Non-aqueous electrolyte and non-aqueous electrolyte secondary batteries

Abstract

A non-aqueous electrolyte comprising: at least one carbonate compound selected from the group consisting of compounds represented by formula (I-1), formula (I-2), and formula (I-3); and at least one sulfonyl compound selected from the group consisting of compounds represented by formula (II) and formula (III). The definitions of the groups in each formula are as described in the specification.

Description

Technical Field

[0001] This disclosure relates to non-aqueous electrolytes and non-aqueous electrolyte secondary batteries. Background Technology

[0002] In recent years, there has been continuous progress in the high-performance development of small, lightweight, and high-output lithium-ion secondary batteries and other energy storage devices. With this advancement, their applications are expanding beyond small electrical products to include larger products such as automobiles. Lithium-ion secondary batteries require specific performance characteristics, including output characteristics, charge / discharge characteristics, and gas generation. For example, capacity retention and output characteristics after charge / discharge cycle testing have become crucial evaluation criteria.

[0003] Patent Document 1 describes a secondary battery using a non-aqueous electrolyte with specific cyclic carbonates such as 4,5-difluoro-1,3-dioxolan-2-one as a non-aqueous solvent, and reports improved cycle characteristics. Furthermore, since the specific cyclic carbonates do not solidify even at low temperatures of around 0°C, the battery's low-temperature cycle characteristics are improved.

[0004] In addition, Patent Document 2 describes the use of a non-aqueous electrolyte containing propylene trifluorocarbonate and reports improved battery performance compared to the use of ethylene carbonate or propylene carbonate.

[0005] Patent Document 1: Japanese Patent Application Publication No. 7-240232 Patent Document 2: Japanese Patent Application Publication No. 8-37025 Summary of the Invention

[0006] The problem that the invention aims to solve One aspect of this disclosure is to provide a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery with excellent battery characteristics after charge-discharge cycles.

[0007] Methods for solving problems The inventors of this application conducted repeated and in-depth research to solve the above-mentioned problems, and found that by combining specific carbonate compounds and specific sulfonyl compounds with non-aqueous electrolytes, the capacity retention rate and resistance rise rate of non-aqueous electrolyte secondary batteries after charge-discharge cycles can be improved, thus completing the present invention.

[0008] That is, as a form of this disclosure, the following content is included.

[0009] <1> A non-aqueous electrolyte comprising: at least one carbonate compound selected from the group consisting of a compound represented by formula (I-1), a compound represented by formula (I-2), and a compound represented by formula (I-3); and at least one sulfonyl compound selected from the group consisting of a compound represented by formula (II) and a compound represented by formula (III).

[0010] [Chemical Formula 1] (In formula (I-1), R) 11 Each can independently represent a carbon fluorocarbon group with 1 to 12 carbon atoms that may contain an oxa- group (-O-) as a substituent, or a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine groups (-F) and oxa- groups (-O-) as a substituent, where x represents an integer from 1 to 4. Wherein, R 11 At least one of them is the aforementioned fluorocarbon group, or the aforementioned hydrocarbon group containing a fluorine group (-F) as a substituent.

[0011] In equation (I-2), R 12 Each can independently represent a fluorine group (-F), a carbon fluorine group with 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent, or a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of a fluorine group (-F) and an oxetine group (-O-) as a substituent, where y represents an integer from 1 to 3.

[0012] In equation (I-3), R 13 Each can independently represent a carbon fluoro group having 1 to 12 carbon atoms that may contain an oxa- group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine groups (-F) and oxa- groups (-O-) as a substituent. Wherein, R 13 At least one of them is the aforementioned fluorocarbon group, or the aforementioned hydrocarbon group containing a fluorine group (-F) as a substituent. [Chemical Formula 2] (In formula (II), R) 21 The group represented by formula (ii-1), the group represented by formula (ii-2), or a divalent hydrocarbon group with 1 to 6 carbon atoms.

[0013] In equation (ii-1), R 22 It represents an oxymethylene group (-OCH2-), an oxyethylene group (-OCH2CH2-), an oxadiol group (-O-), or a divalent hydrocarbon group with 1 to 6 carbon atoms.

[0014] In equation (ii-2), R 23It represents a hydrocarbon group with 1 to 8 carbon atoms, or a hydrogen atom (-H).

[0015] In equation (III), R 3 This refers to a fluorine group (-F), a carbon-fluoro group having 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that contains a fluorine group (-F) as a substituent and may contain an oxetine group (-O-) as a substituent, (M 3 ) + This refers to alkali metal ions, alkaline earth metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidineium ions, piperidinium ions, or phosphonium ions. <2> The non-aqueous electrolyte as described in <1> is a non-aqueous electrolyte for use in non-aqueous electrolyte secondary batteries, wherein the non-aqueous electrolyte secondary battery comprises at least one of the following as a negative electrode active material: silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components.

[0016] <3> The non-aqueous electrolyte as described in <1> or <2>, wherein the total content of the aforementioned carbonate compounds is 0.1% to 10.0% by mass relative to the total amount of the non-aqueous electrolyte.

[0017] <4> The non-aqueous electrolyte as described in at least one of <1> to <3>, wherein the total content of the aforementioned sulfonyl compounds is 0.01% to 5.0% by mass relative to the total amount of the non-aqueous electrolyte.

[0018] <5> A non-aqueous electrolyte secondary battery, comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, wherein the negative electrode comprises a current collector and a negative electrode additive material layer formed on the current collector, the negative electrode additive material layer contains a negative electrode active material, the negative electrode active material comprises at least one selected from the group consisting of silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components, and the non-aqueous electrolyte is any one of <1> to <4>.

[0019] <6> The non-aqueous electrolyte secondary battery as described in <5>, wherein the aforementioned negative electrode active material comprises carbon elemental particles, and at least one of the group consisting of silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components.

[0020] <7> As described in <5>, in the non-aqueous electrolyte secondary battery, when the total mass of the aforementioned negative electrode active material is set to 100% by mass, the total mass of at least one of the aforementioned silicon elemental particles, the aforementioned silicon oxide particles, the aforementioned silicon carbide particles, and the aforementioned composite particles is 30% by mass or less.

[0021] Invention Effects According to one aspect of the present invention, the capacity retention and resistivity rise rate after charge-discharge cycles of non-aqueous electrolyte secondary batteries can be improved. Attached Figure Description

[0022] [ Figure 1 ] Figure 1 A simplified cross-sectional view illustrating an example of a lithium secondary battery precursor according to one embodiment of this disclosure.

[0023] [ Figure 2 ] Figure 2 A simplified cross-sectional view is provided to illustrate another example of a coin cell, which is a lithium secondary battery as described in this disclosure. Detailed Implementation

[0024] When describing the inventions involved in this disclosure, specific examples are given for illustration. However, as long as the description does not depart from the spirit of the inventions involved in this disclosure, it is not limited to the following content and can be implemented with appropriate modifications.

[0025] In this document, the range of values ​​indicated by “~” refers to the range including the values ​​before and after “~” as the lower and upper limits.

