Non-aqueous electrolyte and non-aqueous electrolyte secondary

Abstract

To provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery which improve a capacity retention rate after a charge / discharge cycle.SOLUTION: A nonaqueous electrolyte solution containing at least one fluorine-containing carbonate compound selected from the group consisting of a compound represented by the following formula (I-1) and a compound represented by the following formula (i- 2), and a cyclic sulfate compound represented by the following formula (II) can improve the capacity retention rate after charge-discharge cycles of a nonaqueous electrolyte secondary battery. Wherein the definitions of the groups are as defined in the description.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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, and as a result, they 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 satisfy specific requirements regarding various characteristics such as output characteristics and gas generation rate, but for example, excellent capacity retention after charge / discharge cycles is also a very important evaluation item.

[0003] Patent Document 1 discloses a nonaqueous electrolyte secondary battery having a nonaqueous electrolyte containing lithium bis(oxalato)borate and an unsaturated sultone compound, and reports that such a nonaqueous electrolyte secondary battery is excellent in cycle life performance and low-temperature discharge performance after cycling. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-179883 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one embodiment of the present disclosure is to provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery that improve the capacity retention rate after charge-discharge cycles. [Means for solving the problem]

[0006] As a result of extensive research aimed at solving the above problems, the present inventors have found that by blending a specific carbonate compound and a specific cyclic sulfate ester compound into a non-aqueous electrolyte, the capacity retention rate after charge-discharge cycling of a non-aqueous electrolyte secondary battery can be improved, and have completed the present invention. That is, one aspect of the invention according to the present disclosure includes the following. <1> A non-aqueous electrolyte solution containing at least one fluorine-containing carbonate compound selected from the group consisting of compounds represented by the following formula (I-1) and compounds represented by the following formula (I-2), and a cyclic sulfate ester compound represented by the following formula (II):

[0007] [ka]

[0008] (In formula (I-1), R 11 each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent, and x represents an integer of 1 to 4. 11 At least one of the groups is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent. In formula (I-2), R 12 each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent. 12At least one of the groups is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent.

[0009] [ka]

[0010] (In formula (II), R 21 represents a methylene group (-CH2-), an ethylene group (-CH2CH2-), or an n-propylene group (-CH2CH2CH2-), and R 22 each independently represents a hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of a halogeno group and an oxa group (—O—), and y represents R 21 When is a methylene group (-CH2-), 1 or 2 is used, and R 21 When R is an ethylene group (-CH2CH2-), an integer of 1 to 4 is used. 21 When is an n-propylene group (-CH2CH2CH2-), it represents an integer of 1 to 6.) <2> A non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery, comprising at least one selected from the group consisting of silicon particles, silicon oxide particles, and silicon carbide particles as a negative electrode active material. <1> The non-aqueous electrolyte solution according to claim 1. <3> the total content of the fluorine-containing carbonate compounds is 0.1% by mass to 30.0% by mass relative to the total amount of the nonaqueous electrolyte; <1> or <2> The non-aqueous electrolyte solution according to claim 1. <4> The total content of the cyclic sulfate ester compounds is 0.01% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte solution. <1> ~ <3> 10. The non-aqueous electrolyte solution according to claim 9, <5> Further, the composition contains an unsaturated cyclic carbonate compound represented by the following formula (III): <1> ~ <4> 10. The non-aqueous electrolyte solution according to claim 9,

[0011] [ka]

[0012] (In formula (III), R 31 each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent, and z represents an integer of 0 to 2. <6> A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, the negative electrode includes a current collector and a negative electrode mixture layer formed on the current collector and containing a negative electrode active material, the negative electrode active material including at least one selected from the group consisting of silicon simple particles, silicon oxide particles, and silicon carbide particles, and the nonaqueous electrolyte solution is <1> ~ <5> 10. A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte according to any one of claims 1 to 9. <7> 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; <6> The nonaqueous electrolyte secondary battery according to claim 1. <8> the total mass of at least one selected from the group consisting of the silicon simple particles, the silicon oxide particles, and the silicon carbide particles is 30% by mass or less when the total mass of the entire negative electrode active material is 100% by mass; <6> The nonaqueous electrolyte secondary battery according to claim 1. [Effects of the Invention]

[0013] According to one aspect of the present invention, it is possible to provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery that improve the capacity retention rate after charge-discharge cycles. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a precursor for a lithium secondary battery (nonaqueous electrolyte secondary battery) according to the present disclosure. [Figure 2]FIG. 2 is a schematic cross-sectional view showing a coin-type lithium secondary battery precursor, which is another example of a lithium secondary battery (nonaqueous electrolyte secondary battery) precursor according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] In explaining the invention according to the present disclosure, specific examples will be given, but the invention is not limited to the following content as long as it does not deviate from the spirit of the invention according to the present disclosure, and can be modified and implemented as appropriate.

[0016] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present disclosure, in the numerical ranges described in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified. In this disclosure, combinations of preferred aspects are more preferred aspects. 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.

[0017] <Nonaqueous electrolyte> A nonaqueous electrolyte solution according to one embodiment of the present invention according to the present disclosure (hereinafter may be abbreviated as "the nonaqueous electrolyte solution") contains at least one fluorine-containing carbonate compound (hereinafter may be abbreviated as "fluorine-containing carbonate compound") selected from the group consisting of compounds represented by the following formula (I-1) and compounds represented by the following formula (I-2), and a cyclic sulfate ester compound (hereinafter may be abbreviated as "cyclic sulfate ester compound") represented by the following formula (II):

[0018] [ka]

[0019] (In formula (I-1), R 11 each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent, and x represents an integer of 1 to 4. 11 At least one of the groups is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent.

