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

Abstract

Provided as one embodiment of the present invention is a non-aqueous electrolytic solution for a lithium secondary battery, the electrolytic solution making it possible to reduce the room-temperature resistance increase rate when a lithium secondary battery is stored at a high temperature. The non-aqueous electrolytic solution for a lithium secondary battery contains a compound (I) and an additive X which is at least one selected from the group consisting of: a compound (II), which is at least one of a monofluorophosphate salt and a difluorophosphate salt; a compound (III); a compound (IV); and a compound (V). R11 are, each independently, a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodine group (-I), and h represents an integer of 1 to 6.

Description

[Technical Field]

[0001] This disclosure relates to a non-aqueous electrolyte for lithium secondary batteries, a lithium secondary battery precursor, a method for manufacturing lithium secondary batteries, and lithium secondary batteries. [Background technology]

[0002] In recent years, various studies have been conducted regarding non-aqueous electrolytes for lithium-ion secondary batteries. For example, Patent Documents 1 and 2 disclose non-aqueous electrolytes for lithium secondary batteries containing bissulfonic acid ester compounds of a specific structure.

[0003] Patent Document 1: Specification of Chinese Patent Application Publication No. 113782834 Patent Document 2: Specification of Chinese Patent Application Publication No. 110668978 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, there are cases where it is necessary to further reduce the rate of increase in the room-temperature resistance of lithium secondary batteries when they are stored at high temperatures (hereinafter also referred to as "rate of increase in room-temperature resistance of lithium secondary batteries when stored at high temperatures"). An object of one aspect of this disclosure is to provide 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 that can reduce the rate of increase in resistance at room temperature when lithium secondary batteries are stored at high temperatures. [Means for solving the problem]

[0005] The means for solving the above problems include the following embodiments. <1> Compound (I) represented by the following formula (I), Additive X, which is at least one of monofluorophosphate and difluorophosphate, a compound (III) represented by the following formula (III), a compound (IV) represented by the following formula (IV), and a compound (V) represented by the following formula (V), A non-aqueous electrolyte for a lithium secondary battery containing the same.

[0006] [Chemical formula]

[0007] In formula (I), R 31 , 31 , 31 , , 41 , , , 31 , 31 , 31 , , Each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I). h represents an integer from 1 to 6. In formula (III), M 31+ Represents an alkali metal ion. X<9000003>Each independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I). Y 31 Represents a boron atom or a phosphorus atom. R 31 Each independently represents a single bond (-) or a divalent hydrocarbon group having 1 to 6 carbon atoms which may contain at least one group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodo group (-I) as a substituent. i is 1 or 2 when Y 31 is a boron atom, and represents an integer from 1 to 3 when Y 31 is a phosphorus atom. [[ID=F0000170]] j is 0 or 2 when Y 31 is a boron atom, and represents 0, 2, or 4 when Y 31 is a phosphorus atom. In formula (IV), R 41 Represents an oxa group (-O-) or a divalent hydrocarbon group having 1 to 6 carbon atoms. R 42 This represents a group represented by formula (iv-1), a group represented by formula (iv-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms. * indicates the bonding position. In formula (iv-1), R 43 This represents an oxymethylene group (-OCH2-), an oxyethylene group (-OCH2CH2-), an oxa group (-O-), or a divalent hydrocarbon group having 1 to 6 carbon atoms. In formula (iv-2), R 44 This represents a hydrocarbon group with 1 to 8 carbon atoms. In formula (V), R 51 Each of these independently represents a fluoro group (-F), a hydrocarbon group having 1 to 8 carbon atoms which may contain a fluoro group as a substituent, or a fluorine carbide group having 1 to 8 carbon atoms. k represents an integer between 0 and 2.

[0008] <2> The additive X contains at least one selected from the group consisting of compound (II) and compound (III). <1> Non-aqueous electrolyte for lithium secondary batteries as described above. <3> The additive X contains at least one selected from the group consisting of compound (II), compound (IV), and compound (V). <1> Non-aqueous electrolyte for lithium secondary batteries as described above. <4> The additive X contains compound (II) and at least one selected from the group consisting of compound (IV) and compound (V). <3> Non-aqueous electrolyte for lithium secondary batteries as described above. <5> The compound (IV) contains at least one selected from the group consisting of compound (IV-1) represented by the following formula (IV-1), compound (IV-2) represented by the following formula (IV-2), compound (IV-3) represented by the following formula (IV-3), compound (IV-5) represented by the following formula (IV-5), compound (IV-6) represented by the following formula (IV-6), compound (IV-7) represented by the following formula (IV-7), and compound (IV-8) represented by the following formula (IV-8). <3> Non-aqueous electrolyte for lithium secondary batteries as described above.

[0009] [ka]

[0010] <6> The additive X contains at least one selected from the group consisting of compound (IV-1), compound (IV-2), compound (IV-3), compound (IV-5), compound (IV-6), compound (IV-7), and compound (IV-8), and at least one selected from the group consisting of the difluorophosphate and compound (IV-4) represented by the following formula (IV-4). <5> Non-aqueous electrolyte for lithium secondary batteries as described above.

[0011] [ka]

[0012] <7> The compound (I) contains the following compound (I-1): <1> Non-aqueous electrolyte for lithium secondary batteries as described above.

[0013] [ka]

[0014] <8> 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. <1> ~ <7> A non-aqueous electrolyte for lithium secondary batteries as described in any one of the following. <9> The content of additive X 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 the battery. <1> ~ <8> A non-aqueous electrolyte for lithium secondary batteries as described in any one of the following. <10> 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, <1> ~ <9> A lithium secondary battery precursor, which is a non-aqueous electrolyte for lithium secondary batteries as described in any one of the following. <11> The positive electrode contains a lithium-containing composite oxide represented by the following formula (P1) as the positive electrode active material. <10> 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.] <12> <10> or <11> 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]. <13> <10> ~ <12> A lithium secondary battery obtained by charging and discharging a lithium secondary battery precursor described in any one of the above. [Effects of the Invention]

[0015] This disclosure provides a non-aqueous electrolyte for lithium secondary batteries, a lithium secondary battery precursor, a method for manufacturing a lithium secondary battery, and a lithium secondary battery, all of which can reduce the rate of resistance increase at room temperature during high-temperature storage of lithium secondary batteries. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic cross-sectional view showing a laminated battery, which is an example of a lithium secondary battery precursor according to this disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view showing a coin cell, which is another example of a lithium secondary battery precursor of the present disclosure. [Modes for carrying out the invention]

[0017] 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.

