Non-aqueous electrolyte and non-aqueous electrolyte secondary batteries

Abstract

The objective is to provide a non-aqueous electrolyte that can suppress the increase in resistance after high-temperature storage of a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery equipped with the same. [Solution] A non-aqueous electrolyte comprising: at least one first component selected from the group consisting of carbodiimide compounds represented by the following formula (I); at least one second component selected from the group consisting of phosphates represented by the following formula (II); cyclic carbonate compounds represented by the following formula (III); cyclic sulfonic acid ester compounds represented by the following formula (IV); and isocyanate compounds represented by the following formula (V). JPEG2026102378000020.jpg71163

Description

Technical Field

[0001] The present disclosure relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery.

Background Art

[0002] Power storage devices such as lithium-ion secondary batteries, which are small, lightweight, and have high output, have been further improved in performance in recent years. Along with the improvement in performance, their use has spread not only to small electrical products but also to large product fields such as automobiles. Lithium-ion secondary batteries are required to meet specific requirements for various characteristics such as output characteristics, charge-discharge characteristics, and gas generation. For example, a small decrease in output when stored for a long period (e.g., two weeks or more) under a high-temperature environment (e.g., 60°C or higher) is also a very important evaluation item. Patent Document 1 discloses an invention of a non-aqueous electrolyte in which lithium trifluoromethanesulfonate (TFMSLi), lithium difluorophosphate (LiDFP), and lithium bis(oxalato)borate (LiBOB) are blended. It is also disclosed that when the non-aqueous electrolyte described in Patent Document 1 is used, the resistance value at -10°C after storing a lithium-ion secondary battery at 60°C for 5 days is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, from the viewpoints of battery manufacturing cost, storage convenience, etc., development of a non-aqueous electrolyte capable of long-term high-temperature storage is required. Therefore, the object of this disclosure is to provide a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery containing the same that can suppress the increase in resistance after high-temperature storage (for example, storage in an environment of 60°C or higher for two weeks) of non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries. [Means for solving the problem]

[0005] The following embodiments are included as specific means for solving the aforementioned problems.

[0006] <1> A first component selected from the group consisting of carbodiimide compounds represented by the following formula (I), A second component selected from the group consisting of a phosphate represented by the following formula (II), a cyclic carbonate compound represented by the following formula (III), a cyclic sulfonic acid ester compound represented by the following formula (IV), and an isocyanate compound represented by the following formula (V), A non-aqueous electrolyte containing [a specific component]. [ka] In formula (I), R 11 and R 12 Each of these independently represents either a hydrocarbon group having 1 to 12 carbon atoms, or a trialkylsilyl group having 3 to 18 carbon atoms. In formula (II), R 21 Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent; each independently represents a halogen group; a represents an integer from 1 to 3; b represents 4 when a is 1, 2 when a is 2, and 0 when a is 3; and c represents an integer from 1 to 3. In formula (III), R 31Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, and h represents an integer from 1 to 4. In formula (IV), R 41 Each of these independently represents a C1-C12 hydrocarbon group which may contain a halogen group, a C1-C12 fluorine carbide group which may contain an oxa group (-O-) as a substituent, or a C1-C12 hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and i represents an integer from 0 to 4. In formula (V), R 51 (where j represents a C1-C24 j+1 valent hydrocarbon group which may contain at least one functional group selected from the group consisting of halogen groups and oxa groups (-O-) as substituents, and j represents an integer from 0 to 4.) <2> The total content of the first component is 0.0001% by mass to 5.0000% by mass relative to the total amount of the non-aqueous electrolyte. <1> The non-aqueous electrolyte described above. <3> The total content of the second component is 0.0001% by mass to 5.0000% by mass relative to the total amount of the non-aqueous electrolyte. <1> or <2> The non-aqueous electrolyte described above. <4> It comprises a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. The non-aqueous electrolyte is <1> ~ <3> A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte is one of the non-aqueous electrolytes listed in any one of the following documents. [Effects of the Invention]

[0007] According to one aspect of this disclosure, a non-aqueous electrolyte that suppresses resistance increase after high-temperature storage of a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery is provided, and a non-aqueous electrolyte secondary battery equipped therewith is provided. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic cross-sectional view showing a stacked non-aqueous electrolyte secondary battery precursor, which is an example of a non-aqueous electrolyte secondary battery precursor of this disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view showing a coin-shaped non-aqueous electrolyte secondary battery precursor, which is another example of a non-aqueous electrolyte secondary battery precursor of the present disclosure. [Modes for carrying out the invention]

[0009] In explaining this disclosure, specific examples will be given, but the invention is not limited to the following and can be implemented with appropriate modifications, as long as it does not deviate from the spirit of the invention.

[0010] When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0011] In this disclosure, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described in this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may include multiple types of particles. The amount of each component in the composition means the total amount of multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component are present in the composition. In this disclosure, a preferred combination of embodiments is a more preferred embodiment. In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0012] In this disclosure, alkyl groups and alkylene groups include linear, branched, and cyclic groups unless otherwise specified.

[0013] In the present disclosure, when a compound is represented by a structural formula, it may be represented by a structural formula in which symbols (C and H) representing carbon atoms and hydrogen atoms in a hydrocarbon group and / or a hydrocarbon chain are omitted.

[0014] <Non-aqueous electrolyte> The non-aqueous electrolyte of the present disclosure includes at least one first component selected from the group consisting of carbodiimide compounds represented by the following formula (I), a phosphate represented by the following formula (II), a cyclic carbonate compound represented by the following formula (III), a cyclic sulfonate ester compound represented by the following formula (IV), and at least one second component selected from the group consisting of isocyanate compounds represented by the following formula (V).

