Polyimide, composition, electrode, and lithium ion secondary battery

Abstract

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

Description

Technical Field

[0001] This disclosure relates to polyimide, compositions, electrodes, and lithium-ion secondary batteries. Background Technology

[0002] Among rechargeable batteries, lithium-ion batteries are lighter and have a higher capacity compared to nickel-cadmium and nickel-metal hydride batteries, making them 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 a lithium-ion secondary battery are formed by a current collector and an active material layer, which typically contains a resin composition (also known as a binder). Furthermore, polyimide (see Japanese Patent No. 6240798, etc.) is used as a compound in the resin composition due to its excellent properties such as insulation, mechanical strength, dimensional stability, ease of molding, and lightweight.

[0004] With the increasing demand for improved performance of lithium-ion secondary batteries in recent years, various performance requirements are also being placed on the above-mentioned resin compositions.

[0005] For example, an active material layer is formed by coating a composition containing a resin composition onto the surface of a current collector and heating it at a high temperature, but there is a possibility that the current collector may be damaged due to this heating. Therefore, in order to obtain a resin composition that can form an active material layer by heating at a low temperature, a polyimide with a low glass transition temperature (e.g., below 195°C) is required.

[0006] In addition, for example, from the viewpoint of suppressing the peeling of the current collector from the active material layer, there is a need for a resin composition that can suppress the swelling of the active material layer, requiring a polyimide with at least one of high tensile strength and high elastic modulus. Summary of the Invention

[0007] The problem that the invention aims to solve The problem to be solved by this disclosure is to provide a polyimide having (1) a low glass transition temperature (e.g., below 195°C) or (2) a polyimide having at least one of high tensile strength and high modulus of elasticity.

[0008] It should be noted that the polyimide only needs to solve either of the issues in (1) and (2), and does not need to solve both issues.

[0009] Methods for solving problems One embodiment of this disclosure includes the following approach.

[0010] <1> Polyimide, which is The diamine compound represented by the following general formula (1) and The acid anhydride represented by the following general formula (2) The reactants.

[0011] [Chemical Formula 1] (in general formula (1), R1 to R4 are hydrogen atoms. At least one of R5 to R8 is an aromatic group, phenoxy group, benzyl group, or benzyloxy group having 6 to 10 carbon atoms; all other R5 to R8 groups are hydrogen atoms. [Chemical Formula 2] (in general formula (2), E1 and E2 are ester bonds. Z1 and Z2 are each independently a single bond, an alkyl group with substituents, or an alkyl group without substituents. W1 and W2 are each independently an oxygen atom, a nitrogen atom with a substituent, or a nitrogen atom without a substituent. R' is an alkylene group with a substituent, an alkylene group without a substituent, a group represented by the following general formula (3), or a group represented by the following general formula (3'). [Chemical Formula 3] (in general formula (3), Z3 is a single bond, a substituent alkylene group, or an unsubstituent alkylene group. Z4 and Z5 are each independently an alkyl group with or without substituents. o and p are each independently 0 or an integer from 1 to 4. 1 represents the bonding portion with E1. 2 represents the bonding portion with E2. [Chemical Formula 4] (In general formula (3'), Z6 and Z7 are each independently an alkyl group with or without substituents. 1 represents the bonding portion with E1. 2 represents the bonding portion with E2. <2> The polyimide as described in <1> is The diamine compound represented by the above general formula (1), and Represented by the above general formula (2), where R' is an acid anhydride with or without a substituent alkylene group. The reactants.

[0012] <3> The polyimide as described in <2>, wherein in the above general formula (2), R' is an alkylene group with 1 to 5 carbon atoms that does not have substituents.

[0013] <4> Polyimide as described in <2> or <3>, wherein, in the above general formula (2), Z1 and Z2 are single bonds. W1 and W2 are nitrogen atoms with substituents.

[0014] <5> The polyimide described in <2> is... The diamine compound represented by the above general formula (1), Represented by the above general formula (2), where R' is an acid anhydride with or without a substituent alkylene group, and... The diamine compound represented by the following formula (4) The reactants.

[0015] [Chemical Formula 5] <6> As described in <5>, the polyimide is The diamine compound represented by the above general formula (1), Represented by the above general formula (2), where R' is an acid anhydride with or without a substituent alkylene group. The diamine compound represented by formula (4) above, and The acid anhydride represented by the following general formula (5) The reactants.

[0016] [Chemical Formula 6] (in general formula (5), X represents a carbonyl group, an oxygen atom, or a single bond. <7> The polyimide as described in <1> is The diamine compound represented by the above general formula (1), and An acid anhydride represented by the above general formula (2) and in general formula (2) R' is a group represented by the following general formula (3) or a group represented by the following general formula (3'). The reactants.

[0017] <8> The polyimide as described in <7>, wherein, in general formula (3), Z3 is a single bond, o and p are 0.

[0018] <9> Polyimide as described in <7>, wherein, in general formula (3'), Z6 and Z7 are branched alkyl groups with 1 to 10 carbon atoms that do not have substituents.

[0019] <10> The polyimide as described in any one of <1> to <9> is The diamine compound represented by the above general formula (1), Represented by the above general formula (2), where R' is an acid anhydride with or without a substituent alkylene group, and... An acid anhydride represented by the above general formula (2) and in general formula (2) R' is a group represented by the following general formula (3) or a group represented by the following general formula (3'). The reactants.

[0020] <11> The polyimide as described in any one of <1> to <10> is solvent soluble.

[0021] <12> Composition comprising: The polyimide described in any one of <1> to <10>; and Solvent.

[0022] <13> The composition as described in <12> is used in the manufacture of electrodes.

[0023] <14> Electrode, which has a current collector and an active material layer, The above-mentioned active material layer contains any one of the polyimide in <1> to <10>.

[0024] <15> A lithium-ion secondary battery, which comprises a positive electrode, a negative electrode, a separator, and an electrolyte. The above-mentioned positive or negative electrode is the electrode described in <14>.

[0025] The effects of the invention According to one embodiment of this disclosure, it is possible to provide (1) a polyimide having a low glass transition temperature (e.g., below 195°C) or (2) a polyimide having at least one of high tensile strength and elastic modulus. Detailed Implementation

[0026] The present invention will now be described in detail. The description of the constituent elements described below is based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0027] It should be noted that in this specification, the "~" sign indicating a numerical range is used to include the values ​​listed before and after it as the lower and upper limits.

[0028] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced by the upper or lower limit of another numerical range described in other periods. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit of that range can be replaced by the values ​​shown in the embodiments.

[0029] In addition, in this publication, "mass%" and "weight%" have the same meaning, and "parts of mass" and "parts of weight" have the same meaning.

[0030] Furthermore, in this disclosure, a combination of two or more preferred methods is a more preferred method.

[0031] [Polyimide] The polyimide in this 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).

[0032] It should be noted that the reactants are diamine compounds represented by general formula (1), acid anhydrides represented by general formula (2), diamine compounds other than those represented by general formula (1), and / or acid anhydrides other than those represented by general formula (2).

[0033] [Chemical Formula 7] In general formula (1), R1 to R4 are hydrogen atoms. At least one of R5 to R8 is an aromatic group, phenoxy group, benzyl group, or benzyloxy group having 6 to 10 carbon atoms, and the other R5 to R8 groups are hydrogen atoms.

