Polyol-modified soluble polyimide adhesive and preparation method therefor

Abstract

Disclosed in the present invention are a polyol-modified soluble polyimide adhesive and a preparation method therefor. The polyol-modified soluble polyimide adhesive has a structure represented by formula (I). By introducing a polyol and a diacyl into the molecular structure thereof, the rigidity of the imide ring is significantly reduced, the flexibility of the polyimide adhesive is increased, and the polyimide is rendered soluble in a conventional solvent. In addition, the polyimide of the present invention contains a large number of strongly polar groups, such as amide bonds and ester groups, such that same has strong adhesion.

Description

Polyol-modified soluble polyimide adhesive and its preparation method

[0001] Priority information

[0002] This application claims priority and benefits to patent application No. 202510218888.4, filed with the China National Intellectual Property Administration on February 26, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of battery technology, specifically to a polyol-modified soluble polyimide adhesive and its preparation method, as well as electrodes, batteries, and electrical devices. Background Technology

[0004] Binders are typically used in lithium-ion battery electrodes. Compared to polyvinylidene fluoride (PVDF), polyimide binders offer advantages such as high-temperature resistance, high-voltage resistance, and strong adhesion. However, traditional polyimide binders are prepared from a large amount of rigid aromatic dianhydrides and rigid diamines. Since the polyimide cured at high temperatures cannot dissolve in conventional solvents, it requires homogenization with polyamic acid followed by high-temperature curing and cross-linking. In practical applications, polyamic acid is prone to water absorption and decomposition, and also exhibits poor toughness. The coated and rolled electrodes are prone to curling or even cracking at high temperatures, ultimately leading to a decline in battery performance. Therefore, there is a need to develop a soluble polyimide binder with good flexibility and strong adhesion. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in the related art. Therefore, one object of this invention is to provide a soluble polyimide adhesive with good flexibility and strong adhesion.

[0006] Specifically, the first aspect of the present invention provides a polyol-modified soluble polyimide adhesive, said polyol-modified soluble polyimide adhesive having the structure shown in formula (I).

[0007]

[0008] Formula (I)

[0009] in,

[0010] R1 is selected from C2-C 10 The alkylene group may optionally be substituted with a C1-C6 alkyl group;

[0011] R2 is selected from substituted or unsubstituted C1-C. 10 Alkylene;

[0012] R3 is selected from single bond, oxygen group, carbonyl group, C3-C5 alkylene group, C6-C4 group, etc. 12 arylene dioxy, wherein the C3-C5 alkylene group is optionally substituted with a halogen, and the C6-C... 12 The arylene dioxy group is optionally substituted with a substituent;

[0013] R4 is selected from C6-C 40 Aromatic groups or C6-C 40 heteroaromatic groups, the C6-C 40 Aromatic groups and C6-C 40 Each of the heteroaromatic groups may optionally contain one or more of the following: ether group, ester group, carbonyl group, and halogen;

[0014] n is an integer between 100 and 500;

[0015] m is an integer from 4 to 120.

[0016] The polyimide molecule of this invention incorporates polyol and diacyl groups, i.e., introduces a structural... The introduction of this structure significantly improves the rigidity of the imide ring, increases the flexibility of the polyimide adhesive, and makes the polyimide soluble in conventional solvents. At the same time, the polyimide of the present invention contains a large number of strongly polar groups such as amide bonds and ester groups, thus having strong adhesive force.

[0017] A second aspect of the present invention provides a method for preparing a polyol-modified soluble polyimide adhesive according to the first aspect of the present invention, comprising the following steps:

[0018] Polyol and diacyl chloride are prepolymerized in a first solvent in the presence of an acid-binding agent to obtain a first prepolymer with hydroxyl-terminated ends;

[0019] The first prepolymer is reacted with a dianhydride in a second solvent to obtain a second prepolymer.

[0020] The second prepolymer is reacted with a diamine in a third solvent to obtain a polyol-modified soluble polyimide adhesive;

[0021] The polyol has the structure shown in formula (II):

[0022] Formula (II) is HO-R1-OH, where R1 is as described above;

[0023] The diacyl chloride has the structure shown in formula (III):

[0024] Equation (III), where R2 is as described above;

[0025] The dianhydride has the structure shown in formula (IV):

[0026] Equation (IV), where R3 is as described above;

[0027] The diamine has the structure shown in formula (V):

[0028] The formula is H2N-R4-NH2 (V), where R4 is as described above.

[0029] The preparation method of this invention is mild and undemanding, with simple and easily repeatable steps, making it suitable for large-scale industrial production. The method of this invention can produce soluble polyimide adhesives with good flexibility and strong adhesion.

