifically elucidated, it is believed that the carbodiimide compound represented by formula (I) or the like forms a suitable coating on the electrode surface, and that this coating is particularly suitable for positive electrodes that include a positive electrode active material containing a nickel-containing lithium composite oxide. The battery resistance can be calculated, for example, by discharging a charged battery at a constant current for a certain period of time and then calculating the difference (voltage drop) between the voltage at the start of discharge and the voltage after the certain period of time has elapsed.

[0071] In particular, the nonaqueous electrolyte solution 3 can reduce battery resistance in low-temperature environments, particularly the initial battery resistance in low-temperature environments, by incorporating the carbodiimide compound represented by formula (I). Here, the battery resistance in low-temperature environments can be calculated by discharging a charged battery at a constant current for a certain period of time in a low-temperature environment, such as −20° C., and then calculating the difference (voltage drop) between the voltage at the start of discharge and the voltage after the certain period of time has elapsed.

[0072] The "nickel-containing lithium composite oxide" will be described in detail later in connection with the nonaqueous electrolyte secondary battery, which is another embodiment of the present invention.

[0073] The total content of the carbodiimide compound represented by formula (I) in the nonaqueous electrolyte solution 3 can be appropriately set within the range of 0.001% by mass to 5.0% by mass relative to the total amount of the nonaqueous electrolyte solution (when the total amount of the nonaqueous electrolyte solution is taken as 100% by mass). The lower limit of the total content of the carbodiimide compound is not limited to 0.001% by mass, and can be 0.005% by mass or more, 0.01% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.1% by mass or more, or 0.3% by mass or more. The upper limit of the total content of the carbodiimide compound is not limited to 5.0% by mass, and can be 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, 0.5% by mass or less, 0.3% by mass or less, 0.2% by mass or less, or 0.1% by mass or less. In particular, the total content of the carbodiimide compound represented by formula (I) in the nonaqueous electrolyte solution 3 is preferably 0.001% by mass to 0.5% by mass, and more preferably 0.001% by mass to 0.2% by mass, relative to the total amount of the nonaqueous electrolyte solution (when the total amount of the nonaqueous electrolyte solution is taken as 100% by mass).

[0074] That is, the total content of the carbodiimide compound represented by formula (I) in the present nonaqueous electrolyte solution 3 may be a normal addition amount typically in the range of 0.1% by mass to 5.0% by mass relative to the total amount of the nonaqueous electrolyte solution (when the total amount of the nonaqueous electrolyte solution is taken as 100% by mass). In the normal addition amount, the lower limit is preferably 0.3% by mass or more. In the normal addition amount, the upper limit is preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less.

[0075] On the other hand, the total content of the carbodiimide compound represented by formula (I) in the present nonaqueous electrolyte solution 3 may be added in a trace amount, typically in the range of 0.001% by mass to 0.1% by mass, relative to the total amount of the nonaqueous electrolyte solution (when the total amount of the nonaqueous electrolyte solution is taken as 100% by mass). In the trace amount addition, the lower limit is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.03% by mass or more. In the trace amount addition, the upper limit is preferably 0.08% by mass or less, more preferably 0.05% by mass or less, and even more preferably 0.03% by mass or less.

[0076] When the total content of the carbodiimide compound represented by formula (I) in the present nonaqueous electrolyte solution 3 is within the above range, the initial low-temperature resistance value and the low-temperature resistance value after high-temperature storage tend to be reduced.

[0077] The nonaqueous electrolyte solution 3 preferably further contains a cyclic carbonate compound represented by the following formula (V).

[0078] In formula (V), X represents a fluoro group (—F), a chloro group (—Cl), a bromo group (—Br), or an iodo group (—I), and R ５１ each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), and an oxa group (-O-) as a substituent, and h represents an integer of 0 to 3. X is preferably a fluoro group (-F).

[0079] R ５１each independently represents a "fluoro group (-F)", a "chloro group (-Cl)", a "bromo group (-Br)", an "iodine group (-I)", or a "hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), and an oxa group (-O-) as a substituent", but the "hydrocarbon group" is not defined as R １１ This is equivalent to the case where

[0080] R ５１ When is a hydrocarbon group, it preferably has 10 or less carbon atoms, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less carbon atoms.

[0081] R ５１ Examples of the fluorine-containing alkyl group include a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), and a methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), i-propyl group (—CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ２ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH ３ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ) etc.

[0082] h represents an integer of 0 to 3, with 0 being particularly preferred.

[0083] Examples of the cyclic carbonate compound represented by formula (V) include a compound represented by the following formula, which contains fluoroethylene carbonate (FEC): Note that the nonaqueous electrolyte solution 3 may contain two or more types of cyclic carbonate compounds represented by formula (V).

[0084] The total content of the cyclic carbonate compounds represented by formula (V) in the nonaqueous electrolyte 3 is usually 0.01% by mass or more and 5.0% by mass or less, based on the total amount of the nonaqueous electrolyte (when the total amount of the nonaqueous electrolyte is 100% by mass). The lower limit is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more. The upper limit is preferably 4.0% by mass or less, more preferably 3.5% by mass or less, even more preferably 3.0% by mass or less, and particularly preferably 2.5% by mass or less. When the total content of the cyclic carbonate compounds represented by formula (V) is within the above range, it is easy to control the capacity retention rate and resistance increase rate after charge / discharge cycling to good values.

[0085] The cyclic carbonate compound represented by formula (V) can also be used as a non-aqueous solvent, as described below. When used as a non-aqueous solvent, the total content of the cyclic carbonate compound represented by formula (V) in the non-aqueous electrolyte is usually 5% by mass or more and 50% by mass or less, relative to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is 100% by mass). The lower limit is preferably 7% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less.

[0086] <Non-aqueous solvent> In the present disclosure, the non-aqueous electrolyte generally contains a non-aqueous solvent. Various known non-aqueous solvents can be appropriately selected as the non-aqueous solvent. The non-aqueous solvent may be one type only, or two or more types.

[0087] Examples of non-aqueous solvents include cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, fluorine-containing chain carbonates, aliphatic carboxylic acid esters, fluorine-containing aliphatic carboxylic acid esters, γ-lactones, fluorine-containing γ-lactones, cyclic ethers, fluorine-containing cyclic ethers, chain ethers, fluorine-containing chain ethers, nitriles, amides, lactams, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide, dimethyl sulfoxide phosphate, etc. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of fluorine-containing cyclic carbonates include fluoroethylene carbonate (FEC), etc. Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), dipropyl carbonate (DPC), etc. Examples of fluorine-containing chain carbonates include methyl-2,2,2-trifluoroethyl carbonate, etc.

[0088] Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylbutyrate, ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, ethyl isobutyrate, and ethyl trimethylbutyrate. Examples of fluorine-containing aliphatic carboxylic acid esters include methyl difluoroacetate, methyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, and 2,2,2-trifluoroethyl acetate. Examples of γ-lactones include γ-butyrolactone and γ-valerolactone. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, and 1,4-dioxane. Examples of fluorine-containing cyclic ethers include ethyl nonafluorobutyl ether and methyl nonafluorobutyl ether. Examples of the chain ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, 1,2-dibutoxyethane, etc. Examples of the fluorine-containing chain ethers include HCF ２ CF ２ CH ２ OCF ２ CF ２ H, C.F. ３ CF ２ CH ２ OCF ２ CF ２ H, HCF ２ CF ２ CH ２ OCF ２ CFHCF ３ , C.F. ３ CF ２ CH ２ OCF ２ CFHCF ３ , C ６ F １３ OCH ３ , C ６ F １３ O.C. ２ H ５ , C ８ F１７ OCH ３ , C ８ F １７ O.C. ２ H ５ , C.F. ３ CFHCF ２ CH (CH ３ ) OCF ２ CFHCF ３ , HCF ２ CF ２ OCH (C ２ H ５ ) ２ , HCF ２ CF ２ O.C. ４ H ９ , HCF ２ CF ２ OCH ２ CH(C ２ H ５ ) ２ , HCF ２ CF ２ OCH ２ CH (CH ３ ) ２ Examples of nitriles include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, etc. Examples of amides include N,N-dimethylformamide, etc. Examples of lactams include N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, etc.