[0015]

Chemical formula

[0016] In formula (I), R 11 and R 12 each independently represents a hydrocarbon group having 1 to 12 carbon atoms or a trialkylsilyl group having 3 to 18 carbon atoms. In formula (II), R 21 each independently represents a single bond or a divalent hydrocarbon group having 1 to 6 carbon atoms that may contain at least one functional group selected from the group consisting of a halogeno group and an oxa group (-O-) as a substituent, X each independently represents a halogeno group, a represents an integer of 1 to 3, b represents 4 when a is 1, 2 when a is 2, and 0 when a is 3, and c represents an integer of 1 to 3. In formula (III), R 31 each independently represents a fluorocarbon 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 a fluoro group (-F) and an oxa group (-O-) as a substituent, and h represents an integer of 1 to 4. In formula (IV), R 41Each of these independently represents a C1-C12 hydrocarbon group which may contain a halogen group, a C1-C12 fluorine carbide group which may contain an oxa group (-O-) as a substituent, or a C1-C12 hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and i represents an integer from 0 to 4. In formula (V), R 51 This represents a C1-C24 j+1 valent hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and j represents an integer from 0 to 4.

[0017] The inventors, after diligent research to solve the aforementioned problems, have found that by using a non-aqueous electrolyte containing a first component and a second component, the increase in resistance after high-temperature storage of lithium-ion secondary batteries can be effectively suppressed. While the first component has an effect of suppressing initial resistance, lithium-ion secondary batteries containing only the first component still have room for improvement in terms of resistance increase after high-temperature storage and capacity retention rate. On the other hand, the second component is thought to play a role in compensating for these shortcomings. In other words, by combining the first and second components, the increase in resistance after high-temperature storage is suppressed. As a result, it is possible to provide a lithium-ion secondary battery with excellent suppression of initial resistance and capacity retention rate after high-temperature storage.

[0018] [First component: Carbodiimide compound represented by formula (I)] The first component is a carbodiimide compound represented by the following formula (I). The first component may be a single carbodiimide compound represented by formula (I), or it may be a combination of two or more carbodiimide compounds represented by formula (I). [ka] (I) In formula (I), R 11 and R 12 Each of these independently represents either a hydrocarbon group having 1 to 12 carbon atoms, or a trialkylsilyl group having 3 to 18 carbon atoms.

[0019] In this specification, the term "hydrocarbon group" is not limited to aliphatic hydrocarbon groups having a linear structure, but may also include branched structures, cyclic structures, carbon-carbon unsaturated bond structures (carbon-carbon double bond structures and carbon-carbon triple bond structures), and any combination thereof. In this specification, the term "hydrocarbon group" is a concept that includes any of the following groups: (acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups. In this specification, the term "hydrocarbon group" naturally includes alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and the like.

[0020] R 11 and R 12 When the hydrocarbon group is present, the lower limit of the number of carbon atoms in the hydrocarbon group is preferably 2 or more, more preferably 3 or more. The upper limit of the number of carbon atoms in the hydrocarbon group is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.

[0021] In this specification, a "trialkylsilyl group having 3 to 15 carbon atoms" is a group in which three hydrocarbon groups are bonded to a silicon atom, as represented by -SiR3 (where R represents a hydrocarbon group), and the carbon number represents the total number of carbon atoms in the three hydrocarbon groups.

[0022] R 11 and R 12 When the group is a trialkylsilyl group, the number of carbon atoms in the hydrocarbon group is preferably 12 or less, more preferably 9 or less, even more preferably 6 or less, and particularly preferably 4 or less.

[0023] R 11 and R 12The hydrocarbon groups include methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), i-propyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)2), and cyclohexyl group (-C6H 11 Examples of hydrocarbon groups include i-propyl group (-CH(CH3)2), cyclohexyl group (-C6H5), trimethylsilyl group (-Si(CH3)3), triethylsilyl group (-Si(CH2CH3)3), etc. Among the above, examples of hydrocarbon groups include i-propyl group (-CH(CH3)2), cyclohexyl group (-C6H 11 ), and a trimethylsilyl group (-Si(CH3)3) are preferred.

[0024] The following are specific examples of carbodiimide compounds represented by formula (I): N,N'-di-i-propylcarbodiimide represented by formula (I-1), N,N'-dicyclohexylcarbodiimide represented by formula (I-2), and N,N'-bis(trimethylsilyl)carbodiimide represented by formula (I-3). However, carbodiimide compounds represented by formula (I) are not limited to these.

[0025] [ka]

[0026] The content of the first component is preferably 0.0001% by mass or more and 10.0000% by mass or less, and more preferably 0.0001% by mass or more and 5.0000% by mass or less, based on the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is 100 parts by mass). The lower limit of the above content is preferably 0.0010% by mass or more, and more preferably 0.0100% by mass or more. The upper limit of the above content is preferably 5.0000% by mass or less, more preferably 3.0000% by mass or less, even more preferably 1.0000% by mass or less, and particularly preferably 0.5000% by mass or less. When the content of the first component is within the above range, the increase in resistance after high-temperature storage becomes more easily suppressed.

[0027] [Second component] The second component is at least one selected from the group consisting of a phosphate represented by formula (II), a cyclic carbonate compound represented by formula (III), a cyclic sulfonic acid ester compound represented by formula (IV), and an isocyanate compound represented by formula (V).

[0028] [ka]

[0029] In formula (I), R 11 and R 12 Each of these independently represents either a hydrocarbon group having 1 to 12 carbon atoms, or a trialkylsilyl group having 3 to 18 carbon atoms. In formula (II), R 21 Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent; each independently represents a halogen group; a represents an integer from 1 to 3; b represents 4 when a is 1, 2 when a is 2, and 0 when a is 3; and c represents an integer from 1 to 3. In formula (III), R 31 Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, and h represents an integer from 1 to 4. In formula (IV), R 41 Each of these independently represents a C1-C12 hydrocarbon group which may contain a halogen group, a C1-C12 fluorine carbide group which may contain an oxa group (-O-) as a substituent, or a C1-C12 hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and i represents an integer from 0 to 4. In formula (V), R 51 This represents a C1-C24 j+1 valent hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and j represents an integer from 0 to 4.

[0030] The second component may contain any one of the above groups, or it may contain two or more of the above groups.

[0031] The second component is more preferably composed of at least one of a phosphate represented by formula (II) and an isocyanate compound represented by formula (V), from the viewpoint of further suppressing the increase in resistance after storage at high temperatures.

[0032] The total content of the second component is preferably 0.0001% by mass or more and 10.0000% by mass or less, and more preferably 0.0001% by mass or more and 5.0000% by mass or less, based on the total amount of the non-aqueous electrolyte (when the total amount of the non-aqueous electrolyte is 100 parts by mass). The lower limit of the total content is preferably 0.001% by mass or more, and more preferably 0.01% by mass or more. The upper limit of the total content is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. When the content of the second component is within the above range, the increase in resistance after high-temperature storage becomes more easily suppressed.

