JP7521743B2 - Solvent-soluble polyimide compound, resin composition for producing lithium ion secondary battery negative electrode containing said solvent-soluble polyimide compound, lithium ion secondary battery negative electrode formed using said resin composition for producing lithium ion secondary battery negative electrode, and lithium ion secondary battery equipped with said lithium ion secondary battery negative electrode - Google Patents

Description

The present invention relates to a solvent-soluble polyimide compound, a resin composition for producing a lithium ion secondary battery negative electrode that contains the solvent-soluble polyimide compound, a lithium ion secondary battery negative electrode that is constructed using the resin composition for producing a lithium ion secondary battery negative electrode, and a lithium ion secondary battery that includes the lithium ion secondary battery negative electrode.

In recent years, electronic devices such as smartphones have become increasingly smaller, and this has led to active development of lithium-ion secondary batteries that are small, lightweight, and capable of achieving high energy density.
As the negative electrode active material contained in lithium ion secondary batteries, silicon (Si) materials, which have high discharge capacity and excellent initial charge/discharge efficiency and cycle characteristics, are used. However, silicon expands and contracts significantly during charging and discharging, and repeated use may cause disconnection of the conductive paths between the negative electrode active materials, peeling between the current collector and the negative electrode active material layer, etc.

In light of the problems with silicon materials mentioned above, the use of polyimide compounds as binder resins and materials constituting the negative electrode, instead of the carboxymethyl cellulose and other materials that have been used conventionally, is being considered (see Patent Document 1, etc.).

However, there is room for improvement in the initial charge/discharge efficiency and cycle characteristics, and there is a demand for a polyimide compound that can further improve the initial charge/discharge efficiency and cycle characteristics.

International Publication WO2017/138604 Brochure

The present invention has been made in view of the above problems, and an object of the present invention is to provide a solvent-soluble polyimide compound that can significantly improve the initial charge-discharge efficiency and cycle characteristics of a lithium ion secondary battery.
Another object of the present invention is to provide a resin composition for producing a negative electrode of a lithium ion secondary battery, which contains the solvent-soluble polyimide compound.
Another object of the present invention is to provide a negative electrode for a lithium ion secondary battery which is formed using the resin composition for producing a negative electrode for a lithium ion secondary battery.
Furthermore, the present invention provides a lithium ion secondary battery including the negative electrode for lithium ion secondary batteries.

The solvent-soluble polyimide compound of the present invention is a solvent-soluble polyimide used as an electrode material for a lithium ion secondary battery,
It is a reaction product of a carboxyl group-containing diamine and an acid anhydride,
The elastic modulus is 3.4 GPa or more.

（一般式（１）及び（２）中、Ｒ_１は、単結合又は（ＣＨ_２）_ｐで表され、ｐは１～６の整数であり、ｎ及びｏは、それぞれ、１～５の整数である。） In one embodiment, the carboxyl group-containing diamine compound is represented by the following general formula (1) or (2).

(In general formulas (1) and (2), R ₁ is represented by a single bond or (CH ₂ ) _p , p is an integer of 1 to 6, and n and o are each an integer of 1 to 5.)

In one embodiment, the solvent-soluble polyimide compound of the present invention contains an aromatic diamine compound as a polymerization component.

（一般式（３）中、Ｒ_２～Ｒ_９は、それぞれ独立して、水素、フッ素、置換又は無置換のアルキル基及び置換又は無置換の芳香族基からなる群より選択され、Ｒ_２～Ｒ_９の少なくとも１つが、芳香族基である。） In one embodiment, the solvent-soluble polyimide compound of the present invention contains, as an aromatic diamine compound, a diamine compound represented by the following general formula (3).

(In general formula (3), R ₂ to R ₉ are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R ₂ to R ₉ is an aromatic group.)

In one embodiment, the solvent-soluble polyimide compound of the present invention is a reaction product of (a) a carboxyl group-containing diamine compound, (b) an aromatic diamine compound, and (c) an aromatic acid anhydride.

（一般式（４）中、Ｘは、単結合、炭素数１～６のアルキル基、（ＣＦ_３）_２Ｃ、ＳＯ_２及び酸素原子から選択される。） In one embodiment, the aromatic acid anhydride (c) is represented by the following general formula (4).

(In general formula (4), X is selected from a single bond, an alkyl group having 1 to 6 carbon atoms, (CF ₃ ) ₂ C, SO ₂ , and an oxygen atom.)

In one embodiment, the solvent-soluble polyimide compound of the present invention is a reaction product of (d) a carboxyl group-containing diamine compound and (e) an alicyclic acid anhydride.

The resin composition for producing a negative electrode of a lithium ion secondary battery of the present invention is characterized by containing the above-mentioned solvent-soluble polyimide compound and a negative electrode active material.

The negative electrode for a lithium ion secondary battery of the present invention comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector,
The negative electrode active material layer is characterized by being composed of the above-mentioned resin composition for producing a lithium ion secondary battery negative electrode.

The lithium ion secondary battery of the present invention is characterized by comprising the above-mentioned negative electrode for the lithium ion secondary battery and a positive electrode.

According to the present invention, it is possible to provide a solvent-soluble polyimide compound that can significantly improve the initial charge/discharge efficiency and cycle characteristics of a lithium ion secondary battery.
In addition, it is possible to provide a resin composition for producing a negative electrode of a lithium ion secondary battery, which contains the solvent-soluble polyimide compound.
It is also possible to provide a negative electrode for a lithium ion secondary battery that is formed using the resin composition for producing a negative electrode for a lithium ion secondary battery.
Furthermore, a lithium ion secondary battery including the negative electrode for lithium ion secondary batteries can be provided.