[0089] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, and fluorine-containing chain carbonates. In this case, the total proportion of the cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, and fluorine-containing chain carbonates is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the non-aqueous solvent.

[0090] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates and chain carbonates. In this case, the total proportion of the cyclic carbonates and chain carbonates in the non-aqueous solvent is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the non-aqueous solvent.

[0091] The upper limit of the content of the nonaqueous solvent is preferably 99 mass %, more preferably 97 mass %, and even more preferably 90 mass % relative to the total amount of the nonaqueous electrolyte, and the lower limit of the content of the nonaqueous solvent is preferably 60 mass % or more, and even more preferably 70 mass % or more relative to the total amount of the nonaqueous electrolyte.

[0092] From the viewpoint of further improving the dissociation property of the electrolyte and the mobility of ions, the intrinsic viscosity of the nonaqueous solvent is preferably 10.0 mPa s or less at 25° C. The intrinsic viscosity of the nonaqueous solvent is a value measured at 25° C. using an Ubbelohde viscometer in accordance with Japanese Industrial Standard JIS Z 8803 "Method for measuring viscosity of liquids."

[0093] <Electrolyte> In the present disclosure, the non-aqueous electrolyte generally contains an electrolyte.

[0094] The electrolyte preferably contains at least one of a fluorine-containing lithium salt (hereinafter sometimes referred to as a "fluorine-containing lithium salt") and a fluorine-free lithium salt.

[0095] Examples of the fluorine-containing lithium salt include inorganic acid anion salts and organic acid anion salts. Examples of the inorganic acid anion salt include lithium hexafluorophosphate (LiPF ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium hexafluoroarsenate (LiAsF ６ ), lithium hexafluorotantalate (LiTaF ６ Examples of organic acid anion salts include lithium trifluoromethanesulfonate (LiCF ３ SO ３), lithium bis(trifluoromethanesulfonyl)imide (Li(CF ３ SO ２ ) ２ N), lithium bis(pentafluoroethanesulfonyl)imide (Li(C ２ F ５ SO ２ ) ２ Among them, examples of fluorine-containing lithium salts include lithium hexafluorophosphate (LiPF ６ ) is more preferred.

[0096] Examples of fluorine-free lithium salts include lithium perchlorate (LiClO ４ ), lithium aluminum tetrachloride (LiAlCl ４ ), lithium decachlorodecaborate (Li ２ B １０ Cl １０ ) etc.

[0097] When the electrolyte contains a fluorine-containing lithium salt, the content of the fluorine-containing lithium salt is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the electrolyte. ６ ), lithium hexafluorophosphate (LiPF ６ The content of the component (I) is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, based on the total amount of the electrolyte.

[0098] When the non-aqueous electrolyte solution contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte solution is preferably 0.1 mol / L or more and 3 mol / L or less, more preferably 0.5 mol / L or more and 2 mol / L or less.

[0099] The non-aqueous electrolyte is lithium hexafluorophosphate (LiPF ６ ), the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF ６The concentration of the HCl HCl is preferably 0.1 mol / L or more and 3 mol / L or less, more preferably 0.5 mol / L or more and 2 mol / L or less.

[0100] <Nonaqueous Electrolyte Secondary Battery> The nonaqueous electrolyte secondary battery (hereinafter sometimes abbreviated as "nonaqueous electrolyte secondary battery") of the present disclosure includes a "positive electrode," a "negative electrode," a "nonaqueous electrolyte," and a "separator," and the nonaqueous electrolyte is the present nonaqueous electrolyte 1, the present nonaqueous electrolyte 2, or the present nonaqueous electrolyte 3 described above. The nonaqueous electrolyte secondary battery is obtained by charging and discharging a nonaqueous electrolyte secondary battery precursor, which is a nonaqueous electrolyte secondary battery before charging and discharging. The nonaqueous electrolyte secondary battery precursor refers to a nonaqueous electrolyte secondary battery before charging and discharging. A specific example of a nonaqueous electrolyte secondary battery precursor is a lithium ion secondary battery precursor that charges and discharges by the movement of lithium ions, and a specific example of a nonaqueous electrolyte secondary battery is a lithium ion secondary battery obtained by charging and discharging a lithium ion secondary battery precursor. The "positive electrode," "negative electrode," "separator," etc. will be described in detail below.

[0101] (Positive Electrode) In the present disclosure, the positive electrode can be generally produced by dispersing positive and negative electrode active materials, a binder, and, if necessary, a conductive additive and a thickener in a solvent to form a slurry, and then applying this slurry to a current collector, drying, and compressing it to form a positive electrode mixture layer (also referred to as a "positive electrode active material layer") on the current collector.

[0102] In the present disclosure, the positive electrode active material is not particularly limited as long as it is a material that can absorb and release lithium ions, and can be adjusted appropriately depending on the application of the lithium ion secondary battery precursor, etc.

[0103] Examples of positive electrode active materials include a first oxide and a second oxide. The first oxide contains lithium (Li) and nickel (Ni) as constituent metal elements. The second oxide contains Li, Ni, and at least one metal element other than Li and Ni as constituent metal elements. Examples of metal elements other than Li and Ni include transition metal elements and typical metal elements. The second oxide preferably contains the metal elements other than Li and Ni in an amount equivalent to or less than Ni in atomic number terms. The metal elements other than Li and Ni may be, for example, at least one selected from the group consisting of Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. These positive electrode active materials may be used alone or in combination.

[0104] The positive electrode active material preferably contains the following "composite oxide represented by formula (IV)": Li ｘ Ni ｙ M ｚ O ２ ... (IV) (In formula (IV), M represents at least one atom selected from the group consisting of Co, Mn, and Al, x is a numerical value satisfying 0.95≦x≦1.15, and y and z are numerical values ​​satisfying 0.4≦y<1.0 and y+z=1.)

[0105] In formula (IV), x is a numerical value that satisfies 0.95≦x≦1.15, and the lower limit is preferably 0.96 or more, more preferably 0.97 or more, and even more preferably 0.98 or more, and the upper limit is preferably 1.10 or less, more preferably 1.08 or less, even more preferably 1.06 or less, and particularly preferably 1.04 or less.

[0106] In formula (IV), y is a numerical value that satisfies 0.4≦y<1.0, and the lower limit is preferably 0.5 or more, more preferably 0.6 or more, even more preferably 0.7 or more, even more preferably 0.75 or more, and even more preferably 0.80 or more. The upper limit is preferably 0.95 or less, more preferably 0.90 or less, even more preferably 0.88 or less, and particularly preferably 0.85 or less.

[0107] In formula (IV), z is a value such that y satisfies 0.4≦y<1.0, and 0<z≦0.6 because y+z=1. The lower limit of z is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more.

