Additive for lithium secondary batteries, non-aqueous electrolyte for lithium secondary batteries, lithium secondary battery precursor, lithium secondary battery, and method for manufacturing lithium secondary batteries

Abstract

To provide an additive for lithium secondary batteries that can inhibit shortage of battery capacity after high temperature storage of lithium secondary batteries and also inhibit increase in battery resistance after the high temperature storage.SOLUTION: An additive for lithium secondary batteries contains a compound (I) represented by a formula (I) in the figure. In the formula, R1 represents a C1-10 alkyl group, a C2-10 alkenyl group, a C2-10 alkynyl group, an aryl group, or an aralkyl group, where, in these groups, at least one hydrogen atom may be substituted.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an additive for a lithium secondary battery, a non-aqueous electrolyte for a lithium secondary battery, a lithium secondary battery precursor, a lithium secondary battery, and a method for manufacturing a lithium secondary battery.

Background Art

[0002] In recent years, studies have been made on power storage devices such as lithium secondary batteries. For example, in Patent Document 1, as a non-aqueous electrolyte for a power storage device that reduces electrical resistance and has excellent cycle characteristics, a non-aqueous electrolyte for a power storage device obtained by dissolving an electrolyte in a non-aqueous solvent, wherein the electrolyte is a lithium salt dissolved in the non-aqueous solvent and contains one or more selected from the group consisting of organic sulfone compounds having a specific structure is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of the studies by the present inventors, it has been found that a lithium secondary battery containing the non-aqueous electrolyte described in Patent Document 1 may have insufficient battery capacity and / or too high battery resistance after high-temperature storage.

[0005] An object of one aspect of the present disclosure is to provide an additive for a lithium secondary battery, a non-aqueous electrolyte for a lithium secondary battery, a lithium secondary battery precursor, a lithium secondary battery, and a method for manufacturing a lithium secondary battery that can suppress insufficient battery capacity after high-temperature storage of the lithium secondary battery and can suppress an increase in battery resistance after the high-temperature storage.

Means for Solving the Problems

[0006] The following embodiments are included as means for solving the above problems.

[0007] <1> An additive for lithium secondary batteries, comprising compound (I) represented by the following formula (I).

[0008] [ka]

[0009] [In formula (I), R 1 This represents an alkyl group having 1 to 10 carbon atoms (at least one hydrogen atom of the alkyl group may be substituted with a halogen atom), an alkenyl group having 2 to 10 carbon atoms (at least one hydrogen atom of the alkenyl group may be substituted with a halogen atom), an alkynyl group having 2 to 10 carbon atoms (at least one hydrogen atom of the alkynyl group may be substituted with a halogen atom), an aryl group (at least one hydrogen atom of the aryl group may be substituted with a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms), or an aralkyl group (at least one hydrogen atom of the aromatic ring of the aralkyl group may be substituted with a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms).

[0010] <2> The aforementioned R 1 However, it is an alkyl group having 1 to 10 carbon atoms (at least one hydrogen atom of the alkyl group may be substituted with a halogen atom). <1> Additives for lithium secondary batteries as described above. <3> <1> or <2> A non-aqueous electrolyte for lithium secondary batteries containing the lithium secondary battery additive described above. <4> The compound further comprises at least one selected from the group consisting of compound (II), which is at least one of lithium monofluorophosphate and lithium difluorophosphate, compound (III), which is represented by the following formula (III), and compound (IV), which is represented by the following formula (IV). <3> Non-aqueous electrolyte for lithium secondary batteries as described above.

[0011]

Chemical formula

[0012] In formula (III), M is an alkali metal, Y is a transition element, a Group 13 element, a Group 14 element, or a Group 15 element of the periodic table, b is an integer from 1 to 3, m is an integer from 1 to 4, n is an integer from 0 to 8, q is 0 or 1, R 31 is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups may contain a substituent or a heteroatom in the structure, and when q is 1 and m is 2 to 4, m R 31 may be bonded to each other.) R 32 is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms (these groups may contain a substituent or a heteroatom in the structure, and when n is 2 to 8, n R 32 may be bonded to each other to form a ring.) Q 1 and Q 2 are each independently an oxygen atom or a carbon atom. In formula (IV), R 41 is an oxygen atom, an alkylene group having 1 to 6 carbon atoms, or an alkenylene group having 2 to 6 carbon atoms, R 42 is an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by formula (iv-1), or a group represented by formula (iv-2), * indicates the bonding position, In formula (iv-1), R 43This is an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group. In formula (iv-2), R 44 This is an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms.

[0013] <5> The content of compound (I) is 0.01% by mass or more and 5.0% by mass or less, relative to the total amount of the non-aqueous electrolyte. <3> or <4> Non-aqueous electrolyte for lithium secondary batteries as described above. <6> The case and The case contains a positive electrode, a negative electrode, a separator, and an electrolyte, Equipped with, The positive electrode is a positive electrode capable of intercalating and releasing lithium ions. The aforementioned negative electrode is a negative electrode capable of intercalating and releasing lithium ions. The aforementioned electrolyte, <3> ~ <5> A lithium secondary battery precursor, which is a non-aqueous electrolyte as described in any one of the following. <7> The positive electrode contains a lithium-containing composite oxide represented by the following formula (P1) as the positive electrode active material. <6> A lithium secondary battery precursor as described above. LiRing a Co b Mn c O2… Formula (P1) [In equation (P1), a, b, and c are each independently greater than 0 and less than 1, and the sum of a, b, and c is between 0.99 and 1.00.] <8> <6> or <7> The process of preparing the lithium secondary battery precursor described above, The process involves charging and discharging the lithium secondary battery precursor. A method for manufacturing lithium secondary batteries, including [the specified component]. <9> <6> or <7> A lithium secondary battery obtained by subjecting the lithium secondary battery precursor described above to charging and discharging. [Effects of the Invention]

[0014] This disclosure provides an additive for lithium secondary batteries, a non-aqueous electrolyte for lithium secondary batteries, a lithium secondary battery precursor, a lithium secondary battery, and a method for manufacturing a lithium secondary battery, which can suppress the deficiency of battery capacity after high-temperature storage of lithium secondary batteries and suppress the increase in battery resistance after high-temperature storage. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view showing a laminate-type battery, which is an example of a lithium secondary battery precursor of the present disclosure. [Figure 2] This is a schematic cross-sectional view showing a coin-type battery, which is another example of a lithium secondary battery precursor in this disclosure. [Modes for carrying out the invention]

[0016] In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In this specification, the amount of each component in a composition means the total amount of any multiple substances present in the composition, unless otherwise specified. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their intended purpose is achieved.

[0017] [Additives for lithium secondary batteries] The lithium secondary battery additive of this disclosure comprises at least one compound (I) represented by the following formula (I).

[0018] [ka]

[0019] In formula (I), R 1This represents an alkyl group having 1 to 10 carbon atoms (at least one hydrogen atom of the alkyl group may be substituted with a halogen atom), an alkenyl group having 2 to 10 carbon atoms (at least one hydrogen atom of the alkenyl group may be substituted with a halogen atom), an alkynyl group having 2 to 10 carbon atoms (at least one hydrogen atom of the alkynyl group may be substituted with a halogen atom), an aryl group (at least one hydrogen atom of the aryl group may be substituted with a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms), or an aralkyl group (at least one hydrogen atom of the aromatic ring of the aralkyl group may be substituted with a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms).