[0018] [Non-aqueous electrolyte for lithium secondary batteries] The non-aqueous electrolyte for lithium secondary batteries described herein (hereinafter also simply referred to as "non-aqueous electrolyte") is as follows: Compound (I) represented by the following formula (I), Additive X is at least one selected from the group consisting of compound (II), which is at least one of monofluorophosphate and difluorophosphate, compound (III), which is represented by the following formula (III), compound (IV), which is represented by the following formula (IV), and compound (V), which is represented by the following formula (V). It contains.

[0019] [ka]

[0020] In formula (I), R 11 Each of these independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodine group (-I). h represents an integer from 1 to 6. In formula (III), M 31+ This represents alkali metal ions, X 31 Each of these independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodine group (-I). Y 31 This represents a boron atom or a phosphorus atom, R 31 Each of these independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodo group (-I) as a single bond (-) or substituent. i is the same as Y 31 When it is a boron atom, 1 or 2, the Y 31 When it is a phosphorus atom, it represents an integer from 1 to 3. j is the same as Y 31 When it is a boron atom, it is 0 or 2, the Y 31 When it is a phosphorus atom, it represents 0, 2, or 4. In formula (IV), R 41 This represents an oxa group (-O-) or a divalent hydrocarbon group with 1 to 6 carbon atoms. R 42 This represents a group represented by formula (iv-1), a group represented by formula (iv-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms. * indicates the bonding position. In formula (iv-1), R 43 This represents an oxymethylene group (-OCH2-), an oxyethylene group (-OCH2CH2-), an oxa group (-O-), or a divalent hydrocarbon group having 1 to 6 carbon atoms. In formula (iv-2), R 44 This represents a hydrocarbon group with 1 to 8 carbon atoms. In formula (V), R 51 Each of these independently represents a fluoro group (-F), a hydrocarbon group having 1 to 8 carbon atoms which may contain a fluoro group as a substituent, or a fluorine carbide group having 1 to 8 carbon atoms. k represents an integer between 0 and 2.

[0021] The non-aqueous electrolyte of this disclosure can reduce the rate of resistance increase at room temperature when lithium secondary batteries are stored at high temperatures.

[0022] In this disclosure, room temperature resistance means resistance under room temperature conditions (for example, 25°C). In this disclosure, the rate of increase in room temperature resistance when a lithium secondary battery is stored at high temperatures means the rate of increase in the room temperature resistance of a lithium secondary battery when it is stored at high temperatures. In this disclosure, the rate of increase in room temperature resistance of a lithium secondary battery during high-temperature storage is determined as the ratio of the room temperature resistance of the lithium secondary battery after high-temperature storage to the room temperature resistance of the lithium secondary battery before high-temperature storage (i.e., the ratio [room temperature resistance of the lithium secondary battery after high-temperature storage / room temperature resistance of the lithium secondary battery before high-temperature storage]).

[0023] The above effects of the non-aqueous electrolyte of this disclosure are, Compound (I) and, Additive X is at least one selected from the group consisting of compound (II), which is at least one of monofluorophosphate and difluorophosphate, compound (III), which is represented by the following formula (III), compound (IV), which is represented by the following formula (IV), and compound (V), which is represented by the following formula (V). This effect is thought to be obtained through a combination of these factors. The reason for the above effects is thought to be that the combination of compound (I) and additive X efficiently forms a film on the electrodes (i.e., the positive electrode and / or negative electrode) in the lithium secondary battery, and this film suppresses side reactions such as the decomposition of the electrolyte or non-aqueous solvent in the non-aqueous electrolyte during charging and discharging.

[0024] <Compound (I)> The non-aqueous electrolyte of this disclosure contains compound (I) represented by the following formula (I). The non-aqueous electrolyte of this disclosure may contain only one compound (I) or two or more compounds.

[0025] [ka]

[0026] R 11H is preferably a halogen atom, specifically representing a "fluoro group (-F)", "chloro group (-Cl)", "bromo group (-Br)", or "iodine group (-I)" independently, and h represents an integer from 1 to 6.

[0027] R 11 It is particularly preferable that the group is a fluoro group (-F). h represents an integer from 1 to 6, but it is preferably 1, 2, or 3, more preferably 2 or 3, and particularly preferably 3.

[0028] Specific examples of compound (I) include the following compounds (I-1) and (I-2). Among these, the following compound (I-1) is preferred.

[0029] [ka]

[0030] When compound (I) in the non-aqueous electrolyte of this disclosure contains compound (I-1), the proportion of compound (I) in compound (I) is usually 50% by mass or more and 100% by mass or less, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0031] The content of compound (I) relative to the total amount of the non-aqueous electrolyte of this disclosure is usually 0.01% by mass or more and 5.0% by mass or less, preferably 0.05% by mass or more as the lower limit, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, preferably 4.0% by mass or less as the upper limit, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less. The lower limit can also be 0.8% by mass or more.

[0032] 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 collected from the lithium secondary battery, that non-aqueous electrolyte is included within the scope of non-aqueous electrolytes as defined in this disclosure. The same applies to the other compounds (additive X, etc.) described below.

[0033] <Additive X> The non-aqueous electrolyte of this disclosure contains additive X. Additive X is at least one selected from the group consisting of compound (II), which is at least one of a monofluorophosphate and a difluorophosphate; compound (III), which is represented by the following formula (III); compound (IV), which is represented by the following formula (IV); and compound (V), which is represented by the following formula (V).

[0034] The content of additive X relative to the total amount of the non-aqueous electrolyte of this disclosure is usually 0.01% by mass or more and 5.0% by mass or less, with a lower limit of preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, with an upper limit of preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less. The lower limit can also be 0.8% by mass or more.