[0108] The composite oxide represented by formula (IV) preferably contains aluminum (Al). That is, M in formula (IV) preferably contains Al. In this case, the composite oxide represented by formula (IV) is preferably a composite oxide represented by the following formula (IV-1): Li ｘ Ni ｙ M' ｚ’ Al ｚ” O ２ ...(IV-1) (In formula (IV-1), M' represents at least one atom selected from the group consisting of Co and Mn, x is a numerical value satisfying 0.95≦x≦1.15, and y, z', and z" are numerical values ​​satisfying 0.4≦y<1.0 and y+z'+z"=1.)

[0109] The lower limit of z' in formula (IV-1) is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more.

[0110] The lower limit of z″ in formula (IV-1) is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.03 or more. The upper limit is preferably 0.3 or less, more preferably 0.25 or less, and even more preferably 0.2 or less.

[0111] The composite oxide represented by formula (IV-1) includes LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiNi ０．８８ Co ０．０９ Al ０．０３ etc.

[0112] As the composite oxide represented by formula (IV) other than the composite oxide represented by formula (IV-1), LiNi ０．５ Co ０．３ Mn ０．２O ２ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ In addition, examples of nickel-containing lithium composite oxides other than the composite oxide represented by formula (IV) include LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ As the positive electrode active material, a composite oxide represented by formula (IV-1), a composite oxide represented by formula (IV) other than the composite oxide represented by formula (IV-1), and a nickel-containing lithium composite oxide other than the composite oxide represented by formula (IV) can also be used in appropriate combination.

[0113] The content of the positive electrode active material in the positive electrode mixture layer is preferably 10% by mass or more and 99.9% by mass or less, more preferably 30% by mass or more and 99.9% by mass or less, even more preferably 50% by mass or more and 99% by mass or less, and particularly preferably 70% by mass or more and 99% by mass or less, relative to the total amount of the positive electrode mixture layer. Of the total positive electrode active material, the nickel-containing lithium composite oxide can be 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, still more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0114] In the present disclosure, examples of binders include polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluororesins, and rubber particles. Examples of fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer. Examples of rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles. Among these, fluororesins are preferred from the viewpoint of improving the oxidation resistance of the positive electrode mixture layer. One type of binder can be used alone, or two or more types can be used in combination as needed.

[0115] The content of the binder in the positive electrode mixture layer is preferably 0.1% by mass or more and 4% by mass or less, based on the total amount of the positive electrode mixture layer, from the viewpoint of achieving both the physical properties of the positive electrode mixture layer (e.g., electrolyte permeability, peel strength, etc.) and battery performance. When the binder content is 0.1% by mass or more, the adhesion of the positive electrode mixture layer to the positive electrode current collector and the binding between the positive electrode active materials are further improved. When the binder content is 4% by mass or less, the amount of positive electrode active material in the positive electrode mixture layer can be increased, thereby further improving the discharge capacity.

[0116] The positive electrode mixture layer preferably contains a conductive additive. Known conductive additives can be used as the conductive additive. A conductive carbon material is preferred as the known conductive additive. Examples of conductive carbon materials include graphite, carbon black, conductive carbon fiber, and fullerene. These materials can be used alone or in combination of two or more. Examples of conductive carbon fibers include carbon nanotubes, carbon nanofibers, and carbon fibers. Examples of graphite include artificial graphite and natural graphite. Examples of natural graphite include flake graphite, lump graphite, and amorphous graphite.

[0117] In the present disclosure, the conductive additive may be a commercially available product. Examples of commercially available carbon black products include Toka Black #4300, #4400, #4500, #5500, etc. (furnace black manufactured by Tokai Carbon Co., Ltd.), Printex L, etc. (furnace black manufactured by Degussa), Raven 7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, etc., Conductex SC ULTRA, Conductex 975ULTRA, etc., and PUER BLACK 100, 115, 205, etc. (Columbian Furnace Black), #2350, #2400B, #2600B, #30050B, #3030B, #3230B, #3350B, #3400B, #5400B, etc. (Mitsubishi Chemical Furnace Black), MONARCH 1400, 1300, 900, Vulcan XC-72R, BlackPearls 2000, Examples of such blacks include LITX-50 and LITX-200 (furnace blacks manufactured by Cabot Corporation), Ensaco 250G, Ensaco 260G, Ensaco 350G, and Super-P (manufactured by TIMCAL), Ketjen Black EC-300J and EC-600JD (manufactured by Akzo Chemicals), and Denka Black, Denka Black HS-100 and FX-35 (acetylene blacks manufactured by Denka Co., Ltd.).

[0118] The positive electrode mixture layer may contain other components such as a thickener, a surfactant, a dispersant, a wetting agent, and an antifoaming agent.

[0119] In the present disclosure, examples of the material for the positive electrode current collector include metals and alloys. Specifically, examples of the material for the positive electrode current collector include aluminum, nickel, stainless steel (SUS), and copper. Among these, aluminum is preferred from the viewpoint of the balance between high conductivity and cost. Here, "aluminum" refers to pure aluminum or an aluminum alloy. Aluminum foil is preferred as the positive electrode current collector. The material of the aluminum foil is not particularly limited, and examples include A1085 material, A3003 material, and the like.

[0120] (Negative Electrode) In the present disclosure, the negative electrode can generally be produced by dispersing a negative electrode active material and a binder, and optionally a conductive additive and a thickener, in a solvent to form a slurry, applying this slurry to a negative electrode current collector, drying, and compressing it to form a negative electrode composite layer (also referred to as a "negative electrode active material layer") on the negative electrode current collector.

[0121] In the present disclosure, the elements or compounds that serve as the negative electrode active material can be classified into (1) elemental carbon and carbon compounds that can be doped / dedoped with lithium ions, (2) metals and alloys that can be alloyed with lithium, and (3) oxides, nitrides, carbides, etc. that can be doped / dedoped with lithium ions. When the negative electrode active material is elemental silicon, etc., a particulate (powder) element or compound is usually used. Furthermore, the negative electrode active material used is not limited to one type, and two or more types may be mixed and used.

[0122] The negative electrode active material preferably contains carbon particles and at least one selected from the group consisting of silicon particles, silicon oxide particles, and silicon carbide particles. Examples of carbon particles include graphite (natural graphite, artificial graphite), carbon black particles, activated carbon particles, and amorphous carbon particles. Examples of artificial graphite include graphitized mesocarbon microbeads (MCMB) and graphitized mesophase pitch carbon fiber (MCF). Examples of amorphous carbon materials include hard carbon, coke, and MCMB and MCF calcined at 1500°C or less.

[0123] When the element or compound serving as the negative electrode active material is in the form of particles (powder), specific shapes include fibrous, spherical, potato-like, and flake-like shapes.

[0124] When the negative electrode active material contains particles of simple carbon, the median diameter D50 of the simple carbon is usually 1 μm to 30 μm. The lower limit is preferably 10 μm or more, more preferably 15 μm or more. The upper limit is preferably 25 μm or less, more preferably 20 μm or less.

[0125] When the negative electrode active material contains carbon particles, the BET specific surface area of ​​the carbon particles is usually 1.0 m ２ / g to 5.0m ２The lower limit is preferably 2.0 m / g. ２ / g or more, more preferably 3.0m ２ The upper limit is preferably 4.5 m / g or more. ２ / g or less, more preferably 4.0m ２ / g or less.