[0033] (Phosphate represented by formula (II)) In one embodiment, the second component preferably contains a phosphate represented by the following formula (II).

[0034] [ka] In formula (II), R 21Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent; each independently represents a halogen group; a represents an integer from 1 to 3; b represents 4 when a is 1, 2 when a is 2, and 0 when a is 3; and c represents an integer from 1 to 3.

[0035] The phosphate represented by formula (II) may be used alone or in combination of two or more types.

[0036] In this specification, "single bond (-)" means R 21 This means that the carbonyl groups (C=O) at both ends are directly bonded, forming an oxalate ligand (oxalate ion ligand). In formula (II), "divalent hydrocarbon group" means a hydrocarbon group having two bond positions, and is not limited to aliphatic hydrocarbon groups having a linear structure, but may 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). In formula (II), the term "hydrocarbon group" is a concept that includes any of the following: (acyclic) aliphatic hydrocarbon groups, monocyclic aliphatic hydrocarbon groups, polycyclic aliphatic hydrocarbon groups, monocyclic aromatic hydrocarbon groups, and polycyclic aromatic hydrocarbon groups. In formula (II), the term "hydrocarbon group" includes alkylene groups, alkenylene groups, alkynylene groups, arylene groups, etc., all of which are included in the concept of "divalent hydrocarbon groups." In formula (II), "may contain at least one functional group selected from the group consisting of halogen groups and oxa groups (-O-) as substituents" means that the hydrogen atoms of the hydrocarbon group may be substituted with halogen groups such as fluoro groups (-F), chloro groups (-Cl), bromo groups (-Br), and iodo groups (-I), and furthermore, the carbon atoms of the hydrocarbon group may be substituted with oxa groups (-O-).

[0037] R 21When the group is a hydrocarbon group, the number of carbon atoms is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less.

[0038] R 21 Examples include single bonds (-), methylene groups (-CH2-), ethylene groups (-CH2CH2-), and n-propylene groups (-CH2CH2CH2-). Among these, single bonds (-) are preferred.

[0039] Each of the X groups independently represents a "halogeno group," specifically including a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I). Among these, the fluoro group (-F) is preferred as the halogeno group.

[0040] a represents an integer between 1 and 3, b represents 4 when a is 1, 2 when a is 2, and 0 when a is 3, and c represents an integer between 1 and 3. It is preferable that a is 1, b is 4, and c is 1.

[0041] Below are specific examples of phosphates represented by formula (II), namely lithium tetrafluorooxalate phosphate (LiTFOP), represented by formula (II-1), and lithium difluorobis(oxalate) phosphate (LiDFBOP), represented by formula (II-2). However, phosphates represented by formula (II) are not limited to these.

[0042] [ka]

[0043] (Cyclic carbonate compound represented by formula (III)) In one embodiment, the second component preferably contains a cyclic carbonate compound represented by the following formula (III).

[0044] [ka]

[0045] In formula (III), R 31 Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, and h represents an integer from 1 to 4.

[0046] The cyclic carbonate compound represented by formula (III) may be used alone or in combination of two or more types.

[0047] In formula (III), R 31 These terms independently represent either "a fluorine carbide 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 a fluoro group (-F) and an oxa group (-O-) as a substituent." However, "fluorine carbide group" refers to a hydrocarbon group in which all hydrogen atoms are replaced by fluorine atoms. In formula (III), the "fluorinated carbide group" may also be called a "fluorinated hydrocarbon group" or "fluorinated carbon group," and the concept includes perfluoroalkyl groups. Furthermore, the fluorinated carbide group is not limited to a linear structure, but may also be a fluorinated carbide group having at least one structure selected from the group consisting of a branched structure, a cyclic structure, and a carbon-carbon unsaturated bond structure (carbon-carbon double bond structure and carbon-carbon triple bond structure).

[0048] In formula (III), the definitions of "hydrocarbon group" and "may include at least one functional group selected from the group consisting of halogen groups and oxa groups (-O-) as substituents" are the same as those stated for the phosphate represented by formula (II) above.

[0049] In formula (III), R 31A preferred embodiment of the hydrocarbon group represented by is R in the phosphate represented by the aforementioned formula (II). 21 This is similar to the preferred embodiment for the hydrocarbon group represented by .

[0050] R 31 When R is a fluorine carbide 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. 31 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.

[0051] R 31 These include trifluoromethyl group (-CF3), pentafluoroethyl group (-C2F5), n-heptafluoropropyl group (-C3F7), pentafluorophenyl group (-C6F5), trifluoromethoxy group (-OCF3), pentafluoroethoxy group (-OC2F5), n-heptafluoropropoxy group (-OC3F7), pentafluorophenoxy group (-OC6F5), fluoromethyl group (-CH2F), difluoromethyl group (-CHF2), and 2,2,2-trifluoromethyl group. Roethyl group (-CH2CF3), p-fluorophenyl group (-C6H4F), methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), i-propyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)2), hexyl group (-CH2CH2CH2CH2CH2CH3), cyclohexyl group (-C6H 11 Examples include phenyl groups (-C6H5), fluorophenyl groups (-C6H4F), trifluoromethylphenyl groups (-C6H4CF3), and trifluoromethoxyphenyl groups (-C6H4OCF3). Among these, the trifluoromethyl group (-CF3) is preferred.

[0052] h represents an integer between 1 and 4, but it is preferably 1.

[0053] The following are specific examples of cyclic carbonate compounds represented by formula (III): trifluoropropylene carbonate (TFPC) represented by formula (III-1), a cyclic carbonate compound represented by formula (III-2), and a cyclic carbonate compound represented by formula (III-2). However, the cyclic carbonate compounds represented by formula (III) are not limited to these.

[0054] [ka]

[0055] (Cyclic sulfonic acid ester compounds represented by formula (IV)) In one embodiment, the second component preferably contains a cyclic sulfonic acid ester compound represented by the following formula (IV).