[0034] [Chemical Formula 8] In general formula (2), E1 and E2 are ester bonds. Z1 and Z2 are each independently a single bond, an alkyl group with substituents, or an alkyl group without substituents. W1 and W2 are each independently an oxygen atom, a nitrogen atom with a substituent, or a nitrogen atom without a substituent. R' is an alkylene group with a substituent, an alkylene group without a substituent, a group represented by the following general formula (3), or a group represented by the following general formula (3'). [Chemical Formula 9] In general formula (3), Z3 is a single bond, a substituent alkylene group, or an unsubstituent alkylene group. Z4 and Z5 are each independently an alkyl group with or without substituents. o and p are each independently 0 or an integer from 1 to 4. 1 represents the bonding portion with E1. 2 is the bonding part with E2.

[0035] [Chemical Formula 10] In general formula (3'), Z6 and Z7 are each independently an alkyl group with or without substituents. 1 represents the bonding portion with E1. 2 is the bonding part with E2.

[0036] In this disclosure, when the polyimide is a diamine compound represented by general formula (1) reacting with an acid anhydride represented by general formula (2) where R' is a substituent alkylene group or an unsubstituent alkylene group, by incorporating this polyimide into a resin composition, a resin composition in which an active material layer can be formed by low-temperature heating can be obtained. It is speculated that, based on the above-described polyimide, the glass transition temperature can be suppressed to a lower level, thus achieving the aforementioned effect.

[0037] Furthermore, according to the polyimide disclosed above, even with a low glass transition temperature, it can maintain properties such as heat resistance, and when used as an electrode in a lithium-ion secondary battery, it can also maintain high cycle characteristics.

[0038] When the polyimide in this disclosure is a reaction product of a diamine compound represented by general formula (1) and an anhydride represented by general formula (2) and R' being a group represented by general formula (3) or a group represented by general formula (3'), a resin composition capable of suppressing the swelling of the active material layer can be obtained. It is presumed that the above-mentioned polyimide has at least one of excellent elastic modulus and tensile strength, and therefore can suppress the swelling of the active material layer.

[0039] Furthermore, when the polyimide described in this disclosure is used as an electrode in a lithium-ion secondary battery, high cycle performance can be maintained.

[0040] (Regarding general formula (1)) In general formula (1), preferably one or two of R5 to R8 are aromatic groups with 6 to 10 carbon atoms, more preferably at least one of R5 and R7 is an aromatic group with 6 to 10 carbon atoms, and even more preferably R7 is an aromatic group with 6 to 10 carbon atoms.

[0041] In this disclosure, "aromatic groups" include substituents that are bonded to the main skeleton via oxygen, nitrogen, or carbon atoms. Furthermore, aromatic groups include heteroaromatic groups such as pyrrole groups.

[0042] Examples of aromatic groups having 6 to 10 carbon atoms include phenyl, tolyl, methylphenyl, dimethylphenyl, ethylphenyl, diethylphenyl, propylphenyl, butylphenyl, fluorophenyl, pentafluorophenyl, chlorophenyl, bromophenyl, methoxyphenyl, dimethoxyphenyl, ethoxyphenyl, diethoxyphenyl, aminophenyl, nitrophenyl, nitrobenzyl, cyanophenyl, cyanobenzyl, phenethyl, phenylpropyl, phenylamino, diphenylamino, biphenyl, naphthyl, phenylnaphthyl, and diphenyl Naphthyl, anthracene, anthracene phenyl, phenyl anthracene, tetraphenyl, phenanthrene, phenanthrene phenyl, phenylphenanthrene, pyrene, phenyl pyrene, fluorenyl, phenyl fluorenyl, naphthyl ethyl, naphthyl propyl, anthracene ethyl, phenanthrene ethyl, or pyrrole, imidazolyl, thiazolyl, oxazolyl, furanyl, thiophene, triazolyl, pyrazolyl, isoxazolyl, isothiazolyl, pyridinyl, pyrimidinyl, benzofuranyl, benzothiophene, quinolinyl, isoquinolinyl, indolyl, benzothiazolyl, carbazole, and other heteroaromatic groups, etc.

[0043] Among the aromatic groups mentioned above, phenyl and methylphenyl are preferred in terms of the availability of starting materials and synthesis cost.

[0044] The polyimide in this disclosure can be a polyimide obtained by using two or more diamine compounds represented by general formula (1).

[0045] As a diamine compound satisfying the general formula (1), specifically, 4-aminobenzoic acid (2-phenyl-4-aminophenyl) ester, which is represented by the following formula (6), is preferably used.

[0046] By using this diamine compound, the solvent solubility and melt moldability of the obtained polyimide can be improved. Furthermore, the cycle characteristics of the battery can be enhanced.

[0047] [Chemical Formula 11] The diamine compound represented by general formula (1) can be obtained by reducing the nitro group after reacting the compound represented by formula (7) with the compound represented by formula (8).

[0048] [Chemical Formula 12] [Chemical Formula 13] In the above formula, R1 to R4 and R5 to R8 are defined in the same way as in the general formula (1). In addition, Y represents a hydroxyl group or a halogen group selected from fluorine, chlorine, bromine and iodine groups.

[0049] From the viewpoint of reactivity with compounds represented by general formula (8), Y is preferably a halogen group, more preferably a chlorine group or a bromine group.

[0050] In general formula (7), when Y is a hydroxyl group, the reaction of the compound represented by general formula (7) with the compound represented by general formula (8) is preferably carried out in the presence of a dehydrating condensing agent such as N,N'-dicyclohexylcarbodiimide (DCC) and an organic acid catalyst such as p-toluenesulfonic acid.

[0051] In addition, when Y is a halogen group in general formula (7), 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-binding agent such as triethylamine.

[0052] Specifically, by reacting the compound represented by formula (9) with the compound represented by formula (10), the diamine compound represented by formula (6) can be obtained.

[0053] [Chemical Formula 14] [Chemical Formula 15] The compound represented by general formula (8) can be obtained commercially or by nitrating the synthesized compound represented by formula (11) below. The nitration of the compound represented by formula (11) below can be carried out by conventionally known nitration methods using a mixture of concentrated sulfuric acid and concentrated nitric acid, nitric acid, fuming nitric acid, acid-base metal salts in concentrated sulfuric acid, acetyl nitrate, nitonium salts, nitrogen oxides, etc. It should be noted that R5 to R8 in the formula have the same definition as in the above general formula (1).

[0054] [Chemical Formula 16] From the viewpoint of heat resistance, mechanical strength, and cycle characteristics, 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%.

[0055] (Regarding general formula (2)) In general formula (2), E1 and E2 are ester bonds.

[0056] The CO portion of the ester bond can be disposed on the Z1 and Z2 sides (Z1 or Z2-CO-O-R') or on the R' side (Z1 or Z2-O-CO-R'), preferably on the Z1 and Z2 sides.

[0057] In general formula (2), Z1 and Z2 are each independently a single bond, an alkyl group with a substituent or an alkyl group without a substituent, preferably both being single bonds.

[0058] The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 3.

[0059] Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, sec-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl, trichloromethyl, bromomethyl, dibromomethyl, tribromomethyl, fluoroethyl, difluoroethyl, trifluoroethyl, chloroethyl, dichloroethyl, trichloroethyl, bromoethyl, dibromoethyl, tribromoethyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, sec-pentoxy, n-hexoxy, cyclohexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, trifluoromethoxy, methylamino, dimethylamino, trimethylamino, ethylamino, propylamino, etc.

[0060] Examples of substituents include halogen groups such as alkyl, fluorine, and chloro groups, as well as amino, nitro, hydroxyl, cyano, carboxyl, and sulfonic acid groups.

[0061] In general formula (2), W1 and W2 are each independently an oxygen atom, a nitrogen atom with a substituent or a nitrogen atom without a substituent, preferably an oxygen atom or a nitrogen atom with a substituent.

