Binder for high-performance diaphragm, preparation method and diaphragm using binder

Abstract

The invention discloses a binder for a high-performance diaphragm, a preparation method of the binder and the diaphragm using the binder, and belongs to the technical field of secondary batteries. The binder is composed of sulfonated polyaromatic polymer salt, raw materials of the binder comprise a polymer, a sulfonating agent and a neutralizer, and the polymer comprises polyether-ether-ketone, polyaryletherketone, polyphenyl ether, polyimide and aromatic and semi-aromatic polyamide; the preparation method comprises the following steps: dissolving at least one of the polymers in sulfolane; adding a sulfonating agent for sulfonation reaction; slowly dropwise adding a neutralizing agent for neutralization and salification precipitation; and finally, carrying out fine purification through dialysis filtration or gradient solvent washing, and reducing the residual quantity of sulfolane to 100 ppm or below. The binder is low in molecular weight degradation rate, is applied to a ceramic coating diaphragm and is synergistically applied with sulfolane or a high-voltage electrolyte, so that the thermal stability, the oxidation stability and the rate capability of a battery can be remarkably improved, and the binder is particularly suitable for a high-voltage lithium / sodium battery system of 4.5 V or above.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a high-performance separator adhesive, a preparation method thereof, and a separator using the adhesive. Background Technology

[0002] As the mainstream electrochemical energy storage device, lithium-ion batteries continuously strive for high energy density and safety. Increasing the battery's operating voltage is one effective way to improve energy density, but this places stringent requirements on the high-voltage oxidation stability of the various components within the battery. As a key internal component of the battery, the ceramic coating on the separator's surface is crucial for improving its thermal stability and mechanical strength, and the performance of the coating largely depends on the binder used.

[0003] Currently, the binders widely used in separator ceramic coatings, such as polyvinylidene fluoride (PVDF) and styrene-butadiene rubber (SBR), typically require the use of toxic, highly volatile organic solvents (VOCs) such as N-methylpyrrolidone (NMP) for coating, posing environmental and safety hazards. Furthermore, these traditional binders have limited oxidation potential and are prone to decomposition under high voltage conditions above 4.5V, leading to coating powdering and detachment, and potentially causing safety issues such as internal short circuits in the battery.

[0004] Sulfonated aromatic polymers possess excellent thermal and chemical stability due to their aromatic backbone structure, and the sulfonic acid groups enhance their affinity for lithium ions, making them potential candidates for high-performance binders. However, traditional sulfonation processes typically use concentrated sulfuric acid or fuming sulfuric acid as the sulfonation medium, resulting in vigorous and difficult-to-control reactions. This easily leads to severe chain scission and degradation of the polymer backbone, such as ether and imide bonds, causing a significant decrease in the molecular weight of the product and deterioration of its mechanical properties. Furthermore, subsequent complex and energy-intensive purification steps are required to remove residual acids and salts, making the process cumbersome and difficult to obtain high-purity final products, thus hindering their large-scale application.

[0005] Therefore, there is an urgent need to develop a high-performance membrane binder that is environmentally friendly, has controllable processes, can maintain high molecular weight and high purity, and is compatible with high-voltage electrolyte systems. Summary of the Invention

[0006] The purpose of this invention is to provide a high-performance adhesive for diaphragms, which solves the problems of inefficiency, high cost, non-compliance with green development, and inability to produce synergistic effects with high-voltage electrolytes in the existing sulfonation process.

[0007] Another objective of this invention is to provide a method for preparing a high-performance diaphragm adhesive.

[0008] Another object of the present invention is to provide a diaphragm comprising a high-performance diaphragm adhesive.

[0009] In a first aspect, the present invention provides a high-performance adhesive for diaphragms, which is composed of a sulfonated polyaromatic polymer salt; the raw materials for the sulfonated polyaromatic polymer salt include a polymer, a sulfonating agent, and a neutralizing agent; The polymers include one or more of polyetheretherketone, polyaryletherketone, polyphenylene ether, polyimide, and aromatic and semi-aromatic polyamides.

[0010] Preferably, the sulfonating agent is chlorosulfonic acid.

[0011] Preferably, the neutralizing agent is an alkaline aqueous solution.

[0012] More preferably, the alkaline aqueous solution includes Li + Na + Ca 2+ K + One or more of the following: an alkaline aqueous solution or ammonia solution.

