Nonaqueous electrolyte for batteries, lithium secondary battery precursor, method for manufacturing lithium secondary battery, and lithium secondary battery

Abstract

The present invention is a non-aqueous electrolyte for a battery that includes a compound represented by the formula (P) and a sulfate ester compound. In the formula (P): each of R1–R4 independently represents an alkyl group with a carbon number of 1–6 or an aryl group with a carbon number of 6–12; L1 represents an alkylene group with a carbon number of 1–6 or an arylene group with a carbon number of 6–12; and n represents an integer in the range 0–2. If n is 2, the two R4 moieties can be identical or different and the two L1 moieties can be identical or different.

Description

[Technical field]

[0001] The present disclosure relates to a nonaqueous electrolyte for a battery, a lithium secondary battery precursor, a method for producing a lithium secondary battery, and a lithium secondary battery. [Background technology]

[0002] Various studies have been conducted on non-aqueous electrolyte solutions for batteries and batteries (such as lithium secondary batteries) using the same. For example, Patent Document 1 discloses a nonaqueous electrolyte secondary battery that has sufficient flame retardant effect and excellent high-temperature charge / discharge cycle characteristics, the nonaqueous electrolyte secondary battery including a positive electrode containing a lithium transition metal composite oxide, a negative electrode capable of inserting and extracting lithium ions, and a nonaqueous electrolyte, in which 20 to 40 volume % of the solvent in the nonaqueous electrolyte is tributyl phosphate (TBP) or triphenyl phosphate (TPP). Patent Document 2 discloses a nonaqueous electrolyte solution for a nonaqueous electrolyte battery having a positive electrode and a negative electrode capable of absorbing and releasing metal ions, which generates little gas during high-temperature storage, and which contains, together with an electrolyte and a nonaqueous solvent, a specific phosphate ester compound in an amount of 0.001% by mass or more and 4.5% by mass or less relative to the total amount of the nonaqueous electrolyte solution. Furthermore, Patent Document 3 discloses a non-aqueous electrolyte for batteries that contains phosphoric acid as a non-aqueous electrolyte for batteries that can suppress an increase in battery resistance after high-temperature storage.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-307768 Patent Document 2: JP 2009-3799 A Patent Document 3: JP 2018-156761 A Summary of the Invention [Problem to be solved by the invention]

[0004] 2. Description of the Related Art There are cases where it is required to reduce the rate at which batteries such as lithium secondary batteries generate heat when short-circuited while suppressing deterioration in battery performance. An object of one embodiment of the present disclosure is to provide a nonaqueous electrolyte solution for a battery, a lithium secondary battery precursor, and a method for producing a lithium secondary battery, which are capable of reducing the heat generation rate upon short circuit while suppressing deterioration in battery performance, and a lithium secondary battery in which deterioration in battery performance is suppressed and the heat generation rate upon short circuit is reduced. [Means for solving the problem]

[0005] Means for solving the above problems include the following aspects. <1> A non-aqueous electrolyte for a battery, comprising a compound represented by the following formula (P) and a sulfate ester compound:

[0006] [ka]

[0007] In formula (P), R 1 ~R 4 each independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms; L 1 represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 12 carbon atoms, and n represents an integer of 0 to 2. When n is 2, two R 4 may be the same or different, and the two L 1 may be the same or different.

[0008] <2> The compound represented by formula (P) includes at least one selected from the group consisting of the following compound (P-1), the following compound (P-2), the following compound (P-3), and the following compound (P-4): <1> The non-aqueous electrolyte for a battery according to claim 1.

[0009] [ka]

[0010] In compound (P-3), m represents an integer of 1 or 2; in compound (P-4), x represents an integer of 1 or 2.

[0011] <3> The sulfate ester compound includes a cyclic sulfate ester compound. <1> or <2> The non-aqueous electrolyte for a battery according to claim 1. <4> The sulfate ester compound includes a compound represented by the following formula (C): <1> ~ <3> 13. The nonaqueous electrolyte for a battery according to claim 12,

[0012] [ka]

[0013] In formula (C), R c1 ~R c4 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b). In formulas (a) and (b), * represents a bonding position.

[0014] <5> The compound represented by formula (C) includes at least one selected from the group consisting of the following compound (C-1) and the following compound (C-4): <4> The non-aqueous electrolyte for a battery according to claim 1.

[0015] [ka]

[0016] <6> a number ratio [sulfate group / phosphate group], which is a ratio of the number of sulfate groups contained in the total amount of the sulfate ester compound to the number of phosphate groups contained in the total amount of the compound represented by formula (P), is more than 0 and 3.00 or less; <1> ~ <5> 13. The nonaqueous electrolyte for a battery according to claim 12, <7> The content of the compound represented by the formula (P) is 0.1% by mass to 1.0% by mass with respect to the total amount of the nonaqueous electrolyte for a battery. <1> ~ <6> 13. The nonaqueous electrolyte for a battery according to claim 12, <8> Further, the present invention relates to a cyclic carbonate ester compound having a carbon-carbon unsaturated bond. <1> ~ <7> 13. The nonaqueous electrolyte for a battery according to claim 12,

[0017] <9> A positive electrode and A negative electrode; <1> ~ <8> and a non-aqueous electrolyte for a battery according to any one of the above items. A lithium secondary battery precursor comprising: <10> <9> preparing a lithium secondary battery precursor according to the present invention; obtaining a lithium secondary battery by charging and discharging the lithium secondary battery precursor; A method for producing a lithium secondary battery, comprising: <11> <9> A lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor described in claim 1. Effect of the Invention

[0018] According to one aspect of the present disclosure, there are provided a nonaqueous electrolyte for a battery, a lithium secondary battery precursor, and a method for producing a lithium secondary battery, which are capable of reducing the heat generation rate upon short circuit while suppressing deterioration in battery performance, and a lithium secondary battery in which deterioration in battery performance is suppressed and the heat generation rate upon short circuit is reduced. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic perspective view showing an example of a laminated battery, which is an example of a lithium secondary battery precursor of the present disclosure or a lithium secondary battery of the present disclosure. [Diagram 2] 2 is a schematic cross-sectional view in the thickness direction of a laminated electrode body housed in the laminated battery shown in FIG. 1. [Diagram 3] 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 precursor of the present disclosure or the lithium secondary battery of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] In this specification, 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 this specification, the amount of each component in a composition means, when a plurality of substances corresponding to each component are present in the composition, the total amount of the plurality of substances present in the composition, unless otherwise specified. In this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0021] [Nonaqueous electrolyte for batteries] The nonaqueous electrolyte for a battery according to the present disclosure (hereinafter also simply referred to as "nonaqueous electrolyte") contains a compound represented by the following formula (P) and a sulfate ester compound.

[0022] [ka]

[0023] In formula (P), R 1 ~R 4 each independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms; L 1 represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 12 carbon atoms, and n represents an integer of 0 to 2. When n is 2, two R 4 may be the same or different, and the two L 1 may be the same or different.