[0035] From the viewpoint of achieving a more effective effect with the non-aqueous electrolyte of this disclosure, in the non-aqueous electrolyte of this disclosure, the mass ratio of the content of additive X to the content of compound (I) (hereinafter also referred to as "content mass ratio [additive X / compound (I)]") is usually 0.1 to 10, with a lower limit of preferably 0.2 or more, more preferably 0.5 or more, even more preferably 0.8 or more, and an upper limit of preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.

[0036] (Compound (II)) Compound (II) is at least one of a monofluorophosphate and a difluorophosphate. The cations of monofluorophosphates and difluorophosphates are lithium ions (Li + ), sodium ions (Na + ), potassium ions (K + It is preferable that it be lithium ion (Li + It is especially preferable that it be ) Specific examples of compound (II) include the following compounds (II-1) and (II-2). Compound (II-1) below is lithium difluorophosphate, and compound (II-2) is lithium monofluorophosphate.

[0037] [ka]

[0038] Compound (II) may be either a monofluorophosphate or a difluorophosphate, or both.

[0039] When the non-aqueous electrolyte of this disclosure contains compound (II), the content of compound (II) is usually 0.001% by mass or more and 5.0% by mass or less, with a lower limit of preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, with an upper limit of preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less. The lower limit can also be 0.8% by mass or more.

[0040] (Compound (III)) Compound (III) is a compound represented by the following formula (III).

[0041] [ka]

[0042] In formula (III), M 31+ This represents "alkali metal ions," X 31 Herein, halogen atoms are preferred, and specifically, each independently represents a "fluoro group (-F)", a "chloro group (-Cl)", a "bromo group (-Br)", or an "iodine group (-I)". Y 31 This represents a "boron atom" or a "phosphorus atom". R 31 Each of these independently represents either a "single bond (-)" or a "divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodo group (-I) as a substituent." i is the same as Y 31 When it is a boron atom, 1 or 2, the Y 31 When it is a phosphorus atom, it represents an integer from 1 to 3. j is the same as Y 31 When it is a boron atom, it is 0 or 2, the Y 31 When it is a phosphorus atom, it represents 0, 2, or 4. Note, R 31 It may also be a "single bond (-)", but R 31 For it to be a "single bond (-)", R 31 This means that two adjacent carbonyl groups (>C=O) are directly bonded, which in turn is the oxalate ion (C2O4). 2-This means that the group acts as a polydentate ligand to form an oxalate complex. Furthermore, "divalent hydrocarbon group" refers to a hydrocarbon group having 1 to 10 carbon atoms, and more particularly 1 to 6 carbon atoms, with two bonding positions. It is not limited to aliphatic hydrocarbon groups having a linear structure, but may also be a group having at least one structure selected from the group consisting of branched structures, cyclic structures, and carbon-carbon unsaturated bond structures (carbon-carbon double bond structures and carbon-carbon triple bond structures), and may also be an aromatic hydrocarbon group. In other words, alkylene groups, alkenylene groups, alkynylene groups, arylene groups, etc., are all included in "divalent hydrocarbon groups". Furthermore, the phrase "may include at least one group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodo group (-I) as a substituent" means that in addition to hydrocarbon groups that do not include a fluoro group (-F), etc. as a substituent, hydrocarbon groups in which some of the hydrogen atoms of the hydrocarbon group are substituted with one of the fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I) (specifically, halogenated alkylenes with 1 to 10 carbon atoms, etc.) are included, and the number and combination of fluoro groups (-F), chloro groups (-Cl), bromo groups (-Br), and iodo groups (-I) are not particularly limited.

[0043] R 31 When the hydrocarbon group is a "divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain at least one group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodo group (-I) as a substituent," the number of carbon atoms in the hydrocarbon group is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

[0044] M 31+ Lithium ions (Li + ), sodium ions (Na + ), potassium ions (K + It is preferable that it be lithium ion (Li + It is especially preferable that it be ) X 31The preferred group is a fluoro group (-F) or a chloro group (-Cl), with the fluoro group (-F) being particularly preferred. Y 31 represents a boron atom or a phosphorus atom, and i is Y 31 When it is a boron atom, it is 1 or 2, Y 31 When it is a phosphorus atom, it represents an integer from 1 to 3, and j is Y 31 When it is a boron atom, it is 0 or 2, Y 31 When it is a phosphorus atom, it represents 0, 2, or 4, but Y 31 When the atom is boron, the combinations of i and j are i=1 and j=2, and i=2 and j=0, and Y 31 When the atom is a phosphorus atom, the possible combinations of i and j are i=1 and j=4, i=2 and j=2, and i=3 and j=0. R 31 Preferably, the group is a single bond (-), an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, an alkylene group having 2 to 6 carbon atoms, an alkylene group having 1 to 6 carbon atoms containing a fluoro group (-F), an alkenylene group having 2 to 6 carbon atoms containing a fluoro group (-F), or an alkylene group having 2 to 6 carbon atoms containing a fluoro group (-F). Preferably, the group is a single bond (-), a methylene group (-CH2-), an ethylene group (-CH2CH2-), or an n-propylene group (-CH2CH2CH2-), and particularly preferably, it is a single bond (-).

[0045] Specific examples of compound (III) include compounds (III-1) to (III-4) listed below. Compound (III-1) is lithium bis(oxalato)borate (LiBOB), compound (III-2) is lithium difluorooxalatoborate (LiDFOB), compound (III-3) is lithium tetrafluorooxalatophosphate (LiTFOP), and compound (III-4) is lithium difluorobis(oxalato)phosphate (LiDFBOP).

[0046] [ka]

[0047] When the non-aqueous electrolyte of this disclosure contains compound (III), the content of compound (III) is usually 0.001% by mass or more and 5.0% by mass or less with respect to the total amount of the non-aqueous electrolyte, preferably 0.05% by mass or more as the lower limit, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, preferably 4.0% by mass or less as the upper limit, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less. The lower limit can also be 0.8% by mass or more.

[0048] (Compound (IV)) Compound (IV) is a compound represented by the following formula (IV).