[0126] Silicon oxide is SiO ｘ where x is a variable, i.e., the content of oxygen atoms in silicon oxide is not particularly limited, but x is usually 0≦x<2. The lower limit is preferably 0.2 or more, more preferably 0.4 or more, and even more preferably 0.6 or more. The upper limit is preferably 1.8 or less, more preferably 1.6 or less, and even more preferably 1.4 or less.

[0127] The median diameter D50 of silicon particles, silicon oxide particles, or silicon carbide particles is usually 0.5 μm to 20 μm. The lower limit is preferably 1.0 μm or more, more preferably 3.0 μm or more. The upper limit is preferably 15 μm or less, more preferably 10 μm or less.

[0128] The BET specific surface area of ​​silicon particles, silicon oxide particles, or silicon carbide particles is usually 1.0 m ２ / g to 5.0m ２ The lower limit is preferably 1.5 m / g. ２ / g or more, more preferably 2.0m ２ The upper limit is preferably 4.5 m / g or more. ２ / g or less, more preferably 4.0m ２ / g or less.

[0129] When the negative electrode active material contains carbon particles and at least one selected from the group consisting of silicon particles, silicon oxide particles, and silicon carbide particles, the total charged mass of the silicon particles, silicon oxide particles, and silicon carbide particles in the negative electrode active material is typically 1% by mass to 20% by mass, relative to 100% by mass of the total charged mass of the entire negative electrode active material. The lower limit is preferably 3% by mass or more, more preferably 5% by mass or more. The upper limit is preferably 18% by mass or less, more preferably 15% by mass or less.

[0130] When the negative electrode active material contains carbon particles and at least one selected from the group consisting of silicon particles, silicon oxide particles, and silicon carbide particles, the total charged mass of the carbon particles in the negative electrode active material is typically 70% by mass to 99% by mass, where the total charged mass of the entire negative electrode active material is 100% by mass. The lower limit is preferably 80% by mass or more. The upper limit is preferably 95% by mass or less, more preferably 90% by mass or less. When the total charged mass of the silicon particles and the like is within the above range, it becomes easier to ensure a balance between the energy density and capacity retention rate of the nonaqueous electrolyte secondary battery.

[0131] The total content of the negative electrode active material in the negative electrode mixture layer is usually 70% by mass to 99.5% by mass, with the entire negative electrode mixture layer being 100% by mass. The lower limit is preferably 75% by mass or more, and the upper limit is preferably 99% by mass or less.

[0132] In the present disclosure, examples of the binder for the negative electrode include styrene-butadiene rubber (SBR). The total content of the binder copolymer in the negative electrode mixture layer is typically 0.1% by mass to 5% by mass, where the entire negative electrode mixture layer is taken as 100% by mass. The lower limit is preferably 0.5% by mass or more, more preferably 1.0% by mass or more. The upper limit is preferably 3% by mass or less, more preferably 2% by mass or less.

[0133] The negative electrode mixture layer preferably further contains a conductive additive such as carbon black (e.g., acetylene black), carbon nanotubes, amorphous whiskers, or graphite.

[0134] The total content of the conductive additive in the negative electrode mixture layer is usually 0.01% by mass to 3% by mass, where the entire negative electrode mixture layer is taken as 100% by mass. The lower limit is preferably 0.05% by mass or more, more preferably 0.1% by mass or more. The upper limit is preferably 2% by mass or less, more preferably 1% by mass or less.

[0135] The negative electrode mixture layer preferably further contains a thickener. By including a thickener, it becomes easier to adjust the viscosity of the slurry, thereby improving productivity. Examples of thickeners for the negative electrode include cellulose derivatives such as carboxymethyl cellulose (CMC), carboxyethyl cellulose, and hydroxyethyl cellulose, polyoxyethylene and its modified products, polyvinyl alcohol and its modified products, and polysaccharides.

[0136] The total content of the thickener in the negative electrode mixture layer is usually 0.1% by mass to 5% by mass, where the entire negative electrode mixture layer is taken as 100% by mass. The lower limit is preferably 0.5% by mass or more, more preferably 1.0% by mass or more. The upper limit is preferably 3% by mass or less, more preferably 2% by mass or less.

[0137] In the present disclosure, the slurry may contain a solvent. Examples of the solvent include water, acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, and ethylenediamine. The solvent may be a mixed solvent of the above-mentioned solvents.

[0138] In the present disclosure, examples of the material for the negative electrode current collector include copper, nickel, stainless steel, and nickel-plated steel.

[0139] (Separator) In the present disclosure, an example of the separator is a porous resin flat plate. Examples of materials for the porous resin flat plate include resins and nonwoven fabrics containing such resins. Examples of resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, polyamide, and the like. Among these, the separator is preferably a porous resin sheet having a single layer or multilayer structure. The material of the porous resin sheet is mainly composed of one or more polyolefin resins. The thickness of the separator is preferably 5 μm or more and 30 μm or less. The separator is preferably disposed between the positive electrode and the negative electrode.

[0140] (Case) In the present disclosure, the shape of the case is not particularly limited and may be appropriately selected depending on the application of the nonaqueous electrolyte secondary battery, etc. Examples of the case include a case including a laminate film and a case consisting of a battery can and a battery can lid.

[0141] <Specific Example of Lithium-Ion Secondary Battery Precursor> In the present disclosure, a specific example of a lithium-ion secondary battery precursor is a laminated battery precursor. As shown in FIG. 1 , the lithium-ion secondary battery precursor 1 is a laminated battery precursor. Specifically, in the lithium-ion secondary battery precursor 1, a battery element 10 is enclosed inside an exterior body 30. The exterior body 30 is formed of a laminate film. A positive electrode lead 21 and a negative electrode lead 22 are attached to the battery element 10. The positive electrode lead 21 and the negative electrode lead 22 are led out in opposite directions, from the inside to the outside of the exterior body 30.

[0142] Battery element 10 is formed by laminating a positive electrode 11, a separator 13, and a negative electrode 12. Positive electrode 11 is formed by forming positive electrode composite layers 11B on both main surfaces of a positive electrode current collector 11A. Negative electrode 12 is formed by forming negative electrode composite layers 12B on both main surfaces of a negative electrode current collector 12A. Positive electrode composite layer 11B formed on one main surface of positive electrode current collector 11A of positive electrode 11 and negative electrode composite layer 12B formed on one main surface of negative electrode current collector 12A of negative electrode 12 adjacent to positive electrode 11 face each other with separator 13 interposed therebetween.

[0143] The nonaqueous electrolyte solution of the present disclosure is injected into the interior of the exterior housing 30 of the lithium ion secondary battery precursor 1. The nonaqueous electrolyte solution of the present disclosure permeates the positive electrode composite layer 11B, the separator 13, and the negative electrode composite layer 12B. In the lithium ion secondary battery precursor 1, one single cell layer 14 is formed by the adjacent positive electrode composite layer 11B, the separator 13, and the negative electrode composite layer 12B. Note that the positive electrode and the negative electrode may each have an active material layer formed on one side of the respective current collectors.

[0144] Although the lithium ion secondary battery precursor 1 is a laminated type lithium ion secondary battery precursor, the lithium ion secondary battery precursor is not limited to this and may be, for example, a wound type lithium ion secondary battery precursor. A wound type lithium ion secondary battery precursor is formed by stacking a positive electrode, a separator, a negative electrode, and a separator in this order and winding them into a layered configuration. Wound type lithium ion secondary battery precursors include cylindrical type lithium ion secondary battery precursors and prismatic type lithium ion secondary battery precursors.

