Non-aqueous electrolyte and non-aqueous electrolyte secondary battery

Abstract

This non-aqueous electrolyte contains: at least one carbonate compound selected from the group consisting of a compound represented by the following formula (I-1), a compound represented by the following formula (I-2), and a compound represented by the following formula (I-3); and at least one sulfonyl compound selected from the group consisting of a compound represented by the following formula (II) and a compound represented by the following formula (III). The definition of each group in each formula is as described in the description.

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, 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 meet specific requirements regarding various characteristics such as output characteristics, charge / discharge characteristics, and gas generation, but for example, capacity retention after charge / discharge cycle testing and output characteristics are also very important evaluation items.

[0003] Patent Document 1 describes a nonaqueous electrolyte secondary battery that uses a specific cyclic carbonate such as 4,5-difluoro-1,3-dioxolane-2-one as the nonaqueous solvent, and reports that the battery has improved cycle characteristics, and further that the specific cyclic carbonate does not solidify even at temperatures as low as 0° C., thereby improving the battery's cycle characteristics at low temperatures. Patent Document 2 describes a nonaqueous electrolyte that uses trifluoropropylene carbonate, and reports that the battery has improved performance compared to when ethylene carbonate or propylene carbonate is used.

[0004] Patent Document 1: Japanese Patent Application Publication No. 7-240232 Patent Document 2: Japanese Patent Application Publication No. 8-37025

[0005] An object of one embodiment of the present disclosure is to provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery that exhibit excellent battery characteristics after charge-discharge cycles.

[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 sulfonyl compound into a non-aqueous electrolyte solution, it is possible to improve the capacity retention rate and the resistance increase rate of a non-aqueous electrolyte secondary battery after charge-discharge cycling, and have completed the present invention.

[0007] That is, one aspect of the present disclosure includes the following: <1> A nonaqueous electrolyte solution containing at least one carbonate compound selected from the group consisting of compounds represented by the following formula (I-1), compounds represented by the following formula (I-2), and compounds represented by the following formula (I-3), and at least one sulfonyl compound selected from the group consisting of compounds represented by the following formula (II) and compounds represented by the following formula (III).

[0008]

[0009] (In formula (I-1), R １１ 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, and x represents an integer of 1 to 4. １１ At least one of the groups is the fluorocarbon group or the hydrocarbon group containing a fluoro group (—F) as a substituent. 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, and y represents an integer of 1 to 3. In formula (I-3), R １３ 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. １３ At least one of the groups is the fluorocarbon group or the hydrocarbon group containing a fluoro group (—F) as a substituent.

[0010]

[0011] (In formula (II), R ２１represents a group represented by formula (ii-1), a group represented by formula (ii-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms. ２２ is an oxymethylene group (-OCH ２ -), oxyethylene group (-OCH ２ CH ２ In formula (ii-2), R represents an oxa group (—O—), or a divalent hydrocarbon group having 1 to 6 carbon atoms. ２３ represents a hydrocarbon group having 1 to 8 carbon atoms or a hydrogen atom (—H). ３ 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 contains a fluoro group (-F) as a substituent and may also contain an oxa group (-O-) as a substituent, and (M ３ ) ＋represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion.) <2> The nonaqueous electrolyte solution according to <1>, which is used for a nonaqueous electrolyte secondary battery, containing, as a negative electrode active material, at least one selected from the group consisting of silicon simple particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component. <3> The nonaqueous electrolyte solution according to <1> or <2>, in which the total content of the carbonate compound is 0.1% by mass to 10.0% by mass, based on the total amount of the nonaqueous electrolyte. <4> The nonaqueous electrolyte solution according to any one of <1> to <3>, in which the total content of the sulfonyl compound is 0.01% by mass to 5.0% by mass, based on the total amount of the nonaqueous electrolyte. <5> A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, wherein the negative electrode comprises a current collector and a negative electrode composite layer formed on the current collector and containing a negative electrode active material, the negative electrode active material comprises at least one selected from the group consisting of simple silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component, and the non-aqueous electrolyte is the non-aqueous electrolyte solution according to any one of <1> to <4>. <6> The non-aqueous electrolyte secondary battery according to <5>, wherein the negative electrode active material comprises simple carbon particles and at least one selected from the group consisting of simple silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component. <7> The nonaqueous electrolyte secondary battery according to <5>, wherein the total mass of at least one selected from the group consisting of the silicon simple particles, the silicon oxide particles, the silicon carbide particles, and the composite particles is 30 mass% or less when the total mass of the entire negative electrode active material is 100 mass%.

[0012] According to one aspect of the present invention, it is possible to improve the capacity retention rate and the resistance increase rate of a non-aqueous electrolyte secondary battery after charge-discharge cycling.

