A water-soluble polyimide binder, a method for preparing the same, and an application thereof
A water-soluble polyimide binder was prepared by combining carboxyl diamine, non-carboxyl diamine, and polyols, which solved the problems of traditional polyimide binders being insoluble in water and having poor adhesion, thus improving the cycle life and battery performance of silicon-carbon electrodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NINGBO BOYA POLY ADVANCED MATERIALS CO LTD
- Filing Date
- 2023-04-20
- Publication Date
- 2026-05-29
AI Technical Summary
Traditional polyimide binders are insoluble in water and have poor adhesion, which limits their application in silicon-carbon electrodes. Furthermore, existing water-soluble improvement methods suffer from high processing temperatures or insufficient performance, resulting in insufficient cycle life of silicon-carbon anodes.
By selecting a combination of carboxyl-containing and carboxyl-free diamines and adding polyols, a polyimide binder with excellent water solubility, tensile strength and ductility was prepared. Combined with dianhydrides and catalysts, its bonding performance to metals and silicon carbide materials was improved.
This invention achieves excellent solubility of water-soluble polyimide binders in water, good tensile strength and ductility, improves the bonding performance to metals and silicon-carbon materials, and enhances the cycle stability and charge-discharge performance of batteries.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a water-soluble polyimide binder, its preparation method, and its application. Background Technology
[0002] To improve the energy density of lithium-ion batteries and meet the growing demands of portable electronic devices, electric vehicles, and large-scale energy storage systems, new materials for lithium-ion battery electrodes have attracted widespread attention. Among these materials, silicon-carbon materials are considered the most promising anode materials for next-generation lithium-ion batteries because their theoretical specific capacity is more than 10 times that of currently used graphite electrodes, and they are naturally abundant. However, the cycle life of silicon-carbon anode materials is limited by the huge volume changes during charge-discharge cycles, leading to repeated formation of solid electrolyte interfaces, which in turn causes electrode pulverization and continuous capacity decay.
[0003] Using traditional graphite anode binders can achieve higher specific capacity than traditional graphite electrodes and improve the cycle performance of silicon anodes, but there is still an urgent need to develop a simple and effective method to extend the cycle life of silicon-carbon anodes for further large-scale production; although the proportion of binders in silicon-carbon electrode composites is relatively small, they have a great influence on the cycle performance of silicon-carbon anodes.
[0004] Polyimide, as a commonly used engineering material, has been applied in many fields due to its excellent comprehensive properties, including excellent mechanical properties, excellent chemical and thermal stability, and excellent solvent resistance. CN115160566A discloses a polyimide adhesive, slurry, film, preparation method thereof, and flexible display device. The raw materials for preparing the above-mentioned polyimide adhesive include diamine monomers and diamine monomers; the diamine monomers include a main monomer, which includes at least one of 9,9-bis(4-aminophenyl)fluorene and 4,4'-bis(aminophenoxy)diphenyl fluorene. When the main monomer includes 9,9-bis(4-aminophenyl)fluorene, the diamine monomers also include a comonomer. The comonomer has a stronger reactivity than the main monomer, and the molar number of the comonomer accounts for 30% of the total molar number of the diamine monomers; the diamine monomers include at least one of cyclobutanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, and bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride. The above-mentioned polyimide can be used to prepare transparent polyimide films with small phase differences in the thickness direction.
[0005] However, most traditional polyimides are insoluble or only soluble in environmentally harmful, highly polar organic solvents, and have poor adhesion. Although the addition of amino alcohols to traditional polyamic acids can greatly improve their water solubility, the excessively high processing temperature during imidization also limits their practical application in silicon-carbon electrodes.
[0006] Based on the above problems, developing a water-soluble polyimide adhesive with excellent water solubility, adhesion, tensile strength and ductility is an urgent technical problem to be solved in this field. Summary of the Invention
[0007] To address the shortcomings of existing technologies, the present invention aims to provide a water-soluble polyimide binder, its preparation method, and its application. By selecting a carboxyl-containing diamine and a carboxyl-free diamine for combination and adding a polyol, the molecular structure of the polyimide is successfully designed and modified, resulting in a polyimide binder with excellent water solubility, good tensile strength, and ductility. It also exhibits excellent bonding performance to metals (copper, iron, aluminum, etc.) and silicon-carbon materials, thus improving the electrochemical performance of batteries made using the water-soluble polyimide binder.
