WO2021053800A1 - Solvent-soluble polyimide compound, lithium-ion secondary battery negative electrode producing resin composition including said solvent-soluble polyimide compound, lithium-ion secondary battery negative electrode configured using said lithium-ion secondary battery negative electrode producing resin composition, and lithium-ion secondary battery provided with said lithium-ion secondary battery negative electrode - Google Patents

Abstract

[Problem]To provide a solvent-soluble polyimide compound with which the initial charge/discharge efficiency and the cycle characteristics of a lithium-ion secondary battery can be significantly improved. [Solution] A solvent-soluble polyimide compound according to the present invention is a solvent-soluble polyimide used as an electrode material for a lithium-ion secondary battery, and is characterized in that the solvent-soluble polyimide compound is a reactant of a carboxyl group-containing diamine and an acid anhydride, has an elastic modulus of at least 3.4 GPa.

Description

A solvent-soluble polyimide compound, a resin composition for producing a negative electrode of a lithium ion secondary battery containing the solvent-soluble polyimide compound, and a negative electrode for a lithium ion secondary battery constructed by using the resin composition for producing a negative electrode of a lithium ion secondary battery. And a lithium ion secondary battery including the negative electrode for the lithium ion secondary battery.

The present invention is a lithium ion secondary composed of a solvent-soluble polyimide compound, a resin composition for producing a negative electrode of a lithium ion secondary battery containing the solvent-soluble polyimide compound, and a resin composition for producing a negative electrode of a lithium ion secondary battery. The present invention relates to a negative electrode for a battery and a lithium ion secondary battery including the negative electrode for a lithium ion secondary battery.

In recent years, the miniaturization of electronic devices such as smartphones has been rapidly progressing, and the development of small, lightweight, and high energy density lithium ion secondary batteries has been actively carried out.
As the negative electrode active material contained in the lithium ion secondary battery, a silicon (Si) material having a high discharge capacity and excellent initial charge / discharge efficiency and cycle characteristics is used, but silicon has a large expansion / contraction during charge / discharge. Repeated use may cause cutting of the conductive path between the negative electrode active materials and peeling of the current collector and the negative electrode active material layer.

In view of the above-mentioned problem of the silicon material, the use of a polyimide compound is being studied in place of the conventionally used carboxymethyl cellulose and the like as the material constituting the negative electrode and the binder resin (see Patent Document 1 and the like).

However, there is room for improvement in the initial charge / discharge efficiency and cycle characteristics, and a polyimide compound capable of further improving the initial charge / discharge efficiency and cycle characteristics has been required.

International Publication WO2017 / 138604 Pamphlet

The present invention has been made in view of the above problems, and the problem to be solved is a solvent-soluble polyimide compound capable of remarkably improving the initial charge / discharge efficiency and cycle characteristics of the lithium ion secondary battery. Is to provide.
Another object of the present invention is to provide a resin composition for producing a negative electrode of a lithium ion secondary battery containing the solvent-soluble polyimide compound.
Another object of the present invention is to provide a negative electrode for a lithium ion secondary battery constructed by using the resin composition for producing a negative electrode for a lithium ion secondary battery.
Further, the present invention provides a lithium ion secondary battery including the negative electrode for the lithium ion secondary battery.

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.
It is characterized by having an elastic modulus of 3.4 GPa or more.

In one embodiment, the carboxyl group-containing diamine compound is represented by the following general formula (1) or (2).

(In the 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 integers of 1 to 5, respectively. Is.)

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

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).

(Formula (3) in, R 2 _~ R ₉ are each independently hydrogen, fluorine, selected from the group consisting of substituted or unsubstituted alkyl group and a substituted or unsubstituted aromatic group, R ₂ ~ At _{least one of 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.

In one embodiment, (c) aromatic acid anhydride is represented by the following general formula (4).

(In the 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 solvent-soluble polyimide compound and a negative electrode active material.

The negative electrode for a lithium ion secondary battery of the present invention includes 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 resin composition for producing a negative electrode of a lithium ion secondary battery.

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

According to the present invention, it is possible to provide a solvent-soluble polyimide compound capable of significantly improving the initial charge / discharge efficiency and cycle characteristics of a lithium ion secondary battery.
Further, it is possible to provide a resin composition for producing a negative electrode of a lithium ion secondary battery containing the solvent-soluble polyimide compound.
Further, it is possible to provide a negative electrode for a lithium ion secondary battery constructed by using the resin composition for producing a negative electrode for a lithium ion secondary battery.
Further, it is possible to provide a lithium ion secondary battery including the negative electrode for the lithium ion secondary battery.

