Modified polytetrafluoroethylene material for electrolytic bath and preparation method of modified polytetrafluoroethylene material

Abstract

The invention provides a modified polytetrafluoroethylene material for an electrolytic bath and a preparation method thereof, and the modified polytetrafluoroethylene material for the electrolytic bath comprises the following raw material components in parts by weight: 100-120 parts of modified polytetrafluoroethylene resin, 5-15 parts of polyimide resin, 3-8 parts of fluorinated ceramic microspheres and 0.5-5 parts of fluorinated graphene. Through in-situ copolymerization of modified resin, high-speed mixing of the components, compaction, step-by-step sintering and multi-component compounding and synergism, creep relaxation resistance, compression resilience, mechanical strength and gas tightness of the material are greatly improved while excellent corrosion resistance of PTFE is maintained; and the sealing structure is particularly suitable for long-life sealing under harsh working conditions such as alkaline or PEM water electrolysis hydrogen production electrolytic cells and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a modified polytetrafluoroethylene material for electrolytic cells and its preparation method. Background Technology

[0002] Electrolysis of water to produce hydrogen, especially alkaline water electrolysis and PEM water electrolysis, is currently the mainstream technology for obtaining "green hydrogen." The electrolyzer, as its core equipment, directly affects hydrogen production efficiency, safety, and operating costs through its long-term sealing reliability.

[0003] Sealing gaskets are critical components that prevent leakage of media (such as alkaline solutions, high-purity water, hydrogen, and oxygen) from electrolytic cells. The internal conditions of electrolytic cells are extreme, typically involving high temperatures (60-90℃), high pressures (1-3 MPa or even higher), highly corrosive media (such as 30% KOH solution or acidic PEM environments), continuous tightening stress, and hydrogen permeation. This places extremely high demands on the comprehensive performance of sealing materials: they must possess excellent long-term creep relaxation resistance to maintain the sealing pressure, outstanding chemical corrosion resistance to resist media erosion, good compression resilience to compensate for thermal cycling and stress fluctuations, and extremely low gas permeability to ensure safety.

[0004] Polytetrafluoroethylene (PTFE) is widely used in the preparation of sealing materials due to its excellent chemical inertness, temperature resistance, and low coefficient of friction. However, pure PTFE has significant drawbacks: firstly, it has poor creep resistance (commonly known as "cold flow"), making it prone to plastic deformation under long-term stress, leading to seal failure; secondly, it has low hardness and insufficient resilience; and thirdly, it has poor thermal conductivity. These defects limit its application in high-end, long-life electrolytic cells.

[0005] To improve the performance of PTFE, filler modification is commonly employed. Common fillers include glass fiber, carbon fiber, graphite, molybdenum disulfide, and bronze powder. These modifications improve the mechanical strength or lubricity of PTFE to some extent, but often sacrifice other properties while enhancing one. For example, introducing inorganic fillers may reduce the corrosion resistance uniformity or increase brittleness of the material, and have limited effect on inhibiting the inherent slippage (creep) of PTFE molecular chains. Furthermore, conventional physical blending struggles to address the weak interfacial bonding between the filler and the PTFE matrix, making the interface a potential source of failure in long-term corrosive environments.

[0006] In recent years, research on nanomaterials and high-performance organic polymers as reinforcing phases for PTFE has deepened. Carbon nanotubes can improve strength and thermal conductivity, but are prone to aggregation; graphene can enhance barrier properties, but the layers tend to stack; polyimide resins can significantly improve temperature resistance and mechanical strength. However, how to efficiently and stably combine these reinforcing phases with the PTFE matrix and synergistically address the comprehensive requirements of creep resistance, corrosion resistance, and high sealing performance remains a technical challenge. Meanwhile, from a molecular design perspective, copolymerizing and modifying the PTFE chain structure to enhance its intrinsic creep resistance and forming chemical bonds with the nano-reinforcing phase is an effective way to achieve breakthrough performance, but related research and its application in electrolytic cell sealing materials are still insufficient.