[0056] [ka] In formula (IV), R 41 Each of these independently represents a C1-C12 hydrocarbon group which may contain a halogen group, a C1-C12 fluorine carbide group which may contain an oxa group (-O-) as a substituent, or a C1-C12 hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and i represents an integer from 0 to 4.

[0057] The cyclic sulfonic acid ester compounds represented by formula (IV) may be used alone or in combination of two or more.

[0058] In formula (IV), the definition of "fluorine carbide group" is the same as that given for the cyclic carbonate compound represented by formula (III) above. In formula (IV), the definition of "may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent" is the same as that stated for the phosphate represented by formula (II) above.

[0059] R 41 When R is a fluorine carbide 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. 41 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.

[0060] R 41 These include fluoro group (-F), trifluoromethyl group (-CF3), pentafluoroethyl group (-C2F5), n-heptafluoropropyl group (-C3F7), pentafluorophenyl group (-C6F5), trifluoromethoxy group (-OCF3), pentafluoroethoxy group (-OC2F5), n-heptafluoropropoxy group (-OC3F7), pentafluorophenoxy group (-OC6F5), fluoromethyl group (-CH2F), difluoromethyl group (-CHF2), and 2,2,2- Trifluoroethyl group (-CH2CF3), p-fluorophenyl group (-C6H4F), methyl group (-CH3), ethyl group (-CH2CH3), vinyl group (-CH=CH2), n-propyl group (-CH2CH2CH3), i-propyl group (-CH(CH3)2), n-butyl group (-CH2CH2CH2CH3), s-butyl group (-CH2CH(CH3)2), t-butyl group (-C(CH3)2), hexyl group (-CH2CH2CH2CH2CH2CH3), cyclohexyl group (-C6H 11 Examples include phenyl groups (-C6H5), fluorophenyl groups (-C6H4F), trifluoromethylphenyl groups (-C6H4CF3), and trifluoromethoxyphenyl groups (-C6H4OCF3). Among these, the fluoro group (-F) and the trifluoromethyl group (-CF3) are preferred.

[0061] i represents an integer between 0 and 4, but it is preferably 0 or 1.

[0062] The following are specific examples of cyclic sulfonic acid ester compounds represented by formula (IV): 1-propene-1,3-sultone (PRS) represented by formula (IV-1), a sultone compound represented by formula (IV-2), a sultone compound represented by formula (IV-3), and a sultone compound represented by formula (IV-4). However, cyclic sulfonic acid ester compounds represented by formula (IV) are not limited to these.

[0063] [ka]

[0064] (Isocyanate compounds represented by formula (V)) In one embodiment, the second component preferably contains an isocyanate compound represented by the following formula (V). [ka] In formula (V), R 51 This represents a C1-C24 j+1 valent hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and j represents an integer from 0 to 4.

[0065] The isocyanate compound represented by formula (V) may be used alone or in combination of two or more types.

[0066] In formula (V), "j+1 valent hydrocarbon group" means a hydrocarbon group having j+1 bond positions. The hydrocarbon group 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 formula (V), "may contain at least one functional group selected from the group consisting of halogen groups and oxa groups (-O-) as substituents" means that the hydrogen atoms of the hydrocarbon group may be substituted with fluoro groups (-F), chloro groups (-Cl), bromo groups (-Br), iodo groups (-I), etc., and furthermore, the carbon atoms of the hydrocarbon group may be substituted with oxa groups (-O-). In formula (V), j represents an integer from 0 to 4, which means that the isocyanate compound represented by formula (V) is a compound having 1 to 5 isocyanate groups, such as a monoisocyanate compound, diisocyanate compound, or triisocyanate compound.

[0067] R 51 The number of carbon atoms in the hydrocarbon group is preferably 20 or less, more preferably 16 or less, even more preferably 12 or less, and particularly preferably 10 or less.

[0068] R 51 Examples include methylene group (-CH2-), ethylene group (-CH2CH2CH2-), n-propylene group (-CH2CH2CH2-), n-butylene group (-CH2CH2CH2CH2-), n-pentylene group (-CH2CH2CH2CH2CH2-), methylene group (-CH2-), phenylene group (-C6H4-), and others.

[0069] j represents an integer between 1 and 4, but it is preferably 1.

[0070] The following are specific examples of isocyanate compounds represented by formula (V): isocyanate compounds represented by formula (V-1), formula (V-2), formula (V-3), formula (V-4), formula (V-5), formula (V-6), formula (V-7), and formula (V-8). However, cyclic sulfonic acid ester compounds represented by formula (IV) are not limited to these. [ka]

[0071] [Non-aqueous solvent] The non-aqueous electrolyte preferably further contains a non-aqueous solvent in addition to the first and second components. Various known non-aqueous solvents can be appropriately selected. The non-aqueous solvent may be used alone or in combination of two or more.

[0072] 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.

[0073] 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.

[0074] Among the above, it is preferable that the non-aqueous solvent includes at least one selected from the group consisting of cyclic carbonates, linear carbonates, aliphatic carboxylic acid esters, cyclic ethers, linear ethers, nitriles, amides, and lactams.

[0075] The non-aqueous solvent more preferably contains at least one selected from the group consisting of cyclic carbonates, fluorine-containing cyclic carbonates, linear carbonates, and fluorine-containing linear carbonates. In this case, the total proportion of cyclic carbonates, fluorinated cyclic carbonates, linear carbonates, and fluorinated linear carbonates is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, relative to the total amount of the non-aqueous solvent.

[0076] The non-aqueous solvent is more preferably at least one selected from the group consisting of cyclic carbonates and linear carbonates. In this case, the total proportion of cyclic carbonates and linear carbonates in the non-aqueous solvent is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 80% by mass or more and 100% by mass or less, relative to the total amount of the non-aqueous solvent.

[0077] The upper limit of the non-aqueous solvent content is preferably 99% by mass or less, preferably 97% by mass or less, and more preferably 90% by mass or less, 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.

[0078] 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.

[0079] [Electrolyte] The non-aqueous electrolyte preferably contains an electrolyte in addition to the first and second components. Various known electrolytes can be appropriately selected. The electrolyte may be used alone or in combination of two or more.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] <Nonaqueous electrolyte secondary battery> The non-aqueous electrolyte secondary battery of this disclosure comprises a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of this disclosure. The non-aqueous electrolyte secondary battery in this disclosure may further include a case for housing a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, as necessary. The following provides a detailed explanation of the positive electrode, negative electrode, separator, case, etc.