(Solvent-soluble polyimide compound)
The solvent-soluble polyimide compound of the present invention is characterized by being 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 obtained by reacting two or more kinds of a carboxyl group-containing diamine compound and an acid anhydride.

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

The solvent-soluble polyimide compound of the present invention is characterized by having an elastic modulus of 3.4 GPa or more. More preferably, the elastic modulus of the solvent-soluble polyimide compound is 3.6 GPa or more and 10 GPa or less.
In the present invention, the elastic modulus of the polyimide compound is such that after preparing a polyimide single film having a thickness of about 15 μm, a test piece having a size of 10 mm × 80 mm is used as a tensile tester (manufactured by Shimadzu Corporation, trade name: AG-Xplus 50 kN). ) Was used to measure the elastic modulus in the MD direction and the TD direction at a tensile speed of 10 mm / min. The average value of the elastic modulus in the MD direction and the elastic modulus in the TD direction was calculated.

The tensile strength of the solvent-soluble polyimide compound of the present invention is preferably 90 MPa or more, more preferably 110 MPa or more. By setting the tensile strength of the solvent-soluble polyimide compound to 110 MPa or more, it can withstand 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 is such that after preparing a polyimide single film having a thickness of about 15 μm, a test piece having a size of 10 mm × 80 mm is used as a tensile tester (manufactured by Shimadzu Corporation, trade name: AG-Xplus 50 kN). ) Was used to measure the tensile strength in the MD direction and the TD direction at a tensile speed of 10 mm / min. The average value of the tensile strength in the MD direction and the tensile strength in the TD direction was calculated.

The number average molecular weight of the solvent-soluble polyimide compound of the present invention is preferably 20,000 to 150,000, 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 by using a standard polystyrene by a gel permeation chromatography (GPC) apparatus.
By setting the number average molecular weight in the above numerical range, it is possible to obtain a strong negative electrode active substance layer that is easy to handle at the time of binder production and electrode production.

Preferably, the carboxyl group-containing diamine compound is represented by the following general formula (1) or (2). By using the carboxyl group-containing diamine compound represented by such a general formula, the initial charge / discharge efficiency and cycle characteristics of the 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 , and p is an integer of 1 to 6, preferably 1 to 3.
Further, in the general formulas (1) and (2), n and o are integers of 1 to 5, respectively, 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. Moreover, you may use these together.

Among the listed diamine compounds, the following diamine compounds are preferable. By using such a diamine compound, the initial charge / discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved. Moreover, you may use these together.

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 other carboxyl group-containing diamine compound) may be used, and the general formula (1) may be used. Alternatively, it may be used in combination with the diamine compound represented by (2).
Examples of other carboxyl group-containing diamine compounds include 1,3-bis (4-amino-2-carboxyphenoxy) benzene, 3,5-bis (4-aminophenoxy) benzoic acid, and 5-amino-2- ( Aminophenoxy) Benzoic acid, 3,5-diaminobenzoic acid and the like can be mentioned.

The acid anhydride is not particularly limited, and an aromatic acid anhydride may be used, an aliphatic acid anhydride may be used, or these may be used in combination.
Further, the aliphatic acid anhydride may be a linear type, a branched chain type, or an alicyclic type.