[0008] To achieve this objective, the present invention adopts the following technical solution:
[0009] In a first aspect, the present invention provides a water-soluble polyimide binder, wherein the raw materials for preparing the water-soluble polyimide binder include a carboxyl-containing diamine, a carboxyl-free diamine, a polyol, a dianhydride, and a catalyst.
[0010] The raw materials for preparing the water-soluble polyimide binder provided by this invention include a combination of carboxyl-containing diamine, carboxyl-free diamine, polyol, dianhydride, and catalyst. The polyol, carboxyl-containing diamine, and residual acid after dianhydride esterification all contribute to improving the water solubility of the polyimide, resulting in excellent water solubility. Furthermore, the polyol provides sufficient flexibility, giving the polyimide excellent elongation. The combination of rigid dianhydride and diamine groups ensures the thermal properties of the polyimide, while the polyimide skeleton contributes to its excellent mechanical properties. Ultimately, the resulting water-soluble polyimide binder not only exhibits excellent water solubility, good tensile strength, and ductility, but also excellent bonding properties to metals (copper, iron, aluminum) and silicon-carbon materials. This allows the battery prepared using the water-soluble polyimide as a negative electrode binder to protect the silicon-carbon negative electrode during charge and discharge, resulting in excellent cycle stability.
[0011] Preferably, the molar ratio of the carboxyl-free diamine, the carboxyl-containing diamine, and the polyol is 1:(1-6):(1-3), and more preferably 1:(1.5-4.5):(1.2-2).
[0012] The molar ratio of the carboxyl-free diamine to the carboxyl-containing diamine is 1:2, 1:3, 1:4, or 1:5, etc.
[0013] The molar ratio of the carboxyl-free diamine to the polyol is 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, or 1:2.8, etc.
[0014] As a preferred technical solution, the present invention limits the molar ratio of the carboxyl-free diamine to the carboxyl-containing diamine to 1:(1-6). If the molar ratio of the carboxyl-free diamine to the carboxyl-containing diamine is too high, the water solubility of the obtained polyimide will be reduced, the peel strength will be reduced, and the cycle capacity retention rate of the battery prepared with the same amount of polyimide binder will also be reduced. If the limited molar ratio of the carboxyl-free diamine to the carboxyl-containing diamine is too low, the initial efficiency of the battery prepared with the same amount of polyimide binder will be reduced.
[0015] Preferably, the carboxyl-free diamine includes any one or a combination of at least two of the following: p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 4,4'-diaminobenzoylaniline, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 4,4'-diaminodiphenyl sulfone, 2-(4-aminophenyl)-5-aminobenzimidazole, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-biphenyl, or 9,9-bis(4-aminophenyl)fluorene.
[0016] Preferably, the carboxyl-containing diamine includes any one or a combination of at least two of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid, 6,6'-diamino-3,3'-methylenedibenzoic acid, 3,5-diaminobenzoic acid, or benzidine disulfonic acid.
[0017] Preferably, the polyol includes a diol, and more preferably any one or a combination of at least two of ethylene glycol, propylene glycol, butylene glycol, or polyethylene glycol.
[0018] Preferably, the number average molecular weight of the polyethylene glycol is 100 to 50,000, such as 1,000, 5,000, 10,000, 20,000, 30,000 or 40,000, and more preferably 200 to 3,000.
[0019] Preferably, the total molar ratio of the carboxyl-containing diamine, the carboxyl-free diamine and the polyol to the molar ratio of the dianhydride is 1:(1 to 1.1), for example, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.07 or 1:1.09, etc.
[0020] Preferably, the dianhydride comprises an aromatic tetracarboxylic acid dianhydride.
[0021] Preferably, the aromatic tetracarboxylic acid dianhydride includes 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxobisphthalic acid anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, (4-phthalic anhydride)formyloxy-4-phthalate, bis[(3,4-dianhydride)phenyl]terephthalate, 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, p-phenylene-bisphenyltriester dianhydride, 4,4'-terephthalodioxybisphthalic acid anhydride, pyromellitic dianhydride, and 2,2'-bis(3,4-dicarboxylic acid) The mixture comprises any one or a combination of at least two of the following: hexafluoropropane dianhydride, 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane dianhydride, 2,2-bis(4-(3,4-dicarboxybenzoyloxy)phenyl)hexafluoropropane dianhydride, or 2,2'-bis(trifluoromethyl)-4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, and more preferably any one or a combination of at least two of the following: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, or 4,4'-terephthalic anhydride.