[0024] Through the study of the present inventors, (1) The nonaqueous electrolyte solution contains a compound represented by formula (P), thereby reducing the rate at which heat is generated when the battery is short-circuited; (2) When the non-aqueous electrolyte contains the compound represented by formula (P), the battery performance is deteriorated (for example, the battery resistance is increased); and (3) When the non-aqueous electrolyte contains a compound represented by formula (P) and also contains a sulfate ester compound, the rate of heat generation during a short circuit can be reduced while suppressing deterioration in battery performance. It was discovered that... Therefore, the nonaqueous electrolyte of the present disclosure can reduce the rate of heat generation during a short circuit while suppressing deterioration in battery performance. Furthermore, the nonaqueous electrolyte of the present disclosure contains the compound represented by formula (P) and, compared to a case where the electrolyte does not contain a sulfate ester compound, the heat generation rate during a short circuit can be further reduced (for example, see the comparison between Example 1-1 and Comparative Example 1-1 described later). Such an effect is considered to be due to the combination of the compound represented by formula (P) and the sulfate ester compound.

[0025] Hereinafter, each component that may be contained in the nonaqueous electrolyte solution of the present disclosure will be described.

[0026] <Compound represented by formula (P)> The nonaqueous electrolyte solution of the present disclosure contains at least one compound represented by the following formula (P). The compound represented by formula (P) is included in the phosphate ester compounds, as shown in the following structure.

[0027] [ka]

[0028] In formula (P), R 1 ~R 4 each independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms; L 1 represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 12 carbon atoms, and n represents an integer of 0 to 2. When n is 2, two R 4 may be the same or different, and the two L 1 may be the same or different.

[0029] In formula (P), R 1 ~R 4The alkyl group represented by the formula (I) may be a straight-chain alkyl group or a branched alkyl group. R 1 ~R 4 The alkyl group represented by the following formula (1) has 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms, and further preferably 1 carbon atom.

[0030] In formula (P), R 1 ~R 4 The aryl group represented by the following formula (I) has 6 to 12 carbon atoms, preferably 6 to 11 carbon atoms, more preferably 6 to 8 carbon atoms, and further preferably 6 or 7 carbon atoms. R 1 ~R 4 The aryl group represented by the formula (I) is preferably a phenyl group or a phenyl group substituted with at least one alkyl group (preferably a methyl group or an ethyl group, more preferably a methyl group), and more preferably a phenyl group.

[0031] In formula (P), R 1 ~R 4 are preferably each independently an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, even more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

[0032] In formula (P), L 1 The alkylene group represented by the formula (I) may be a linear alkylene group or a branched alkylene group. L 1 The alkylene group represented by the following formula (1) has 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms, and further preferably 1 carbon atom.

[0033] In formula (P), L 1 The arylene group represented by the following formula has 6 to 12 carbon atoms, preferably 6 to 11 carbon atoms, more preferably 6 to 8 carbon atoms, and further preferably 6 or 7 carbon atoms. L 1The arylene group represented by the formula (I) is preferably a phenylene group, a biphenylene group, a phenylene group substituted with at least one alkyl group (preferably a methyl group or an ethyl group, more preferably a methyl group), or a biphenylene group substituted with at least one alkyl group (preferably a methyl group or an ethyl group, more preferably a methyl group).

[0034] In formula (P), L 1 is preferably an alkylene group having 1 to 6 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms, even more preferably a methylene group or ethylene group, and even more preferably a methylene group.

[0035] In formula (P), n represents an integer of 0 to 2. When n is 2, two R 4 may be the same or different, and the two L 1 may be the same or different. n is preferably 0 or 1, and more preferably 0.

[0036] The compound represented by formula (P) preferably includes at least one selected from the group consisting of the following compound (P-1), the following compound (P-2), the following compound (P-3), and the following compound (P-4).

[0037] [ka]

[0038] In the compound (P-3), m represents 1 or 2. The compound (P-3) may be either a compound in which m is 1 or a compound in which m is 2, or it may be both (ie, a mixture). The compound (P-4) may be either a compound where x is 1 or a compound where x is 2, or it may be both (ie, a mixture).

[0039] The content of the compound represented by formula (P) is preferably 0.01 mass % to 10 mass %, more preferably 0.02 mass % to 5.0 mass %, even more preferably 0.05 mass % to 3.0 mass %, even more preferably 0.05 mass % to 2.0 mass %, and still more preferably 0.1 mass % to 1.0 mass %, relative to the total amount of the nonaqueous electrolyte.

[0040] When the compound represented by formula (P) includes at least one selected from the group consisting of compound (P-1), compound (P-2), compound (P-3), and compound (P-4), the total proportion of compound (P-1), compound (P-2), compound (P-3), and compound (P-4) in the entire compound represented by formula (P) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0041] The preferred range of the content of the compound represented by the above-mentioned formula (P) may be interpreted as the preferred range of the content of each of the compounds (P-1), (P-2), (P-3), and (P-4).

[0042] <Sulfate ester compounds> The nonaqueous electrolyte solution of the present disclosure contains at least one sulfate ester compound. The sulfate compound may be a chain sulfate compound or a cyclic sulfate compound. In order to more effectively exert the effects of the nonaqueous electrolyte solution of the present disclosure, the sulfate ester compound is preferably a cyclic sulfate ester compound.

[0043] The sulfate ester compound preferably contains a compound represented by the following formula (C): The compound represented by formula (C) is included in cyclic sulfate compounds, as shown in the following structure.

[0044] [ka]

[0045] In formula (C), R c1 ~R c4 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b). In formulas (a) and (b), * represents a bonding position.

[0046] In formula (C), R c1 ~R c4 The hydrocarbon group having 1 to 6 carbon atoms represented by the following formula is preferably an alkyl group, an alkenyl group, or an alkynyl group, more preferably an alkyl group or an alkenyl group, and particularly preferably an alkyl group. R c1 ~R c4 The hydrocarbon group having 1 to 6 carbon atoms represented by the following formula (I) preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and particularly preferably 1.

[0047] Specific examples of the compound represented by formula (C) are shown below, but compound (C) is not limited to the following specific examples. The sulfate ester compound preferably contains at least one selected from the group consisting of compound (C-1), compound (C-2), compound (C-3), and compound (C-4), more preferably contains at least one selected from the group consisting of compound (C-1), compound (C-2), and compound (C-3), more preferably contains at least one selected from the group consisting of compound (C-1) and compound (C-2), and even more preferably contains compound (C-1). The sulfate ester compound preferably contains at least one selected from the group consisting of the compound (C-1) and the compound (C-4).