[0013] Preferably, the molar ratio of polymer to chlorosulfonic acid is 1:(0.5-8).

[0014] More preferably, the molar ratio of polymer to chlorosulfonic acid is 1:(1-5).

[0015] Secondly, the present invention also provides a method for preparing a high-performance membrane adhesive, comprising the following steps: S1. Add the polymer to sulfolane and stir to obtain a polymer solution and / or dispersion; S2. Add a sulfonating agent to the polymer solution and / or dispersion, and react to obtain a sulfonated polymer solution; S3. Slowly add a neutralizing agent to the sulfonated polymer solution and stir until a precipitate is formed to achieve in-situ salt formation. Filter and purify to obtain the final product.

[0016] Preferably, in step S1, the mass concentration of the polymer in sulfolane is 2% to 45%.

[0017] Preferably, in step S2, the reaction temperature is 50–90°C and the reaction time is 2–8 h.

[0018] Preferably, in step S3, purification includes dialysis filtration and gradient solvent washing; the gradient solvent washing is performed sequentially using water, a water-alcohol mixture, alcohol, and diethyl ether.

[0019] Preferably, the water-ethanol mixture is deionized water and ethanol in a volume ratio of (1-3):1.

[0020] Preferably, the residual amount of sulfolane in the purified high-performance membrane binder is below 500 ppm.

[0021] More preferably, the residual amount of sulfolane in the purified high-performance membrane binder is less than 100 ppm.

[0022] Thirdly, the present invention also provides an adhesive diaphragm, comprising a base film and a ceramic coating coated on at least one surface of the base film, wherein the ceramic coating contains a high-performance diaphragm adhesive.

[0023] Preferably, in the ceramic coating, the mass ratio of ceramic powder to high-performance membrane binder is (95-99):(1-5).

[0024] The beneficial effects of this invention are: 1. This invention selects sulfonation in a sulfolane medium, which offers mild conditions and is easy to control precisely. Compared to the strong oxidizing and acidic environment of concentrated sulfuric acid, the sulfolane medium effectively inhibits the attack and breakage of ether and imide bonds on the main chains of polymers such as polyether ether ketone and polyimide during sulfonation, thereby significantly reducing the degradation rate of the polymer and obtaining sulfonated polymer products with high molecular weight and high structural integrity. This lays the foundation for providing excellent mechanical strength and adhesion as an adhesive. The sulfonated products can be neutralized by alkaline aqueous solution, achieving "in-situ salt formation and precipitation" of polymer sulfonates, avoiding the dependence on large amounts of toxic organic solvents in traditional PVDF / NMP systems or subsequent treatments. The entire preparation and coating process can be water-based, conforming to the development trend of green chemistry.

[0025] 2. This invention employs dialysis filtration or gradient solvent washing as a fine purification method. Dialysis filtration efficiently retains large polymer salt molecules while allowing small inorganic salt molecules and the solvent sulfolane to pass through, thus achieving deep purification. Gradient solvent washing selectively removes impurities through changes in solvent polarity. These methods can control the sulfolane content below 500 ppm, ensuring the high purity of the binder product. Importantly, the trace amounts of sulfolane remaining in the binder can form a synergistic system with the electrolyte when applied to high-voltage electrolytes containing sulfolane components, transforming it into a compatible component beneficial to the electrolyte system and improving overall compatibility.

[0026] 4. The binder of this invention is composed of sulfonated polymer salts with a backbone of PEEK, PI, etc., which possess extremely high thermal and oxidation stability and are compatible with high-voltage cathode materials above 4.5V. Its lithium / sodium sulfonate groups enhance the coating's affinity for lithium / sodium ions, reduce ion migration resistance, and thus improve the battery's rate performance. When this binder is used in conjunction with a sulfolane-based high-voltage electrolyte, the two form a synergistic system with matched performance at the interface, further enhancing interfacial stability under high voltage and jointly ensuring the battery's long-term safe operation under high voltage and wide temperature range. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0028] A high-performance membrane adhesive is composed of a sulfonated polyaromatic polymer salt; the raw materials for the sulfonated polyaromatic polymer salt include a polymer, a sulfonating agent, and a neutralizing agent. The polymers include one or more of polyetheretherketone, polyaryletherketone, polyphenylene ether, polyimide, and aromatic and semi-aromatic polyamides.