[0049] [ka]

[0050] In formula (IV), R 41 This represents an "oxa group (-O-)" or a "divalent hydrocarbon group with 1 to 6 carbon atoms," R 42 This represents "a group represented by formula (iv-1)", "a group represented by formula (iv-2)", or "a divalent hydrocarbon group having 1 to 6 carbon atoms". * indicates the bonding position. In formula (iv-1), R 43 This represents an "oxymethylene group (-OCH2-)", an "oxyethylene group (-OCH2CH2-)", an "oxa group (-O-)", or a "divalent hydrocarbon group with 1 to 6 carbon atoms". In formula (iv-2), R 44 This represents a hydrocarbon group with 1 to 8 carbon atoms. Note, R 41 The term "oxa group (-O-)" means that the oxa group (-O-) is combined with a sulfonyl group (>S(=O)2) and R 42 Each of them is bonded to a cyclic sulfate ester (...S(=O)2-OR 42This means that -O…) is formed. Also, in formulas (iv-1) and (iv-2), * represents the "bonding position," which means that at the * part, the oxygen atom of formula (IV) and R 41 They are then combined into, for example, R 41 R is an "oxa group (-O-)" 42 If it is a "group represented by formula (iv-1)" or a "group represented by formula (iv-2)", it means that it forms a five-membered ring of ethylene sulfate (...S(=O)2-O-CH2-CHR-O...). Also, the definition of a "divalent hydrocarbon group" is the same as above. Also, R 43 The term "oxymethylene group (-OCH2-)" means that the oxa group (-O-) of the oxymethylene group is bonded to a sulfonyl group (>S(=O)2) to form a five-membered ring of ethylene sulfate (...S(=O)2-O-CH2-CHR-O...), 43 The statement that it is an "oxyethylene group (-OCH2CH2-)" means that it forms a six-membered ring of propylene sulfate (...S(=O)2-O-CH2-CH2-CHR-O...), 43 The statement that it is an "oxa group (-O-)" means that it forms a four-membered ring of methylene sulfate (...S(=O)2-O-CHR-O...).

[0051] R 41 When the hydrocarbon group is a "divalent hydrocarbon group having 1 to 6 carbon atoms," the number of carbon atoms in the hydrocarbon group is preferably 5 or less, more preferably 4 or less. R 42 When the hydrocarbon group is a "divalent hydrocarbon group having 1 to 6 carbon atoms," the number of carbon atoms in the hydrocarbon group is preferably 5 or less, more preferably 4 or less. R 43 When the hydrocarbon group is a "divalent hydrocarbon group having 1 to 6 carbon atoms," the number of carbon atoms in the hydrocarbon group is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less. R 44 This refers to a "hydrocarbon group having 1 to 8 carbon atoms," but the number of carbon atoms in the hydrocarbon group is preferably 6 or less, more preferably 5 or less, even more preferably 4 or less, and particularly preferably 3 or less.

[0052] R 41 Preferably, the group is an oxy group (-O-), an alkylene group having 1 to 6 carbon atoms, or an alkenylene group having 2 to 6 carbon atoms. More preferably, it is an oxy group (-O-), a methylene group (-CH2-), an ethylene group (-CH2CH2-), or an ethenylene group (-CH=CH-). Particularly preferably, it is an oxy group (-O-) or an ethenylene group (-CH=CH-). R 42 Preferably, the group is represented by formula (iv-1), the group represented by formula (iv-2), an alkylene group having 1 to 6 carbon atoms, or an alkenylene group having 2 to 6 carbon atoms. More preferably, the group is represented by formula (iv-1), the group represented by formula (iv-2), a methylene group (-CH2-), an ethylene group (-CH2CH2-), an ethenylene group (-CH=CH-), or an n-propylene group (-CH2CH2CH2-). Particularly preferred is the group represented by formula (iv-1) or a methylene group (-CH2-). R 43 Preferably, the group is an oxymethylene group (-OCH2-), an oxyethylene group (-OCH2CH2-), an oxa group (-O-), an alkylene group having 1 to 6 carbon atoms, or an alkenylene group having 1 to 6 carbon atoms. More preferably, the group is an oxymethylene group (-OCH2-), an oxyethylene group (-OCH2CH2-), an oxa group (-O-), a methylene group (-CH2-), an ethylene group (-CH2CH2-), or an n-propylene group (-CH2CH2CH2-), and particularly preferably, an oxymethylene group (-OCH2-). R 44 Preferably, the group is an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 2 to 8 carbon atoms, or an aryl group having 6 to 8 carbon atoms. More preferably, it is a methyl group (-CH3), an ethyl group (-CH2CH3), a vinyl group (-CH=CH2), an n-propyl group (-CH2CH2CH3), an n-butyl group (-CH2CH2CH2CH3), or a phenyl group (-C6H5). Particularly preferred are a methyl group (-CH3), an ethyl group (-CH2CH3), a vinyl group (-CH=CH2), or an n-propyl group (-CH2CH2CH3).

[0053] Specific examples of compound (IV) include compounds (IV-1) to (IV-8) listed below, but compounds (IV-1), (IV-2), (IV-3), (IV-5), (IV-6), (IV-7), and (IV-8) are preferred. Compound (IV-4) is particularly preferred to be used in combination with at least one compound selected from the group consisting of compounds (IV-1), (IV-2), (IV-3), (IV-5), (IV-6), (IV-7), and (IV-8).

[0054] [ka]

[0055] When the non-aqueous electrolyte of this disclosure contains compound (IV), the content of compound (IV) is usually 0.001% by mass or more and 5.0% by mass or less, with a lower limit of preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, with an upper limit of preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less. The lower limit can also be 0.8% by mass or more.

[0056] (Compound (V)) Compound (V) is a compound represented by the following formula (V).