[0026] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced with the upper or lower limit of another numerical range described in other stages. Furthermore, the upper or lower limit of a numerical range described in this disclosure can be replaced with the values ​​shown in the embodiments.

[0027] In this disclosure, the amount of each component in the composition, unless otherwise specified, refers to the total amount of the multiple substances present in the composition, where multiple substances belonging to each component are present in the composition.

[0028] In this disclosure, the preferred combination of methods is a more preferred method.

[0029] In this publication, the term "process" includes not only individual processes, but also processes that achieve the desired purpose of the process, even if they cannot be clearly distinguished from other processes.

[0030] <Non-aqueous electrolyte> The non-aqueous electrolyte (hereinafter, sometimes simply referred to as "this non-aqueous electrolyte") as one embodiment of this disclosure contains: at least one carbonate compound (hereinafter, sometimes simply referred to as "carbonate compound") selected from the group consisting of a compound represented by formula (I-1), a compound represented by formula (I-2), and a compound represented by formula (I-3); and at least one sulfonyl compound (hereinafter, sometimes simply referred to as "sulfonyl compound") selected from the group consisting of a compound represented by formula (II) and a compound represented by formula (III).

[0031] [Chemical Formula 3] In equation (I-1), R 11 Each can independently represent a carbon fluorocarbon group with 1 to 12 carbon atoms that may contain an oxa- group (-O-) as a substituent, or a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine groups (-F) and oxa- groups (-O-) as a substituent, where x represents an integer from 1 to 4. Wherein, R 11 At least one of them is the aforementioned fluorocarbon group, or the aforementioned hydrocarbon group containing a fluorine group (-F) as a substituent.

[0032] In equation (I-2), R 12 Each can independently represent a fluorine group (-F), a carbon fluorine group with 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent, or a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of a fluorine group (-F) and an oxetine group (-O-) as a substituent, where y represents an integer from 1 to 3.

[0033] In equation (I-3), R 13 Each can independently represent a carbon fluoro group having 1 to 12 carbon atoms that may contain an oxa- group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine groups (-F) and oxa- groups (-O-) as a substituent. Wherein, R 13 At least one of them is the aforementioned fluorocarbon group, or the aforementioned hydrocarbon group containing a fluorine group (-F) as a substituent.

[0034] [Chemical Formula 4] In equation (II), R 21 The group represented by formula (ii-1), the group represented by formula (ii-2), or a divalent hydrocarbon group with 1 to 6 carbon atoms.

[0035] In equation (ii-1), R 22It represents an oxymethylene group (-OCH2-), an oxyethylene group (-OCH2CH2-), an oxadiol group (-O-), or a divalent hydrocarbon group with 1 to 6 carbon atoms.

[0036] In equation (ii-2), R 23 It represents a hydrocarbon group with 1 to 8 carbon atoms, or a hydrogen atom (-H).

[0037] In equation (III), R 3 This refers to a fluorine group (-F), a carbon-fluoro group having 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that contains a fluorine group (-F) as a substituent and may contain an oxetine group (-O-) as a substituent, (M 3 ) + It represents alkali metal ions, alkaline earth metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidineium ions, piperidinium ions, or phosphonium ions.

[0038] The inventors of this application have conducted in-depth research on non-aqueous electrolyte secondary batteries with excellent battery characteristics after charge-discharge cycles. The results show that by combining the aforementioned carbonate compound and the aforementioned sulfonyl compound with non-aqueous electrolyte, the capacity retention rate and resistance rise rate of non-aqueous electrolyte secondary batteries after charge-discharge cycles can be improved.

[0039] The following will provide detailed descriptions of "compounds represented by formula (I-1)," "compounds represented by formula (I-2)," and "compounds represented by formula (I-3)" as carbonate compounds, and "compounds represented by formula (II)" and "compounds represented by formula (III)" as sulfonyl compounds.

[0040] [Carbonate compounds] (The compound represented by formula (I-1)) [Chemical Formula 5] R 11Each term independently represents either a fluorocarbon group having 1 to 12 carbon atoms that may contain an oxo group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine (-F) and oxo group (-O-) as a substituent. The term "fluorocarbon group" refers to a group obtained by replacing all hydrogen atoms of a hydrocarbon group with fluorine atoms; it is sometimes also called a "fluorocarbon group" or "fluorocarbon group." Furthermore, it also includes the concept of perfluoroalkyl groups. In addition, fluorocarbon groups are not limited to those with a straight-chain structure; they can also be fluorocarbon groups with at least one structure selected from the group consisting of branched structures, cyclic structures, and carbon-carbon unsaturated bond structures (carbon-carbon double bonds and carbon-carbon triple bonds). Furthermore, "hydrocarbon group" is not limited to aliphatic hydrocarbon groups with a straight-chain structure, but can also be a hydrocarbon 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). Moreover, the number of these structures is not limited; therefore, (acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups are all included in "hydrocarbon group". Additionally, alkyl, alkenyl, alkynyl, aryl, etc., are naturally all included in "hydrocarbon group". Furthermore, "may contain at least one functional group selected from the group consisting of fluorine (-F) and oxo (-O-) as a substituent" means that the hydrogen atom of the hydrocarbon group can be replaced by a fluorine group (-F), and the carbon atom of the hydrocarbon group can be replaced by an oxo (-O-). Additionally, formula (I-1) has an insertion of (-R) into the cyclic structure of ethylene carbonate. 11 The structure of the (-R) group indicates that one or more (-R) groups have been introduced at the substitution positions in the ethylene carbonate structure. 11 The substitution site specifically becomes the ethylene (-CH2H2-) of the ethylene carbonate structure, allowing the four hydrogen atoms of the ethylene to be substituted, thus representing the introduced (-R) group. 11 The number of (-R) groups, x, is an integer from 1 to 4. That is, when x is 1, one (-R) group is introduced. 11 The ) group, the aforementioned ethylene, becomes (-C(R) 11 When x is 4, import 4 (-R) HCH2-), 11 The ) group, the aforementioned ethylene, becomes (-C(R) 11 )2C(R 11 )2-). In addition, "R 11At least one of them is the aforementioned fluorocarbon group, or the aforementioned hydrocarbon group containing a fluorine group (-F) as a substituent, and "the aforementioned hydrocarbon group containing a fluorine group (-F)" means that the aforementioned "hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine group (-F) and oxo group (-O-) as a substituent" is a group containing at least one fluorine group (-F). Therefore, R 11 At least one of them contains a fluorine group (-F).

[0041] R 11 When it is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. Additionally, R... 11 When the group is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0042] As R 11 Examples of fluorocarbon groups include trifluoromethyl (-CF3), pentafluoroethyl (-C2F5), n-heptafluoropropyl (-C3F7), pentafluorophenyl (-C6F5), trifluoromethoxy (-OCF3), pentafluoroethoxy (-OC2F5), and 3-trifluoromethoxyhexafluoropropyl.

[0043] As R 11 Examples of hydrocarbon groups include fluoromethyl (-CH2F), difluoromethyl (-CHF2), 2,2,2-trifluoroethyl (-CH2CF3), pentafluorophenoxy (-OC6F5), p-fluorophenyl (-C6H4F), and 2-trifluoromethoxyethyl.