[0029] By employing the above technical solution, a membrane adhesive is prepared using sulfonated polyaromatic polymer salts. Sulfonated polyaromatic polymer salts are products obtained by sulfonation and salt formation reactions of polymers with rigid aromatic backbones. The raw materials for sulfonated polyaromatic polymer salts include polymers, sulfonating agents, and neutralizing agents. The polymers include one or more of polyetheretherketones, polyaryletherketones, polyphenylene ethers, polyimides, and aromatic and semi-aromatic polyamides. Their backbones consist of stable aromatic ring structures linked together, inherently possessing excellent thermal stability and chemical inertness. This provides a structural basis for the stable use of the adhesive under high-temperature and high-pressure oxidizing conditions in batteries. The raw material system of sulfonated polyaromatic polymer salts is simple and clear. The polymer, as the main skeleton, determines the basic mechanical and stability properties of the adhesive. The sulfonating agent is used to introduce functional sulfonic acid groups, and the neutralizing agent realizes the salt formation conversion and green separation of the product. These three components work synergistically to ensure the performance of the adhesive and the environmental friendliness of the preparation process.

[0030] By sulfonating polymers with sulfonating agents, sulfonic acid groups can be precisely introduced into the stable main chain of polyaromatic polymers, a key step in endowing the adhesive with functionality. Sulfonic acid groups possess strong polarity and hydrophilicity, which significantly enhances the adhesive's affinity for lithium / sodium ions, providing channels for ion migration within the membrane coating and reducing ion migration resistance. Furthermore, it improves the interfacial interaction between the adhesive and the ceramic powder and membrane substrate, enhancing the coating's adhesion and bonding strength. Crucially, this invention confines the sulfonation reaction to a sulfolane medium. Compared to traditional concentrated sulfuric acid, the weak oxidizing properties and mild acidic environment of sulfolane effectively regulate the sulfonation reaction rate, preventing over-sulfonation or side reactions, ensuring the sulfonic acid groups are uniformly distributed on the polymer main chain, and maximizing the protection of the main chain structure's integrity, avoiding the breakage of critical bonds such as ether bonds and imide bonds.

[0031] Neutralizing agents can convert sulfonated polymers generated during the sulfonation reaction into sulfonates, achieving the green separation goal of "in-situ salt formation and precipitation." Unneutralized sulfonated polymers have poor water solubility, and their acidic groups may corrode internal battery components. Neutralization to sulfonates not only eliminates the risk of acid corrosion but also further optimizes the solubility and dispersibility of the product, laying the foundation for subsequent water-based coating processes. Simultaneously, the polymer sulfonates generated during the neutralization reaction precipitate directly without the need for separation and purification using toxic organic solvents, significantly simplifying the preparation process, reducing environmental and safety hazards, and perfectly aligning with the development trend of green chemistry.

[0032] In some embodiments, the sulfonating agent is chlorosulfonic acid. Chlorosulfonic acid is a highly efficient electrophilic sulfonating agent with moderate sulfonating activity. In sulfolane media, it can undergo precise electrophilic substitution reactions with the aromatic rings of polyaromatic polymers, effectively controlling the introduction position and degree of sulfonation of sulfonic acid groups. Compared to other sulfonating agents such as concentrated sulfuric acid and fuming sulfuric acid, chlorosulfonic acid exhibits stronger reaction selectivity, is less likely to induce chain scission and degradation of the polymer backbone, and better preserves the high molecular weight characteristics of the polymer, thereby ensuring the mechanical strength of the binder. Simultaneously, chlorosulfonic acid has good solubility in sulfolane and can be uniformly dispersed in the reaction system, ensuring uniform sulfonation and avoiding localized over- or under-sulfonation, resulting in more stable performance of the final product.

