A high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm and its preparation method

Abstract

This invention belongs to the technical field of membrane materials for alkaline water electrolysis hydrogen production, specifically relating to a high-toughness, oxidation-resistant alkaline water electrolyzer membrane and its preparation method. The method involves mixing anhydrous methylpyrrolidone, anhydrous dimethylacetamide, anhydrous lithium chloride, polybenzimidazole resin, polyethersulfone resin, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylpyrrolidone, polyethylene glycol, and glycerol, and adding zirconium ceroxyphosphonate polybenzimidazole and sulfonylphosphonate benzimidazole fluoride copolymer. The membrane is then prepared through coating, pre-evaporation, aqueous phase inversion, washing, potassium hydroxide activation, and drying. The membrane obtained by this invention exhibits good flexibility, oxidation resistance, hydrophilicity retention, and suitability for alkaline water electrolysis.

Description

Technical Field

[0001] This invention belongs to the technical field of alkaline water electrolysis hydrogen production membrane materials, specifically relating to a high-toughness, oxidation-resistant alkaline water electrolyzer membrane and its preparation method. Background Technology

[0002] Alkaline water electrolysis is a crucial technological pathway for producing green hydrogen. The diaphragm, a key component of the electrolyzer, primarily isolates hydrogen generated at the cathode from oxygen generated at the anode, while allowing ion migration in the electrolyte to maintain the continuous electrolysis reaction. The diaphragm material must operate under complex conditions of strong alkali, high temperature, bubble erosion, and electric field influence. It must possess not only low ion transport resistance but also high gas barrier properties, dimensional stability, alkali resistance, and mechanical strength. Unstable pore structure, insufficient hydrophilicity, or poor oxidation resistance of the diaphragm can easily lead to increased electrolysis voltage, increased gas cross-permeability, localized dry spots, and shortened service life, ultimately affecting the safety and hydrogen production efficiency of the alkaline water electrolyzer.

[0003] Existing alkaline water electrolyzer diaphragms are typically prepared by combining organic polymers with inorganic hydrophilic fillers. For example, polysulfone resins, polyethersulfone resins, and polyphenylene sulfide fiber cloth are used as film-forming or support materials, and inorganic oxides are introduced to improve hydrophilicity and electrolyte retention. However, traditional composite diaphragms still have several shortcomings: the interfacial bonding between inorganic fillers and organic resins is limited, and filler migration or pore deterioration easily occurs under long-term alkaline immersion and bubble scouring; some diaphragms sacrifice flexibility and tensile strength while improving hydrophilicity, making them prone to microcracks during assembly, compression, or cycle start-up and shutdown; simultaneously, the anodic oxidation environment may promote polymer chain aging, leading to increased diaphragm resistance and decreased gas tightness. Especially under high-load, frequent fluctuation operating conditions, it is difficult to simultaneously achieve high toughness, oxidation resistance, low resistance, and stable gas barrier properties by relying solely on conventional polymer matrices or ordinary inorganic fillers.

[0004] Therefore, there is an urgent need to develop an alkaline water electrolyzer diaphragm that is primarily composed of organic materials and possesses flexible support, hydrophilic retention, interfacial stability, and oxidation resistance. This method involves constructing a continuous film-forming phase using alkali-resistant polymer resin, providing mechanical support with woven polyphenylene sulfide fiber fabric, and introducing a composite modification component with antioxidant and ionic solvation properties (polybenzimidazole, zirconium phosphonate, and cerium oxide clusters), as well as a graft modification component with flexible interfacial toughening properties (sulfopropylbenzimidazole, aminoethylphosphonic acid, and polyvinylidene fluoride / hexafluoropropylene copolymer). This is expected to form a stable organic-inorganic synergistic network within the diaphragm, improving electrolyte wetting and retention capabilities, mitigating oxidative damage, enhancing the interfacial bonding between the filler and the polymer, and improving the long-term service stability of the diaphragm in an alkaline water electrolysis environment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-toughness, oxidation-resistant, alkaline water electrolyzer diaphragm and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm, comprising the following steps: S1. By weight, mix 160.0-220.0 parts of anhydrous N-methylpyrrolidone and 30.0-60.0 parts of anhydrous N,N-dimethylacetamide to obtain a mixed solvent; add 1.0-3.0 parts of dried anhydrous lithium chloride, 8.0-16.0 parts of polybenzimidazole resin and 35.0-50.0 parts of polyethersulfone resin to the mixed solvent, stir at 100-120℃, and cool to 7℃. At 5-85℃, add 6.0-12.0 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 5.0-10.0 parts of polyvinylpyrrolidone, 3.0-6.0 parts of polyethylene glycol-400 and 2.0-5.0 parts of glycerol, continue stirring, add 3.0-7.0 parts of zirconium cerium oxyphosphonate polybenzimidazole and 4.0-9.0 parts of sulfopropylphosphonate benzimazole fluoride copolymer, shear dispersion, degassing, to obtain membrane film-forming slurry; S2. Wash and dry 18.0-30.0 parts of polyphenylene sulfide fiber woven fabric to obtain pretreated polyphenylene sulfide fiber support fabric; coat the surface of the pretreated polyphenylene sulfide fiber support fabric with membrane forming slurry to obtain coated polyphenylene sulfide fiber support fabric; pre-evaporate the coated polyphenylene sulfide fiber support fabric at 25-35℃, then immerse it in deionized water at 20-30℃, and then wash it in deionized water at 40-50℃; immerse the washed membrane in potassium hydroxide aqueous solution, activate it at 50-60℃, and dry it at 45-55℃ to obtain a high-toughness oxidation-resistant alkaline water electrolyzer membrane.