[0048] [ka]

[0049] The content of the sulfate ester compound is preferably 0.001% by mass to 10% by mass, more preferably 0.003% by mass to 5.0% by mass, even more preferably 0.003% by mass to 3.0% by mass, even more preferably 0.03% by mass to 3.0% by mass, even more preferably 0.1% by mass to 3.0% by mass, and even more preferably 0.1% by mass to 2.0% by mass, relative to the total amount of the nonaqueous electrolyte.

[0050] When the sulfate ester compound contains a cyclic sulfate ester compound (preferably a compound represented by formula (C)), the proportion of the cyclic sulfate ester compound (preferably a compound represented by formula (C)) in the total sulfate ester compounds is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0051] The preferred range of the content of the sulfate ester compound is as follows: This may be interpreted as a preferred range of the cyclic sulfate ester compound, It may be interpreted as a preferred range of the content of the compound represented by formula (C), It may also be interpreted as a preferred range for the content of each of the compounds (C-1) to (C-4).

[0052] In the nonaqueous electrolyte solution of the present disclosure, the ratio of the number of sulfate groups contained in the total amount of the sulfate ester compounds to the number of phosphate groups contained in the total amount of the compounds represented by formula (P) [sulfate groups / phosphate groups] is preferably greater than 0 and not greater than 3.00. When the ratio of the number of groups [sulfate group / phosphate group] is greater than 0 and equal to or less than 3.00, the effects of the nonaqueous electrolyte solution of the present disclosure described above are more effectively exhibited. The ratio of the numbers of sulfate groups to phosphate groups is preferably 0.10 to 2.50, and more preferably 0.20 to 2.20.

[0053] <Electrolytes> The non-aqueous electrolyte of the present disclosure contains at least one electrolyte, preferably a lithium salt. Examples of lithium salt electrolytes include: Lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorotantalate (LiTaF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium decachlorodecaborate (Li2B 10 Cl 10 ) and other inorganic acid anion salts; Anion salts of organic acids such as lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), lithium bis(fluorosulfonyl)imide (Li(FSO2)2N), and lithium bis(pentafluoroethanesulfonyl)imide (Li(C2F5SO2)2N); etc. As the lithium salt, LiPF6 is particularly preferred.

[0054] The proportion of the lithium salt in the entire electrolyte contained in the nonaqueous electrolyte solution of the present disclosure is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0055] The proportion of LiPF6 in the entire electrolyte contained in the nonaqueous electrolyte of the present disclosure is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0056] The concentration of the electrolyte in the nonaqueous electrolyte solution of the present disclosure is preferably 0.1 mol / L to 3 mol / L, and more preferably 0.5 mol / L to 2 mol / L.

[0057] The concentration of LiPF6 in the nonaqueous electrolyte of the present disclosure is preferably 0.1 mol / L to 3 mol / L, and more preferably 0.5 mol / L to 2 mol / L.

[0058] <Non-aqueous solvent> The nonaqueous electrolyte of the present disclosure contains at least one nonaqueous solvent. Examples of non-aqueous solvents include cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, fluorine-containing chain carbonates, aliphatic carboxylate esters, fluorine-containing aliphatic carboxylate 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.

[0059] Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of fluorine-containing cyclic carbonates include fluoroethylene carbonate (FEC). 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 carboxylate 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. The amides include, for example, N,N-dimethylformamide. Examples of lactams include N-methylpyrrolidinone, N-methyloxazolidinone, and N,N'-dimethylimidazolidinone.

[0060] 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 cyclic carbonates, fluorine-containing cyclic carbonates, chain carbonates, and fluorine-containing chain carbonates in the non-aqueous solvent is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0061] 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 to 100% by mass, more preferably 60% by mass to 100% by mass, and even more preferably 80% by mass to 100% by mass.

[0062] The proportion of the nonaqueous solvent in the nonaqueous electrolyte solution of the present disclosure is preferably 60 mass % or more, and more preferably 70 mass % or more.

[0063] <Cyclic carbonate compounds containing carbon-carbon unsaturated bonds> The nonaqueous electrolyte solution of the present disclosure may contain at least one cyclic carbonate compound containing a carbon-carbon unsaturated bond. When the nonaqueous electrolyte solution of the present disclosure contains a cyclic carbonate compound containing a carbon-carbon unsaturated bond, the chemical stability of the nonaqueous electrolyte solution can be further improved.

[0064] Examples of cyclic carbonate compounds containing a carbon-carbon unsaturated bond include vinylene carbonate compounds, vinyl ethylene carbonate compounds, and methylene ethylene carbonate compounds.

[0065] Examples of vinylene carbonate compounds include vinylene carbonate (also known as 1,3-dioxol-2-one), methyl vinylene carbonate (also known as 4-methyl-1,3-dioxol-2-one), ethyl vinylene carbonate (also known as 4-ethyl-1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1,3-dioxol-2-one, and 4-trifluoromethyl-1,3-dioxol-2-one.

[0066] Examples of vinyl ethylene carbonate compounds include vinyl ethylene carbonate (also known as 4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, 4-ethyl-4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolan-2-one, 4,4-divinyl-1,3-dioxolan-2-one, and 4,5-divinyl-1,3-dioxolan-2-one.

[0067] Examples of the methylene ethylene carbonate-based compounds include 4-methylene-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5-methylene-1,3-dioxolan-2-one.

[0068] As the cyclic carbonate compound containing a carbon-carbon unsaturated bond, vinylene carbonate is particularly preferred.

[0069] When the nonaqueous electrolyte solution of the present disclosure contains a cyclic carbonate ester compound having a carbon-carbon unsaturated bond, the content of the cyclic carbonate ester compound having a carbon-carbon unsaturated bond is preferably 0.1 mass % to 10.0 mass %, more preferably 0.2 mass % to 5.0 mass %, even more preferably 0.2 mass % to 2.0 mass %, and still more preferably 0.2 mass % to 1.0 mass %, relative to the total amount of the nonaqueous electrolyte solution.

[0070] When the nonaqueous electrolyte solution of the present disclosure contains vinylene carbonate, the content of vinylene carbonate is preferably 0.1 mass % to 10.0 mass %, more preferably 0.2 mass % to 5.0 mass %, even more preferably 0.2 mass % to 2.0 mass %, and still more preferably 0.2 mass % to 1.0 mass %, relative to the total amount of the nonaqueous electrolyte solution.

[0071] When the nonaqueous electrolyte solution of the present disclosure contains a cyclic carbonate compound containing a carbon-carbon unsaturated bond, the ratio of the total content of compound (P) and sulfate compound to the mass content of the cyclic carbonate compound (hereinafter also referred to as "mass ratio [(compound (P)+sulfate compound) / cyclic carbonate compound containing a carbon-carbon unsaturated bond]") is preferably 0.3 to 5.0, more preferably 0.5 to 4.0, and even more preferably 0.8 to 3.0. When the content mass ratio [(compound (P)+sulfate ester compound) / cyclic carbonate ester compound having a carbon-carbon unsaturated bond] is 0.3 or more, the effect of the combination of compound (P) and the sulfate ester compound described above is more effectively exerted. When the content mass ratio [(compound (P)+sulfuric acid ester compound) / cyclic carbonate ester compound having a carbon-carbon unsaturated bond] is 5.0 or less, the effect of adding the cyclic carbonate ester compound having a carbon-carbon unsaturated bond is more effectively exerted.