[0057] [ka]

[0058] In formula (V), R 51 These terms independently represent "fluoro group (-F)", "carbon hydrocarbon group having 1 to 8 carbon atoms that may contain a fluoro group as a substituent", or "fluorine carbide group having 1 to 8 carbon atoms". k represents an integer between 0 and 2. In the formula (V), the connecting line of (R 51 ) k has a structure that pierces into the five-membered ring of vinylene carbonate. This means that the two hydrogen atoms contained in the five-membered ring of vinylene carbonate (…C(=O)-O-CH=CH-O…) can each independently be substituted with a "fluoro group (-F)", a "hydrocarbon group having 1 to 8 carbon atoms which may contain a fluoro group (-F) as a substituent", or a "fluorocarbon group having 1 to 8 carbon atoms". Also, the "hydrocarbon group having 1 to 8 carbon atoms which may contain a fluoro group as a substituent" is the same as described above. Further, the "fluorocarbon group" means a group in which all hydrogen atoms of the hydrocarbon group are substituted with fluoro groups (-F).

[0059] When R 51 is a "hydrocarbon group having 1 to 8 carbon atoms which may contain a fluoro group (-F) as a substituent" or a "fluorocarbon group having 1 to 8 carbon atoms", the number of carbon atoms of the hydrocarbon group and the fluorocarbon group is preferably 6 or less, more preferably 5 or less, still more preferably 4 or less, and particularly preferably 3 or less.

[0060] R 51 is preferably a fluoro group (-F), an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 2 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms containing a fluoro group (-F), an alkenyl group having 2 to 8 carbon atoms containing a fluoro group (-F), an alkynyl group having 2 to 8 carbon atoms containing a fluoro group (-F), an aryl group having 6 to 8 carbon atoms containing a fluoro group (-F), a perfluoroalkyl group having 1 to 8 carbon atoms, a perfluoroalkenyl group having 2 to 8 carbon atoms, a perfluoroalkynyl group having 2 to 8 carbon atoms, or a perfluoroaryl group having 6 to 8 carbon atoms, and particularly preferably a fluoro group (-F), a monofluoromethyl group (-CH2F), a difluoromethyl group (-CHF2), a trifluoromethyl group (-CF3), a methyl group (-CH3), or an ethyl group (-CH2CH3). k is an integer between 0 and 2, but 0 and 1 are preferred, and 0 is particularly preferred. Note that k being 0 means that R 51 This means that it does not exist, and therefore it becomes vinylene carbonate.

[0061] A specific example of compound (V) is compound (V-1) shown below. Compound (V-1) is vinylene carbonate.

[0062] [ka]

[0063] When the non-aqueous electrolyte of this disclosure contains compound (V), the content of compound (V) is usually 0.001% by mass or more and 5.0% by mass or less, with a lower limit of preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, with an upper limit of preferably 4.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 2.0% by mass or less, and particularly preferably 1.5% by mass or less. The lower limit can also be 0.8% by mass or more.

[0064] Additive X is at least one selected from the group consisting of compound (II), which is at least one of a monofluorophosphate and a difluorophosphate; compound (III), which is represented by the following formula (III); compound (IV), which is represented by the following formula (IV); and compound (V), which is represented by the following formula (V). However, in the non-aqueous electrolyte of this disclosure, it is preferable to contain two or more types of additive X, and it is also preferable to contain three or more types. Preferred forms of additive X include one or more selected from the group consisting of compound (II) and compound (III), one or more selected from the group consisting of compound (II), compound (IV), and compound (V), and one or more selected from the group consisting of compound (II) and compound (IV) and compound (V). Furthermore, preferred forms of additive X include one or more selected from the group consisting of compound (IV-1), compound (IV-2), compound (IV-3), compound (IV-5), compound (IV-6), compound (IV-7), and compound (IV-8), and one or more selected from the group consisting of difluorophosphate and compound (IV-4) represented by formula (IV-4). In particular, when additive X contains two or more types, a combination of compound (II) and compound (IV) is preferred, and a combination of lithium difluorophosphate and compound (IV-1) is especially preferred. When additive X contains three or more types, preferred combinations of additive X are compound (II), compound (IV), and compound (V), compound (II), compound (IV-1), and compound (IV-4), and particularly preferred combinations of lithium difluorophosphate, compound (IV-1), and compound (VI), and lithium difluorophosphate, compound (IV-1), and compound (IV-4).

[0065] <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.

[0066] 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.

[0067] The non-aqueous solvent preferably contains at least one carbonate compound 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.

[0068] The non-aqueous solvent preferably contains at least one carbonate compound 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.

[0069] 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.

[0070] 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.

[0071] <Electrolytes> Non-aqueous electrolytes generally contain electrolytes.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] [Precursor for lithium secondary batteries] The lithium secondary battery precursor of this disclosure is The case and The case contains the positive electrode, negative electrode, separator, and electrolyte, 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 the present disclosure (i.e., the non-aqueous electrolyte according to the first or second embodiment described above; the same applies hereinafter).

[0079] In this disclosure, a lithium secondary battery precursor refers to a lithium secondary battery before it has been charged and discharged.

[0080] According to the lithium secondary battery precursor of this disclosure, the rate of increase in resistance at room temperature during high-temperature storage can be reduced in a lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor.

[0081] <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.

[0082] <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.

[0083] 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.

[0084] 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.

[0085] The positive electrode composite layer preferably contains a positive electrode active material and a binder.

[0086] 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.

[0087] Examples of the positive electrode active material include, for example, a first oxide, a second oxide, etc. The first oxide has lithium (Li) and nickel (Ni) as constituent metal elements. The second oxide contains Li, Ni, and at least one metal element other than Li and Ni as constituent metal elements. Examples of the metal element other than Li and Ni include, for example, a transition metal element, a typical metal element, etc. The second oxide preferably contains the metal element other than Li and Ni at a ratio preferably comparable to or less than Ni in terms of atomic number conversion. The metal element other than Li and Ni may be, for example, at least one selected from the group consisting of Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. These positive electrode active materials may be used alone or in combination of plural.

[0088] The positive electrode active material preferably contains a lithium-containing composite oxide represented by the following formula (P1) (hereinafter, may be referred to as "NCM"). The lithium-containing composite oxide (P1) has the advantages of high energy density per unit volume and excellent thermal stability. LiNi a Co b Mn c O2… 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 more and 1.00 or less. Specific examples of NCM include LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.

[0089] 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.