[0088] [Positive electrode] The positive electrode can be manufactured by dispersing a positive electrode active material, a binder, and optionally a conductive additive and a thickener in a solvent to form a slurry, and then applying this slurry to a current collector, drying it, and compressing it to form a positive electrode composite layer (also called the "positive electrode active material layer") on the current collector.

[0089] As for the positive electrode active material, 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(x, y, and z are each independently greater than 0 and less than 1.00, and the sum of x, y, and z is between 0.99 and 1.00.) (so-called "NCM"; for example, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiLiLi 0.5 Co 0.3 Mn 0.2 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 O2, LiLiLi 0.6 Co 0.2 Mn 0.2 O2, LiLiLi 0.8 Co 0.1 Mn 0.1 Composite oxides consisting of lithium and transition metals, such as O2; Li t Ni 1-x-y Cox Al y O2 (t is 0.95 or more and 1.15 or less, x is 0 or more and 0.3 or less, y is 0.1 or more and 0.2 or less, and the sum of x and y is less than 0.5.) (so-called "NCA"; for example, LiNi 0.8 Co 0.15 Al 0.05 O2), etc., composite oxides composed of lithium, transition metals, and typical metals; Conductive polymer materials such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole, polyaniline composites, etc.; Lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium manganese iron phosphate (LiMn x Fe 1-x PO4; 0 < x < 1), lithium cobalt phosphate (LiCoPO4), lithium nickel phosphate (LiNiPO4), etc., lithium metal phosphates; etc. can be mentioned.

[0090] Examples of the binder for the positive electrode include polyvinylidene fluoride, etc. Examples of the conductive assistant for the positive electrode include carbon black (for example, acetylene black), amorphous whiskers, graphite, etc. Examples of the thickening agent for the positive electrode include carboxymethyl cellulose, etc. In addition, examples of the solvent for the slurry for forming the positive electrode include organic solvents such as N-methylpyrrolidone.

[0091] The total content of the positive electrode active material in the positive electrode mixture layer is usually 70% to 97% by mass, preferably 75% or more and preferably 95% or less when the total content of the positive electrode mixture layer is 100% by mass.

[0092] Examples of the material for the current collector of the positive electrode include aluminum, aluminum alloy, stainless steel, nickel, titanium, tantalum, carbon cloth, carbon paper, etc.

[0093] 〔Negative electrode〕 The negative electrode can be manufactured by dispersing a negative electrode active material, a binder, and optionally a conductive additive and a thickener in a solvent to form a slurry, applying this slurry to a current collector, drying it, and compressing it to form a negative electrode composite layer (also called the "negative electrode active material layer") on the current collector.

[0094] The elements or compounds that serve as the negative electrode active material can be classified into (1) elemental carbon and carbon compounds that can be doped / dedoped with lithium ions, (2) metals and alloys that can be alloyed with lithium, and (3) oxides, nitrides, and carbides that can be doped / dedoped with lithium ions. When the negative electrode active material is elemental silicon, a particulate (powdered) elemental or compound is usually used. Furthermore, the negative electrode active material used is not limited to one type, but may be a mixture of two or more types.

[0095] The negative electrode active material preferably contains elemental carbon particles and at least one selected from the group consisting of elemental silicon particles, silicon oxide particles, and silicon carbide particles. Examples of elemental carbon particles include graphite (natural graphite, artificial graphite) particles, carbon black particles, activated carbon particles, and amorphous carbon particles. Examples of artificial graphite include graphitized MCMB and graphitized MCF. Examples of amorphous carbon materials include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500°C or below, and mesophase pitch carbon fiber (MCF).

[0096] When the element or compound that serves as the negative electrode active material is in the form of particles (powder), its specific shape may include fibrous, spherical, potato-shaped, or flake-shaped.

[0097] When the negative electrode active material contains elemental carbon particles, the median diameter D50 of the elemental carbon is typically 1 μm to 30 μm, preferably 10 μm or more, more preferably 15 μm or more, preferably 25 μm or less, and more preferably 20 μm or less.

[0098] When the negative electrode active material contains elemental carbon particles, the BET specific surface area of ​​elemental carbon is typically 1.0 m². 2 / g~5.0m2 / g, preferably 2.0 m 2 / g or more, more preferably 3.0 m 2 / g or more, preferably 4.5 m 2 / g or less, more preferably 4.0 m 2 / g or less.

[0099] Silicon oxide can be represented by SiO x where x is a variable, that is, the oxygen atom content in silicon oxide is not particularly limited, but x is usually 0 ≦ x < 2, preferably 0.2 or more, more preferably 0.4 or more, still more preferably 0.6 or more, preferably 1.8 or less, more preferably 1.6 or less, still more preferably 1.4 or less.

[0100] The median diameter D50 of elemental silicon particles, silicon oxide particles, or silicon carbide particles is usually 0.5 μm to 20 μm, preferably 1.0 μm or more, more preferably 3.0 μm or more, preferably 15 μm or less, more preferably 10 μm or less.

[0101] The BET specific surface area of elemental silicon particles, silicon oxide particles, or silicon carbide particles is usually 1.0 m 2 / g to 5.0 m 2 / g, preferably 1.5 m 2 / g or more, more preferably 2.0 m 2 / g or more, preferably 4.5 m 2 / g or less, more preferably 4.0 m 2 / g or less.

[0102] When the negative electrode active material contains at least one selected from the group consisting of elemental carbon particles and at least one of elemental silicon particles, silicon oxide particles, and silicon carbide particles, the total charged mass of the elemental silicon particles, silicon oxide particles, and silicon carbide particles in the negative electrode active material is usually 1% by mass to 20% by mass when the total charged mass of the entire negative electrode active material is 100% by mass, preferably 3% by mass or more, more preferably 5% by mass or more, preferably 18% by mass or less, more preferably 15% by mass or less.