[0044] From the viewpoint of improving the capacity retention rate and resistance rise rate after charge-discharge cycles, trifluoromethyl (-CF3) is particularly preferred.

[0045] x represents an integer from 1 to 4, preferably 1 or 2.

[0046] Examples of compounds represented by formula (I-1) include those represented by the following formulas. Non-aqueous electrolytes may contain two or more compounds represented by formula (I-1).

[0047] [Chemical Formula 6] (The compound represented by formula (I-2)) [Chemical Formula 7] R 12Each can independently represent "fluoro group (-F)," "a fluorocarbon group with 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent," or "a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluoro groups (-F) and oxetine groups (-O-) as substituents." The meanings of "fluorocarbon group" and "hydrocarbon group" are the same as those of R. 11 The situation is the same. Additionally, the cyclic structure of ethylene carbonate in formula (I-2) contains an insertion of (-R)... 12 The structure of the group is also related to R. 11 The situation is the same.

[0048] R 12 When it is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. Additionally, R... 11 When the group is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0049] As R 12 Examples include fluorinated (-F), trifluoromethyl (-CF3), pentafluoroethyl (-C2F5), n-heptafluoropropyl (-C3F7), pentafluorophenyl (-C6F5), trifluoromethoxy (-OCF3), pentafluoroethoxy (-OC2F5), n-heptafluoropropoxy (-OC3F7), pentafluorophenoxy (-OC6F5), fluoromethyl (-CH2F), difluoromethyl (-CHF2), 2,2,2-trifluoroethyl (-CH2CF3), p-fluorophenyl (-C6H4F), 2- Trifluoromethoxyethyl, methyl (-CH3), ethyl (-CH2CH3), vinyl (-CH=CH2), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), sec-butyl (-CH2CH(CH3)2), isobutyl (-CH2CH(CH3)2), tert-butyl (-C(CH3)3), hexyl (-CH2CH2CH2CH2CH2CH3), cyclohexyl (-C6H) 11 ), phenyl (-C6H5), etc.

[0050] From the viewpoint of improving capacity retention and resistance rise rate after charge-discharge cycles, fluorine-based (-F) is particularly preferred.

[0051] y represents an integer from 1 to 3, preferably 1.

[0052] Examples of compounds represented by formula (I-2) include those represented by the following formulas. Non-aqueous electrolytes may contain two or more compounds represented by formula (I-2).

[0053] [Chemical Formula 8] (The compound represented by formula (I-3)) [Chemical Formula 9] R 13 Each can independently represent "a fluorocarbon group having 1 to 10 carbon atoms that may contain an oxoyl (-O-) as a substituent" or "a hydrocarbon group having 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine (-F) and oxoyl (-O-) as a substituent." The meanings of "fluorocarbon group" and "hydrocarbon group" are the same as those of R. 11 The situation is the same. "R" 13 "At least one of them is the aforementioned fluorocarbon group, or the aforementioned hydrocarbon group containing a fluorine group (-F) as a substituent", thus making R 13 At least one of them contains a fluorine group (-F).

[0054] R 13 When it is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. Additionally, R... 11 When the group is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0055] As R 13 Examples of fluorocarbon groups include trifluoromethyl (-CF3), pentafluoroethyl (-C2F5), n-heptafluoropropyl (-C3F7), pentafluorophenyl (-C6F5), trifluoromethoxy (-OCF3), pentafluoroethoxy (-OC2F5), n-heptafluoropropoxy (-OC3F7), pentafluorophenoxy (-OC6F5), fluoromethyl (-CH2F), difluoromethyl (-CHF2), 2,2,2-trifluoroethyl (-CH2CF3), p-fluorophenyl (-C6H4F), and 2-trifluoromethoxyethyl. 13 Examples of hydrocarbon groups include methyl (-CH3), ethyl (-CH2CH3), vinyl (-CH=CH2), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), sec-butyl (-CH2CH(CH3)2), isobutyl (-CH2CH(CH3)2), tert-butyl (-C(CH3)3), hexyl (-CH2CH2CH2CH2CH2CH3), and cyclohexyl (-C6H) 11 ), phenyl (-C6H5), etc.

[0056] From the viewpoint of improving capacity retention and resistance rise rate after charge-discharge cycles, fluorinated (-F), trifluoromethyl (-CF3), methyl (-CH3), ethyl (-CH2CH3), vinyl (-CH=CH2), n-propyl (-CH2CH2CH3), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3), hexyl (-CH2CH2CH2CH2CH2CH3), and cyclohexyl (-C6H) are particularly preferred. 11 ), phenyl (-C6H5).

[0057] Examples of compounds represented by formula (I-3) include those represented by the following formulas. Non-aqueous electrolytes may contain two or more compounds represented by formula (I-3).

[0058] [Chemical Formula 10] Relative to the total amount of non-aqueous electrolyte (when the total amount of non-aqueous electrolyte is set to 100% by mass), the total content of carbonate compounds in the non-aqueous electrolyte is typically 0.1% by mass or more and 20% by mass or less, preferably 0.2% by mass or more as the lower limit, more preferably 0.5% by mass or more, further preferably 1.0% by mass or more, particularly preferably 1.5% by mass or more, and preferably 15% by mass or less as the upper limit, more preferably 12% by mass or less, further preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the total content of these compounds is within the aforementioned range, it becomes easier to control the capacity retention rate and resistivity rise rate after charge-discharge cycles to good values.

[0059] [Sulfonyl compounds] (The compound represented by formula (II)) [Chemical Formula 11] R 21 The term "divalent hydrocarbon group" refers to a group represented by formula (ii-1), a group represented by formula (ii-2), or a group with 1 to 6 carbon atoms. "Divalent hydrocarbon group" indicates a hydrocarbon group with two bonding positions, meaning it is not limited to aliphatic hydrocarbon groups with a straight-chain structure. It can be a group with at least one structure selected from branched structures, cyclic structures, and carbon-carbon unsaturated bond structures (carbon-carbon double bonds and carbon-carbon triple bonds). Additionally, it can also be an aromatic hydrocarbon group. That is, alkylene, alkenylene, ynylene, arylene, etc., are all included in "divalent hydrocarbon group".

[0060] R 21 When the group is a hydrocarbon group, the number of carbon atoms is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

[0061] [Chemical Formula 12] The wavy lines in formulas (ii-1) and (ii-2) indicate that their front ends are bonded to the two oxygen atoms (-O-) of formula (II), forming a cyclic sulfate ester structure.

[0062] R 22 This refers to "oxymethylene (-OCH2-)", "oxyethylene (-OCH2CH2-)", "oxazine (-O-)", or "a divalent hydrocarbon group with 1 to 6 carbon atoms". The meaning of "divalent hydrocarbon group" is the same as that of R. 21 The situation is the same. Additionally, the so-called R... 22 The terms are oxymethylene (-OCH2-), oxyethylidene (-OCH2CH2-), or oxadiol (-O-), indicating that the oxadiol is bonded to the sulfur atom (-S(=O)2O-) of formula (ii-1) to form a cyclic sulfate ester structure.