[0013] 1 is a schematic cross-sectional view showing an example of a lithium secondary battery precursor according to an embodiment of the present disclosure, and FIG. 2 is a schematic cross-sectional view showing an example of a coin-type battery, which is another example of the lithium secondary battery according to the present disclosure.

[0014] 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.

[0015] 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 numerical range described in stages. 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 in the composition means the total amount of those multiple substances present in the composition, unless otherwise specified. In the present disclosure, a combination of preferred embodiments is a more preferred embodiment. In the present disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0016] <Non-aqueous Electrolyte> A non-aqueous electrolyte according to one embodiment of the present disclosure (hereinafter may be abbreviated as "the non-aqueous electrolyte") contains at least one carbonate compound (hereinafter may be abbreviated as "carbonate compound") selected from the group consisting of compounds represented by the following formula (I-1), compounds represented by the following formula (I-2), and compounds represented by the following formula (I-3), and at least one sulfonyl compound (hereinafter may be abbreviated as "sulfonyl compound") selected from the group consisting of compounds represented by the following formula (II) and compounds represented by the following formula (III).

[0017]

[0018] In formula (I-1), R １１each 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, and x represents an integer of 1 to 4. １１ At least one of the groups is the fluorocarbon group or the hydrocarbon group containing a fluoro group (—F) as a substituent. 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, and y represents an integer of 1 to 3. In formula (I-3), R １３ 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. １３ At least one of the groups is the above-mentioned fluorocarbon group or the above-mentioned hydrocarbon group containing a fluoro group (—F) as a substituent.

[0019]

[0020] In formula (II), R ２１ represents a group represented by formula (ii-1), a group represented by formula (ii-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms. ２２ is an oxymethylene group (-OCH ２ -), oxyethylene group (-OCH ２ CH ２ In formula (ii-2), R represents an oxa group (—O—), or a divalent hydrocarbon group having 1 to 6 carbon atoms. ２３ represents a hydrocarbon group having 1 to 8 carbon atoms or a hydrogen atom (—H). ３represents 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 and may also contain an oxa group (-O-) as a substituent, and (M ３ ) ＋ represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion.

[0021] The present inventors have conducted extensive research into nonaqueous electrolyte secondary batteries with excellent battery characteristics after charge-discharge cycling, and as a result have found that by incorporating the above-mentioned carbonate compound and the above-mentioned sulfonyl compound into a nonaqueous electrolyte, it is possible to improve the capacity retention rate and resistance increase rate of a nonaqueous electrolyte secondary battery after charge-discharge cycling. Hereinafter, carbonate compounds such as "compounds represented by formula (I-1)," "compounds represented by formula (I-2)," and "compounds represented by formula (I-3)," and sulfonyl compounds such as "compounds represented by formula (II)" and "compounds represented by formula (III)," will be described in detail.

[0022] [Carbonate Compound] (Compound represented by formula (I-1))

[0023]

[0024] R １１each independently represent "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." The term "fluorocarbon group" refers to a group in which all hydrogen atoms of a hydrocarbon group have been substituted with fluorine atoms, and is sometimes called a "fluorohydrocarbon group" or a "fluorocarbon group." The term also encompasses perfluoroalkyl groups. The fluorocarbon group is not limited to a fluorocarbon group having a linear structure, 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 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). Furthermore, 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 of ethylene carbonate (-R １１ ) group is inserted at a substitutable position of the ethylene carbonate structure. １１ ) group is introduced. However, the substitutable position is specifically the ethylene group (—CH ２ H ２-), and four hydrogen atoms of the ethylene group can be substituted, so the introduced (-R １１ The x representing the number of (-R １１ ) group is introduced, and the ethylene group is replaced by (—C(R １１ ) HCH ２ -), and when x is 4, it becomes (-R １１ ) groups are introduced, and the above-mentioned ethylene group is replaced by (—C(R １１ ) ２ C (R １１ ) ２ -) and "R １１ is the fluorocarbon group or the hydrocarbon group containing a fluoro group (-F) as a substituent, and the term "the hydrocarbon group containing a fluoro group (-F)" means that the aforementioned "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" is a group containing at least one fluoro group (-F). １１ At least one of the groups will contain a fluoro group (—F).

[0025] 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.