[0103] When the negative electrode active material includes elemental carbon particles and at least one selected from the group consisting of elemental silicon particles, silicon oxide particles, and silicon carbide particles, the total mass of elemental carbon particles in the negative electrode active material is usually 70% to 99% by mass, but preferably 80% or more by mass, preferably 95% or less by mass, and more preferably 90% or less by mass, when the total mass of the entire negative electrode active material is taken as 100% by mass. When the total mass of elemental silicon particles, etc., is within the above range, it becomes easier to ensure a balance between the energy density and capacity retention rate of the lithium-ion secondary battery.

[0104] The total content of the negative electrode active material in the negative electrode composite layer is usually 70% to 99.5% by mass, but preferably 75% or more by mass, and preferably 99% or less by mass, when the entire negative electrode composite layer is considered to be 100% by mass.

[0105] Examples of binders for the negative electrode include styrene-butadiene rubber (SBR). The total content of the copolymer binder in the negative electrode composite layer is usually 0.1% to 5% by mass, but preferably 0.5% or more by mass, more preferably 1.0% or more by mass, preferably 3% or less by mass, and more preferably 2% or less by mass, when the entire negative electrode composite layer is considered as 100% by mass.

[0106] The negative electrode composite layer preferably further 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.

[0107] The total content of the conductive additive in the negative electrode composite layer is usually 0.01% to 3% by mass, when the entire negative electrode composite layer is considered as 100% by mass, but is preferably 0.05% or more by mass, more preferably 0.1% or more by mass, preferably 2% or less by mass, and more preferably 1% or less by mass.

[0108] The negative electrode composite layer preferably further contains a thickening agent. Including a thickening agent makes it easier to adjust the viscosity of the slurry and improves productivity. Examples of thickening agents for the negative electrode include cellulose derivatives such as carboxymethylcellulose (CMC), carboxyethylcellulose, and hydroxyethylcellulose, polyoxyethylene and its modified forms, polyvinyl alcohol and its modified forms, and polysaccharides.

[0109] The total content of the thickening agent in the negative electrode composite layer is usually 0.1% to 5% by mass, when the entire negative electrode composite layer is considered as 100% by mass, but is preferably 0.5% or more by mass, more preferably 1.0% or more by mass, preferably 3% or less by mass, and more preferably 2% or less by mass.

[0110] 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.

[0111] Examples of materials for the negative electrode current collector include copper, nickel, stainless steel, and nickel-plated steel.

[0112] [Separator] Examples of separators include porous resin plates. Materials for the porous resin plates include resin and nonwoven fabrics containing this resin. Examples of resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, and polyamide. Among these, 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.

[0113] 〔case〕 The shape of the case is not particularly limited and can be appropriately selected depending on the application of the non-aqueous electrolyte 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.

[0114] [Specific examples of non-aqueous electrolyte secondary battery precursors] Figure 1 is a schematic cross-sectional view showing a stacked non-aqueous electrolyte secondary battery precursor, which is an example of a non-aqueous electrolyte secondary battery precursor of this disclosure. As shown in Figure 1, the non-aqueous electrolyte secondary battery precursor 1 is a stacked battery precursor. In detail, in the non-aqueous electrolyte secondary battery precursor 1, the battery element 10 is enclosed inside an 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.

[0115] 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.

[0116] The non-aqueous electrolyte of this disclosure is injected into the interior of the outer casing 30 of the non-aqueous electrolyte 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 non-aqueous electrolyte 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 by having the active material layers on one side of each current collector.

[0117] The non-aqueous electrolyte secondary battery precursor 1 is a stacked type non-aqueous electrolyte secondary battery precursor, but the non-aqueous electrolyte secondary battery precursor of this disclosure is not limited to this, and may be, for example, a wound type non-aqueous electrolyte secondary battery precursor. The wound type non-aqueous electrolyte 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 type non-aqueous electrolyte secondary battery precursor includes cylindrical non-aqueous electrolyte secondary battery precursors and prismatic non-aqueous electrolyte secondary battery precursors.

[0118] As shown in Figure 1, in the non-aqueous electrolyte 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 casing 30 are opposite to the 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 casing 30 is the same direction with respect to the casing 30.

[0119] An example of the non-aqueous electrolyte secondary battery of this disclosure, described later, is a lithium secondary battery obtained by subjecting a non-aqueous electrolyte secondary battery precursor 1 to charging and discharging.

[0120] Figure 2 is a schematic cross-sectional view showing a coin-shaped non-aqueous electrolyte secondary battery precursor, which is another example of a non-aqueous electrolyte secondary battery precursor of the present disclosure.

[0121] In the coin-shaped non-aqueous electrolyte secondary battery precursor shown in Figure 2, a disc-shaped negative electrode 42, a separator 45 into which non-aqueous electrolyte has been injected, 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.

[0122] 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 non-aqueous electrolyte secondary battery precursor shown in Figure 2.

[0123] [Method of manufacturing lithium secondary batteries] The method for manufacturing a lithium secondary battery described herein is not particularly limited, but for example, The process of preparing the non-aqueous electrolyte secondary battery precursor described above (hereinafter also referred to as the "preparation process"), The above non-aqueous electrolyte secondary battery precursor is subjected to a charging and discharging process, The manufacturing method may include the following: The lithium secondary battery of this disclosure is a lithium secondary battery obtained by subjecting the non-aqueous electrolyte secondary battery precursor of this disclosure described above to charging and discharging.

[0124] 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.

[0125] The preparation step may simply be a step of preparing a pre-manufactured non-aqueous electrolyte secondary battery precursor of the present disclosure for use in the charging and discharging process, or it may be a step of manufacturing the non-aqueous electrolyte secondary battery precursor of the present disclosure. The non-aqueous electrolyte secondary battery precursor is as described above.

[0126] In the charging and discharging process, the charging and discharging of the non-aqueous electrolyte secondary battery precursor can be carried out according to known methods. In this process, the non-aqueous electrolyte 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) in the non-aqueous electrolyte secondary battery precursor.

[0127] The charging and discharging process preferably involves performing a combination of charging and discharging one or more times on the non-aqueous electrolyte secondary battery precursor in an environment of 25°C to 70°C. [Examples]

[0128] The following are examples of the embodiments of this disclosure, but this disclosure is limited to the following embodiments. In the following, "%" refers to "mass%" unless otherwise specified.