[0022] Preferably, the present invention does not have special requirements on the type of catalyst used, and can exemplary select any one or a combination of at least two of isoquinoline, N-methylmorpholine, triethylenediamine, isoquinoline or triethylamine.
[0023] Preferably, the raw materials for preparing the water-soluble polyimide adhesive also include a solvent.
[0024] Preferably, the solvent is a nonprotonated polar solvent.
[0025] Preferably, the aprotic polar solvent includes any one or a combination of at least two of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, ethyl acetate, toluene, or methyl ethyl ketone, and more preferably N,N-dimethylformamide and / or N,N-dimethylacetamide.
[0026] In a second aspect, the present invention provides a method for preparing a water-soluble polyimide adhesive as described in the first aspect, the method comprising the following steps:
[0027] (1) The polyol and a portion of the dianhydride are reacted in a solvent to obtain an intermediate product;
[0028] (2) The intermediate product obtained in step (1), the carboxyl-containing diamine, the carboxyl-free diamine, the remaining dianhydride and the catalyst are reacted to obtain the water-soluble polyimide binder.
[0029] Preferably, the reactions described in steps (1) and (2) are carried out under the protection of a protective gas.
[0030] Preferably, the protective gas includes nitrogen or argon.
[0031] Preferably, the reaction temperature in step (1) is 50 to 120°C, such as 60°C, 70°C, 80°C, 90°C, 100°C or 110°C, and more preferably 60 to 105°C.
[0032] Preferably, the reaction time in step (1) is 1 to 24 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours or 22 hours, and more preferably 3 to 10 hours.
[0033] Preferably, after the reaction in step (2) is completed, the process further includes the steps of settling, washing and drying the obtained reaction solution in ethanol.
[0034] As a preferred embodiment of the present invention, the preparation method of the water-soluble polyimide adhesive includes the following steps:
[0035] (1) Under the protection of a protective gas, a polyol and a portion of a dianhydride are reacted in a solvent at a temperature of 50–120 °C for 1–24 h to obtain an intermediate product.
[0036] (2) The intermediate product obtained in step (1), the carboxyl-containing diamine, the carboxyl-free diamine, the remaining dianhydride and the catalyst are reacted. The reaction is stopped after no water is generated, and a reaction solution is obtained. The reaction solution is poured into ethanol for precipitation. The precipitate is washed with a large amount of ethanol and then vacuum dried to obtain the water-soluble polyimide adhesive.
[0037] As can be seen from the above, the water-soluble polyimide binder obtained by the method has had the solvent added during the reaction removed and is in the form of a dry powder. In other words, the water-soluble polyimide binder provided by the first aspect of the present invention does not contain solvent.
[0038] Meanwhile, the present invention does not impose special limitations on the reaction temperature described in step (2) above, and the conventional polyimide temperature can be used. In addition, xylene can be added in step (2) to make the water generated during the imide process azeotropic and carry the water out.
[0039] Thirdly, the present invention provides an aqueous polyimide adhesive slurry, the aqueous polyimide adhesive slurry comprising the water-soluble polyimide adhesive as described in the first aspect and water.
[0040] Preferably, the solid content of the waterborne polyimide adhesive slurry is 4-30%, 5%, 10%, 15%, 20% or 25%, and more preferably 6-15%.
[0041] Preferably, the viscosity of the waterborne polyimide adhesive slurry is 500 to 20000 cp, such as 1000 cp, 2000 cp, 5000 cp, 10000 cp, 12000 cp, 14000 cp, 16000 cp or 18000 cp, and more preferably 800 to 60000 cp.
[0042] Fourthly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a copper foil and a negative electrode paste adhered to the copper foil after drying;
[0043] The negative electrode slurry includes a negative electrode active material, a conductive agent, and an aqueous polyimide binder as described in the first aspect.
