Polyimide, composition, electrode, and lithium ion secondary battery

Abstract

This polyimide is a product of a reaction between a diamine compound represented by general formula (1) and an acid anhydride represented by general formula (2).

Description

Polyimide, composition, electrode, and lithium ion secondary battery

[0001] The present disclosure relates to a polyimide, a composition, an electrode, and a lithium-ion secondary battery.

[0002] Lithium-ion secondary batteries are lightweight and have a higher capacity than nickel-cadmium and nickel-metal hydride batteries, and are therefore widely used as power sources for mobile electronic devices such as smartphones. In recent years, they have also become increasingly popular as power sources for hybrid and electric vehicles.

[0003] The electrodes of lithium-ion secondary batteries are formed from a current collector and an active material layer, and the active material layer generally contains a resin composition (also called a binder). Polyimide is used as a compound contained in the resin composition because of its excellent properties such as insulating properties, mechanical strength, dimensional stability, easy formability, and light weight (see, for example, Japanese Patent No. 6240798).

[0004] In response to recent demands for further performance improvements in lithium-ion secondary batteries, various performance characteristics are also being sought for the resin compositions. For example, an active material layer is formed by applying a composition containing a resin composition to the surface of a current collector and heating the applied composition at high temperatures. However, such heating may damage the current collector. Therefore, in order to obtain a resin composition that can form an active material layer by low-temperature heating, polyimides having a low glass transition temperature (e.g., 195°C or lower) are required. Furthermore, for example, from the viewpoint of suppressing peeling between the current collector and the active material layer, resin compositions that can suppress swelling of the active material layer are required, and polyimides having at least one of high tensile strength and elastic modulus are required.

[0005] The problem to be solved by the present disclosure is to provide (1) a polyimide having a low glass transition temperature (e.g., 195°C or lower) or (2) a polyimide having at least one of high tensile strength and elastic modulus. Note that the polyimide may be one that can solve either problem (1) or problem (2), but is not required to solve both problems.

[0006] One embodiment of the present disclosure includes the following aspects.

[0007] <1> A polyimide which is a reaction product of a diamine compound represented by the following general formula (1) and an acid anhydride represented by the following general formula (2):

[0008]

[0009] (In general formula (1), R １ ~R ４ is a hydrogen atom, and R ５ ~R ８ At least one of R is an aromatic group having 6 to 10 carbon atoms, a phenoxy group, a benzyl group, or a benzyloxy group, and the other R ５ ~R ８ is a hydrogen atom.)

[0010]

[0011] (In general formula (2), E １ and E ２ is an ester bond, and Z １ and Z ２ each independently represents a single bond, a substituted alkyl group, or an unsubstituted alkyl group; W １ and W ２ are each independently an oxygen atom, a substituted nitrogen atom, or an unsubstituted nitrogen atom, and R' is a substituted alkylene group, an unsubstituted alkylene group, a group represented by the following general formula (3), or a group represented by the following general formula (3'):

[0012]

[0013] (In general formula (3), Z ３ is a single bond, a substituted or unsubstituted alkylene group, Z ４ and Z ５ are each independently a substituted or unsubstituted alkyl group, o and p are each independently 0 or an integer of 1 to 4, *1 is E １ *2 is the bond with E ２ It is the joint with

[0014]

[0015] (In general formula (3'), Z ６ and Z ７ are each independently a substituted or unsubstituted alkyl group, and *1 is E １ *2 is the bond with E ２ It is the joint with

[0016] <2> The polyimide according to <1>, which is a reaction product of a diamine compound represented by the general formula (1) and an acid anhydride represented by the general formula (2), in which R′ is a substituted or unsubstituted alkylene group.

[0017] <3> The polyimide according to <2>, wherein R′ in the general formula (2) is an unsubstituted alkylene group having 1 to 5 carbon atoms.

[0018] <4> In the above general formula (2), Z １ and Z ２ is a single bond, and W １ and W ２ is a nitrogen atom having a substituent.

[0019] <5> The polyimide according to <2>, which is a reaction product of a diamine compound represented by the above general formula (1), an acid anhydride represented by the above general formula (2), in which R′ in the above general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, and a diamine compound represented by the following formula (4):

[0020]

[0021] <6> The polyimide according to <5>, which is a reaction product of a diamine compound represented by the general formula (1), an acid anhydride represented by the general formula (2), in which R′ in the general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, a diamine compound represented by the formula (4), and an acid anhydride represented by the following general formula (5):

[0022] (In general formula (5), X represents a carbonyl group, an oxygen atom, or a single bond.)

[0023] <7> The polyimide according to <1>, which is a reaction product of a diamine compound represented by the above general formula (1), and an acid anhydride represented by the above general formula (2), wherein R' in the general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3'):

[0024] <8> In the general formula (3), Z ３ <7> The polyimide according to <7>, wherein: is a single bond; and o and p are 0.

[0025] <9> In the general formula (3′), Z ６ and Z ７ is a branched alkyl group having 1 to 10 carbon atoms and having no substituent.

[0026] <10> The polyimide according to any one of <1> to <9>, which is a reaction product of a diamine compound represented by the above general formula (1), an acid anhydride represented by the above general formula (2), in which R' in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, and an acid anhydride represented by the above general formula (2), in which R' in general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3'):

[0027] <11> The polyimide according to any one of <1> to <10>, which is soluble in a solvent.

[0028] <12> A composition comprising the polyimide according to any one of <1> to <10> and a solvent.

[0029] <13> The composition according to <12>, which is used for producing an electrode.

[0030] <14> An electrode comprising a current collector and an active material layer, wherein the active material layer contains the polyimide according to any one of <1> to <10>.

[0031] <15> A lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode or the negative electrode is the electrode according to <14>.

[0032] According to one embodiment of the present disclosure, it is possible to provide (1) a polyimide having a low glass transition temperature (for example, 195° C. or less) or (2) a polyimide having at least one of high tensile strength and modulus of elasticity.

[0033] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after the term are included as the upper and lower limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, in this disclosure, "mass %" and "wt %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0034] [Polyimide] The polyimide of the present disclosure is a reaction product of a diamine compound represented by the following general formula (1) and an acid anhydride represented by the following general formula (2): Note that the reaction product may be a reaction product of a diamine compound of the diamine compound represented by the general formula (1), an acid anhydride of the acid anhydride represented by the general formula (2), and a diamine compound other than the diamine compound represented by the general formula (1), and / or an acid anhydride other than the acid anhydride represented by the general formula (2).

[0035]

[0036] In general formula (1), R １ ~R ４ is a hydrogen atom, and R ５ ~R ８ At least one of R is an aromatic group having 6 to 10 carbon atoms, a phenoxy group, a benzyl group, or a benzyloxy group, and the other R ５ ~R ８ is a hydrogen atom.