[0026] R １１ The fluorocarbon group is a trifluoromethyl group (-CF ３ ), a pentafluoroethyl group (—C ２ F ５ ), n-heptafluoropropyl group (—C ３ F ７ ), a pentafluorophenyl group (—C ６ F ５ ), a trifluoromethoxy group (—OCF ３ ), a pentafluoroethoxy group (—OC ２ F５ ), 3-trifluoromethoxyhexafluoropropyl group, etc. １１ As the hydrocarbon group, a fluoromethyl group (-CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (—CH ２ CF ３ ), a pentafluorophenoxy group (—OC ６ F ５ ), p-fluorophenyl group (—C ６ H ４ Among these, from the viewpoint of improving the capacity retention rate and the resistance increase rate after charge-discharge cycling, a trifluoromethyl group (-CF ３ ) is particularly preferred.

[0027] x represents an integer of 1 to 4, preferably 1 or 2.

[0028] Examples of the compound represented by formula (I-1) include compounds represented by the following formula: The non-aqueous electrolyte may contain two or more types of compounds represented by formula (I-1).

[0029]

[0030] (Compound represented by formula (I-2))

[0031]

[0032] 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", but the "fluorocarbon group" and the "hydrocarbon group" are not included in the R １１ In addition, the cyclic structure of ethylene carbonate in formula (I-2) has the same meaning as in the case of (—R １２ ) groups are also included in the R １１ is the same as in

[0033] R１２ 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.

[0034] R １２ Examples of the fluoro group include a fluoro group (-F), a trifluoromethyl group (-CF ３ ), a pentafluoroethyl group (—C ２ F ５ ), n-heptafluoropropyl group (—C ３ F ７ ), a pentafluorophenyl group (—C ６ F ５ ), a trifluoromethoxy group (—OCF ３ ), a pentafluoroethoxy group (—OC ２ F ５ ), n-heptafluoropropoxy group (—OC ３ F ７ ), a pentafluorophenoxy group (—OC ６ F ５ ), a fluoromethyl group (—CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (—CH ２ CF ３ ), p-fluorophenyl group (—C ６ H ４ F), 2-trifluoromethoxyethyl group, methyl group (—CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), an isopropyl group (-CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), s-butyl group (—CH ２CH (CH ３ ) ２ ), isobutyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ３ ), 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 Among these, a fluoro group (—F) is particularly preferred from the viewpoint of improving the capacity retention rate and the resistance increase rate after charge / discharge cycling.

[0035] y represents an integer of 1 to 3, with 1 being preferred.

[0036] Examples of the compound represented by formula (I-2) include compounds represented by the following formula: The non-aqueous electrolyte may contain two or more types of compounds represented by formula (I-2).

[0037]

[0038] (Compound represented by formula (I-3))

[0039]

[0040] R １３ each independently represents "a fluorocarbon group having 1 to 10 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 with R １１ This is the same as the case of "R １３ At least one of the hydrocarbon groups is the fluorocarbon group or the hydrocarbon group containing a fluoro group (—F) as a substituent, so that R １３ At least one of the groups will contain a fluoro group (—F).

[0041] R １３ 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.

[0042] R １３ The fluorocarbon group is a trifluoromethyl group (-CF ３ ), a pentafluoroethyl group (—C ２ F ５ ), n-heptafluoropropyl group (—C ３ F ７ ), a pentafluorophenyl group (—C ６ F ５ ), a trifluoromethoxy group (—OCF ３ ), a pentafluoroethoxy group (—OC ２ F ５ ), n-heptafluoropropoxy group (—OC ３ F ７ ), a pentafluorophenoxy group (—OC ６ F ５ ), a fluoromethyl group (—CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (—CH ２ CF ３ ), p-fluorophenyl group (—C ６ H ４ F), 2-trifluoromethoxyethyl group, etc. １３ 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 ), an isopropyl group (-CH(CH ３ ) ２ ), n-butyl group (—CH ２ CH ２ CH ２CH ３ ), s-butyl group (—CH ２ CH (CH ３ ) ２ ), isobutyl group (—CH ２ CH (CH ３ ) ２ ), t-butyl group (—C(CH ３ ) ３ ), 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 Among these, from the viewpoint of improving the capacity retention rate and the resistance increase rate after charge-discharge cycling, a fluoro group (-F), a trifluoromethyl group (-CF ３ ), methyl group (-CH ３ ), ethyl group (-CH ２ CH ３ ), vinyl group (-CH=CH ２ ), n-propyl group (—CH ２ CH ２ CH ３ ), n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), t-butyl group (—C(CH ３ ) ３ ), 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 ) is particularly preferred.

[0043] Examples of the compound represented by formula (I-3) include compounds represented by the following formula: The non-aqueous electrolyte may contain two or more types of compounds represented by formula (I-3).

[0044]

[0045] The total content of carbonate compounds in the non-aqueous electrolyte is usually 0.1% by mass or more and 20% 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 1.5% by mass or more, and the upper limit being preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, and particularly preferably 8% by mass or less, with respect to the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is 100% by mass). When the total content of these compounds is within the above range, it becomes easier to control the capacity retention rate and resistance increase rate after charge / discharge cycling to good values.