[0030] A third aspect of the present invention provides an electrode comprising a polyol-modified soluble polyimide adhesive of the first aspect of the present invention or a polyol-modified soluble polyimide adhesive obtained by the method of the second aspect of the present invention.

[0031] A fourth aspect of the present invention provides a battery comprising the electrode sheet of the third aspect of the present invention.

[0032] A fifth aspect of the present invention provides an electrical device comprising the battery of the fourth aspect of the present invention.

[0033] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0034] Figure 1 is a cyclic volt-ampere curve of the button cell corresponding to Example 1.

[0035] Figure 2 is a cyclic voltammetry curve of the button cell corresponding to Comparative Example 2. Embodiments of the present invention

[0036] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] To facilitate understanding of the invention, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0041] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0042] Unless otherwise stated, conventional methods within the scope of the art, such as mass spectrometry, NMR, IR, and UV / Vis spectroscopy, and pharmacological methods, are employed. Unless specifically defined, the terminology used herein in the relevant descriptions of analytical chemistry, organic synthetic chemistry, and pharmaceutical and medicinal chemistry is known in the art. Standard techniques can be used in chemical synthesis, chemical analysis, drug preparation, formulation and delivery, and in the treatment of patients. For example, reactions and purifications can be carried out using the manufacturer's instructions for use of kits, or in accordance with methods known in the art or the descriptions of this application. The techniques and methods described herein are generally carried out according to conventional methods well known in the art, based on descriptions in several summary and more specific documents cited and discussed in this specification. In this specification, groups and their substituents can be selected by those skilled in the art to provide stable structural moieties and compounds. When a substituent is described by a conventional chemical formula written from left to right, the substituent also includes chemically equivalent substituents obtained when the structural formula is written from right to left. For example, CH2O is equivalent to OCH2.

[0043] The term "single bond" should be understood as a covalent bond formed by two atoms sharing a pair of electrons.

[0044] The term "halogen" includes fluorine, chlorine, bromine, and iodine.

[0045] The term "oxygen group" should be understood as representing -O-.

[0046] The term "carbonyl" should be understood to mean C=O, which is attached to other groups through a carbon atom.

[0047] The term "C1-C" 10 "Alkylene" should be understood as referring to a straight-chain or branched alkylene group having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, which is formed by two carbon atoms linked to other groups to form an alkylene group. C1-C 10 Alkylenes can be methylene (-CH2-), ethylene (-CH2CH2-), propylene (-CH2CH2CH2-, -CH(CH3)CH2-), etc.

[0048] The term "C2-C" 10 "alkylene" should be understood as referring to a straight-chain or branched alkylene with 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, which is connected to other groups through two carbon atoms to form an alkylene.

[0049] The term “C2-C5 alkylene” should be understood to refer to a straight-chain or branched alkylene with 2, 3, 4 or 5 carbon atoms, which is connected to other groups through two carbon atoms to form an alkylene.

[0050] The term “C3-C5 alkylene” should be understood to refer to a straight-chain or branched alkylene with 3, 4 or 5 carbon atoms, which is connected to other groups through two carbon atoms to form an alkylene group.

[0051] The term “C1-C6 alkylene” should be understood to refer to a straight-chain or branched alkylene with 1, 2, 3, 4 or 5 carbon atoms, which is connected to other groups through two carbon atoms to form an alkylene.

[0052] The term “C1-C3 alkylene” should be understood to refer to a straight-chain or branched alkylene with 1, 2 or 3 carbon atoms, which is connected to other groups through two carbon atoms to form an alkylene.

[0053] The term "C1-C6 alkyl" should be understood as referring to a straight-chain or branched alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms, which is linked to other groups through a carbon atom to form an alkyl group. C1-C6 alkyl groups can be methyl (-CH3), ethyl (-CH2CH3), propyl (-CH2CH2CH3, -CH(CH3)CH3), etc.

[0054] The term "C6-C" 12 "Arenedioxy" should be understood as referring to an arylenedioxy group having 6-12 carbon atoms. "Arenedioxy" should also be understood as a group formed when two hydrogen atoms in an aromatic compound are replaced by two oxygen atoms, for example... “C6-C 12"The optional substitution of the aryldioxy group with a substituent" should be understood as indicating C6-C 12 At least one hydrogen atom on the aryldioxy group is substituted with a substituent, or is not substituted. The substituent may be halogen, alkyl, aryl, etc.

[0055] "C3-C5 alkylene groups are optionally substituted with halogens" should be understood as indicating that at least one hydrogen atom on the C3-C5 alkylene group is substituted with a halogen.