[0062] Examples of substituents include halogen groups such as alkyl, fluorine, and chloro groups, as well as amino, nitro, hydroxyl, cyano, carboxyl, and sulfonic acid groups. Among these, alkyl groups are preferred, alkyl groups with 1 to 6 carbon atoms are more preferred, and alkyl groups with 1 to 3 carbon atoms are even more preferred.

[0063] In one embodiment, the nitrogen atom having an alkyl group is a nitrogen atom having a methyl or ethyl group.

[0064] In general formula (2), when R' is an alkylene group with a substituent, an alkylene group without a substituent, or a group represented by general formula (3'), W1 and W2 are preferably nitrogen atoms with a substituent.

[0065] In general formula (2), when R' is a group represented by general formula (3), W1 and W2 are preferably oxygen atoms.

[0066] In general formula (2), R' is an alkylene group with a substituent, an alkylene group without a substituent, a group represented by general formula (3) or a group represented by general formula (3'), preferably an alkyl group without a substituent, a group represented by general formula (3) or a group represented by general formula (3').

[0067] From the viewpoint of suppressing the glass transition temperature of polyimide to a low level, R' is preferably an alkylene group without substituents.

[0068] 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, further preferably 1 or 2, and particularly preferably 2.

[0069] Examples of substituents that can be present in alkylene groups include alkyl, halogen groups such as fluorine and chloro groups, amino, nitro, hydroxy, cyano, carboxyl, and sulfonic acid groups.

[0070] (Regarding general formula (3)) In general formula (3), Z3 is a single bond, an alkylene group with a substituent or an alkylene group without a substituent, preferably a single bond.

[0071] Regarding the alkylene group, it is preferably the same group as the alkylene group in R'.

[0072] In general formula (3), Z4 and Z5 are each independently an alkyl group with substituents or an alkyl group without substituents.

[0073] Regarding alkyl groups, the preferred group is the same as the alkyl group in Z1 and Z2.

[0074] In general formula (3), o and p are each independently 0 or integers from 1 to 4. From the point of view of reactivity, 0 is preferred.

[0075] (Regarding the general formula (3')) In general formula (3'), Z6 and Z7 are each independently an alkyl group with or without a substituent, preferably an alkyl group without a substituent.

[0076] The alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 7, and even more preferably 1 to 5.

[0077] Alkyl groups can be straight-chain or branched, preferably branched.

[0078] Examples of substituents include halogen groups such as fluorine and chlorine, as well as amino, nitro, hydroxyl, cyano, carboxyl, and sulfonic acid groups.

[0079] Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, sec-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl, among which isopropyl or tert-butyl is preferred.

[0080] The polyimide in this disclosure can be a polyimide obtained by using two or more acid anhydrides represented by general formula (2).

[0081] From the viewpoint of glass transition temperature, softness, etc., the sum of the contents of anhydrides represented by general formula (2) and R' being a substituted alkylene group and R' being an unsubstituted alkylene group relative to the anhydride component constituting polyimide is preferably 30 mol% or more, more preferably 35 mol% to 100 mol%, and even more preferably 40 mol% to 80 mol%.

[0082] From the viewpoint of tensile strength, elastic modulus, etc., the sum of the contents of the anhydrides represented by general formula (2) and R' being general formula (3) and general formula (3') relative to the anhydride component 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%.

[0083] Examples of acid anhydrides represented by general formula (2) include, but are not limited to, the following compounds.

[0084] [Chemical Formula 17] [Chemical Formula 18] [Chemical Formula 19] [Chemical Formula 20] [Chemical Formula 21] [Chemical Formula 22] (Regarding general formula (4)) The polyimide disclosed herein may contain a diamine compound represented by formula (4) as a constituent component. By making the polyimide of this composition, there is a tendency to suppress the glass transition temperature to be lower. In addition, the cycle characteristics of the battery can be improved.

[0085] [Chemical Formula 23] As a diamine compound represented by the above formula (4), three types of diamine compounds can be described, namely, those with amino groups at the ortho, meta, and para positions. Among these three types, diamine compounds with amino groups at the meta and para positions are preferred. Specifically, 1,3-bis(3-aminophenoxy)benzene (APB-N) or 1,3-bis(4-aminophenoxy)benzene (TPE-R) represented by the following formula are preferred.

[0086] [Chemical Formula 24] [Chemical Formula 25] The polyimide in this disclosure can be a polyimide obtained by using two or more diamine compounds represented by formula (4).

[0087] From the viewpoint of glass transition temperature and sealing properties, the content of the diamine compound represented by formula (4) relative to the diamine component 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%.

[0088] (Regarding general formula (5)) The polyimide disclosed herein may contain an anhydride represented by the following general formula (5) as a constituent component. By making the polyimide with this composition, there is a tendency to further improve the tensile strength and elastic modulus, and to improve the solvent solubility of the polyimide. In addition, the cycle characteristics of the battery can be improved.

[0089] [Chemical Formula 26] In general formula (5), X represents a carbonyl group, an oxygen atom, or a single bond.

[0090] Among the anhydrides represented by general formula (5), 3,4,3',4'-benzophenone tetracarboxylic dianhydride (BTDA) with X as a carbonyl group, 4,4'-oxydiphthalic anhydride (ODPA) with X as an oxygen atom, and diphenyl-3,3',4,4'-tetracarboxylic dianhydride (BPDA) with X as a single bond are preferred.

[0091] From the perspective of tensile strength and elastic modulus, ODPA or BPDA are preferred.

[0092] From the perspective of solvent solubility, BPDA is preferred.

[0093] The polyimide in this disclosure can be a polyimide obtained by using two or more acid anhydrides represented by general formula (5).

[0094] From the viewpoint of tensile strength, elastic modulus and solvent solubility, the content of the anhydride represented by formula (5) relative to the anhydride component 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%.

[0095] (Other diamine compounds) The polyimide disclosed herein may contain diamine compounds other than those represented by general formula (1) and diamine compounds represented by formula (4) as its constituent components.

[0096] Examples of other diamine compounds include 5,5'-methylenebis(2-aminobenzoic acid) (MBAA), p-phenylenediamine (PPD), m-phenylenediamine (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, and 3,3'-dimethoxy-4,4'-diaminobiphenyl. 2,2-Bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-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)benzene (TPE-R), 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-dihydroxydiphenyl sulfone (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, 9,9-bis(4-aminophenyl)fluorene, etc., but not limited to these. These diamine compounds can be used alone or in combination of two or more.

[0097] (Other acid anhydrides) The polyimide disclosed herein may contain anhydrides other than those represented by general formula (2) and general formula (5) as its constituent components.

[0098] Other examples of 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, and 2,3,3',4'-benzophenonetetracarboxylic dianhydride. 3,3',4,4'-benzophenone tetracarboxylic 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 (B PADA), 4,4'-(hexafluoroisopropylidene) phthalic anhydride, bis(3,4-dicarboxyphenyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl) sulfoxide dianhydride, thiodiphthalic anhydride, 3,4,9,10-perylenetetracarboxylic anhydride, 2,3,6,7-anthracitetetracarboxylic anhydride, 1,2,7,8-phenanthrenetetracarboxylic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 9,9-bis[4- Aromatic tetracarboxylic dianhydrides such as (3,4'-dicarboxyphenoxy)phenyl]fluorene dianhydride, cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexylsuccinic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride, etc., but not limited to these. These anhydrides can be used alone or in combination of two or more.

[0099] (An embodiment of polyimide) In one embodiment, the polyimide of this disclosure is: a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2) in which R' is a substituent alkylene group or an unsubstituent alkylene group, and a reactant with the diamine compound represented by formula (4).