[0046] [Sulfonyl Compound] (Compound represented by formula (II))

[0047]

[0048] R ２１ represents "a group represented by formula (ii-1)," "a group represented by formula (ii-2)," or "a divalent hydrocarbon group having 1 to 6 carbon atoms," but a "divalent hydrocarbon group" means a hydrocarbon group having two bonding positions, and is not limited to an aliphatic hydrocarbon group having a straight-chain structure, but may be a 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), or may be an aromatic hydrocarbon group. In other words, alkylene groups, alkenylene groups, alkynylene groups, arylene groups, etc. are all included in the "divalent hydrocarbon group."

[0049] R ２１ When is a hydrocarbon group, the number of carbon atoms is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

[0050]

[0051] The wavy lines in formula (ii-1) and formula (ii-2) indicate that their ends are bonded to two oxygen atoms (—O—) in formula (II), respectively, to form a cyclic sulfate ester structure.

[0052] R２２ means "oxymethylene group (-OCH ２ -), "oxyethylene group (-OCH ２ CH ２ -), "oxa group (-O-)", or "divalent hydrocarbon group having 1 to 6 carbon atoms", but "divalent hydrocarbon group" is defined as R ２１ In addition, R ２２ is an oxymethylene group (-OCH ２ -), oxyethylene group (-OCH ２ CH ２ The term "an oxa group (-O-)" means that the oxa group is a sulfur atom (-S(=O) ２ O—) to form a cyclic sulfate structure.

[0053] R ２２ Examples of the oxymethylene group include ２ -), oxyethylene group (-OCH ２ CH ２ -) is particularly preferred.

[0054] R ２３ represents a "hydrocarbon group having 1 to 8 carbon atoms" or a "hydrogen atom (-H)", but 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 ), an isopropyl 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 ) ３ ), hexyl group (-CH ２ CH ２ CH ２ CH ２ CH ２ CH３ ), a cyclohexyl group (-C ６ H １１ ), a phenyl group (-C ６ H ５ ) is preferred, and from the viewpoint of improving the capacity retention rate and the resistance increase rate after charge-discharge cycling, an n-butyl group (—CH ２ CH ２ CH ２ CH ３ ), and a hydrogen atom (—H) are particularly preferred.

[0055] Examples of the compound represented by formula (II) include a cyclic sulfate ester compound represented by the following formula (II-1), and compounds represented by the following formulas (II-2) and (II-3). The nonaqueous electrolyte may contain two or more types of compounds represented by formula (II).

[0056]

[0057] (Compound represented by formula (III))

[0058]

[0059] R ３ 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 contains a fluoro group (-F) as a substituent and may also contain an oxa group (-O-) as a substituent", but the terms "fluorocarbon group" and "hydrocarbon group" are used interchangeably with R １１ The phrase "containing a fluoro group (-F) as a substituent and optionally containing an oxa group (-O-) as a substituent" means that at least one hydrogen atom of the hydrocarbon group is substituted with a fluoro group (-F), and a carbon atom of the hydrocarbon group may be substituted with an oxa group (-O-).

[0060] R ３ 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. ３When 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.

[0061] R ３ Examples of the fluoro group include a fluoro group (-F), a trifluoromethyl group (-CF ３ ), a pentafluoroethyl group (—C ２ F ５ ), n-heptafluoropropyl group (—C ３ F ７ ), a pentafluorophenyl group (—C ６ F ５ ), a trifluoromethoxy group (—OCF ３ ), a pentafluoroethoxy group (—OC ２ F ５ ), n-heptafluoropropoxy group (—OC ３ F ７ ), a pentafluorophenoxy group (—OC ６ F ５ ), a fluoromethyl group (—CH ２ F), difluoromethyl group (-CHF ２ ), 2,2,2-trifluoroethyl group (—CH ２ CF ３ ), p-fluorophenyl group (—C ６ H ４ F), 2-trifluoromethoxyethyl group, and the like.

[0062] (M ３ ) ＋ represents an "alkali metal ion," an "alkaline earth metal ion," an "ammonium ion," an "imidazolium ion," a "pyridinium ion," a "pyrrolidinium ion," a "piperidinium ion," or a "phosphonium ion," but is particularly preferably a lithium ion.

[0063] The compound represented by formula (III) includes lithium fluorosulfonate (LiSO) represented by the following formula (III-1): ３ F), lithium trifluoromethanesulfonate (CF) represented by the following formula (III-2): ３ SO ３F) The non-aqueous electrolyte may contain two or more types of compounds represented by formula (III).