(Solvent-soluble polyimide compound)
The solvent-soluble polyimide compound of the present invention is characterized in that it is a reaction product of a carboxyl group-containing diamine compound and an acid anhydride.
The solvent-soluble polyimide compound of the present invention may be a compound obtained by reacting two or more kinds of carboxyl group-containing diamine compounds and two or more kinds of acid anhydrides.

In the present invention, "solvent-soluble polyimide compound" means a polyimide compound that dissolves in an amount of 5 g or more in 100 g of an organic solvent.

The solvent-soluble polyimide compound of the present invention is characterized in that it has an elastic modulus of 3.4 GPa or more, and more preferably has an elastic modulus of 3.6 GPa or more and 10 GPa or less.
In the present invention, the elastic modulus of the polyimide compound was measured by preparing a polyimide film having a thickness of about 15 μm, cutting it into a test piece having a size of 10 mm×80 mm, and measuring the elastic modulus in the MD direction and the TD direction at a tensile speed of 10 mm/min using a tensile tester (manufactured by Shimadzu Corporation, product name: AG-Xplus 50 kN). The average value of the elastic modulus in the MD direction and the elastic modulus in the TD direction were calculated.

The tensile strength of the solvent-soluble polyimide compound of the present invention is preferably 90 MPa or more, and more preferably 110 MPa or more. By making the tensile strength of the solvent-soluble polyimide compound 110 MPa or more, the compound can withstand the expansion and contraction of the silicon material during charging and discharging, and the cycle characteristics are improved.
In the present invention, the tensile strength of the polyimide compound was measured by preparing a polyimide film having a thickness of about 15 μm, cutting it into a test piece having a size of 10 mm×80 mm, and measuring the tensile strength in the MD direction and the TD direction at a tension speed of 10 mm/min using a tensile tester (manufactured by Shimadzu Corporation, product name: AG-Xplus 50 kN). The average value of the tensile strength in the MD direction and the tensile strength in the TD direction were calculated.

The number average molecular weight of the solvent-soluble polyimide compound of the present invention is preferably 20,000 to 150,000, and more preferably 30,000 to 100,000.
In the present invention, the number average molecular weight is a polystyrene equivalent value based on a calibration curve prepared using standard polystyrene with a gel permeation chromatography (GPC) apparatus.
By setting the number average molecular weight within the above numerical range, it is possible to easily handle the binder during preparation, easily fabricate the electrode, and obtain a strong negative electrode active material layer.

Preferably, the carboxyl group-containing diamine compound is represented by the following general formula (1) or (2): By using a carboxyl group-containing diamine compound represented by such a general formula, the initial charge/discharge efficiency and cycle characteristics of a lithium ion secondary battery can be further improved.
More preferably, the carboxyl group-containing diamine compound is represented by the following general formula (1).
The diamine compound represented by the general formula (1) and the diamine compound represented by the general formula (2) may be used in combination.

In the above general formulas (1) and (2), R ₁ is represented by a single bond or (CH ₂ ) _p , where p is an integer of 1 to 6, and preferably 1 to 3.
In the above general formulas (1) and (2), n and o each represent an integer of 1 to 5, more preferably 1 to 3, and particularly preferably 1.

Examples of the diamine compound satisfying the above general formula (1) or (2) include, but are not limited to, the following compounds. These compounds may also be used in combination.

Among the diamine compounds listed above, the following diamine compounds are preferred. By using such diamine compounds, the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved. These diamine compounds may also be used in combination.

As the carboxyl group-containing diamine compound, a compound other than the diamine compound represented by the general formula (1) or (2) (hereinafter referred to as the other carboxyl group-containing diamine compound) may be used, or may be used in combination with the diamine compound represented by the general formula (1) or (2).
Other carboxyl group-containing diamine compounds include, for example, 1,3-bis(4-amino-2-carboxyphenoxy)benzene, 3,5-bis(4-aminophenoxy)benzoic acid, 5-amino-2-(aminophenoxy)benzoic acid, and 3,5-diaminobenzoic acid.

The acid anhydride is not particularly limited, and an aromatic acid anhydride or an aliphatic acid anhydride may be used, or these may be used in combination.
The aliphatic acid anhydride may be a straight-chain one, a branched-chain one, or an alicyclic one.