[0044] Preferably, the mass percentage of the aqueous polyimide binder in the negative electrode slurry is 0.1% to 10%, such as 0.5%, 1%, 2%, 4%, 6%, 8%, or 10%, and more preferably 0.5% to 5%.
[0045] Preferably, the negative electrode active material includes silicon-carbon active material.
[0046] Preferably, the mass percentage of the negative electrode active material in the negative electrode slurry is 0.1% to 10%, for example, 0.5%, 1%, 2%, 4%, 6%, or 8%.
[0047] Preferably, the mass percentage of conductive agent in the negative electrode slurry is 5% to 20%, such as 7%, 9%, 11%, 13%, 15%, 17%, or 19%.
[0048] Fifthly, the present invention provides a battery comprising a negative electrode as described in the fourth aspect.
[0049] Compared with the prior art, the present invention has the following beneficial effects:
[0050] (1) The raw materials for preparing the water-soluble polyimide binder provided by the present invention include a combination of carboxyl-containing diamine, carboxyl-free diamine, polyol, dianhydride and catalyst; by selecting the carboxyl-containing diamine and the carboxyl-free diamine for combination and adding polyol, the final polyimide has excellent solubility in water and excellent mechanical properties, and also has excellent bonding properties to a variety of metals and carbon materials, so that the battery prepared by the negative electrode sheet made of the water-soluble polyimide binder can exhibit excellent charge-discharge performance and cycle stability.
[0051] (2) By further limiting the molar ratio of carboxyl diamine and carboxyl-free diamine, the present invention can make the 180° peel force of the negative electrode sheet containing the water-soluble polyimide binder reach 48 to 78 N / m, and further make the battery have an initial charge capacity of 941 to 973 mAh / g, an initial efficiency of 86 to 91%, and a capacity retention rate of 79 to 85% after 200 cycles. Detailed Implementation
[0052] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.
[0053] Example 1
[0054] A water-soluble polyimide adhesive, the preparation method of which includes the following steps:
[0055] (1) Under nitrogen protection, polyethylene glycol (8g, number average molecular weight 800) and pyromellitic dianhydride (2.18g) in a molar ratio of 1:1 were added to a reaction vessel containing NMP (57.68g) and reacted at 60°C for 8h to obtain an intermediate product.
[0056] (2) Then, 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid (2.72g), 4,4'-diaminodiphenyl ether (4g) and pyromellitic dianhydride (6.54g) in a molar ratio of 1:2:3 were added to the reaction vessel, along with NMP (173g), isoquinoline (0.129g) and xylene (50g). The reaction was carried out at 180°C until no more water was generated, and the reaction was stopped. After the reaction solution was cooled to room temperature, the reaction solution was poured into ethanol to settle, and then washed repeatedly with a large amount of ethanol three times and dried under vacuum to obtain the water-soluble polyimide adhesive.
[0057] Example 2
[0058] A water-soluble polyimide adhesive differs from Example 1 only in that an equimolar amount of ethylene glycol is used instead of polyethylene glycol; all other substances, amounts, and preparation methods are the same as in Example 1.
[0059] Example 3
[0060] A water-soluble polyimide adhesive differs from Example 1 only in that 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid is replaced with an equimolar amount of 3,5-diaminobenzoic acid; all other substances, amounts, and preparation methods are the same as in Example 1.
[0061] Example 4
[0062] A water-soluble polyimide adhesive differs from Example 1 only in that equimolar amounts of ethylene glycol are used instead of polyethylene glycol, and equimolar amounts of 3,5-diaminobenzoic acid are used instead of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid. All other substances, amounts, and preparation methods are the same as in Example 1.
[0063] Example 5
[0064] A water-soluble polyimide adhesive differs from Example 1 only in that, while keeping the total amount of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether constant, the molar ratio of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether is adjusted to 1:1.5. All other substances, amounts, and preparation methods are the same as in Example 1.
[0065] Example 6
[0066] A water-soluble polyimide adhesive differs from Example 1 only in that, while keeping the total amount of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether constant, the molar ratio of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether is adjusted to 1:4.5. All other substances, amounts, and preparation methods are the same as in Example 1.
[0067] Example 7
[0068] A water-soluble polyimide adhesive differs from Example 1 only in that, while keeping the total amount of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether constant, the molar ratio of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether is adjusted to 1:0.5. All other substances, amounts, and preparation methods are the same as in Example 1.