[0064]

[0065] The total content of sulfonyl compounds in the non-aqueous electrolyte is usually 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, even more preferably 0.3% by mass or more, and particularly preferably 0.5% 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, with respect 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 total content of these compounds is within the above range, it becomes easier to control the capacity retention rate and resistance increase rate after charge / discharge cycling to good values.

[0066] (Non-aqueous solvent) A non-aqueous electrolyte generally contains a non-aqueous solvent (excluding the compounds represented by formula (I-1), formula (I-2), and formula (I-3). Hereinafter, this may also be simply referred to as a "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.

[0067] Examples of non-aqueous solvents include cyclic carbonates having no fluoro group (-F), fluorocarbon group, or hydrocarbon group, chain carbonates having no fluorocarbon group or hydrocarbon group, 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 having no fluoro group (-F), fluorocarbon group, or hydrocarbon group include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of chain carbonates not having a fluorocarbon group or a hydrocarbon group 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, 1,2-dibutoxyethane, etc. 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, and N,N'-dimethylimidazolidinone.

[0068] The nonaqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates having no fluoro group (-F), fluorocarbon group, or hydrocarbon group, and chain carbonates having no fluorocarbon group or hydrocarbon group. 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 nonaqueous solvent.

[0069] 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.

[0070] 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. The lower limit of the content of the nonaqueous solvent is preferably 60 mass % or more, more preferably 70 mass % or more, and even more preferably 80 mass %, relative to the total amount of the nonaqueous electrolyte.

[0071] 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.

[0072] (Electrolyte) The non-aqueous electrolyte generally contains an electrolyte.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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 (LiPF６ 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.

[0077] 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 3.0 mol / L or less, and more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0078] The non-aqueous electrolyte is lithium hexafluorophosphate (LiPF ６ ), the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF ６ The concentration of the HCl HCl salt 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.

[0079] <Non-aqueous electrolyte secondary battery> A non-aqueous electrolyte secondary battery according to another embodiment of the present invention is a non-aqueous 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.

[0080] (Positive Electrode) A positive electrode can usually be produced 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.

[0081] The positive electrode active material is MoS ２ , TiS ２ , MnO ２ , V ２ O ５ transition metal oxides or transition metal sulfides such as LiCoO ２ , LiMnO ２ , LiMn ２ O ４ , LiNiO ２ , LiNi Ｘ Co （１－Ｘ） O ２ (0<X<1), LiNi ｘ Co ｙ Mnｚ O ２ (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"; e.g., LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ , LiNi ０．５ Co ０．３ Mn ０．２ O 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 Lithium and transition metal composite oxides such as Li ｔ Ni １－ｘ－ｙ Co ｘ Al ｙ O ２ (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 O ２ composite oxides comprising lithium, a transition metal, and a typical metal, such as lithium phosphate (LiFePO); conductive polymer materials, such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, and polyaniline composites; lithium iron phosphate (LiFePO ４ ), lithium manganese phosphate (LiMnPO ４ ), lithium manganese iron phosphate (LiMn ｘ Fe １－ｘ P.O. ４ ; 0<x<1), lithium cobalt phosphate (LiCoPO ４ ), lithium nickel phosphate (LiNiPO ４ lithium metal phosphates such as ammonium phosphate;

[0082] Examples of binders for the positive electrode include polyvinylidene fluoride, examples of conductive additives for the positive electrode include carbon black (e.g., acetylene black), amorphous whiskers, graphite, etc., and examples of thickeners for the positive electrode include carboxymethyl cellulose, etc. Examples of solvents for the slurry used to form the positive electrode include organic solvents such as N-methylpyrrolidone.

[0083] The total content of the positive electrode active material in the positive electrode mixture layer is usually 70% by mass to 97% by mass, and preferably 75% by mass or more and preferably 95% by mass or less, when the total content of the positive electrode mixture layer is 100% by mass.

[0084] 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.

[0085] (Negative Electrode) A negative electrode can usually 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 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 current collector.

[0086] 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, carbides, etc. that can be doped / dedoped with lithium ions. When the negative electrode active material is silicon, etc., a particulate (powder) type of silicon or compound is usually used. The negative electrode active material used is not limited to one type, and two or more types may be mixed and used.

[0087] The negative electrode active material preferably contains at least one selected from the group consisting of carbon particles and silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing silicon and carbon components. 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) calcined at 1500°C or less, and mesophase pitch carbon fiber (MCF).

[0088] 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.

[0089] 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, with the lower limit being preferably 10 μm or more, more preferably 15 μm or more, and the upper limit being preferably 25 μm or less, more preferably 20 μm or less.