[0007] Therefore, developing a long-life sealing material that combines excellent creep relaxation resistance, high strength, superior chemical corrosion resistance, and extremely low permeability, and is specifically suitable for harsh electrolytic cell conditions, has significant industrial application value. Summary of the Invention

[0008] Purpose of the invention: The purpose of this invention is to provide a long-life sealing material and its preparation method that combines excellent anti-creep relaxation properties, high strength, excellent chemical corrosion resistance and extremely low permeability, and is specifically suitable for harsh electrolytic cell conditions.

[0009] The technical solution of the present invention: A modified polytetrafluoroethylene material for electrolytic cells, wherein the raw materials of the modified polytetrafluoroethylene material for electrolytic cells, by weight, include the following components: 100-120 parts of modified polytetrafluoroethylene resin, 5-15 parts of polyimide resin, 3-8 parts of fluorinated ceramic microspheres, and 0.5-5 parts of fluorinated graphene.

[0010] Furthermore, the modified polytetrafluoroethylene resin is obtained by copolymerization of tetrafluoroethylene, perfluoropropyl vinyl ether, and functionalized fullerene; the mass ratio of tetrafluoroethylene, perfluoropropyl vinyl ether, and functionalized fullerene is (95.0-98.5):(0.1-1.0):(1.0-5.0).

[0011] Furthermore, the glass transition temperature (Tg) of the polyimide resin is ≥250℃.

[0012] Furthermore, the fluorinated ceramic microspheres are at least one of fluorinated alumina microspheres, fluorinated silica microspheres, or boron nitride fluoride microspheres, with a particle size range of 5-50 μm.

[0013] Furthermore, the preparation method of the functionalized fullerene includes the following steps: a) Fullerene oxidation: Fullerene is dispersed in a concentrated acid mixture and oxidized at 60-90℃ for 0.5-4 hours. After treatment, it is separated, washed and dried to obtain surface carboxylated fullerene. b) Acyl chloride reaction: The carboxylated fullerene obtained in step a) is dispersed in a first organic solvent and reacted with thionyl chloride or oxalyl chloride under catalytic conditions to obtain a fullerene intermediate with acyl chloride groups on its surface. c) Functional group grafting: The fullerene intermediate with surface rich in acyl chloride groups obtained in step b) is dispersed in a second organic solvent and reacted with an amine compound or an alcohol compound. After the reaction is complete, the product is separated, washed, and dried to obtain a functionalized fullerene with amino or hydroxyl groups grafted onto its surface. Further, the amine compound is selected from ethylenediamine, hexamethylenediamine, or a silane coupling agent containing a primary amino group; the alcohol compound is selected from ethylene glycol, glycerol, or a silane coupling agent containing a hydroxyl group.

[0014] Furthermore, the first organic solvent is at least one of dichloromethane, 1,2-dichloroethane, tetrahydrofuran, and toluene, and the second organic solvent is at least one of dichloromethane, tetrahydrofuran, and toluene.

[0015] This invention provides a method for preparing modified polytetrafluoroethylene material for electrolytic cells, characterized by comprising the following steps: (1) In a polymerization reactor, deionized water, fluorinated dispersant, functionalized fullerene and part of perfluoropropyl vinyl ether are added and premixed. The mixture is ultrasonically treated for 15-30 min. Then, tetrafluoroethylene and the remaining part of perfluoropropyl vinyl ether are introduced and mixed. Under the action of an initiator, a copolymerization reaction is carried out at 50-80℃ and 1.0-3.0 MPa pressure to obtain the modified polytetrafluoroethylene resin. (2) Weigh each component according to the ratio, and mix the modified polytetrafluoroethylene resin, polyimide resin fluorinated ceramic microspheres and fluorinated graphene in a high-speed mixer according to the ratio to form a uniform composite powder; (3) Press the composite powder from step (2) into a blank, and then sinter the blank in steps under an inert atmosphere. First, heat the material to 320-340℃ and keep it at that temperature, then continue to heat the material to 365-380℃ and keep it at that temperature, and finally cool the material to room temperature to obtain the modified polytetrafluoroethylene material for the electrolytic cell.