[0069] Example 8
[0070] A water-soluble polyimide adhesive differs from Example 1 only in that, while keeping the total amount of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether constant, the molar ratio of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether is adjusted to 1:7. All other substances, amounts, and preparation methods are the same as in Example 1.
[0071] Comparative Example 1
[0072] A polyimide adhesive differs from Example 1 only in that the total amount of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether remains unchanged, and 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid is not added. All other substances, amounts, and preparation methods are the same as in Example 1.
[0073] Comparative Example 2
[0074] A polyimide adhesive differs from Example 1 only in that the total amount of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid and 4,4'-diaminodiphenyl ether remains unchanged, but 4,4'-diaminodiphenyl ether is not added. All other substances, amounts, and preparation methods are the same as in Example 1.
[0075] Comparative Example 3
[0076] A polyimide adhesive is prepared by means of the following method: under nitrogen protection, 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid (2.72 g), 4,4'-diaminodiphenyl ether (4 g), and pyromellitic dianhydride (6.54 g) in a molar ratio of 1:2:3 are added to a reaction vessel, isoquinoline (0.129 g) and xylene (50 g) are added, and the reaction is carried out at 180°C. The reaction is stopped after no water is generated. After the reaction solution is cooled to room temperature, the reaction solution is poured into ethanol to settle, and then washed repeatedly with a large amount of ethanol three times and vacuum dried to obtain the water-based polyimide.
[0077] Application Example 1
[0078] A negative electrode sheet, the preparation method of which includes the following steps:
[0079] (1) Preparation of water-based adhesive slurry: The water-soluble polyimide adhesive obtained in Example 1 was dissolved in deionized water to obtain a water-based adhesive slurry with a solid content of 20% and a viscosity of 3000cp;
[0080] (2) Preparation of negative electrode slurry: Silicon carbon active material DXA5 (BTR New Materials Co., Ltd.), conductive additive SuperP and water-based binder slurry obtained in step (1) are mixed uniformly under high speed stirring and degassed; wherein, the mass ratio of silicon carbon active material DXA5, conductive additive SuperP and water-soluble polyimide binder (solid component) is 90:8.5:1.5;
[0081] (3) Preparation of negative electrode sheet: The negative electrode slurry obtained in step (2) is coated on copper foil, and after being thoroughly dried by heating at 110°C for 1 hour, it is stamped to prepare the negative electrode sheet.
[0082] Application Examples 2-8
[0083] A negative electrode sheet, which differs from Application Example 1 only in that the water-soluble polyimide binder obtained in Examples 2 to 8 is used instead of the water-soluble polyimide binder obtained in Example 1, while the other conditions and steps are the same as in Application Example 1.
[0084] Comparative Application Examples 1-3
[0085] A negative electrode sheet, which differs from Application Example 1 only in that the polyimide binder obtained in Comparative Examples 1 to 3 is used instead of the water-soluble polyimide binder obtained in Example 1, while the other conditions and steps are the same as in Application Example 1.
[0086] Performance testing:
[0087] (1) 180° peel force: The test was conducted in accordance with the test method provided in the national standard GB / T 2792-199;
[0088] (2) Electrical performance: The button cell was assembled in a glove box. The positive electrode active material of the button cell was LiFePO4, the separator was Celgard 2320, and the electrolyte was 1M LiFP6 (EC:DEC = 1:1 v / v). The assembly sequence was positive electrode shell, positive electrode plate, electrolyte, separator, electrolyte, negative electrode plate, steel plate, spring plate, and negative electrode shell. Before the full cell assembly, half cells were assembled for activation pretreatment. The mass ratio of the active materials of the positive and negative electrodes was about 1:1.
[0089] Five batteries were made from each type of negative electrode sheet, and the button cells prepared above were connected to a potential tester for charge-discharge testing. The potential range was 0 to 2V, and a constant current of 0.5C was used for cyclic testing to test the initial charge capacity, initial charge efficiency, and capacity retention rate after 200 cycles.
[0090]
[0091] The tests were conducted according to the above test methods, corresponding to test cases 1-8 and comparative application examples 1-3. The test results are shown in Table 1.