Examples of the aromatic acid anhydride include 4,4'-oxydiphthalic acid dianhydride (ODPA), 3,3', 4,4'-biphenyltetracarboxylic acid hydride (BPDA), and 2,3-naphthalene. Dicarboxylic acid anhydride, pyrolimetic acid dianhydride, 3-fluoropyromellitic dianhydride, 3,6-difluoropyromellitic hydride, 3,6-bis (trifluoromethyl) pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride , 3,3', 4,4'-biphenylsulfonetetracarboxylic hydride, 2,3,3', 4'-biphenyltetracarboxylic hydride, 3,3 ″, 4,4'' -Terphenyltetracarboxylic dianhydride, 3,3''', 4,4'''-Quaterphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride Methylene-4,4'-diphthalic hydride, 1,1-ethynidene-4,4'-diphthalic hydride, 2,2-propylidene-4,4'-diphthalic hydride, 1 , 2-ethylene-4,4'-diphthalic hydride, 1,3-trimethylen-4,4'-diphthalic hydride, 1,4-tetramethylene-4,4'-diphthalic hydride , 1,5-Pentamethylene-4,4'-diphthalic hydride, 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- (3,3) 4-Dicarboxyphenoxy) phenyl] methanenianhydride, 2,2-bis [3- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 2,2-bis [4- (3,4-di) Carboxyphenoxy) phenyl] propane dianhydride, difluoromethylene-4,4'-diphthalic hydride, 1,1,2,2-tetrafluoro-1,2-ethylene-4,4'-diphthalate dianhydride , 3,3', 4,4'-diphenylsulfonetetracarboxylic hydride, oxy-4,4'-diphthalic hydride, bis (3,4-dicarboxyphenyl) ether dianhydride , Thio-4,4'-diphthalic hydride, sulfonyl-4,4'-diphthalate Anhydride, 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 acid dianhydride, 1,2,5,6- Naphthalenetetracarboxylic hydride, 3,3', 5,5'-tetrakis (trifluoromethyl) oxy-4,4'-diphthalic hydride, 3,3', 6,6'-tetrakis (tri) Fluoromethyl) oxy-4,4'-diphthalic acid dianhydride, 5,5', 6,6'-tetrakis (trifluoromethyl) oxy-4,4'-diphthalic acid dianhydride, 3,3', 5,5', 6,6'-hexakis (trifluoromethyl) oxy-4,4'-diphthalic hydride, 3,3'-difluorosulfonyl-4,4'-diphthalic hydride, 5, 5'-Difluorosulfonyl-4,4'-diphthalic acid dianhydride, 6,6'-difluorosulfonyl-4,4'-diphthalic acid dianhydride, 3,3', 5,5', 6,6'-Hexafluorosulfonyl-4,4'-diphthalic hydride, 3,3'-bis (trifluoromethyl) sulfonyl-4,4'-diphthalic hydride, 5,5'-bis (trifluoromethyl) ) Sulfonyl-4,4'-diphthalic hydride, 6,6'-bis (trifluoromethyl) sulfonyl-4,4'-diphthalic hydride, 3,3', 5,5'-tetrakis () Trifluoromethyl) sulfonyl-4,4'-diphthalic hydride, 3,3', 6,6'-tetrakis (trifluoromethyl) sulfonyl-4,4'-diphthalic hydride, 5,5' , 6,6'-tetrakis (trifluoromethyl) sulfonyl-4,4'-diphthalic hydride, 3,3', 5,5', 6,6'-hexakis (trifluoromethyl) sulfonyl-4, 4'-diphthalic hydride, 3,3'-difluoro-2,2-perfluoropropylidene-4,4'-diphthalic hydride, 5,5'-difluoro-2,2-perfluoropropi LIDEN-4,4'-diphthalic hydride, 6,6'-difluoro-2,2-perfluoro Propyridene-4,4'-diphthalic dianhydride, 3,3', 5,5', 6,6'-hexafluoro-2,2-perfluoropropyridene-4,4'-diphthalic dianhydride , 3,3'-bis (trifluoromethyl) -2,2-perfluoropropyridene-4,4'-diphthalic dianhydride and 4,4'-(4,4'-isopropyridenediphenoxy) bisphthal Acid dianhydride and the like can be mentioned.
Examples of the aliphatic acid anhydride include norbornan-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornan-5,5'', 6,6''-tetracarboxylic acid dianhydride. (CpODA), Bicyclo [2,2,2] Octo-ene-2,3,5,6-tetracarboxylic acid dianhydride (BTA), 1,2,4,5-Cyclohexanetetracarboxylic acid dianhydride , 1,2,3,4-butanetetracarboxylic acid dianhydride, 3,3', 4,4'-bicyclohexyltetracarboxylic acid dioanoxide, carbonyl-4,4'-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) Acid) dianhydride, oxy-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis (cyclohexane-1,2-dicarboxylic acid) dianhydride and Examples thereof include 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 having no 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'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3,3'-dimethyl-1,1'-biphenyl, 3,4'-diaminodiphenyl ether, 4,4 '-Diaminodiphenyl ether, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, 4-aminophenyl-4-aminobenzoate, 4,4'-(9-) Fluolenilidene) 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-methylphenyl) 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-aminopheni) L) Benzene and 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone and the like can be mentioned.
Among the above, from the viewpoint of initial charge / discharge efficiency and cycle characteristics of the lithium ion secondary battery, bis [4- (4-aminophenoxy) phenyl] sulfone (BAPS) and 1,3-bis (4-aminophenoxy) benzene (TPE-R) is preferable.