[0016] Furthermore, the specific steps of the stepwise sintering described in step (3) are as follows: heat up to 320-340℃ at 20-50℃ / h and hold for 1-4 hours; then heat up to 365-380℃ at 20-40℃ / h and hold for 2-8 hours; then cool down to room temperature at 20-50℃ / h.

[0017] Furthermore, the high-speed mixing in step (2) is carried out in a high-speed mixer for a mixing time of 25-75 minutes and a speed of 1000-3000 rpm.

[0018] Beneficial effects: The modified polytetrafluoroethylene material for electrolytic cells of the present invention has the following beneficial effects: 1. Synergistic Reinforcement System: Using functionalized fullerene copolymerized PTFE as the matrix, steric hindrance and crosslinking points are introduced at the molecular chain level to enhance intrinsic creep resistance; polyimide resin serves as the macroscopic reinforcing framework, providing high strength and high modulus; fluorinated ceramic microspheres improve hardness, wear resistance, and dimensional stability; fluorinated graphene, as a two-dimensional nanosheet, significantly enhances its barrier properties against gases and liquids. Each component has a clearly defined function and exhibits synergistic effects.

[0019] 2. Robust interfacial bonding: Functionalized fullerenes are chemically bonded to the PTFE chain through in-situ copolymerization, solving the problem of nanofiller dispersion and interfacial bonding; fluorinated ceramic microspheres and fluorinated graphene have good compatibility with the fluoroplastic matrix. Although the polyimide resin is physically bonded to the matrix, its high aspect ratio and surface properties can effectively transfer loads in the composite material.

[0020] 3. Excellent comprehensive performance: While maintaining the excellent corrosion resistance of PTFE, the obtained material has significantly improved creep relaxation rate, compression rebound rate, hardness and gas sealing performance, making it particularly suitable for long-term use in high temperature, high pressure and highly corrosive electrolytic cell environments.

[0021] 4. Controllable process: The preparation method, especially the stepwise sintering process, is conducive to eliminating internal stress, promoting the fusion of phases, and ensuring the uniformity and stability of the material structure. Detailed Implementation

[0022] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0023] Polyimide resin was purchased from Shanghai Heruifeng Plastics Co., Ltd., item number: BL-G500; ceramic microspheres were purchased from Shanghai Bihe Industry & Trade Co., Ltd., model G-600; graphene oxide powder was purchased from Jiangxi Shuobang New Material Technology Co., Ltd., particle size 2nm; carbon nanotubes were purchased from Zhongke Leiming (Beijing) Technology Co., Ltd., tube diameter 1-2nm, length 5-30um; polytetrafluoroethylene resin was purchased from Dongguan Hualixing Plastic Raw Materials Co., Ltd., grade: M-18; fullerene C60 was purchased from Hubei Kewode Chemical Co., Ltd., premium grade.

[0024] Unless otherwise specified, all chemical reagents used in this invention are commercially available analytical grade reagents.

[0025] Preparation method of fluorinated ceramic microspheres: S1: Add ceramic microspheres to a 5% (w / w) dilute hydrochloric acid solution, ultrasonically clean for 30 min, then wash repeatedly with deionized water until the pH of the washing solution is 7, place the ceramic microspheres in a vacuum drying oven and dry at 120℃ for 2 h. S2: Dry fluorinated ceramic microspheres, polytetrafluoroethylene resin, and aluminum trichloride were placed in a planetary ball mill jar at a mass ratio of 10:4:0.5. Anhydrous ethanol was added as a dispersion medium, with a solid-liquid mass ratio of 1:6. The ball milling speed was set to 350 r / min, and the milling time was 2.5 h to obtain a uniform ceramic microsphere-PTFE composite slurry. Then, the ceramic microsphere-PTFE composite slurry was placed in a 65℃ constant temperature water bath and stirred until the anhydrous ethanol was completely evaporated. The slurry was then passed through a 120-mesh sieve to obtain the composite powder. S3: Place the composite powder in a tube furnace, heat it to 600℃ under nitrogen protection, hold it at that temperature for 4 hours, and after the reaction is complete, cool it to room temperature under a nitrogen atmosphere. After slight grinding and dispersion, fluorinated ceramic microspheres are obtained.