[0129] [Example 1] <Preparation of non-aqueous electrolyte> Ethylene carbonate (hereinafter sometimes abbreviated as "EC"), dimethyl carbonate (hereinafter sometimes abbreviated as "DMC"), and ethyl methyl carbonate (hereinafter sometimes abbreviated 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. LiPF6 was dissolved in the resulting mixed solvent as an electrolyte to a final concentration of 1 mol / L in the resulting non-aqueous electrolyte, thereby obtaining the electrolyte (hereinafter sometimes abbreviated as "basic electrolyte"). To the obtained basic electrolyte, N,N'-di-i-propylcarbodiimide represented by the following formula (I-1) and lithium tetrafluorooxalate phosphate (LiTFOP) represented by the following formula (II-1) were added so that their respective content relative to the total amount of non-aqueous electrolyte obtained (values ​​when the total amount of non-aqueous electrolyte is considered as 100% by mass) were as shown in Table 1, thereby obtaining a non-aqueous electrolyte.

[0130] [ka]

[0131] [ka]

[0132] <Fabrication of the positive electrode> Li(Ni) is used as the positive electrode active material.0.8 Co 0.1 Mn 0.1 A mixture was obtained by adding 94% by mass of O2, carbon black (3% by mass) as a conductive additive, and polyvinylidene fluoride (PVdF) (3% by mass) as a binder. The obtained mixture was dispersed in N-methylpyrrolidone solvent to obtain a cathode composite slurry. A 20 μm thick aluminum foil was prepared as the positive electrode current collector. The obtained positive electrode slurry was applied onto aluminum foil, dried, and then rolled in a press to obtain a sheet-like positive electrode. The positive electrode consists of a positive electrode current collector and a positive electrode active material layer.

[0133] <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.

[0134] <Preparing the separator> A porous polyethylene film was prepared as a separator.

[0135] <Preparation of non-aqueous electrolyte secondary battery precursors> The negative electrode was punched out in a disc shape with a diameter of 14 mm, the positive electrode in a disc shape with a diameter of 13 mm, and the separator in a disc shape with a diameter of 17 mm. This resulted in coin-shaped negative electrodes, coin-shaped positive electrodes, and coin-shaped separators. The obtained coin-shaped negative electrode, coin-shaped separator, and coin-shaped positive electrode were stacked in this order inside a stainless steel battery case (size: 2032). Next, 20 μL of non-aqueous electrolyte was poured into the battery case, immersing the separator, positive electrode, and negative electrode in the non-aqueous electrolyte. Next, an aluminum plate (1.2 mm thick, 16 mm in diameter) and a spring were placed on the positive electrode, and the battery was sealed by crimping the battery can lid via a polypropylene gasket. Based on the above, a coin-shaped non-aqueous electrolyte 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 non-aqueous electrolyte secondary battery precursor was 20 mm in diameter and 3.2 mm in height.

[0136] <Manufacturing of lithium-ion secondary batteries> The lithium-ion secondary battery precursor was subjected to the following processes in order: charging from 1.5V to 4.2V, holding for 5 to 50 hours, charging to 4.2V, and discharging to 2.5V, all within a temperature range of 25°C to 70°C, to obtain a lithium-ion secondary battery.

[0137] <Evaluation of initial room temperature resistance> The lithium-ion secondary battery of Example 1 was charged to 3.7V, then cooled to -10°C in a constant temperature bath, and the DC resistance [Ω] as the initial room temperature resistance value (25°C) was measured based on the voltage drop (= voltage before discharge start - voltage 10 seconds after discharge start) and the current value (i.e., the current value corresponding to the discharge rates of 0.1C to 0.6C) for each discharge rate of 0.1C to 0.6C due to "CC10s discharge". The initial room temperature resistance (25°C) of Comparative Example 1, described later, was measured using the same procedure. Then, the relative value of the initial room temperature resistance (25°C) of Example 1 was calculated, with the initial room temperature resistance (25°C) of the lithium-ion secondary battery of Comparative Example 1 set to 100, and this was defined as the "initial room temperature resistance (relative value)".

[0138] <Evaluation of room temperature resistance after high-temperature storage> Next, the lithium-ion secondary battery, after the initial low-temperature resistance measurement, was charged to 4.2V, and the charged lithium-ion secondary battery was stored in a constant temperature bath at 60°C for 14 days (hereinafter sometimes referred to as "high-temperature storage"). Then, the resistance value of the lithium-ion secondary battery at room temperature (25°C) after high-temperature storage was measured using the same method as the initial room-temperature resistance value. Similarly, for Comparative Example 1, described later, the resistance value of the lithium-ion secondary battery at room temperature (25°C) after high-temperature storage was measured. Based on the above results, the relative value of the room temperature resistance (25°C) of the lithium-ion secondary battery in Example 1 after high-temperature storage was calculated, with the room temperature resistance (25°C) of the lithium-ion secondary battery in Comparative Example 1 after high-temperature storage set to 100, and this was defined as the "Room Temperature Resistance (Relative Value) after High-Temperature Storage". The results are shown in Table 1 under the item "Evaluation after High-Temperature Storage" in the [Discharge DC Resistance] column at 25°C.

[0139] <Evaluation of initial low-temperature resistance> The lithium-ion secondary battery of Example 1 was charged to 3.7V, then cooled to -10°C in a constant temperature bath, and the DC resistance [Ω] as the initial low-temperature resistance value (-10°C) was measured based on the voltage drop (=voltage before discharge start - voltage 10 seconds after discharge start) and the current value (i.e., the current value corresponding to the discharge rates of 0.1C to 0.6C) for each discharge rate of 0.1C to 0.6C due to "CC10s discharge". For Comparative Example 1, described later, the initial low-temperature resistance value (-10°C) was measured using the same procedure, and the relative value of the initial low-temperature resistance value (-10°C) of Example 1 was calculated, with the initial low-temperature resistance value (-10°C) of the lithium-ion secondary battery of Comparative Example 1 set to 100, and this was referred to as the "initial low-temperature resistance value (relative value)".