[0090] In the lithium secondary battery precursor of the present disclosure, if 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 and 99.9% by mass or less, more preferably 30% by mass or more and 99.9% by mass or less, even more preferably 50% by mass or more and 99% by mass or less, and particularly preferably 70% by mass or more and 99% by mass or less, based on the total amount of the positive electrode composite layer.

[0091] 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.

[0092] 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, BlackPearls2 Examples include 000, LITX-50, LITX-200 (Cabot Furnace Black), Ensaco 250G, Ensaco 260G, Ensaco 350G, Super-P (TIMCAL), Ketjenblack EC-300J, EC-600JD (Akzo), Denka Black HS-100, FX-35 (Denka Acetylene Black).

[0093] The positive electrode composite layer may contain other components. These other components include thickeners, surfactants, dispersants, wetting agents, and defoaming agents.

[0094] <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.

[0095] 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.

[0096] 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.

[0097] The negative electrode composite layer preferably contains a negative electrode active material and a binder.

[0098] 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").

[0099] 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.

[0100] 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.

[0101] 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.

[0102] <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.

[0103] <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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] [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.

[0114] According to the lithium secondary battery and its manufacturing method disclosed herein, the rate of increase in resistance at room temperature during high-temperature storage of the lithium secondary battery can be reduced.

[0115] 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.

[0116] 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.

[0117] 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]

[0118] 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.

[0119] [Comparative 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 (hereinafter referred to as "EMC") were mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This yielded a mixed solvent as a non-aqueous solvent. To the resulting mixed solvent, LiPF6 was dissolved as an electrolyte so that the concentration in the final non-aqueous electrolyte solution was 1 mole / liter, thereby obtaining the electrolyte solution (hereinafter also referred to as the "basic electrolyte solution").

[0120] <Fabrication of the positive electrode> LiNi as a positive electrode active material 0.5 Co 0.2 Mn 0.3 A mixture was obtained by mixing O2 (94% by mass), carbon black (3% by mass) as a conductive additive, and polyvinylidene fluoride (PVdF) (3% by mass) as a binder. The obtained mixture was dispersed in N-methylpyrrolidone solvent to obtain a 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.

[0121] <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.

[0122] <Preparing the separator> A porous polyethylene film was prepared as a separator.

[0123] <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, 28 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.

[0124] <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 the lithium secondary battery of Comparative Example 1.

[0125] <Measurement of initial room-temperature resistance> The lithium secondary battery obtained in Comparative Example 1 was charged to 3.7V, and then, in a constant temperature bath at a temperature of 25°C, the voltage drop (= voltage before discharge - voltage 10 seconds after discharge) due to CC10s discharge at each discharge rate from 0.1C to 0.6C was measured. Here, CC10s discharge means discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and each current value (i.e., each current value corresponding to the discharge rates from 0.1C to 0.6C), the initial DC resistance [Ω] as the resistance at room temperature was determined.

[0126] <Measurement of initial low-temperature resistance> After initial room-temperature resistance measurement, lithium secondary batteries were charged to 3.7V. Then, in a constant-temperature chamber at -10°C, the voltage drop (=voltage before discharge - voltage 10 seconds after discharge) was measured for each discharge rate from 0.1C to 0.6C during a CC10s discharge. Here, CC10s discharge refers to discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and current values ​​(i.e., current values ​​corresponding to discharge rates from 0.1C to 0.6C), the initial room-temperature DC resistance [Ω] was determined.

[0127] <High temperature storage> Next, the lithium secondary batteries, after the initial low-temperature 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").

[0128] <Measurement of resistance at room temperature after high-temperature storage> The lithium secondary batteries, after being stored at high temperatures, were discharged to 2.5V, and then their resistance at room temperature after high-temperature storage was measured using the same method as the initial resistance measurement at room temperature.

[0129] <Measurement of low-temperature resistance after high-temperature storage> The lithium secondary batteries whose room-temperature resistance was measured after high-temperature storage were discharged to 2.5V, and then the room-temperature resistance after high-temperature storage was measured again using the same method as the initial room-temperature resistance measurement.

[0130] [Comparative Examples 2 and 3, Examples 1-5] To the basic electrolyte solution used in the lithium secondary battery of Comparative Example 1, compounds corresponding to specific examples of compound (I), compound (II), compound (III), compound (IV), and compound (V) were added as additives, such that their content relative to the total amount of the final non-aqueous electrolyte solution was as shown in Table 1. This yielded the non-aqueous electrolyte solutions used in the lithium secondary batteries of Comparative Examples 2 and 3, and the lithium secondary batteries of Examples 1 to 5. The lithium secondary batteries of Comparative Examples 2 and 3 and Examples 1 to 5 were prepared by performing the same procedure as in Comparative Example 1, and the initial room temperature resistance and initial low temperature resistance were measured, respectively, by performing the same procedure as in Comparative Example 1. Furthermore, high-temperature storage was performed by performing the same procedure as in Comparative Example 1, and the room temperature resistance after high-temperature storage and the low temperature resistance after high-temperature storage were measured, respectively. In Table 1, "-" means that the corresponding component is not contained. Furthermore, specific examples of compounds (I), (II), (III), (IV), and (V) are the following compounds (I-1), (I-2), (II-1), (III-1), (IV-1), (IV-4), and (V-1).

[0131] [ka] JPEG0007846771000016.jpg2319 JPEG0007846771000017.jpg2542 JPEG0007846771000018.jpg3442 JPEG0007846771000019.jpg2414

[0132] The relative values ​​of the lithium secondary batteries of Comparative Examples 2 and 3, and the lithium secondary batteries of Examples 1 to 5, were calculated, with the room temperature resistance and low temperature resistance after high-temperature storage of Comparative Example 1 set to 100. The results are shown in Table 1.