[0020] The additive for lithium secondary batteries of this disclosure can suppress the deficiency of battery capacity after high-temperature storage of lithium secondary batteries, and can also suppress the increase in battery resistance after high-temperature storage. This effect is thought to be brought about by the combination of the -SO2- group, the -C(=O)O- group, and the -CF3 group bonded to the -SO2- group in compound (I).

[0021] The lithium secondary battery additives of this disclosure are, in particular, preferably additives for the non-aqueous electrolyte of the lithium secondary battery.

[0022] In formula (I), R 1 The "C1-C10 alkyl group" represented by is a linear or branched alkyl group having 1 to 10 carbon atoms. Examples of "C1-C10 alkyl groups" include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, 2-methylbutyl, 1-methylpentyl, neopentyl, 1-ethylpropyl, hexyl, 3,3-dimethylbutyl, heptyl, octyl, nonyl, and decyl groups. Among these, C1-C6 alkyl groups are preferred, and C1-C4 alkyl groups are more preferred. At least one hydrogen atom of the "alkyl group having 1 to 10 carbon atoms" may be substituted with a halogen atom. Preferred halogen atoms are fluorine, chlorine, bromine, or iodine; more preferably fluorine, chlorine, or bromine; even more preferably fluorine or chlorine; and even more preferably fluorine. In the "alkyl group having 1 to 10 carbon atoms," the number of hydrogen atoms substituted for the halogen atom is not particularly limited and can be appropriately selected according to the number of carbon atoms in the alkyl group, with 1 to 7 being preferred.

[0023] In formula (I), R 1 The "C2-C10 alkenyl group" represented by is a linear or branched alkenyl group having 2 to 10 carbon atoms. Examples of "C2-C10 alkenyl groups" include vinyl, 2-propenyl, 2-butenyl, 3-butenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, and 5-hexenyl groups. Among these, "C2-C10 alkenyl groups" are preferably C2-C6 alkenyl groups, and more preferably C2-C4 alkenyl groups. At least one hydrogen atom of the "alkenyl group having 2 to 10 carbon atoms" may be substituted with a halogen atom. Preferred halogen atoms are fluorine, chlorine, bromine, or iodine; more preferably fluorine, chlorine, or bromine; even more preferably fluorine or chlorine; and even more preferably fluorine. In the "alkenyl group having 2 to 10 carbon atoms," the number of hydrogen atoms substituted by halogen atoms is not particularly limited and can be appropriately selected according to the number of carbon atoms in the alkenyl group, with 1 to 7 being preferred.

[0024] In formula (I), R 1The "alkynyl group having 2 to 10 carbon atoms" is a linear or branched alkynyl group having 2 to 10 carbon atoms. Examples of "alkynyl groups having 2 to 10 carbon atoms" include ethynyl group, propargyl group (2-propynyl group), 2-butynyl group, 3-butynyl group, 2-pentynyl group, 3-pentynyl group, 4-pentynyl group, and 5-hexynyl group. Among these, the "alkynyl group having 2 to 10 carbon atoms" is preferably an alkynyl group having 2 to 6 carbon atoms, and more preferably an alkynyl group having 2 to 4 carbon atoms. At least one hydrogen atom of the "alkynyl group having 2 to 10 carbon atoms" may be substituted with a halogen atom. Preferred halogen atoms are fluorine, chlorine, bromine, or iodine; more preferably fluorine, chlorine, or bromine; even more preferably fluorine or chlorine; and even more preferably fluorine. In the "alkynyl group having 2 to 10 carbon atoms," the number of hydrogen atoms substituted for halogen atoms is not particularly limited and can be appropriately selected according to the number of carbon atoms in the alkynyl group, with 1 to 7 being preferred.

[0025] In formula (I), R 1 At least one hydrogen atom of the "aryl group" represented by may be substituted with a halogen atom, a carbon-1 to carbon-6 alkoxy group, or a carbon-1 to carbon-6 alkyl group. The halogen atom is preferably a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; more preferably a fluorine atom, a chlorine atom, or a bromine atom; even more preferably a fluorine atom or a chlorine atom; and even more preferably a fluorine atom. In the "aryl group," the number of hydrogen atoms substituted for the halogen atom is not particularly limited, but is preferably 1 to 5. The alkoxy group having 1 to 6 carbon atoms may have a linear, branched, or cyclic alkyl group. Examples of alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, t-butoxy, and pentyloxy groups. Among these, alkoxy groups having 1 to 3 carbon atoms are preferred, with methoxy and ethoxy groups being more preferred. In the "aryl group," the number of hydrogen atoms substituted by the alkoxy group having 1 to 6 carbon atoms is not particularly limited, but 1 to 3 is preferred. The C1-C6 alkyl group may be linear, branched, or cyclic. Examples of C1-C6 alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, n-hexyl, and cyclohexyl groups. Among these, C1-C6 alkyl groups are preferably C1-C3 alkyl groups, with methyl and ethyl groups being more preferred. In the "aryl group," the number of hydrogen atoms substituted by the C1-C6 alkyl group is not particularly limited, but 1 to 3 is preferred.

[0026] In formula (I), R 1 It is preferably an alkyl group having 1 to 10 carbon atoms (at least one hydrogen atom of the alkyl group may be substituted with a halogen atom), more preferably an unsubstituted alkyl group having 1 to 10 carbon atoms, even more preferably an unsubstituted alkyl group having 1 to 6 carbon atoms, and still more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms.

[0027] The following are specific examples of compound (I) (compounds (I-1) to (I-4)), but compound (I) is not limited to these examples.

[0028] [ka]

[0029] The following is an example of how to prepare compound (I). In formula (I), R 1However, compound (I) in the case of a methyl group, ethyl group, allyl group, benzyl group, t-butyl group, or cyclohexyl group is, for example, Journal of Fluorine Chemistry, 1994, 66(3),301-9, Journal of Fluorine Chemistry, 2013, 153, 151-161, and, CN111253292 A 2020-06-09 It can be manufactured by following the method described in [reference].

[0030] Furthermore, compound (I) can be reacted in, for example, the following reaction scheme. to As shown, it can also be produced by reacting the following compound (xx) and the following compound (yy) in the presence of the following compound (zz).

[0031] [ka]

[0032] In compound (xx), M represents either Na or K. In compound (yy), X represents Cl, Br, or I. In compound (yy), R 1 This is R in compound (I). 1 This is synonymous with the same as the preferred configuration. Compound (zz) is R4N + It represents NaI or KI. Here, R4N + In this case, R is R in compound (I). 1 This is synonymous with the same as the preferred embodiment. However, R4N + R in compound (I) and R in compound (I) 1 These may be the same or different.

[0033] The above reaction scheme to In the described manufacturing method, there are no particular restrictions on the reaction solvent. Examples of reaction solvents include single solvents or mixed solvents containing at least one selected from the group consisting of esters (e.g., ethyl acetate), acetonitrile, and dimethylacetamide. Examples of compound (yy) include methyl bromoacetate, ethyl bromoacetate, n-propyl bromoacetate, i-propyl bromoacetate, n-butyl bromoacetate, t-butyl bromoacetate, allyl bromoacetate, benzyl bromoacetate, methyl chloroacetate, ethyl chloroacetate, n-propyl chloroacetate, i-propyl chloroacetate, n-butyl chloroacetate, t-butyl chloroacetate, allyl chloroacetate, and benzyl chloroacetate. The above reaction scheme to The reaction can be carried out, for example, in the range of -20°C to the reflux temperature of the reaction system, preferably 40 to 100°C. The reaction time for the reaction shown in the above reaction scheme can be, for example, in the range of 0.5 hours to 48 hours, and preferably 0.5 to 24 hours.