[0063] As R 22 Particularly preferred are oxymethylene (-OCH2-) and oxyethylidene (-OCH2CH2-).

[0064] R 23 Examples of hydrocarbon groups representing "carbon atoms 1-8" or "hydrogen atoms (-H)" include methyl (-CH3), ethyl (-CH2CH3), vinyl (-CH=CH2), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), sec-butyl (-CH2CH(CH3)2), tert-butyl (-C(CH3)3), hexyl (-CH2CH2CH2CH2CH2CH3), and cyclohexyl (-C6H) 11 ), phenyl (-C6H5), and from the viewpoint of improving the capacity retention rate and resistance rise rate after charge-discharge cycles, n-butyl (-CH2CH2CH2CH3) and hydrogen atom (-H) are particularly preferred.

[0065] Examples of compounds represented by formula (II) include cyclic sulfate compounds represented by formula (II-1), compounds represented by formulas (II-2) and (II-3) below. Non-aqueous electrolytes may contain two or more compounds represented by formula (II).

[0066] [Chemical Formula 13] (The compound represented by formula (III)) [Chemical Formula 14] R3 The terms "fluoro group (-F)," "fluorocarbon group with 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent," or "hydrocarbon group with 1 to 12 carbon atoms that contains a fluoro group (-F) as a substituent and may contain an oxetine group (-O-) as a substituent," are used. The meanings of "fluorocarbon group" and "hydrocarbon group" are the same as those of R. 11 The same applies. "Contains a fluorine group (-F) as a substituent and may contain an oxo group (-O-) as a substituent" means that at least one hydrogen atom of the hydrocarbon group is replaced by a fluorine group (-F), and the carbon atom of the hydrocarbon group may be replaced by an oxo group (-O-).

[0067] R 3 When it is a fluorocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less. Additionally, R... 3 When the group is a hydrocarbon group, the number of carbon atoms is preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0068] As R 3 Examples include fluorinated (-F), trifluoromethyl (-CF3), pentafluoroethyl (-C2F5), n-heptafluoropropyl (-C3F7), pentafluorophenyl (-C6F5), trifluoromethoxy (-OCF3), pentafluoroethoxy (-OC2F5), n-heptafluoropropoxy (-OC3F7), pentafluorophenoxy (-OC6F5), fluoromethyl (-CH2F), difluoromethyl (-CHF2), 2,2,2-trifluoroethyl (-CH2CF3), p-fluorophenyl (-C6H4F), and 2-trifluoromethoxyethyl.

[0069] (M) 3 ) + The term "alkali metal ion", "alkaline earth metal ion", "ammonium ion", "imidazolium ion", "pyridinium ion", "pyrrolidineium ion", "piperidineium ion", or "phosphonium ion" is particularly preferred, with lithium ion being the most preferred.

[0070] Examples of compounds represented by formula (III) include lithium fluorosulfonate (LiSO3F) represented by formula (III-1) and lithium trifluoromethanesulfonate (CF3SO3F) represented by formula (III-2). Non-aqueous electrolytes may contain two or more compounds represented by formula (III).

[0071] [Chemical Formula 15] Relative to the total amount of non-aqueous electrolyte (when the total amount of non-aqueous electrolyte is set to 100% by mass), the total content of sulfonyl compounds in the non-aqueous electrolyte is typically 0.01% by mass or more and 5.0% by mass or less, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and preferably 4.0% by mass or less, more preferably 3.0% by mass or less, further preferably 2.0% by mass or less, particularly preferably 1.5% by mass or less. When the total content of these compounds is within the aforementioned range, it becomes easier to control the capacity retention rate and resistivity rise rate after charge-discharge cycles to good values.

[0072] (Non-aqueous solvent) Non-aqueous electrolytes generally contain non-aqueous solvents (excluding compounds represented by formulas (I-1), (I-2), and (I-3). These are also referred to as "non-aqueous solvents" below). Various known substances can be appropriately selected as non-aqueous solvents. There can be only one non-aqueous solvent, or there can be two or more.

[0073] Examples of non-aqueous solvents include, for example, cyclic carbonates without fluorine (-F), fluorocarbon, or hydrocarbon groups; chain carbonates without fluorocarbon or hydrocarbon groups; fluorinated chain carbonates; aliphatic carboxylic acid esters; fluorinated aliphatic carboxylic acid esters; γ-lactones; fluorinated γ-lactones; cyclic ethers; fluorinated cyclic ethers; chain ethers; fluorinated chain ethers; nitriles; amides; lactams; nitromethane; nitrobenzene; sulfolane; trimethyl phosphate; dimethyl sulfoxide; and dimethyl sulfoxide phosphoric acid.

[0074] Examples of cyclic carbonates that do not have a fluorine (-F), fluorocarbon, or hydrocarbon group include ethylene carbonate (EC), propylene carbonate (PC), and butene carbonate (BC).

[0075] Examples of chain carbonates that do not have fluorocarbon or hydrocarbon groups include dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and dipropyl carbonate (DPC).

[0076] 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.

[0077] Examples of γ-lactones include, for example, γ-butyrolactone and γ-valerolactone.

[0078] Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxacyclopentane, 4-methyl-1,3-dioxacyclopentane, 1,3-dioxacyclohexane, and 1,4-dioxacyclohexane.

[0079] Examples of chain ethers include, for example, 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, and 1,2-dibutoxyethane.

[0080] Examples of nitrile compounds include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, and 3-methoxypropionitrile.

[0081] Examples of amides include, for example, N,N-dimethylformamide.

[0082] Examples of lactams include N-methylpyrrolidone, N-methyloxazolidinone, and N,N'-dimethylimidazolinone.

[0083] The non-aqueous solvent preferably comprises at least one type selected from the group consisting of cyclic carbonates that do not have a fluorine group (-F), a fluorocarbon group or a hydrocarbon group, and chain carbonates that do not have a fluorocarbon group or a hydrocarbon group.

[0084] In this case, the total proportion of cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, and fluorinated chain carbonates relative to the total amount of non-aqueous solvents 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.

[0085] The non-aqueous solvent preferably includes at least one selected from the group consisting of cyclic carbonates and chain carbonates.

[0086] In this case, the total proportion of cyclic carbonates and chain carbonates in the non-aqueous solvent is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, relative to the total amount of non-aqueous solvent.

[0087] The upper limit of the content of non-aqueous solvent relative to the total amount of non-aqueous electrolyte is preferably 99% by mass, more preferably 97% by mass, and even more preferably 90% by mass. The lower limit of the content of non-aqueous solvent relative to the total amount of non-aqueous electrolyte is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass.

[0088] From the viewpoint of further improving the dissociation property of electrolytes and the mobility of ions, the intrinsic viscosity of non-aqueous solvents is preferably below 10.0 mPa·s at 25°C.

[0089] (electrolytes) Non-aqueous electrolytes generally contain electrolytes.

[0090] 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.

[0091] Examples of fluorinated lithium salts include inorganic acid anionic salts and organic acid anionic salts.

[0092] Examples of inorganic acid anionic salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium hexafluorotantalate (LiTaF6).