Examples of aromatic acid anhydrides include 4,4'-oxydiphthalic dianhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3-naphthalenedicarboxylic anhydride, pyrrolimetic dianhydride, 3-fluoropyromellitic dianhydride, 3,6-difluoropyromellitic dianhydride, 3,6-bis(trifluoromethyl)pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyl ... Nilsulfonetetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3'',4,4''-terphenyltetracarboxylic dianhydride, 3,3''',4,4'''-quaterphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethynylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene 1,5-pentamethylene-4,4'-diphthalic dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride tetrafluoromethylene-4,4'-diphthalic dianhydride, 1,1,2,2-tetrafluoro-1,2-ethylene-4,4'-diphthalic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, oxy-4,4'-diphthalic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, thio-4,4'-diphthalic dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)-1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,3',5,5'-tetrakis(trifluoromethyl)oxy-4,4'-diphthalic dianhydride, 3,3',6,6'-tetrakis(trifluoromethyl)oxy-4,4'-diphthalic dianhydride, 5,5', 6,6'-tetrakis(trifluoromethyl)oxy-4,4'-diphthalic dianhydride, 3,3',5,5',6,6'-hexakis(trifluoromethyl)oxy-4,4'-diphthalic dianhydride, 3,3'-difluorosulfonyl-4,4'-diphthalic dianhydride, 5,5'-difluorosulfonyl-4,4'-diphthalic dianhydride, 6,6'-difluorosulfonyl-4,4'-diphthalic dianhydride, 3,3',5,5',6,6'-hexafluorosulfonyl-4,4'-diphthalic dianhydride, 3,3'-bis(trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 5,5'-bis (Trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 6,6'-bis(trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 3,3',5,5'-tetrakis(trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 3,3',6,6'-tetrakis(trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 5,5',6,6'-tetrakis(trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 3,3',5,5',6,6'-hexakis(trifluoromethyl)sulfonyl-4,4'-diphthalic dianhydride, 3,3'-diflu perfluoropropylidene-4,4'-diphthalic dianhydride, 5,5'-difluoro-2,2-perfluoropropylidene-4,4'-diphthalic dianhydride, 6,6'-difluoro-2,2-perfluoropropylidene-4,4'-diphthalic dianhydride, 3,3',5,5',6,6'-hexafluoro-2,2-perfluoropropylidene-4,4'-diphthalic dianhydride, 3,3'-bis(trifluoromethyl)-2,2-perfluoropropylidene-4,4'-diphthalic dianhydride, and 4,4'-(4,4'-isopropylidenediphenoxy)bisphthalic dianhydride.
Examples of the aliphatic acid anhydride include norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (CpODA), bicyclo[2,2,2]oct-ene-2,3,5,6-tetracarboxylic dianhydride (BTA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride, carbonyl-4, Examples of the dianhydride include 4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,2-ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, and sulfonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride.

In one embodiment, the polyimide compound of the present invention contains an aromatic diamine compound as a polymerization component. In the present invention, the aromatic diamine compound means an aromatic diamine compound that does not have a carboxyl group.

Examples of the aromatic diamine compound include bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 2,2'-bis(trifluoromethyl)benzidine, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,4(6)-diamino-3,5-diethyltoluene, 5(6)-amino-1,3,3-trimethyl-1-(4-aminophenyl)indan, 4,4'-diamino-2,2'-dimethylphenylamine, and the like. 4,4'-diamino-3,3'-dimethyl-1,1'-biphenyl, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 4-aminophenyl-4-aminobenzoate, 4,4'-(9-fluorenylidene)dianiline, 9,9'-bis( 3-methyl-4-aminophenyl)fluorene, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(4-aminophenoxy)benzene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-methyl-4-aminophenyl)propane, 4,4'-(hexafluoroisopropylidene)dianiline, 2,2-bis(3-amino-4-methyl 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, α,α-bis[4-(4-aminophenoxy)phenyl]-1,3-diisopropylbenzene, α,α-bis[4-(4-aminophenoxy)phenyl]-1,4-diisopropylbenzene, 3,7-diamino-dimethyldibenzothiophene 5,5-dioxide, bis(3-carboxy-4-aminophenyl)methylene, 3,3'-diamino-4,4'-dihydroxy-1,1'-biphenyl, 4,4'-diamino-3,3'-dihydroxy-1,1'-biphenyl, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 1,3-bis(3-hydroxy-4-aminophenoxy)benzene, 2,2-bis(3-hydroxy-4-aminophenyl)benzene and 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone.
Among the above, bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS) and 1,3-bis(4-aminophenoxy)benzene (TPE-R) are preferred from the viewpoint of the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery.

In addition, a diamine compound represented by the following general formula (3) can also be used as the aromatic diamine compound. By using a diamine compound having such a structure, the initial charge-discharge efficiency and cycle characteristics of a lithium ion secondary battery can be further improved. In addition, the solvent solubility of the polyimide compound can be further improved.

In the above general formula (3), R ₂ to R ₉ are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R ₂ to R ₉ is an aromatic group. Preferably, one or two of R ₂ to R ₉ are aromatic groups.
Preferably, one or two of R ₆ to R ₉ are substituted or unsubstituted aromatic groups, and more preferably, at least R ₆ or R ₈ is an aromatic group.
By having an aromatic group at the above-mentioned position, the steric hindrance of the diamine compound can be suppressed, and the polymerization reaction with an acid anhydride or the like can be smoothly carried out.
In a particularly preferred embodiment, one or two of R ₆ to R ₉ are substituted or unsubstituted aromatic groups, and R ₂ to R ₉ other than the aromatic group are selected from the group consisting of hydrogen, fluorine, and substituted or unsubstituted alkyl groups.
Specifically, compounds represented by the following chemical formulas are included (an embodiment in which R ₈ is an aromatic group, and R ₂ to R ₇ other than R ₈ and R ₉ are hydrogen).

In the present invention, the alkyl group includes linear, branched and cyclic alkyl groups, and further includes alkoxy groups and alkylamino groups which are bonded to the main skeleton via an oxygen atom or a nitrogen atom.
Similarly, the aromatic group includes a substituent bonded to the main skeleton via an oxygen atom, a nitrogen atom, or a carbon atom, and further includes a heteroaromatic group such as a pyrrole group.