[0007] In this invention, the preparation mechanism of the high-toughness, oxidation-resistant, and alkaline-resistant water electrolyzer diaphragm is as follows: after anhydrous N-methylpyrrolidone and anhydrous N,N-dimethylacetamide form a mixed solvent, anhydrous lithium chloride helps dissolve and disperse polybenzimidazole resin and polyethersulfone resin. Polybenzimidazole resin provides an alkali-resistant, heat-resistant, and ion-solvent-resistant structure, while polyethersulfone resin forms a continuous film-forming phase and improves the film strength. The addition of polyvinylidene fluoride-hexafluoropropylene copolymer improves the film toughness with its flexible fluoropolymer segments. Polyvinylpyrrolidone, polyethylene glycol-400, and glycerol jointly regulate the slurry viscosity, hydrophilicity, and phase inversion pore structure. After the addition of zirconium cerium oxyphosphonate polybenzimidazole, its polybenzimidazole structure is compatible with polybenzimidazole resin, and zirconium phosphonate and cerium oxyphosphonate clusters provide hydrophilic, antioxidant and alkaline adsorption sites. After the addition of sulfopropylphosphonate benzimidazole fluoride copolymer, its polyvinylidene fluoride-hexafluoropropylene copolymer segments are compatible with polyvinylidene fluoride-hexafluoropropylene copolymer in the matrix, the benzimidazole structure interacts with polybenzimidazole resin, and the aminoethylphosphonic acid and sulfopropyl groups interact with hydrophilic inorganic clusters and alkaline electrolyte, so that a stable interfacial network is formed between the organic phase, inorganic clusters and supporting structure. After the membrane-forming slurry is coated onto the surface of the polyphenylene sulfide (PPS) fiber woven fabric, the PPS fiber woven fabric provides tensile support and dimensional stability. Pre-evaporation allows for moderate evaporation of the surface solvent and improves the initial stability of the coating. Subsequently, upon immersion in deionized water, anhydrous N-methylpyrrolidone and anhydrous N,N-dimethylacetamide diffuse into the aqueous phase, and deionized water enters the interior of the coating. The polymer undergoes non-solvent-induced phase separation and solidifies into a porous membrane layer. Residual solvents and soluble components are then removed by washing with deionized water. During activation with potassium hydroxide aqueous solution, the nitrogen-containing sites, zirconium phosphonate sites, and sulfopropyl hydrophilic sites in the polybenzimidazole resin, zirconium phosphonate polybenzimidazole, and benzimidazole sulfonate fluoride copolymer adsorb and retain the alkaline electrolyte. After drying, a high-toughness, oxidation-resistant alkaline water electrolyzer membrane with supporting strength, flexibility, oxidation resistance, and ion conductivity is formed.

[0008] According to a preferred embodiment of the present invention, in step S1, the polybenzimidazole resin is Celazole U-60 grade polybenzimidazole resin; the shear dispersion temperature is 50-60℃.

[0009] According to a preferred embodiment of the present invention, in step S2, the activation time at 50-60°C is 4-8 hours.