[0034] [Non-aqueous electrolyte for lithium secondary batteries] The non-aqueous electrolyte for lithium secondary batteries of this disclosure (hereinafter also simply referred to as "non-aqueous electrolyte") contains the additive for lithium secondary batteries of this disclosure (hereinafter also referred to as "additive (A)"). The non-aqueous electrolyte of this disclosure provides effects similar to those of the additive for lithium secondary batteries of this disclosure (i.e., it can suppress the deficiency of battery capacity after high-temperature storage of lithium secondary batteries, and it can suppress the increase in battery resistance after high-temperature storage).

[0035] Additive (A) contains at least one compound (I). In other words, the non-aqueous electrolyte of this disclosure comprises at least one compound (I).

[0036] From the viewpoint of achieving the above effects more effectively, the content of compound (I) is preferably 0.01% by mass or more and 5.0% by mass or less, relative to the total amount of the non-aqueous electrolyte. The upper limit of the content of compound (I) is more preferably 3.0% by mass, and even more preferably 1.5% by mass, based on the total amount of the non-aqueous electrolyte. The lower limit of the content of compound (I) is more preferably 0.05% by mass, even more preferably 0.10% by mass, and even more preferably 0.20% by mass, relative to the total amount of the non-aqueous electrolyte.

[0037] Furthermore, when analyzing non-aqueous electrolytes collected from disassembled lithium secondary batteries, the amount of compound (I) may be less than the amount added to the non-aqueous electrolyte. Even in this case, if even a small amount of compound (I) is detected in the non-aqueous electrolyte extracted from the lithium secondary battery, the electrolyte of that lithium secondary battery is included within the scope of non-aqueous electrolytes as defined in this disclosure.

[0038] <Additive (B)> The non-aqueous electrolyte of this disclosure preferably further comprises at least one compound (II) which is at least one of lithium monofluorophosphate and lithium difluorophosphate, compound (III) which is represented by formula (III) described below, and compound (IV) which is represented by formula (IV) described below (hereinafter also referred to as "additive (B)" in this disclosure). If the non-aqueous electrolyte of this disclosure contains additive (B), the effects of the non-aqueous electrolyte of this disclosure are more effectively achieved.

[0039] If the non-aqueous electrolyte contains additive (B), the content of additive (B) is preferably more than 0% by mass and 5.0% by mass or less, and more preferably 0.001% by mass or more and 5.0% by mass or less, based on the total amount of the non-aqueous electrolyte. The upper limit of the content of additive (B) is more preferably 3.0% by mass, and more preferably 2.0% by mass, relative to the total amount of the non-aqueous electrolyte. The lower limit of the content of additive (B) is more preferably 0.01% by mass, and even more preferably 0.1% by mass, relative to the total amount of the non-aqueous electrolyte.

[0040] (Compound (II)) Compound (II) is at least one of lithium monofluorophosphate and lithium difluorophosphate. Lithium difluorophosphate is compound (II-1) below, and lithium monofluorophosphate is compound (II-2) below.

[0041] [ka]

[0042] Compound (II) may be lithium monofluorophosphate and lithium difluorophosphate alone, or both lithium monofluorophosphate and lithium difluorophosphate.

[0043] If the non-aqueous electrolyte of this disclosure contains compound (II), the content of compound (II) is preferably more than 0% by mass and 5.0% by mass or less, and more preferably 0.001% by mass or more and 5.0% by mass or less, based on the total amount of the non-aqueous electrolyte. The upper limit of the content of compound (II) is more preferably 3.0% by mass, and even more preferably 2.0% by mass. The lower limit of the content of compound (II) is more preferably 0.01% by mass, and even more preferably 0.1% by mass.

[0044] (Compound (III)) Compound (III) is a compound represented by the following formula (III).

[0045] [ka]

[0046] In formula (III), M is an alkali metal, Y is a transition element, a group 13, group 14, or group 15 element of the periodic table. b is an integer between 1 and 3. m is an integer between 1 and 4. n is an integer between 0 and 8. q is either 0 or 1, R 31 This is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups may contain substituents or heteroatoms in their structure, and when q is 1 and m is 2 to 4, there are m R 31 They may be joined together.) R 32 This includes halogen atoms, C1-C10 alkyl groups, C1-C10 halogenated alkyl groups, C6-C20 aryl groups, or C6-C20 halogenated aryl groups (these groups may contain substituents or heteroatoms in their structure, and if n is 2-8, there are n R 32 They may each be joined together to form a ring. Q 1 , and Q 2 These are, independently, either an oxygen atom or a carbon atom.

[0047] M is an alkali metal. Examples of alkali metals include lithium, sodium, and potassium. Of these, M is preferably lithium. Y is a transition element, a group 13, group 14, or group 15 element of the periodic table. Preferably, Y is Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf, or Sb, and more preferably Al, B, or P. When Y is Al, B, or P, the synthesis of the anionic compound becomes relatively easy, and manufacturing costs can be reduced. b represents the valency of the anion and the number of cations. b is an integer between 1 and 3, and is preferably 1. If b is 3 or less, the salt of the anionic compound is easily soluble in the mixed organic solvent. m and n are values ​​related to the number of ligands. Each of m and n is determined by the type of M. m is an integer from 1 to 4. n is an integer from 0 to 8. q is either 0 or 1. When q is 0, the chelate ring is a five-membered ring, and when q is 1, the chelate ring is a six-membered ring. R 31 R represents an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups, halogenated alkylene groups, arylene groups, or halogenated arylene groups may contain substituents or heteroatoms in their structure. Specifically, R 31 These groups may contain substituents instead of hydrogen atoms. Substituents include halogen atoms, linear or cyclic alkyl groups, aryl groups, alkenyl groups, alkoxy groups, aryloxy groups, sulfonyl groups, amino groups, cyano groups, carbonyl groups, acyl groups, amide groups, or hydroxyl groups. These groups may also have structures in which nitrogen atoms, sulfur atoms, or oxygen atoms are introduced instead of the carbon element. When q is 1 and m is 2-4, there are m R 31 These components may be bonded together. An example of such a ligand is ethylenediaminetetraacetic acid. R 32 R represents a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkyl halide having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aryl halide having 6 to 20 carbon atoms. These alkyl groups, alkyl halides, aryl groups, or aryl halides are R 31 Similarly, the structure may contain substituents and heteroatoms, and when n is 2 to 8, there are n R 32 These may each be joined to form a ring. 32 As such, electron-withdrawing groups are preferred, and fluorine atoms are particularly preferred. Q 1 and Q 2 Each of these elements independently represents either O or C. Therefore, the ligand will bond to Y via these heteroatoms.

[0048] Specific examples of compound (III) include the following compounds (III-1) and (III-2).

[0049] [ka]

[0050] If the non-aqueous electrolyte of this disclosure contains compound (III), the content of compound (III) is preferably more than 0% by mass and 5.0% by mass or less, and more preferably 0.001% by mass or more and 5.0% by mass or less, based on the total amount of the non-aqueous electrolyte. The upper limit of the content of compound (II) is more preferably 3.0% by mass, and even more preferably 2.0% by mass. The lower limit of the content of compound (II) is more preferably 0.01% by mass, and even more preferably 0.1% by mass.

[0051] (Compound (IV)) Compound (IV) is a compound represented by the following formula (IV).

[0052] [ka]

[0053] In formula (IV), R 41 This is an oxygen atom, an alkylene group having 1 to 6 carbon atoms, or an alkenylene group having 2 to 6 carbon atoms. R 42 This is an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by formula (iv-1), or a group represented by formula (iv-2). * indicates the bonding position. In formula (iv-1), R 43 This is an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group. In formula (iv-2), R 44 This is an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms.