[0140] <Evaluation of low-temperature resistance after high-temperature storage> Next, the lithium-ion secondary battery, after the initial low-temperature resistance measurement, was charged to 4.2V, and the charged lithium-ion secondary battery was stored in a constant temperature bath at 60°C for 14 days (hereinafter sometimes referred to as "high-temperature storage"). Then, the low-temperature resistance (-10°C) of the lithium-ion secondary battery after high-temperature storage was measured using the same method as the initial low-temperature resistance (-10°C). Similarly, the low-temperature resistance value (-10°C) of the lithium-ion secondary battery after high-temperature storage was measured for Comparative Example 1, described later. Based on the above results, the relative value of the low-temperature resistance (-10°C) of the lithium-ion secondary battery in Example 1 after high-temperature storage was calculated, with the low-temperature resistance (-10°C) of the lithium-ion secondary battery in Comparative Example 1 after high-temperature storage set to 100, and this was defined as the "low-temperature resistance (relative value) after high-temperature storage". The results are shown in the [Discharge DC Resistance] at -10°C in the "Evaluation after high-temperature storage" section of Table 1.

[0141] [Comparative Example 1] Non-aqueous electrolytes and lithium-ion secondary batteries were prepared by the same procedure as described in Example 1, except that N,N'-di-i-propylcarbodiimide represented by formula (I-1) and lithium tetrafluorooxalate phosphate (LiTFOP) represented by formula (II-1) were not added. Furthermore, the initial low-temperature resistance value (-10°C) and the low-temperature resistance value of the lithium-ion secondary battery after high-temperature storage (-10°C) were measured by the same procedure as described in Example 1, and these were used as reference values ​​for the "initial low-temperature resistance value (relative value)" and "low-temperature resistance value after high-temperature storage (relative value)" in Examples and Comparative Examples 2-3.

[0142] [Examples 2-4 and Comparative Examples 2-3] The procedure was the same as in Example 1, except that the type and content of additives used in the preparation of the non-aqueous electrolyte were changed as shown in Table 1. The results are shown in Table 1. The additives shown in Table 1 are N,N'-di-i-propylcarbodiimide represented by formula (I-1) below, lithium tetrafluorooxalate phosphate (LiTFOP) represented by formula (II-1) below, trifluoropropylene carbonate (TFPC) represented by formula (III-1) below, 1-propene-1,3-sultone (PRS) represented by formula (IV-1) below, and an isocyanate compound represented by formula (V-1) below.

[0143] [ka]

[0144] In the table, item [(I-1)] represents the content of the carbodiimide compound represented by formula (I-1) relative to the total amount of non-aqueous electrolyte. In the table, item [(II-1)] represents the content of the phosphate represented by formula (II-1) relative to the total volume of the non-aqueous electrolyte. In the table, item [(III-1)] represents the content of the cyclic carbonate compound represented by formula (III-1) relative to the total amount of non-aqueous electrolyte. In the table, item [(IV-1)] represents the content of the cyclic sulfonic acid ester compound represented by formula (IV-1) relative to the total amount of non-aqueous electrolyte. In the table, item [(V-1)] represents the content of the isocyanate compound represented by formula (V-1) relative to the total amount of non-aqueous electrolyte.

[0145] [Table 1]

[0146] As is clear from Table 1, the battery equipped with the non-aqueous electrolyte of the example can suppress the increase in resistance after long-term storage at high temperatures compared to the battery equipped with the non-aqueous electrolyte of the comparative example. Furthermore, the battery equipped with the non-aqueous electrolyte of the example can also improve the suppression of initial resistance and the decrease in capacity retention rate after storage at high temperatures. [Explanation of symbols]

[0147] 1 Nonaqueous electrolyte secondary battery precursor 10 Battery elements 11 Positive electrode 11A positive electrode current collector 11B Positive electrode composite layer 12 Negative electrode 12 12A negative electrode current collector 12B Negative electrode composite layer 13 Separator 14 single cell layers 21 Positive lead 22 Negative lead 30 Exterior

[0148] 42 Disc-shaped negative electrode 45 Separator 41 Disc-shaped positive electrode 47 Spacer plate 48 Spacer plate 43 Positive electrode can 43 (also called battery can) 44. Sealing plate 44 (also called battery can cover) 43 Positive electrode can 44 Sealing plate 46 Gasket

Claims

1. A first component selected from the group consisting of carbodiimide compounds represented by the following formula (I), A second component selected from the group consisting of a phosphate represented by the following formula (II), a cyclic carbonate compound represented by the following formula (III), a cyclic sulfonic acid ester compound represented by the following formula (IV), and an isocyanate compound represented by the following formula (V), A non-aqueous electrolyte containing [a specific component]. 【Chemistry 1】 (In formula (I), R １１ and R １２ Each of these independently represents either a hydrocarbon group having 1 to 12 carbon atoms, or a trialkylsilyl group having 3 to 18 carbon atoms. In formula (II), R ２１ Each independently represents a divalent hydrocarbon group having 1 to 6 carbon atoms, which may contain a single bond or at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent; each independently represents a halogen group; a represents an integer from 1 to 3; b represents 4 when a is 1, 2 when a is 2, and 0 when a is 3; and c represents an integer from 1 to 3. In formula (III), R ３１ Each of these independently represents a fluorine carbide group having 1 to 12 carbon atoms, which may contain an oxa group (-O-) as a substituent, or a hydrocarbon group having 1 to 12 carbon atoms, which may contain at least one functional group selected from the group consisting of a fluoro group (-F) and an oxa group (-O-) as a substituent, and h represents an integer from 1 to 4. In formula (IV), R ４１ Each of these independently represents a C1-C12 hydrocarbon group which may contain a halogen group, a C1-C12 fluorine carbide group which may contain an oxa group (-O-) as a substituent, or a C1-C12 hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and i represents an integer from 0 to 4. In formula (V), R ５１ (where j represents a C1-C24 j+1 valent hydrocarbon group which may contain at least one functional group selected from the group consisting of a halogen group and an oxa group (-O-) as a substituent, and j represents an integer from 0 to 4.)

2. The non-aqueous electrolyte according to claim 1, wherein the total content of the first component is 0.0001% by mass to 5.0000% by mass relative to the total amount of the non-aqueous electrolyte.

3. The non-aqueous electrolyte according to claim 1, wherein the total content of the second component is 0.0001% by mass to 5.0000% by mass relative to the total amount of the non-aqueous electrolyte.

4. It comprises a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte is the non-aqueous electrolyte described in any one of claims 1 to 3.

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