[0010] According to a preferred embodiment of the present invention, the preparation method of the zirconium ceroxyphosphonate polybenzimidazole includes: A1. By weight, under nitrogen protection, 9.9-10.1 parts of 3,3′-diaminobenzidine free base, 7.4-7.8 parts of isophthalic acid, 90.0-120.0 parts of polyphosphoric acid and 5.0-10.0 parts of phosphorus pentoxide are mixed and stirred at 110-120℃. The mixture is then heated to 150-160℃ and further heated to 200-220℃. After cooling to 80-90℃, 500.0-800.0 parts of deionized water are added. The mixture is then centrifuged, washed, and dried to obtain the polybenzimidazole precursor. A2. Add 10.0-15.0 parts of polybenzimidazole precursor to a mixed solvent of 120.0-160.0 parts of anhydrous N,N-dimethylacetamide and 3.0-5.0 parts of anhydrous lithium chloride, stir at 70-80℃, cool to 45-55℃, add 2.0-3.0 parts of phenylphosphonic acid, 4.0-6.0 parts of zirconium oxychloride octahydrate and 4.0-6.0 parts of triethylamine, and continue the reaction; then add 2.0-4.0 parts of cerium(III) nitrate hexahydrate, 0.5-1.0 parts of citric acid, 6.0-10.0 parts of urea and 40.0-60.0 parts of deionized water, react at 80-90℃, then transfer to a reaction vessel, solvothermal treat at 135-150℃, cool, centrifuge, wash, dry, grind and sieve.

[0011] In this invention, the preparation mechanism of zirconium cerium oxyphosphonate polybenzimidazole is as follows: Under nitrogen protection, the free base of 3,3′-diaminobenzidine reacts with isophthalic acid in a strongly dehydrating system composed of polyphosphoric acid and phosphorus pentoxide to undergo a condensation reaction. The two adjacent amino groups in the free base of 3,3′-diaminobenzidine first condense with the carboxyl groups in isophthalic acid, followed by further cyclization and dehydration to form a benzimidazole ring, which grows along the aromatic chain segment to obtain the polybenzimidazole precursor. This process requires anhydrous, acidic, and relatively high temperature conditions. Polyphosphoric acid serves as both a reaction medium and promotes carboxyl group activation and dehydration cyclization, while phosphorus pentoxide further enhances the dehydration capacity, which is beneficial to the growth of the polybenzimidazole precursor molecular chain. Adding the polybenzimidazole precursor to a mixed solvent of anhydrous N,N-dimethylacetamide and anhydrous lithium chloride weakens the strong interactions between the polybenzimidazole precursor molecular chains, improving its dispersion and swelling degree. Subsequently, phenylphosphonic acid, zirconium oxychloride octahydrate, and triethylamine were added. The phosphonic acid group in phenylphosphonic acid coordinates with zirconium species. The zirconium oxychloride octahydrate forms zirconium-oxygen coordination centers through coordination and partial hydrolysis. Triethylamine regulates the acidity of the system and promotes the binding of phosphonic acid groups with zirconium species. The benzimidazole nitrogen sites in the polybenzimidazole precursor can coordinate with zirconium species or form hydrogen bonds, allowing the zirconium phosphonate structure to attach around the polybenzimidazole precursor. Cerium(III) nitrate hexahydrate, citric acid, urea, and deionized water were then added. Citric acid plays a complexing and dispersing role for cerium species. Urea gradually hydrolyzes during heating and solvothermal treatment, slowly increasing the alkalinity of the system and promoting the hydrolysis of cerium species to generate cerium-oxygen clusters. Cerium-oxygen clusters form near the interface of zirconium phosphonate and polybenzimidazole precursor, combining the three into a composite structure to obtain cerium-oxygen zirconium phosphonate polybenzimidazole. The polybenzimidazole precursor provides an alkali-resistant framework and ion solvation sites, zirconium phosphonate improves hydrophilicity and interfacial anchoring ability, and the cerium-oxygen clusters buffer oxidizing species through valence state changes of cerium species.

[0012] According to a preferred embodiment of the present invention, in step A1, the stirring time at 110-120°C is 1-2 hours; the reaction time at 150-160°C is 3-4 hours; and the reaction time at 200-220°C is 10-16 hours.

[0013] According to a preferred embodiment of the present invention, in step A2, the stirring time at 70-80°C is 6-8 hours; the reaction time at 80-90°C is 5-7 hours; and the solvothermal treatment time at 135-150°C is 6-10 hours.