[0054] In formula (IV), R 41It is preferably an alkylene group, vinylene group, or oxygen atom having 2 to 3 carbon atoms, more preferably a trimethylene group, vinylene group, or oxygen atom, and even more preferably an oxygen atom.

[0055] In formula (IV), R 42 It is preferable that the group is represented by formula (iv-1) or formula (iv-2). In formula (iv-1), R 43 The group is preferably an alkylene group having 1 to 3 carbon atoms, an alkenylene group having 1 to 3 carbon atoms, or an oxymethylene group, and more preferably an oxymethylene group. In formula (iv-2), R 44 It is preferably an alkyl group having 1 to 3 carbon atoms, or an alkenyl group having 2 to 3 carbon atoms, and more preferably a propyl group.

[0056] Specific examples of compound (IV) include compounds (IV-1) to (IV-8) listed below.

[0057] [ka]

[0058] If the non-aqueous electrolyte of this disclosure contains compound (IV), the content of compound (IV) is preferably more than 0% by mass and 5.0% by mass or less, and more preferably 0.001% by mass or more and 5.0% by mass or less, based on the total amount of the non-aqueous electrolyte. The upper limit of the content of compound (IV) is more preferably 3.0% by mass, and even more preferably 2.0% by mass. The lower limit of the content of compound (IV) is more preferably 0.01% by mass, and even more preferably 0.1% by mass.

[0059] <Other additives> The non-aqueous electrolyte of this disclosure may contain other additives. Other additives are not particularly limited, and any known additives can be used as desired. Other additives that can be used include, for example, those described in paragraphs 0042 to 0055 of Japanese Patent Publication No. 2019-153443.

[0060] <Non-aqueous solvent> Non-aqueous electrolytes generally contain a non-aqueous solvent. Various known non-aqueous solvents can be appropriately selected. There may be only one non-aqueous solvent or two or more.

[0061] Examples of non-aqueous solvents include cyclic carbonates, fluorinated cyclic carbonates, linear carbonates, fluorinated linear carbonates, aliphatic carboxylic acid esters, fluorinated aliphatic carboxylic acid esters, γ-lactones, fluorinated γ-lactones, cyclic ethers, fluorinated cyclic ethers, linear ethers, fluorinated linear ethers, nitriles, amides, lactams, nitromethane, nitroethane, sulfolanes, trimethyl phosphate, dimethyl sulfoxide, and dimethyl sulfoxide phosphate. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of fluorine-containing cyclic carbonates include fluoroethylene carbonate (FEC). Examples of linear carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC). Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylbutyrate, ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, ethyl isobutyrate, and ethyl trimethylbutyrate. Examples of γ-lactones include γ-butyrolactone and γ-valerolactone. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, and 1,4-dioxane. Examples of linear ethers include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, and 1,2-dibutoxyethane. Examples of nitriles include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, and 3-methoxypropionitrile. Examples of amides include N,N-dimethylformamide. Examples of lactam compounds include N-methylpyrrolidinone, N-methyloxazolidinone, and N,N'-dimethylimidazolidinone.

[0062] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates, fluorine-containing cyclic carbonates, linear carbonates, and fluorine-containing linear carbonates. In this case, the total proportion of cyclic carbonates, fluorinated cyclic carbonates, linear carbonates, and fluorinated linear 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, relative to the total amount of the non-aqueous solvent.

[0063] The non-aqueous solvent preferably contains at least one selected from the group consisting of cyclic carbonates and linear carbonates. In this case, the total proportion of cyclic carbonates and linear 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, relative to the total amount of the non-aqueous solvent.

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

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

[0066] <Electrolyte> Non-aqueous electrolytes generally contain electrolytes.

[0067] The electrolyte preferably contains at least one of a lithium salt containing fluorine (hereinafter sometimes referred to as "fluorinated lithium salt") and a lithium salt that does not contain fluorine.

[0068] Examples of fluorinated lithium salts include inorganic acid anionic salts and organic acid anionic salts. Examples of inorganic acid anionic salts include lithium hexafluoride phosphate (LiPF6), lithium borate tetrafluoride (LiBF4), lithium arsenate hexafluoride (LiAsF6), and lithium tantalate hexafluoride (LiTaF6). Examples of organic acid anionic salts include lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), and lithium bis(pentafluoroethanesulfonyl)imide (Li(C2F5SO2)2N). Among these, lithium hexafluoride phosphate (LiPF6) is even more preferred as the fluorinated lithium salt.

[0069] Lithium salts that do not contain fluorine include lithium perchlorate (LiClO4), lithium aluminate tetrachloride (LiAlCl4), and lithium decachlorodecaborate (Li2B 10 Cl 10 ) are some examples.

[0070] When the electrolyte contains a fluorinated lithium salt, the content of the fluorinated lithium salt is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of the electrolyte. When the fluorinated lithium salt contains lithium hexafluoride phosphate (LiPF6), the content of lithium hexafluoride phosphate (LiPF6) is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of the electrolyte.

[0071] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3 mol / L or less, more preferably 0.5 mol / L or more and 2 mol / L or less.

[0072] When the non-aqueous electrolyte contains lithium hexafluoride phosphate (LiPF6), the concentration of lithium hexafluoride phosphate (LiPF6) in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3 mol / L or less, more preferably 0.5 mol / L or more and 2 mol / L or less.

[0073] <Other ingredients> The non-aqueous electrolyte may contain other components as needed. Other components include acid anhydrides.

[0074] [Precursor for lithium secondary batteries] The lithium secondary battery precursor of this disclosure is The case and The positive electrode, negative electrode, separator, and electrolyte were repurposed for the case. It is equipped with. Here, The positive electrode is a positive electrode capable of intercalating and releasing lithium ions. The negative electrode is a negative electrode capable of intercalating and releasing lithium ions. The electrolyte is the non-aqueous electrolyte of this disclosure.

[0075] In this disclosure, a lithium secondary battery precursor refers to a lithium secondary battery before it has been charged and discharged.

[0076] The lithium secondary battery precursor of this disclosure can suppress the deficiency of battery capacity after high-temperature storage of the lithium secondary battery, and can also suppress the increase in battery resistance after high-temperature storage.

[0077] <Case> The shape of the case is not particularly limited and can be appropriately selected depending on the application of the lithium secondary battery precursor described herein. Examples of cases include cases containing laminate film, and cases consisting of a battery can and a battery can lid.

[0078] <Positive electrode> The positive electrode is a positive electrode capable of intercalating and releasing lithium ions. The positive electrode preferably includes at least one positive electrode active material capable of intercalating and releasing lithium ions.

[0079] The positive electrode preferably comprises a positive electrode current collector and a positive electrode composite layer provided on at least a portion of the surface of the positive electrode current collector.

[0080] Examples of materials for the positive electrode current collector include metal or alloy. More specifically, suitable materials for the positive electrode current collector include aluminum, nickel, stainless steel (SUS), and copper. Among these, aluminum is preferred from the viewpoint of balancing high conductivity with cost. Here, "aluminum" refers to pure aluminum or aluminum alloy. Aluminum foil is preferred as the positive electrode current collector. The material of the aluminum foil is not particularly limited, and examples include A1085 and A3003.

[0081] The positive electrode composite layer contains a positive electrode active material and a binder.

[0082] The positive electrode active material is not particularly limited as long as it is a material capable of intercalating and releasing lithium ions, and can be appropriately adjusted depending on the application of the lithium secondary battery precursor.