[0145] 1 , in the lithium ion secondary battery precursor 1, the directions in which the positive electrode lead and the negative electrode lead each protrude from the inside of the exterior body 30 to the outside are opposite directions with respect to the exterior body 30, but the present disclosure is not limited thereto. For example, the directions in which the positive electrode lead and the negative electrode lead each protrude from the inside of the exterior body 30 to the outside may be the same direction with respect to the exterior body 30.

[0146] An example of the nonaqueous electrolyte secondary battery of the present disclosure, which will be described later, is a lithium ion secondary battery obtained by charging and discharging a lithium ion secondary battery precursor 1 shown in FIG.

[0147] A specific example of a lithium ion secondary battery precursor is a coin-type battery precursor. In the coin-type lithium ion secondary battery precursor 2 shown in FIG. 2 , a disc-shaped negative electrode 42, a separator 45 filled with a nonaqueous electrolyte, a disc-shaped positive electrode 41, and, if necessary, a spacer plate 47 made of stainless steel, aluminum, or the like are stacked in this order. A spacer plate 48 is provided on the disc-shaped negative electrode 42 side, and the battery precursor 2 is housed between a positive electrode can 43 (hereinafter also referred to as a "battery can") and a sealing plate 44 (hereinafter also referred to as a "battery can lid"). The positive electrode can 43 and the sealing plate 44 are crimped and sealed via a gasket 46. In this example, the present nonaqueous electrolyte solution 1, the present nonaqueous electrolyte solution 2, or the present nonaqueous electrolyte solution 3 is used as the nonaqueous electrolyte to be filled into the separator 45.

[0148] An example of the nonaqueous electrolyte secondary battery of the present disclosure, which will be described later, is a lithium ion secondary battery obtained by charging and discharging a coin-type lithium ion secondary battery precursor 2 shown in FIG. 2 .

[0149] [Lithium-ion secondary battery and manufacturing method thereof] In the present disclosure, a manufacturing method of a lithium-ion secondary battery includes the steps of: preparing the above-described lithium-ion secondary battery precursor (hereinafter also referred to as the "preparation step"); and charging and discharging the above-described lithium-ion secondary battery precursor. The lithium-ion secondary battery is a lithium-ion secondary battery obtained by charging and discharging the above-described lithium-ion secondary battery precursor.

[0150] According to the lithium ion secondary battery and the method for manufacturing the same, it is possible to reduce the room temperature resistance increase rate of the lithium ion secondary battery when stored at high temperatures.

[0151] The preparation step may be a step of simply preparing a previously manufactured lithium ion secondary battery precursor for a step of charging and discharging, or may be a step of manufacturing a lithium ion secondary battery precursor. The lithium ion secondary battery precursor is as described above.

[0152] In the step of charging and discharging, the charging and discharging of the lithium ion secondary battery precursor can be carried out according to a known method. In this step, the charging and discharging cycle may be repeated multiple times for the lithium ion secondary battery precursor. As described above, this charging and discharging preferably forms an SEI (Solid Electrolyte Interface) film on the surface of the positive electrode (particularly the positive electrode active material) and / or the negative electrode (particularly the negative electrode active material) in the lithium ion secondary battery precursor.

[0153] In the step of charging and discharging, the lithium ion secondary battery precursor is preferably subjected to a combination of charging and discharging at least once in an environment of 25°C to 70°C.

[0154] Examples of the present disclosure will be shown below, but the present disclosure is not limited to the following examples. Hereinafter, "%" means "% by mass" unless otherwise specified.

[0155] [First Aspect] [Example 1-1] <Preparation of Non-Aqueous Electrolyte> Ethylene carbonate (hereinafter sometimes abbreviated as "EC"), dimethyl carbonate (hereinafter sometimes abbreviated as "DMC"), and ethyl methyl carbonate (hereinafter sometimes abbreviated as "EMC") were mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This resulted in a mixed solvent as a non-aqueous solvent. LiPF as an electrolyte was added to the obtained mixed solvent. ６was dissolved so that the concentration in the finally obtained non-aqueous electrolyte solution was 1 mol / L, and an electrolyte solution (hereinafter sometimes abbreviated as "basic electrolyte solution") was obtained. To the obtained basic electrolyte solution, N,N'-di-i-propylcarbodiimide represented by the following formula (IA) (a type of carbodiimide compound represented by formula (I).) And methylene methanedisulfonate represented by the following formula (II-A) (a type of disulfonic acid ester compound represented by formula (II-1).) Each content relative to the total amount of the finally obtained non-aqueous electrolyte solution (a numerical value when the total amount of the non-aqueous electrolyte solution is 100 mass%) was added so that the content (mass%) shown in Table 1 was obtained, and a non-aqueous electrolyte solution was obtained. In Table 1, the contents of the carbodiimide compound and disulfonic acid ester compound in the non-aqueous electrolyte solution were listed in the "Content of each additive" column. In Table 1, in order to indicate that formula (IA) is one type of carbodiimide compound represented by formula (I), (I) is written in the column above (IA). Similarly, (II) is written in the column above (II-A).

[0156]

[0157] <Preparation of Positive Electrode> Li (Ni) was used as the positive electrode active material. ０．８ Co ０．１ Mn ０．１ O ２A mixture was obtained by adding 98% by mass of cellulose acetate, 1% by mass of carbon black as a conductive additive, and 1% by mass of polyvinylidene fluoride (PVdF) as a binder. The resulting mixture was dispersed in N-methylpyrrolidone solvent to obtain a slurry for a positive electrode composite. A 20 μm-thick aluminum foil was prepared as a positive electrode current collector. The resulting slurry for a positive electrode composite was applied to the aluminum foil, dried, and then rolled using a press to obtain a sheet-shaped positive electrode blank. This positive electrode blank included a region where a positive electrode active material composite layer (hereinafter referred to as the "positive electrode composite layer") was formed and a region where the positive electrode composite layer was not formed (hereinafter referred to as the "uncoated portion for tab bonding"). The uncoated portion for tab bonding was an uncoated portion that served as a margin. The resulting positive electrode blank was slit to obtain a positive electrode. The positive electrode had a positive electrode composite layer and an uncoated portion for tab bonding. The positive electrode mixture layer had a width of 29 mm and a length of 40 mm, and the uncoated portion for tab bonding had a width of 5 mm and a length of 11 mm.

[0158] <Negative Electrode Fabrication> Graphite (98% by mass) was used as the negative electrode active material, 1% by mass of sodium carboxymethylcellulose dispersed in pure water as a thickener (solids), and 1% by mass of styrene-butadiene rubber (SBR) dispersed in pure water as a binder (solids). A 16 μm-thick copper foil was prepared as the negative electrode current collector. The resulting negative electrode composite slurry was applied to the copper foil (negative electrode current collector), dried, and then rolled using a press to obtain a negative electrode blank. This negative electrode blank included a region where the negative electrode active material composite layer (hereinafter referred to as the "negative electrode composite layer") was formed and a region where the negative electrode composite layer was not formed (hereinafter referred to as the "uncoated portion for tab bonding"). The uncoated portion for tab bonding was the uncoated portion that served as a margin. The resulting negative electrode blank was slit to obtain a negative electrode. The negative electrode had a negative electrode composite layer and an uncoated portion for tab bonding. The negative electrode composite layer had a width of 30 mm and a length of 41 mm. The uncoated portion for tab bonding had a width of 5 mm and a length of 11 mm.