[0020] In formula (I-2), R 12 each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent. 12 At least one of the groups is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent.

[0021] [ka]

[0022] (In formula (II), R 21 represents a methylene group (-CH2-), an ethylene group (-CH2CH2-), or an n-propylene group (-CH2CH2CH2-), and R 22each independently represents a hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (—O—), and y represents R 21 When is a methylene group (-CH2-), 1 or 2 is used, and R 21 When R is an ethylene group (-CH2CH2-), an integer of 1 to 4 is used. 21 When is an n-propylene group (-CH2CH2CH2-), it represents an integer of 1 to 6.)

[0023] As a result of extensive research into improving the capacity retention rate after charge-discharge cycling, the present inventors have found that by incorporating the above-mentioned fluorine-containing carbonate compound and the above-mentioned cyclic sulfate ester compound into a nonaqueous electrolyte solution, the capacity retention rate after charge-discharge cycling of a nonaqueous electrolyte secondary battery can be improved. Such a nonaqueous electrolyte solution can reduce not only the capacity retention rate after charge-discharge cycling but also the initial battery resistance and after charge-discharge cycling, making it possible to provide a nonaqueous electrolyte secondary battery with excellent practicality. Hereinafter, the fluorine-containing carbonate compounds "compounds represented by formula (I-1)", "compounds represented by formula (I-2)", "cyclic sulfate ester compounds represented by formula (II)" and the like will be described in detail.

[0024] [Fluorine-containing carbonate compound] (Compound represented by formula (I-1))

[0025] [ka]

[0026] R 11each independently represent a "fluoro group (-F)," a "fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent," 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) and an oxa group (-O-) as a substituent," and the term "fluorocarbon group" refers to a group in which all hydrogen atoms of the hydrocarbon group have been substituted with fluorine atoms. The term "fluorocarbon group" is also sometimes called a "fluorohydrocarbon group" or a "fluorocarbon group," and is a concept that includes perfluoroalkyl groups. The fluorocarbon group is not limited to a linear fluorocarbon group, but may also be a fluorocarbon 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). Furthermore, the "hydrocarbon group" is not limited to an aliphatic hydrocarbon group having a linear 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). Since the number of these structures is not limited, (acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups are all included in the "hydrocarbon group." Naturally, alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and the like are all included in the "hydrocarbon group." Furthermore, the phrase "may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent" means that a hydrogen atom of the hydrocarbon group may be substituted with a fluoro group (-F), and further, a carbon atom of the hydrocarbon group may be substituted with an oxa group (-O-). Furthermore, formula (I-1) represents a hydrocarbon group having a ring structure (-R) of ethylene carbonate. 11 ) group is inserted at a substitutable position of the ethylene carbonate structure. 11) group has been introduced. However, the substitutable position is specifically the ethylene group (-CH2CH2-) of the ethylene carbonate structure, and four hydrogen atoms of the ethylene group can be substituted, so the introduced (-R 11 ) groups, x is an integer between 1 and 4. That is, when x is 1, (-R 11 ) group is introduced, and when x is 4, (-R 11 ) groups are introduced. 11 at least one of which is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms which contains a fluoro group (-F) as a substituent, so the compound represented by formula (I-1) contains at least one fluoro group (-F).

[0027] R 11 When R is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. 11 When is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0028] R 11Examples include a fluoro group (-F), a trifluoromethyl group (-CF3), a pentafluoroethyl group (-C2F5), an n-heptafluoropropyl group (-C3F7), a pentafluorophenyl group (-C6F5), a trifluoromethoxy group (-OCF3), a pentafluoroethoxy group (-OC2F5), an n-heptafluoropropoxy group (-OC3F7), a pentafluorophenoxy group (-OC6F5), a fluoromethyl group (-CH2F), a difluoromethyl group (-CHF2), a 2,2,2-trifluoroethyl group (-CH2CF3), p-Fluorophenyl group (-CH6H4F), 2-trifluoromethoxyethyl group, methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), isopropyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH(CH3)CH2CH3), isobutyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)3), hexyl group (-CH2CH2CH2CH2CH2CH2CH3), cyclohexyl group (-CH 11 ), phenyl group (-C6H5), etc. Among these, a fluoro group (-F) is particularly preferred from the viewpoint of improving the capacity retention rate after charge-discharge cycles.

[0029] x represents an integer of 1 to 4, with 1 or 2 being preferred.

[0030] Examples of the compound represented by formula (I-1) include a compound represented by the following formula (I-1-1), a compound represented by the following formula (I-1-2), a compound represented by the following formula (I-1-3), a compound represented by the following formula (I-1-4), a compound represented by the following formula (I-1-5), a compound represented by the following formula (I-1-6), a compound represented by the following formula (I-1-7), a compound represented by the following formula (I-1-8), a compound represented by the following formula (I-1-9), a compound represented by the following formula (I-1-10), a compound represented by the following formula (I-1-11), etc. The non-aqueous electrolyte may contain two or more compounds represented by formula (I-1).