The alkyl group and aromatic group are preferably unsubstituted, but may have a substituent, such as an alkyl group, a halogen group such as a fluoro group or a chloro group, an amino group, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, or a sulfonic acid group. The alkyl group and aromatic group may have one or more of these substituents.

The alkyl group preferably has 1 to 10 carbon atoms, and more preferably has 1 to 3 carbon atoms.
Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, a sec-pentyl group, an n-hexyl group, a cyclohexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a chloromethyl group, a dichloromethyl group, a trichloromethyl group, a bromomethyl group, a dibromomethyl group, a tribromomethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a chloroethyl group, a dichloromethyl group, a Examples of such an alkyl group include a chloroethyl group, a trichloroethyl group, a bromoethyl group, a dibromoethyl group, a tribromoethyl group, a hydroxymethyl group, a hydroxyethyl group, a hydroxylpropyl group, a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, a sec-pentyloxy group, an n-hexyloxy group, a cyclohexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, an n-decyloxy group, a trifluoromethoxy group, a methylamino group, a dimethylamino group, a trimethylamino group, an ethylamino group, and a propylamino group.
Among the above alkyl groups, a methyl group, an ethyl group, a methoxy group, an ethoxy group and a trifluoromethyl group are preferred from the standpoint of steric hindrance and heat resistance.

The aromatic group preferably has 5 to 20 carbon atoms, and more preferably has 6 to 10 carbon atoms.
Examples of the aromatic group having 5 to 20 carbon atoms include a phenyl group, a tolyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, a diethylphenyl group, a propylphenyl group, a butylphenyl group, a fluorophenyl group, a pentafluorophenyl group, a chlorophenyl group, a bromophenyl group, a methoxyphenyl group, a dimethoxyphenyl group, an ethoxyphenyl group, a diethoxyphenyl group, a benzyl group, a methoxybenzyl group, a dimethoxybenzyl group, an ethoxybenzyl group, a diethoxybenzyl group, an aminophenyl group, an aminobenzyl group, a nitrophenyl group, a nitrobenzyl group, a cyanophenyl group, a cyanobenzyl group, a phenethyl group, a phenylpropyl group, a phenoxy group, a benzyloxy group, a phenylamino group, a diphenylamino group, a biphenyl group, a naphthyl group, Examples of heteroaromatic groups include a phenyl group, a phenylnaphthyl group, a diphenylnaphthyl group, an anthryl group, an anthrylphenyl group, a phenylanthryl group, a naphthacenyl group, a phenanthryl group, a phenanthrylphenyl group, a phenylphenanthryl group, a pyrenyl group, a phenylpyrenyl group, a fluorenyl group, a phenylfluorenyl group, a naphthylethyl group, a naphthylpropyl group, an anthracenylethyl group, a phenanthrylethyl group, a pyrrole group, an imidazole group, a thiazole group, an oxazole group, a furan group, a thiophene group, a triazole group, a pyrazole group, an isoxazole group, an isothiazole group, a pyridine group, a pyrimidine group, a benzofuran group, a benzothiophene group, a quinoline group, an isoquinoline group, an indolyl group, a benzothiazolyl group, and a carbazolyl group.
Among the above aromatic groups, in terms of availability of starting materials and synthesis costs, a phenyl group, a phenoxy group, a benzyl group and a benzyloxy group are preferred.

Preferred embodiments of the polyimide compound are described below.

One particularly preferred embodiment of the polyimide compound according to the present invention is a reaction product of (a) a carboxyl group-containing diamine compound, (b) an aromatic diamine compound, and (c) an aromatic acid anhydride.

(a) As the carboxyl group-containing diamine compound, it is preferable to use a diamine compound represented by the above general formula (1) or (2). More preferred embodiments of the diamine compound satisfying general formula (1) or (2) are as described above.

The content of the carboxyl group-containing diamine compound (a) in the polyimide compound is preferably 10 mol % or more and 90 mol % or less, and more preferably 20 mol % or more and 80 mol % or less, relative to 100 mol % of the total diamine amount.
By setting the content within the above range, the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved, and further, gelation of the varnish containing the polyimide compound can be prevented.

(b) As the aromatic diamine compound, the above-mentioned compounds can be appropriately selected and used. Among the above-mentioned aromatic diamine compounds, bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 1,3-bis(4-aminophenoxy)benzene (TPE-R), and aromatic diamine compounds satisfying the above general formula (3) are preferred. These compounds may also be used in combination.

The content of the aromatic diamine compound (b) in the polyimide compound is preferably 10 mol% or more and 90 mol% or less, and more preferably 20 mol% or more and 80 mol% or less, based on 100 mol% of the total diamine amount. This can further improve the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery.

As the (c) aromatic acid anhydride, it is preferable to use one represented by the following general formula (4): By using such an aromatic acid anhydride, the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved.

In the above general formula (4), X is selected from a single bond, an alkyl group having 1 to 6 carbon atoms, (CF ₃ ) ₂ C, SO ₂ , and an oxygen atom.

Examples of aromatic acid anhydrides satisfying the above general formula (4) include 4,4'-oxydiphthalic dianhydride (ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-biphenylsulfonetetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, etc.

Note that (c) aromatic acid anhydride is not limited to the above, and aromatic acid anhydrides not satisfying general formula (4) may be used.

A particularly preferred embodiment of the polyimide compound may contain polymerization components other than (a) a carboxyl group-containing diamine compound, (b) an aromatic diamine compound, and (c) an aromatic acid anhydride, as long as the properties of the present invention are not impaired.