[0083] Examples of positive electrode active materials include primary oxides and secondary oxides. Primary oxides consist of lithium (Li) and nickel (Ni) as constituent metal elements. Secondary oxides contain Li, Ni, and at least one other metal element as constituent metal elements. Examples of metal elements other than Li and Ni include transition metal elements and typical metal elements. Preferably, the secondary oxide contains the metal element other than Li and Ni in an amount equivalent to or less than Ni in terms of atomic number. The metal element other than Li and Ni may be at least one selected from the group consisting of Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. These positive electrode active materials may be used individually or in combination.

[0084] The positive electrode active material preferably contains a lithium-containing composite oxide (hereinafter sometimes referred to as "NCM") represented by the following formula (P1). The lithium-containing composite oxide (P1) has the advantage of having a high energy density per unit volume and excellent thermal stability. LiRing a Co b Mn c O2… Formula (P1) In equation (P1), a, b, and c are each independently greater than 0 and less than 1, and the sum of a, b, and c is between 0.99 and 1.00. A specific example of NCM is LiNi 0.33 Co 0.33 Mn 0.33 O2, LiLiLi 0.5 Co 0.3 Mn 0.2 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 O2, LiLiLi 0.6 Co 0.2 Mn 0.2O2, LiLiLi 0.8 Co 0.1 Mn 0.1 Examples include O2.

[0085] The positive electrode active material may contain a lithium-containing composite oxide represented by the following formula (P2) (hereinafter sometimes referred to as "NCA"). Li t Ni 1-x-y Co x Al y O2… Formula (P2) In equation (P2), t is between 0.95 and 1.15, x is between 0 and 0.3, y is between 0.1 and 0.2, and the sum of x and y is less than 0.5. A specific example of NCA is Li Ni 0.8 Co 0.15 Al 0.05 Examples include O2.

[0086] In the lithium secondary battery precursor of this disclosure, when the positive electrode comprises a positive electrode current collector and a positive electrode composite layer containing a positive electrode active material and a binder, the content of the positive electrode active material in the positive electrode composite layer is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more, based on the total amount of the positive electrode composite layer. The content of the positive electrode active material in the positive electrode composite layer is preferably 99.9% by mass or less, more preferably 99% by mass or less, based on the total amount of the positive electrode composite layer.

[0087] Examples of binders include polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluororesins, and rubber particles. Examples of fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer. Examples of rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles. Among these, fluororesins are preferred from the viewpoint of improving the oxidation resistance of the positive electrode composite layer. One type of binder can be used alone, and two or more types can be used in combination as needed. The binder content in the positive electrode composite layer is preferably 0.1% by mass or more and 4% by mass or less relative to the total amount of the positive electrode composite layer, from the viewpoint of balancing the physical properties of the positive electrode composite layer (e.g., electrolyte permeability, peel strength, etc.) and battery performance. When the binder content is 0.1% by mass or more, the adhesion of the positive electrode composite layer to the positive electrode current collector and the bonding of the positive electrode active materials to each other are further improved. When the binder content is 4% by mass or less, the amount of positive electrode active material in the positive electrode composite layer can be increased, thus further improving the discharge capacity.

[0088] The positive electrode composite layer preferably contains a conductive additive. As the material for the conductive additive, known conductive additives can be used. Among the known conductive additives, conductive carbon materials are preferred. Examples of conductive carbon materials include graphite, carbon black, conductive carbon fibers, and fullerenes. These can be used alone or in combination of two or more types. Examples of conductive carbon fibers include carbon nanotubes, carbon nanofibers, and carbon fibers. Examples of graphite include artificial graphite and natural graphite. Examples of natural graphite include flake graphite, lump graphite, and earthy graphite. The material of the conductive additive may be a commercially available product. Examples of commercially available carbon blacks include Tokai Carbon #4300, #4400, #4500, #5500, etc. (Tokai Carbon Co., Ltd., Furnace Black), Printex L, etc. (Degussa Co., Ltd., Furnace Black), Raven 7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, etc., Conductex SC ULTRA, Conductex 975ULTRA, etc., PUER BLACK100, 115, 205 etc. (Columbian brand, Furnace Black), #2350, #2400B, #2600B, #30050B, #3030B, #3230B, #3350B, #3400B, #5400B etc. (Mitsubishi Chemical Corporation, Furnace Black), MONARCH1400, 1300, 900, VulcanXC-72R, BlackPearls2000, Examples include LITX-50, LITX-200 (Cabot Furnace Black), Ensaco 250G, Ensaco 260G, Ensaco 350G, Super-P (TIMCAL), Ketjenblack EC-300J, EC-600JD (Akzo), Denka Black, Denka Black HS-100, FX-35 (Denka Acetylene Black).

[0089] The positive electrode composite layer may contain other components. These other components include thickeners, surfactants, dispersants, wetting agents, and defoaming agents.

[0090] <Negative electrode> The negative electrode is a negative electrode capable of intercalating and releasing lithium ions. The negative electrode preferably includes at least one negative electrode active material capable of intercalating and releasing lithium ions.

[0091] The negative electrode preferably comprises a negative electrode current collector and a negative electrode composite material layer provided on at least a portion of the surface of the negative electrode current collector.

[0092] There are no particular restrictions on the material of the negative electrode current collector; any known material can be used, such as metal or alloy. Specifically, examples of materials for the negative electrode current collector include aluminum, nickel, stainless steel (SUS), nickel-plated steel, and copper. Among these, copper is preferred as the material for the negative electrode current collector from the viewpoint of processability. Copper foil is preferred as the negative electrode current collector.

[0093] The negative electrode composite layer contains a negative electrode active material and a binder.

[0094] The negative electrode active material is not particularly limited as long as it is a material capable of intercalating and releasing lithium ions. Preferably, the negative electrode active material is at least one selected from the group consisting of, for example, metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped and dedoped with lithium ions, transition metal nitrides that can be doped and dedoped with lithium ions, and carbon materials that can be doped and dedoped with lithium ions. Among these, the negative electrode active material is preferably a carbon material capable of doping and dedoping with lithium ions (hereinafter also simply referred to as "carbon material").

[0095] Examples of carbon materials include carbon black, activated carbon, graphite materials, and amorphous carbon materials. These carbon materials may be used individually or in mixtures of two or more. The form of the carbon material is not particularly limited and can be fibrous, spherical, potato-shaped, or flake-shaped. The particle size of the carbon material is not particularly limited, but is preferably 5 μm to 50 μm, and more preferably 20 μm to 30 μm. Examples of amorphous carbon materials include hard carbon, coke, mesocarbon microbeads (MCMB) fired at temperatures below 1500°C, and mesophase pitch carbon fiber (MCF). Examples of graphite materials include natural graphite and artificial graphite. Examples of artificial graphite include graphitized MCMB and graphitized MCF. Graphite materials may also contain boron. Graphite materials may be coated with metal or amorphous carbon. Examples of metals used to coat graphite materials include gold, platinum, silver, copper, and tin. Graphite materials may also be mixtures of amorphous carbon and graphite.

[0096] The negative electrode composite layer preferably contains a conductive additive. Examples of conductive additives include those similar to those exemplified as conductive additives that may be included in the positive electrode composite layer.

[0097] The negative electrode composite layer may contain other components in addition to the above-mentioned components. Examples of other components include thickeners, surfactants, dispersants, wetting agents, and defoaming agents.