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

In the general formula _{(3), R 2 ~ R} 9 are each independently hydrogen, fluorine, selected from the group consisting of substituted or unsubstituted alkyl group and a substituted or unsubstituted aromatic group, R ₂ ~ At _{least one of 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 satisfactorily promoted.
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 hydrogen, fluorine and a substituted or unsubstituted alkyl group. Selected from the group consisting of.
Specific examples thereof include compounds represented by the following chemical formulas (a mode in which _{R 8} is an aromatic group and _{R 2} to R ₇ and R ₉ other than _{R 8 are hydrogen).}

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

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

The alkyl group preferably has 1 to 10 carbon atoms, and more preferably 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, and n-. Xyl group, cyclohexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, fluoromethyl group, difluoromethyl group, trifluoromethyl group, chloromethyl group, dichloromethyl group, Trichloromethyl group, bromomethyl group, dibromomethyl group, tribromomethyl group, fluoroethyl group, difluoroethyl group, trifluoroethyl group, chloroethyl group, dichloroethyl group, trichloroethyl group, bromoethyl group, dibromoethyl group, tribromoethyl group Group, hydroxymethyl group, hydroxyethyl group, hydroxylpropyl group, methoxy group, ethoxy group, n-propoxy group, n-butoxy group, n-pentyloxy group, sec-pentyloxy group, n-hexyloxy group, cyclo Xyloxy group, n-heptyloxy group, n-octyloxy group, n-nonyloxy group, n-decyloxy group, trifluoromethoxy group, methylamino group, dimethylamino group, trimethylamino group, ethylamino group, propylamino group, etc. Can be mentioned.
Among the above-mentioned alkyl groups, a methyl group, an ethyl group, a methoxy group, an ethoxy group and a trifluoromethyl group are preferable because of steric hindrance and heat resistance.

The aromatic group preferably has 5 to 20 carbon atoms, and more preferably 6 to 10 carbon atoms.
Examples of the aromatic group having 5 to 20 carbon atoms include a phenyl group, a trill group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, a diethylphenyl group, a propylphenyl group, a butylphenyl group, a fluorophenyl group, and a pentafluoro. Phenyl group, chlorphenyl group, bromophenyl group, methoxyphenyl group, dimethoxyphenyl group, ethoxyphenyl group, diethoxyphenyl group, benzyl group, methoxybenzyl group, dimethoxybenzyl group, ethoxybenzyl group, diethoxybenzyl group, aminophenyl Group, aminobenzyl group, nitrophenyl group, nitrobenzyl group, cyanophenyl group, cyanobenzyl group, phenethyl group, phenylpropyl group, phenoxy group, benzyloxy group, phenylamino group, diphenylamino group, biphenyl group, naphthyl group, Phenylnaphthyl group, diphenylnaphthyl group, anthryl group, anthrylphenyl group, phenylanthryl group, naphthacenyl group, phenanthryl group, phenanthrylphenyl group, phenylphenanthryl group, pyrenyl group, phenylpyrenyl group, fluorenyl group Phenylfluorenyl group, naphthylethyl group, naphthylpropyl group, anthracenylethyl group, phenanthrylethyl group, pyrrole group, imidazole group, thiazole group, oxazole group, furan group, thiophene group, triazole group, pyrazole group , Isooxazole group, isothiazole group, pyridine group, pyrimidine group, benzofuran group, benzothiophene group, quinoline group, isoquinolin group, indolyl group, benzothiazolyl group, carbazolyl group and other heteroaromatic groups.
Among the above-mentioned aromatic groups, a phenyl group, a phenoxy group, a benzyl group and a benzyloxy group are preferable from the viewpoint of easy availability of starting material and synthesis cost.

Hereinafter, preferred embodiments of the polyimide compound will be described.