[0072] <Other ingredients> The nonaqueous electrolyte solution of the present disclosure may contain at least one component other than the above-mentioned components.

[0073] [Lithium secondary battery precursor, lithium secondary battery] The lithium secondary battery precursor of the present disclosure includes a positive electrode, a negative electrode, and the nonaqueous electrolyte solution of the present disclosure described above.

[0074] The lithium secondary battery of the present disclosure is a lithium secondary battery obtained by charging and discharging (hereinafter also referred to as "charging and discharging") the lithium secondary battery precursor of the present disclosure.

[0075] In the present disclosure, the lithium secondary battery precursor means a lithium secondary battery after production and before charging and discharging. In other words, in the present disclosure, a lithium secondary battery refers to a battery obtained by charging and discharging a lithium secondary battery precursor.

[0076] The lithium secondary battery precursor of the present disclosure contains the nonaqueous electrolyte solution of the present disclosure described above. Therefore, the lithium secondary battery precursor and the nonaqueous electrolyte solution of the present disclosure provide the same effects as those provided by the nonaqueous electrolyte solution of the present disclosure described above.

[0077] Hereinafter, each of the components that can be included in the lithium secondary battery precursor of the present disclosure will be described. Each component that can be included in the lithium secondary battery of the present disclosure is basically similar to each component that can be included in the lithium secondary battery precursor of the present disclosure. In the lithium secondary battery of the present disclosure, a SEI (Solid Electrolyte Interface) film is preferably formed on the surface of the positive electrode (preferably a positive electrode active material) and / or the negative electrode (preferably a negative electrode active material). The SEI film is a coating that can be formed by charging and discharging a lithium secondary battery precursor. The SEI film contains components in the nonaqueous electrolyte and / or products (e.g., decomposition products) derived from the components.

[0078] <Negative electrode> The negative electrode is capable of absorbing and releasing lithium ions. The negative electrode preferably contains at least one negative electrode active material. The negative electrode active material in the negative electrode preferably contains a carbon material capable of absorbing and releasing lithium ions. When the negative electrode active material contains the carbon material, the stability of the SEI film formed by charging and discharging is further improved. In particular, the carbon material is advantageous in terms of the stability of the SEI film because it undergoes less morphological change during charging and discharging than other negative electrode active materials (e.g., metal Li, metal Si, silicon oxide). The negative electrode active material may contain both the above carbon material and other negative electrode active materials (for example, metallic Li, metallic Si, silicon oxide).

[0079] Examples of carbon materials as negative electrode active materials include hard carbon, soft carbon, MCMB, natural graphite, and artificial graphite. Each of the natural graphite and synthetic graphite may be coated with amorphous carbon. Among these, hard carbon, MCMB, natural graphite coated with amorphous carbon, or artificial graphite coated with amorphous carbon is preferred because the SEI film formed on the negative electrode is highly stable and has a high ability to absorb lithium ions.

[0080] The negative electrode preferably includes a negative electrode current collector. The material of the negative electrode current collector is not particularly limited, and any known material can be used. Specific examples of the negative electrode current collector include metal materials such as copper, nickel, stainless steel, nickel-plated steel, etc. Among these, copper is particularly preferred from the viewpoint of ease of processing.

[0081] The negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on at least a portion of the surface of the negative electrode current collector. The negative electrode active material layer contains at least one negative electrode active material, which contains the above-mentioned carbon material. From the viewpoint of the energy density of the battery, the content of the carbon material in the negative electrode active material layer is preferably 70 mass % or more, more preferably 80 mass % or more, and even more preferably 90 mass % or more, based on the total amount of the negative electrode active material layer.

[0082] The negative electrode active material layer may further contain at least one type of binder. Styrene butadiene is used as a binder. Ngo M (SBR) (e.g., SBR latex), acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose, polyvinyl alcohol, hydroxypropyl cellulose, and diacetyl cellulose. The binder preferably contains SBR latex and carboxymethyl cellulose. The content of the binder in the negative electrode active material layer is preferably 1 mass % to 20 mass %, more preferably 1 mass % to 10 mass %, and even more preferably 1 mass % to 5 mass %, relative to the total amount of the negative electrode active material layer.

[0083] <Positive electrode> The positive electrode preferably contains at least one positive electrode active material. The positive electrode active material is not particularly limited, and any known positive electrode active material can be used. The positive electrode active material is preferably a lithium transition metal oxide or a lithium metal phosphate. Examples of lithium transition metal oxides include: Lithium Cobalt Oxide (LiCoO2) Lithium Manganese Oxide (LiMnO2 or LiMn2O4) Lithium Nickel Oxide (LiNiO2) Lithium Nickel Cobalt Oxide, Lithium Nickel Manganese Cobalt Oxide (hereinafter referred to as "NMC"); Lithium Nickel Cobalt Aluminum Oxide (hereinafter referred to as "NCA"), etc. Examples of lithium metal phosphate include: Lithium iron phosphate (LiFePO4), Lithium manganese phosphate (LiMnPO4), Lithium iron manganese phosphate (LiMn (1-X) Fe X PO4;0 <X<1)、 etc.

[0084] From the viewpoint of more effectively exerting the effects of the nonaqueous electrolyte of the present disclosure, the positive electrode active material is It is preferable that the lithium transition metal oxide is contained, More preferably, it contains NMC, It is more preferable that the composition contains a compound represented by the following formula (X):

[0085] LiNi a Mn b Co c O2… (X) (In formula (X), a, b, and c are each independently greater than 0 and less than 1.00, and the sum of a, b, and c is 0.99 to 1.00.)

[0086] Specific examples of the compound represented by formula (X) include LiNi 0.33 Mn 0.33 Co 0.33 O2, LiNi 0.5 Mn 0.2 Co 0.3 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, etc.

[0087] In formula (X), a is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.50 or more, and still more preferably 0.70 or more. A larger value of a (that is, a higher Ni content) is advantageous in that the battery capacity (energy density) increases.

[0088] In formula (X), a is preferably 0.95 or less, more preferably 0.90 or less. In formula (X), b is preferably 0.05 or more, and more preferably 0.10 or more. In formula (X), b is preferably 0.90 or less, more preferably 0.50 or less, and even more preferably 0.40 or less. In formula (X), c is preferably 0.05 or more, and more preferably 0.10 or more. In formula (X), c is preferably 0.90 or less, more preferably 0.50 or less, and even more preferably 0.40 or less.