[0037]

[0038] In general formula (2), E １ and E ２ is an ester bond, and Z １ and Z ２ each independently represents a single bond, a substituted alkyl group, or an unsubstituted alkyl group; W １ and W ２ are each independently an oxygen atom, a substituted nitrogen atom, or an unsubstituted nitrogen atom, and R' is a substituted alkylene group, an unsubstituted alkylene group, a group represented by the following general formula (3), or a group represented by the following general formula (3'):

[0039]

[0040] In general formula (3), Z ３ is a single bond, a substituted or unsubstituted alkylene group, Z ４ and Z ５ are each independently a substituted or unsubstituted alkyl group, o and p are each independently 0 or an integer of 1 to 4, *1 is E １ *2 is the bond with E ２ This is the junction with

[0041]

[0042] In general formula (3'), Z ６ and Z ７ are each independently a substituted or unsubstituted alkyl group, and *1 is E １ *2 is the bond with E ２ This is the junction with

[0043] When the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1) and an acid anhydride represented by general formula (2), where R' is a substituted or unsubstituted alkylene group, a resin composition capable of forming an active material layer by low-temperature heating can be obtained by incorporating this polyimide into a resin composition. It is presumed that the above-mentioned effects are achieved by the polyimide, which can maintain a low glass transition temperature. Furthermore, the polyimide of the present disclosure maintains properties such as heat resistance even when the glass transition temperature is low, and can maintain high cycle characteristics even when used in electrodes for lithium-ion secondary batteries. When the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1) and an acid anhydride represented by general formula (2), where R' is a group represented by general formula (3) or a group represented by general formula (3'), a resin composition capable of suppressing swelling of the active material layer can be obtained. It is presumed that the polyimide has at least one of excellent elastic modulus and tensile strength, which suppresses swelling of the active material layer. Furthermore, when the polyimide of the present disclosure is used in an electrode of a lithium ion secondary battery, high cycle characteristics can be maintained.

[0044] (Regarding General Formula (1)) In General Formula (1), R ５ ~R ８ Preferably, one or two of R are aromatic groups having 6 to 10 carbon atoms, ５ and R ７ It is more preferable that at least one of R is an aromatic group having 6 to 10 carbon atoms, ７ is more preferably an aromatic group having 6 to 10 carbon atoms. In the present disclosure, the term "aromatic group" includes a substituent bonded to the main skeleton via an oxygen atom, a nitrogen atom, or a carbon atom. Furthermore, the aromatic group includes a heteroaromatic group such as a pyrrole group.

[0045] Examples of aromatic groups having 6 to 10 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, an aminophenyl group, a nitrophenyl group, a nitrobenzyl group, a cyanophenyl group, a cyanobenzyl group, a phenethyl group, a phenylpropyl group, a phenylamino group, a diphenylamino group, a biphenyl group, a naphthyl group, a phenylnaphthyl group, a diphenylnaphthyl group, an anthryl group, and an anthrylphenyl group. Examples of aromatic groups include a phenyl group, a phenylanthryl group, a naphthacenyl 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 aromatic groups listed above, a phenyl group and a methylphenyl group are preferred in terms of availability of starting materials and synthesis costs.

[0046] The polyimide of the present disclosure may be a polyimide obtained by using two or more diamine compounds represented by general formula (1).

[0047] Specifically, a preferred diamine compound satisfying general formula (1) is 2-phenyl-4-aminophenyl-4-aminobenzoate, which is a compound represented by the following formula (6). Use of this diamine compound can improve the solvent solubility, melt moldability, and other properties of the resulting polyimide. It can also improve the cycle characteristics of the battery.

[0048]

[0049] The diamine compound represented by general formula (1) can be obtained by reacting a compound represented by the following formula (7) with a compound represented by the following formula (8), and then reducing the nitro group.

[0050]

[0051]

[0052] In the above formula, R １ ~R ４ , and R ５ ~R ８ is the same as defined in the above general formula (1). Y represents a hydroxyl group or a halogen group selected from a fluoro group, a chloro group, a bromo group, and an iodo group. From the viewpoint of reactivity with the compound represented by general formula (8), Y is preferably a halogen group, and more preferably a chloro group or a bromo group.

[0053] When Y in general formula (7) is a hydroxyl group, the reaction between the compound represented by general formula (7) and the compound represented by general formula (8) is preferably carried out in the presence of a dehydration condensation agent such as N,N'-dicyclohexylcarbodiimide (DCC), an organic acid catalyst such as p-toluenesulfonic acid, etc. Furthermore, when Y in general formula (7) is a halogen group, the reaction between the compound represented by general formula (7) and the compound represented by general formula (8) is preferably carried out in the presence of an acid acceptor such as triethylamine.

[0054] Specifically, a compound represented by the following formula (9) can be reacted with a compound represented by the following formula (10) to obtain a diamine compound represented by the above formula (6).

[0055]

[0056]

[0057] The compound represented by general formula (8) can be obtained by nitrating a commercially available or synthesized compound represented by the following formula (11). The nitration of the compound represented by the following formula (11) can be carried out by a conventionally known nitration method using a mixed acid of concentrated sulfuric acid and concentrated nitric acid, nitric acid, fuming nitric acid, an alkali metal salt of an acid in concentrated sulfuric acid, acetyl nitrate, a nitronium salt, a nitrogen oxide, or the like. ５ ~R ８ is the same as defined in the above general formula (1).

[0058]

[0059] From the viewpoints of heat resistance, mechanical strength, cycle characteristics, etc., the content of the amine compound represented by general formula (1) relative to the diamine component constituting the polyimide is preferably 25 mol% or more, more preferably 40 mol% to 100 mol%, and even more preferably 45 mol% to 90 mol%.

[0060] (Regarding General Formula (2)) In General Formula (2), E １ and E ２ is an ester bond. The CO moiety in the ester bond is Z １ and Z ２ Even if placed next to １ or Z ２ -CO-O-R'), may be located on the R' side (Z １ or Z ２ -O-CO-R'), Z １ and Z ２ It is preferably located to the side.

[0061] In general formula (2), Z １ and Z ２are each independently a single bond, an alkyl group having a substituent, or an alkyl group having no substituent, and preferably a single bond. The number of carbon atoms in the alkyl group is preferably 1 to 10, and more preferably 1 to 3. 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 the substituent 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, a propylamino group, etc. Examples of the substituent include 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, a sulfonic acid group, etc.

[0062] In general formula (2), W １ and W ２are each independently an oxygen atom, a nitrogen atom having a substituent, or a nitrogen atom having no substituent, and are preferably an oxygen atom or a nitrogen atom having a substituent. Examples of the substituent include 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, and a sulfonic acid group. Among these, an alkyl group is preferred, an alkyl group having 1 to 6 carbon atoms is more preferred, and an alkyl group having 1 to 3 carbon atoms is even more preferred. In one embodiment, the nitrogen atom having an alkyl group is a nitrogen atom having a methyl group or an ethyl group. In general formula (2), when R' is an alkylene group having a substituent, an alkylene group having no substituent, or a group represented by general formula (3'), W １ and W ２ In the general formula (2), when R′ is a group represented by the general formula (3), W １ and W ２ is preferably an oxygen atom.

[0063] In general formula (2), R' is an alkylene group having a substituent, an alkylene group having no substituent, a group represented by general formula (3), or a group represented by general formula (3'), and is preferably an alkyl group having no substituent, a group represented by general formula (3), or a group represented by general formula (3'). From the viewpoint of keeping the glass transition temperature of the polyimide low, R' is preferably an alkylene group having no substituent. From the viewpoint of tensile strength and elastic modulus, the number of carbon atoms in the alkylene group is preferably 1 to 5, more preferably 1 to 3, even more preferably 1 or 2, and particularly preferably 2. Examples of substituents that the alkylene group may have include alkyl groups, halogen groups such as fluoro groups and chloro groups, amino groups, nitro groups, hydroxyl groups, cyano groups, carboxyl groups, and sulfonic acid groups.