[0100] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a lower level, thus enabling the formation of a resin composition with an active material layer through low-temperature heating.

[0101] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2) in which R' is a substituent alkylene group or an alkylene group without substituents, a diamine compound represented by formula (4), and a reactant with an acid anhydride represented by general formula (5).

[0102] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a lower level, thus enabling the formation of a resin composition with an active material layer through low-temperature heating.

[0103] In addition, it can improve the elastic modulus and tensile strength of polyimide, thus obtaining a resin composition that can suppress the swelling of the active material layer.

[0104] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a substituent alkylene group or an alkylene group without substituents, or a reactant of an anhydride represented by general formula (2) in which R' is a group represented by general formula (3) or a group represented by general formula (3').

[0105] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a substituent alkylene group or an alkylene group without substituents, an anhydride represented by general formula (2) in which R' is a group represented by general formula (3), and a reactant with an anhydride represented by general formula (2) in which R' is a group represented by general formula (3').

[0106] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a low level, thus enabling the formation of an active material layer by low-temperature heating of a resin composition.

[0107] In addition, it can improve the elastic modulus and tensile strength of polyimide, thus obtaining a resin composition that can suppress the swelling of the active material layer.

[0108] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a substituent alkylene group or an unsubstituent alkylene group, an anhydride represented by general formula (2) in which R' is a group represented by general formula (3) or a group represented by general formula (3'), and a reactant of a diamine compound represented by formula (4).

[0109] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a substituent alkylene group or an unsubstituent alkylene group, an anhydride represented by general formula (2) in which R' is a group represented by general formula (3), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3'), and a reactant of a diamine compound represented by formula (4).

[0110] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a lower level, thus enabling the formation of a resin composition with an active material layer through low-temperature heating.

[0111] In addition, it can improve the elastic modulus and tensile strength of polyimide, thus obtaining a resin composition that can suppress the swelling of the active material layer.

[0112] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a substituent alkylene group or an unsubstituent alkylene group, an anhydride represented by general formula (2) in which R' is a group represented by general formula (3) or a group represented by general formula (3'), a diamine compound represented by formula (4), and a reactant with an anhydride represented by general formula (5).

[0113] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a substituent alkylene group or an unsubstituent alkylene group, an anhydride represented by general formula (2) in which R' is a group represented by general formula (3), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3'), a diamine compound represented by formula (4), and a reactant with an anhydride represented by general formula (5).

[0114] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a lower level, thus enabling the formation of a resin composition with an active material layer through low-temperature heating.

[0115] In addition, it can improve the elastic modulus and tensile strength of polyimide, thus obtaining a resin composition that can suppress the swelling of the active material layer.

[0116] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an acid anhydride represented by general formula (2) in which R' is a group represented by general formula (3) or a group represented by general formula (3'), and a reactant of a diamine compound represented by formula (4).

[0117] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3'), and a reactant of a diamine compound represented by formula (4).

[0118] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a lower level, thus enabling the formation of a resin composition with an active material layer through low-temperature heating.

[0119] In addition, it can improve the elastic modulus and tensile strength of polyimide, thus obtaining a resin composition that can suppress the swelling of the active material layer.

[0120] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3) or a group represented by general formula (3'), a diamine compound represented by formula (4), and a reactant with an anhydride represented by general formula (5).

[0121] In one embodiment, the polyimide of this disclosure is a diamine compound represented by general formula (1), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3), an anhydride represented by general formula (2) in which R' is a group represented by general formula (3'), a diamine compound represented by formula (4), and a reactant with an anhydride represented by general formula (5).

[0122] By reacting the above-mentioned diamine compound with the acid anhydride, the glass transition temperature of the obtained polyimide can be suppressed to a lower level, thus enabling the formation of a resin composition with an active material layer through low-temperature heating.

[0123] Furthermore, since the elastic modulus and tensile strength of polyimide can be further improved, a resin composition that can suppress the swelling of the active material layer can be obtained.

[0124] (Physical properties of polyimide) The polyimide in this disclosure is preferably solvent-soluble. In this disclosure, "solvent-soluble" means that more than 5g can be dissolved in 100g of an organic solvent.

[0125] When polyimide is solvent-soluble, it can be easily film-formed by preparing a composition that is soluble in a suitable organic solvent.

[0126] The glass transition temperature (Tg) of the polyimide disclosed herein is preferably below 195°C, more preferably below 190°C, and even more preferably below 185°C. It is particularly preferred to be below 180°C, and most preferably below 178°C.

[0127] There is no specific limit to the lower limit of Tg; for example, it can be set to above 150℃.

[0128] Tg was determined by the following method.

[0129] First, a solution containing the polyimide and organic solvent disclosed herein was coated onto a 10 cm square glass plate and dried at 250°C for 1 hour. Then, the plate was peeled off to obtain a test piece (3 mm × 3 mm × (20 μm ± 3 μm)) weighing 3 mg. For each test piece obtained in this manner, the glass transition temperature (Tg) was determined using a DSCQ200 (trade name) manufactured by TA Instruments Japan Co., Ltd., under a nitrogen flow, at a heating rate of 10°C / min.

[0130] The tensile strength of the polyimide disclosed herein is preferably 100 MPa or more, more preferably 105 MPa or more, and even more preferably 110 MPa or more. The tensile strength is particularly preferred to be 115 MPa or higher, and most preferably 120 MPa or higher. There is no particular upper limit to the tensile strength; for example, it can be set to 300 MPa or lower.

[0131] Regarding tensile strength, a test piece with dimensions of 10 mm × 80 mm × (20 μm ± 3 μm) is prepared from a solution of polyimide and organic solvent containing the present disclosure. The tensile strength is measured using a tensile testing machine (e.g., Shimadzu EZ-SX (trade name), clamp distance 50 mm) at a tensile speed of 10 mm / min. The average tensile strength of the three samples is then taken as the tensile strength.

[0132] The elastic modulus of the polyimide disclosed herein is preferably 3.15 GPa or higher, more preferably 3.20 GPa or higher, and even more preferably 3.30 GPa or higher. Particularly preferred is 3.50 GPa or higher, and most preferred is 3.70 GPa or higher. There is no particular upper limit to the tensile strength; for example, it can be set to 10.00 GPa or lower.

[0133] Regarding the elastic modulus, a test piece with dimensions of 10 mm × 80 mm × (20 μm ± 3 μm) is prepared from a solution of polyimide and organic solvent containing the present disclosure. The tensile strength is measured using a tensile testing machine (e.g., Shimadzu EZ-SX (trade name), clamp distance 50 mm) at a tensile speed of 10 mm / min. The average elastic modulus of the three samples is then used as the elastic modulus.

[0134] The weight-average molecular weight (Mw) of the polyimide in this disclosure is preferably 20,000 to 100,000, more preferably 50,000 to 95,000.

[0135] Mw was determined using high performance liquid chromatography.

[0136] The polyimide in this disclosure preferably has an imide group concentration of 25% or less, more preferably 24% or less, and even more preferably 23% or less. This allows for a further reduction in the glass transition temperature of the polyimide.

[0137] Furthermore, the concentration of imide groups is preferably 10% or more, more preferably 13% or more, and even more preferably 15% or more. This further suppresses swelling.

[0138] The concentration of imide groups is calculated using the following method.

[0139] First, the molecular weight A of the smallest unit of polyimide is calculated. For example, in Comparative Example 1 described later, (PHBAAB)-(ODPA)-(APB-N)-(ODPA) is the smallest unit. The molecular weight of the smallest unit is obtained by subtracting the molecular weight of the generated water molecules from the total molecular weight of these compounds. It should be noted that in Comparative Example 1, since four water molecules are generated, the molecular weight in the following formula is 18.02 × 4.