[0033] In some embodiments, the neutralizing agent is an alkaline aqueous solution; more preferably, the alkaline aqueous solution includes Li + Na + Ca 2 + K + One or more alkaline aqueous solutions or ammonia solutions are used. Using an alkaline aqueous solution as a neutralizing agent allows for the gentle neutralization and salt formation of the sulfonated polymer, avoiding problems such as violent localized reactions and product structure damage that may occur with the use of highly corrosive solid alkalis. The good fluidity of the alkaline aqueous solution allows for sufficient contact with the sulfonated polymer solution, ensuring complete neutralization and improving product conversion rate. More preferably, Li-containing solutions are used. + Na + An isocationic alkaline aqueous solution has the advantage of containing cations such as Li in the sulfonate salts formed after neutralization. + It can work synergistically with lithium ions in the battery system without introducing harmful impurity ions, thus avoiding negative impacts on the electrochemical performance of the battery. When ammonia is used as a neutralizing agent, its decomposition products are ammonia gas and water, with no residual impurities, which can also ensure the purity of the binder.

[0034] In some embodiments, the molar ratio of polymer to chlorosulfonic acid is 1:(0.5-8); more preferably, the molar ratio of polymer to chlorosulfonic acid is 1:(1-5). This molar ratio range can meet actual performance requirements. When the molar ratio is less than 1:1, the amount of chlorosulfonic acid is insufficient, the sulfonation reaction is incomplete, and the number of sulfonic acid groups introduced on the polymer backbone is too small, which cannot effectively achieve functional goals such as enhancing ion affinity and improving adhesion strength, leading to deterioration of binder performance. When the molar ratio is greater than 1:5, there is an excessive amount of chlorosulfonic acid, which not only wastes raw materials and increases the burden of subsequent purification, but may also trigger an over-sulfonation reaction, leading to damage to the polymer backbone structure, a decrease in molecular weight, and a significant reduction in mechanical properties. At the same time, excessive chlorosulfonic acid may also remain in the product, adversely affecting battery performance. The molar ratio range of 1:(1-5) can ensure that the sulfonation reaction can be carried out fully and controllably under different polymer types and different sulfonation degree requirements, so that the sulfonation degree of the final product is within a suitable range, taking into account the mechanical strength, ion conduction performance, and chemical stability of the binder.

[0035] A method for preparing a high-performance membrane adhesive, characterized by comprising the following steps: S1. Add the polymer to sulfolane and stir to obtain a polymer solution and / or dispersion; S2. Add a sulfonating agent to the polymer solution and / or dispersion, and react to obtain a sulfonated polymer solution; S3. Slowly add a neutralizing agent to the sulfonated polymer solution and stir until a precipitate is formed to achieve in-situ salt formation. Filter and purify to obtain the final product.

[0036] By adopting the above technical solution, in step S1, the polymer is added to sulfolane and stirred to ensure that the polymer is fully dissolved or uniformly dispersed, creating conditions for the uniform sulfonation reaction in the subsequent process. Sulfolane, as a good solvent, can effectively dissolve or disperse the selected polyaromatic polymer, and its chemical properties are stable, preventing side reactions with the polymer and providing a stable medium environment for the reaction. Step S2 is crucial for the introduction of functional groups. After adding the sulfonating agent to the polymer solution / dispersion, the sulfonic acid groups can be controllably grafted onto the polymer backbone by controlling the reaction conditions, avoiding backbone degradation and ensuring the high molecular weight characteristics of the product. In step S3, the pH value of the reaction system can be stably controlled by slowly adding a neutralizing agent, avoiding excessive local alkalinity that could damage the polymer backbone. At the same time, the sulfonated polymer is converted to sulfonate and precipitated in situ. Subsequent filtration and purification steps further remove impurities, ensuring product purity.

[0037] In some embodiments, in step S1, the polymer concentration in sulfolane is 2%–45% by mass. This concentration range ensures that the reaction system has a suitable viscosity, which is beneficial for mass transfer and uniform reaction, as well as for subsequent precipitation and purification. If the concentration is below 2%, the polymer content in the reaction system is too low, resulting in low sulfonation efficiency and low product yield per unit volume of reaction system. Furthermore, the dilute solution system increases the energy consumption and cost of subsequent separation and purification. If the concentration is above 45%, the viscosity of the polymer solution / dispersion will increase sharply, making stirring difficult and preventing the sulfonating agent from spreading evenly throughout the system. This can lead to incomplete local sulfonation reactions and inconsistent product performance. Excessive viscosity can also reduce the system's heat transfer efficiency, preventing the heat generated during the reaction from dissipating in time, causing localized temperature increases and side reactions, and damaging the polymer backbone structure. A concentration range of 2%–45% ensures that the reaction system has suitable fluidity, guaranteeing sufficient contact and uniform reaction between the sulfonating agent and the polymer.