[0014] According to a preferred embodiment of the present invention, the method for preparing the sulfopropylphosphonic acid benzimidazole fluorinated copolymer includes: B1. By weight, 20.0-30.0 parts of polyvinylidene fluoride-hexafluoropropylene copolymer are added to 180.0-240.0 parts of anhydrous N-methylpyrrolidone and 30.0-60.0 parts of anhydrous dimethyl sulfoxide. The mixture is stirred at 65-75°C, cooled to 45-50°C, and a mixture containing 1.0-3.0 parts of potassium hydroxide, 1.0-3.0 parts of deionized water and 0.2-0.6 parts of tetrabutylammonium bromide is added. The mixture is reacted at 45-50°C to obtain an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution. B2. Premix 1.5-3.0 parts of 2-aminoethylphosphonic acid, 3.0-5.0 parts of triethylamine, and 10.0-20.0 parts of anhydrous dimethyl sulfoxide to obtain an organic dispersion of 2-aminoethylphosphonic acid; add 2.0-3.5 parts of the organic dispersion of 2-aminobenzimidazole and 2-aminoethylphosphonic acid to an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution, and react at 60-70℃ to obtain a reaction solution; add the reaction solution to a mixture of 800.0-1200.0 parts of ethanol and deionized water. The intermediate was obtained by centrifugation, washing, and drying to obtain benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene. The benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate was added to 80.0-120.0 parts of anhydrous N,N-dimethylacetamide and 20.0-40.0 parts of anhydrous dimethyl sulfoxide, dispersed, and then 0.8-1.5 parts of sodium 3-bromopropanesulfonate and 0.8-1.5 parts of potassium carbonate were added. The reaction was carried out at 75-90℃, followed by centrifugation, washing, and drying.

[0015] In this invention, the preparation mechanism of the sulfonylphosphonic acid benzimidazole fluoride copolymer is as follows: The polyvinylidene fluoride-hexafluoropropylene copolymer is first swollen and dispersed in anhydrous N-methylpyrrolidone and anhydrous dimethyl sulfoxide to form a homogeneous polymer solution. Subsequently, a mixture prepared from potassium hydroxide, deionized water, and tetrabutylammonium bromide is added. Tetrabutylammonium bromide promotes the entry of the alkaline component into the organic phase, while potassium hydroxide causes the polyvinylidene fluoride-hexafluoropropylene copolymer segments to defluorinate, forming an unsaturated structure on the polymer chain, resulting in an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution. This unsaturated structure provides reaction sites for subsequent grafting. When 2-aminoethylphosphonic acid, triethylamine, and anhydrous dimethyl sulfoxide are premixed, triethylamine weakens the acidic effect of the phosphonic acid group in 2-aminoethylphosphonic acid, allowing its amino group to maintain good nucleophilicity. An organic dispersion of 2-aminobenzimidazole and 2-aminoethylphosphonic acid was added to an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution. The nitrogen-containing sites in 2-aminobenzimidazole and the unsaturated structures on the amino groups of 2-aminoethylphosphonic acid undergo addition grafting to form a benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate. The intermediate was then dispersed in anhydrous N,N-dimethylacetamide and anhydrous dimethyl sulfoxide, and 3-bromopropanesulfonate and potassium carbonate were added. Under the action of potassium carbonate, the reactive nitrogen sites in the benzimidazole structure underwent a substitution reaction with the 3-bromopropanesulfonate, introducing a sulfopropyl group to obtain a sulfopropylphosphonic acid benzimidazole fluoride copolymer. The polyvinylidene fluoride-hexafluoropropylene copolymer segment provides flexibility and chemical resistance, the benzimidazole structure enhances compatibility with polybenzimidazole resins and polybenzimidazole precursors, the aminoethylphosphonic acid structure can form coordination or hydrogen bonds with zirconium species and cerium oxygen clusters, and the sulfopropyl structure improves hydrophilicity and alkali retention.

[0016] According to a preferred embodiment of the present invention, in step B1, the stirring time at 65-75°C is 4-6 hours; the reaction time at 45-50°C is 1.5-2.5 hours.

[0017] According to a preferred embodiment of the present invention, in step B2, the reaction time at 60-70°C is 8-10 hours.

[0018] In a second aspect, the present invention provides a high-toughness, oxidation-resistant, and alkaline-resistant water electrolyzer diaphragm prepared according to the preparation method of the high-toughness, oxidation-resistant, and alkaline-resistant water electrolyzer diaphragm described above.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses polybenzimidazole resin, polyethersulfone resin and polyvinylidene fluoride-hexafluoropropylene copolymer to form a film-forming system. Polybenzimidazole resin is beneficial to improving the stability and ion solubilization ability of the diaphragm in an alkaline environment. Polyethersulfone resin is beneficial to improving the continuity of the film layer, film strength and heat resistance. Polyvinylidene fluoride-hexafluoropropylene copolymer is beneficial to improving the flexibility and bending resistance of the film layer. Polyphenylene sulfide fiber woven fabric serves as a supporting skeleton, which can improve the tensile strength, dimensional stability and assembly tolerance of the diaphragm, making the diaphragm less prone to cracking, warping and structural collapse under alkaline water electrolysis tank pressing, soaking and bubble flushing conditions.