[0140] The molecular weight of the smallest unit = (304.35 + 292.34 + (310.22 × 2)) - (18.02 × 4) = 1217.13 - 72.08 = 1145.05 Next, the molecular weight of the imide group is set to 70.03, multiplied by the number of water molecules produced when the aforementioned smallest unit is formed, as B. This is because the imide group is formed in the portion where water molecules are generated.

[0141] Substitute A and B into the following formula to determine the concentration of imide groups.

[0142] Imide concentration = B / A In Comparative Example 1 above, 70.03 × 4 / 1145.05 = 24.46%.

[0143] (Uses of polyimide) The polyimide disclosed herein may be contained in a resin composition for forming an active material layer, which is the active material layer of the positive or negative electrode of a lithium-ion secondary battery.

[0144] Alternatively, it may be included in the resin composition used to form the coating, which is a coating on the surface of the separator of a lithium-ion secondary battery.

[0145] [Manufacturing method of polyimide] The polyimide disclosed herein can be obtained by reacting a diamine compound with an acid anhydride to obtain polyamic acid, followed by a cyclization and dehydration reaction to convert it into polyimide.

[0146] Regarding the mixing ratio of the diamine compound and the acid anhydride, the total amount of the diamine compound is preferably set to 0.5 mol% to 1.5 mol% relative to 1 mol% of the total amount of the acid anhydride, and more preferably 0.9 mol% to 1.1 mol%.

[0147] The reaction of diamine compounds with acid anhydrides 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 reactants of the diamine compound and the acid anhydride. Examples include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N'-dimethylimidazolinone, γ-butyrolactone, dimethyl sulfoxide, sulfolane, 1,3-dioxane, 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, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, toluene, xylene, etc. From the viewpoint of the solubility of diamine compounds, N-methyl-2-pyrrolidone, N,N'-dimethylimidazolinone, and γ-butyrolactone are preferred.

[0148] Regarding the reaction temperature of the diamine compound with the acid anhydride, in the case of chemical imidization, it is preferably below 40°C. Furthermore, in the case of thermal imidization, it is preferably 150°C to 220°C, more preferably 170°C to 200°C.

[0149] In cyclization dehydration reactions, imidization catalysts can be used, such as 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, toluene, trichloroaniline, pyridine, trimethylpyridine, dimethylpyridine, methylpyridine, quinoline, isoquinoline, and valerol. Alternatively, azeotropic dehydrating agents such as toluene, xylene, and ethylcyclohexane, as well as acid catalysts such as acetic anhydride, propionic anhydride, butyric anhydride, and benzoic anhydride can be used as needed.

[0150] In addition, in the reaction of diamine compounds with acid anhydrides, end-capping agents such as benzoic acid, phthalic anhydride, and hydrogenated phthalic anhydride can be used.

[0151] Alternatively, double or triple bonds can be introduced into the ends of polyimides by using maleic anhydride, ethynyl phthalic anhydride, methyl ethynyl phthalic anhydride, phenyl ethynyl phthalic anhydride, phenyl ethynyl trimellitic anhydride, 3- or 4-ethynyl aniline, etc.

[0152] [Composition] The compositions disclosed herein comprise the polyimide and solvent of the present disclosure.

[0153] The organic solvents mentioned above can be used as solvents.

[0154] The content of polyimide in this disclosure relative to the total mass of the composition of this disclosure is preferably 1% to 30% by mass, more preferably 3% to 25% by mass, and even more preferably 5% to 20% by mass.

[0155] The compositions disclosed herein may contain other resins.

[0156] Other resins include polyvinylidene fluoride (PVDF), PVDF copolymer resins, fluorinated resins, styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), styrene-acrylonitrile copolymers, carboxymethyl cellulose (CMC), and polyimides other than the polyimides described in this disclosure.

[0157] Examples of PVDF copolymer resins include hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PFMV), or copolymer resins of tetrafluoroethylene (TFE) and PVDF.

[0158] Examples of fluorinated resins include polytetrafluoroethylene (PTFE) and fluororubber.

[0159] Other resins can be used in combination with two or more of the above-mentioned types.

[0160] The compositions disclosed herein can be used in the manufacture of electrodes. Specifically, they can be used to form an active material layer on the surface of a current collector.

[0161] When the composition of this disclosure is used in the formation of the active material layer, the composition may contain active material, conductive material, etc.

[0162] It should be noted that the electrode can be either positive or negative.

[0163] Silicon-based materials and carbon-based materials can be used as negative electrode active materials.

[0164] Examples of silicon-based materials include silicon particles, alloys of metals such as tin, nickel, iron, copper, silver, cobalt, manganese, and zinc with silicon, as well as compounds of silicon such as boron, nitrogen, oxygen, and carbon.

[0165] Examples of carbon-based materials include coke, mesophase carbon microspheres (MCMB), mesophase pitch-based carbon fibers, thermally decomposed vapor-deposited carbon fibers, phenolic resin sintered bodies, polyacrylonitrile-based carbon fibers, quasi-isotropic carbon, furfuryl alcohol resin sintered bodies (PFA), hard carbon, natural graphite, and artificial graphite.

[0166] Examples of positive electrode active materials include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), Co-Ni-Mn lithium composite oxide (Li(CoMnNi)O2), Ni-Mn-Al lithium composite oxide, Ni-Co-Al lithium composite oxide, olivine-type lithium iron phosphate (LiFePO4), olivine-type lithium manganese phosphate (LiMnPO4), Li2MnO3-LiNiO2 solid solutions, and Li... 1+x Mn 2-x O4 (0 < X ​​< 2) represents lithium-excess spinel compounds, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4, etc.

[0167] Examples of conductive materials include carbon black (e.g., acetylene black, Ketjen black (registered trademark), furnace black, etc.), graphite, carbon fiber, carbon sheet, carbon ultrashort fiber (e.g., carbon nanotube, vapor-deposited carbon fiber, etc.), and various metal fibers and foils.

[0168] The compositions disclosed herein can be manufactured by mixing the various components described above. Mixing can be performed using mixers such as ball mills, sand mills, bead mills, pigment dispersers, grinders, ultrasonic dispersers, homogenizers, planetary mixers, and FILMIX mixers.

[0169] [electrode] The electrode of this disclosure has a current collector and an active material layer, the active material layer comprising the polyimide of this disclosure.

[0170] The electrodes in this disclosure can be either positive or negative.

[0171] The electrodes in this disclosure may contain positive or negative active materials.

[0172] The electrodes in this disclosure may contain conductive materials.

[0173] Regarding polyimide, active material, and conductive material in this disclosure, since they have been explained above, they are omitted here.

[0174] The polyimide content in this disclosure relative to the total mass of the active material layer is preferably 5% to 30% by mass, more preferably 7% to 20% by mass, and even more preferably 9% to 15% by mass.

[0175] There is no particular limitation on the thickness of the active material layer; for example, it can be set to 10 μm to 100 μm.

[0176] The current collector only needs to be a material that is conductive and has electrochemical durability; previously known materials can be appropriately selected and used.

[0177] As a current collector, a current collector made of one or more materials selected from iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, and their alloys can be used.

[0178] [Electrode manufacturing method] The method for manufacturing the electrode of this disclosure includes coating the composition of this disclosure onto the surface of a current collector and drying it to form an active material layer.

[0179] The coating of the composition can be performed on one side or both sides of the current collector. Alternatively, it can be performed on the entire surface of the current collector or on a portion thereof.