[0038] In some embodiments, in step S2, the reaction temperature is 50–90°C, and the reaction time is 2–8 hours. 50°C is the effective starting temperature for the sulfonation reaction. Below this temperature, the sulfonation activity of chlorosulfonic acid is insufficient, the reaction rate is too slow, and it is difficult to achieve the target degree of sulfonation within a reasonable time. Above 90°C, excessively high temperatures will accelerate the degradation reaction of the polymer backbone, leading to a decrease in product molecular weight, deterioration of mechanical properties, and potentially over-sulfonation, disrupting the structural uniformity of the product. Regarding time, 2 hours is the minimum time requirement to achieve the basic degree of sulfonation; below this time, sulfonation is insufficient, and the number of sulfonic acid groups is inadequate. Within 8 hours, over-sulfonation and backbone degradation can be avoided. The combination of a temperature of 50–90°C and a time of 2–8 hours allows for controllable preparation of different target degrees of sulfonation, ensuring uniform sulfonation and an intact backbone structure, laying the foundation for the subsequent performance of the binder.

[0039] In some embodiments, step S3, purification includes dialysis filtration and gradient solvent washing; the gradient solvent washing sequentially uses water, a water-alcohol mixture, alcohol, and diethyl ether; the water-alcohol mixture is deionized water and ethanol in a volume ratio of (1-3):1; the purification strategy of dialysis filtration and gradient solvent washing can achieve deep purification of sulfonated polymer salts and efficiently remove impurities from the system. Dialysis filtration utilizes the sieving effect of a semi-permeable membrane to accurately retain large molecule sulfonated polymer salts while allowing small molecule impurities to be removed, offering advantages such as high purification efficiency, gentle operation, and no damage to the polymer structure. Gradient solvent washing achieves selective removal of impurities of different polarities through a gradual change in solvent polarity: first, washing with water can quickly remove water-soluble inorganic salts and some residual sulfolane; then, a water-alcohol mixture with a volume ratio of (1-3):1, whose polarity is between that of water and pure alcohol, can remove slightly hydrophobic organic impurities and some residual water-insoluble impurities; subsequently, washing with alcohol further removes organic impurities and dehydrates; finally, washing with ether can completely dehydrate and remove trace amounts of residual non-polar impurities.

[0040] In some embodiments, the residual amount of sulfolane in the purified high-performance membrane binder is below 500 ppm; more preferably, the residual amount of sulfolane is below 100 ppm. Strictly controlling the residual amount of sulfolane to below 500 ppm ensures the high purity of the binder product itself and avoids the potential negative impact of residual solvents on battery performance. More importantly, when trace amounts of residual sulfolane are applied to high-voltage electrolytes containing sulfolane components, they can be converted into beneficial compatibility components, forming a synergistic system with the electrolyte, improving interfacial compatibility, and realizing the resource utilization of "residual impurities." This residual amount control standard also reflects the high efficiency of the purification process of this invention. Through the synergistic effect of dialysis filtration and gradient solvent washing, this strict purification target can be stably achieved, providing a guarantee for the high-performance application of the binder.

[0041] An adhesive diaphragm includes a base membrane and a ceramic coating applied to at least one surface of the base membrane, the ceramic coating comprising a high-performance diaphragm adhesive.

[0042] By employing the above technical solution, applying a high-performance membrane binder to the ceramic coating of the membrane can significantly improve the overall performance of the membrane. The membrane base membrane, such as polyethylene or polypropylene, provides basic isolation and support, while the ceramic coating containing the binder serves as a functional enhancement layer. The binder is the core link maintaining the structural stability and performance of the ceramic coating. The binder of this invention, through its excellent bonding properties, firmly bonds ceramic powder to the surface of the base membrane, forming a dense, uniform, and strongly adherent ceramic coating, preventing powdering and detachment during battery assembly or cycling. Simultaneously, the binder's high heat resistance enhances the thermal stability of the ceramic coating, inhibiting base membrane shrinkage under high-temperature battery conditions and ensuring the membrane's isolation function. Its excellent high-pressure oxidation stability prevents decomposition under high-pressure conditions, ensuring the integrity of the coating structure. Furthermore, the ion affinity provided by its sulfonic acid groups optimizes ion conduction channels within the coating, reducing battery internal resistance and improving rate performance. By synergistically integrating binders with ceramic coatings and base films, high-performance separators with high safety, high stability, and excellent electrochemical performance can be prepared, making them suitable for high-voltage battery systems above 4.5V.