[0090] 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 ２ / g, and the lower limit is preferably 2.0 m ２ / g or more, more preferably 3.0m ２ / g or more, and the upper limit is preferably 4.5m ２ / g or less, more preferably 4.0m ２ / g or less.

[0091] 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, and the upper limit is preferably 1.8 or less, more preferably 1.6 or less, and even more preferably 1.4 or less.

[0092] The median diameter D50 of the silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component is usually 0.5 μm to 20 μm, with the lower limit being preferably 1.0 μm or more, more preferably 3.0 μm or more, and the upper limit being preferably 15 μm or less, more preferably 10 μm or less.

[0093] The BET specific surface area of ​​silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing silicon and carbon components is usually 1.0 m ２ / g to 5.0m ２ / g, and the lower limit is preferably 1.5 m ２ / g or more, more preferably 2.0m ２ / g or more, and the upper limit is preferably 4.5m ２ / g or less, more preferably 4.0m ２ / g or less.

[0094] When the negative electrode active material contains carbon particles and at least one selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component, the total mass of the silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component in the negative electrode active material is usually 1% by mass to 20% by mass, when the total mass of the entire negative electrode active material is taken as 100% by mass, but the lower limit is preferably 3% by mass or more, more preferably 5% by mass or more, and the upper limit is preferably 18% by mass or less, more preferably 15% by mass or less.

[0095] When the negative electrode active material contains carbon particles and at least one selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component, the total mass of the carbon particles in the negative electrode active material is typically 70% to 99% by mass, with the total mass of the entire negative electrode active material being 100% by mass, but the lower limit is preferably 80% by mass or more, more preferably 85% by mass or more, and the upper limit is preferably 95% by mass or less, more preferably 90% by mass or less. 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.

[0096] 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 when the entire negative electrode mixture layer is taken as 100% by mass, but the lower limit is preferably 75% by mass or more and the upper limit is preferably 99% by mass or less.

[0097] Examples of binders for the negative electrode include styrene-butadiene rubber (SBR), etc. The total content of the binder copolymer in the negative electrode mixture layer is usually 0.1% by mass to 5% by mass when the entire negative electrode mixture layer is taken as 100% by mass, but the lower limit is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and the upper limit is preferably 3% by mass or less, more preferably 2% by mass or less.

[0098] 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.

[0099] The total content of the conductive additive in the negative electrode mixture layer is usually 0.01% by mass to 3% by mass when 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, and the upper limit is preferably 2% by mass or less, more preferably 1% by mass or less.

[0100] 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.

[0101] The total content of the thickener in the negative electrode mixture layer is usually 0.1% by mass to 5% by mass, when the entire negative electrode mixture layer is taken as 100% by mass. The lower limit is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more, and the upper limit is preferably 3% by mass or less, and more preferably 2% by mass or less.

[0102] 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.

[0103] Examples of materials for the current collector of the negative electrode include copper, nickel, stainless steel, and nickel-plated steel.

[0104] <Separator> The nonaqueous electrolyte secondary battery according to one 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 separator may be 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, and polyamide. Among these, the separator is preferably a porous resin sheet having a single-layer or multilayer structure. The porous resin sheet is primarily 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.

[0105] <Case> The shape of the case is not particularly limited and may be appropriately selected depending on the application of the lithium secondary battery precursor of the present disclosure, 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.

[0106] <Specific Example of Lithium Secondary Battery Precursor> 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.

[0107] As shown in Fig. 1, the lithium secondary battery precursor 1 is a laminated battery precursor. Specifically, in the lithium 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.

[0108] As shown in Fig. 1, the battery element 10 is formed by stacking a positive electrode 11, a separator 13, and a negative electrode 12. The positive electrode 11 is formed by forming a positive electrode composite layer 11B on both main surfaces of a positive electrode current collector 11A. The negative electrode 12 is formed by forming a negative electrode composite layer 12B on both main surfaces of a negative electrode current collector 12A. The positive electrode composite layer 11B formed on one main surface of the positive electrode current collector 11A of the positive electrode 11 and the negative electrode composite layer 12B formed on one main surface of the negative electrode current collector 12A of the negative electrode 12 adjacent to the positive electrode 11 face each other with the separator 13 interposed therebetween.

[0109] 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. The positive electrode and the negative electrode may each have an active material layer formed on one side of the respective current collectors.

[0110] The lithium secondary battery precursor 1 is a stacked-type lithium secondary battery precursor, but the lithium secondary battery precursor of the present disclosure is not limited thereto and may be, for example, a wound-type lithium secondary battery precursor. A wound-type 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-type lithium secondary battery precursors include cylindrical lithium secondary battery precursors and prismatic lithium secondary battery precursors.