[0056] The term "C6-C" 40 "Aromatic group" should be understood to refer to an aromatic group having 6-40 carbon atoms, wherein C6-C 40 The hydrogen atoms on the aromatic groups may optionally be substituted with substituents, which may contain one or more of the following: ether group, ester group, carbonyl group, halogen, alkylene group, alkyl group, aryl group, heteroaryl group.

[0057] The term "C6-C" 40 "Heteroaromatic group" should be understood as referring to a heteroaromatic group having 6-40 carbon atoms, wherein C6-C 40 The hydrogen atoms on the heteroaromatic group may optionally be replaced by substituents, which may contain aryl groups.

[0058] The term "aryl" should be understood to mean an aryl group having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. Examples of aryl groups include phenyl, biphenyl, etc.

[0059] The term "heteroaryl" should be understood to refer to non-fused and fused heteroaryl groups comprising 1 to 5 heteroatoms, wherein at least one heteroatom is selected from the group consisting of nitrogen, oxygen, sulfur, selenium, silicon, phosphorus, germanium, and boron atoms. The heteroaryl group can be a heteroaryl group having 3 to 30 carbon atoms, preferably a heteroaryl group having 3 to 20 carbon atoms, and more preferably a heteroaryl group having 3 to 12 carbon atoms. Suitable heteroaryl groups include pyridine, benzimidazole, pyrimidine, etc.

[0060] Binders are typically used in lithium-ion battery electrodes. Compared to polyvinylidene fluoride (PVDF), polyimide binders offer advantages such as high-temperature resistance, high-voltage resistance, and strong adhesion. However, traditional polyimide binders are prepared from a large amount of rigid aromatic dianhydrides and rigid diamines. Since the polyimide cured at high temperatures cannot dissolve in conventional solvents, it requires homogenization with polyamic acid followed by high-temperature curing and cross-linking. In practical applications, polyamic acid is prone to water absorption and decomposition, and also exhibits poor toughness. The coated and rolled electrodes are prone to curling or even cracking at high temperatures, ultimately leading to a decline in battery performance. Therefore, there is a need to develop a soluble polyimide binder with good flexibility and strong adhesion.

[0061] To address the above problems, this invention proposes a polyol-modified soluble polyimide adhesive, which introduces polyol and diacyl groups into its molecular structure, i.e., introduces a structural... The introduction of this structure significantly improves the rigidity of the imide ring, increases the flexibility of the polyimide adhesive, and makes the polyimide soluble in conventional solvents. At the same time, the polyimide of the present invention contains a large number of strongly polar groups such as amide bonds and ester groups, thus having strong adhesive force.

[0062] Specifically, the first aspect of the present invention provides a polyol-modified soluble polyimide adhesive, said polyol-modified soluble polyimide adhesive having the structure shown in formula (I).

[0063]

[0064] Formula (I)

[0065] in,

[0066] R1 is selected from C2-C 10 The alkylene group may optionally be substituted with a C1-C6 alkyl group;

[0067] R2 is selected from substituted or unsubstituted C1-C. 10 Alkylene;

[0068] R3 is selected from single bond, oxygen group, carbonyl group, C3-C5 alkylene group, C6-C4 group, etc. 12 arylene dioxy, wherein the C3-C5 alkylene group is optionally substituted with a halogen, and the C6-C... 12 The arylene dioxy group is optionally substituted with a substituent;

[0069] R4 is selected from C6-C 40 Aromatic groups or C6-C 40 heteroaromatic groups, the C6-C 40 Aromatic groups and C6-C 40 Each of the heteroaromatic groups may optionally contain one or more of the following: ether group, ester group, carbonyl group, and halogen;

[0070] n is an integer between 100 and 500;

[0071] m is an integer from 4 to 120.

[0072] The polyimide binder of the present invention is not only flexible, strong, and soluble, but also can be cured at a low temperature, eliminating the need for secondary curing and crosslinking at high temperatures. When applied to electrode slurry, it can be cured as the electrode dries, thus avoiding the risk of degradation of active materials at high temperatures.

[0073] In addition, the polyimide adhesive of the present invention is preferably free of fluorine atoms, so it will not produce toxic fluorine-containing gas during the high-temperature cutting process of the electrode sheet like PVDF, and is inexpensive and has stronger adhesion.

[0074] In some embodiments, m is an integer from 4 to 15. The R1 group is formed by the dehydrogenation of the raw material polyol. The low molecular weight polyol can reduce the viscosity of the binder solution. The low viscosity is beneficial to the uniform mixing of the electrode slurry, which is beneficial to the electrode manufacturing process.