[0031] [ka]

[0032] (Compound represented by formula (I-2))

[0033] [ka]

[0034] R 12 each independently represents "a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent" 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) and an oxa group (-O-) as a substituent", but the terms "fluorocarbon group" and "hydrocarbon group" are used interchangeably in R 11 It is the same as the case of "R 12 At least one of R is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent. 12 At least one of the groups will contain a fluoro group (-F).

[0035] R 12 When R is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. 12 When is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0036] R 12Examples of the fluorocarbon group include trifluoromethyl group (-CF3), pentafluoroethyl group (-C2F5), n-heptafluoropropyl group (-C3F7), pentafluorophenyl group (-C6F5), trifluoromethoxy group (-OCF3), pentafluoroethoxy group (-OC2F5), n-heptafluoropropoxy group (-OC3F7), pentafluorophenoxy group (-OC6F5), fluoromethyl group (-CH2F), difluoromethyl group (-CHF2), 2,2,2-trifluoroethyl group (-CH2CF3), p -Fluorophenyl group (-C6H4F), 2-trifluoromethoxyethyl group, methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), isopropyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH(CH3)CH2CH3), isobutyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)3), hexyl group (-CH2CH2CH2CH2CH2CH2CH3), cyclohexyl group (-C6H 11 ), phenyl group (-C6H5), etc. Among these, the most popular are fluoro (-F), trifluoromethyl (-CF3), methyl (-CH3), ethyl (-CH2CH3), vinyl (-CH=CH2), n-propyl (-CH2CH2CH3), n-butyl (-CH2CH2CH2CH3), t-butyl (-C(CH3)3), hexyl (-CH2CH2CH2CH2CH2CH3), cyclohexyl (-CH6H 11 ), and a phenyl group (—C6H5) is particularly preferred.

[0037] Examples of the compound represented by formula (I-2) include a compound represented by the following formula (I-2-1), a compound represented by the following formula (I-2-2), a compound represented by the following formula (I-2-3), a compound represented by the following formula (I-2-4), a compound represented by the following formula (I-2-5), etc. The non-aqueous electrolyte may contain two or more types of compounds represented by formula (I-2).

[0038] [ka]

[0039] The total content of fluorine-containing carbonate compounds in the non-aqueous electrolyte is usually 0.1% by mass or more and 20.0% by mass or less, with the lower limit being preferably 0.2% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and particularly preferably 2% by mass or more, and the upper limit being preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 8% by mass or less, with the total content of these compounds within the above range, which makes it easier to improve the capacity retention rate after charge / discharge cycling, the initial battery resistance and the battery resistance after charge / discharge cycling, etc.

[0040] [Cyclic sulfate compound represented by formula (II)]

[0041] [ka]

[0042] R 21 represents a "methylene group (-CH2-)", an "ethylene group (-CH2CH2-)", or an "n-propylene group (-CH2CH2CH2-)", but R 21 is a methylene group (-CH2-), the cyclic sulfate ester compound represented by formula (II) is a four-membered ring, and R 21 is an ethylene group (-CH2CH2-), the cyclic sulfate ester compound represented by formula (II) is a five-membered ring, and R 21 is an n-propylene group (-CH2CH2CH2-), this means that the cyclic sulfate ester compound represented by formula (II) is a six-membered ring. R 21 As the alkyl group, an ethylene group (-CH2CH2-) is particularly preferred.

[0043] R 22each independently represents "a hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of a halogeno group and an oxa group (-O-)", and the "hydrocarbon group" is defined as R 11 The term "halogeno group" refers to a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I).

[0044] R 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.

[0045] R 22 Examples include methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), isopropyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH(CH3)CH2CH3), isobutyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)3), hexyl group (-CH2CH2CH2CH2CH2CH3), cyclohexyl group (-C6H 11 ), phenyl group (-C6H5), etc.

[0046] y is R 21 When is a methylene group (-CH2-), 1 or 2 is used, and R 21 When R is an ethylene group (-CH2CH2-), an integer of 1 to 4 is used. 21 When is an n-propylene group (-CH2CH2CH2-), it represents an integer of 1 to 6, and y is particularly preferably 1.

[0047] Examples of the cyclic sulfate ester compound represented by formula (II) include a cyclic sulfate ester compound represented by the following formula (II-1), a cyclic sulfate ester compound represented by the following formula (II-2), a cyclic sulfate ester compound represented by the following formula (II-3), a cyclic sulfate ester compound represented by the following formula (II-4), a cyclic sulfate ester compound represented by the following formula (II-5), and a cyclic sulfate ester compound represented by the following formula (II-6). The nonaqueous electrolyte may contain two or more types of cyclic sulfate ester compounds represented by formula (II).

[0048] [ka]

[0049] The total content of cyclic sulfate ester compounds in the non-aqueous electrolyte is typically 0.01% by mass or more and 10% by mass or less, with the lower limit being preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and particularly preferably 0.5% by mass or more, and the upper limit being preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, relative to the total amount of the non-aqueous electrolyte (assuming the total amount of the non-aqueous electrolyte is 100% by mass). When the total content of these compounds is within this range, it is easy to improve the capacity retention rate after charge-discharge cycling, the initial battery resistance and the battery resistance after charge-discharge cycling, etc.

[0050] (Unsaturated cyclic carbonate compound represented by formula (III)) The nonaqueous electrolyte preferably further contains an unsaturated cyclic carbonate compound represented by the following formula (III): By incorporating the unsaturated cyclic carbonate compound represented by formula (III), it becomes easier to further improve the capacity retention rate after charge-discharge cycling, the initial battery resistance and the battery resistance after charge-discharge cycling, etc.