[0098] <Separator> Examples of separators include porous resin plates. Materials for the porous resin plates include resin, nonwoven fabrics containing this resin, and others. Examples of resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, and polyamide. In particular, the separator is preferably a porous resin sheet with a single-layer or multi-layer structure. The porous resin sheet is mainly made of one or more types of polyolefin resin. The thickness of the separator is preferably 5 μm to 30 μm. The separator is preferably placed between the positive electrode and the negative electrode.

[0099] <Specific examples of lithium secondary battery precursors> Figure 1 is a schematic cross-sectional view showing a stacked lithium secondary battery precursor, which is an example of a lithium secondary battery precursor according to this disclosure.

[0100] As shown in Figure 1, lithium secondary battery precursor 1 is a stacked battery precursor. In detail, in the lithium secondary battery precursor 1, the battery element 10 is enclosed inside the outer casing 30. The outer casing 30 is made of laminate film. The battery element 10 is fitted with a positive electrode lead 21 and a negative electrode lead 22. 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 outer casing 30.

[0101] As shown in Figure 1, the battery element 10 is made up of a stack of a positive electrode 11, a separator 13, and a negative electrode 12. The positive electrode 11 has a positive electrode composite layer 11B formed on both main surfaces of the positive electrode current collector 11A. The negative electrode 12 has a negative electrode composite layer 12B formed on both main surfaces of the 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 via the separator 13.

[0102] The non-aqueous electrolyte of this disclosure is injected into the exterior casing 30 of the lithium secondary battery precursor 1. The non-aqueous electrolyte of this 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, a single 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 negative electrode may be formed with their respective active material layers on one side of their respective current collectors.

[0103] Although lithium secondary battery precursor 1 is a stacked lithium secondary battery precursor, the lithium secondary battery precursor of this disclosure is not limited to this, and may be, for example, a wound lithium secondary battery precursor. The wound lithium secondary battery precursor is formed by stacking a positive electrode, a separator, a negative electrode, and a separator in that order and winding them in layers. The wound lithium secondary battery precursor includes cylindrical lithium secondary battery precursors and prismatic lithium secondary battery precursors.

[0104] As shown in Figure 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 outer casing 30 are opposite to the outer casing 30, but the disclosure is not limited thereto. For example, the way in which the positive electrode lead and the negative electrode lead protrude from the inside to the outside of the outer casing 30 is the same direction with respect to the outer casing 30.

[0105] An example of the lithium secondary battery of this disclosure described later is a lithium secondary battery obtained by subjecting a lithium secondary battery precursor 1 to charging and discharging.

[0106] Figure 2 is a schematic cross-sectional view showing a coin-type lithium secondary battery precursor, which is another example of a lithium secondary battery precursor of the present disclosure.

[0107] In the coin-type lithium secondary battery precursor shown in Figure 2, a disc-shaped negative electrode 42, a separator 45 injected with a non-aqueous electrolyte, a disc-shaped positive electrode 41, and, if necessary, spacer plates 47 and 48 made of stainless steel or aluminum are stacked in this order and housed between the positive electrode can 43 (hereinafter also referred to as the "battery can") and the sealing plate 44 (hereinafter also referred to as the "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 non-aqueous electrolyte of this disclosure is used as the non-aqueous electrolyte injected into the separator 45.

[0108] An example of the lithium secondary battery of this disclosure, as described later, is a lithium secondary battery obtained by charging and discharging a coin-type lithium secondary battery precursor shown in Figure 2.

[0109] [Lithium secondary battery and method for manufacturing the same] The method for manufacturing a lithium secondary battery disclosed herein is: The process for preparing the lithium secondary battery precursor described above (hereinafter also referred to as the "preparation process"), The above lithium secondary battery precursor is subjected to a charging and discharging process, Includes. The lithium secondary battery of this disclosure is a lithium secondary battery obtained by subjecting the lithium secondary battery precursor of this disclosure described above to charging and discharging.

[0110] According to the lithium secondary battery and its manufacturing method disclosed herein, it is possible to suppress the deficiency of battery capacity after high-temperature storage of the lithium secondary battery, and to suppress the increase in battery resistance after high-temperature storage.

[0111] The preparation step may simply be a step of preparing a pre-manufactured lithium secondary battery precursor of the present disclosure for use in a charging and discharging step, or it may be a step of manufacturing the lithium secondary battery precursor of the present disclosure. The lithium secondary battery precursor is as described above.

[0112] In the charging and discharging process, the charging and discharging of the lithium secondary battery precursor can be carried out according to known methods. In this process, the lithium secondary battery precursor may undergo multiple charging and discharging cycles. As described above, this charging and discharging process preferably forms an SEI (Solid Electrolyte Interface) film on the surface of the positive electrode (especially the positive electrode active material) and / or the negative electrode (especially the negative electrode active material) of the lithium secondary battery precursor.

[0113] The charging and discharging process preferably involves performing a combination of charging and discharging one or more times on the lithium secondary battery precursor in an environment of 25°C to 70°C. [Examples]

[0114] The following are examples of the embodiments of this disclosure, but this disclosure is not limited to the following embodiments. In the following, "%" refers to "mass%" unless otherwise specified.

[0115] <Synthesis of compound (I-1) (methyltrifluoromethylsulfonyl acetate)> Compound (I-1) (methyltrifluoromethylsulfonyl acetate), a specific example of compound (I), was synthesized according to the reaction scheme below.

[0116] [ka]

[0117] The detailed procedure for this synthesis is as follows: A 200 mL four-necked flask connected to a nitrogen-purged Liebig condenser was charged with sodium trifluoromethanesulfonate (5.00 g, 32.0 mmol), methyl bromoacetate (4.90 g, 32.0 mmol), and dimethylacetamide (DMA) (20 mL) as a solvent, and the mixture was stirred and reacted at 80°C. After 3 hours, the reaction was stopped and the mixture was cooled to room temperature. The resulting reaction solution was then filtered to remove the salts, and the filtrate was concentrated under reduced pressure. The obtained crude product was separated and purified by flash column chromatography using a hexane / ethyl acetate solvent. The hexane / ethyl acetate solvent consists of hexane and ethyl acetate. This yielded compound (I-1) (methyltrifluoromethylsulfonyl acetate), a colorless, transparent oil (1.66 g, 8.05 mmol, yield 25%). Colorless and transparent oil 1 The measurement results by 1H-NMR (CDCl3) are shown below. 1 H-NMR: δ3.89(s,3H), 4.25(s,2H)

[0118] <Synthesis of compound (I-2) (ethyl trifluoromethylsulfonyl acetate)> Compound (I-2) (ethyl trifluoromethylsulfonyl acetate), a specific example of compound (I), was synthesized according to the reaction scheme below.

[0119] [ka]

[0120] The detailed procedure for this synthesis is as follows: A 200 mL four-necked flask connected to a nitrogen-purged Liebig condenser was charged with sodium trifluoromethanesulfonate (6.37 g, 40.8 mmol), sodium iodide (6.12 g, 40.8 mmol), ethyl chloroacetate (5.00 g, 40.8 mmol), and dimethylacetamide (20 mL) as a solvent. The mixture was stirred and reacted at 80°C. After 3 hours, the reaction was stopped and the mixture was cooled to room temperature. The resulting reaction solution was then filtered to remove the salts, and the filtrate was concentrated under reduced pressure. The obtained crude product was separated and purified by flash column chromatography using a hexane / ethyl acetate solvent. The hexane / ethyl acetate solvent consists of hexane and ethyl acetate. This yielded compound (I-2) (ethyl trifluoromethylsulfonyl acetate), a colorless, transparent oil (3.21 g, 14.6 mmol, yield 35%). Colorless and transparent oil 1 The measurement results by 1H-NMR (CDCl3) are shown below. 1 H-NMR: δ1.35(t,J=6.0Hz,3H), 4.23(s,2H), 4.34(q,J=6.0Hz,2H)

[0121] <Synthesis of compound (I-3) (n-butyltrifluoromethylsulfonyl acetate)> Compound (I-3) (n-butyltrifluoromethylsulfonyl acetate), a specific example of compound (I), was synthesized.