[0089] The positive electrode may contain at least one conductive assistant. The conductive assistant may be a carbon material such as carbon black, amorphous whiskers, or graphite.

[0090] The positive electrode preferably includes a positive electrode current collector. There is no particular limitation on the material of the positive electrode current collector, and any known material can be used. Specific examples of the positive electrode current collector include metal materials such as aluminum, stainless steel, nickel, titanium, and tantalum; carbon materials such as carbon cloth and carbon paper; and the like. Among these, aluminum is preferred from the viewpoint of the balance between high electrical conductivity and cost. Here, "aluminum" refers to pure aluminum or an aluminum alloy.

[0091] The positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on at least a portion of the surface of the positive electrode current collector. The positive electrode active material layer contains at least one positive electrode active material. Preferred positive electrode active materials are as described above. From the viewpoint of the energy density of the battery, the content of the positive electrode active material in the positive electrode active material layer is preferably 70 mass % or more, and more preferably 80 mass % or more, based on the total amount of the positive electrode active material layer. The positive electrode active material layer may further contain at least one of the above-mentioned conductive assistants. The positive electrode active material layer may further contain at least one type of binder. Examples of the binder include polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluororesin, and rubber particles. Examples of the fluororesin include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer. Examples of the rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles. Among these, fluororesin is preferred from the viewpoint of improving the oxidation resistance of the positive electrode active material layer. The content of the binder in the positive electrode active material layer is preferably 1 mass % to 20 mass %, and more preferably 1 mass % to 10 mass %, relative to the total amount of the positive electrode active material layer.

[0092] <separator> The lithium secondary battery precursor of the present disclosure preferably includes a separator between the negative electrode and the positive electrode. The separator is a membrane that electrically insulates the positive electrode from the negative electrode and is permeable to lithium ions, and examples of the separator include a porous membrane and a polymer electrolyte. As the porous membrane, a microporous polymer film is preferably used, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like. In particular, porous polyolefin is preferred, specifically, a porous polyethylene film, a porous polypropylene film, or a multi-layer film of a porous polyethylene film and a porous polypropylene film can be exemplified. The porous polyolefin film may be coated with another resin having excellent thermal stability. Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, and a polymer swollen with an electrolytic solution. The nonaqueous electrolyte solution of the present disclosure may be used for the purpose of swelling a polymer to obtain a polymer electrolyte.

[0093] <Construction of lithium secondary battery precursor> The lithium secondary battery precursor of the present disclosure can have various known shapes, and can be formed into any shape such as a cylinder, a coin, a square, a laminate, a film, etc. However, the basic structure of the lithium secondary battery precursor is the same regardless of the shape, and the design can be modified according to the purpose. For the basic structure of the lithium secondary battery of the present disclosure, the basic structure of the lithium secondary battery precursor of the present disclosure can be referred to.

[0094] An example of the lithium secondary battery precursor of the present disclosure or the lithium secondary battery of the present disclosure is a laminate type battery. FIG. 1 is a schematic perspective view showing an example of a laminated battery, which is an example of a lithium secondary battery precursor or a lithium secondary battery of the present disclosure, and FIG. 2 is a schematic cross-sectional view in the thickness direction of a stacked electrode body accommodated in the laminated battery shown in FIG. The laminated battery shown in Fig. 1 contains a nonaqueous electrolyte (not shown in Fig. 1) and a laminated electrode body (not shown in Fig. 1) and includes a laminated exterior body 1 whose periphery is sealed to seal the inside. As the laminated exterior body 1, for example, an aluminum laminated exterior body is used. 2, the laminated electrode body housed in the laminate exterior body 1 includes a laminate in which positive electrode plates 5 and negative electrode plates 6 are alternately stacked with separators 7 interposed therebetween, and a separator 8 surrounding the periphery of the laminate. The positive electrode plates 5, negative electrode plates 6, separators 7, and separator 8 are impregnated with the nonaqueous electrolyte solution of the present disclosure. Here, the separator 8 surrounding the periphery of the laminate may be omitted. Each of the multiple positive electrode plates 5 in the laminated electrode body is electrically connected to a positive electrode terminal 2 via a positive electrode tab (not shown), and a part of this positive electrode terminal 2 protrudes outward from the peripheral edge of the laminated exterior body 1 (FIG. 1). The portion of the peripheral edge of the laminated exterior body 1 from which the positive electrode terminal 2 protrudes is sealed with an insulating seal 4. Similarly, each of the multiple negative electrode plates 6 in the laminated electrode body is electrically connected to a negative electrode terminal 3 via a negative electrode tab (not shown), and a portion of this negative electrode terminal 3 protrudes outward from the peripheral edge of the laminated exterior body 1 (FIG. 1). The portion of the peripheral edge of the laminated exterior body 1 from which the negative electrode terminal 3 protrudes is sealed with an insulating seal 4. In the laminated battery according to the above example, the number of positive electrode plates 5 is five and the number of negative electrode plates 6 is six, and the positive electrode plates 5 and the negative electrode plates 6 are laminated with separators 7 interposed therebetween in an arrangement in which the outermost layers on both sides are negative electrode plates 6. However, it goes without saying that the number and arrangement of positive and negative electrode plates in the laminated battery are not limited to this example, and various modifications may be made.

[0095] Another example of the lithium secondary battery precursor or the lithium secondary battery of the present disclosure includes a coin-type battery. FIG. 3 is a schematic perspective view showing an example of a coin-type battery, which is another example of the lithium secondary battery precursor of the present disclosure or the lithium secondary battery of the present disclosure. 3, a disk-shaped negative electrode 12, a separator 15 filled with a non-aqueous electrolyte, a disk-shaped positive electrode 11, and, if necessary, spacer plates 17, 18 made of stainless steel, aluminum, or the like are stacked in this order and housed between a positive electrode can 13 (hereinafter also referred to as a "battery can") and a sealing plate 14 (hereinafter also referred to as a "battery can lid"). The positive electrode can 13 and the sealing plate 14 are crimped and sealed with a gasket 16 interposed therebetween. In this example, the nonaqueous electrolyte of the present disclosure is used as the nonaqueous electrolyte injected into separator 15 .

[0096] The applications of the lithium secondary battery precursor or the lithium secondary battery of the present disclosure are not particularly limited, and the battery can be widely used in both small portable devices and large devices. Applications of the lithium secondary battery precursor of the present disclosure or the lithium secondary battery of the present disclosure include, for example, notebook computers, mobile computers, mobile phones, headphone stereos, video movie cameras, liquid crystal televisions, handy cleaners, electronic organizers, calculators, radios, backup power sources, power storage sources (for example, power sources for storing power at night, power sources for storing surplus power generated by solar power, etc.), motors, automobiles, electric automobiles, hybrid automobiles, motorcycles, electric motorcycles, bicycles, electric bicycles, lighting equipment, game consoles, watches, power tools, cameras, etc.