[0051] [ka]

[0052] (In formula (III), R31 each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent, and z represents an integer of 0 to 2.

[0053] R 31 each independently represents a "fluoro group (-F)", a "fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent", 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) and an oxa group (-O-) as a substituent", but "fluorocarbon group", "hydrocarbon group", etc. are not included in R 11 Formula (III) is the same as the case where (-R 31 ) group is inserted at a substitutable position of the vinylene carbonate structure. 31 ) group is introduced. However, the substitutable position is specifically the vinylene group (-CH=CH-) of the vinylene carbonate structure, and two hydrogen atoms of the vinylene group can be substituted, so the introduced (-R 31 ) groups, z is an integer of 0 to 2.

[0054] R 31 When R is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. 31 When is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0055] R 31Examples include a fluoro group (-F), a trifluoromethyl group (-CF3), a pentafluoroethyl group (-C2F5), an n-heptafluoropropyl group (-C3F7), a pentafluorophenyl group (-C6F5), a trifluoromethoxy group (-OCF3), a pentafluoroethoxy group (-OC2F5), an n-heptafluoropropoxy group (-OC3F7), a pentafluorophenoxy group (-OC6F5), a fluoromethyl group (-CH2F), a difluoromethyl group (-CHF2), a 2,2,2-trifluoroethyl group (-CH2CF3), p-Fluorophenyl group (-CH6H4F), 2-trifluoromethoxyethyl group, methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), isopropyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH(CH3)CH2CH3), isobutyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)3), hexyl group (-CH2CH2CH2CH2CH2CH2CH3), cyclohexyl group (-CH 11 ), phenyl group (-C6H5), etc.

[0056] z represents an integer of 0 to 2, with 0 being preferred.

[0057] Examples of the unsaturated cyclic carbonate compound represented by formula (III) include an unsaturated cyclic carbonate compound represented by the following formula (III-1), an unsaturated cyclic carbonate compound represented by the following formula (III-2), an unsaturated cyclic carbonate compound represented by the following formula (III-3), an unsaturated cyclic carbonate compound represented by the following formula (III-4), an unsaturated cyclic carbonate compound represented by the following formula (III-5), an unsaturated cyclic carbonate compound represented by the following formula (III-6), and an unsaturated cyclic carbonate compound represented by the following formula (III-7). The non-aqueous electrolyte may contain two or more unsaturated cyclic carbonate compounds represented by formula (III).

[0058] [ka]

[0059] The total content of the unsaturated cyclic carbonate compounds represented by formula (III) in the non-aqueous electrolyte is usually 0.01% by mass or more and 10% by mass or less, with the lower limit being preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and particularly preferably 0.5% by mass or more, and the upper limit being preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, 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). If the total content of these compounds is within the above range, it is easy to improve the capacity retention rate after charge / discharge cycling, the initial battery resistance and the battery resistance after charge / discharge cycling, etc.

[0060] (non-aqueous solvent) The non-aqueous electrolyte generally contains a non-aqueous solvent (excluding the compound represented by formula (I-1), the compound represented by formula (I-2), and the compound represented by formula (III). Hereinafter, this may also be simply referred to as "non-aqueous solvent"). As the non-aqueous solvent, various known ones can be appropriately selected. The non-aqueous solvent may be one type only, or two or more types.

[0061] Examples of non-aqueous solvents include cyclic carbonates, fluorine-containing cyclic carbonates (excluding compounds represented by formula (I-1)), chain carbonates, fluorine-containing chain carbonates (excluding compounds represented by formula (I-2)), 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, and dimethyl sulfoxide phosphate. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC). 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 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 chain ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, and 1,2-dibutoxyethane. Examples of nitriles include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, and 3-methoxypropionitrile. Examples of amides include N,N-dimethylformamide. Examples of lactams include N-methylpyrrolidinone, N-methyloxazolidinone, and N,N'-dimethylimidazolidinone.

[0062] 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.

[0063] 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 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.

[0064] The upper limit of the non-aqueous solvent content is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 90% by mass or less, relative to the total amount of the non-aqueous electrolyte. The lower limit of the non-aqueous solvent content is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, relative to the total amount of the non-aqueous electrolyte.

[0065] The intrinsic viscosity of the non-aqueous solvent is preferably 10.0 mPa·s or less at 25° C., from the viewpoint of further improving the dissociation property of the electrolyte and the mobility of ions.

[0066] (electrolyte) The non-aqueous electrolyte generally contains an electrolyte.

[0067] 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.

[0068] Examples of the fluorine-containing lithium salt include inorganic acid anion salts and organic acid anion salts. Examples of inorganic acid anion salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium hexafluorotantalate (LiTaF6). Examples of organic acid anion salts include lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), and lithium bis(pentafluoroethanesulfonyl)imide (Li(C2F5SO2)2N). Among these, lithium hexafluorophosphate (LiPF6) is more preferable as the fluorine-containing lithium salt.

[0069] Fluorine-free lithium salts include lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), and lithium decachlorodecaborate (Li2B 10 Cl 10 ) etc.

[0070] 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. When the fluorine-containing lithium salt contains lithium hexafluorophosphate (LiPF6), the content of lithium hexafluorophosphate (LiPF6) 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.