[0092] Table 1
[0093]
[0094] According to the data in Table 1:
[0095] The negative electrode sheets provided in Application Examples 1 to 6 have a 180° peel force of 48 to 78 N / m, and the batteries further manufactured have an initial charge capacity of 941 to 973 mAh / g, an initial efficiency of 86 to 91%, and a capacity retention rate of 79 to 85% after 200 cycles.
[0096] Comparing Application Example 1 and Comparative Application Example 1 reveals that the negative electrode sheet obtained without adding a carboxyl-containing diamine has very low peel strength, and the initial charge capacity, initial efficiency, and 200-cycle capacity retention rate of the battery further prepared all decrease. Comparing Application Example 2 and Comparative Application Example 3 reveals that although the negative electrode sheet obtained without adding a carboxyl-free diamine has high peel strength, it leads to a very low 200-cycle capacity retention rate of the battery further prepared. Finally, comparing Application Example 3 and Comparative Application Example 4 also reveals that the negative electrode sheet obtained without adding a polyol has low peel strength, and the initial charge capacity, initial efficiency, and 200-cycle capacity retention rate of the battery prepared are all poor.
[0097] Further comparison of the data from Application Example 1 and Application Examples 5-8 reveals that the molar ratio of carboxyl-containing diamines to carboxyl-free diamines also affects the peeling force of the negative electrode and the electrical performance of the battery.
[0098] The applicant declares that this invention illustrates a water-soluble polyimide adhesive, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials in the product of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection and disclosure scope of this invention.
Claims
1. A water-soluble polyimide adhesive, characterized in that, The raw materials for preparing the water-soluble polyimide adhesive include carboxyl-containing diamines, carboxyl-free diamines, polyols, dianhydrides, and catalysts. The molar ratio of the carboxyl-free diamine, the carboxyl-containing diamine, and the polyol is 1:(1~6):(1~3); The polyols include diols; The water-soluble polyimide adhesive is prepared by the following method, which includes the following steps: (1) The polyol and a portion of the dianhydride are reacted in a solvent to obtain an intermediate product; (2) The intermediate product obtained in step (1), the carboxyl-containing diamine, the carboxyl-free diamine, the remaining dianhydride and the catalyst are reacted to obtain the water-soluble polyimide binder.
2. The water-soluble polyimide adhesive according to claim 1, characterized in that, The molar ratio of the carboxyl-free diamine, the carboxyl-containing diamine, and the polyol is 1:(1.5~4.5):(1.2~2).
3. The water-soluble polyimide adhesive according to claim 1, characterized in that, The carboxyl-free diamine includes any one or a combination of at least two of the following: p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 4,4'-diaminobenzoylaniline, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 4,4'-diaminodiphenyl sulfone, 2-(4-aminophenyl)-5-aminobenzimidazole, 2,2-bis(4-hydroxy-3-aminophenyl)propane, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-biphenyl, or 9,9-bis(4-aminophenyl)fluorene.
4. The water-soluble polyimide adhesive according to claim 1, characterized in that, The carboxyl-containing diamine includes any one or a combination of at least two of 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid, 6,6'-diamino-3,3'-methylenedibenzoic acid, or 3,5-diaminobenzoic acid.
5. The water-soluble polyimide adhesive according to claim 1, characterized in that, The polyol is any one or a combination of at least two of ethylene glycol, propylene glycol, butylene glycol, or polyethylene glycol.
6. The water-soluble polyimide adhesive according to claim 5, characterized in that, The number average molecular weight of the polyethylene glycol is 100 to 50,000.
7. The water-soluble polyimide adhesive according to claim 6, characterized in that, The number average molecular weight of the polyethylene glycol is 200-3000.
8. The water-soluble polyimide adhesive according to claim 1, characterized in that, The total molar ratio of the carboxyl-containing diamine, the non-carboxyl-containing diamine, and the polyol to the molar ratio of the dianhydride is 1:(1~1.1).
9. The water-soluble polyimide adhesive according to claim 1, characterized in that, The dianhydride includes aromatic tetracarboxylic acid dianhydride.