[0043] In some embodiments, the mass ratio of ceramic powder to high-performance membrane binder in the ceramic coating is (95-99):(1-5). The ceramic powder (such as alumina, boehmite, etc.) is the core component for improving the thermal stability and mechanical strength of the coating. A 95-99% proportion ensures the coating fully utilizes its advantages in high-temperature resistance and puncture resistance, providing reliable safety for the membrane. A binder proportion of 1-5% is sufficient to meet the coating's bonding requirements. This (95-99):(1-5) mass ratio achieves a precise balance between the safety performance of the ceramic powder and the functional performance of the binder. While ensuring the stability and safety of the coating structure, it minimizes the negative impact on the battery's electrochemical performance, while controlling production costs, making it suitable for large-scale applications.

[0044] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0045] Example

[0046] Example 1: A high-performance diaphragm adhesive was prepared by the following method: S1. Add sulfolane to the reaction flask, and slowly add polyether ether ketone while stirring, controlling the mass concentration of polyether ether ketone in the sulfolane solution to be 15%, and stir at 70°C for 3 hours. S2. Keep the reaction temperature at 70℃, add chlorosulfonic acid dropwise to the polyether ether ketone dispersion, and control the molar ratio of polyether ether ketone to chlorosulfonic acid to be 1:2. After the addition is complete, continue the reaction at a constant temperature for 5 hours to obtain a sulfonated polyether ether ketone solution. S3. Reduce the temperature of the sulfonated polyether ether ketone solution to 25°C, and slowly add 1M lithium hydroxide aqueous solution dropwise while stirring until no more precipitate is produced. Continue stirring for 1 hour to achieve in-situ salt formation. S4. Place the precipitate in a dialysis bag (molecular weight cutoff 10000) and dialyze for 72 hours using deionized water as the dialysis medium, changing the deionized water every 12 hours during this period. After dialysis, perform gradient solvent washing: soak and wash with deionized water for 2 hours, soak and wash with a 2:1 volume ratio deionized water-ethanol mixture for 2 hours, soak and wash with ethanol for 2 hours, and soak and wash with ether for 2 hours. Filter after each washing. Finally, place the washed precipitate in a vacuum drying oven and vacuum dry at 80°C for 12 hours to obtain a high-performance membrane binder.

[0047] The residual amount of sulfolane was determined by headspace GC using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 35 ppm.

[0048] Example 2, a high-performance membrane adhesive, differs from Example 1 only in that the molar ratio of polyether ether ketone and chlorosulfonic acid is 1:5.

[0049] The residual amount of sulfolane was determined by headspace gas chromatography (Headspace GC) using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 28 ppm.

[0050] Example 3, a high-performance membrane adhesive, differs from Example 1 only in that the molar ratio of polyether ether ketone and chlorosulfonic acid is 1:1.

[0051] The residual amount of sulfolane was determined by headspace GC using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 41 ppm.

[0052] Example 4: A high-performance diaphragm adhesive was prepared by the following method: S1. Add sulfolane to the reaction flask, and slowly add polyarylether ketone while stirring, controlling the mass concentration of polyarylether ketone in the sulfolane solution to be 8%, and stir at 60°C for 3 hours. S2. Keep the reaction temperature at 60℃, add chlorosulfonic acid dropwise to the polyaryletherketone solution, and control the molar ratio of polyaryletherketone to chlorosulfonic acid to be 1:1.2. After the addition is complete, continue the reaction at a constant temperature for 5 hours to obtain a sulfonated polyaryletherketone solution. S3. Reduce the temperature of the sulfonated polyaryletherketone solution to 25°C, slowly add 1M lithium hydroxide aqueous solution dropwise while stirring until no more precipitate is produced, and continue stirring for 1 hour to achieve in-situ salt formation. S4. Place the precipitate in a dialysis bag (molecular weight cutoff 10000) and dialyze for 72 hours using deionized water as the dialysis medium, changing the deionized water every 12 hours during this period. After dialysis, perform gradient solvent washing: soak and wash with deionized water for 2 hours, soak and wash with a 2:1 volume ratio deionized water-ethanol mixture for 2 hours, soak and wash with ethanol for 2 hours, and soak and wash with ether for 2 hours. Filter after each washing. Finally, place the washed precipitate in a vacuum drying oven and vacuum dry at 80°C for 12 hours to obtain a high-performance membrane binder.