[0064] (Regarding general formula (3)) In general formula (3), Z ３represents a single bond, an alkylene group having a substituent, or an alkylene group having no substituent, and is preferably a single bond. The alkylene group is preferably the same as the alkylene group in R'.

[0065] In general formula (3), Z ４ and Z ５ are each independently a substituted or unsubstituted alkyl group. １ and Z ２ The same alkyl groups as those in the above are preferred.

[0066] In the general formula (3), o and p each independently represent 0 or an integer of 1 to 4, and are preferably 0 from the viewpoint of reactivity.

[0067] (Regarding general formula (3')) In general formula (3'), Z ６ and Z ７ are each independently a substituted or unsubstituted alkyl group, preferably an unsubstituted alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 7, and even more preferably 1 to 5. The alkyl group may be linear or branched, but is preferably branched. Examples of the substituent include halogen groups such as a fluoro group or a chloro group, an amino group, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, and a sulfonic acid group. Examples of the alkyl group 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, and an n-decyl group. Among these, an isopropyl group or a tert-butyl group is preferred.

[0068] The polyimide of the present disclosure may be a polyimide obtained by using two or more acid anhydrides represented by general formula (2). From the viewpoints of glass transition temperature, flexibility, etc., the sum of the contents of the acid anhydrides represented by general formula (2) in which R' is a substituted alkylene group and R' is an unsubstituted alkylene group relative to the acid anhydride components constituting the polyimide is preferably 30 mol% or more, more preferably 35 mol% to 100 mol%, and even more preferably 40 mol% to 80 mol%. From the viewpoints of tensile strength, elastic modulus, etc., the sum of the contents of the acid anhydrides represented by general formula (2) in which R' is a group represented by general formula (3) and a group represented by general formula (3') relative to the acid anhydride components constituting the polyimide is preferably 5 mol% or more, more preferably 10 mol% to 60 mol%, and even more preferably 20 mol% to 50 mol%.

[0069] Examples of the acid anhydride represented by general formula (2) include, but are not limited to, the following compounds:

[0070]

[0071] (TAHQ)

[0072]

[0073]

[0074] (TMPBP-TME)

[0075] (BPADA)

[0076] (Regarding General Formula (4)) The polyimide of the present disclosure may contain a diamine compound represented by the following formula (4) as a constituent component. By configuring the polyimide in this manner, the glass transition temperature tends to be further reduced. In addition, the cycle characteristics of the battery can be improved.

[0077]

[0078] The diamine compound represented by the formula (4) includes three types in which the amino groups are located at the ortho, meta, and para positions, and among these three types, diamine compounds having amino groups at the meta and para positions can be preferably used. Specifically, 1,3-bis(3-aminophenoxy)benzene (APB-N) or 1,3-bis(4-aminophenoxy)benzene (TPE-R) represented by the following formula can be preferably used.

[0079]

[0080]

[0081] The polyimide of the present disclosure may be a polyimide obtained by using two or more diamine compounds represented by formula (4). From the viewpoints of glass transition temperature and adhesion, the content of the diamine compound represented by formula (4) relative to the diamine components constituting the polyimide is preferably 15 mol% or more, more preferably 20 mol% to 80 mol%, and even more preferably 35 mol% to 60 mol%.

[0082] (Regarding General Formula (5)) The polyimide of the present disclosure may contain an acid anhydride represented by the following general formula (5) as a constituent component. By providing the polyimide with such a structure, the tensile strength and elastic modulus can be further improved, and the solvent solubility of the polyimide tends to be improved. In addition, the cycle characteristics of the battery can be improved.

[0083]

[0084] In general formula (5), X represents a carbonyl group, an oxygen atom, or a single bond. Among the acid anhydrides represented by general formula (5), 3,4,3',4'-benzophenonetetracarboxylic dianhydride (BTDA) in which X is a carbonyl group, 4,4'-oxydiphthalic anhydride (ODPA) in which X is an oxygen atom, and diphenyl-3,3',4,4'-tetracarboxylic dianhydride (BPDA) in which X is a single bond can be preferably used. From the viewpoints of tensile strength and elastic modulus, ODPA or BPDA are preferred. From the viewpoint of solvent solubility, BPDA is preferred.

[0085] The polyimide of the present disclosure may be a polyimide obtained by using two or more acid anhydrides represented by general formula (5). From the viewpoints of tensile strength, elastic modulus, and solvent solubility, the content of the acid anhydride represented by formula (5) relative to the acid anhydride components constituting the polyimide is preferably 30 mol% or more, more preferably 35 mol% to 80 mol%, and even more preferably 40 mol% to 70 mol%.

[0086] (Other Diamine Compounds) The polyimide of the present disclosure may contain, as a constituent component, a diamine compound other than the diamine compound represented by general formula (1) and the diamine compound represented by formula (4). Examples of other diamine compounds include 5,5'-methylenebis(2-aminobenzoic acid) (MBAA), paraphenylenediamine (PPD), metaphenylenediamine (MPDA), 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 2,5-dimethyl-1,4-phenylenediamine (DMPDA), 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 2,2-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diaminobiphenyl ... , 4'-diaminodiphenylmethane (MDA), 2,2-bis-(4-aminophenyl)propane, 3,3'-diaminodiphenyl sulfone (33DDS), 4,4'-diaminodiphenyl sulfone (44DDS), 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,4-diaminodiphenyl ether (m-DADE), 4,4'-diaminodiphenyl ether (p-DADE), 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 1,3-bis(3-aminophenoxy)benzene (APB), 1,3-bis(4-aminophenoxy) Examples of the bis(aminophenoxy)phenyl include, but are not limited to, 1,4-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]sulfone (BAPSM), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 3,3-diamino-4,4-dihydroxydiphenylsulfone (ABPS), hydroxybenzidine (HAB), 2-bis(3-aminophenyl)1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)1,1,1,3,3,3-hexafluoropropane, and 9,9-bis(4-aminophenyl)fluorene.These diamine compounds may be used alone or in combination of two or more.

[0087] (Other Acid Anhydrides) The polyimide of the present disclosure may contain, as a constituent component, an acid anhydride other than the acid anhydride represented by general formula (2) and the acid anhydride represented by general formula (5). Examples of other acid anhydrides include pyromellitic dianhydride (PMDA), 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3 ',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 4,4'-(hexafluorophenyl) bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride, thiodiphthalic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 9,9-bis[4-(3,4'-dicarboxyphenoxy) Examples of the dianhydride include aromatic tetracarboxylic dianhydrides such as phenyl]fluorene dianhydride, cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofuran tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexylsuccinic dianhydride, and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride, but are not limited to these.These acid anhydrides may be used alone or in combination of two or more.

[0088] (One embodiment of polyimide) In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), in which R' in general formula (2) is a substituted or unsubstituted alkylene group, and a diamine compound represented by formula (4). By reacting the diamine compound and the acid anhydride, the glass transition temperature of the resulting polyimide can be further reduced, and a resin composition capable of forming an active material layer by heating at a low temperature can be obtained.