[0133] [Table 1]

[0134] [Examples 6-9] Similar to Examples 1-5, the compounds corresponding to specific examples of Compound (I), Compound (II), Compound (III), Compound (IV), and Compound (V) mentioned above were added as additives in such a way that their content relative to the total amount of the final non-aqueous electrolyte was as shown in Table 2, thereby obtaining the non-aqueous electrolytes to be used in the lithium secondary batteries of Examples 6-9. The lithium secondary batteries of Examples 6-9 were then prepared by performing the same procedure as in Comparative Example 1, and the "initial room temperature resistance measurement" and "initial low temperature resistance measurement" were performed by performing the same procedure as in Comparative Example 1. Furthermore, high-temperature storage was performed by performing the same procedure as in Comparative Example 1, and the "room temperature resistance measurement after high-temperature storage" and "low temperature resistance measurement after high-temperature storage" were performed, respectively. Compound (IV-8), which is a specific example of Compound (IV), is as follows.

[0135] [ka]

[0136] <Calculation of the rate of increase in resistance at room temperature and the rate of increase in resistance at low temperature during high-temperature storage> Using the initial room temperature resistance values, room temperature resistance values ​​after high-temperature storage, initial low-temperature resistance values, and low-temperature resistance values ​​after high-temperature storage for the lithium secondary batteries of Comparative Examples 1-3 and Examples 1-9, the percentage increase in room temperature resistance during high-temperature storage and the percentage increase in low-temperature resistance during high-temperature storage were calculated using the following formulas. Then, the relative values ​​of the percentage increase in room temperature resistance during high-temperature storage and the percentage increase in low-temperature resistance during high-temperature storage for the lithium secondary batteries of Comparative Examples 2 and 3 and Examples 1-9 were calculated, with the percentage increase in room temperature resistance during high-temperature storage and the percentage increase in low-temperature resistance during high-temperature storage for the lithium secondary battery of Comparative Example 1 set to 100. The results are shown in Table 2. Increase in resistance at room temperature during high-temperature storage (%) = (Resistance at room temperature after high-temperature storage / Initial resistance at room temperature) × 100 The percentage increase in low-temperature resistance during high-temperature storage (%) = (low-temperature resistance value after high-temperature storage / initial low-temperature resistance value) × 100

[0137] [Table 2]

[0138] <Measurement of initial capacity> For each of the lithium secondary batteries in Comparative Example 1, Example 3, Example 6, Example 7, Example 8, and Example 9, an aging procedure was performed in a constant temperature bath at 25°C, involving two charge-discharge cycles between 2.5V and 4.2V. After aging, the initial capacity of the lithium secondary batteries was measured by 4.2V CC-CV charging at a charge rate of 0.2C and 2.5V CC discharge at a discharge rate of 0.2C. "CC-CV charging" means constant current - constant voltage. "CC discharge" means discharging at a constant current.

[0139] <Measurement of initial room-temperature resistance> After initial capacity measurement, each lithium secondary battery was charged to 3.7V, and then, in a constant temperature chamber at 25°C, the voltage drop (=voltage before discharge - voltage 10 seconds after discharge) was measured for each discharge rate from 0.1C to 0.6C during a CC10s discharge. Here, CC10s discharge means discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and current values ​​(i.e., current values ​​corresponding to discharge rates from 0.1C to 0.6C), the initial DC resistance [Ω] as the resistance at room temperature was determined.

[0140] <Measurement of initial low-temperature resistance> After initial room-temperature resistance measurements, each lithium secondary battery was charged to 3.7V. Then, in a constant-temperature chamber at -10°C, the voltage drop (=voltage before discharge - voltage 10 seconds after discharge) was measured for each discharge rate from 0.1C to 0.6C during a CC10s discharge. Here, CC10s discharge refers to discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and current values ​​(i.e., current values ​​corresponding to discharge rates from 0.1C to 0.6C), the initial room-temperature DC resistance [Ω] was determined.

[0141] <Operation of high-temperature cycles> Next, each lithium secondary battery, after the initial low-temperature resistance measurement, was subjected to 200 cycles of charging at 55°C with a charge rate of 1C to 4.2V using a constant current and low voltage, followed by discharging at a discharge rate of 1C to 2.5V using a constant current. (Hereinafter referred to as the "high-temperature cycle")

[0142] <Measurement of capacity after high-temperature cycling> For each lithium secondary battery after high-temperature cycling, a constant current-constant voltage (Constant Current - Constant Voltage) charge was performed at a charge rate of 0.2C and a constant current (Constant Current) discharge at a discharge rate of 0.2C and a constant current (Constant Current) discharge at 2.5V was performed, and the capacity after high-temperature cycling was measured. Then, relative values ​​of the lithium secondary batteries of Examples 3, 6, 7, 8, and 9 after high-temperature cycling were calculated, with the capacity of the lithium secondary battery of Comparative Example 1 after high-temperature cycling set to 100. The results are shown in Table 3.

[0143] <Measurement of room-temperature resistance after high-temperature cycling> For each lithium secondary battery whose capacity after high-temperature cycling was measured, it was charged to 3.7V, and then, in a constant-temperature bath at a temperature of 25°C, the voltage drop (= voltage before discharge - voltage 10 seconds after discharge) due to CC10s discharge at discharge rates of 0.1C to 0.6C was measured. Here, CC10s discharge means discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and current values ​​(i.e., current values ​​corresponding to discharge rates of 0.1C to 0.6C), the DC resistance [Ω] as room-temperature resistance after high-temperature cycling was determined.

[0144] <Measurement of low-temperature resistance after high-temperature cycling> For each lithium secondary battery whose room-temperature resistance after high-temperature cycling was measured, it was charged to 3.7V, and then, in a constant-temperature bath at a temperature of 25°C, the voltage drop (= voltage before discharge - voltage 10 seconds after discharge) due to CC10s discharge at discharge rates of 0.1C to 0.6C was measured. Here, CC10s discharge means discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and current values ​​(i.e., current values ​​corresponding to discharge rates of 0.1C to 0.6C), the DC resistance [Ω] as the low-temperature resistance after high-temperature cycling was determined.