[0075] In some specific embodiments, m can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.

[0076] In some embodiments, R1 is selected from In this polyol, C2-C5 alkylene groups are replaced by C1-C6 alkyl groups. Branched polyols can reduce the viscosity of the adhesive solution. Lower viscosity is beneficial for the uniform mixing of the electrode slurry, which in turn is beneficial for the electrode manufacturing process. Therefore, in this invention, it is preferable that the alkylene groups in the polyol are replaced by alkyl groups.

[0077] In some specific embodiments, the C2-C5 alkylene substituted with C1-C6 alkyl may be ethylene substituted with C1-C6 alkyl, propylene substituted with C1-C6 alkyl, butylene substituted with C1-C6 alkyl, or pentylene substituted with C1-C6 alkyl.

[0078] In some embodiments, R2 is selected from unsubstituted C1-C6 alkylene groups. The R2 group originates from the dechlorination of the starting material diacyl chloride; smaller molecule diacyl chlorides have better chain extension effects, which is beneficial for introducing more structures. Introducing a large number of ester groups can enhance molecular chain rotation, improve film strength, improve the rigidity of imide rings, and enhance the flexibility of the electrode. Secondly, it can enhance the peel force of the electrode on the basis of polyimide, further optimizing the electrode coating effect. At the same time, it can increase the flexibility and solubility of polyimide binder.

[0079] In some specific embodiments, R2 is selected from unsubstituted C1-C3 alkylene groups.

[0080] In some specific embodiments, R2 is selected from methylene, ethylene, and propylene.

[0081] In some embodiments, R3 is selected from one of the following structures:

[0082] Single bond, oxygen group, carbonyl group , The R3 group originates from the dianhydride in the raw material. Optimizing the type of dianhydride is beneficial to improving the thermal stability and mechanical properties of polyimide binders.

[0083] In some embodiments, R4 is selected from one of the following structures:

[0084] , , , , , , , , , The R4 group originates from the raw material diamine. Optimizing rigid diamine is beneficial for improving the thermal stability and mechanical properties of polyimide binders.

[0085] A second aspect of the present invention provides a method for preparing a polyol-modified soluble polyimide adhesive according to the first aspect of the present invention, comprising the following steps:

[0086] Polyol and diacyl chloride are prepolymerized in a first solvent in the presence of an acid-binding agent to obtain a first prepolymer with hydroxyl-terminated ends;

[0087] The first prepolymer is reacted with a dianhydride in a second solvent to obtain a second prepolymer.

[0088] The second prepolymer is reacted with a diamine in a third solvent to obtain a polyol-modified soluble polyimide adhesive;

[0089] The polyol has the structure shown in formula (II):

[0090] Formula (II) is HO-R1-OH, where R1 is as described above;

[0091] The diacyl chloride has the structure shown in formula (III):

[0092] Equation (III), where R2 is as described above;

[0093] The dianhydride has the structure shown in formula (IV):

[0094] Equation (IV), where R3 is as described above;

[0095] The diamine has the structure shown in formula (V):

[0096] The formula is H2N-R4-NH2 (V), where R4 is as described above.

[0097] The preparation method of this invention is mild and undemanding, with simple and easily repeatable steps, making it suitable for large-scale industrial production. The method of this invention can produce soluble polyimide adhesives with good flexibility and strong adhesion.

[0098] The reaction route of the preparation method of the present invention is as follows:

[0099] ;

[0100] ;

[0101] .

[0102] In some embodiments, the polyol includes one or more of polyethylene glycol, polypropylene glycol, and hydroxyl-terminated polybutadiene acrylonitrile (HTBN).

[0103] In some specific embodiments, the number average molecular weight of the polyol can be 230 Daltons to 10,000 Daltons, for example 230 Daltons to 1,000 Daltons, 1,000 Daltons to 2,000 Daltons, 2,000 Daltons to 3,000 Daltons, 3,000 Daltons to 4,000 Daltons, 4,000 Daltons to 5,000 Daltons, 5,000 Daltons to 6,000 Daltons, 6,000 Daltons to 7,000 Daltons, 7,000 Daltons to 8,000 Daltons, 8,000 Daltons to 9,000 Daltons, or 9,000 Daltons to 10,000 Daltons.

[0104] In some specific embodiments, the number average molecular weight of polyethylene glycol can be 200-5000 Daltons, such as 230 Daltons, 400 Daltons, 1000 Daltons, 2000 Daltons, 4000 Daltons or 5000 Daltons.

[0105] In some specific embodiments, the number average molecular weight of polypropylene glycol can be 400-8000 Daltons, such as 400 Daltons, 1000 Daltons, 2000 Daltons, 4000 Daltons or 8000 Daltons.