One particularly preferred embodiment of the polyimide compound according to the present invention is a reaction product of (d) a carboxyl group-containing diamine compound and (e) an alicyclic acid anhydride.

(d) As the carboxyl group-containing diamine compound, it is preferable to use a diamine compound represented by the above general formula (1) or (2). More preferred embodiments of the diamine compound satisfying general formula (1) or (2) are as described above.

The content of the (d) carboxyl group-containing diamine compound in the polyimide compound is preferably 10 mol% or more and 90 mol% or less, and more preferably 20 mol% or more and 80 mol% or less, relative to 100 mol% of the total diamine amount. This can further improve the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery.

(e) As the alicyclic acid anhydride, the above-mentioned may be appropriately selected and used. Among the above-mentioned alicyclic acid anhydrides, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (CpODA) and bicyclo[2,2,2]octo-ene-2,3,5,6-tetracarboxylic dianhydride (BTA) are preferred from the viewpoint of the initial charge/discharge efficiency of the lithium ion secondary battery.

In a particularly preferred embodiment, the polyimide compound may contain polymerization components other than (d) a carboxyl group-containing diamine compound and (e) an alicyclic acid anhydride, as long as the properties of the present invention are not impaired.

The polyimide compound of the present invention can be produced by a conventional method using the above diamine compound and the above acid anhydride. Specifically, the diamine compound is reacted with the acid anhydride to obtain a polyamic acid, which is then subjected to a cyclization dehydration reaction to convert it into a polyimide compound.

The mixing ratio of the acid anhydride and the diamine compound is preferably 0.5 mol% to 1.5 mol% of the total amount of the diamine compound per 1 mol% of the total amount of the acid anhydride, and more preferably 0.9 mol% to 1.1 mol%.

The reaction between the diamine compound and the acid anhydride is preferably carried out in an organic solvent. The organic solvent is not particularly limited as long as it does not react with the diamine compound and the acid anhydride of the present invention and can dissolve the reaction product of the diamine compound and the acid anhydride, and examples of the organic solvent include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N'-dimethylimidazolidinone, γ-butyrolactone, dimethylsulfoxide, sulfolane, 1,3-dioxolane, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, dipropylene glycol dimethyl ether, diethylene ... Coal dibutyl ether, dibenzyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propyl acetate, propylene glycol diacetate, butyl acetate, isobutyl acetate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, n-butyl acetate, butyl carbitol acetate, methyl lactate, ethyl lactate, butyl lactate, methyl benzoate, ethyl benzoate, triglyme, tetraglyme, acetylacetone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, cyclopentanone, 2-heptanone, butyl alcohol, isobutyl alcohol, pentanol, 4-methyl-2-pentanol, 3-methyl-2-butanol, 3-methyl-3-methoxybutanol, diacetone alcohol, toluene, xylene, and the like.
From the viewpoint of the solubility of the polyimide compound of the present invention, N-methyl-2-pyrrolidone, N,N'-dimethylimidazolidinone, and γ-butyrolactone are preferred for the polyimide.

The reaction temperature between the diamine compound and the acid anhydride is preferably 40°C or less in the case of chemical imidization. In the case of thermal imidization, the reaction temperature is preferably 150 to 220°C, and more preferably 170 to 200°C.

In the cyclization dehydration reaction, an imidization catalyst may be used. For example, methylamine, ethylamine, trimethylamine, triethylamine, propylamine, tripropylamine, butylamine, tributylamine, tert-butylamine, hexylamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, triethylenediamine, N-methylpyrrolidine, N-ethylpyrrolidine, aniline, benzylamine, toluidine, trichloroaniline, pyridine, collidine, lutidine, picoline, quinoline, isoquinoline, valerolactone, and the like can be used.
If necessary, an azeotropic dehydrating agent such as toluene, xylene, or ethylcyclohexane, or an acid catalyst such as acetic anhydride, propionic anhydride, butyric anhydride, or benzoic anhydride can be used.

In the reaction between the diamine compound and the acid anhydride, a sealing agent such as benzoic acid, phthalic anhydride, or hydrogenated phthalic anhydride can be used.
Furthermore, by using maleic anhydride, ethynylphthalic anhydride, methylethynylphthalic anhydride, phenylethynylphthalic anhydride, phenylethynyltrimellitic anhydride, 3- or 4-ethynylaniline, or the like, a double bond or triple bond can be introduced into the terminal of the polyimide compound.

(Resin composition for producing negative electrode of lithium ion secondary battery)
The resin composition for producing a lithium ion secondary battery negative electrode (hereinafter, sometimes simply referred to as a resin composition) of the present invention contains the above-mentioned polyimide compound and a negative electrode active material. In one embodiment, the resin composition contains a conductive agent.

The structure of the polyimide compound has been described above, and therefore will not be described here.
The content of the polyimide compound in the resin composition is preferably 1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 18% by mass or less.
By setting the content of the polyimide compound in the resin composition within the above numerical range, the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved.

In the resin composition of the present invention, it is preferable to use a silicon material as the negative electrode active material, since the volume change of the silicon can be effectively prevented.
Examples of silicon materials include silicon particles, alloys of silicon with metals such as tin, nickel, iron, copper, silver, cobalt, manganese, and zinc, and compounds of silicon with boron, nitrogen, oxygen, carbon, and the like.
Examples of silicon materials include SiO, _SiO2 , _SiB4 , _Mg2Si , _Ni2Si , _CoSi2 , _NiSi2 , _Cu5Si , _FeSi2 , _MnSi2 , _ZnSi2 , SiC _{, Si3N4 , and Si2N2O .}

Materials other than silicon may be used as negative electrode active materials, such as metallic lithium, metal oxides, and graphite.