As one of the particularly preferable embodiments of the polyimide compound according to the present invention, the polyimide compound is a reaction of (a) a carboxyl group-containing diamine compound, (b) an aromatic diamine compound, and (c) an aromatic acid anhydride. It is a thing.

(A) As the carboxyl group-containing diamine compound, it is preferable to use the diamine compound represented by the above general formula (1) or (2). The more preferable embodiment in the diamine compound satisfying the general formula (1) or (2) is as described above.

The content of the (a) carboxyl group-containing diamine compound in the polyimide compound is preferably 10 mol% or more and 90 mol% or less, preferably 20 mol% or more and 80 mol% or less, based on 100 mol% of the total diamine amount. More preferably.
Within the above numerical range, the initial charge / discharge efficiency and cycle characteristics of the lithium ion secondary battery can be further improved. Further, it is possible to prevent the varnish containing the polyimide compound from gelling.

(B) As the aromatic diamine compound, the above-mentioned one 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 the above general formula (3) Aromatic diamine compounds satisfying the above conditions are preferable. Moreover, you may use these together.

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

As the aromatic acid anhydride (c), 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 the aromatic acid anhydride satisfying the above general formula (4) include 4,4'-oxydiphthalic acid dianhydride (ODPA) and 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA). , 3,3', 4,4'-biphenylsulfonetetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetra Examples thereof include carboxylic acid dianhydride.

The aromatic acid anhydride (c) is not limited to this, and the above-mentioned aromatic acid anhydride that does not satisfy the general formula (4) may be used.

The polyimide compound according to a particularly preferable embodiment is a polymerization component other than (a) a carboxyl group-containing diamine compound, (b) an aromatic diamine compound, and (c) an aromatic acid anhydride, as long as the characteristics of the present invention are not impaired. May include.

One of the particularly preferable embodiments 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.

As the (d) carboxyl group-containing diamine compound, it is preferable to use the diamine compound represented by the above general formula (1) or (2). The more preferable embodiment in the diamine compound satisfying the general formula (1) or (2) is 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, preferably 20 mol% or more and 80 mol% or less, based on 100 mol% of the total diamine amount. More preferably. Thereby, the initial charge / discharge efficiency and the cycle characteristics of the lithium ion secondary battery can be further improved.

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

The polyimide compound according to a particularly preferable embodiment may contain a polymerization component other than (d) a carboxyl group-containing diamine compound and (e) an alicyclic acid anhydride as long as the characteristics of the present invention are not impaired.

The polyimide compound of the present invention can be produced by a conventionally known method using the diamine compound and the acid anhydride. Specifically, it can be obtained by reacting a diamine compound with an acid anhydride to obtain a polyamic acid, and then performing 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%, preferably 0.9 mol%, based on the total amount of the acid anhydride of 1 mol%. More preferably, it is ~ 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 acid anhydride of the present invention and can dissolve the reaction product of the diamine compound and acid anhydride. -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 glycol 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, nail acetate, butyl carbitol acetate, methyl lactate, ethyl lactate, butyl lactate, methyl benzoate, ethyl benzoate, triglime, tetraglyme, acetylacetone, methylpropylketone, methylbutylketone, methylisobutyl 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 preferable in the polyimide.

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

An imidization catalyst may be used during the cyclization dehydration reaction, for example, methylamine, ethylamine, trimethylamine, triethylamine, propylamine, tripropylamine, butylamine, tributylamine, tert-butylamine, hexylamine, triethanolamine, etc. N, N-dimethylethanolamine, N, N-diethylethanolamine, triethylenediamine, N-methylpyrrolidin, N-ethylpyrrolidin, aniline, benzylamine, toluidine, trichloroaniline, pyridine, colidin, lutidine, picolin, quinoline, isoquinolin , Valerolactone and the like can be used.
If necessary, an azeotropic dehydrating agent such as toluene, xylene, or ethylcyclohexane, and an acid catalyst such as acetic anhydride, propionic anhydride, butyric anhydride, and 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.
Further, by using maleic anhydride, ethynylphthalic anhydride, methylethynylphthalic anhydride, phenylethynylphthalic anhydride, phenylethynyltrimellitic anhydride, 3- or 4-ethynylaniline, etc., the polyimide compound can be prepared. Double or triple bonds can also be introduced at the ends.