[0071] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3.0 mol / L or less, and more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0072] When the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF6), the concentration of lithium hexafluorophosphate (LiPF6) in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3.0 mol / L or less, more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0073] <Nonaqueous electrolyte secondary battery> A nonaqueous electrolyte secondary battery according to another embodiment of the present invention is a nonaqueous electrolyte secondary battery including a "positive electrode," a "negative electrode," a "nonaqueous electrolyte," and a "separator." The "positive electrode," "negative electrode," "separator," etc. will be described in detail below.

[0074] (positive electrode) Typically, a positive electrode can be manufactured by dispersing a positive 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 current collector, drying, and compressing it to form a positive electrode composite layer (also referred to as a "positive electrode active material layer") on the current collector.

[0075] The positive electrode active material is transition metal oxides or sulfides such as MoS2, TiS2, MnO2, V2O5; LiCoO2, LiMnO2, LiMn2O4, LiNiO2, LiNi X Co (1-X) O2(0 <X<1)、LiNi x Co y Mn z O2 (x, y, and z are each independently greater than 0 and less than 1.00, and the sum of x, y, and z is 0.99 to 1.00) (so-called "NCM"; for example, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co0.1 Mn 0.1 Composite oxides composed of lithium and transition metals such as O2); Li t Ni 1-x-y Co x Al y O2 (where t is 0.95 or more and 1.15 or less, x is 0 or more and 0.3 or less, y is 0.1 or more and 0.2 or less, and the sum of x and y is less than 0.5.) (so-called "NCA"; for example, LiNi 0.8 Co 0.15 Al 0.05 Composite oxides composed of lithium, transition metals, and typical metals such as O2); Conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, and polyaniline composites; Lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium manganese iron phosphate (LiMn x Fe 1-x PO4; 0 < x < 1), lithium cobalt phosphate (LiCoPO4), lithium nickel phosphate (LiNiPO4), etc.; and the like.

[0076] Examples of the binder for the positive electrode include polyvinylidene fluoride, etc. Examples of the conductive assistant for the positive electrode include carbon black (e.g., acetylene black), amorphous whiskers, graphite, etc. Examples of the thickening agent for the positive electrode include carboxymethyl cellulose, etc. In addition, examples of the solvent for the slurry for forming the positive electrode include organic solvents such as N-methylpyrrolidone.

[0077] The total content of the positive electrode active material in the positive electrode composite layer is usually 70% to 97% by mass, preferably 75% or more and preferably 95% or less when the entire positive electrode composite layer is 100% by mass.

[0078] Examples of materials for the current collector of the positive electrode include aluminum, aluminum alloy, stainless steel, nickel, titanium, tantalum, carbon cloth, and carbon paper.

[0079] (Negative electrode) A negative electrode can usually be manufactured 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 current collector, drying, and compressing it to form a negative electrode composite layer (also called a "negative electrode active material layer") on the current collector.

[0080] The negative electrode active material may be classified into (1) 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, and carbides that can be doped / dedoped with lithium ions. When the negative electrode active material is silicon, a particulate (powder) type of silicon or compound is usually used. The negative electrode active material is not limited to one type, and two or more types may be mixed together.

[0081] 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) particles, carbon black particles, activated carbon particles, and amorphous carbon particles. Examples of artificial graphite include graphitized MCMB and graphitized MCF. Examples of amorphous carbon materials include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500°C or less, and mesophase pitch carbon fiber (MCF).

[0082] 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.

[0083] 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, preferably 10 μm or more, more preferably 15 μm or more, and preferably 25 μm or less, more preferably 20 μm or less.

[0084] 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~5.0m 2 / g, preferably 2.0m 2 / g or more, more preferably 3.0m 2 / g or more, preferably 4.5m 2 / g or less, more preferably 4.0m 2 / g or less.

[0085] 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, preferably 0.2 or more, more preferably 0.4 or more, even more preferably 0.6 or more, and preferably 1.8 or less, more preferably 1.6 or less, even more preferably 1.4 or less.

[0086] The median diameter D50 of the silicon particles, silicon oxide particles, or silicon carbide particles is usually 0.5 μm to 20 μm, preferably 1.0 μm or more, more preferably 3.0 μm or more, and preferably 15 μm or less, more preferably 10 μm or less.

[0087] The BET specific surface area of ​​silicon particles, silicon oxide particles, or silicon carbide particles is usually 1.0 m 2 / g~5.0m 2 / g, preferably 1.5m 2 / g or more, more preferably 2.0m 2 / g or more, preferably 4.5m 2 / g or less, more preferably 4.0m 2 / g or less.

[0088] 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 mass of the silicon particles, silicon oxide particles, and silicon carbide particles in the negative electrode active material is usually 1% by mass to 20% by mass, but is preferably 3% by mass or more, more preferably 5% by mass or more, and is preferably 18% by mass or less, more preferably 15% by mass or less, when the total mass of the entire negative electrode active material is taken as 100% by mass.

[0089] 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 mass of the carbon particles in the negative electrode active material is typically 70% by mass to 99% by mass, preferably 80% by mass or more, more preferably 85% by mass or more, and preferably 95% by mass or less, and more preferably 90% by mass or less, when the total mass of the entire negative electrode active material is taken as 100% by mass. When the total mass of the silicon particles and the like is within this range, it becomes easier to ensure a balance between the energy density and capacity retention rate of the lithium ion secondary battery.