[0106] In some specific embodiments, the number average molecular weight of hydroxyl-terminated polybutadiene acrylonitrile (HTBN) can be 1,000-5,000 Daltons, such as 1,000 Daltons, 2,000 Daltons, 3,000 Daltons, 4,000 Daltons or 5,000 Daltons.

[0107] In some embodiments, the diacyl chloride includes one or more of succinyl chloride, glutaryl chloride, adipic acid chloride, heptacyanate chloride, and sebacyl chloride. Preferably, the diacyl chloride includes one or more of succinyl chloride, glutaryl chloride, and adipic acid chloride.

[0108] In some embodiments, the acid-binding agent includes one or more of triethylamine, pyridine, sodium hydroxide, potassium hydroxide, and imidazole.

[0109] In some embodiments, the molar ratio of hydroxyl groups, acid-binding agents, and diacyl chlorides in the polyol may be 2:(1-1.5):(1-1.2).

[0110] In some specific embodiments, the molar ratio of hydroxyl groups, acid-binding agents, and diacyl chlorides in the polyol may be 2:1:1, 2:1.2:1, 2:1.5:1, 2:1:1.1, 2:1:1.2, 2:1.2:1.1, 2:1.2:1.2, 2:1.5:1.1, or 2:1.5:1.2.

[0111] In some embodiments, the step of prepolymerizing polyol and diacyl chloride in a first solvent in the presence of an acid-binding agent to obtain a first prepolymer with hydroxyl-terminated ends further includes: mixing the polyol, the acid-binding agent, and the first solvent; adding the diacyl chloride dropwise into the mixture at -10°C to 10°C for 1-5 hours; and performing prepolymerization for 2-5 hours after the addition is completed.

[0112] In some specific embodiments, the temperature at which the diacyl chloride is added dropwise can be -10°C, -5°C, 0°C, 5°C, or 10°C. The dropwise addition time can be 1 h, 2 h, 3 h, 4 h, or 5 h. The prepolymerization time can be 2 h, 3 h, 4 h, or 5 h.

[0113] In some embodiments, the dianhydride may be 4,4'-terephthalodioxydiphthalic anhydride (TPA). ), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride ( ), 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride ( ), 4,4'-oxophthalic anhydride ( ), 3,3',4,4'-benzophenone tetracarboxylic dianhydride ( One or more of the following.

[0114] In some embodiments, the molar ratio of hydroxyl groups to dianhydrides in the first prepolymer can be 1:(2-2.2). Optimizing the molar ratio of hydroxyl groups to dianhydrides in the first prepolymer helps to control the reaction in the direction of generating the second prepolymer and reduces byproducts.

[0115] In some specific embodiments, the molar ratio of hydroxyl groups to dianhydrides in the first prepolymer may be 1:2, 1:2.1, or 1:2.2.

[0116] In some embodiments, the step of reacting the first prepolymer with the dianhydride in a second solvent to obtain the second prepolymer further includes: mixing the dianhydride with the second solvent to form a homogeneous solution, adding the first prepolymer in batches, and then reacting at 25°C-45°C for 3-5 hours.

[0117] In some specific embodiments, the reaction temperature for preparing the second prepolymer can be 25°C, 30°C, 35°C, 40°C, or 45°C. The reaction time can be 3h, 3.5h, 4h, 4.5h, or 5h.

[0118] In some embodiments, the diamine includes p-phenylenediamine (P-phenylenediamine). m-phenylenediamine ( ), 2,2-bis(4-aminophenyl)hexafluoropropane ( ), 2-(4-aminophenyl)-5-aminobenzimidazole ( ), 3,4-pyridinediamine ( Toluenediamine () ), 2,5-bis(4-amino-phenyl)pyrimidine ( ), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane ( ), 2,2'-dimethyl-4,4'-diaminobiphenyl ( ), 3,3'-dimethyl-4,4'-diaminobiphenyl ( One or more of the following.

[0119] In some embodiments, the molar ratio of the anhydride group in the second prepolymer to the amino group in the diamine can be (1-1.2):1. Controlling the molar ratio of the anhydride group in the second prepolymer to the amino group in the diamine is beneficial for controlling the reaction to proceed in the direction of generating the target product and reducing by-products.

[0120] In some specific embodiments, the molar ratio of the anhydride group in the second prepolymer to the amino group in the diamine may be 1:1, 1.1:1, or 1.2:1.