The resin composition may contain two or more types of negative electrode active materials.

The content of the negative electrode active material in the resin composition is preferably 70% by mass or more and 99% by mass or less, and more preferably 75% by mass or more and 95% by mass or less.
By setting the content of the negative electrode active material in the resin composition within the above numerical range, the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved.

In one embodiment, the resin composition of the present invention contains a conductive agent, for example, carbon black (acetylene black, ketjen black, furnace black, etc.), graphite, carbon fiber, carbon flakes, metal fiber and foil, etc. Among these, carbon black is preferred, and acetylene black is more preferred. The resin composition may contain two or more types of conductive agents.

The content of the conductive agent in the resin composition is preferably 0.1% by mass or more and 25% by mass or less, and more preferably 1% by mass or more and 20% by mass or less.
By setting the content of the conductive agent in the resin composition within the above numerical range, a good conductive path can be formed in the negative electrode active material layer.

The resin composition of the present invention may contain additives, such as thickeners, fillers, etc., to the extent that the properties of the present invention are not impaired.

(Negative electrode for lithium ion secondary batteries)
The negative electrode for a lithium ion secondary battery of the present invention comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, the negative electrode active material layer being composed of the above-mentioned resin composition.

There is no particular limitation on the current collectors that can be used, but examples include copper, nickel, stainless steel, gold, iron, aluminum and alloys thereof, nickel-plated steel, and chrome-plated steel.

The thickness of the negative electrode active material layer is preferably 15 μm or more and 150 μm or less, and more preferably 30 μm or more and 120 μm or less. By setting the thickness of the negative electrode active material layer within the above numerical range, the initial charge/discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved.

The negative electrode for a lithium ion secondary battery of the present invention can be produced by applying an organic solvent in which the above-mentioned resin composition is dissolved or dispersed onto a current collector, and then drying the applied solvent.
As the organic solvent, those mentioned above can be used, and from the viewpoint of the solubility or dispersibility of the resin composition, N-methyl-2-pyrrolidone, N,N'-dimethylimidazolidinone and γ-butyrolactone are preferred.
The coating method is not particularly limited, and examples thereof include a die coater method, a three-roll transfer coater method, a doctor blade method, a dip method, a direct roll method, and a gravure method.

(Lithium-ion secondary battery)
The lithium ion secondary battery of the present invention is characterized by comprising the above-mentioned negative electrode and a positive electrode. In one embodiment, the lithium ion secondary battery of the present invention further comprises a separator disposed between the negative electrode and the positive electrode.
Hereinafter, each component of the lithium ion secondary battery will be described, but since the negative electrode has been described above, a description thereof will be omitted here.

As the positive electrode, any positive electrode that has been conventionally used for lithium ion secondary batteries can be appropriately used.
The positive electrode can be prepared by applying a resin composition for preparing a positive electrode for a lithium ion secondary battery onto a current collector and drying the applied resin composition.

The resin composition for producing a positive electrode of a lithium ion secondary battery may contain a positive electrode active material and a binder resin. The resin composition for producing a positive electrode of a lithium ion secondary battery may also contain the conductive agent and additives.

Examples of the positive electrode active material include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium iron phosphate.
As the binder resin, the above-mentioned polyimide compounds may be used, or polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyethylene, or the like may be used.

In addition, the positive electrode is not limited to the above, and lithium foil, etc. can also be used.

The separator may be any conventional separator, such as a paper separator, a resin separator such as polyethylene or polypropylene, or a glass fiber separator.

The positive and negative electrodes are placed in a battery container, and the container is filled with an organic solvent (electrolyte) in which an electrolyte is dissolved. The electrolyte is not particularly limited, and examples thereof include _LiPF6 , _{LiClO4, LiBF4} , _LiClF4 , _LiAsF6 , _LiSbF6 , _{LiAlO4 , LiAlCl4} , _CF3SO3Li , LiN( _CF3SO2 ) ₃ , LiCl _, and LiI _.
Among these, LiPF ₆ , LiClO ₄ and CF ₃ SO ₃ Li are preferred because they have a high degree of dissociation.
The organic solvent is also not particularly limited, and examples thereof include carbonate compounds, lactone compounds, ether compounds, sulfolane compounds, dioxolane compounds, ketone compounds, nitrile compounds, and halogenated hydrocarbon compounds.
Specific examples of the solvent include carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethyl carbonate, ethylene glycol diethyl carbonate, and vinylene carbonate, lactones such as γ-butyl lactone, ethers such as dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,4-dioxane, sulfolanes such as sulfolane and 3-methylsulfolane, dioxolanes such as 1,3-dioxolane, ketones such as 4-methyl-2-pentanone, nitriles such as acetonitrile, propionitrile, valeronitrile, and benzonitrile, halogenated hydrocarbons such as 1,2-dichloroethane, and other ionic liquids such as methyl formate, dimethylformamide, diethylformamide, dimethylsulfoxide, imidazolium salts, and quaternary ammonium salts. Mixtures of these may also be used.
Among these, carbonate compounds are preferred because the solubility of the polyimide compound used in the negative electrode is low and swelling of the polyimide can be suppressed.