[0090] 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, preferably 75% by mass or more, and preferably 99% by mass or less, when the entire negative electrode mixture layer is taken as 100% by mass.

[0091] Examples of binders for the negative electrode include styrene-butadiene rubber (SBR). The total content of the binder copolymer in the negative electrode mixture layer is usually 0.1% by mass to 5% by mass, but is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and is preferably 3% by mass or less, more preferably 2% by mass or less, when the entire negative electrode mixture layer is taken as 100% by mass.

[0092] The negative electrode mixture layer preferably further contains a conductive additive such as carbon black (for example, acetylene black), carbon nanotubes, amorphous whiskers, and graphite.

[0093] The total content of the conductive additive in the negative electrode mixture layer is usually 0.01% by mass to 3% by mass, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and is preferably 2% by mass or less, more preferably 1% by mass or less, when the entire negative electrode mixture layer is taken as 100% by mass.

[0094] 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.

[0095] The total content of the thickener in the negative electrode mixture layer is usually 0.1% by mass to 5% by mass, but is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and is preferably 3% by mass or less, more preferably 2% by mass or less, when the entire negative electrode mixture layer is taken as 100% by mass.

[0096] The slurry may contain a solvent, such as water, acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, or ethylenediamine. The solvent may be a mixed solvent of the above-mentioned solvents.

[0097] Examples of materials for the current collector of the negative electrode include copper, nickel, stainless steel, and nickel-plated steel.

[0098] <Separator> The nonaqueous electrolyte secondary battery according to one embodiment of the present invention is a nonaqueous electrolyte secondary battery comprising a "positive electrode," a "negative electrode," a "nonaqueous electrolyte," and a "separator." The separator may be a porous resin flat plate. 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, and polyamide. In particular, the separator is preferably a porous resin sheet having a single layer or a multilayer structure. The porous resin sheet is mainly made 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.

[0099] <Case> The shape of the case is not particularly limited and may be appropriately selected depending on the intended use of the lithium secondary battery precursor of the present disclosure. Examples of the case include a case including a laminate film, and a case consisting of a battery can and a battery can lid.

[0100] <Specific examples of lithium secondary battery precursors> FIG. 1 is a schematic cross-sectional view showing a laminated lithium secondary battery precursor, which is an example of the lithium secondary battery precursor of the present disclosure.

[0101] As shown in FIG. 1, a lithium secondary battery precursor 1 is a laminated type battery precursor. Specifically, in the lithium secondary battery precursor 1, the 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.

[0102] As shown in FIG. 1 , battery element 10 is formed by laminating positive electrode 11, separator 13, and negative electrode 12. Positive electrode 11 has positive electrode composite layer 11B formed on both main surfaces of positive electrode current collector 11A. Negative electrode 12 has negative electrode composite layer 12B formed on both main surfaces of 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.

[0103] The nonaqueous electrolyte solution of the present disclosure is poured into the interior of the exterior housing 30 of the lithium 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 secondary battery precursor 1, one unit 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.

[0104] Although the lithium secondary battery precursor 1 is a laminated lithium secondary battery precursor, the lithium secondary battery precursor of the present disclosure is not limited thereto and may be, for example, a wound lithium secondary battery precursor. A wound lithium 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 lithium secondary battery precursors include cylindrical lithium secondary battery precursors and prismatic lithium secondary battery precursors.

[0105] 1 , in the lithium secondary battery precursor 1, the directions in which the positive electrode lead and the negative electrode lead each protrude from the inside to the outside of the exterior body 30 are opposite directions relative to the exterior body 30, but the present disclosure is not limited to this. For example, the directions in which the positive electrode lead and the negative electrode lead each protrude from the inside to the outside of the exterior body 30 may be the same direction relative to the exterior body 30.

[0106] An example of the lithium secondary battery of the present disclosure, which will be described later, is a lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor 1.

[0107] FIG. 2 is a schematic cross-sectional view showing a coin-type lithium secondary battery precursor, which is another example of the lithium secondary battery precursor of the present disclosure.

[0108] 2, a disc-shaped negative electrode 42, a separator 45 filled with a non-aqueous electrolyte, a disc-shaped positive electrode 41, and, if necessary, spacer plates 47 and 48 made of stainless steel, aluminum, or the like are stacked in this order and 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 with a gasket 46 interposed therebetween. In this example, the nonaqueous electrolyte of the present disclosure is used as the nonaqueous electrolyte injected into separator 45 .

[0109] An example of the lithium secondary battery of the present disclosure, which will be described later, is a lithium secondary battery obtained by charging and discharging the coin-type lithium secondary battery precursor shown in FIG.

[0110] [Lithium secondary battery and manufacturing method thereof] The method for producing a lithium secondary battery according to the present disclosure includes: a step of preparing the lithium secondary battery precursor of the present disclosure (hereinafter also referred to as a "preparation step"); charging and discharging the lithium secondary battery precursor; Includes: The lithium secondary battery of the present disclosure is a lithium secondary battery obtained by charging and discharging the above-described lithium secondary battery precursor of the present disclosure.

[0111] According to the lithium secondary battery and the method for producing the same disclosed herein, it is possible to reduce the room temperature resistance increase rate of the lithium secondary battery when stored at high temperatures.