[0093] Examples of anionic salts of organic acids include lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (Li(CF3SO2)2N), and lithium bis(pentafluoroethanesulfonyl)imide (Li(C2F5SO2)2N).

[0094] Among them, lithium hexafluorophosphate (LiPF6) is further preferred as a fluorinated lithium salt.

[0095] Examples of fluorine-free lithium salts include lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), and lithium decachloroborate (Li2B). 10 Cl 10 )wait.

[0096] When the electrolyte contains a fluorinated lithium salt, the proportion of the fluorinated lithium salt relative to the total amount of electrolyte 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.

[0097] When the fluorinated lithium salt contains lithium hexafluorophosphate (LiPF6), the content of lithium hexafluorophosphate (LiPF6) relative to the total amount of electrolyte 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.

[0098] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 3.0 mol / L or less, more preferably 0.5 mol / L or more and 2.0 mol / L or less.

[0099] When the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF6), the concentration of lithium hexafluorophosphate (LiPF6) in the non-aqueous electrolyte is preferably 0.1 mol / L or more than 3.0 mol / L, and more preferably 0.5 mol / L or more than 2.0 mol / L.

[0100] <Non-aqueous electrolyte secondary batteries> As another aspect of the present invention, a non-aqueous electrolyte secondary battery is a non-aqueous electrolyte secondary battery having a "positive electrode", a "negative electrode", a "non-aqueous electrolyte", and a "separator".

[0101] The following provides a detailed explanation of "positive electrode", "negative electrode", and "diaphragm".

[0102] (positive electrode) Typically, the positive electrode can be manufactured by dispersing the positive electrode active material, binder, conductive additives, and thickeners in a solvent to form a slurry. This slurry is then coated onto a current collector and dried and compressed to form a positive electrode binder material layer (also known as a "positive electrode active material layer") on the current collector.

[0103] Examples of positive electrode active materials include: Transition metal oxides or transition metal sulfides such as MoS2, TiS2, MnO2, and V2O5; LiCoO2, LiMnO2, LiMn2O4, LiNiO2, LiNi X Co （1-X） O2 (0 < X ​​< 1), LiNi x Co y Mn z O2 (where x, y, and z are each independently greater than 0 and less than 1.00, and the sum of x, y, and z is 0.99~1.00). (So-called "NCM"; for example, LiNi) 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2) and other composite oxides formed from lithium and transition metals; Li t Ni 1-x-yCo x Al y O2 (t is 0.95 to 1.15, x is 0 to 0.3, y is 0.1 to 0.2, and the sum of x and y is less than 0.5). (So-called "NCA"; for example, LiNi 0.8 Co 0.15 Al 0.05 O2) and other complex oxides formed from lithium, transition metals and typical metals; Conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polybenzoxanone, dimercaptothiadiazole, and polyaniline composites; Lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium manganese iron phosphate (LiMn) x Fe 1-x Lithium metal phosphates such as PO4 (0 < x < 1), lithium cobalt phosphate (LiCoPO4), lithium nickel phosphate (LiNiPO4), etc.

[0104] Examples of binders for the positive electrode include polyvinylidene fluoride (PVDF), examples of conductive additives for the positive electrode include carbon black (e.g., acetylene black), amorphous whiskers, and graphite, and examples of tackifiers for the positive electrode include carboxymethyl cellulose.

[0105] In addition, organic solvents such as N-methylpyrrolidone can be used as solvents for forming the slurry of the positive electrode.

[0106] When the total content of the positive electrode compound material layer is set to 100% by mass, the total content of the positive electrode active material in the positive electrode compound material layer is usually 70% to 97% by mass, preferably 75% or more by mass, and more preferably 95% or less by mass.

[0107] Materials used as current collectors for the positive electrode include aluminum, aluminum alloys, stainless steel, nickel, titanium, tantalum, carbon cloth, and carbon paper.

[0108] (negative electrode) Typically, the negative electrode can be manufactured by dispersing the negative electrode active material and binder (adhesive), conductive additives and thickeners as needed in a solvent to form a slurry. The slurry is then coated onto the current collector and dried and compressed to form a negative electrode binder material layer (also known as the "negative electrode active material layer") on the current collector.

[0109] The elements or compounds that can be used as negative electrode active materials can be classified as: (1) carbon elements and carbon compounds that can be doped / dedoped with lithium ions; (2) metals and alloys that can be alloyed with lithium; (3) oxides, nitrides and carbides that can be doped / dedoped with lithium ions. When the negative electrode active material is silicon, etc., particulate (powder) elements or compounds are usually used. In addition, the negative electrode active material used is not limited to one type, and two or more types can be used in combination.

[0110] As the negative electrode active material, preferably, it comprises at least one of the following groups: carbon elemental particles, silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components. Examples of carbon elemental particles include graphite (natural graphite, artificial graphite) particles, carbon black particles, activated carbon particles, and amorphous carbon particles. Examples of artificial graphite include graphitized MCMB and graphitized MCF. Examples of amorphous carbon materials include hard carbon, coke, mesophase carbon microspheres (MCMB) obtained by sintering at temperatures below 1500°C, and mesophase pitch carbon fibers (MCF).

[0111] When the element or compound that becomes the negative electrode active material is in the form of particles (powder), examples of its detailed shape include fibrous, spherical, potato-shaped, and scaly.

[0112] When the negative electrode active material contains carbon elemental particles, the median particle size D50 of the carbon elemental particles is usually 1 μm to 30 μm, with the lower limit preferably being 10 μm or more, more preferably 15 μm or more, and the upper limit preferably being 25 μm or less, more preferably 20 μm or less.

[0113] When the negative electrode active material contains carbon elemental particles, the BET specific surface area of ​​the carbon elemental is typically 1.0 m². 2 / g~5.0m 2 / g, with a lower limit preferably 2.0m 2 / g or more, preferably 3.0m 2 / g or more, with the upper limit preferably 4.5m 2 / g or less, preferably 4.0m 2 / g or less.

[0114] Silicon oxide can be in the form of SiO x It is indicated that x is a variable, that is, the content of oxygen atoms in silicon oxide is not particularly limited. x usually satisfies 0≤x<2, the lower limit is preferably 0.2 or more, more preferably 0.4 or more, even more preferably 0.6 or more, the upper limit is preferably 1.8 or less, more preferably 1.6 or less, even more preferably 1.4 or less.

[0115] The median particle size D50 of silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles containing silicon and carbon components is typically 0.5 μm to 20 μm, with the lower limit preferably being 1.0 μm or more, more preferably 3.0 μm or more, and the upper limit preferably being 15 μm or less, more preferably 10 μm or less.

[0116] The BET specific surface area of ​​elemental silicon particles, silicon oxide particles, silicon carbide particles, and composite particles containing both silicon and carbon components is typically 1.0 m². 2 / g~5.0m 2 / g, with the lower limit preferably being 1.5m. 2 / g or more, preferably 2.0m 2 / g or more, with the upper limit preferably 4.5m 2 / g or less, preferably 4.0m 2 / g or less.