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

Since the composition of the polyimide compound has been described above, the description thereof is omitted 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 the 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 because the volume change of silicon can be effectively prevented.
Examples of the silicon material include alloys of silicon with metals such as silicon particles, tin, nickel, iron, copper, silver, cobalt, manganese and zinc, and compounds of silicon with boron, nitrogen, oxygen and carbon. Be done.
Examples of silicon materials include SiO, SiO ₂ , SiB ₄ , Mg ₂ Si, Ni ₂ Si, CoSi ₂ , NiSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ and Si. ₂ N ₂ O and the like can be mentioned.

As the negative electrode active material, a material other than a silicon material may be used, and examples thereof include metallic lithium, metal oxide, 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 the 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 and includes, for example, carbon black (acetylene black, ketjen black, furnace black, etc.), graphite, carbon fiber, carbon flakes, metal fiber, foil and the like. Be done. Among these, carbon black is preferable, and acetylene black is more preferable. The resin composition may contain two or more kinds 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 as long as the characteristics of the present invention are not impaired, and examples thereof include thickeners and fillers.

(Negative electrode for lithium ion secondary battery)
The negative electrode for a lithium ion secondary battery of the present invention includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, and the negative electrode active material layer is composed of the above resin composition. It is characterized by being done.

The current collector that can be used is not particularly limited, and examples thereof 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 resin composition is dissolved or dispersed on a current collector and drying it.
As the organic solvent, those described above can be used, and from the viewpoint of solubility or dispersibility of the resin composition, N-methyl-2-pyrrolidone, N, N'-dimethylimidazolidinone and γ-butyrolactone Is preferable.
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 including the above-mentioned negative electrode and a positive electrode. Further, in one embodiment, the lithium ion secondary battery of the present invention includes a separator arranged between the negative electrode and the positive electrode.
Hereinafter, each configuration of the lithium ion secondary battery will be described, but since the negative electrode has been described above, the description thereof will be omitted here.

As the positive electrode, those conventionally used for the positive electrode of the lithium ion secondary battery can be appropriately used.
The positive electrode can be produced by applying a resin composition for producing a positive electrode of a lithium ion secondary battery on a current collector and drying it.

The resin composition for producing a positive electrode of a lithium ion secondary battery can include a positive electrode active material and a binder resin. Further, the resin composition for producing a positive electrode of a lithium ion secondary battery may contain the above-mentioned conductive agent and additive.

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

Further, the present invention is not limited to the above, and a lithium foil or the like can be used as the positive electrode.

As the separator, conventionally known ones can be used, and examples thereof include a paper separator, a resin separator such as polyethylene and polypropylene, and a glass fiber separator.

The positive electrode and the negative electrode are arranged in a battery container, and the container is filled with an organic solvent (electric field solution) in which an electrolyte is dissolved. The electrolyte is not particularly limited, for _{example, LiPF 6, LiClO 4, LiBF} 4, LiClF 4, LiAsF 6, LiSbF 6, LiAlO 4, LiAlCl 4, CF 3 SO 3 Li, LiN (CF 3 SO 2) ₃ , LiCl, LiI and the like can be mentioned.
_{Among these, LiPF 6} , LiClO ₄ and CF ₃ SO ₃ Li are preferable 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.
Specifically, 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, and lactones such as γ-butyl lactone. , Dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, tetrahydropyran, ethers such as 1,4-dioxane, sulfolanes, sulfolanes such as 3-methylsulfolane, dioxolanes such as 1,3-dioxolane, 4-methyl- Ketones such as 2-pentanone, nitriles such as acetonitrile, pyropionitrile, valeronitrile, benzonitrile, halogenated hydrocarbons such as 1,2-dichloroethane, other methylformates, dimethylformamide, diethylformamide, dimethylsulfoxide. , Imidazolium salt, quaternary ammonium salt and other ionic liquids and the like. Further, it may be a mixture of these.
Among these, the carbonate compound is preferable because the solubility of the polyimide compound used for the negative electrode is low and the swelling of the polyimide can be suppressed.

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

(Example 1)
43.25 g (100 mmol) of the diamine compound (BAPS) represented by the following chemical formula and the diamine compound represented by the following chemical formula (100 mmol) in a 500 ml separable flask equipped with a synthetic nitrogen introduction tube for the solvent-soluble polyimide compound A and a stirrer. MBAA) 28.63 g (100 mmol), acid anhydride (BPDA) 58.84 g (200 mmol) represented by the following chemical formula, N-methyl-2-pyrrolidone 700 g, pyridine 3.2 g (40 mmol) and toluene 70 g. Was charged and reacted at 180 ° C. under a nitrogen atmosphere for 8 hours while looking out of the system on the way to obtain a 15 wt% polyimide solution.