The shape of the lithium ion secondary battery is not particularly limited and can be modified as appropriate depending on the application, such as paper type, button type, coin cell type, laminated type, cylindrical type, and square type.

Example 1
Synthesis of Solvent-Soluble Polyimide Compound A
Into a 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer, 43.25 g (100 mmol) of a diamine compound (BAPS) represented by the chemical formula below, 28.63 g (100 mmol) of a diamine compound (MBAA) represented by the chemical formula below, 58.84 g (200 mmol) of an acid anhydride (BPDA) represented by the chemical formula below, 700 g of N-methyl-2-pyrrolidone, 3.2 g (40 mmol) of pyridine, and 70 g of toluene were charged and reacted under a nitrogen atmosphere at 180° C. for 8 hours while removing the toluene from the system during the reaction, thereby obtaining a 15 wt % polyimide solution.

Example 2
Synthesis of Solvent-Soluble Polyimide Compound B
Using the same apparatus as in Example 1, 43.25 g (100 mmol) of BAPS, 28.63 g (100 mmol) of MBAA, 15.22 g (50 mmol) of a diamine compound (PHBAAB) represented by the following chemical formula, 44.13 g (150 mmol) of BPDA, 31.02 g (100 mmol) of an acid anhydride (ODPA) represented by the following chemical formula, 868 g of N-methyl-2-pyrrolidone, 4.0 g (50 mmol) of pyridine, and 87 g of toluene were added and reacted under a nitrogen atmosphere at 180° C. for 9 hours while removing the toluene from the system during the reaction, thereby obtaining a 15 wt % polyimide solution.

Example 3
Synthesis of Solvent-Soluble Polyimide Compound C
Using the same apparatus as in Example 1, 28.63 g (100 mmol) of MBAA, 15.22 g (50 mmol) of PHBAAB, 29.23 g (100 mmol) of a diamine compound (TPE-R) represented by the following chemical formula, 31.02 g (100 mmol) of ODPA, 37.23 g (150 mmol) of an acid anhydride (BTA) represented by the following chemical formula, 750 g of N-methyl-2-pyrrolidone, 4.0 g (50 mmol) of pyridine, and 75 g of toluene were added and reacted under a nitrogen atmosphere at 180° C. for 10 hours while removing the toluene from the system during the reaction, thereby obtaining a 15 wt % polyimide solution.

Example 4
Synthesis of Solvent-Soluble Polyimide Compound D
Using the same apparatus as in Example 1, 28.63 g (100 mmol) of MBAA, 38.44 g (100 mmol) of an acid anhydride (CpODA) represented by the following chemical formula, 360 g of N-methyl-2-pyrrolidone, 1.6 g (20 mmol) of pyridine, and 36 g of toluene were charged and reacted under a nitrogen atmosphere at 180° C. for 12 hours while removing the toluene from the system during the reaction, thereby obtaining a 15 wt % polyimide solution.

(Comparative Example 1)
Synthesis of solvent-soluble polyimide compound a
Using the same apparatus as in Example 1, 43.25 g (100 mmol) of BAPS, 38.44 g (100 mmol) of CpODA, 442 g of N-methyl-2-pyrrolidone, 1.6 g (20 mmol) of pyridine, and 44 g of toluene were charged and reacted under a nitrogen atmosphere at 180° C. for 12 hours while removing the toluene from the system during the reaction, thereby obtaining a 15 wt % polyimide solution.

(Comparative Example 2)
Synthesis of solvent-soluble polyimide compound b
Using the same apparatus as in Example 1, 15.22 g (100 mmol) of DABz represented by the following chemical formula, 38.44 g (100 mmol) of CpODA, 284 g of N-methyl-2-pyrrolidone, 1.6 g (20 mmol) of pyridine, and 28 g of toluene were charged and reacted under a nitrogen atmosphere at 180° C. for 10 hours while removing the toluene from the system during the reaction, thereby obtaining a 15 wt % polyimide solution.

<<Elasticity measurement>>
The solutions obtained in the above Examples and Comparative Examples were applied onto a 10 cm square glass plate by spin coating, and dried for 0.5 hour at 100° C., 0.5 hour at 200° C., and 1 hour at 250° C. Thereafter, the plate was peeled off from the glass plate and cut to obtain a test piece measuring 80 mm long, 10 mm wide, and 15 μm thick.
The elastic modulus of this test piece was measured in the MD and TD directions at a tension speed of 10 mm/min using a tensile tester (manufactured by Shimadzu Corporation, product name: AG-Xplus 50 kN). The average values of the elastic modulus in the MD and TD directions were calculated, and the measurement results are summarized in Table 1.

<<Tensile strength measurement>>
A sample was prepared in the same manner as in the measurement of the elastic modulus, and the tensile strength of this test piece was measured in the MD direction and the TD direction using a tensile tester (manufactured by Shimadzu Corporation, product name: AG-Xplus 50 kN) at a tension speed of 10 mm/min. The average values of the elastic modulus in the MD direction and the tensile strength in the TD direction were calculated, and the measurement results are summarized in Table 1.