[0026] Preparation method of fluorinated graphene: Graphene oxide powder was added to deionized water (10 times the mass of the graphene oxide powder in deionized water) and ultrasonically treated at 300W for 60 minutes to fully disperse it, forming a uniform graphene oxide dispersion (concentration of 5 mg / mL). The graphene oxide dispersion was then mixed with ammonium fluoride (the molar ratio of graphene oxide to ammonium fluoride was controlled at 1:20) in a polytetrafluoroethylene autoclave and magnetically stirred for 30 minutes until the ammonium fluoride was completely dissolved. Ammonia was added dropwise to adjust the pH of the system to 8.5, and then the temperature was increased to 180℃ at a rate of 5℃ / min and held for 12 hours. After the reaction was completed, the mixture was cooled, and the product was washed and dried to obtain fluorinated graphene.

[0027] Example 1 The preparation method of functionalized fullerenes includes the following steps: a) Fullerene oxidation: 1g of fullerene C 60 Add 50 mL of a mixture of concentrated H2SO4 (98 wt%) and concentrated HNO3 (68 wt%) (volume ratio 3:1), sonicate at 70 °C for 2 hours, cool and centrifuge, wash with water until neutral to obtain surface carboxylated fullerene. b) Acyl chloride reaction: 0.5 g of surface carboxylated fullerene obtained in step a) was dispersed in 30 mL of dry dichloromethane, 2 mL of oxalyl chloride and 0.5 mL of N,N-dimethylformamide were added as catalysts, and the reaction was refluxed at 50 °C for 4 hours. The solvent and excess oxalyl chloride were removed by rotary evaporation to obtain the acyl chloride intermediate. c) Functional group grafting: The acyl chloride intermediate obtained in step b) was dispersed in 30 mL of anhydrous tetrahydrofuran, and 5 mL of ethylenediamine was slowly added dropwise under ice bath. The reaction was carried out at room temperature for 12 hours. The solid was collected by centrifugation, washed with THF and ethanol, and dried to obtain the functionalized fullerene.

[0028] A method for preparing modified polytetrafluoroethylene material for electrolytic cells includes the following steps: (1) In a 2L high-pressure polymerization reactor, add 1L of deionized water, 3g of perfluorooctanoic acid ammonium, 2g of functionalized fullerene and 0.5g of perfluoropropyl vinyl ether, sonicate for 20min, evacuate and replace with nitrogen, introduce tetrafluoroethylene to a pressure of 1.5MPa, heat to 65℃, add 1.5mL of 5% ammonium persulfate aqueous solution, start the reaction, continuously introduce 97g of tetrafluoroethylene and the remaining 0.5g of perfluoropropyl vinyl ether mixture, maintain pressure of 2.0MPa, stop the reaction after 6 hours, depressurize, discharge and coagulate, wash with hot water, dry at 120℃ to obtain the modified polytetrafluoroethylene resin; (2) Weigh each component according to the ratio, mix 100 parts of modified polytetrafluoroethylene resin, 10 parts of polyimide resin, 8 parts of fluorinated ceramic microspheres and 2 parts of fluorinated graphene in a high-speed mixer, mix at 2000 rpm for 40 minutes to form a uniform composite powder. (3) Press the composite powder from step (2) under 40 MPa pressure for 5 minutes to form a Φ50×5mm blank. Then, under nitrogen protection, the blank is sintered in stages. Under nitrogen protection, the temperature is raised to 330℃ at 30℃ / h and held for 2 hours. Then, the temperature is raised to 370℃ at 30℃ / h and held for 5 hours. Finally, the temperature is lowered to room temperature at 30℃ / h to obtain the modified polytetrafluoroethylene material for the electrolytic cell.