[0053] The residual amount of sulfolane was determined by headspace GC using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 32 ppm.

[0054] Example 5: A high-performance diaphragm adhesive was prepared by the following method: S1. Add sulfolane to the reaction flask, and slowly add polyimide while stirring, controlling the mass concentration of polyimide in the sulfolane solution to be 30%, and stir at 90℃ for 5 hours. S2. Keep the reaction temperature at 90℃, add chlorosulfonic acid dropwise to the polyimide dispersion, and control the molar ratio of polyimide to chlorosulfonic acid to be 1:3. After the addition is complete, continue the reaction at a constant temperature for 7 hours to obtain a sulfonated polyimide solution. S3. Reduce the temperature of the sulfonated polyether ether ketone solution to 25°C, and slowly add 1M lithium hydroxide aqueous solution dropwise while stirring until no more precipitate is produced. Continue stirring for 1 hour to achieve in-situ salt formation. S4. Place the precipitate in a dialysis bag (molecular weight cutoff 10000) and dialyze for 72 hours using deionized water as the dialysis medium, changing the deionized water every 12 hours during this period. After dialysis, perform gradient solvent washing: soak and wash with deionized water for 2 hours, soak and wash with a 2:1 volume ratio deionized water-ethanol mixture for 2 hours, soak and wash with ethanol for 2 hours, and soak and wash with ether for 2 hours. Filter after each washing. Finally, place the washed precipitate in a vacuum drying oven and vacuum dry at 80°C for 12 hours to obtain a high-performance membrane binder.

[0055] The residual amount of sulfolane was determined by headspace GC using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 39 ppm.

[0056] Comparative Example

[0057] Comparative Example 1, a high-performance membrane adhesive, differs from Example 1 only in the molar ratio of polyetheretherketone and chlorosulfonic acid 1:0.3.

[0058] The residual amount of sulfolane was determined by headspace GC using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 68 ppm.

[0059] Comparative Example 2, a high-performance diaphragm adhesive, was prepared by the following method: 20g of vacuum-dried polyetheretherketone (PEEK) granules were slowly added to a reaction flask containing 500mL of concentrated sulfuric acid. The mixture was stirred for 12 hours under a nitrogen atmosphere to obtain a sulfonated PEEK solution. The solution was heated to 50°C and the reaction was continued for 6 hours. After the reaction was completed, the solution was cooled to room temperature, and ice water was slowly poured in while stirring to obtain white sulfonated PEEK fibers. The white fibers were washed several times with deionized water until the pH of the resulting aqueous solution was around 7. Finally, the white fibers were soaked in deionized water and stirred overnight. The washed precipitate was then placed in a vacuum drying oven and dried at 80°C for 12 hours.

[0060] Comparative Example 3, a high-performance membrane binder, differs from Example 1 only in that, after in-situ salt formation, the precipitate is washed with deionized water only.

[0061] The residual amount of sulfolane was determined by headspace GC using a quartz glass capillary column and an FID detector. The residual amount of sulfolane was found to be 541 ppm.

[0062] Application examples

[0063] The membrane binders prepared in Examples 1-5 and Comparative Examples 1-3 were formulated into ceramic slurries. 100g of alumina powder as ceramic material and 1g of sodium carboxymethyl cellulose as dispersant were added to 120g of deionized water. After stirring at 300rpm for 60min, 20g of membrane binder (solid content of about 15%) was added and stirred at 300rpm for 30min to obtain ceramic slurry. The ceramic slurry prepared in Examples 1-5 and Comparative Examples 1-3 was uniformly coated onto one side of the base membrane polyolefin lithium battery separator using a wire rod coater and dried to form a coating layer with a thickness of 1-2μm, thereby obtaining the corresponding separator.