[0121] In some embodiments, the step of reacting the second prepolymer with the diamine in a third solvent to obtain a polyol-modified soluble polyimide adhesive further includes: reacting the second prepolymer with the diamine in a third solvent at 20°C-30°C for 12-24 hours; then adding a catalyst and heating to 120°C-180°C to react for 5-10 hours.

[0122] In some specific embodiments, the reaction time between the second prepolymer and the diamine can be 12h, 14h, 16h, 18h, 20h, 22h, or 24h. The heating temperature can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, or 180℃. The heating reaction time can be 5h, 6h, 7h, 8h, 9h, or 10h.

[0123] In some embodiments, the catalyst includes one or more of isoquinoline, piperazine, and triethylamine.

[0124] In some embodiments, the first solvent, the second solvent, and the third solvent each comprise at least one of N-methylpyrrolidone and N,N-dimethylacetamide. The present invention does not impose any particular limitation on the type of solvent, as long as it can dissolve the reaction substrate and does not participate in the reaction.

[0125] In some embodiments, the molar amount of hydroxyl groups in the polyol is denoted as n1, the molar amount of acyl chloride is denoted as n2, the molar amount of acid anhydride is denoted as n3, and the molar amount of diamine is denoted as n4, satisfying the following condition: n2-n1 ≥ n4-n3.

[0126] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0127] The raw materials used in the examples include polyethylene glycol and polypropylene glycol with different degrees of polymerization. Polybutane and HTBN were purchased from Aladdin.

[0128] Example 1

[0129] (1) Polyethylene glycol (HO(CH2CH2O) m+1 H, m is 9), triethylamine, and N-methylpyrrolidone were mixed, and succinyl chloride was added dropwise to the mixture at 0°C for 3 hours to carry out preliminary prepolymerization. The reaction was carried out for 3 hours, and then filtered to obtain the first prepolymer with hydroxyl-terminated ends.

[0130] (2) Mix 4,4'-terephthalic anhydride and N-methylpyrrolidone to form a homogeneous solution, and then add the first prepolymer obtained in step 1 in batches. After the addition is complete, react at 35°C for 4 hours to obtain the second prepolymer.

[0131] (3) Under room temperature conditions, the second prepolymer obtained in step 2 was dissolved in N-methylpyrrolidone to form a homogeneous solution. Then, p-phenylenediamine was added in batches and the reaction was carried out at room temperature for 18 h. Then, isoquinoline was added and the temperature was raised to 160 °C and stirred for 8 h. After the reaction was completed, a blackish-red viscous liquid was obtained and diluted with N-methylpyrrolidone to a solid content of 10 wt% for later use.

[0132] Example 2-Example 21

[0133] Examples 2-21 were carried out according to the method of Example 1, with the differences shown in Table 1.

[0134] Comparative Example 1

[0135] Comparative Example 1 was carried out according to the method of Example 1, with the differences shown in Table 1.

[0136] Comparative Example 2

[0137] PVDF is provided as an adhesive.

[0138] Table 1

[0139]

[0140] Product characterization and performance testing

[0141] (1) Number-average molecular weight test: The number-average molecular weight of the binder was tested using gel permeation chromatography (GPC) with dimethyl sulfoxide (DMSO) as the mobile phase. The degree of polymerization was calculated as the number-average molecular weight divided by the molecular weight of the repeating unit. The test results are shown in Table 2 below.

[0142] (2) Viscosity test: The polyimide adhesives prepared in the above examples and comparative examples were kept at 25°C for 6 hours and then tested using a digital rotational viscometer at a rotation speed of 20 rpm. The test results are shown in Table 2 below.

[0143] (3) Peel force test of electrode sheet: The positive electrode sheet was prepared as described below, and a 180° peel force test was performed after rolling. The test results are shown in Table 2 below.

[0144] (4) Flexibility test: The adhesive solution was dried into a film, and its mechanical properties, including tensile strength and elongation at break, were tested using a universal testing machine. The test results are shown in Table 2 below.

[0145] (5) Visual inspection of appearance.

[0146] The test results are shown in Table 2 below.

[0147] Table 2

[0148]

[0149] Using the polyimide binder prepared in Example 1 and PVDF, button cells were prepared using the general method described below.

[0150] (1) Preparation of positive electrode sheet

[0151] Lithium iron phosphate (LFP), conductive carbon black SP, and binder (i.e., the binder prepared in the above examples or comparative examples) are mixed in a mass ratio of 8:1:1. N-methyl-2-pyrrolidone is added and mixed evenly. The mixture is then coated onto aluminum foil, dried, rolled, and cut to obtain a positive electrode sheet.

[0152] (2) Preparation of negative electrode sheet

[0153] The negative electrode uses lithium foil.