[0180] Examples of coating methods include doctor blade coating, dip coating, reverse roller coating, direct roller coating, gravure coating, and extrusion coating.

[0181] There are no particular limitations on the drying method; any known method can be used, such as drying based on warm air, hot air, or low-humidity air, vacuum drying, drying based on infrared or electron beam irradiation, etc.

[0182] From the viewpoint of reducing damage to the current collector, the drying temperature is preferably below 195°C, more preferably below 170°C, and even more preferably below 165°C.

[0183] From the viewpoint of cycling characteristics, the drying temperature is preferably higher than the glass transition temperature of polyimide, preferably 100°C or more higher, more preferably 120°C or more higher, and even more preferably 130°C or more higher.

[0184] It should be noted that after drying, pressure can be applied to the electrode using mold pressing or roller pressing. This pressure treatment improves the adhesion between the active material layer and the current collector, and also increases the density of the active material layer.

[0185] [Lithium-ion rechargeable battery] The lithium-ion secondary battery disclosed herein comprises a positive electrode, a negative electrode, a separator, and an electrolyte. The positive or negative electrode is the electrode of this disclosure.

[0186] (electrode) As for electrodes other than those described in this disclosure, there are no particular limitations, and known electrodes used in the manufacture of lithium-ion secondary batteries may be used. Specifically, electrodes formed by creating an electrode composite material layer on a current collector using known manufacturing methods may be used.

[0187] (Electrolyte) As the electrolyte, an organic electrolyte, formed by dissolving the supporting electrolyte in an organic solvent, is typically used. For example, a lithium salt can be used as the supporting electrolyte for a lithium-ion secondary battery. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred from the viewpoint of easy solubility in solvents and exhibiting a high degree of dissociation, with LiPF6 being particularly preferred.

[0188] Electrolytes can be used alone or in combination of two or more in any ratio. Generally, there is a tendency that the higher the degree of dissociation of the supporting electrolyte, the higher the lithium-ion conductivity. Therefore, the lithium-ion conductivity can be adjusted by the type of supporting electrolyte.

[0189] There are no particular limitations on organic solvents; examples include carbonate compounds, lactone compounds, ether compounds, sulfolane compounds, dioxane compounds, ketone compounds, nitrile compounds, and halogenated hydrocarbon compounds. Specifically, 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; butyrolactones such as γ-butylbutyrolactone; ethers such as dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,4-dioxane; sulfolane and 3-methylsulfolane; dioxanes such as 1,3-dioxane; ketones such as 4-methyl-2-pentanone; nitriles such as acetonitrile, propionitrile, valeronitrile, and benzonitrile; halogenated hydrocarbons such as 1,2-dichloroethane; other methyl formates; dimethylformamide; diethylformamide; dimethyl sulfoxide; imidazolium salts; and quaternary ammonium salts. Mixtures of these can also be included.

[0190] In the above, a carbonate compound with low solubility and the ability to suppress swelling of the polyimide disclosed herein is preferred.

[0191] (Diaphragm) The membrane is not particularly limited, but a microporous membrane formed of resins such as polyolefins (polyethylene, polypropylene), polyamides, and polyimides is preferred. Alternatively, a heat-resistant membrane may be used in which a coating is provided on one or both sides of the microporous membrane to improve its heat resistance. The polyimide in this disclosure may be contained in the resin composition used to form the coating.

[0192] [Manufacturing method of lithium-ion secondary batteries] The lithium-ion secondary battery disclosed herein can be manufactured, for example, by stacking the positive and negative electrodes through a separator, and winding them according to the battery shape as needed, or by stacking multiple sheets of the positive and negative electrodes through a separator, placing them in a battery container, injecting electrolyte into the battery container, and sealing it. To prevent pressure rise inside the lithium-ion secondary battery and overcharging / discharging, components such as fuses, PTC elements, expanded metal mesh, and lead plates can be provided as needed. The shape of the lithium-ion secondary battery can be any of the following: coin-shaped, button-shaped, sheet-shaped, cylindrical, square, or flat.

[0193] Example The present disclosure is illustrated below through examples, but the present disclosure is not limited to the following examples. It should be noted that, unless otherwise specified, "parts" and "%" are based on mass.

[0194] (Example 1) Add 30.44 g (100 mmol) of (2-phenyl-4-aminophenyl)-4-aminobenzoate (PHBAAB), an aromatic diamine compound, 29.23 g (100 mmol) of 1,3-bis(3-aminophenoxy)benzene (APB-N), an aromatic diamine compound, and 4,4'-oxobis(phthalamide) to a 500 ml separable flask equipped with a nitrogen inlet tube and a stirring device. Formic anhydride (ODPA) 31.02 g (100 mmol), ethylene glycol-bis-trimethoxymethyl ester (TMEG-100) 41.03 g (100 mmol), N-methyl-2-pyrrolidone (NMP) 498 g, pyridine 3.16 g (40 mmol), and toluene 50 g were reacted at 180 °C under a nitrogen atmosphere for 7 hours, with toluene being removed from the system midway, to obtain a 20% by mass polyimide solution. The imide group concentration of the polyimide in the polyimide solution was calculated to be 22.5%. The imide group concentrations of the polyimides prepared in the following examples and comparative examples were also calculated in the same way and are summarized in Table 1.

[0195] It should be noted that PHBAAB is a substance synthesized using the method described in the examples of Japanese Patent No. 6240798, APB-N is a substance manufactured by Mitsui Chemicals Co., Ltd., ODPA is a substance manufactured by Toho Chemical Industry Co., Ltd., and TMEG-100 is a substance manufactured by Shin Nippon Rikka Co., Ltd.

[0196] [Chemical Formula 27] [Chemical Formula 28] [Chemical Formula 29] [Chemical Formula 30] (Example 2) To a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, add 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 bis(triphenylene) dianhydride (TADBHQ), 41.03 g (100 mmol) of TMEG-100, 60 mmol of NMP, 3.16 g (40 mmol) of pyridine, and 60 g of toluene. Under a nitrogen atmosphere, react at 180 °C for 6 hours, while excluding toluene from the system midway, to obtain a 20% by mass polyimide solution.

[0197] Since a 20% by mass polyimide solution was obtained, it is known that the polyimide contained therein is solvent-soluble. The same applies to the following examples and comparative examples.

[0198] It should be noted that TADBHQ is a substance synthesized using the method described in the examples of Japanese Patent Application Publication No. 2023-2497.

[0199] [Chemical Formula 31] (Example 3) In a 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer, add 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), 306 g of NMP, 3.16 g (40 mmol) of pyridine, and 31 g of toluene. Under a nitrogen atmosphere, react at 180 °C for 7 hours while excluding toluene from the system midway through the reaction to obtain a 20% by mass polyimide solution.

[0200] It should be noted that BP-TME uses substances manufactured by Honshu Chemical Industry Co., Ltd.

[0201] [Chemical Formula 32] (Example 4) In a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, add 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) (as shown below), 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. Under a nitrogen atmosphere, react at 180 °C for 7 hours while excluding toluene from the system midway through the reaction, thereby obtaining a 20% by mass polyimide solution.

[0202] It should be noted that MBAA uses substances manufactured by SEIKA Co., Ltd.

[0203] [Chemical Formula 33] (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 added to a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirring device. The mixture was reacted at 180 °C under a nitrogen atmosphere for 7 hours, with the toluene being removed from the system midway through the reaction, to obtain a 20% by mass polyimide solution.

[0204] (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 added to a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirring device. The mixture was reacted at 180 °C under a nitrogen atmosphere for 7 hours, with toluene being removed from the system midway through the reaction, to obtain a 20% by mass polyimide solution.