[0029] Example 2 This preparation example is basically the same as Example 1, except that: In the preparation method of functionalized fullerenes, step c, "ethylenediamine" is replaced with "ethylene glycol"; Preparation method of modified polytetrafluoroethylene material for electrolytic cells Replace step (1) "2g functionalized fullerene, 0.5g perfluoropropyl vinyl ether; 97g tetrafluoroethylene and 0.5g perfluoropropyl vinyl ether mixed" with "4g functionalized fullerene, 0.25g perfluoropropyl vinyl ether; 95.5g tetrafluoroethylene and 0.25g perfluoropropyl vinyl ether mixed"; Replace step (2) with “100 parts modified polytetrafluoroethylene resin, 10 parts polyimide resin, 8 parts fluorinated ceramic microspheres and 2 parts fluorinated graphene” and “100 parts modified polytetrafluoroethylene resin, 15 parts polyimide resin, 4.5 parts fluorinated ceramic microspheres and 0.5 parts fluorinated graphene”.

[0030] Example 3 This preparation example is basically the same as Example 1, except that: Preparation method of modified polytetrafluoroethylene material for electrolytic cells Replace step (1) "2g functionalized fullerene, 0.5g perfluoropropyl vinyl ether; 97g tetrafluoroethylene and 0.5g perfluoropropyl vinyl ether mixed" with "1g functionalized fullerene, 0.25g perfluoropropyl vinyl ether; 98.5g tetrafluoroethylene and 0.25g perfluoropropyl vinyl ether mixed"; Replace step (2) with “100 parts modified polytetrafluoroethylene resin, 10 parts polyimide resin, 8 parts fluorinated ceramic microspheres and 2 parts fluorinated graphene” and “100 parts modified polytetrafluoroethylene resin, 15 parts polyimide resin, 4.5 parts fluorinated ceramic microspheres and 0.5 parts fluorinated graphene”.

[0031] Example 4 This preparation example is basically the same as Example 1, except that: In the preparation of the functionalized fullerene, the "2g functionalized fullerene" in step (1) of the preparation method of the modified polytetrafluoroethylene material for the electrolytic cell is replaced with "2g carbon nanotube".

[0032] Example 5 This preparation example is basically the same as Example 1, except that: In the preparation of the functionalized fullerene, the step (1) "2g functionalized fullerene, 0.5g perfluoropropyl vinyl ether; 97g tetrafluoroethylene and 0.5g perfluoropropyl vinyl ether mixed" in the preparation method of modified polytetrafluoroethylene material for electrolytic cell is replaced with "10g functionalized fullerene, 0.5g perfluoropropyl vinyl ether; 89g tetrafluoroethylene and 0.5g perfluoropropyl vinyl ether mixed".

[0033] Comparative Example 1 This preparation example is basically the same as Example 1, except that: In the preparation method of modified polytetrafluoroethylene material for electrolytic cells, modified polytetrafluoroethylene resin is not prepared (i.e., step (1) is removed), and "100 parts of modified polytetrafluoroethylene resin" in step (2) is replaced with "100 parts of polytetrafluoroethylene resin".

[0034] Comparative Example 2 This preparation example is basically the same as Example 1, except that: In the preparation method of modified polytetrafluoroethylene material for electrolytic cells, the "8 parts of fluorinated ceramic microspheres and 2 parts of fluorinated graphene" in step (2) is replaced with "8 parts of ceramic microspheres and 2 parts of graphite powder".

[0035] The following performance tests were performed on the materials obtained in Examples 1-5 and Comparative Examples 1-2: 1. Compression Ratio and Rebound Ratio: According to the "Test Method for Compression Ratio and Rebound Ratio of Gaskets for Pipe Flanges" (GB / T 12622-2008), a gasket compression and rebound testing machine is used. A Φ50mm×3mm sample is placed in the fixture, a preload stress of 1MPa is applied and then zeroed. Then, a load is applied at a rate of 0.5MPa / s to the specified compressive stress (e.g., 25MPa), held for 30s, and the compressed thickness is recorded to calculate the compression ratio. The load is then unloaded to the preload stress, held for 60s, and the recovered thickness is recorded to calculate the rebound ratio. Three samples are tested in parallel, and the arithmetic mean is taken as the final result. The allowable error for the compression ratio is ≤0.5%, and the allowable error for the rebound ratio is ≤1.5%.