[0159] <Preparation of Separator> A porous polyethylene film was prepared as a separator.

[0160] <Fabrication of Laminated Battery> A laminate was obtained by stacking a positive electrode, a negative electrode, and a separator with the coated surface of the negative electrode in contact with the separator and the coated surface of the positive electrode in contact with the separator. An aluminum positive electrode tab (positive electrode lead) was then bonded to the uncoated tab-bonding portion of the positive electrode of the resulting laminate using an ultrasonic bonding machine. A nickel negative electrode tab (negative electrode lead) was then bonded to the uncoated tab-bonding portion of the negative electrode of the resulting laminate using an ultrasonic bonding machine. The laminate with the bonded positive and negative electrode tabs was sandwiched between a pair of laminate films (cases) with both aluminum surfaces coated with a resin layer, and then three sides were heat-sealed to obtain a laminate (assembly). In this case, the positive and negative electrode tabs were allowed to protrude from one of the three sealed sides of the laminate that was adjacent to the unsealed opening. Next, the nonaqueous electrolyte solution obtained above was poured into the opening of the laminate, and the opening of the laminate was sealed, thereby obtaining an aluminum laminate battery (electrochemical device precursor).

[0161] <Fabrication of Lithium-Ion Secondary Battery> The lithium-ion secondary battery precursor was charged to 1.5 V to 4.2 V, held for 5 to 50 hours, charged to 4.2 V, and discharged to 2.5 V, in this order, at a temperature range of 25° C. to 70° C., to obtain a lithium-ion secondary battery.

[0162] <Evaluation of Initial Low-Temperature Resistance Value> A lithium ion secondary battery was charged at 3.7 V and then cooled to −10°C in a thermostatic chamber. The DC resistance [Ω] was measured as the initial low-temperature resistance value (−10°C) based on the amount of voltage drop (= voltage before the start of discharge−voltage 10 seconds after the start of discharge) due to “CC10s discharge” at discharge rates of 0.1 C to 0.6 C and each current value (i.e., each current value corresponding to a discharge rate of 0.1 C to 0.6 C). Note that “CC10s discharge” here refers to discharging at a constant current for 10 seconds. The initial low-temperature resistance value (−10°C) of Comparative Example 1-1 described later was also measured using the same procedure. The initial low-temperature resistance value (−10°C) of Example 1-1 was calculated relative to the initial low-temperature resistance value (−10°C) of the lithium ion secondary battery of Comparative Example 1-1, which was set to 100, and this value was used as the “initial low-temperature resistance value (relative value).”

[0163] <Evaluation of Low-Temperature Resistance Values ​​After High-Temperature Storage> A lithium-ion secondary battery was charged to 4.2 V and stored in a thermostatic chamber at 60°C for 14 days (hereinafter, sometimes abbreviated as "high-temperature storage"). Next, the lithium-ion secondary battery after high-temperature storage was discharged to 3.7 V in a thermostatic chamber at 25°C and then cooled to -20°C in the thermostatic chamber. The DC resistance [Ω] was measured as the low-temperature resistance value (-20°C) after high-temperature storage based on the voltage drop (= voltage before the start of discharge - voltage 10 seconds after the start of discharge) due to "CC10s discharge" at discharge rates of 0.1 C to 0.6 C and each current value (i.e., each current value corresponding to a discharge rate of 0.1 C to 0.6 C). Note that CC10s discharge here refers to discharging at a constant current for 10 seconds. For Comparative Example 1-1 described later, the low-temperature resistance value (-20°C) after high-temperature storage was also measured by the same procedure, and the relative value of the low-temperature resistance value (-20°C) after high-temperature storage of Example 1-1, where the low-temperature resistance value (-20°C) after high-temperature storage of the lithium ion secondary battery of Comparative Example 1-1 was set to 100, was calculated and defined as the "low-temperature resistance value (-20°C, relative value) after high-temperature storage." The results are shown in Table 1.

[0164] Comparative Example 1-1 A lithium ion secondary battery was fabricated in the same manner as described in Example 1-1, except that the base electrolyte solution was used as is as the electrolyte solution without adding N,N'-di-i-propylcarbodiimide represented by formula (IA) and methylene methanedisulfonate represented by formula (II-A). Furthermore, the initial low-temperature resistance value and the low-temperature resistance value (-20°C) after high-temperature storage were measured in the same manner as described in Example 1-1, and these were used as the reference values ​​for the "initial low-temperature resistance value" and the "low-temperature resistance value (-20°C, relative value) after high-temperature storage" of Example 1-1, respectively. The results are shown in Table 1.

[0165] Example 1-2 A lithium ion secondary battery was fabricated in the same manner as in Example 1-1, except that the N,N'-di-i-propylcarbodiimide represented by formula (IA) was replaced with N,N'-dicyclohexylcarbodiimide represented by formula (IB). Furthermore, the initial low-temperature resistance value and the low-temperature resistance value (-20°C) after high-temperature storage were measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0166] Example 1-3 A lithium ion secondary battery was fabricated in the same manner as described in Example 1-1, except that the N,N'-di-i-propylcarbodiimide represented by formula (IA) was replaced with N,N'-bis(trimethylsilyl)carbodiimide represented by formula (IC). Furthermore, the initial low-temperature resistance value and the low-temperature resistance value (-20°C) after high-temperature storage were measured in the same manner as described in Example 1-1. The results are shown in Table 1.

[0167] Comparative Example 1-2 A lithium ion secondary battery was fabricated in the same manner as in Example 1-1, except that N,N'-di-i-propylcarbodiimide represented by formula (IA) was not added to the electrolyte solution. Furthermore, the initial low-temperature resistance value and the low-temperature resistance value (-20°C) after high-temperature storage were measured in the same manner as in Example 1-1. The results are shown in Table 1.

[0168]

[0169]

[0170] Example 2-1 Ethylene carbonate (hereinafter sometimes abbreviated as "EC"), dimethyl carbonate (hereinafter sometimes abbreviated as "DMC"), and ethyl methyl carbonate (hereinafter sometimes abbreviated as "EMC") were mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This resulted in a mixed solvent as a non-aqueous solvent. LiPF as an electrolyte was added to the obtained mixed solvent. ６was dissolved so that the concentration in the finally obtained non-aqueous electrolyte solution was 1 mol / L, and an electrolyte solution (hereinafter sometimes abbreviated as "basic electrolyte solution"). To the obtained basic electrolyte solution, N,N'-di-i-propylcarbodiimide represented by the following formula (IA) (one of the carbodiimide compounds represented by formula (I)), methylene methanedisulfonate represented by the following formula (II-A) (one of the disulfonic acid ester compounds represented by formula (II-1)), and a cyclic sulfate ester compound represented by the following formula (III-A) (one of the cyclic sulfate ester compounds represented by formula (III)) were added so that the contents (values ​​when the total amount of the non-aqueous electrolyte solution is 100% by mass) relative to the total amount of the finally obtained non-aqueous electrolyte solution were the contents (mass%) listed in Table 1, and a non-aqueous electrolyte solution was obtained. Then, a lithium ion secondary battery was produced by the same operation as described in Example 1-1. Furthermore, the low-temperature resistance value (-20°C) of the lithium ion secondary battery after high-temperature storage was measured by the same procedure as described in Example 1-1, and this was used as the reference value for "low-temperature resistance value (-20°C, relative value) after high-temperature storage" in Example 1-1. The results are shown in Table 2.