<<Initial charge/discharge efficiency>>
The solvent-soluble polyimide compound A obtained in Example 1 above, silicon monoxide (SiO) and graphite as negative electrode active materials, and acetylene black (Li-400, manufactured by Denka Co., Ltd.) and carbon fiber (VGCF-H, manufactured by Showa Denko K.K.) as conductive agents were mixed in the following composition to prepare a resin composition for preparing a lithium ion secondary battery negative electrode. Except for changing the solvent-soluble polyimide compound A to the solvent-soluble polyimide compounds obtained in the other Examples and Comparative Examples, a resin composition for preparing a lithium ion secondary battery negative electrode was prepared in the same manner.
(Composition of resin composition for producing lithium ion secondary battery negative electrode)
Solvent-soluble polyimide compound A 6% by mass
Silicon monoxide 18% by mass
Graphite 72% by mass
Acetylene black 3% by mass
Carbon fiber: 1% by mass

A 10 μm-thick electrolytic copper foil was prepared as a negative electrode current collector, and the resin composition for producing lithium-ion secondary battery negative electrodes prepared as described above was applied to its surface and dried to form a 50 μm-thick negative electrode active material layer, thereby obtaining a negative electrode.

A lithium foil was used as the positive electrode, ethylene carbonate and ethyl methyl carbonate were used as the electrolyte, and a polyolefin single-layer separator (Celgard (registered trademark) 2500, manufactured by Celgard Corporation) was used to fabricate a coin cell-type lithium ion secondary battery.

[Evaluation of Battery Performance]
The lithium ion secondary battery prepared as described above was allowed to stand for 24 hours in an environment at 25° C. Thereafter, a performance test of the lithium ion secondary battery was carried out in an environment at 25° C. The test method was as follows, and the test results are summarized in Table 2.

<<Initial charge/discharge efficiency evaluation>>
The initial charge/discharge efficiency was measured by the following method.
CC (constant current) charging was performed at a current density equivalent to 0.1 C to 5 mV, followed by switching to CV (constant voltage) charging at 5 mV, charging until a current density equivalent to 0.01 C was reached, and then CC discharging at a current density equivalent to 0.1 C to 1.2 V was performed for two cycles at 25° C., and the ratio of the 0.1 C discharge capacity B in the first cycle to the 0.1 C charge capacity A in the first cycle at this time was taken as the initial charge/discharge efficiency, which was calculated based on the formula: initial charge/discharge efficiency (%)=(B/A)×100, and the results are shown in Table 2.

<<Cycle characteristic evaluation>>
The cycle characteristics were measured by the following method. After two cycles of measuring the initial charge-discharge efficiency, CC (constant current) charging was performed at a current density of 0.2C to 5 mV, then switched to CV (constant voltage) charging at 5 mV, charging until the current density was equivalent to 0.02C, and then CC discharging at a current density of 0.2C to 1.2V was performed for three cycles at 25 ° C., followed by CC (constant current) charging at a current density of 0.5C to 5 mV, then switched to CV (constant voltage) charging at 5 mV, charging until the current density was equivalent to 0.05CC, and then CC discharging at a current density of 0.5C to 1.2V was performed for 30 cycles at 25 ° C., and the discharge capacity equivalent to 0.5C at the 30th cycle was taken as C. The cycle characteristics were calculated based on the formula ΔC (%) = (C / B) × 100, and the results are summarized in Table 2.

Claims (7)

A solvent-soluble polyimide used as an electrode material for a lithium-ion secondary battery, comprising:
(a) a reaction product of a diamine component containing a carboxyl group-containing diamine and (b) an aromatic diamine compound , and (c) an acid anhydride component containing an aromatic acid anhydride , or (a) a reaction product of a diamine compound containing a carboxyl group-containing diamine, and (e) an acid anhydride component containing an alicyclic acid anhydride ,
The (b) aromatic diamine compound includes a diamine compound represented by the following general formula (3):
(In general formula (3), R ₂ to R ₉ are each independently selected from the group consisting of hydrogen, fluorine, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted aromatic group, and at least one of R ₂ to R ₉ is an aromatic group.)
the solvent-soluble polyimide is a polyimide soluble in at least one organic solvent selected from the group consisting of N-methyl-2-pyrrolidone, N,N'-dimethylimidazolidinone, and γ-butyrolactone;
A solvent-soluble polyimide compound having an elastic modulus of 3.4 GPa or more and a tensile strength of 90 MPa or more. 2. The solvent-soluble polyimide compound according to claim 1, wherein the carboxyl group-containing diamine compound (a) is represented by the following general formula (1) or (2):
(In general formulas (1) and (2), R ₁ is represented by a single bond or (CH ₂ ) _p , p is an integer from 1 to 6, and n and o are each an integer from 1 to 5.) 3. The solvent-soluble polyimide compound according to claim 1 , wherein the aromatic acid anhydride (c) is represented by the following general formula (4):
(In general formula (4), X is selected from a single bond, an alkyl group having 1 to 6 carbon atoms, (CF ₃ ) ₂ C, SO ₂ , and an oxygen atom.) The solvent-soluble polyimide compound according to any one of claims 1 to 3, wherein the (e) alicyclic acid anhydride is at least one selected from the group consisting of norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″, 6,6 ″-tetracarboxylic acid dianhydride and bicyclo[2,2,2]oct-ene-2,3,5,6-tetracarboxylic acid dianhydride. A resin composition for producing a lithium ion secondary battery negative electrode, comprising the solvent-soluble polyimide compound according to any one of claims 1 to 4 and a negative electrode active material. a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector,
6. A negative electrode for a lithium ion secondary battery, wherein the negative electrode active material layer is made of the resin composition for producing a lithium ion secondary battery negative electrode according to claim 5 . A lithium ion secondary battery comprising the negative electrode for lithium ion secondary batteries according to claim 5 and a positive electrode.