[0036] 2. Compression Creep Relaxation Rate: Referring to the "Test Method for Creep Relaxation Rate of Gasket Materials" (GB / T 20671.5-2020), a creep relaxation testing machine is used. The sample is placed in a constant temperature environment (e.g., 100℃), and an initial compressive stress (e.g., 25MPa) is applied. The stress decay of the gasket is continuously monitored using a force sensor. The percentage of residual stress to initial stress after a specified constant temperature time (e.g., 22h) is calculated, which is the creep relaxation rate. Three samples are measured in parallel, and the arithmetic mean is taken as the final result, with an allowable error ≤2%.

[0037] 3. Gas Leakage Rate: According to the "Test Method for Sealing Performance of Gaskets for Pipe Flanges" (GB / T 12385—2025), nitrogen is used as the test medium on the metal-to-metal flange sealing surface. The sample is installed in a standard flange fixture, and a specified bolt load (e.g., 30 MPa gasket stress) is applied. The system pressure is increased to the specified test pressure (e.g., 2 MPa) at room temperature, and after holding the pressure for 10 minutes, the gas leakage volume per unit time is measured using a leak detection fluid or a high-precision flow meter. Three samples are measured in parallel, and the arithmetic mean is taken as the final result, with an allowable error ≤10%.

[0038] 4. Alkali corrosion resistance (mass change rate): Refer to "Determination of the resistance of plastics to liquid chemical reagents" (GB / T11547-2008). Cut samples of the specified size (e.g., 25mm × 25mm × 3mm), dry and weigh them. Completely immerse the samples in a 30% KOH aqueous solution and place them in a 100℃ constant temperature oven for 168 hours. After removal, wash with deionized water, dry, weigh again, and measure the hardness. Calculate the mass change rate and hardness change value before and after immersion. Perform parallel tests on 3 samples, and take the arithmetic mean as the final result. The allowable error for the mass change rate is ≤0.02%.

[0039] Table 1: Performance Test Results

[0040] As shown in Table 1, the modified polytetrafluoroethylene (PTFE) material for electrolytic cells of the present invention exhibits excellent performance in terms of creep resistance, sealing performance, resilience, and corrosion resistance. Specifically, comparing Example 4 with Example 1, it is evident that replacing the functionalized fullerene with carbon nanotubes significantly increases the compression creep relaxation rate and decreases the resilience rate of the material. This demonstrates that the unique zero-dimensional spherical structure of functionalized fullerene has irreplaceable advantages in achieving the three-dimensional molecular chain "pinning" effect and synergistically enhancing the creep resistance and resilience of the matrix with PPVE. Comparing Example 5 with Example 1, it is evident that excessive fullerene affects polymerization or causes dispersion problems, leading to a decline in performance and failure to meet expectations. Results: A comparison of Comparative Example 1 and Example 1 shows that due to the lack of copolymerization synergistic modification of perfluoropropyl vinyl ether and functionalized fullerene, the material's creep resistance is severely insufficient, its resilience is poor, and its gas sealing performance is significantly deteriorated, making it completely unable to meet the long-term sealing requirements of the electrolytic cell. A comparison of Comparative Example 2 and Example 1 shows that after replacing the fluorinated ceramic microspheres and fluorinated graphene with ordinary ceramic microspheres and graphite powder, the material's stability in a strongly alkaline environment is severely reduced, and its gas sealing performance is reduced by more than an order of magnitude. This proves that the use of fluorinated modified special fillers is crucial for ensuring the long-term chemical stability and ultimate sealing of the material in harsh electrolyte environments.

[0041] This invention can also be implemented in various other ways. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A modified polytetrafluoroethylene material for electrolytic cells, characterized in that, The raw materials for the modified polytetrafluoroethylene material used in the electrolytic cell, by weight, include the following components: 100-120 parts of modified polytetrafluoroethylene resin, 5-15 parts of polyimide resin, 3-8 parts of fluorinated ceramic microspheres, and 0.5-5 parts of fluorinated graphene.