[0111] 1 , in the lithium secondary battery precursor 1, the directions in which the positive electrode lead and the negative electrode lead 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 thereto. For example, the directions in which the positive electrode lead and the negative electrode lead protrude from the inside to the outside of the exterior body 30 may be the same direction relative to the exterior body 30.

[0112] 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.

[0113] 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.

[0114] 2 , a disc-shaped negative electrode 42, a separator 45 filled with a nonaqueous electrolyte solution, a disc-shaped positive electrode 41, and, as needed, spacer plates 47, 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 via a gasket 46. In this example, the nonaqueous electrolyte solution of the present disclosure is used as the nonaqueous electrolyte solution filled in the separator 45.

[0115] 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. 2 .

[0116] [Lithium secondary battery and manufacturing method thereof] A manufacturing method of a lithium secondary battery according to the present disclosure includes the steps of: preparing the lithium secondary battery precursor according to the present disclosure described above (hereinafter also referred to as the "preparation step"); and charging and discharging the lithium secondary battery precursor. The lithium secondary battery according to the present disclosure is a lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor according to the present disclosure described above.

[0117] 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.

[0118] The preparation step may be a step of simply preparing a previously manufactured lithium secondary battery precursor of the present disclosure for the step of charging and discharging, or may be a step of manufacturing the lithium secondary battery precursor of the present disclosure. The lithium secondary battery precursor is as described above.

[0119] In the step of charging and discharging, the charging and discharging of the lithium 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 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 secondary battery precursor.

[0120] 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.

[0121] 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.

[0122] Example 1 Preparation of Non-Aqueous Electrolyte Solution Ethylene carbonate (hereinafter referred to as "EC"), dimethyl carbonate (hereinafter referred to as "DMC"), and ethyl methyl carbonate (hereinafter referred to 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. ６The above was dissolved so that the concentration in the finally obtained non-aqueous electrolyte solution was 1.0 mol / L to obtain an electrolyte solution (hereinafter also referred to as "basic electrolyte solution"). A compound represented by the following formula (I-2-1) was blended into the obtained basic electrolyte solution so that the content relative to the total amount of the finally obtained non-aqueous electrolyte solution was 2.0 mass%, and further a compound represented by the following formula (II-1) was blended so that the content relative to the total amount of the non-aqueous electrolyte solution was 2.0 mass%, to obtain a non-aqueous electrolyte solution.

[0123]

[0124] <Preparation of Positive Electrode> LiNi as Positive Electrode Active Material ０．８ Co ０．１ Mn ０．１ O ２ A mixture was obtained by mixing 94% by mass of cellulose acetate, 3% by mass of carbon black as a conductive additive, and 3% by mass of polyvinylidene fluoride (PVdF) as a binder. The resulting 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 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 active material layer.

[0125] <Preparation of Negative Electrode> As the negative electrode active material, 92.15 mass % of graphite and silicon oxide (SiO ｘ A negative electrode composite slurry was obtained by mixing 4.85 mass% silicon monoxide (x=1), 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. A 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.

[0126] <Preparation of Separator> A porous polyethylene film was prepared as a separator.

[0127] <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. 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, immersing the separator, positive electrode, and negative electrode 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.

[0128] <Fabrication of Lithium Ion Secondary Battery> 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.

[0129] <Measurement of Initial Discharge Capacity> The lithium ion secondary battery was charged to 4.2 V in a thermostatic chamber 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.

[0130] <Measurement of Initial Resistance Value> After measuring the initial discharge capacity, the lithium ion secondary battery was charged to 3.7 V, and then 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 1.0 C was measured in a thermostatic chamber at -20°C. CC10s discharge refers to discharge performed at a constant current for 10 seconds. Based on the obtained amount of voltage drop and each current value (i.e., each current value corresponding to a discharge rate of 0.1 C to 1.0 C), the DC resistance [Ω] was measured as the initial resistance value.

[0131] <Charge-Discharge Cycle Test> Next, the lithium ion secondary battery after the initial resistance measurement 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.