[0112] The preparation step may be a step of simply preparing a previously manufactured lithium secondary battery precursor of the present disclosure for a step of charging and discharging, or may be a step of manufacturing a lithium secondary battery precursor of the present disclosure. The lithium secondary battery precursor is as described above.

[0113] In the step of charging and discharging, the lithium secondary battery precursor can be charged and discharged according to a known method. In this step, the lithium secondary battery precursor may be subjected to a cycle of charging and discharging multiple times. 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 negative electrode (particularly the negative electrode active material) in the lithium secondary battery precursor.

[0114] In the step of charging and discharging, the lithium 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. [Example]

[0115] Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples. Hereinafter, "%" means "% by mass" unless otherwise specified.

[0116] Example 1 <Preparation of non-aqueous electrolyte> Ethylene carbonate (hereinafter "EC"), dimethyl carbonate (hereinafter "DMC"), and ethyl methyl carbonate (hereinafter "EMC") were mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This resulted in a mixed solvent as a nonaqueous solvent. LiPF6 as an electrolyte was dissolved in the resulting mixed solvent so that the concentration in the final nonaqueous electrolyte solution would be 1.0 mol / L, thereby obtaining an electrolyte solution (hereinafter also referred to as a "basic electrolyte solution"). A compound represented by the following formula (I-1-1) was added to the resulting basic electrolyte solution so that the content was 5.0 mass% relative to the total amount of the final nonaqueous electrolyte solution, a cyclic sulfate ester compound represented by the following formula (II-1) was added to the resulting basic electrolyte solution so that the content was 0.5 mass% relative to the total amount of the nonaqueous electrolyte solution, and an unsaturated cyclic carbonate compound represented by the following formula (III-1) was added to the resulting nonaqueous electrolyte solution so that the content was 1.0 mass% relative to the total amount of the nonaqueous electrolyte solution.

[0117] [ka]

[0118] <Preparation of positive electrode> LiNi as a positive electrode active material 0.8 Co 0.1 Mn 0.1 A mixture was obtained by mixing O2 (94% by mass), carbon black (3% by mass) as a conductive additive, and polyvinylidene fluoride (PVdF) (3% by mass) as a binder. The obtained mixture was dispersed in 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 obtained positive electrode composite slurry was applied to aluminum foil, dried, and then rolled in a press to obtain a sheet-shaped positive electrode. The positive electrode consisted of a positive electrode current collector and a positive electrode active material layer.

[0119] <Preparation of negative electrode> The negative electrode active material was 87.3 mass% graphite and silicon oxide (SiO x(x=1), 9.7 mass% silicon monoxide, 1.5 mass% solids of sodium carboxymethyl cellulose dispersed in pure water as a thickener, and 1.5 mass% solids of styrene-butadiene rubber (SBR) dispersed in pure water as a binder were mixed to obtain a negative electrode composite slurry. Copper foil with a thickness of 10 μm 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 active material layer.

[0120] <Preparing the separator> A porous polyethylene film was prepared as a separator.

[0121] <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. Next, an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were placed on the positive electrode, and the battery can lid was crimped via a polypropylene gasket to seal the battery. This resulted in a coin-shaped lithium ion secondary battery precursor (i.e., a lithium ion secondary battery before charging and discharging) having the configuration shown in FIG. 2. The lithium ion secondary battery precursor had a diameter of 20 mm and a height of 3.2 mm.

[0122] <Fabrication of lithium-ion secondary batteries> The lithium ion secondary battery precursor was charged to 4.2 V and discharged to 2.5 V three times in a temperature range of 25° C. to 70° C. to obtain a lithium ion secondary battery.

[0123] <Measurement of initial discharge capacity> The lithium ion secondary battery was charged to 4.2 V in a thermostatic bath at 25° C., and then discharged to 2.5 V, and the discharge capacity [mAh] (hereinafter also referred to as "initial discharge capacity") was measured.

[0124] <Measurement of initial resistance> After measuring the initial discharge capacity, the lithium-ion secondary batteries were charged to 3.7 V, and then measured for each voltage drop (= voltage before discharge started - voltage 10 seconds after discharge started) due to CC10s discharge at discharge rates of 0.1 C to 1.0 C in thermostatic chambers at 25°C and -20°C. CC10s discharge refers to discharge at a constant current for 10 seconds. Based on the obtained voltage drop and each current value (i.e., each current value corresponding to a discharge rate of 0.1 C to 1.0 C), DC resistance [Ω] was measured as the initial resistance value.

[0125] <Charge / discharge cycle test> Next, the lithium ion secondary battery after measuring the initial resistance was charged at a constant current of 0.5 C to 4.2 V in a thermostatic chamber at 25° C. Then, it was discharged at a constant current of 0.5 C to 2.5 V. The above charge / discharge cycle was repeated 100 times.