2. The modified polytetrafluoroethylene material for electrolytic cells according to claim 1, characterized in that, The modified polytetrafluoroethylene resin is obtained by copolymerization of tetrafluoroethylene, perfluoropropyl vinyl ether, and functionalized fullerene; the mass ratio of tetrafluoroethylene, perfluoropropyl vinyl ether, and functionalized fullerene is (95.0-98.5):(0.1-1.0):(1.0-5.0).

3. The modified polytetrafluoroethylene material for electrolytic cells according to claim 1, characterized in that, The glass transition temperature (Tg) of the polyimide resin is ≥250℃.

4. The modified polytetrafluoroethylene material for electrolytic cells according to claim 1, characterized in that, The fluorinated ceramic microspheres are at least one of fluorinated alumina microspheres, fluorinated silica microspheres, or boron nitride fluoride microspheres, with a particle size range of 5-50 μm.

5. The modified polytetrafluoroethylene material for electrolytic cells according to claim 2, characterized in that, The method for preparing the functionalized fullerene includes the following steps: a) Fullerene oxidation: Fullerene is dispersed in a concentrated acid mixture and oxidized at 60-90℃ for 0.5-4 hours. After treatment, it is separated, washed and dried to obtain surface carboxylated fullerene. b) Acyl chloride reaction: The carboxylated fullerene obtained in step a) is dispersed in a first organic solvent and reacted with thionyl chloride or oxalyl chloride under catalytic conditions to obtain a fullerene intermediate with acyl chloride groups on its surface. c) Functional group grafting: The fullerene intermediate with surface rich in acyl chloride groups obtained in step b) is dispersed in a second organic solvent and reacted with amine or alcohol compounds. After the reaction is completed, the product is separated, washed and dried to obtain functionalized fullerenes with amino or hydroxyl groups grafted on the surface.

6. The modified polytetrafluoroethylene material for electrolytic cells according to claim 5, characterized in that, The amine compound is selected from ethylenediamine, hexamethylenediamine, or a silane coupling agent containing a primary amino group; the alcohol compound is selected from ethylene glycol, glycerol, or a silane coupling agent containing a hydroxyl group.

7. The modified polytetrafluoroethylene material for electrolytic cells according to claim 5, characterized in that, The first organic solvent is at least one of dichloromethane, 1,2-dichloroethane, tetrahydrofuran, and toluene, and the second organic solvent is at least one of dichloromethane, tetrahydrofuran, and toluene.

8. The method for preparing the modified polytetrafluoroethylene material for electrolytic cells according to any one of claims 1-7, characterized in that, Includes the following steps: (1) In a polymerization reactor, deionized water, fluorinated dispersant, functionalized fullerene and part of perfluoropropyl vinyl ether are added and premixed. The mixture is ultrasonically treated for 15-30 min. Then, tetrafluoroethylene and the remaining part of perfluoropropyl vinyl ether are introduced and mixed. Under the action of an initiator, a copolymerization reaction is carried out at 50-80℃ and 1.0-3.0 MPa pressure to obtain the modified polytetrafluoroethylene resin. (2) Weigh each component according to the ratio, and mix the modified polytetrafluoroethylene resin, polyimide resin, fluorinated ceramic microspheres and fluorinated graphene in a high-speed mixer according to the ratio to form a uniform composite powder; (3) Press the composite powder from step (2) into a blank, and then sinter the blank in steps under an inert atmosphere. First, heat the material to 320-340℃ and keep it at that temperature, then continue to heat the material to 365-380℃ and keep it at that temperature, and finally cool the material to room temperature to obtain the modified polytetrafluoroethylene material for the electrolytic cell.

9. The method for preparing the modified polytetrafluoroethylene material for electrolytic cells according to claim 8, characterized in that, The specific steps of the stepwise sintering in step (3) are as follows: heat up to 320-340℃ at 20-50℃ / h and hold for 1-4 hours; then heat up to 365-380℃ at 20-40℃ / h and hold for 2-8 hours; then cool down to room temperature at 20-50℃ / h.

10. The method for preparing the modified polytetrafluoroethylene material for electrolytic cells according to claim 8, characterized in that, The high-speed mixing in step (2) is carried out in a high-speed mixer for 25-75 minutes and at a speed of 1000-3000 rpm.

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