[0089] In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), in which R' is a substituted or unsubstituted alkylene group, a diamine compound represented by formula (4), and an acid anhydride represented by general formula (5). By reacting the diamine compound and the acid anhydride, the glass transition temperature of the resulting polyimide can be further reduced, thereby obtaining a resin composition that can form an active material layer by heating at a low temperature. Furthermore, the elastic modulus and tensile strength of the polyimide can be improved, thereby obtaining a resin composition that can suppress swelling of the active material layer.

[0090] In one embodiment, a polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), in which R' in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, and an acid anhydride represented by general formula (2), in which R' in general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3'). In one embodiment, a polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), in which R' in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, an acid anhydride represented by general formula (2), in which R' in general formula (2) is a group represented by general formula (3), and an acid anhydride represented by general formula (2), in which R' in general formula (2) is a group represented by general formula (3'). By reacting the diamine compound with the acid anhydride, the glass transition temperature of the resulting polyimide can be kept low, thereby obtaining a resin composition that can form an active material layer by low-temperature heating. Furthermore, the elastic modulus and tensile strength of the polyimide can be improved, thereby obtaining a resin composition that can suppress swelling of the active material layer.

[0091] In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2) in which R′ in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, an acid anhydride represented by general formula (2) in which R′ in general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3′), and a diamine compound represented by formula (4). In one embodiment, the polyimide disclosed herein is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), where R' in general formula (2) is a substituted or unsubstituted alkylene group, an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3), an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3'), and a diamine compound represented by formula (4). By reacting the diamine compound and the acid anhydride, the glass transition temperature of the resulting polyimide can be further reduced, thereby obtaining a resin composition that can form an active material layer by low-temperature heating. Furthermore, the elastic modulus and tensile strength of the polyimide can be improved, thereby obtaining a resin composition that can suppress swelling of the active material layer.

[0092] In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2) in which R′ in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent, an acid anhydride represented by general formula (2) in which R′ in general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3′), a diamine compound represented by formula (4), and an acid anhydride represented by general formula (5). In one embodiment, the polyimide disclosed herein is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), where R' in general formula (2) is a substituted or unsubstituted alkylene group, an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3), an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3'), a diamine compound represented by formula (4), and an acid anhydride represented by general formula (5). By reacting the diamine compound and the acid anhydride, the glass transition temperature of the resulting polyimide can be further reduced, thereby obtaining a resin composition that can form an active material layer by low-temperature heating. Furthermore, the elastic modulus and tensile strength of the polyimide can be improved, thereby obtaining a resin composition that can suppress swelling of the active material layer.

[0093] In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3) or a group represented by general formula (3'), and a diamine compound represented by formula (4). In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3), an acid anhydride represented by general formula (2), where R' in general formula (2) is a group represented by general formula (3'), and a diamine compound represented by formula (4). By reacting the diamine compound and the acid anhydride, the glass transition temperature of the resulting polyimide can be further reduced, thereby making it possible to obtain a resin composition that can form an active material layer by heating at a low temperature. Furthermore, since the elastic modulus and tensile strength of the polyimide can be improved, a resin composition capable of suppressing swelling of the active material layer can be obtained.

[0094] In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), wherein R' in general formula (2) is a group represented by general formula (3) or a group represented by general formula (3'), a diamine compound represented by formula (4), and an acid anhydride represented by general formula (5). In one embodiment, the polyimide of the present disclosure is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), wherein R' in general formula (2) is a group represented by general formula (3), an acid anhydride represented by general formula (2), wherein R' in general formula (2) is a group represented by general formula (3'), a diamine compound represented by formula (4), and an acid anhydride represented by general formula (5). By reacting the diamine compound with the acid anhydride, the glass transition temperature of the resulting polyimide can be further reduced, thereby obtaining a resin composition that can form an active material layer by heating at a low temperature. In addition, the elastic modulus and tensile strength of the polyimide can be further improved, thereby obtaining a resin composition that can suppress swelling of the active material layer.

[0095] (Physical Properties of Polyimide) The polyimide of the present disclosure is preferably solvent-soluble. In the present disclosure, "solvent-soluble" means that 5 g or more of the polyimide is dissolved in 100 g of an organic solvent. When the polyimide is solvent-soluble, it can be easily formed into a film by dissolving the polyimide in an appropriate organic solvent to form a composition.

[0096] The glass transition temperature (Tg) of the polyimide of the present disclosure is preferably 195°C or lower, more preferably 190°C or lower, even more preferably 185°C or lower, particularly preferably 180°C or lower, and most preferably 178°C or lower. The lower limit of Tg is not particularly limited, but can be, for example, 150°C or higher. Tg is measured by the following method. First, a solution containing the polyimide of the present disclosure and an organic solvent is applied to a 10 cm square glass plate and dried at 250°C for 1 hour. The plate is then peeled off from the glass plate to obtain a test piece (3 mm x 3 mm x (20 μm±3 μm)) weighing 3 mg. The glass transition temperature (Tg) of each test piece thus obtained was measured using a DSCQ200 (trade name) manufactured by TA Instruments Japan, Inc., under a nitrogen gas flow at a heating rate of 10°C / min.

[0097] The tensile strength of the polyimide of the present disclosure is preferably 100 MPa or more, more preferably 105 MPa or more, even more preferably 110 MPa or more, particularly preferably 115 MPa or more, and most preferably 120 MPa or more. The upper limit of the tensile strength is not particularly limited, and can be, for example, 300 MPa or less. The tensile strength is measured by cutting a solution containing the polyimide of the present disclosure and an organic solvent into a test piece measuring 10 mm x 80 mm x (20 μm ± 3 μm), using a tensile tester (e.g., Shimadzu EZ-SX (trade name), chuck distance 50 mm) at a pulling rate of 10 mm / min, and the average value of the tensile strengths for n=3 is calculated as the tensile strength.

[0098] The elastic modulus of the polyimide of the present disclosure is preferably 3.15 GPa or more, more preferably 3.20 GPa or more, even more preferably 3.30 GPa or more, particularly preferably 3.50 GPa or more, and most preferably 3.70 GPa or more. The upper limit of the tensile strength is not particularly limited, and can be, for example, 10.00 GPa or less. The elastic modulus is measured by cutting a solution containing the polyimide of the present disclosure and an organic solvent into a test piece measuring 10 mm x 80 mm x (20 μm ± 3 μm), using a tensile tester (e.g., Shimadzu Corporation's EZ-SX (trade name), chuck distance 50 mm), at a tension speed of 10 mm / min, and calculating the average value of the elastic modulus for n=3.

[0099] The weight average molecular weight (Mw) of the polyimide of the present disclosure is preferably 20,000 to 100,000, and more preferably 50,000 to 95,000. Mw is measured using a high performance liquid chromatograph.

[0100] The imide group concentration of the polyimide of the present disclosure is preferably 25% or less, more preferably 24% or less, and even more preferably 23% or less. This allows the glass transition temperature of the polyimide to be further lowered. Furthermore, the imide group concentration is preferably 10% or more, more preferably 13% or more, and even more preferably 15% or more. This allows swelling to be further suppressed.