[0145] <Calculation of resistance increase rates at room temperature and low temperature during high-temperature cycling> Using the initial room temperature resistance, room temperature resistance after high-temperature cycling, initial low-temperature resistance, and low-temperature resistance after high-temperature cycling values ​​for each lithium secondary battery of Comparative Example 1, Example 3, Example 6, Example 7, Example 8, and Example 9, the percentage increase in room temperature resistance during high-temperature cycling and the percentage increase in low-temperature resistance during high-temperature cycling were calculated using the following formulas. Then, the relative values ​​of the percentage increase in room temperature resistance during high-temperature storage and the percentage increase in low-temperature resistance during high-temperature storage for each lithium secondary battery of Examples 3, 6, 7, 8, and Example 9 were calculated, with the percentage increase in room temperature resistance during high-temperature cycling and the percentage increase in low-temperature resistance during high-temperature cycling of the lithium secondary battery of Comparative Example 1 set to 100. The results are shown in Table 3. Increase in room temperature resistance during high-temperature cycling (%) = (Room temperature resistance after high-temperature cycling / Initial room temperature resistance) × 100 Rate of increase in low-temperature resistance during high-temperature cycling (%) = (low-temperature resistance after high-temperature cycling / initial low-temperature resistance) × 100

[0146] <Calculation of capacity retention rate during high-temperature cycling> Using the initial capacity and capacity after high-temperature cycling for each lithium secondary battery of Comparative Example 1, Example 3, Example 6, Example 7, Example 8, and Example 9, the capacity retention rate (%) during high-temperature cycling was calculated using the following formula. The results are shown in Table 3. Capacity retention rate during high-temperature cycling (%) = (Capacity after high-temperature cycling / Initial capacity) × 100

[0147] [Table 3]

[0148] As shown in Tables 1 to 3, the lithium secondary batteries of Examples 1 to 9, which use a non-aqueous electrolyte containing a combination of compound (I) and additive X, are clearly superior to the lithium secondary battery of Comparative Example 1 in terms of lower room temperature resistance after high-temperature storage and low-temperature resistance after high-temperature storage, as well as superior room temperature resistance increase rate during high-temperature storage, low-temperature resistance increase rate during high-temperature cycling, room temperature resistance increase rate during high-temperature cycling, low-temperature resistance increase rate during high-temperature cycling, capacity after high-temperature cycling, and capacity retention rate during high-temperature cycling.

[0149] 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 plates

[0150] The disclosure of Japanese Patent Application No. 2022-128895 filed on August 12, 2022 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference.

Claims

1. Compound (I) represented by the following formula (I), Additive X is at least one selected from the group consisting of compound (II) which is at least one of monofluorophosphate and difluorophosphate, compound (III) represented by the following formula (III), compound (IV) represented by the following formula (IV), and compound (V) represented by the following formula (V), A non-aqueous electrolyte for lithium secondary batteries containing the following: 【Chemistry 1】 [In formula (I), R １１ Each of these independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodine group (-I). h represents an integer between 1 and 6. In formula (III), M ３１＋ This represents alkali metal ions, X ３１ Each of these independently represents a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodine group (-I). Y ３１ This represents a boron atom or a phosphorus atom, R ３１ Each of these independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond (-) or at least one group selected from the group consisting of a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I) as a substituent. i is the Y ３１ When it is a boron atom, 1 or 2, the Y ３１ When it is a phosphorus atom, it represents an integer from 1 to 3. j is the above Y ３１ is 0 or 2 when the above Y ３１ is a phosphorus atom, and represents 0, 2, or 4. In formula (IV), R ４１ This represents an oxa group (-O-) or a divalent hydrocarbon group having 1 to 6 carbon atoms. R ４２ This represents a group represented by formula (iv-1), a group represented by formula (iv-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms. * indicates the bonding position. In formula (iv-1), R ４３ is an oxymethylene group (-OCH ２ -), oxyethylene group (-OCH ２ CH ２ -), represents an oxa group (-O-), or a divalent hydrocarbon group having 1 to 6 carbon atoms. In formula (iv-2), R ４４ This represents a hydrocarbon group with 1 to 8 carbon atoms. In formula (V), R ５１ Each of these independently represents a fluoro group (-F), a hydrocarbon group having 1 to 8 carbon atoms which may contain a fluoro group as a substituent, or a fluorine carbide group having 1 to 8 carbon atoms. k represents an integer between 0 and 2.

2. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the additive X contains at least one selected from the group consisting of compound (II) and compound (III).

3. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the additive X contains at least one selected from the group consisting of compound (II), compound (IV), and compound (V).

4. The non-aqueous electrolyte for lithium secondary batteries according to claim 3, wherein the additive X contains compound (II) and at least one selected from the group consisting of compound (IV) and compound (V).

5. The non-aqueous electrolyte for a lithium secondary battery according to claim 3, wherein the compound (IV) contains at least one selected from the group consisting of a compound represented by the following formula (IV-1) (IV-1), a compound represented by the following formula (IV-2) (IV-2), a compound represented by the following formula (IV-3) (IV-3), a compound represented by the following formula (IV-5) (IV-5), a compound represented by the following formula (IV-6) (IV-6), a compound represented by the following formula (IV-7) (IV-7), and a compound represented by the following formula (IV-8) (IV-8). 【Chemistry 2】

6. The non-aqueous electrolyte for a lithium secondary battery according to claim 5, wherein the additive X contains at least one selected from the group consisting of compound (IV-1), compound (IV-2), compound (IV-3), compound (IV-5), compound (IV-6), compound (IV-7), and compound (IV-8), and at least one selected from the group consisting of the difluorophosphate and compound (IV-4) represented by the following formula (IV-4). 【Transformation 3】

7. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the compound (I) contains the following compound (I-1). 【Chemistry 4】

8. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the content of compound (I) is 0.01% by mass or more and 5.0% by mass or less based on the total amount of the non-aqueous electrolyte for lithium secondary batteries.

9. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the content of the additive X is 0.01% by mass or more and 5.0% by mass or less with respect to the total amount of the non-aqueous electrolyte for batteries.

10. 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 a non-aqueous electrolyte for lithium secondary batteries according to any one of claims 1 to 9.

11. The lithium secondary battery precursor according to claim 10, 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.]

12. A step of preparing a lithium secondary battery precursor according to claim 10, The process involves charging and discharging the lithium secondary battery precursor. A method for manufacturing lithium secondary batteries, including [the specified component].

13. A lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor described in claim 10.

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