(Example 2)
Synthesis of Solvent-Soluble Polyimide Compound B Using the same equipment as in Example 1, BAPS 43.25 g (100 mmol), MBAA 28.63 g (100 mmol), and diamine compound (PHBAAB) 15.22 g (50 mmol) represented by the following chemical formula. ), BPDA 44.13 g (150 mmol), acid anhydride (ODPA) 31.02 g (100 mmol) represented by the following chemical formula, N-methyl-2-pyrrolidone 868 g, pyridine 4.0 g (50 mmol) and toluene 87 g. Was charged and reacted at 180 ° C. under a nitrogen atmosphere for 9 hours while looking out of the system on the way to obtain a 15 wt% polyimide solution.

(Example 3)
Synthesis of Solvent-Soluble Polyimide Compound C Using the same equipment as in Example 1, 28.63 g (100 mmol) of MBAA, 15.22 g (50 mmol) of PHBAAB, and 29.23 g of diamine compound (TPE-R) represented by the following chemical formula (TPE-R). 100 mmol), 31.02 g (100 mmol) of ODPA, 37.23 g (150 mmol) of 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 was added, and the mixture was reacted at 180 ° C. under a nitrogen atmosphere for 10 hours while looking out of the system on the way to obtain a 15 wt% polyimide solution.

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

(Comparative Example 1)
Synthesis of Solvent-Soluble Polyimide Compound a Using the same equipment as in Example 1, BAPS 43.25 g (100 mmol), CpODA 38.44 g (100 mmol), N-methyl-2-pyrrolidone 442 g, pyridine 1.6 g (20 mmol). And 44 g of toluene was added, and the mixture was reacted at 180 ° C. under a nitrogen atmosphere for 12 hours while looking out of the system on the way to obtain a 15 wt% polyimide solution.

(Comparative Example 2)
Synthesis of solvent-soluble polyimide compound b Using the same equipment as in Example 1, DABz 15.22 g (100 mmol), CpODA 38.44 g (100 mmol), N-methyl-2-pyrrolidone 284 g, pyridine 1 represented by the following chemical formulas. .6 g (20 mmol) and 28 g of toluene were added and reacted at 180 ° C. under a nitrogen atmosphere for 10 hours while looking out of the system on the way to obtain a 15 wt% polyimide solution.

<< Measurement of elastic modulus >>
The solutions obtained in the above Examples and Comparative Examples were applied onto a 10 cm square glass plate by a spin coating method, and dried at 100 ° C. for 0.5 hours, 200 ° C. for 0.5 hours, and 250 ° C. for 1 hour. did. Then, it was peeled off from the glass plate and cut to obtain a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 15 μm.
The elastic modulus of this test piece was measured in the MD direction and the TD direction at a tensile speed of 10 mm / min using a tensile tester (manufactured by Shimadzu Corporation, trade name: AG-Xplus 50 kN). The average values of the elastic modulus in the MD direction and the elastic modulus in the TD direction were calculated, and the measurement results are summarized in Table 1.

<< Tensile strength measurement >>
A sample was prepared by the same method as when measuring the elastic modulus, and the tensile strength of this test piece was measured using a tensile tester (manufactured by Shimadzu Corporation, trade name: AG-Xplus 50 kN) at a tensile speed of 10 mm / min. The tensile strength in the MD direction and the TD direction was measured. The average values of elastic modulus in the MD direction and 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, acetylene black (manufactured by Denka Co., Ltd., Li-400) and carbon fiber (Showa Denko) as conductive agents. VGCF-H manufactured by Denko KK) was mixed with the following composition to prepare a resin composition for producing a negative electrode of a lithium ion secondary battery. A resin composition for producing a negative electrode of a lithium ion secondary battery was prepared in the same manner except that the solvent-soluble polyimide compound A was changed to the solvent-soluble polyimide compound obtained in the other Examples and Comparative Examples.
(Composition of Resin Composition for Fabricing Negative Electrode of Lithium Ion Secondary Battery)
-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

An electrolytic copper foil having a thickness of 10 μm was prepared as a current collector for the negative electrode, and a resin composition for producing a negative electrode of a lithium ion secondary battery prepared as described above was applied to the surface of the electrolytic copper foil, and dried to obtain a thickness of 50 μm. A negative electrode active material layer was formed to obtain a negative electrode.