[0132] <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 for the initial discharge capacity. For Comparative Example 1 described below, the discharge capacity of the lithium ion secondary battery after the charge / discharge cycle test was also measured in the same manner. The discharge capacity retention rate after charge / discharge cycles of Example 1 was calculated as a relative value when the discharge capacity retention rate after charge / discharge cycles of Comparative Example 1 was set to 100 (see the following formula). Discharge capacity retention rate after charge / discharge cycles of Example 1 (relative value) = (discharge capacity retention rate after charge / discharge cycles of Example 1) / (discharge capacity retention rate after charge / discharge cycles of Comparative Example 1) × 100

[0133] <Measurement of Resistance Increase Rate After Charge / Discharge Cycles 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. For Comparative Example 1 described below, the resistance value (DCIR: Direct Current Internal Resistance) of the lithium ion secondary battery after the charge / discharge cycle test was also measured in the same manner. The resistance increase rate after the charge / discharge cycles of each Example was calculated as a relative value when the resistance increase rate after the charge / discharge cycles of Comparative Example 1 was set to 100 (see the following formula). Resistance increase rate after the charge / discharge cycles of each Example (relative value) = (resistance increase rate after the charge / discharge cycles of each Example) / (resistance increase rate after the charge / discharge cycles of Comparative Example 1) × 100

[0134] Examples 2 to 12, Comparative Examples 1 to 4 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 solutions were changed as shown in Table 1. The results are shown in Table 1. The additives added to the non-aqueous electrolyte solutions of Examples 2 to 12 and Comparative Examples 1 to 4 are as shown below. In Table 1, "-" indicates that no additive was added.

[0135]

[0136]

[0137] As is clear from Table 1, the lithium ion secondary batteries using the nonaqueous electrolytes of Examples 1 to 12 containing a carbonate compound and a sulfonyl compound have improved capacity retention and resistance increase rates after charge-discharge cycling compared to the lithium ion secondary batteries using the nonaqueous electrolytes of Comparative Examples that do not contain these additive combinations. Specifically, it can be seen that Examples 1 to 4 maintain the capacity retention rate and are superior in resistance increase rate after charge-discharge cycling compared to Comparative Example 2. It can also be seen that Examples 5 to 8 maintain the capacity retention rate and are superior in resistance increase rate after charge-discharge cycling compared to Comparative Example 3, and Examples 9 to 12 maintain the capacity retention rate and are superior in resistance increase rate after charge-discharge cycling compared to Comparative Example 4.

[0138] The disclosure of Japanese Patent Application No. 2024-54730, filed on March 28, 2024, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0139] REFERENCE SIGNS LIST 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 Single cell layer 21 Positive electrode lead 22 Negative electrode lead 30 Exterior body 41 Positive electrode 42 Negative electrode 43 Positive electrode can 44 Sealing plate 45 Separator 46 Gasket 47, 48 Spacer plate

Claims

1. A non-aqueous electrolyte solution containing at least one carbonate compound selected from the group consisting of compounds represented by the following formula (I-1), compounds represented by the following formula (I-2), and compounds represented by the following formula (I-3), and at least one sulfonyl compound selected from the group consisting of compounds represented by the following formula (II) and compounds represented by the following formula (III). (In formula (I-1), R １１ 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, and x represents an integer of 1 to 4. １１ At least one of the groups is the fluorocarbon group or the hydrocarbon group containing a fluoro group (—F) as a substituent. 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, and y represents an integer of 1 to 3. In formula (I-3), R １３ 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. １３ At least one of the groups is the fluorocarbon group or the hydrocarbon group containing a fluoro group (—F) as a substituent. (In formula (II), R ２１ represents a group represented by formula (ii-1), a group represented by formula (ii-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms. ２２ is an oxymethylene group (-OCH ２ -), oxyethylene group (-OCH ２ CH ２ In formula (ii-2), R represents an oxa group (—O—), or a divalent hydrocarbon group having 1 to 6 carbon atoms. ２３ represents a hydrocarbon group having 1 to 8 carbon atoms or a hydrogen atom (—H). ３ 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 contains a fluoro group (-F) as a substituent and may also contain an oxa group (-O-) as a substituent, and (M ３ ) ＋ represents an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, or a phosphonium ion.

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

3. The non-aqueous electrolyte according to claim 1, wherein the total content of the carbonate compound is 0.1% by mass to 20.0% by mass based on the total amount of the non-aqueous electrolyte.

4. The non-aqueous electrolyte according to claim 1, wherein the total content of the sulfonyl compounds is 0.01% by mass to 5.0% by mass based on the total amount of the non-aqueous electrolyte.

5. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, wherein the negative electrode comprises a current collector and a negative electrode composite layer formed on the current collector and containing a negative electrode active material, the negative electrode active material comprises at least one selected from the group consisting of simple silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component, and the non-aqueous electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 4.

6. The nonaqueous electrolyte secondary battery according to claim 5, wherein the negative electrode active material comprises carbon particles and at least one selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing a silicon component and a carbon component.

7. The nonaqueous electrolyte secondary battery according to claim 5, wherein the total mass of at least one selected from the group consisting of the silicon particles, the silicon oxide particles, the silicon carbide particles, and the composite particles is 30 mass% or less when the total mass of the entire negative electrode active material is 100 mass%.

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