[0171]

[0172] Comparative Example 2-1 A lithium ion secondary battery was fabricated in the same manner as in Example 2-1, except that the carbodiimide compound represented by formula (IA) was not added to the electrolyte solution. Furthermore, the low-temperature resistance value (-20°C) of the lithium ion secondary battery after high-temperature storage was measured in the same manner as in Example 1-1, and this was used as the reference value for "low-temperature resistance value (-20°C, relative value) after high-temperature storage" in Example 2-1. The results are shown in Table 2.

[0173]

[0174] Example 3-1 A nonaqueous electrolyte solution was prepared by the same procedure as described in Example 2-1, except that each additive was added so that the content relative to the total amount of the nonaqueous electrolyte solution finally obtained (a value when the total amount of the nonaqueous electrolyte solution is 100% by mass) was the content (% by mass) shown in Table 3, and a lithium ion secondary battery was prepared. Furthermore, the low-temperature resistance value (-20°C) of the lithium ion secondary battery after high-temperature storage was measured by the same procedure as described in Example 1-1, and the relative value was calculated by setting the low-temperature resistance value (-20°C) of the lithium ion secondary battery after high-temperature storage of Comparative Example 3-1 after high-temperature storage (-20°C, relative value) as 100, and this was taken as the "low-temperature resistance value after high-temperature storage (-20°C, relative value)." The results are shown in Table 3.

[0175] Example 3-2 A nonaqueous electrolyte solution was prepared in the same manner as in Example 3-1, except that the N,N'-di-i-propylcarbodiimide represented by formula (IA) was replaced with N,N'-bis(trimethylsilyl)carbodiimide represented by formula (IC), and a lithium ion secondary battery was fabricated. Furthermore, the low-temperature resistance value (-20°C) of the lithium ion secondary battery after high-temperature storage was measured in the same manner as in Example 3-1, and the relative value was calculated by setting the low-temperature resistance value (-20°C) of the lithium ion secondary battery of Comparative Example 3-1 after high-temperature storage as 100, to obtain the "low-temperature resistance value (-20°C, relative value) after high-temperature storage." The results are shown in Table 3.

[0176] Comparative Example 3-1 A nonaqueous electrolyte solution was prepared in the same manner as in Example 3-1, except that N,N'-di-i-propylcarbodiimide represented by formula (IA) was not added, and a lithium ion secondary battery was fabricated. Furthermore, the low-temperature resistance value (-20°C) of the lithium ion secondary battery after high-temperature storage was measured in the same manner as in Example 1-1, and this was used as the reference value for the "low-temperature resistance value (-20°C, relative value) after high-temperature storage" in Examples 3-1 and 3-2. The results are shown in Table 3.

[0177]

[0178]

[0179] The symbol "-" in Tables 1, 2, and 3 indicates that the corresponding additive is not contained. The numerical values ​​(mass %) indicating the content in Tables 1, 2, and 3 indicate the content (mass %) of the additive relative to the total amount of the nonaqueous electrolyte (when the total amount of the nonaqueous electrolyte is taken as 100 mass %).

[0180] From the results in Tables 1, 2, and 3, it is clear that the lithium ion secondary batteries of Example 1-1 and the like, which use a non-aqueous electrolyte solution containing the carbodiimide compound represented by formula (I) and the disulfonic acid ester compound represented by formula (II-1) or formula (II-2), have a suppressed low-temperature resistance value after high-temperature storage, compared to the lithium ion secondary batteries of Comparative Example 1-1 and the like, which use a non-aqueous electrolyte solution not containing the carbodiimide compound represented by formula (I).

[0181] [Second Aspect] [Example 4-1] <Preparation of Non-Aqueous Electrolyte> Ethylene carbonate (hereinafter sometimes abbreviated as "EC"), dimethyl carbonate (hereinafter sometimes abbreviated as "DMC"), and ethyl methyl carbonate (hereinafter sometimes abbreviated as "EMC") were mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This resulted in a mixed solvent as a non-aqueous solvent. LiPF as an electrolyte was added to the obtained mixed solvent. ６ was dissolved so that the concentration in the finally obtained non-aqueous electrolyte solution was 1 mol / L, thereby obtaining an electrolyte solution (hereinafter sometimes abbreviated as "basic electrolyte solution"). N,N'-di-i-propylcarbodiimide represented by the following formula (IA) (one type of carbodiimide compound represented by formula (I)) was added to the obtained basic electrolyte solution so that the content (mass %) relative to the total amount of the finally obtained non-aqueous electrolyte solution (value when the total amount of the non-aqueous electrolyte solution is 100 mass %) was the content (mass %) shown in Table 4, thereby obtaining a non-aqueous electrolyte solution.

[0182]

[0183] <Preparation of Positive Electrode> LiNi was used as the positive electrode active material. ０．８８ Co ０．０９ Al ０．０３A mixture was obtained by adding 97% by mass of cellulose acetate, 1.5% by mass of acetylene black as a conductive additive, and 1.5% by mass of polyvinylidene fluoride (PVdF) as a binder. The resulting mixture was dispersed in an N-methylpyrrolidone solvent to obtain a positive electrode composite slurry. Aluminum foil with a thickness of 20 μm was prepared as a positive electrode current collector. The resulting positive electrode composite slurry was applied to aluminum foil, dried, and then rolled using a press to obtain a sheet-shaped positive electrode. The positive electrode consisted of a positive electrode current collector and a positive electrode composite layer.

[0184] <Preparation of Negative Electrode> Graphite (96% by mass) was used as the negative electrode active material, carbon black (1% by mass) was used as a conductive additive, 1% by mass of sodium carboxymethyl cellulose dispersed in pure water as a thickener (solid content), and 2% by mass of styrene-butadiene rubber (SBR) dispersed in pure water as a binder (solid content) were mixed to obtain a negative electrode composite slurry. A 10 μm thick copper foil was prepared as a negative electrode current collector. The obtained negative electrode composite slurry was applied to copper foil, dried, and then rolled in a press to obtain a sheet-shaped negative electrode. The negative electrode consisted of a negative electrode current collector and a negative electrode composite layer.

[0185] <Preparation of Separator> A porous polyethylene film was prepared as a separator.

[0186] <Preparation of Lithium-Ion Secondary Battery Precursor> The negative electrode, positive electrode, and separator were each punched into a disk shape with a diameter of 14 mm, 13 mm, and 17 mm, respectively. This resulted in a coin-shaped negative electrode, coin-shaped positive electrode, and coin-shaped separator, respectively. The resulting coin-shaped negative electrode, coin-shaped separator, and coin-shaped positive electrode were stacked in this order in a stainless steel battery can (size: 2032). Next, 20 μL of nonaqueous electrolyte was poured into the battery can, and the separator, positive electrode, and negative electrode were immersed in the nonaqueous electrolyte.

[0187] Next, an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were placed on the positive electrode, and the battery case lid was crimped via a polypropylene gasket to seal the battery.

[0188] As a result of the above, a coin-type lithium ion secondary battery precursor (i.e., a lithium ion secondary battery before being charged and discharged) was obtained. The lithium ion secondary battery precursor had a diameter of 20 mm and a height of 3.2 mm.

[0189] <Fabrication of Lithium-Ion Secondary Battery> The lithium-ion secondary battery precursor was charged to 1.5 V to 4.2 V, held for 5 to 50 hours, charged to 4.2 V, and discharged to 2.5 V, in this order, at a temperature range of 25° C. to 70° C., to obtain a lithium-ion secondary battery.