[0154] (3) Assemble button batteries

[0155] A 1.0 mol / L lithium hexafluorophosphate solution was used as the electrolyte to assemble a coin cell by combining the positive electrode, separator, negative electrode, and electrolyte.

[0156] Button cell battery performance test

[0157] (1) Cyclic Voltmeter-Ampere Test (CV Test)

[0158] Cyclic voltammetry curves were tested using a multichannel electrochemical workstation (manufacturer: Bioroger, France, model VMP3) at a scan rate of 0.1 mV / s and a potential range of 2.0–4.5 V. The presence of redox peaks in the CV curves was observed, and the test results are shown in Table 3.

[0159] (2) Initial charge and discharge capacity test and coulombic efficiency test

[0160] The constant current charge-discharge performance of the battery was tested using a LAND CT2001A battery testing system at a constant temperature of 25℃. The charge-discharge currents were 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, and 5 C. The voltage range for cycle performance was 2.5–4.3 V, with a cycle charge-discharge current of 0.2 C. The measured initial charge capacity is shown in Table 3. The ratio of initial charge capacity to initial discharge capacity is the initial coulombic efficiency, and the test results are shown in Table 3.

[0161] (3) Cyclic performance test

[0162] The capacity retention rate test process is as follows: At 25℃, the prepared coin cell is charged to 4.2V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 4.2V, rested for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same coin cell, and the discharge capacity Cn of the coin cell after the nth cycle is recorded. The capacity retention rate Pn of the coin cell after each cycle is then calculated as Pn = Cn / C0. 100%.

[0163] Table 3

[0164]

[0165] Results and Discussion:

[0166] As shown in Tables 2-3, by comparing Examples 1-21 and Comparative Example 1, it can be seen that the polyol-modified polyimide prepared by the present invention is a liquid, has solubility, significantly improves elongation at break, and has better flexibility.

[0167] By comparing Examples 1-21 and Comparative Example 2, it can be seen that the polyol-modified polyimide prepared in this invention has significantly higher electrode peel strength, stronger adhesion, and better battery performance.

[0168] Comparing Examples 1 and 2, it can be seen that branched polyols can reduce the viscosity of the adhesive solution. Low viscosity is beneficial to the uniform mixing of the electrode slurry, which in turn is beneficial to the electrode manufacturing process.

[0169] Comparative examples 5-8 show that low molecular weight polyols can reduce the viscosity of the adhesive solution. Low viscosity is beneficial for the uniform mixing of the electrode slurry, which in turn benefits the electrode manufacturing process.

[0170] A comparison of Examples 1 and 9-11 shows that the small molecule diacyl chloride has a better chain extension effect, which is beneficial for introducing more structures. Introducing a large number of ester groups can enhance molecular chain rotation, improve film strength, improve the rigidity of imide rings, and enhance the flexibility of the electrode. Secondly, it can enhance the peel force of the electrode on the basis of polyimide, further optimizing the electrode coating effect. At the same time, it can increase the solubility of polyimide binder.

[0171] Figure 1-2 shows the cyclic voltammetry curves of the coin cells corresponding to Example 1 and Comparative Example 2. It can be clearly seen that under the working voltage of LFP, the polyimide binder prepared in Example 1 does not produce a redox reaction with the electrolyte. This indicates that the polyimide binder of the present invention has a stable structure and is not easily decomposed.

[0172] In summary, this invention introduces polyols and diacyl groups into the polyimide molecule, i.e., introduces a structural... This invention significantly improves the rigidity of the imide ring, increases the flexibility of the polyimide adhesive, and makes the polyimide soluble in conventional solvents. In addition, the polyimide of this invention contains a large number of strongly polar groups such as amide bonds and ester groups, thus exhibiting strong adhesive force.

[0173] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0174] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A polyol-modified soluble polyimide adhesive, wherein, The polyol-modified soluble polyimide adhesive has the structure shown in formula (I). Formula (I) in, R1 is selected from C2-C 10 The alkylene group may optionally be substituted with a C1-C6 alkyl group; R2 is selected from substituted or unsubstituted C1-C. 10 Alkylene; R3 is selected from single bond, oxygen group, carbonyl group, C3-C5 alkylene group, C6-C4 group, etc. 12 arylene dioxy, wherein the C3-C5 alkylene group is optionally substituted with a halogen, and the C6-C... 12 The arylene dioxy group is optionally substituted with a substituent; R4 is selected from C6-C 40 Aromatic groups or C6-C 40 heteroaromatic groups, the C6-C 40 Aromatic groups and C6-C 40 Each of the heteroaromatic groups may optionally contain one or more of the following: ether group, ester group, carbonyl group, and halogen; n is an integer between 100 and 500; m is an integer from 4 to 120.