[0122] [ka]

[0123] For details, "Sodium trifluoromethanesulfonate (6.37g, 40.8mmol), sodium iodide (6.12g, 40.8mmol), ethyl chloroacetate (5.00g, 40.8mmol), and dimethylacetamide (20mL) as a solvent" "Sodium trifluoromethanesulfonate (5.18 g, 33.2 mmol), sodium iodide (4.98 g, 33.2 mmol), butyl chloroacetate (5.00 g, 33.2 mmol), and dimethylacetamide (20 mL) as a solvent." Compound (I-3) (n-butyltrifluoromethylsulfonyl acetate) was synthesized in the same manner as the synthesis of compound (I-2) described above, except for the change in the compound. This yielded compound (I-3) (n-butyltrifluoromethylsulfonyl acetate), a colorless, transparent oil (2.30 g, 9.27 mmol, yield 28%). Colorless and transparent oil 1 The measurement results by 1H-NMR (CDCl3) are shown below. 1 H-NMR: δ0.82(t,J=7.2Hz,3H), 1.38-1.45(m, 2H), 1.66-1.71(m,2H), 4.23(s,2H), 4.28(t,J=5.4Hz,2H)

[0124] <Synthesis of compound (I-4) (t-butyltrifluoromethylsulfonyl acetate)> Compound (I-4) (t-butyltrifluoromethylsulfonyl acetate), a specific example of compound (I), was synthesized.

[0125] [ka]

[0126] For details, "Sodium trifluoromethanesulfonate (5.00 g, 32.0 mmol), methyl bromoacetate (4.90 g, 32.0 mmol), and dimethylacetamide (20 mL) as a solvent" 「Sodium trifluoromethanesulfonate (5.00 g, 32.0 mmol), t-butyl bromoacetate (6.24 g, 32.0 mmol), and dimethylacetamide (20 mL) as a solvent」 Compound (I-4) (t-butyl trifluoromethylsulfonylacetate) was synthesized in the same manner as the synthesis of the aforementioned compound (I-1), except that it was changed to the above. Thereby, compound (I-4) (t-butyl trifluoromethylsulfonylacetate), which is a colorless transparent oil (2.02 g, 8.14 mmol, yield 25%), was obtained. Of the colorless transparent oil 1 The measurement results by 1H-NMR (CDCl3) are shown below. 1 1H-NMR: δ 1.52 (s, 9H), 4.14 (s, 2H)

[0127] 〔Example 1〕 <Preparation of non-aqueous electrolyte> Ethylene carbonate (hereinafter referred to as EC), dimethyl carbonate (hereinafter referred to as DMC), and ethyl methyl carbonate (EMC) were mixed at EC:DMC:EMC = 30:35:35 (volume ratio). Thereby, a mixed solvent was obtained as a non-aqueous solvent. To the obtained mixed solvent, LiPF6 as an electrolyte was dissolved so that the concentration in the finally obtained non-aqueous electrolyte became 1 mol / liter, and an electrolyte (hereinafter also referred to as "basic electrolyte") was obtained. To the obtained basic electrolyte, the above compound (I-1) as compound (I) was added so that the content with respect to the total amount of the finally obtained non-aqueous electrolyte became the content (mass%) described in Table 1, and a non-aqueous electrolyte was obtained.

[0128] <Fabrication of positive electrode> As a positive electrode active material, Li(Ni 0.5 Co 0.2 Mn 0.3A mixture was obtained by adding 94% by mass of O2, carbon black (3% by mass) as a conductive additive, and polyvinylidene fluoride (PVdF) (3% by mass) as a binder. The obtained mixture was dispersed in N-methylpyrrolidone solvent to obtain a cathode composite slurry. A 20 μm thick aluminum foil was prepared as the positive electrode current collector. The obtained positive electrode slurry was applied onto aluminum foil, dried, and then rolled in a press to obtain a sheet-like positive electrode. The positive electrode consists of a positive electrode current collector and a positive electrode active material layer.

[0129] <Fabrication of the negative electrode> A negative electrode slurry was obtained by mixing graphite (96% by mass) as the negative electrode active material, carbon black (1% by mass) as a conductive additive, 1% by mass of carboxymethylcellulose sodium dispersed in pure water as a thickener, and 2% by mass of styrene-butadiene rubber (SBR) dispersed in pure water as a binder. A 10 μm thick copper foil was prepared as the negative electrode current collector. The obtained negative electrode slurry was applied onto copper foil, dried, and then rolled in a press to obtain a sheet-like negative electrode. The negative electrode consists of a negative electrode current collector and a negative electrode active material layer.

[0130] <Preparing the separator> A porous polyethylene film was prepared as a separator.

[0131] <Preparation of lithium secondary battery precursors> The negative electrode was punched out in a disc shape with a diameter of 14 mm, the positive electrode in a disc shape with a diameter of 13 mm, and the separator in a disc shape with a diameter of 17 mm. This resulted in coin-shaped negative electrodes, coin-shaped positive electrodes, and coin-shaped separators. The obtained coin-shaped negative electrode, coin-shaped separator, and coin-shaped positive electrode were stacked in this order inside a stainless steel battery case (size: 2032). Next, 20 μL of non-aqueous electrolyte was poured into the battery case, immersing the separator, positive electrode, and negative electrode in the non-aqueous electrolyte. Next, an aluminum plate (1.2 mm thick, 16 mm in diameter) and a spring were placed on the positive electrode, and the battery was sealed by crimping the battery can lid via a polypropylene gasket. Based on the above, a coin-shaped lithium secondary battery precursor (i.e., a lithium secondary battery before charging and discharging) having the configuration shown in Figure 2 was obtained. The size of the lithium secondary battery precursor was 20 mm in diameter and 3.2 mm in height.

[0132] <Manufacturing of lithium secondary batteries> The lithium secondary battery precursor described above was subjected to the following processes in order: charging from 1.5V to 4.2V, holding for 5 to 50 hours, charging to 4.2V, and discharging to 2.5V, all within a temperature range of 25°C to 70°C, to obtain a lithium secondary battery.

[0133] <Evaluation of initial discharge capacity> The lithium secondary battery obtained above was charged to 4.2V in a constant temperature bath at 25°C, then discharged to 2.5V, and its discharge capacity [mAh] (hereinafter referred to as "initial discharge capacity") was measured.

[0134] <Evaluation of initial resistance> Next, the lithium secondary battery, after measuring its initial discharge capacity, was charged to 3.7V, then cooled to -10°C in a constant temperature bath. Based on the voltage drop (=voltage before discharge - voltage 10 seconds after discharge) and current values ​​(i.e., current values ​​corresponding to discharge rates 0.1C to 0.6C) for each discharge rate of 0.1C to 0.6C, the DC resistance [Ω] as the initial resistance value (-10°C) was measured.