[0126] <Measurement of discharge capacity retention rate after charge / discharge cycles and calculation of relative value> Next, the discharge capacity of the lithium ion secondary battery after the charge-discharge cycle test was measured in the same manner as the initial discharge capacity. The discharge capacity of the lithium ion secondary battery after the charge-discharge cycle test was also measured in the same manner for Comparative Example 1 described below. The discharge capacity retention rate after the charge-discharge cycle of Example 1 was calculated as a relative value when the discharge capacity retention rate after the charge-discharge cycle of Comparative Example 1 was set to 100 (see the following formula). Discharge capacity retention rate after charge-discharge cycles in Example 1 (relative value)=(Discharge capacity retention rate after charge-discharge cycles in Example 1) / (Discharge capacity retention rate after charge-discharge cycles in Comparative Example 1)×100

[0127] <Measurement of resistance increase rate after charge / discharge cycle and calculation of relative value> Next, the resistance value of the lithium ion secondary battery after the charge-discharge cycle test was measured in the same manner as for the initial resistance value. The resistance value of the lithium ion secondary battery after the charge-discharge cycle test was also measured in the same manner for Comparative Example 1 described below. The resistance increase rate after the charge-discharge cycle of Example 1 was calculated as a relative value when the resistance increase rate after the charge-discharge cycle of Comparative Example 1 was set to 100 (see the following formula). Resistance increase rate after charge-discharge cycles in Example 1 (relative value)=(resistance increase rate after charge-discharge cycles in Example 1) / (resistance increase rate after charge-discharge cycles in Comparative Example 1)×100

[0128] [Comparative Examples 1 and 2] The same procedure as in Example 1 was carried out, except that the type and content of the additives used in preparing the non-aqueous electrolyte solution were changed as shown in Table 1. The results are shown in Table 1. The additives added to the non-aqueous electrolyte solutions of Comparative Examples 1 and 2 are as shown below. In Table 1, "-" indicates that no additive was added. DTD: 1,3,2-dioxathiolane 2,2-dioxide

[0129] [ka]

[0130] [Table 1]

[0131] As is clear from Table 1, the lithium ion secondary battery using a nonaqueous electrolyte solution containing the fluorine-containing carbonate compound represented by formula (I-1) and the cyclic sulfate ester compound represented by formula (II) has an improved capacity retention rate after charge-discharge cycling. Specifically, in Example 1, the capacity retention rate after charge-discharge cycling was improved compared to the lithium ion secondary batteries of Comparative Examples 1 and 2, which did not contain the cyclic sulfate ester compound represented by formula (II).In addition, a decrease in the initial resistance value and the rate of increase in resistance was also observed. [Explanation of symbols]

[0132] 1. Lithium 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 Cell layer 21 Positive lead 22 Negative lead 30 Exterior body 41 Positive electrode 42 Negative electrode 43 Positive electrode can 44 Sealing plate 45 Separator 46 Gasket 47, 48 Spacer plates

Claims

1. A non-aqueous electrolyte solution containing at least one fluorine-containing carbonate compound selected from the group consisting of compounds represented by the following formula (I-1) and compounds represented by the following formula (I-2), and a cyclic sulfate ester compound represented by the following formula (II): 【Chemistry 1】 (In formula (I-1), R １１ each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent, and x represents an integer of 1 to 4. １１ At least one of the groups is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent. In formula (I-2), R １２ each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent. １２ At least one of is a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms and containing a fluoro group (-F) as a substituent. 【Chemistry 2】 (In formula (II), R ２１ is a methylene group (-CH ２ -), ethylene group (-CH ２ CH ２ -), or n-propylene group (-CH ２ CH ２ CH ２ -), and R ２２ each independently represents a hydrocarbon group having 1 to 6 carbon atoms which may contain at least one functional group selected from the group consisting of a halogeno group and an oxa group (—O—), and y represents R ２１ is a methylene group (-CH ２ -) then 1 or 2, R ２１ is an ethylene group (-CH ２ CH ２ -), an integer from 1 to 4 is used, R ２１ is an n-propylene group (-CH ２ CH ２ CH ２ -) represents an integer between 1 and 6.

2. 2. The nonaqueous electrolyte according to claim 1, which is used in a nonaqueous electrolyte secondary battery and contains, as a negative electrode active material, at least one selected from the group consisting of silicon particles, silicon oxide particles, and silicon carbide particles.

3. 2. The non-aqueous electrolyte according to claim 1, wherein the total content of the fluorine-containing carbonate compounds is 0.1% by mass to 30.0% by mass based on the total amount of the non-aqueous electrolyte.

4. 2. The non-aqueous electrolyte according to claim 1, wherein the total content of the cyclic sulfate ester compounds is 0.01% by mass to 10% by mass based on the total amount of the non-aqueous electrolyte.

5. The nonaqueous electrolyte solution according to claim 1 , further comprising an unsaturated cyclic carbonate compound represented by the following formula (III): 【Transformation 3】 (In formula (III), R ３１ each independently represents a fluoro group (-F), a fluorocarbon group having 1 to 12 carbon atoms which may contain an oxa group (-O-) as a substituent, 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) and an oxa group (-O-) as a substituent, and z represents an integer of 0 to 2.

6. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, the negative electrode includes a current collector and a negative electrode mixture layer formed on the current collector and containing a negative electrode active material, the negative electrode active material contains at least one selected from the group consisting of silicon particles, silicon oxide particles, and silicon carbide particles, A nonaqueous electrolyte secondary battery, wherein the nonaqueous electrolyte is the nonaqueous electrolyte according to any one of claims 1 to 5.

7. 7. The nonaqueous electrolyte secondary battery according to claim 6, wherein the negative electrode active material comprises particles of pure carbon and at least one selected from the group consisting of particles of pure silicon, silicon oxide, and silicon carbide.

8. 7. The nonaqueous electrolyte secondary battery according to claim 6, wherein the total mass of the at least one selected from the group consisting of the silicon particles, the silicon oxide particles, and the silicon carbide particles is 30% by mass or less, when the total mass of the entire negative electrode active material is 100% by mass.

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