[0205] (Example 7) In a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, add 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) as shown below, 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. Under a nitrogen atmosphere, react at 180 °C for 7 hours while purging toluene from the system midway through the reaction to obtain a 20% by mass polyimide solution.

[0206] It should be noted that DABz uses substances manufactured by Nippon Junryu Pharmaceutical Co., Ltd.

[0207] [Chemical Formula 34] (Example 8) In a 1000ml separable flask equipped with a nitrogen inlet tube and a stirrer, 42.61g (140 mmol) of PHBAAB, 17.54g (60 mmol) of APB-N, 50.06g (122 mmol) of TMEG-100, 10.69g (20 mmol) of BP-TME, 17.65g (60 mmol) of diphenyl-3,3',4,4'-tetracarboxylic dianhydride (BPDA) as shown below, 525.08g of NMP, 3.2g (20 mmol) of pyridine, and 53g of toluene were added. Under a nitrogen atmosphere, the mixture was reacted at 180°C for 7 hours, with toluene being removed from the system midway through the reaction, to obtain a 20% by mass polyimide solution.

[0208] It should be noted that BPDA uses substances manufactured by Ube Industries, Ltd.

[0209] [Chemical Formula 35] (Example 9) Except for changing the monomer composition ratio to the ratio recorded in Table 1, the same procedure as in Example 8 was followed to obtain a 20% by mass polyimide solution.

[0210] (Example 10) Except for changing the monomer composition ratio to the ratio recorded in Table 1, the same procedure as in Example 8 was followed to obtain a 20% by mass polyimide solution.

[0211] (Example 11) In a 500ml separable flask equipped with a nitrogen inlet tube and a stirrer, 42.61g (140 mmol) of PHBAAB, 17.54g (60 mmol) of APB-N, 50.06g (122 mmol) of TMEG-100, 22.82g (40 mmol) of TADBHQ, 11.77g (40 mmol) of BPDA, 550.08g of NMP, 3.2g (40 mmol) of pyridine, and 55g of toluene were added. The mixture was reacted for 7 hours at 180°C under a nitrogen atmosphere, with toluene being removed from the system midway through the reaction, to obtain a 20% by mass polyimide solution.

[0212] (Example 12) In a 500ml separable flask equipped with a nitrogen inlet tube and a stirrer, add 19.63g (64.5 mmol) of PHBAAB, 10.23g (35 mmol) of APB-N, 24.62g (30 mmol) of TMEG-100, 24.62g (60 mmol) of (BP-TME), 8.83g (30 mmol) of BPDA, 260g of NMP, 3.16g (40 mmol) of pyridine, and 26g of toluene. Under a nitrogen atmosphere, react at 180°C for 7 hours while excluding toluene from the system midway through the reaction to obtain a 20% by mass polyimide solution.

[0213] (Example 13) In a 500ml separable flask equipped with a nitrogen inlet tube and a stirrer, 21.30g (70 mmol) of PHBAAB, 8.77g (30 mmol) of APB-N, 22.57g (55 mmol) of TMEG-100, 8.02g (15 mmol) of (BP-TME), 8.83g (30 mmol) of BPDA, 264g of NMP, 3.16g (40 mmol) of pyridine, and 26g of toluene were added. The mixture was reacted for 7 hours at 180°C under a nitrogen atmosphere, with toluene being removed from the system midway through the reaction, to obtain a 20% by mass polyimide solution.

[0214] (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 added to a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirring device. The mixture was reacted at 180 °C under a nitrogen atmosphere for 7 hours, with toluene being removed from the system midway through the reaction, to obtain a 20% by mass polyimide solution.

[0215] (Comparative Example 2) To a 1000 ml separable flask equipped with a nitrogen inlet tube and a stirrer, add 60.87 g (150 mmol) of bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 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 react at 180 °C under a nitrogen atmosphere for 7 hours while purging toluene from the system midway, thereby obtaining a 20% by mass polyimide solution.

[0216] [Chemical Formula 36] <Determination of Glass Transition Temperature (Tg)> The polyimide solutions obtained in the above examples and comparative examples were spin-coated onto a 10 cm square glass plate and dried at 250°C for 1 hour. The plates were then peeled off to obtain test pieces (3 mm × 3 mm × (20 μm ± 3 μm)) weighing 3 mg. For each test piece obtained in this manner, the glass transition temperature (Tg) was measured using a DSCQ200 (trade name) manufactured by TA Instruments Japan Co., Ltd., under a nitrogen atmosphere at a heating rate of 10°C / min. The results are summarized in Table 2.

[0217] <Determination of 5% weight loss temperature (Td)> The polyimide solutions obtained in the above examples and comparative examples were coated onto a 10 cm square glass plate using a spin coating method and dried at 250°C for 1 hour. Then, the plates were peeled off to prepare test pieces with dimensions of (3 mm × 3 mm × (20 μm ± 3 μm)) and a weight of (5 mg).

[0218] In accordance with JIS K 7120, using TG-DTA: Hitachi High-Tech Science Co., Ltd. (trade name) STA7200R, the 5% weight reduction temperature of the above test pieces was measured in air at a heating rate of 10°C / min. The results are summarized in Table 2.

[0219] <Determination of Tensile Strength> The polyimide solutions obtained in the above examples and comparative examples were used to prepare test pieces with dimensions of 10 mm × 80 mm × (20 μm ± 3 μm). Tensile strength was measured using a tensile testing machine (Shimadzu Corporation, trade name: EZ-SX, clamp distance 50 mm) at a tensile speed of 10 mm / min. The average tensile strength of the three samples was taken as the tensile strength and summarized in Table 2.

[0220] It should be noted that the tensile strength was measured at 23±2℃ and 50±10% relative humidity.

[0221] <Determination of Elastic Modulus> The polyimide solutions obtained in the above examples and comparative examples were made into test pieces with dimensions of 10 mm × 80 mm × (20 μm ± 3 μm). The elastic modulus was measured using a tensile testing machine (Shimadzu Corporation, trade name: EZ-SX, clamp distance 50 mm) at a tensile speed of 10 mm / min. The average elastic modulus of the three samples was taken as the elastic modulus and summarized in Table 2.

[0222] It should be noted that the elastic modulus was measured at 23±2℃ and 50±10% relative humidity.

[0223] <Determination of Elongation> The polyimide solutions obtained in the above examples and comparative examples were made into test pieces with dimensions of 10 mm × 80 mm × 10 to 50 μm. The elongation was measured using a tensile testing machine (Shimadzu Corporation, trade name: EZ-SX, clamp distance 50 mm) at a tensile speed of 10 mm / min.

[0224] The maximum values ​​of displacements with n=3 are summarized in Table 2.

[0225] It should be noted that the elongation (%) is calculated by displacement (mm) / distance between clamps 50mm × 100.

[0226] It should be noted that the elongation was measured at 23±2℃ and 50±10% relative humidity.

[0227] <Determination of Coefficient of Thermal Expansion (CTE)> After processing the polyimide solutions obtained in the examples and comparative examples into films of approximately 20 μm ± 3 μm, test pieces with a size of 3 mm × 20 mm were prepared.

[0228] Using a thermal analysis apparatus (Hitachi High-Tech Science, TMA6100), the temperature of the test specimen was increased from room temperature (30°C) to 400°C at a rate of 10°C / min while a 5g load was applied. The average coefficient of thermal expansion (CTE) of the test specimen from 100°C to 200°C was then determined. The results are summarized in Table 2.