[0097] [Method for manufacturing lithium secondary battery] 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 described above (hereinafter also referred to as a "preparation step"); charging and discharging the lithium secondary battery precursor; Includes.

[0098] 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.

[0099] 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, by this charging and discharging, an SEI film is preferably formed 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. EXAMPLES

[0100] Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples. In the following examples, the "amount added" refers to the content in the finally obtained non-aqueous electrolyte solution (that is, the amount relative to the total amount of the finally obtained non-aqueous electrolyte solution). "wt%" means mass%. "%" means "mass %" unless otherwise specified.

[0101] Example 1-1 <Preparation of non-aqueous electrolyte> Ethylene carbonate (hereinafter, EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:EMC=30:70 to obtain a mixed solvent as a non-aqueous solvent. For the above mixed solvent, LiPF6 as an electrolyte is dissolved so that the concentration in the finally obtained non-aqueous electrolyte is 1 mol / L (hereinafter, also referred to as "1M"). Vinylene carbonate (VC) was dissolved as an additive in such a way that its content in the final non-aqueous electrolyte was 0.5% by mass. The compound (P-1) as an additive was dissolved in the non-aqueous electrolyte solution to give a content of 0.5% by mass. The compound (C-1) as an additive was dissolved in the non-aqueous electrolyte solution to give a content of 0.05% by mass. A non-aqueous electrolyte was obtained.

[0102] Here, compound (P-1) is a specific example of a compound represented by formula (P) (hereinafter also referred to as "compound (P)"), compound (C-1) is a specific example of a compound represented by formula (C) (hereinafter also referred to as "compound (C)"), and VC is a specific example of a cyclic carbonate compound containing a carbon-carbon unsaturated bond.

[0103] <Fabrication of lithium secondary batteries (stacked type batteries)> As the lithium secondary battery, a stacked battery for evaluating the heat generation rate was fabricated. Details are given below.

[0104] (Preparation of positive electrode) -Slurry preparation- A 5 L Planetary Disperser was used to prepare the slurry. NMC532 (i.e., LiNi 0.5 Mn 0.3 Co 0.2 920 g of O2), 20 g of Super-P (conductive carbon manufactured by TIMCAL) as a conductive additive, and 20 g of KS-6 (flake graphite manufactured by TIMREX) as a conductive additive were mixed for 10 minutes, and then 100 g of N-methylpyrrolidone (NMP) was added thereto and mixed for an additional 20 minutes. Next, 150g of 8%-PVDF solution (Kureha PVDFW#7200 dissolved in NMP) was added and kneaded for 30 minutes, and then 150g of the above 8%-PVDF solution was added and kneaded for 30 minutes. Then, 200g of the above 8%-PVDF solution was added and kneaded for 30 minutes. Next, 80g of NMP was added and kneaded for 30 minutes. Then, 27g of NMP was added to adjust the viscosity, and mixed for 30 minutes, and vacuum degassing was performed for 30 minutes. As a result, a positive electrode mixture slurry with a solid content of 60% was obtained.

[0105] - Coating and drying - A die coater was used for applying the slurry. The coating mass after drying is 19.0mg / cm 2 The positive electrode mixture slurry was applied to a portion of one side of an aluminum foil (thickness: 20 μm, width: 200 mm) serving as a positive electrode current collector, and then dried. Next, a coating mass of 19.0 mg / cm was similarly applied to a portion of the opposite side (uncoated side). 2 The positive electrode mixture slurry was applied to an aluminum foil so as to become a thickness of 100 μm and then dried. The thus obtained double-sided coated aluminum foil (the total coating amount on both sides is 38.0 mg / cm 2 ) was dried in a vacuum drying oven at 130°C for 12 hours.

[0106] -press- The double-sided coated aluminum foil after drying was pressed in a 35-ton press to a press density of 2.9±0.05g / cm 3 It was pressed to be.

[0107] -slit- The double-sided coated aluminum foil after pressing was slit so as to obtain a coated portion (40 mm×29 mm) and a tab welding margin, thereby obtaining a positive electrode.

[0108] (Preparation of negative electrode) -Slurry preparation- A 5 L Planetary Disperser was used to prepare the slurry. 960 g of natural graphite as the negative electrode active material and Super-P (conductive carbon, BET specific surface area 62 m) as the conductive additive. 2 To 10 g of the cellulose acetate solution (1% by mass / g), 450 g of a 1% CMC aqueous solution (that is, a 1% by mass aqueous solution of carboxymethyl cellulose (CMC)) was added, and the mixture was mixed for 30 minutes. To the obtained mixture, 300 g of a 1% CMC aqueous solution was added and kneaded for 30 minutes, and then 250 g of a 1% CMC aqueous solution was added and kneaded for 30 minutes. To the obtained kneaded product, 50 g of styrene butadiene rubber (SBR) (40% emulsion) as a binder was added and mixed for 30 minutes, and then vacuum degassing was performed for 30 minutes. In this manner, a negative electrode mixture slurry having a solid content of 45% was obtained.

[0109] - Coating and drying - A die coater was used for applying the slurry. The coating mass after drying is 11.0mg / cm 2 The negative electrode mixture slurry was applied to a part of one side of a copper foil (thickness: 10 μm) serving as a negative electrode current collector, and then dried. Next, a coating mass of 11.0 mg / cm was applied to a part of the opposite side (uncoated side) of the copper foil. 2 The negative electrode mixture slurry was applied and dried so that The double-sided coated copper foil obtained in this way (the total coating amount on both sides is 22.0 mg / cm 2 ) was dried in a vacuum drying oven at 120°C for 12 hours.

[0110] -press- After drying, the double-sided coated copper foil was pressed in a small press until the density reached 1.45±0.05g / cm 3 It was pressed to be.

[0111] -slit- The double-sided coated copper foil after pressing was slit so as to obtain a coated portion (42 mm×31 mm) and a tab welding margin, thereby obtaining a negative electrode.

[0112] (Preparation of stacked battery precursor) The separator used was a polyethylene porous film (50 mm×50 mm) with a porosity of 45% and a thickness of 25 μm. A negative electrode (front surface), a separator, a positive electrode (rear surface / front surface), a separator, and a negative electrode (front surface) were stacked and fixed in order to obtain a laminate. An aluminum tab was bonded to the margin of the positive electrode of the obtained laminate as a positive electrode tab using an ultrasonic bonding machine, and a nickel tab was bonded to the margin of the negative electrode as a negative electrode tab using an ultrasonic bonding machine. The laminate with the bonded positive electrode tab and negative electrode tab was sandwiched between laminate sheets, and three sides were heat sealed to obtain a laminate.

[0113] The inside of the laminate obtained above was dried under reduced pressure for 12 hours at 70° C. in a vacuum dryer. After the reduced pressure drying, 1.20±0.05 g of the nonaqueous electrolyte was injected into the remaining side of the laminate not heat-sealed, and the remaining side was then heat-sealed while drawing a vacuum to obtain a stacked battery precursor (i.e., a stacked battery before being charged and discharged).