[0101] The imide group concentration is calculated using the following method. First, the molecular weight A of the smallest unit of polyimide is calculated. For example, in Comparative Example 1 described below, (PHBAAB)-(ODPA)-(APB-N)-(ODPA) is the smallest unit, and its molecular weight is calculated by subtracting the molecular weight of the water molecules generated from the total molecular weight of these compounds. In Comparative Example 1, four water molecules are generated, so the following formula is 18.02 x 4. Molecular weight of smallest unit = (304.35 + 292.34 + (310.22 x 2)) - (18.02 x 4) = 1217.13 - 72.08 = 1145.05

[0102] Next, the molecular weight of the imide group, 70.03, is multiplied by the number of water molecules generated when the minimum unit is produced to obtain B. This is because imide groups are formed at the sites where water molecules are generated. The above A and B are substituted into the following formula to measure the imide group concentration: Imide group concentration = B / A In the above Comparative Example 1, the result is 70.03 x 4 / 1145.05 = 24.46%.

[0103] (Uses of Polyimide) The polyimide of the present disclosure can be contained in a resin composition used to form an active material layer of a positive electrode or a negative electrode included in a lithium ion secondary battery, or can be contained in a resin composition used to form a coating on the surface of a separator included in a lithium ion secondary battery.

[0104] [Method for Producing Polyimide] The polyimide of the present disclosure can be obtained by reacting a diamine compound with an acid anhydride to obtain a polyamic acid, and then converting the polyamic acid into a polyimide by a cyclization dehydration reaction.

[0105] The mixing ratio of the diamine compound and the acid anhydride is preferably such that the total amount of the diamine compound is 0.5 mol % to 1.5 mol %, more preferably 0.9 mol % to 1.1 mol %, per 1 mol % of the total amount of the acid anhydride.

[0106] The reaction of the diamine compound with 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 and can dissolve the reaction product of the diamine compound and the acid anhydride, and examples thereof include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N'-dimethylimidazolidinone, γ-butyrolactone, dimethyl sulfoxide, sulfolane, 1,3-dioxolane, tetrahydrofuran, 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, methyl lactate, ethyl lactate, butyl lactate, methyl benzoate, ethyl benzoate, triglyme, tetraglyme, toluene, and xylene. From the viewpoint of the solubility of the diamine compound, N-methyl-2-pyrrolidone, N,N'-dimethylimidazolidinone, and γ-butyrolactone are preferred.

[0107] The reaction temperature between the diamine compound and the acid anhydride is preferably 40°C or lower in the case of chemical imidization, and is preferably 150°C to 220°C, more preferably 170°C to 200°C in the case of thermal imidization.

[0108] An imidization catalyst may be used during the cyclization dehydration reaction. Examples of suitable catalysts include 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, and valerolactone. 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, may be used. Furthermore, a capping agent such as benzoic acid, phthalic anhydride, or hydrogenated phthalic anhydride may be used in the reaction of a diamine compound with an acid anhydride. Furthermore, a double bond or a triple bond can be introduced into the terminal of the polyimide by using maleic anhydride, ethynylphthalic anhydride, methylethynylphthalic anhydride, phenylethynylphthalic anhydride, phenylethynyltrimellitic anhydride, 3- or 4-ethynylaniline, or the like.

[0109] [Composition] The composition of the present disclosure contains the polyimide of the present disclosure and a solvent. As the solvent, the above-mentioned organic solvents can be used.

[0110] The content of the polyimide of the present disclosure relative to the total mass of the composition of the present disclosure is preferably 1% by mass to 30% by mass, more preferably 3% by mass to 25% by mass, and even more preferably 5% by mass to 20% by mass.

[0111] The composition of the present disclosure may contain other resins. Examples of other resins include polyvinylidene fluoride (PVDF), PVDF copolymer resins, fluororesins, styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), styrene-acrylonitrile copolymers, carboxymethyl cellulose (CMC), and polyimides other than the polyimides of the present disclosure. Examples of PVDF copolymer resins include copolymer resins of PVDF with hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PFMV), or tetrafluoroethylene (TFE). Examples of fluororesins include polytetrafluoroethylene (PTFE), fluororubbers, and the like. Two or more of the above-mentioned other resins may be used in combination.

[0112] The composition of the present disclosure can be used to manufacture an electrode. Specifically, it can be used to form an active material layer on the surface of a current collector. When the composition of the present disclosure is used to form an active material layer, the composition can contain an active material, a conductive material, and the like. The electrode may be a positive electrode or a negative electrode.

[0113] As the negative electrode active material, silicon-based materials and carbon-based materials can be used. Examples of silicon-based 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, and carbon. Examples of carbon-based materials include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, pyrolytic vapor-grown carbon fiber, phenolic resin calcined body, polyacrylonitrile-based carbon fiber, pseudoisotropic carbon, furfuryl alcohol resin calcined body (PFA), hard carbon, natural graphite, and artificial graphite.

[0114] The positive electrode active material is lithium-containing cobalt oxide (LiCoO ２ ), lithium manganese oxide (LiMn ２ O ４ ), lithium-containing nickel oxide (LiNiO ２ ), Co—Ni—Mn lithium-containing composite oxide (Li(CoMnNi)O ２), lithium-containing composite oxide of Ni-Mn-Al, lithium-containing composite oxide of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO ４ ), olivine-type lithium manganese phosphate (LiMnPO ４ ), Li ２ MnO ３ -LiNiO ２ system solid solution, Li １＋ｘ Mn ２－ｘ O ４ (0<X<2) Lithium-excess spinel compound represented by Li[Ni ０．１７ Li ０．２ Co ０．０７ Mn ０．５６ ]O ２ , LiNi ０．５ Mn １．５ O ４ etc.

[0115] Examples of the conductive material include conductive carbon materials such as carbon black (e.g., acetylene black, Ketjenblack (registered trademark), furnace black, etc.), graphite, carbon fiber, carbon flakes, and ultrashort carbon fibers (e.g., carbon nanotubes, vapor-grown carbon fibers, etc.); and fibers and foils of various metals.

[0116] The composition of the present disclosure can be produced by mixing the above-described various components. Mixing may be carried out using a mixer such as a ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, or Filmix.

[0117] [Electrode] The electrode of the present disclosure includes a current collector and an active material layer, and the active material layer contains the polyimide of the present disclosure. The electrode of the present disclosure may be a positive electrode or a negative electrode. The electrode of the present disclosure may contain a positive electrode active material or a negative electrode active material. The electrode of the present disclosure may contain a conductive material. The polyimide, active material, and conductive material of the present disclosure have been described above, so further description will be omitted here.

[0118] The content of the polyimide of the present disclosure relative to the total mass of the active material layer is preferably 5% by mass to 30% by mass, more preferably 7% by mass to 20% by mass, and even more preferably 9% by mass to 15% by mass.

[0119] The thickness of the active material layer is not particularly limited, but may be, for example, 10 μm to 100 μm.

[0120] The current collector can be made of any conventionally known material as long as it is electrically conductive and electrochemically durable. The current collector can be made of one or more materials selected from the group consisting of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, and alloys thereof.

[0121] [Method for Manufacturing an Electrode] The method for manufacturing an electrode according to the present disclosure includes applying the composition according to the present disclosure to the surface of a current collector and drying the composition to form an active material layer. The composition may be applied to one or both surfaces of the current collector. Furthermore, the composition may be applied to the entire surface of the current collector or to a portion of the entire surface.