A lithium foil as a positive electrode, ethylene carbonate and ethyl methyl carbonate as an electrolytic solution, and a polyolefin single-layer separator (Celguard Co., Ltd., Celguard (registered trademark) 2500) were prepared to prepare 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 of 25 ° C. Then, the performance test of the lithium ion secondary battery was carried out in an environment of 25 ° C. The test method is 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 up to 5 mV with a current density equivalent to 0.1 C, then switch to CV (constant voltage) charging at 5 mV, charge until the current density is equivalent to 0.01 C, and then equivalent to 0.1 C. Two cycles of CC discharge to 1.2 V at the current density of 1 are performed at 25 ° C., and the ratio of 0.1C discharge capacity B in the first cycle to the charge capacity A equivalent to 0.1C in the first cycle at this time is the first time. The charge / discharge efficiency was calculated based on the formula of initial charge / discharge efficiency (%) = (B / A) × 100, and the results are summarized in Table 2.

<< Cycle characterization >>
The cycle characteristics were measured by the following method. After two cycles of initial charge / discharge efficiency measurement, CC (constant current) charging is performed up to 5 mV with a current density equivalent to 0.2 C, then switching to CV (constant voltage) charging at 5 mV, and a current density equivalent to 0.02 C. After charging until it becomes, CC discharge to 1.2V with a current density equivalent to 0.2C is performed for 3 cycles at 25 ° C., and then CC (constant current) charging is performed to 5mV with a current density equivalent to 0.5C. Then, switch to CV (constant voltage) charging at 5 mV, charge until the current density is equivalent to 0.05 CC, and then CC discharge to 1.2 V at a current density equivalent to 0.5 C at 25 ° C. 30 cycles were performed, and the discharge capacity equivalent to 0.5C at the 30th cycle at this time was defined as C. The cycle characteristics were calculated based on the formula ΔC (%) = (C / B) × 100, and the results are summarized in Table 2.

Claims (10)

1. A solvent-soluble polyimide used as an electrode material for lithium-ion secondary batteries.
   It is a reaction product of a carboxyl group-containing diamine and an acid anhydride.
   A solvent-soluble polyimide compound having an elastic modulus of 3.4 GPa or more.
2. The solvent-soluble polyimide compound according to claim 1, wherein the carboxyl group-containing diamine compound is represented by the following general formula (1) or (2).
   

   

   (In the 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 integers of 1 to 5, respectively. Is.)
3. The solvent-soluble polyimide compound according to claim 1 or 2, which contains an aromatic diamine compound as a polymerization component.
4. The solvent-soluble polyimide compound according to any one of claims 1 to 3, which contains the diamine compound represented by the following general formula (3) as the aromatic diamine compound.
   

   

   (Formula (3) in, R 2 _~ R ₉ are each independently hydrogen, fluorine, selected from the group consisting of substituted or unsubstituted alkyl group and a substituted or unsubstituted aromatic group, R ₂ ~ At _{least one of R 9} is an aromatic group.)
5. The solvent-soluble polyimide according to any one of claims 1 to 4, which is a reaction product of (a) a carboxyl group-containing diamine compound, (b) an aromatic diamine compound, and (c) an aromatic acid anhydride. Compound.
6. The solvent-soluble polyimide compound according to claim 5, wherein the aromatic acid anhydride (c) is represented by the following general formula (4).
   

   

   (In the 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.)
7. The solvent-soluble polyimide compound according to any one of claims 1 to 4, which is a reaction product of (d) a carboxyl group-containing diamine compound and (e) an alicyclic acid anhydride.
8. A resin composition for producing a negative electrode of a lithium ion secondary battery, which comprises the solvent-soluble polyimide compound according to any one of claims 1 to 7 and a negative electrode active material.
9. A negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector are provided.
   A negative electrode for a lithium ion secondary battery, wherein the negative electrode active material layer is composed of the resin composition for producing a negative electrode for a lithium ion secondary battery according to claim 8.
10. A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to claim 9 and a positive electrode.