[0135] <Evaluation of volume after high-temperature storage> Next, the lithium secondary batteries, after initial resistance measurement, were charged to 4.2V, and the charged lithium secondary batteries were stored in a constant temperature bath at 60°C for 14 days (hereinafter referred to as "high-temperature storage"). The discharge capacity [mAh] of a lithium secondary battery after high-temperature storage was determined by discharging it to 2.5V in a constant temperature bath at 25°C, then charging it to 4.2V, and finally discharging it again to 2.5V. The discharge capacity [mAh] at the final discharge was defined as the discharge capacity after high-temperature storage. Based on the above results, the discharge capacity of the lithium secondary battery in Example 1 after high-temperature storage was determined, with the discharge capacity of the lithium secondary battery in Comparative Example 1 after high-temperature storage set to 100, and this was defined as "Capacity after high-temperature storage (relative value)". The obtained "volume after high-temperature storage (relative value)" is shown in Table 1.

[0136] <Evaluation of resistance after high-temperature storage> Next, the resistance value of the lithium secondary battery after capacity measurement following high-temperature storage (-10°C) was measured using the same method as the initial resistance value (-10°C). Similarly, for Comparative Example 1 described later, the resistance value of the lithium secondary battery after capacity measurement following high-temperature storage (-10°C) was measured. Based on the above results, the resistance value (-10°C) of the lithium secondary battery in Example 1 after high-temperature storage and capacity measurement was set to 100 (relative value), and this was determined and referred to as "Resistance after high-temperature storage (relative value)". The obtained "resistance after high-temperature storage (relative value)" is shown in Table 1.

[0137] [Examples 2, 3, and 7] The same procedure as in Example 1 was followed, except that compound (I-1) added to the basic electrolyte was changed to compound (I-2), compound (I-3), or compound (I-4). The results are shown in Table 1.

[0138] [Examples 4-6] The procedure was the same as in Example 3, except that to a non-aqueous electrolyte containing compound (I-3), the following specific compound (II-1) (lithium difluorophosphate), which is a specific example of compound (II), the following specific compound (III-1), which is a specific example of compound (III), or the following specific compound (IV-1), which is a specific example of compound (IV), were added, such that the content of each compound relative to the total amount of the final non-aqueous electrolyte was as shown in Table 1. The results are shown in Table 1.

[0139] [ka]

[0140] [Examples 8-10] The procedure was the same as in Example 7, except that compound (II-1), compound (III-1), or compound (IV-1) was added to the non-aqueous electrolyte containing compound (I-4) in such a way that their respective content relative to the total volume of the final non-aqueous electrolyte was as shown in Table 1. The results are shown in Table 1.

[0141] [Comparative Example 1] The same procedure as in Example 1 was followed for the obtained basic electrolyte, except that compound (I-1) was not added. The results are shown in Table 1.

[0142] [Comparative Example 2] The procedure was the same as in Example 1, except that compound (I-1) added to the basic electrolyte was changed to the comparative compound (C1) described below. The results are shown in Table 1. The comparative compound (C1) is methyl methanesulfonyl acetate, as described in Japanese Patent Publication No. 2017-168347.

[0143] [ka]

[0144] [Table 1]

[0145] In Table 1, "-" indicates that the corresponding component is not present. "Content of each additive" shows the content (mass %) of the additive relative to the total amount of non-aqueous electrolyte for lithium secondary batteries.

[0146] As shown in Table 1, the lithium secondary batteries of Examples 1 to 10, which used a non-aqueous electrolyte containing compound (I) represented by formula (I), exhibited superior capacity after high-temperature storage and reduced resistance after high-temperature storage compared to the lithium secondary batteries of Comparative Examples 1 and 2. Here, the lithium secondary battery of Comparative Example 1 is a lithium secondary battery using a non-aqueous electrolyte that does not contain compound (I), and the lithium secondary battery of Comparative Example 2 is a lithium secondary battery using a non-aqueous electrolyte that contains comparative compound (C1) instead of compound (I). [Explanation of Symbols]

[0147] 1. Lithium secondary battery precursor 10 Battery elements 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 layers 21 Positive lead 22 Negative lead 30 Exterior 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 for lithium secondary batteries containing an additive for lithium secondary batteries comprising compound (I) represented by the following formula (I), The content of compound (I) is 0.01% by mass or more and 5.0% by mass or less, relative to the total amount of the non-aqueous electrolyte for lithium secondary batteries. Nonaqueous electrolyte for lithium secondary batteries. 【Chemistry 1】 [In formula (I), R １ This represents an alkyl group having 1 to 10 carbon atoms (at least one hydrogen atom of the alkyl group may be substituted with a halogen atom), an alkenyl group having 2 to 10 carbon atoms (at least one hydrogen atom of the alkenyl group may be substituted with a halogen atom), an alkynyl group having 2 to 10 carbon atoms (at least one hydrogen atom of the alkynyl group may be substituted with a halogen atom), an aryl group (at least one hydrogen atom of the aryl group may be substituted with a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms), or an aralkyl group (at least one hydrogen atom of the aromatic ring of the aralkyl group may be substituted with a halogen atom, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms).

2. The aforementioned R １ The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the alkyl group has 1 to 10 carbon atoms (at least one hydrogen atom of the alkyl group may be substituted with a halogen atom).

3. A non-aqueous electrolyte for a lithium secondary battery according to claim 1 or 2, further comprising at least one selected from the group consisting of compound (II), which is at least one of lithium monofluorophosphate and lithium difluorophosphate; compound (III), which is represented by the following formula (III); and compound (IV), which is represented by the following formula (IV). 【Chemistry 2】 [In formula (III), M is an alkali metal, Y is a transition element, a group 13, group 14, or group 15 element of the periodic table. b is an integer between 1 and 3. m is an integer between 1 and 4. n is an integer from 0 to 8. q is either 0 or 1, R ３１ This is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups may contain substituents or heteroatoms in their structure, and when q is 1 and m is 2 to 4, there are m R ３１ They may be joined together.) R ３２ This includes halogen atoms, C1-C10 alkyl groups, C1-C10 halogenated alkyl groups, C6-C20 aryl groups, or C6-C20 halogenated aryl groups (these groups may contain substituents or heteroatoms in their structure, and when n is 2-8, there are n R ３２ They may each be joined together to form a ring. Q １ and Q ２ Each of these is independently either an oxygen atom or a carbon atom. In formula (IV), R ４１ is an oxygen atom, an alkylene group having 1 to 6 carbon atoms, or an alkenylene group having 2 to 6 carbon atoms, R ４２ This is an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by formula (iv-1), or a group represented by formula (iv-2). * indicates the bonding position. In formula (iv-1), R ４３ This is an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group. In formula (iv-2), R ４４ This is an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms.

4. The case and The case contains a positive electrode, a negative electrode, a separator, and an electrolyte, Equipped with, The positive electrode is a positive electrode capable of intercalating and releasing lithium ions. The aforementioned negative electrode is a negative electrode capable of intercalating and releasing lithium ions. A lithium secondary battery precursor wherein the electrolyte is the non-aqueous electrolyte for lithium secondary batteries described in any one of claims 1 to 3.

5. The lithium secondary battery precursor according to claim 4, wherein the positive electrode contains a lithium-containing composite oxide represented by the following formula (P1) as the positive electrode active material. LiNi ａ Co ｂ Mn ｃ O ２ ... Formula (P1) [In formula (P1), a, b, and c are each independently greater than 0 and less than 1, and the sum of a, b, and c is 0.99 or greater and 1.00 or less.]

6. A step of preparing a lithium secondary battery precursor according to claim 4 or claim 5, The process involves charging and discharging the lithium secondary battery precursor. A method for manufacturing lithium secondary batteries, including [the specified component].

7. A lithium secondary battery obtained by charging and discharging a lithium secondary battery precursor according to claim 4 or claim 5.

Images