[0122] Examples of the coating method include a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, and an extrusion method.

[0123] The drying method is not particularly limited and may be a known method, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. From the viewpoint of reducing damage to the current collector, the drying temperature is preferably 195°C or lower, more preferably 170°C or lower, and more preferably 165°C or lower. From the viewpoint of cycle characteristics, the drying temperature is preferably higher than the glass transition temperature of the polyimide, preferably 100°C or higher, more preferably 120°C or higher, and more preferably 130°C or higher. After drying, the electrode may be subjected to a pressure treatment using a mold press or a roll press. Pressure treatment can improve the adhesion between the active material layer and the current collector and increase the density of the active material layer.

[0124] [Lithium-ion secondary battery] The lithium-ion secondary battery of the present disclosure includes a positive electrode, a negative electrode, a separator, and an electrolyte solution, and the positive electrode or the negative electrode is the electrode of the present disclosure.

[0125] (Electrode) The electrode other than the electrode of the present disclosure is not particularly limited, but a known electrode used in the manufacture of lithium ion secondary batteries can be used. Specifically, an electrode formed by forming an electrode mixture layer on a current collector using a known manufacturing method can be used.

[0126] (Electrolyte) As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte of the lithium ion secondary battery, for example, a lithium salt is used. As the lithium salt, for example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among these, LiPF is preferred from the viewpoint of being easily soluble in solvents and exhibiting a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３ Li is preferred, and LiPF ６ is particularly preferred. One type of electrolyte may be used alone, or two or more types may be used in combination in any ratio. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0127] The organic solvent is 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 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 ionic liquids such as other methyl formates, dimethylformamide, diethylformamide, dimethyl sulfoxide, imidazolium salts, and quaternary ammonium salts. Furthermore, mixtures of these may also be used. Among the above, carbonate compounds can be preferably used, which have low solubility in the polyimide of the present disclosure and can suppress swelling.

[0128] (Separator) The separator is not particularly limited, but is preferably a microporous film made of a resin such as polyolefin (polyethylene, polypropylene), polyamide, or polyimide. A heat-resistant separator having a coating layer on one or both sides of the microporous film to enhance the heat resistance of the separator can also be used. The polyimide of the present disclosure can be contained in the resin composition used to form the coating layer.

[0129] [Method for Manufacturing Lithium-Ion Secondary Battery] The lithium-ion secondary battery of the present disclosure can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween and winding the stack as needed according to the battery shape, or by stacking multiple positive electrodes and negative electrodes with a separator sandwiched between them, placing the stacked ...

[0130] The present disclosure will be described below with reference to examples, but the present disclosure is not limited to the following examples. Note that, in the following, "parts" and "%" are all by mass unless otherwise specified.

[0131] Example 1 Into a 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer, 30.44 g (100 mmol) of (2-phenyl-4-aminophenyl)-4-aminobenzoate (PHBAAB), an aromatic diamine compound represented by the formula below, 29.23 g (100 mmol) of 1,3-bis(3-aminophenoxy)benzene (APB-N), an aromatic diamine compound represented by the formula below, 31.02 g (100 mmol) of 4,4′-oxydiphthalic anhydride (ODPA), represented by the formula below, 41.03 g (100 mmol) of ethylene glycol-bis-trimellitic acid ester (TMEG-100), represented by the formula below, 498 g of N-methyl-2-pyrrolidone (NMP), and pyridine were added. 3.16 g (40 mmol) of toluene and 50 g of toluene were added, and the reaction was carried out for 7 hours at 180°C under a nitrogen atmosphere, while removing toluene from the system during the reaction, to obtain a 20% by mass polyimide solution. The imide group concentration of the polyimide in the polyimide solution was determined to be 22.5%. The imide group concentrations were similarly calculated for the polyimides produced in the following Examples and Comparative Examples, and are summarized in Table 1. PHBAAB was synthesized by the method described in the Examples of Japanese Patent No. 6240798, APB-N was manufactured by Mitsui Chemicals, Inc., ODPA was manufactured by Toho Chemical Industry Co., Ltd., and TMEG-100 was manufactured by New Japan Chemical Co., Ltd.

[0132]

[0133]

[0134]

[0135]

[0136] Example 2 30.44 g (100 mmol) of PHBAAB, 29.23 g (100 mmol) of APB-N, 57.05 g (100 mmol) of 2,5-di-tert-butyl-1,4-phenylene bistrimellitate dianhydride (TADBHQ) represented by the following formula, 41.03 g (100 mmol) of TMEG-100, 602.16 g of NMP, 3.16 g (40 mmol) of pyridine, and 60 g of toluene were added to a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer. The mixture was reacted under a nitrogen atmosphere at 180°C for 6 hours while removing toluene from the system during the reaction, thereby obtaining a 20% by mass polyimide solution. The fact that a 20% by mass polyimide solution was obtained indicates that the polyimide contained therein is solvent-soluble. This also applies to the following examples and comparative examples. TADBHQ used was synthesized by the method described in the examples of JP-A No. 2023-2497.

[0137]

[0138] Example 3 A 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 21.30 g (70 mmol) of PHBAAB, 8.77 g (30 mmol) of APB-N, 22.82 g (40 mmol) of TADBHQ, 16.41 g (40 mmol) of TMEG-100, 10.69 g (40 mmol) of biphenyl-4,4′-diyl bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (BP-TME) represented by the following formula, 306 g of NMP, 3.16 g (40 mmol) of pyridine, and 31 g of toluene. The mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing toluene from the system during the reaction, thereby obtaining a 20% by mass polyimide solution. The BP-TME used was manufactured by Honshu Chemical Industry Co., Ltd.

[0139]

[0140] Example 4 A 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 30.44 g (100 mmol) of PHBAAB, 58.47 g (100 mmol) of APB-N, 28.63 g (100 mmol) of 5,5'-methylenebis(2-aminobenzoic acid) (MBAA) represented by the following formula, 62.04 g (200 mmol) of ODPA, 82.06 g (200 mmol) of TMEG-100, 988.92 g of NMP, 6.33 g (80 mmol) of pyridine, and 99 g of toluene. The mixture was reacted under a nitrogen atmosphere at 180°C for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20% by mass polyimide solution. The MBAA used was manufactured by Seika Corporation.

[0141]

[0142] Example 5 30.44 g (100 mmol) of PHBAAB, 41.03 g (100 mmol) of TMEG-100, 271.48 g of NMP, 1.58 g (20 mmol) of pyridine, and 27 g of toluene were placed in a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0143] Example 6 30.44 g (100 mmol) of PHBAAB, 29.23 g (100 mmol) of APB-N, 82.06 g (200 mmol) of TMEG-100, 538.08 g of NMP, 3.16 g (40 mmol) of pyridine, and 54 g of toluene were placed in a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0144] Example 7 30.44 g (100 mmol) of PHBAAB, 11.69 g (40 mmol) of APB-N, 9.13 g (60 mmol) of 3,5-diaminobenzoic acid (DABz) represented by the following formula, 82.06 g (200 mmol) of TMEG-100, 504.44 g of NMP, 3.16 g (20 mmol) of pyridine, and 50 g of toluene were placed in a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing toluene from the system, thereby obtaining a 20% by mass polyimide solution. DABz used was manufactured by Nippon Junryo Chemical Co., Ltd.