10. The water-soluble polyimide adhesive according to claim 9, characterized in that, The aromatic tetracarboxylic dianhydrides include 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxobisphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, (4-phthalic anhydride)formyloxy-4-phthalate, bis[(3,4-dianhydride)phenyl]terephthalate, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, and p-phenylene-bisphenyltriester. The anhydride, 4,4'-terephthalodioxydiphthalic anhydride, pyromellitic dianhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane dianhydride, 2,2-bis(4-(3,4-dicarboxybenzoyloxy)phenyl)hexafluoropropane dianhydride, or 2,2'-bis(trifluoromethyl)-4,4'-bis(3,4-dicarboxyphenoxy)biphenyl anhydride, or any one or a combination of at least two of these anhydrides.
11. The water-soluble polyimide adhesive according to claim 10, characterized in that, The aromatic tetracarboxylic acid dianhydride is any one or a combination of at least two of the following: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, or 4,4'-terephthalodioxydiphthalic anhydride.
12. The water-soluble polyimide binder according to claim 1, characterized in that, The raw materials for preparing the water-soluble polyimide adhesive also include solvents.
13. The water-soluble polyimide adhesive according to claim 12, characterized in that, The solvent is a nonprotonated polar solvent.
14. The water-soluble polyimide adhesive according to claim 13, characterized in that, The nonprotonated polar solvent includes any one or a combination of at least two of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, γ-butyrolactone, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, ethyl acetate, toluene, or methyl ethyl ketone.
15. The water-soluble polyimide adhesive according to claim 14, characterized in that, The deprotonated polar solvent is N,N-dimethylformamide and / or N,N-dimethylacetamide.
16. A method for preparing a water-soluble polyimide adhesive as described in any one of claims 1 to 15, characterized in that, The preparation method includes the following steps: (1) The polyol and a portion of the dianhydride are reacted in a solvent to obtain an intermediate product; (2) The intermediate product obtained in step (1), the carboxyl-containing diamine, the carboxyl-free diamine, the remaining dianhydride and the catalyst are reacted to obtain the water-soluble polyimide binder.
17. The preparation method according to claim 16, characterized in that, The reactions described in steps (1) and (2) are both carried out under the protection of a protective gas.
18. The preparation method according to claim 17, characterized in that, The protective gas includes nitrogen or argon.
19. The preparation method according to claim 16, characterized in that, The reaction temperature in step (1) is 50~120℃.
20. The preparation method according to claim 19, characterized in that, The reaction temperature in step (1) is 60~105℃.
21. The preparation method according to claim 16, characterized in that, The reaction time in step (1) is 1 to 24 hours.
22. The preparation method according to claim 21, characterized in that, The reaction time in step (1) is 3 to 10 hours.
23. The preparation method according to claim 16, characterized in that, After the reaction in step (2) is completed, the steps of settling, washing and drying the reaction solution in ethanol are also included.
24. A water-based polyimide adhesive slurry, characterized in that, The water-based polyimide binder slurry comprises the water-soluble polyimide binder as described in any one of claims 1 to 15 and water.
25. The waterborne polyimide adhesive slurry according to claim 24, characterized in that, The solid content of the water-based polyimide adhesive slurry is 4-30%.
26. The waterborne polyimide adhesive slurry according to claim 25, characterized in that, The solid content of the waterborne polyimide adhesive slurry is 6-15%.
27. The waterborne polyimide adhesive slurry according to claim 24, characterized in that, The viscosity of the water-based polyimide adhesive slurry is 500~20000 cp.
28. The waterborne polyimide adhesive slurry according to claim 27, characterized in that, The viscosity of the water-based polyimide adhesive slurry is 800~18000 cp.
29. A negative electrode sheet, characterized in that, The negative electrode sheet includes a copper foil and a negative electrode paste that is dried and adhered to the copper foil; The negative electrode slurry includes a negative electrode active material, a conductive agent, and a water-soluble polyimide binder as described in any one of claims 1 to 15.
30. The negative electrode sheet according to claim 29, characterized in that, The mass percentage of water-based polyimide binder in the negative electrode slurry is 0.1-10%.
31. The negative electrode sheet according to claim 30, characterized in that, The mass percentage of water-based polyimide binder in the negative electrode slurry is 0.5-5%.
32. The negative electrode sheet according to claim 29, characterized in that, The negative electrode active material includes silicon-carbon active materials.
33. A battery, characterized in that, The battery includes a negative electrode as described in any one of claims 29-32.