[0117] When the negative electrode active material comprises at least one of the following: carbon elemental particles, silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles containing silicon and carbon components, and the total mass of the negative electrode active material is set to 100% by mass, the total mass of silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles containing silicon and carbon components in the negative electrode active material is typically 1% to 20% by mass, preferably 3% or more by mass at the lower limit, more preferably 5% or more by mass at the higher limit, preferably 18% or less by mass at the lower limit, and more preferably 15% or less by mass at the upper limit.

[0118] When the negative electrode active material comprises at least one of the following: carbon elemental particles, silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components, and the total mass of the negative electrode active material is set to 100% by mass, the total mass of the carbon elemental particles in the negative electrode active material is typically 70% to 99% by mass, preferably 80% by mass or more, more preferably 85% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. If the total mass of silicon elemental particles, etc., is within the aforementioned range, it becomes easier to ensure a balance between the energy density and capacity retention rate of the lithium-ion secondary battery.

[0119] When the negative electrode mixture material layer is set to 100% by mass, the total content of negative electrode active material in the negative electrode mixture material layer is usually 70% to 99.5% by mass, with the lower limit preferably above 75% by mass and the upper limit preferably below 99% by mass.

[0120] Examples of bonding materials used as negative electrodes include styrene-butadiene rubber (SBR).

[0121] When the negative electrode binder material layer is set to 100% by mass, the total content of the copolymer of the binder material in the negative electrode binder material layer is usually 0.1% to 5% by mass, preferably 0.5% or more by mass, more preferably 1.0% or more by mass, and preferably 3% or less by mass, more preferably 2% or less by mass.

[0122] The negative electrode mixture layer preferably also contains a conductive additive. Examples of conductive additives for the negative electrode include carbon black (e.g., acetylene black), carbon nanotubes, amorphous whiskers, and graphite.

[0123] When the negative electrode additive material layer is set to 100% by mass, the total content of conductive additives in the negative electrode additive material layer is usually 0.01% to 3% by mass, with the lower limit preferably being 0.05% by mass or more, more preferably 0.1% by mass or more, and the upper limit preferably being 2% by mass or less, more preferably 1% by mass or less.

[0124] The negative electrode mixture material layer preferably also includes a thickener. By including a thickener, the viscosity of the slurry can be easily adjusted, thus improving productivity. Examples of thickeners for the negative electrode include cellulose derivatives such as carboxymethyl cellulose (CMC), carboxyethyl cellulose, and hydroxyethyl cellulose, polyethylene oxide and its modified forms, polyvinyl alcohol and its modified forms, and polysaccharides.

[0125] When the negative electrode mixture material layer is set to 100% by mass, the total content of the thickener in the negative electrode mixture material layer is usually 0.1% to 5% by mass, with the lower limit preferably being 0.5% or more, more preferably 1.0% or more, and the upper limit preferably being 3% or less, more preferably 2% or less.

[0126] The slurry may contain a solvent. Examples of solvents include water, acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, and ethylenediamine. The solvent may also be a mixed solvent obtained by mixing the aforementioned solvents.

[0127] Materials used as current collectors for the negative electrode include copper, nickel, stainless steel, and nickel-plated steel.

[0128] <Septum> One aspect of the present invention is a non-aqueous electrolyte secondary battery comprising a "positive electrode", a "negative electrode", a "non-aqueous electrolyte", and a "separator". The separator can be a porous resin plate. The material for the porous resin plate can be resin, non-woven fabric containing the resin, etc. The resin can be polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, polyamide, etc.

[0129] The separator is preferably a porous resin sheet with a single-layer or multi-layer structure. Regarding the material of the porous resin sheet, one or more polyolefin resins are used as the main body. The thickness of the separator is preferably 5 μm to 30 μm. The separator is preferably disposed between the positive and negative electrodes.

[0130] <Shell> The shape of the casing is not particularly limited and can be appropriately selected according to the intended use of the lithium secondary battery precursor in this disclosure.

[0131] Examples of housings include housings containing laminated films and housings formed by battery compartments and battery compartment covers.

[0132] <Specific Examples of Lithium-ion Secondary Battery Precursors> Figure 1 A simplified cross-sectional view of a stacked lithium secondary battery precursor, which is an example of a lithium secondary battery precursor as described in this disclosure.

[0133] like Figure 1 As shown, the lithium secondary battery precursor 1 is a stacked battery precursor.

[0134] In detail, in the lithium secondary battery precursor 1, the battery element 10 is encapsulated inside an outer package 30. The outer package 30 is formed of a laminated film. A positive electrode wire 21 and a negative electrode wire 22 are each mounted on the battery element 10. The positive electrode wire 21 and the negative electrode wire 22 are each led out from the inside of the outer package 30 in opposite directions to the outside.

[0135] Battery element 10, such as Figure 1 As shown, the electrode 11, the separator 13, and the negative electrode 12 are stacked together. The positive electrode 11 is formed by forming a positive electrode flux layer 11B on two main surfaces of the positive electrode current collector 11A. The negative electrode 12 is formed by forming a negative electrode flux layer 12B on two main surfaces of the negative electrode current collector 12A. The positive electrode flux layer 11B formed on one main surface of the positive electrode current collector 11A of the positive electrode 11 is opposite to the negative electrode flux 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, separated by the separator 13.

[0136] The non-aqueous electrolyte of this disclosure is injected into the interior of the outer encapsulation 30 of the lithium secondary battery precursor 1. The non-aqueous electrolyte of this disclosure permeates into the positive electrode flux layer 11B, the separator 13, and the negative electrode flux layer 12B. In the lithium secondary battery precursor 1, a single cell layer 14 is formed by adjacent positive electrode flux layer 11B, separator 13, and negative electrode flux layer 12B. The positive and negative electrodes can also be products formed by forming each active material layer on one surface of each current collector.

[0137] The lithium secondary battery precursor 1 is a stacked lithium secondary battery precursor, but the lithium secondary battery precursor in this disclosure is not limited to this; for example, it can also be a wound lithium secondary battery precursor. A wound lithium secondary battery precursor is formed by overlapping and winding a positive electrode, a separator, a negative electrode, and a separator in this order. Wound lithium secondary battery precursors include cylindrical lithium secondary battery precursors and prismatic lithium secondary battery precursors.

[0138] like Figure 1 As shown, in the lithium secondary battery precursor 1, the positive electrode wire and the negative electrode wire each protrude from the inside of the outer package 30 in opposite directions on the outer package 30, but this disclosure is not limited to this. For example, the positive electrode wire and the negative electrode wire may also protrude from the inside of the outer package 30 in the same direction on the outer package 30.

[0139] As an example of the lithium secondary battery described in this disclosure, which will be described later, a lithium secondary battery obtained by charging and discharging a lithium secondary battery precursor 1 can be cited.

[0140] Figure 2 A simplified cross-sectional view of a button-type lithium secondary battery precursor, which is another example of a lithium secondary battery precursor as described in this disclosure.