[0145]

[0146] Example 8 A 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 42.61 g (140 mmol) of PHBAAB, 17.54 g (60 mmol) of APB-N, 50.06 g (122 mmol) of TMEG-100, 10.69 g (20 mmol) of BP-TME, 17.65 g (60 mmol) of diphenyl-3,3',4,4'-tetracarboxylic dianhydride (BPDA) represented by the following formula, 525.08 g of NMP, 3.2 g (20 mmol) of pyridine, and 53 g of toluene. The mixture was reacted under a nitrogen atmosphere at 180°C for 7 hours while removing the toluene from the system during the reaction, to obtain a 20% by mass polyimide solution. BPDA was used, manufactured by Ube Industries, Ltd.

[0147]

[0148] Example 9 A 20% by mass polyimide solution was obtained in the same manner as in Example 8, except that the monomer composition ratio was changed to the ratio shown in Table 1.

[0149] Example 10 A 20% by mass polyimide solution was obtained in the same manner as in Example 8, except that the monomer composition ratio was changed to the ratio shown in Table 1.

[0150] Example 11 42.61 g (140 mmol) of PHBAAB, 17.54 g (60 mmol) of APB-N, 50.06 g (122 mmol) of TMEG-100, 22.82 g (40 mmol) of TADBHQ, 11.77 g (40 mmol) of BPDA, 550.08 g of NMP, 3.2 g (40 mmol) of pyridine, and 55 g of toluene were placed in a 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0151] Example 12 A 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 19.63 g (64.5 mmol) of PHBAAB, 10.23 g (35 mmol) of APB-N, 24.62 g (30 mmol) of TMEG-100, 24.62 g (60 mmol) of (BP-TME), 8.83 g (30 mmol) of BPDA, 260 g of NMP, 3.16 g (40 mmol) of pyridine, and 26 g of toluene, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0152] Example 13 21.30 g (70 mmol) of PHBAAB, 8.77 g (30 mmol) of APB-N, 22.57 g (55 mmol) of TMEG-100, 8.02 g (15 mmol) of (BP-TME), 8.83 g (30 mmol) of BPDA, 264 g of NMP, 3.16 g (40 mmol) of pyridine, and 26 g of toluene were placed in a 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0153] Comparative Example 1 30.44 g (100 mmol) of PHBAAB, 29.23 g (100 mmol) of APB-N, 62.04 g (200 mmol) of ODPA, 458 g of NMP, 3.16 g (40 mmol) of pyridine, and 46 g of toluene were placed in a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0154] Comparative Example 2 A 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 60.87 g (150 mmol) of bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS) represented by the following formula, 29.42 g (100 mmol) of BPDA, 15.51 g (50 mmol) of ODPA, 418 g of NMP, 2.37 g (30 mmol) of pyridine, and 42 g of toluene, and the mixture was reacted under a nitrogen atmosphere at 180° C. for 7 hours while removing the toluene from the system during the reaction, thereby obtaining a 20 mass % polyimide solution.

[0155]

[0156] <Measurement of Glass Transition Temperature (Tg)> Each polyimide solution obtained in the above Examples and Comparative Examples was applied to a 10 cm square glass plate by spin coating and dried at 250°C for 1 hour. The polyimide solution was then peeled off from the glass plate to obtain a test piece (3 mm x 3 mm x (20 μm±3 μm)) weighing 3 mg. The glass transition temperature (Tg) of each test piece thus obtained was measured using a DSCQ200 (trade name) manufactured by TA Instruments Japan, Inc., under a nitrogen gas flow at a heating rate of 10°C / min. The measurement results are summarized in Table 2.

[0157] <Measurement of 5% Weight Loss Temperature (Td)> Each polyimide solution obtained in the above Examples and Comparative Examples was applied to a 10 cm square glass plate by spin coating and dried at 250°C for 1 hour. Thereafter, a test piece measuring 3 mm x 3 mm x (20 μm±3 μm) and weighing 5 mg was peeled off from the glass plate. In accordance with JIS K 7120, the 5% weight loss temperature of the test piece was measured in air at a heating rate of 10°C / min using a TG-DTA (Hitachi High-Tech Science Corporation, product name STA7200R). The measurement results are summarized in Table 2.

[0158] <Measurement of Tensile Strength> Each polyimide solution obtained in the above Examples and Comparative Examples was cut into a test piece measuring 10 mm x 80 mm x (20 μm±3 μm), and the tensile strength was measured at a pulling rate of 10 mm / min using a tensile tester (Shimadzu Corporation, product name: EZ-SX, chuck distance 50 mm). The average tensile strength value for n=3 is shown in Table 2. The tensile strength measurement was carried out in an environment of 23±2°C and a relative humidity of 50±10%.

[0159] <Measurement of Elastic Modulus> Each polyimide solution obtained in the above Examples and Comparative Examples was cut into a test piece measuring 10 mm x 80 mm x (20 μm±3 μm), and the elastic modulus was measured at a tension speed of 10 mm / min using a tensile tester (Shimadzu Corporation, product name: EZ-SX, chuck distance 50 mm). The average value of the elastic modulus for n=3 is shown in Table 2. The elastic modulus measurement was carried out in an environment of 23±2°C and a relative humidity of 50±10%.

[0160] <Measurement of Elongation Percentage> Each polyimide solution obtained in the above Examples and Comparative Examples was cut into a test piece measuring 10 mm x 80 mm x 10 to 50 μm, and elongation was measured at a tension speed of 10 mm / min using a tensile tester (Shimadzu Corporation, product name: EZ-SX, chuck distance 50 mm). The maximum displacement values ​​for n=3 are summarized in Table 2. The elongation percentage (%) was calculated by the formula: displacement (mm) / chuck distance 50 mm x 100. The elongation percentage was measured in an environment of 23±2°C and a relative humidity of 50±10%.

[0161] <Measurement of Coefficient of Thermal Expansion (CTE)> Each polyimide solution obtained in the Examples and Comparative Examples was processed into a film of approximately 20 μm±3 μm, and then cut into a test piece measuring 3 mm × 20 mm. Using a thermal analyzer (TMA6100, manufactured by Hitachi High-Tech Science Corporation), the test piece was heated from room temperature (30°C) to 400°C at a rate of 10°C / min while applying a 5 g weight, and the average coefficient of thermal expansion (CTE) of the test piece from 100°C to 200°C was determined. The results are summarized in Table 2.

[0162] <Measurement of Swelling Ratio> Each polyimide solution obtained in the Examples and Comparative Examples was applied to a glass plate and dried at 160°C for 10 hours to obtain a film with a thickness of approximately 40 μm. A 2 cm x 2 cm test piece was prepared from the film and immersed in an electrolyte solvent consisting of ethylene carbonate: propylene carbonate: dimethyl carbonate = 1:1:1. The electrolyte solvent was heated to 50°C, and the test piece was immersed at 50°C for 72 hours. The weight change of the test piece before and after the immersion treatment was measured, and the weight increase rate (%) was calculated as the swelling ratio, which is summarized in Table 2. Here, the film preparation method does not affect the swelling ratio value. Furthermore, the weight of the film after the immersion treatment was measured after removing the test piece from the electrolyte solvent and quickly wiping off the electrolyte adhering to the surface with a tissue to prevent it from drying.