2. The polyol-modified soluble polyimide adhesive according to claim 1, wherein, m is an integer from 4 to 15.

3. The polyol-modified soluble polyimide adhesive according to claim 1 or 2, wherein, R1 is selected from In which C2-C5 alkylene groups are replaced by C1-C6 alkyl groups.

4. The polyol-modified soluble polyimide adhesive according to any one of claims 1-3, wherein, R2 is selected from unsubstituted C1-C6 alkylene groups; preferably, R2 is selected from unsubstituted C1-C3 alkylene groups.

5. The polyol-modified soluble polyimide adhesive according to any one of claims 1-4, wherein, R3 is selected from one of the following structures: Single bond, oxygen group, carbonyl group 、 。 6. The polyol-modified soluble polyimide adhesive according to any one of claims 1-5, wherein, R4 is selected from one of the following structures: 、 、 、 、 、 、 、 、 、 。 7. A method for preparing the polyol-modified soluble polyimide adhesive according to any one of claims 1-6, wherein, Includes the following steps: Polyol and diacyl chloride are prepolymerized in a first solvent in the presence of an acid-binding agent to obtain a first prepolymer with hydroxyl-terminated ends; The first prepolymer is reacted with a dianhydride in a second solvent to obtain a second prepolymer. The second prepolymer is reacted with a diamine in a third solvent to obtain a polyol-modified soluble polyimide adhesive; The polyol has the structure shown in formula (II): HO-R1-OH formula (II), wherein R1 is as described in any one of claims 1-3; The diacyl chloride has the structure shown in formula (III): Formula (III), wherein R2 is as described in claim 1 or 4; The dianhydride has the structure shown in formula (IV): Formula (IV), wherein R3 is as described in claim 1 or 5; The diamine has the structure shown in formula (V): H2N-R4-NH2 (V), wherein R4 is as described in claim 1 or 6.

8. The method according to claim 7, wherein, The polyol includes one or more of polyethylene glycol, polypropylene glycol, and hydroxyl-terminated polybutadiene acrylonitrile; Optionally, the diacyl chloride includes one or more of succinyl chloride, glutaryl chloride, adipicoyl chloride, pimecroyl chloride, and sebacyl chloride; Optionally, the acid-binding agent includes one or more of triethylamine, pyridine, sodium hydroxide, potassium hydroxide, and imidazole; Optionally, the molar ratio of hydroxyl groups, acid-binding agents, and diacyl chlorides in the polyol is 2:(1-1.5):(1-1.2). Optionally, the step of prepolymerizing the polyol and diacyl chloride in the first solvent in the presence of an acid-binding agent to obtain a first prepolymer with hydroxyl-terminated ends further includes: mixing the polyol, the acid-binding agent, and the first solvent, adding the diacyl chloride dropwise into the mixture at -10°C to 10°C for 1-5 hours, and then performing prepolymerization for 2-5 hours after the addition is completed.

9. The method according to claim 7 or 8, wherein, The dianhydride is , , , , One or more of the following; Optionally, the molar ratio of hydroxyl groups to dianhydrides in the first prepolymer is 1:(2-2.2). Optionally, the step of reacting the first prepolymer with the dianhydride in the second solvent to obtain the second prepolymer further includes: mixing the dianhydride with the second solvent to form a homogeneous solution, adding the first prepolymer in batches, and then reacting at 25℃-45℃ for 3h-5h.

10. The method according to any one of claims 7-9, wherein, The diamine includes , , , , , , , , , One or more of the following; Optionally, the molar ratio of the anhydride group in the second prepolymer to the amino group in the diamine is (1-1.2):1; Optionally, the step of reacting the second prepolymer with the diamine in a third solvent to obtain a polyol-modified soluble polyimide adhesive further includes: reacting the second prepolymer with the diamine in a third solvent at 20°C-30°C for 12-24 hours; then adding a catalyst and heating to 120°C-180°C to react for 5-10 hours. The catalyst includes one or more of isoquinoline, piperazine, and triethylamine.

11. The method according to any one of claims 7-10, wherein, The first solvent, the second solvent, and the third solvent each include at least one of N-methylpyrrolidone and N,N-dimethylacetamide.

12. An electrode sheet, wherein, The adhesive comprises a polyol-modified soluble polyimide adhesive according to any one of claims 1-6 or a polyol-modified soluble polyimide adhesive obtained by the method according to any one of claims 7-11.

13. A battery, wherein, Includes the electrode as described in claim 12.

14. An electrical appliance, wherein, Includes the battery as described in claim 13.

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