[0229] <Determination of Swelling Rate> The polyimide solutions obtained in the examples and comparative examples were coated onto glass plates and dried at 160°C for 10 hours to obtain a film with a thickness of approximately 40 μm. A 2 cm × 2 cm test piece was fabricated from the film and immersed in an electrolyte solvent composed of ethylene carbonate: propylene carbonate: dimethyl carbonate = 1:1:1.

[0230] The electrolyte solvent was heated to 50°C, and the test pieces were then immersed in the solution at 50°C for 72 hours. The weight change of the test pieces before and after the immersion treatment was measured, and the weight increase rate (%) was calculated as the swelling rate, which is summarized in Table 2.

[0231] Here, the membrane fabrication method does not affect the swelling ratio value. In addition, the weight of the membrane after impregnation is determined as follows: the test piece is removed from the electrolyte solvent, and the electrolyte adhering to the surface is quickly wiped off with a paper towel without drying, and then the measurement is performed.

[0232] <Determination of weight-average molecular weight (Mw)> The polyimide solutions obtained in the above examples and comparative examples were diluted with NMP, and the weight-average molecular weight was determined by high performance liquid chromatography (Tosoh).

[0233] [Table 1] [Table 2] <Evaluation of Cyclic Characteristics> The polyimide (solid component), negative electrode active material (silicon), and conductive material (carbon) contained in the polyimide solutions obtained in Examples 1, 4, 5, 7, 11, and 14 above were mixed according to the following composition to prepare a negative electrode composition for lithium-ion secondary batteries.

[0234] · Polyimide 10.0% by mass Silicon 87.0% by mass • Conductive agent 3.00% by mass As a current collector for the negative electrode, an electrolytic copper foil with a thickness of 10 μm is prepared, and the negative electrode composition obtained in the above manner is coated on the surface of the electrolytic copper foil. The negative electrode active material layer with a thickness of 30 μm is formed by heat treatment at 160°C, thereby producing a negative electrode for a lithium-ion secondary battery.

[0235] Lithium foil is prepared as the positive electrode for lithium-ion secondary batteries.

[0236] As an electrolyte for lithium-ion secondary batteries, a mixture of 1M LiPF6, ethylene carbonate and ethyl methyl carbonate (mixing ratio 1:1:1 (mass), VC (ethylene carbonate) 1% by mass) was prepared.

[0237] As a separator for lithium-ion secondary batteries, a single-layer microporous membrane made of polyolefin with a thickness of 25 μm (manufactured by Asahi Kasei Corporation, Celgard 2325) was prepared.

[0238] Using the above-mentioned negative electrode, positive electrode, electrolyte, and separator, a button cell type (R2032 type) lithium-ion secondary battery is manufactured in a dry environment with a dew point of -60°C.

[0239] The prepared lithium-ion secondary battery half-cell was left to stand at 30°C for 24 hours.

[0240] Then, at 30°C, the discharge capacity retention rate after 30 cycles is calculated as follows.

[0241] Charge to 5mV with a constant current (CC) at a current density equivalent to a 0.1C rate, then switch to constant voltage (CV) charging at 5mV, charging to a current density equivalent to a 0.01C rate, and then discharge to 1.2V with a current density equivalent to a 0.1C rate. This cycle is performed twice at 30°C. The discharge capacity equivalent to a 0.1C rate in the first cycle is set as "A".

[0242] Next, the circuit is charged at a constant current (CC) rate of 0.2C to 5mV, then switched to constant voltage (CV) charging at 0.5mV, charging to a current density equivalent to 0.02C, and then discharged at a current density equivalent to 0.2C to 1.2V. This cycle is performed 3 times at 30°C. Then, the circuit is charged at a constant current (CC) rate of 0.5C to 5mV, then switched to constant voltage (CV) charging at 5mV, charging to a current density equivalent to 0.05C, and then discharged at a current density equivalent to 0.5C to 1.2V. This cycle is performed 30 times at 30°C. The discharge capacity at the 0.5C rate of the 30th cycle is designated as "B".

[0243] Based on A and B above, the discharge capacity retention rate after 30 cycles is calculated using the following formula, and summarized in Table 3.

[0244] Discharge capacity retention after 30 cycles (%) = (B / A) × 100 [Table 3]

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), [Chemical Formula 1] In general formula (1), R1 to R4 are hydrogen atoms. At least one of R5 to R8 is an aromatic group, phenoxy, benzyl or benzyloxy with 6 to 10 carbon atoms, and the other R5 to R8 are hydrogen atoms; [Chemical Formula 2] In general formula (2), E1 and E2 are ester bonds. Z1 and Z2 are each independently a single bond, an alkyl group with substituents, or an alkyl group without substituents. W1 and W2 are each independently an oxygen atom, a nitrogen atom with a substituent, or a nitrogen atom without a substituent. R' is an alkylene group with a substituent, an alkylene group without a substituent, a group represented by the following general formula (3) or a group represented by the following general formula (3'); [Chemical Formula 3] In general formula (3), Z3 is a single bond, a substituent alkylene group, or an unsubstituent alkylene group. Z4 and Z5 are each independently an alkyl group with or without substituents. o and p are each independently 0 or an integer from 1 to 4. 1 represents the bonding portion with E1. 2 represents the bonding portion with E2; [Chemical Formula 4] In general formula (3'), Z6 and Z7 are each independently an alkyl group with or without substituents. 1 represents the bonding portion with E1. 2 is the bonding part with E2.

2. The polyimide of claim 1, wherein it is a diamine compound represented by the general formula (1), and... Represented by the general formula (2), where R' is an acid anhydride of alkylene with or without substituents in the general formula (2). The reactants.

3. The polyimide as described in claim 2, wherein, In the general formula (2), R' is an alkylene group with 1 to 5 carbon atoms that does not have substituents.

4. The polyimide as described in claim 2 or 3, wherein, In the general formula (2), Z1 and Z2 are single bonds. W1 and W2 are nitrogen atoms with substituents.

5. The polyimide as described in claim 2, wherein it is The diamine compound represented by the general formula (1), Represented by the general formula (2), where R' is an acid anhydride of alkylene with or without substituents, and... The diamine compound represented by the following formula (4) Reactants, [Chemical Formula 5] 。 6. The polyimide as described in claim 5, wherein it is The diamine compound represented by the general formula (1), Represented by the general formula (2), where R' is an acid anhydride with or without a substituent alkylene group. The diamine compound represented by formula (4), and The acid anhydride represented by the following general formula (5) Reactants, [Chemical Formula 6] In general formula (5), X represents a carbonyl group, an oxygen atom, or a single bond.

7. The polyimide as described in claim 1, wherein it is The diamine compound represented by the general formula (1), and An acid anhydride represented by the general formula (2) in which R' is a group represented by the general formula (3) below or a group represented by the general formula (3') below. The reactants.

8. The polyimide of claim 7, wherein, In general formula (3), Z3 is a single bond. o and p are 0.

9. The polyimide of claim 7, wherein, In general formula (3'), Z6 and Z7 are branched alkyl groups with 1 to 10 carbon atoms that do not have substituents.

10. The polyimide as described in claim 1 or 2, wherein it is The diamine compound represented by the general formula (1), Represented by the general formula (2), where R' is an acid anhydride of alkylene with or without substituents, and... An acid anhydride represented by the general formula (2) in which R' is a group represented by the general formula (3) below or a group represented by the general formula (3') below. The reactants.

11. The polyimide as described in claim 1 or 2, wherein it is solvent-soluble.

12. A composition comprising: The polyimide according to claim 1 or 2; and Solvent.

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

14. An electrode, which has a current collector and an active material layer. The active material layer comprises the polyimide as described in claim 1 or 2.

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

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