[0163] <Measurement of Weight Average Molecular Weight (Mw)> Each of the polyimide solutions obtained in the above Examples and Comparative Examples was diluted with NMP, and the weight average molecular weight was measured using a high performance liquid chromatograph (manufactured by Tosoh Corporation).

[0164] [Rule 26 amendment 07.04.2025]

[0165] [Rule 26 amendment 07.04.2025]

[0166] <Evaluation of cycle characteristics> The polyimide (solid content), negative electrode active material (silicon), and conductive material (carbon) contained in each of the polyimide solutions obtained in Examples 1, 4, 5, 7, 11, and 14 were mixed in the following composition to prepare negative electrode compositions for lithium ion secondary batteries: Polyimide 10.0 mass %, Silicon 87.0 mass %, and Conductive agent 3.00 mass %.

[0167] An electrolytic copper foil having a thickness of 10 μm was prepared as a negative electrode current collector, and the negative electrode composition obtained as described above was applied to the surface of the electrolytic copper foil, followed by heat treatment at 160° C. to form a negative electrode active material layer having a thickness of 30 μm, thereby producing a negative electrode for a lithium ion secondary battery.

[0168] A lithium foil was prepared as a positive electrode for a lithium ion secondary battery. 1M LiPF was used as an electrolyte for the lithium ion secondary battery. ６ A mixed solution of ethylene carbonate and ethyl methyl carbonate (mixing ratio 1:1:1 (by mass), containing 1 mass% of VC (vinylene carbonate)) was prepared. A 25 μm thick polyolefin single-layer microporous membrane (Celgard 2325, manufactured by Asahi Kasei Corporation) was prepared as a separator for the lithium ion secondary battery. A coin cell type (R2032 type) lithium ion secondary battery was fabricated using the above negative electrode, positive electrode, electrolyte, and separator in a dry environment with a dew point of −60°C.

[0169] The fabricated lithium-ion secondary battery half-cell was allowed to stand for 24 hours in an environment at 30°C. Thereafter, the discharge capacity retention rate after 30 cycles in an environment at 30°C was determined as follows: CC (constant current) charging was performed to 5 mV at a current density equivalent to a 0.1 C rate, followed by switching to CV (constant voltage) charging at 5 mV, charging to a current density equivalent to a 0.01 C rate, and then CC discharging to 1.2 V at a current density equivalent to a 0.1 C rate. This cycle was repeated for two cycles at 30°C. The discharge capacity equivalent to a 0.1 C rate in the first cycle was designated "A." Next, the battery was subjected to CC (constant current) charging at a current density equivalent to 0.2C rate to 5 mV, then switched to CV (constant voltage) charging at 0.5 mV, and charged to a current density equivalent to 0.02C rate, followed by CC discharging at a current density equivalent to 0.2C rate to 1.2 V. This cycle was repeated three times at 30°C. Subsequently, the battery was subjected to CC (constant current) charging at a current density equivalent to 0.5C rate to 5 mV, then switched to CV (constant voltage) charging at 5 mV, and charged to a current density equivalent to 0.05C rate, followed by CC discharging at a current density equivalent to 0.5C rate to 1.2 V. This cycle was repeated 30 times at 30°C. The discharge capacity equivalent to 0.5C rate at this time was designated "B". From A and B above, the discharge capacity retention rate after 30 cycles was calculated using the following formula and summarized in Table 3. Discharge capacity retention rate after 30 cycles (%) = (B / A) x 100

[0170] [Rule 26 amendment 07.04.2025]

Claims

1. A polyimide which is a reaction product of a diamine compound represented by the following general formula (1) and an acid anhydride represented by the following general formula (2): (In general formula (1), R １ ~R ４ is a hydrogen atom, and R ５ ~R ８ At least one of R is an aromatic group having 6 to 10 carbon atoms, a phenoxy group, a benzyl group, or a benzyloxy group, and the other R ５ ~R ８ is a hydrogen atom.) (In general formula (2), E １ and E ２ is an ester bond, and Z １ and Z ２ each independently represents a single bond, a substituted alkyl group, or an unsubstituted alkyl group; W １ and W ２ are each independently an oxygen atom, a substituted nitrogen atom, or an unsubstituted nitrogen atom, and R' is a substituted alkylene group, an unsubstituted alkylene group, a group represented by the following general formula (3), or a group represented by the following general formula (3'): (In general formula (3), Z ３ is a single bond, a substituted or unsubstituted alkylene group, Z ４ and Z ５ are each independently a substituted or unsubstituted alkyl group, o and p are each independently 0 or an integer of 1 to 4, *1 is E １ *2 is the bond with E ２ It is the joint with (In general formula (3'), Z ６ and Z ７ are each independently a substituted or unsubstituted alkyl group, and *1 is E １ *2 is the bond with E ２ It is the joint with 2. The polyimide according to claim 1, which is a reaction product of a diamine compound represented by general formula (1) and an acid anhydride represented by general formula (2), wherein R' in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent.

3. The polyimide according to claim 2, wherein R' in said general formula (2) is an unsubstituted alkylene group having 1 to 5 carbon atoms.

4. In the general formula (2), Z １ and Z ２ is a single bond, and W １ and W ２ The polyimide according to claim 2 or 3, wherein is a nitrogen atom having a substituent.

5. The polyimide according to claim 2, which is a reaction product of a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2), in which R' is an alkylene group having a substituent or an alkylene group having no substituent, and a diamine compound represented by the following formula (4):

6. The polyimide according to claim 5, which is a reaction product of: a diamine compound represented by general formula (1); an acid anhydride represented by general formula (2) in which R' is an alkylene group having a substituent or an alkylene group having no substituent; a diamine compound represented by formula (4); and an acid anhydride represented by the following general formula (5): (In general formula (5), X represents a carbonyl group, an oxygen atom, or a single bond.) 7. The polyimide according to claim 1, which is a reaction product of a diamine compound represented by the general formula (1) and an acid anhydride represented by the general formula (2), wherein R' in the general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3'):

8. In the general formula (3), Z ３ The polyimide of claim 7 , wherein: is a single bond; and o and p are 0.

9. In the general formula (3'), Z ６ and Z ７ is an unsubstituted branched alkyl group having 1 to 10 carbon atoms.

10. The polyimide according to claim 1 or 2, which is a reaction product of: a diamine compound represented by general formula (1); an acid anhydride represented by general formula (2), in which R' in general formula (2) is an alkylene group having a substituent or an alkylene group having no substituent; and an acid anhydride represented by general formula (2), in which R' in general formula (2) is a group represented by the following general formula (3) or a group represented by the following general formula (3').

11. The polyimide according to claim 1 or claim 2, which is solvent-soluble.

12. A composition comprising the polyimide according to claim 1 or 2, and a solvent.

13. The composition of claim 12 used in the manufacture of an electrode.

14. An electrode comprising a current collector and an active material layer, wherein the active material layer contains the polyimide according to claim 1 or 2.

15. A lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode or the negative electrode is the electrode according to claim 14.

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