[0114] (Fabrication of stacked batteries) The laminated battery precursor was kept in the atmosphere at 25° C. for 24 hours, then charged at a constant current of 0.1 C (0.1C-CC) for 3 hours, and then allowed to rest at 25° C. for 12 hours. Next, the stacked battery precursor after resting was charged at a constant current and constant voltage of 0.1C (0.1C-CCCV) to 4.2V (SOC 100%), rested for 30 minutes, and then discharged at a constant current of 0.1C (0.1C-CC) to 2.8V to obtain a stacked battery.

[0115] <Evaluation of heat generation rate inside the battery during short circuit> The laminated battery was subjected to the following nail penetration test to evaluate the heat generation rate inside the battery when a short circuit occurred.

[0116] (Nail penetration test) The laminated battery prepared above was charged at 0.1 C to 4.2 V (SOC 100%) at constant current and constant voltage (0.1 C-CCCV) and subjected to a nail penetration test. A nail having a diameter of 3 mm, a length of 15 mm, a tip angle of 30°, and a bottomed hole of 0.6 mm in diameter was covered with Macol (registered trademark). Next, a sheath type K thermocouple (product number: IP10-K-0.5-200) with a sheath diameter of 0.5 mm and a sheath length of 200 mm was inserted to a position near the tip of the nail to obtain a nail penetration test tool. The nail test tool and the stacked battery were fixed to a nail penetration test device (TYS-94DM45 manufactured by Toyo Systems), and the nail was inserted into the center of the battery (cell) at a speed of 1 mm / sec, shorting the positive and negative electrodes inside the battery container. The temperature inside the battery measured by the nail penetration test tool and the surface temperature obtained from a thermocouple attached to the surface of the battery were measured over time.

[0117] -Calculation of heat generation rate- The heat generation rate of the battery was calculated as shown below from the measurement results of the nail penetration test described above. The time when the internal temperature of the battery rose by 0.2°C after short circuit was defined as the heat generation start time T0 (seconds), and 1 second after T0 was defined as T1 (seconds). The internal temperature of the battery at T0 was defined as H0 (°C), and the internal temperature of the battery at T1 was defined as H1 (°C), and the heat generation rate immediately after short circuit was calculated using the following formula. Heat release rate: (H1-H0) / (T1-T0)

[0118] The heat release rate results are shown in Table 1. The heat release rate results are: The heat release rate is shown as a relative value X with the value of 100 being the heat release rate in Comparative Example A in which neither the compound (P) nor the compound (C) was contained, but only VC was contained. The heat release rate was shown as a relative value Y, assuming that the heat release rate in the comparative example in which compound (C) was not contained and only compound (P) and VC were contained (Comparative Example 1-1 in the case of this Example 1-1) was 100. The same applies to other embodiments described below.

[0119] <Preparation of lithium secondary battery (coin type battery)> As the lithium secondary battery, a coin-type battery for evaluating the battery resistance was fabricated. Details are given below.

[0120] (Preparation of positive electrode) LiNi as a positive electrode active material 0.5 Mn 0.3 Co 0.2 A mixture of O2 (92 parts by mass), Super-P (conductive carbon manufactured by TIMCAL) (2 parts by mass) as a conductive additive, KS-6 (flake graphite manufactured by TIMREX) (2 parts by mass) as a conductive additive, and polyvinylidene fluoride (4 parts by mass) as a binder was dispersed in N-methylpyrrolidinone as a solvent to prepare a paste-like positive electrode mixture slurry. Next, this positive electrode mixture slurry was applied to a strip-shaped aluminum foil (positive electrode current collector) having a thickness of 20 μm, dried, and then rolled with a roll press to obtain a sheet-shaped positive electrode consisting of the positive electrode current collector and the positive electrode active material layer. The applied mass of the positive electrode active material layer at this time was 19.0 mg / cm. 2 and the press density is 2.9±0.05g / cm 3 It was.

[0121] (Preparation of negative electrode) Natural graphite (96 parts by mass) as the negative electrode active material, Super-P (1 part by mass) as a conductive additive, sodium carboxymethylcellulose dispersed in pure water (1 part by mass as solid content) as a thickener, and styrene-butadiene rubber (SBR) dispersed in pure water (2 parts by mass) as a binder were added and mixed to obtain a paste-like negative electrode mixture slurry. Next, the obtained negative electrode mixture slurry was applied to a strip-shaped copper foil (negative electrode current collector) having a thickness of 10 μm, dried, and then rolled with a roll press to obtain a sheet-shaped negative electrode consisting of the negative electrode current collector and the negative electrode active material layer. The coating mass of the negative electrode active material layer at this time was 11.0 mg / cm. 2 and the press density is 1.45±0.05g / cm 3 It was.

[0122] (Preparation of separator) A microporous polyethylene film having a thickness of 20 μm was punched out into a disk having a diameter of 17 mm to obtain a coin-shaped separator.

[0123] (Preparation of coin cell precursor) The above-mentioned negative electrode was punched out into a disk shape having a diameter of 14 mm, and the above-mentioned positive electrode was punched out into a disk shape having a diameter of 13 mm, to obtain a coin-shaped negative electrode and a coin-shaped positive electrode, respectively. The obtained coin-shaped positive electrode, separator, and coin-shaped negative electrode were stacked in this order in a stainless steel battery can (size 2032), and then 20 μL of the above-mentioned nonaqueous electrolyte was poured into the battery can to impregnate the separator, positive electrode, and negative electrode. Next, a SUS plate (thickness 0.5 mm, diameter 16 mm) and a spring were placed on the negative electrode, and the battery was sealed by crimping the battery can lid with a polypropylene gasket interposed therebetween. As a result of the above, a coin-type battery precursor (i.e., a coin-type battery before charging and discharging) having the configuration shown in Figure 3 with a diameter of 20 mm and a height of 3.2 mm was obtained as a lithium secondary battery precursor (i.e., a lithium secondary battery before charging and discharging).

[0124] (Making coin-cell batteries) The coin battery precursor was subjected to three cycles of charging and discharging between 2.8 V and 4.2 V at 25° C. in a thermostatic chamber to obtain a coin battery.

[0125] <Evaluation of battery resistance> The coin-type batteries were evaluated for battery resistance as follows. The coin battery was charged to a constant voltage of 4.2 V at room temperature, and then discharged at a constant current of 0.1 C at room temperature, and the first potential drop was measured for 10 seconds from the start of discharge. The coin battery was charged to a constant voltage of 4.2 V at room temperature, and then discharged at a constant current of 0.2 C at room temperature, and the second potential drop was measured for 10 seconds from the start of discharge. The coin battery was charged to a constant voltage of 4.2 V at room temperature, and then discharged at a constant current of 0.5 C at room temperature, and the amount of decrease in the third potential was measured for 10 seconds from the start of discharge. The coin battery was charged to a constant voltage of 4.2 V at room temperature, and then discharged at a constant current of 1.0 C at room temperature, and the amount of decrease in the fourth potential was measured for 10 seconds from the start of discharge. The battery resistance (direct current resistance; DCIR) at the beginning of discharge was calculated from the first potential drop amount to the fourth potential drop amount when discharging at each current rate.