[0141] Figure 2 In the button-type lithium secondary battery precursor shown, a disc-shaped negative electrode 42, a separator 45 filled with non-aqueous electrolyte, a disc-shaped positive electrode 41, and spacers 47 and 48 made of stainless steel or aluminum, as needed, are stacked in this order between a positive electrode box 43 (hereinafter also referred to as the "battery box") and a sealing plate 44 (hereinafter also referred to as the "battery box cover"). The positive electrode box 43 and the sealing plate 44 are sealed together by a gasket 46.

[0142] In this example, the non-aqueous electrolyte of this disclosure is used as the non-aqueous electrolyte injected into the diaphragm 45.

[0143] As an example of the lithium secondary battery described later in this disclosure, further examples can be given regarding... Figure 2 The lithium secondary battery is obtained by charging and discharging the button-shaped lithium secondary battery precursor shown.

[0144] [Lithium-ion secondary batteries and their manufacturing methods] The method for manufacturing a lithium secondary battery disclosed herein includes the following steps: The steps for preparing the lithium secondary battery precursor of the aforementioned disclosure (hereinafter also referred to as the "preparation steps"); and The process of charging and discharging the aforementioned lithium secondary battery precursor.

[0145] The lithium secondary battery disclosed herein is a lithium secondary battery obtained by charging and discharging the lithium secondary battery precursor described above.

[0146] The lithium secondary battery and its manufacturing method disclosed herein can reduce the rate of increase in room temperature resistance when the lithium secondary battery is stored at high temperatures.

[0147] The preparation process can be a process of simply preparing a pre-manufactured lithium secondary battery precursor of the present disclosure for use in the charging and discharging process, or it can be a process of manufacturing the lithium secondary battery precursor of the present disclosure.

[0148] Regarding lithium secondary battery precursors, as described above.

[0149] In the charging and discharging process, the charging and discharging of the lithium secondary battery precursor can be carried out according to known methods.

[0150] In this process, the lithium secondary battery precursor can be repeatedly charged and discharged multiple times.

[0151] As described above, through this charging and discharging, an SEI (Solid Electrolyte Interface) film is ideally formed on the surface of the positive electrode (especially the positive electrode active material) and / or the negative electrode (especially the negative electrode active material) in the lithium secondary battery precursor.

[0152] Regarding the charging and discharging process, it is preferable that, for the lithium secondary battery precursor, the combination of charging and discharging is carried out more than once in an environment of 25°C to 70°C.

[0153] Example The following are examples of embodiments of this disclosure, but this disclosure is not limited to the following embodiments.

[0154] Unless otherwise specified, "%" hereafter refers to "quality%".

[0155] [Example 1] <Preparation of Non-Aqueous Electrolytes> Ethylene carbonate (hereinafter "EC"), dimethyl carbonate (hereinafter "DMC"), and ethyl methyl carbonate (hereinafter "EMC") are mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This yields a mixed solvent as a non-aqueous solvent. LiPF6, serving as the electrolyte, is dissolved in the obtained mixed solvent at a concentration of 1.0 mol / L in the final non-aqueous electrolyte to obtain an electrolyte (hereinafter also referred to as the "basic electrolyte"). The obtained basic electrolyte is then combined with a compound represented by formula (I-2-1) at a concentration of 2.0% by mass relative to the total amount of the final non-aqueous electrolyte, and further combined with a compound represented by formula (II-1) at a concentration of 2.0% by mass relative to the total amount of the non-aqueous electrolyte to obtain a non-aqueous electrolyte.

[0156] [Chemical Formula 16] <The Making of Positive Electrode> LiNi will be used as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (94% by mass), carbon black (3% by mass) as a conductive additive, and polyvinylidene fluoride (PVdF) (3% by mass) as a binder were mixed to obtain a mixture. The mixture was dispersed in N-methylpyrrolidone solvent to obtain a positive electrode slurry. A 20 μm thick aluminum foil was prepared as the positive electrode current collector. The obtained positive electrode slurry was coated onto the aluminum foil, dried, and then rolled using a press to obtain a sheet-like positive electrode. The positive electrode comprises a positive electrode current collector and a positive electrode active material layer.

[0157] <Making the Negative Electrode> 92.15% by mass of graphite and silicon dioxide (SiO2) were used as the negative electrode active material. x (x=1), 4.85% by mass of silicon monoxide, 1.5% by mass of sodium carboxymethyl cellulose dispersed in pure water as a tackifier (solid content), and 1.5% by mass of styrene-butadiene rubber (SBR) dispersed in pure water as a binder (solid content) were mixed to obtain a negative electrode slurry. A copper foil with a thickness of 10 μm was prepared as the negative electrode current collector. The obtained negative electrode slurry was coated onto the copper foil, dried, and then rolled using 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.

[0158] <Preparation of the diaphragm> A porous polyethylene film is prepared as a diaphragm.

[0159] <Preparation of Lithium-ion Secondary Battery Precursors> Separately, the negative electrode is punched into a disc shape with a diameter of 14 mm, the positive electrode into a disc shape with a diameter of 13 mm, and the separator into a disc shape with a diameter of 17 mm. This yields button-shaped negative electrodes, button-shaped positive electrodes, and button-shaped separators. These button-shaped negative electrodes, separators, and positive electrodes are then stacked in this order within a stainless steel battery case (size: 2032). Next, 20 μL of non-aqueous electrolyte is injected into the battery case, immersing the separator, positive electrode, and negative electrode in the electrolyte. Then, an aluminum plate (1.2 mm thick, 16 mm in diameter) and a spring are placed on the positive electrode, and the battery case lid is sealed using a polypropylene gasket. Through these operations, a battery with… Figure 2 The diagram shows a button-shaped lithium-ion secondary battery precursor (i.e., a lithium-ion secondary battery before charging and discharging). The lithium-ion secondary battery precursor has a diameter of 20 mm and a height of 3.2 mm.

[0160] <The Manufacturing of Lithium-ion Secondary Batteries> For the aforementioned lithium-ion secondary battery precursor, the charging process up to 4.2V and the discharging process up to 2.5V were repeated three times within a temperature range of 25℃ to 70℃ to obtain a lithium-ion secondary battery.

[0161] <Determination of Initial Discharge Capacity> The lithium-ion secondary battery was charged in a constant temperature bath at 25°C until it reached 4.2V, and then discharged until it reached 2.5V. The discharge capacity [mAh] (hereinafter also referred to as "initial discharge capacity") was measured.

[0162] <Determination of initial resistance> The lithium-ion secondary battery, after initial discharge capacity measurement, was charged to 3.7V. Then, in a constant-temperature bath at -20°C, the voltage drop (equal to the voltage before discharge start - voltage at 10 seconds after discharge start) based on a CC10s discharge was measured at various discharge rates from 0.1C to 1.0C. A CC10s discharge refers to discharging with 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 1.0C), the DC resistance [Ω] was measured as the initial resistance value.

[0163] <Charge-Discharge Cycle Test> Next, the lithium-ion secondary battery, after initial resistance measurement, was charged at a constant current at a charging rate of 0.5C in a constant temperature bath at 25°C until it reached 4.2V. Then, it was discharged at a constant current at a discharging rate of 0.5C until it reached 2.5V. This charge-discharge cycle was repeated 100 times.