[0190] <Evaluation of Initial Low-Temperature Resistance Value> A lithium-ion secondary battery was charged at 3.7 V and then cooled to −10° C. in a thermostatic chamber. The DC resistance [Ω] was measured as the initial low-temperature resistance value (−20° C.) based on the amount of voltage drop (= voltage before the start of discharge−voltage 10 seconds after the start of discharge) due to “CC10s discharge” at discharge rates of 0.1 C to 0.6 C and each current value (i.e., each current value corresponding to a discharge rate of 0.1 C to 0.6 C). Here, “CC10s discharge” means discharging at a constant current for 10 seconds.

[0191] For Comparative Example 4-1 described later, the initial low-temperature resistance value (-20°C) was also measured by the same procedure, and the relative value of the initial low-temperature resistance value (-20°C) of Example 4-1, where the initial low-temperature resistance value (-20°C) of the lithium ion secondary battery of Comparative Example 4-1 was set to 100, was calculated and defined as the "initial low-temperature resistance value (relative value)."

[0192] Comparative Examples 4-1 and 4-2, Example 4-2 The same operation as in Example 4-1 was carried out, except that the type and content of the additive used in preparing the nonaqueous electrolyte solution were changed as shown in Table 4. In Example 4-2 and Comparative Example 4-2, fluoroethylene carbonate represented by the following formula (V-1) (a type of cyclic carbonate compound represented by formula (V)) was added.

[0193]

[0194]

[0195] As shown in Table 4, a comparison between Comparative Example 4-1 and Example 4-1, and a comparison between Comparative Example 4-2 and Example 4-2, reveals that when the carbodiimide compound represented by formula (I) is added, the initial battery resistance of a nonaqueous electrolyte secondary battery using a nickel-containing lithium composite oxide as a positive electrode active material can be kept low.

[0196] REFERENCE SIGNS LIST 1, 2 Lithium ion secondary battery precursor 10 Battery element 11 Positive electrode 11A Positive electrode current collector 11B Positive electrode composite layer 12 Negative electrode 12A Negative electrode current collector 12B Negative electrode composite layer 13 Separator 14 Single cell layer 21 Positive electrode lead 22 Negative electrode lead 30 Exterior body 41 Disk-shaped positive electrode 42 Disk-shaped negative electrode 43 Positive electrode can 44 Sealing plate 45 Separator 46 Gasket 47, 48 Spacer plate

[0197] The disclosures of Japanese Patent Application No. 2023-193840, filed on November 14, 2023, and Japanese Patent Application No. 2024-030692, filed on February 29, 2024, are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A non-aqueous electrolyte solution comprising a carbodiimide compound represented by the following formula (I) and a disulfonic acid ester compound represented by the following formula (II-1) or (II-2): [In formula (I), R １１ each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms. [In formulas (II-1) and (II-2), R ２１ and R ２２ each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ R represents a divalent hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of ２３ each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), a cyano group (-CN), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ ) represents a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of 2. The non-aqueous electrolyte according to claim 1, wherein the content of the carbodiimide compound is 0.001% by mass to 5.0% by mass based on the total amount of the non-aqueous electrolyte.

3. The non-aqueous electrolyte according to claim 1, wherein the content of the disulfonic acid ester compound is 0.01% by mass to 5.0% by mass based on the total amount of the non-aqueous electrolyte.

4. The nonaqueous electrolyte according to claim 1, further comprising a cyclic sulfate compound represented by the following formula (III): [In formula (III), R ３１ each independently represents a group represented by formula (iii-1), a group represented by formula (iii-2), a hydrogen atom (-H), or a substituent selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ R represents a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of ３２ is a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and as a substituent, a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an oxa group (-O-), a carbonyl group (>C=O), and a sulfonyl group (>S(=O) ２ a hydrocarbon group having 1 to 12 carbon atoms, a fluorocarbon group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a group represented by formula (iii-3), each of which may contain at least one functional group selected from the group consisting of 5. The non-aqueous electrolyte according to claim 4, wherein the content of the cyclic sulfate ester compound is 0.01% by mass to 5.0% by mass based on the total amount of the non-aqueous electrolyte.

6. A non-aqueous electrolyte solution containing a carbodiimide compound represented by the following formula (I-2): [In formula (I-2), R １２ each independently represents a hydrocarbon group having 1 to 6 carbon atoms.

7. A nonaqueous electrolyte used in a nonaqueous electrolyte secondary battery containing a nickel-containing lithium composite oxide as a positive electrode active material, the nonaqueous electrolyte containing a carbodiimide compound represented by the following formula (I): [In formula (I), R １１ each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms.

8. The non-aqueous electrolyte according to claim 7, wherein the total content of the carbodiimide compound represented by formula (I) is 0.001% by mass to 5.0% by mass based on the total amount of the non-aqueous electrolyte.

9. The non-aqueous electrolyte according to claim 7, wherein the total content of the carbodiimide compound represented by formula (I) is 0.001% by mass to 0.5% by mass based on the total amount of the non-aqueous electrolyte.

10. The non-aqueous electrolyte according to claim 7, wherein the total content of the carbodiimide compound represented by formula (I) is 0.001% by mass to 0.2% by mass based on the total amount of the non-aqueous electrolyte.

11. The nonaqueous electrolyte according to claim 7, wherein the nickel-containing lithium composite oxide is a composite oxide represented by the following formula (IV): Li ｘ Ni ｙ M ｚ O ２ ... (IV) (In formula (IV), M represents at least one atom selected from the group consisting of Co, Mn, and Al, x is a numerical value satisfying 0.95≦x≦1.15, and y and z are numerical values ​​satisfying 0.4≦y<1.0 and y+z=1.) 12. The nonaqueous electrolyte according to claim 7, further comprising a cyclic carbonate compound represented by the following formula (V): In formula (V), X represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I), R ５１ each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), or a hydrocarbon group having 1 to 12 carbon atoms which may contain at least one functional group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), an iodo group (-I), and an oxa group (-O-) as a substituent, and h represents an integer of 0 to 3.

13. A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator, wherein the nonaqueous electrolyte is the nonaqueous electrolyte according to any one of claims 1 to 12.

14. The nonaqueous electrolyte secondary battery according to claim 13, wherein the positive electrode comprises a positive electrode active material containing a nickel-containing lithium composite oxide.

15. The nonaqueous electrolyte secondary battery according to claim 14, wherein the nickel-containing lithium composite oxide is a composite oxide represented by the following formula (IV): Li ｘ Ni ｙ M ｚ O ２ ... (IV) (In formula (IV), M represents at least one atom selected from the group consisting of Co, Mn, and Al, x is a numerical value satisfying 0.95≦x≦1.15, and y and z are numerical values ​​satisfying 0.4≦y<1.0 and y+z=1.) 16. The nonaqueous electrolyte secondary battery according to claim 15, wherein the composite oxide represented by formula (IV) is a composite oxide represented by the following formula (IV-1): Li ｘ Ni ｙ M' ｚ’ A ｚ” O ２ ...(IV-1) (In formula (IV-1), M' represents at least one atom selected from the group consisting of Co and Mn, x is a numerical value satisfying 0.95≦x≦1.15, and y, z', and z" are numerical values ​​satisfying 0.4≦y<1.0 and y+z'+z"=1.)

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