[0064] Performance testing

[0065] 1. Heat shrinkage test: The diaphragms prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were cut into sizes of 5cm × 10cm and treated in a drying oven at 150°C for 30min. The transverse and longitudinal lengths of the diaphragms before and after baking were measured and the heat shrinkage rate was calculated. 2. Ionic conductivity test: The separators prepared in Examples 1-5 and Comparative Examples 1-3 were used to make 2016 button batteries. An appropriate amount of electrolyte (sulfolane:EC:EMC = 3:3:4, LiPF6, 1M) was added. The AC impedance was measured using an electrochemical workstation, and the result was σ = L / (Rb). A), where σ is the ionic conductivity (S). cm -1 L is the thickness of the diaphragm (cm); Rb is the intrinsic resistance of the diaphragm (Ω); A is the effective area (cm²). 2 ) 3. Cyclic performance test: The charging and discharging potential range is 3.5V to 4.9V. The charging process is constant current 1C to 4.9V, constant voltage charging at 4.9V to the cutoff current ≤0.05C, rest for 5min, 1C discharge to 3.5V, rest for 5min, and after 30 cycles of charging and discharging at 25℃, the cycle capacity retention rate is recorded.

[0066] Table 1 Performance test results

[0067] The above examples demonstrate that all embodiments of the present invention exhibit excellent and balanced performance. The low heat shrinkage rate of <1.7% indicates that the high thermal stability of the sulfonated polyaromatic polymer salt backbone effectively enhances the overall heat resistance of the coating and diaphragm. The high ionic conductivity directly benefits from the sulfonic acid groups introduced onto the polymer, which improve ion affinity and transport channels. In contrast, Comparative Example 1, due to insufficient sulfonation and fewer functional groups, failed to form a solution after salt formation, resulting in a significant decrease in ionic conductivity and adhesion performance. Comparative Example 2, using a strong acid medium for sulfonation, showed some performance, but the overall performance was still lower than the examples due to partial degradation of the backbone. Comparative Example 3, due to incomplete purification, had a sulfolane residue as high as 541 ppm, severely deteriorating the electrochemical environment and leading to poor ionic conductivity and cycling performance. This highlights the core technological value of the present invention: using a mild sulfolane medium to protect the integrity of the backbone and controlling residues through deep purification.

[0068] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A high-performance adhesive for membranes, characterized in that, It is composed of sulfonated polyaromatic polymer salts; the raw materials for the sulfonated polyaromatic polymer salts include polymers, sulfonating agents, and neutralizing agents; The polymer includes one or more of polyetheretherketone, polyaryletherketone, polyphenylene ether, polyimide, and aromatic and semi-aromatic polyamides.

2. The high-performance diaphragm adhesive according to claim 1, characterized in that, The sulfonating agent is chlorosulfonic acid; the neutralizing agent is an alkaline aqueous solution.

3. The high-performance diaphragm adhesive according to claim 1, characterized in that, The molar ratio of the polymer to chlorosulfonic acid is 1:(0.5-8).

4. A preparation method for preparing the high-performance membrane adhesive according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Add the polymer to sulfolane and stir to obtain a polymer solution and / or dispersion; S2. Add a sulfonating agent to the polymer solution and / or dispersion, and react to obtain a sulfonated polymer solution; S3. Slowly add a neutralizing agent to the sulfonated polymer solution and stir until a precipitate is formed to achieve in-situ salt formation. Filter and purify to obtain the final product.

5. The preparation method according to claim 4, characterized in that, In step S1, the mass concentration of the polymer in sulfolane is 2% to 45%.

6. The preparation method according to claim 4, characterized in that, In step S2, the reaction temperature is 50–90°C and the reaction time is 2–8 hours.

7. The preparation method according to claim 4, characterized in that, In step S3, the purification includes dialysis filtration and gradient solvent washing; the gradient solvent washing is performed sequentially using water, a water-alcohol mixture, alcohol, and diethyl ether.

8. The preparation method according to claim 4, characterized in that, The residual amount of sulfolane in the purified high-performance membrane binder is below 500 ppm.

9. An adhesive separator, comprising a base film and a ceramic coating applied to at least one surface of the base film, characterized in that, The ceramic coating includes a high-performance diaphragm adhesive as described in any one of claims 1-3.

10. The adhesive diaphragm according to claim 9, characterized in that, In the ceramic coating, the mass ratio of ceramic powder to the high-performance membrane binder is (95-99):(1-5).

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