[0164] <Determination of discharge capacity retention rate and calculation of relative value after charge-discharge cycles> Next, the discharge capacity of the lithium-ion secondary battery after the charge-discharge cycle test was measured using the same method as the initial discharge capacity. The discharge capacity of the lithium-ion secondary battery after the charge-discharge cycle test was also measured using the same method for Comparative Example 1, which will be described later. The discharge capacity retention rate after charge-discharge cycles of Example 1, with the discharge capacity retention rate after charge-discharge cycles of Comparative Example 1 set to 100%, was calculated as a relative value (see the formula below).

[0165] The discharge capacity retention rate (relative value) after charge-discharge cycles of Example 1 = (Discharge capacity retention rate after charge-discharge cycles of Example 1) / (Discharge capacity retention rate after charge-discharge cycles of Comparative Example 1) × 100 <Determination of the rate of increase in resistance after charge-discharge cycles and calculation of the relative value> Next, the resistance value of the lithium-ion secondary battery after the charge-discharge cycle test was measured using the same method as for the initial resistance value. Regarding Comparative Example 1 described later, the resistance value (DCIR: Direct Current Internal Resistance) of the lithium-ion secondary battery after the charge-discharge cycle test was also measured using the same method. The resistance rise rate after charge-discharge cycles for each embodiment, with the resistance rise rate after charge-discharge cycles of Comparative Example 1 set to 100%, was calculated as a relative value (see the formula below).

[0166] The rate of resistance rise after charge-discharge cycles in each embodiment (relative value) = (the rate of resistance rise after charge-discharge cycles in each embodiment) / (the rate of resistance rise after charge-discharge cycles in Comparative Example 1) × 100 [Examples 2-12, Comparative Examples 1-4] Except for changing the types and amounts of additives used to prepare the non-aqueous electrolyte as shown in Table 1, the same procedures as in Example 1 were performed. The results are shown in Table 1. The additives added to the non-aqueous electrolytes of Examples 2-12 and Comparative Examples 1-4 are each as follows. In addition, "-" in Table 1 indicates that no additives were added.

[0167] [Chemical Formula 17] [Table 1] As shown in Table 1, the lithium-ion secondary batteries using the non-aqueous electrolytes of Examples 1-12 containing carbonate compounds and sulfonyl compounds showed improved capacity retention and resistance rise rate after charge-discharge cycles compared to the lithium-ion secondary batteries using the non-aqueous electrolytes of the comparative examples that did not contain these additives.

[0168] Specifically, Examples 1-4 maintain capacity retention and exhibit superior resistance increase rate after charge-discharge cycles compared to Comparative Example 2. Furthermore, Examples 5-8 maintain capacity retention and exhibit superior resistance increase rate after charge-discharge cycles compared to Comparative Example 3. Examples 9-12 maintain capacity retention and exhibit superior resistance increase rate after charge-discharge cycles compared to Comparative Example 4.

[0169] The full disclosure of Japanese Patent Application No. 2024-54730, filed on March 28, 2024, is incorporated herein by reference.

[0170] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the extent that each document, patent application and technical standard is incorporated by reference to the extent that it is specifically and separately described.

[0171] Explanation of reference numerals in the attached figures 1. Precursor for lithium secondary batteries 10 Battery Components 11 Positive electrode 11A Positive Current Collector 11B Positive Electrode Mixture Material Layer 12 Negative electrode 12A negative current collector 12B Negative Electrode Mixture Material Layer 13. Diaphragm 14 Single cell layers 21 Positive wire 22 Negative conductor 30 External package 41 Positive electrode 42 Negative electrode 43 Positive electrode box 44 Sealing board 45 Diaphragm 46 gasket 47, 48 partition plates

Claims

1. Non-aqueous electrolyte, containing: At least one carbonate compound selected from the group consisting of compounds represented by formula (I-1), formula (I-2), and formula (I-3); and At least one sulfonyl compound selected from the group consisting of compounds represented by formula (II) and compounds represented by formula (III) below. [Chemical Formula 1] In equation (I-1), R 11 Each of these groups independently represents a fluorocarbon group with 1 to 12 carbon atoms that may contain an oxoyl (-O-) as a substituent, or a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine (-F) and oxoyl (-O-) as a substituent, where x represents an integer from 1 to 4. R 11 At least one of them is the fluorocarbon group, or the hydrocarbon group containing a fluorine group (-F) as a substituent. In equation (I-2), R 12 Each can independently represent a fluorine group (-F), a carbon fluoro group with 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent, or a hydrocarbon group with 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine groups (-F) and oxetine groups (-O-) as a substituent, where y represents an integer from 1 to 3. In equation (I-3), R 13 Each independently represents a carbon fluoro group having 1 to 12 carbon atoms that may contain an oxoyl (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that may contain at least one functional group selected from the group consisting of fluorine (-F) and oxoyl (-O-) as a substituent, wherein R 13 At least one of them is the fluorocarbon group, or the hydrocarbon group containing a fluorine group (-F) as a substituent; [Chemical Formula 2] In equation (II), R 21 The group represented by formula (ii-1), the group represented by formula (ii-2), or a divalent hydrocarbon group having 1 to 6 carbon atoms, In equation (ii-1), R 22 This indicates an oxymethylene group (-OCH2-), an oxyethylidene group (-OCH2CH2-), an oxetyl group (-O-), or a divalent hydrocarbon group having 1 to 6 carbon atoms. In equation (ii-2), R 23 Represents a hydrocarbon group with 1 to 8 carbon atoms, or a hydrogen atom (-H); In equation (III), R 3 This refers to a fluorine group (-F), a carbon-fluoro group having 1 to 12 carbon atoms that may contain an oxetine group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms that contains a fluorine group (-F) as a substituent and may contain an oxetine group (-O-) as a substituent, (M 3 ) + It represents alkali metal ions, alkaline earth metal ions, ammonium ions, imidazolium ions, pyridinium ions, pyrrolidineium ions, piperidinium ions, or phosphonium ions.

2. The non-aqueous electrolyte as described in claim 1, wherein the non-aqueous electrolyte secondary battery comprises at least one selected from the group consisting of elemental silicon particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components as the negative electrode active material.

3. The non-aqueous electrolyte as described in claim 1, wherein, The total content of the carbonate compounds is 0.1% to 20.0% by mass relative to the total amount of non-aqueous electrolyte.

4. The non-aqueous electrolyte as described in claim 1, wherein, The total content of the sulfonyl compound is 0.01% to 5.0% by mass relative to the total amount of non-aqueous electrolyte.

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

6. The non-aqueous electrolyte secondary battery as described in claim 5, wherein, The negative electrode active material comprises carbon elemental particles, and at least one of the following groups: silicon elemental particles, silicon oxide particles, silicon carbide particles, and composite particles comprising silicon and carbon components.

7. The non-aqueous electrolyte secondary battery as described in claim 5, wherein, When the total mass of the negative electrode active material is set to 100% by mass, the total mass of at least one of the following selected particles—silicon particles, silicon oxide particles, silicon carbide particles, and composite particles—is less than 30% by mass.

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