[0126] The results of the battery resistance (DCIR) are shown in Table 1. The battery resistance (DCIR) result is The battery resistance (DCIR) of Comparative Example A, which did not contain the compound (P) and the compound (C) but contained only VC, was taken as 100, and the relative value X was calculated. The battery resistance (DCIR) in a comparative example in which compound (C) was not contained and only compound (P) and VC were contained (Comparative Example 1-1 in the case of this Example 1-1) was taken as 100, and the relative value Y was calculated. The same applies to other embodiments described below.

[0127] [Comparative Example A, Comparative Example 1-1, Examples 1-2 to 1-3, Comparative Example 2-1, Examples 2-1 to 2-6, Comparative Example 2-2, Example 2-7, Comparative Example 3-1, Examples 3-1 to 3-6, Comparative Example 3-2, Examples 3-7 to 3-8, Comparative Example 4-1, Examples 4-1 to 4-3, Comparative Example 4-2, Example 4-4] The same operations as in Example 1-1 were performed except that the combinations of the presence or absence of compound (P) as an additive, the type and amount of compound (P), the presence or absence of compound (C) as an additive, and the type and amount of compound (C) were changed as shown in Table 1. The results are shown in Table 1. In addition, in all the examples, the non-aqueous electrolyte contains 0.5 wt % of VC.

[0128] The additives in Table 1 are as follows: In the compound (P-3), m is 1, and in the compound (P-4), x is 1.

[0129] [ka]

[0130] [Table 1]

[0131] As shown in Table 1, in each of the examples using a nonaqueous electrolyte solution containing compound (P) (i.e., a compound represented by formula (P)) and compound (C) (i.e., a compound represented by formula (C)), which is a sulfate ester compound, it was possible to reduce the heat generation rate during short circuit while suppressing the deterioration of battery performance (specifically, in these examples, an increase in battery resistance). For example, compared to the nonaqueous electrolyte of Comparative Example A containing neither compound (P) nor compound (C), the nonaqueous electrolyte of Comparative Example 1-1 to which compound (P) was added reduced the heat generation rate during short-circuiting of the battery, but increased the battery resistance (see comparison between Comparative Example A and Comparative Example 1-1). The nonaqueous electrolyte solutions of Examples 1-1 to 1-3, in which compound (C) was further added to the nonaqueous electrolyte solution of Comparative Example 1-1, further reduced the heat generation rate upon short-circuiting of the battery, and also suppressed an increase in battery resistance (see comparison between Comparative Example 1-1 and Examples 1-1 to 1-3). These trends are Comparison of Comparative Example A, Comparative Example 2-1, and Examples 2-1 to 2-6. Comparison of Comparative Example A, Comparative Example 2-2, and Example 2-7; Comparison of Comparative Example A, Comparative Example 3-1, and Examples 3-1 to 3-6. Comparison of Comparative Example A, Comparative Example 3-2, and Examples 3-7 to 3-8. Comparison of Comparative Example A, Comparative Example 4-1, and Examples 4-1 to 4-3, and This can also be confirmed by comparing Comparative Example A, Comparative Example 4-2, and Example 4-4.

[0132] The disclosure of Japanese Patent Application No. 2021-094572, filed on June 4, 2021, is incorporated by reference in its entirety into this specification. All publications, patent applications, and standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A non-aqueous electrolyte solution for a battery, comprising a compound represented by the following formula (P) and a sulfate ester compound: 【Chemistry 1】 [In formula (P), R １ ~R ４ each independently represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms; L １ represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 12 carbon atoms; and n represents 1 or 2. When n is 2, two R ４ may be the same or different, and two L １ may be the same or different.

2. The compound represented by formula (P) includes at least one selected from the group consisting of the following compounds (P-3) and (P-4): 【Chemistry 2】 [In compound (P-3), m represents 1 or 2, and in compound (P-4), x represents 1 or 2.]

3. The nonaqueous electrolyte for a battery according to claim 1 or 2, wherein the sulfate ester compound comprises a cyclic sulfate ester compound.

4. The nonaqueous electrolyte for a battery according to claim 1 or 2, wherein the sulfate ester compound comprises a compound represented by the following formula (C): 【Chemistry 3】 [In formula (C), R ｃ１ ~R ｃ４ each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, a group represented by formula (a), or a group represented by formula (b). In formulas (a) and (b), * represents a bonding position.

5. The compound represented by formula (C) includes at least one selected from the group consisting of the following compound (C-1) and the following compound (C-4): 【Chemistry 4】

6. A composition comprising a compound represented by the following formula (P) and a sulfate ester compound: The sulfate ester compound includes at least one selected from the group consisting of the following compound (C-1) and the following compound (C-2): Non-aqueous electrolyte for batteries. 【Chemistry 5】 [In formula (P), R 1 to R 4 each independently represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, L 1 represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 12 carbon atoms, and n represents an integer of 0 to 2. When n is 2, two R 4 s may be the same or different, and two L 1 s may be the same or different. 【Chemistry 6】

7. The non-aqueous electrolyte for a battery described in claim 6, wherein the compound represented by formula (P) includes at least one selected from the group consisting of the following compound (P-1), the following compound (P-2), the following compound (P-3), and the following compound (P-4). 【Chemistry 7】 [In compound (P-3), m represents 1 or 2, and in compound (P-4), x represents 1 or 2.]

8. 7. The nonaqueous electrolyte solution for a battery according to claim 1, wherein a ratio of the number of sulfate groups contained in the total amount of the sulfate ester compounds to the number of phosphate groups contained in the total amount of the compounds represented by formula (P), [sulfate groups / phosphate groups], is greater than 0 and not greater than 3.

00.

9. The non-aqueous electrolyte solution for a battery according to claim 1 or 6, wherein the content of the compound represented by formula (P) is 0.1 mass % to 1.0 mass % based on the total amount of the non-aqueous electrolyte solution for a battery.

10. 7. The nonaqueous electrolyte for a battery according to claim 1, further comprising a cyclic carbonate compound containing a carbon-carbon unsaturated bond.

11. A positive electrode and A negative electrode; The nonaqueous electrolyte for a battery according to claim 1 or 6, A lithium secondary battery precursor comprising:

12. Providing a lithium secondary battery precursor according to claim 11; obtaining a lithium secondary battery by charging and discharging the lithium secondary battery precursor; A method for producing a lithium secondary battery, comprising:

13. A lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor according to claim 11.

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