[0020] (2) This invention uses zirconium cerium oxyphosphonate polybenzimidazole, which forms a good compatibility and dispersion with polybenzimidazole resin and polyethersulfone resin, and provides stable hydrophilic retention sites and antioxidant protection sites inside the membrane. Zirconium cerium oxyphosphonate polybenzimidazole can improve the wetting and retention ability of the membrane to potassium hydroxide aqueous solution, reduce the risk of hydrophilicity decay, pore deterioration and resistance increase of the membrane during long-term operation, and at the same time help to alleviate the damage of oxidizing species to polybenzimidazole resin, polyethersulfone resin and polyvinylidene fluoride-hexafluoropropylene copolymer.

[0021] (3) The present invention uses a sulfopropylphosphonic acid benzimidazole fluoride copolymer to form a flexible interface bridge between it and polyvinylidene fluoride-hexafluoropropylene copolymer, polybenzimidazole resin, and zirconium cerium oxyphosphonate polybenzimidazole. The sulfopropylphosphonic acid benzimidazole fluoride copolymer can improve the bonding stability between organic resins and between organic resins and modified compounds, reduce the migration of modified compounds and interface debonding, so that the resulting high-toughness oxidation-resistant alkaline water electrolyzer diaphragm has the advantages of low mass transfer resistance, good gas barrier properties, strong oxidation resistance, and good long-term service stability. Detailed Implementation

[0022] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0023] Example 1 This embodiment provides a method for preparing a high-toughness, oxidation-resistant, alkaline water electrolyzer diaphragm, the steps of which include: S1. Mix 190.0g of anhydrous N-methylpyrrolidone and 45.0g of anhydrous N,N-dimethylacetamide and stir for 15min to obtain a mixed solvent. Add 2.0g of anhydrous lithium chloride, 12.0g of Celazole U-60 grade polybenzimidazole resin and 42.5g of polyethersulfone resin to the mixed solvent after vacuum drying at 80℃ for 8h. Stir at 110℃ for 7h to form a uniform resin solution. Cool to 80℃ and add 9.0g of polyvinylidene fluoride-hexafluoropropylene copolymer, 7.5g of polyvinylpyrrolidone, 4.5g of polyethylene glycol-400 and 3.5g of glycerol. Continue stirring for 5h. Add 5.0g of zirconium cerium oxyphosphonate polybenzimidazole and 6.5g of sulfonylphosphonate benzimidazole fluoride copolymer. Shear disperse at 55℃ for 45min, and then degas at -0.08MPa for 20min to obtain a membrane forming slurry.

[0024] S2. Cut 24.0g of polyphenylene sulfide (PPS) fiber woven fabric into flat sheets, wash with ethanol and then with deionized water, and dry at 60℃ for 2h to obtain pretreated PPS fiber support fabric; uniformly coat the surface of the pretreated PPS fiber support fabric with diaphragm film-forming slurry, so that the film-forming slurry fully wets the PPS fiber woven fabric and forms a continuous coating, with a single-sided wet coating thickness of 180μm, to obtain coated PPS fiber support fabric; pre-evaporate the coated PPS fiber support fabric at 30℃ for 60s, then immerse it in 25℃ deionized water for phase inversion film formation for 20min, and then immerse it in 45℃ deionized water for washing for 8h; immerse the washed diaphragm in a 15% potassium hydroxide aqueous solution and activate it at 55℃ for 6h, remove it and remove the free potassium hydroxide aqueous solution from the surface, and dry it at 50℃ until there are no free droplets on the surface to obtain a high-toughness oxidation-resistant alkaline water electrolyzer diaphragm.

[0025] Preparation of zirconium ceroxyphosphonate polybenzimidazole: A1. Under nitrogen protection, 10.0g 3,3′-Diaminobenzidine free base, 7.6 g isophthalic acid, 105.0 g polyphosphoric acid, and 7.5 g phosphorus pentoxide were added to a reactor equipped with mechanical stirring, a nitrogen inlet, and a condenser. After purging with nitrogen for 30 min, nitrogen protection was maintained, and stirring was started to ensure uniform mixing of the materials. The mixture was stirred at 115 °C for 1.5 h, then heated to 155 °C for 3.5 h, and further heated to 210 °C for 13 h to obtain a viscous reactant. After the reaction was completed, the mixture was cooled to 85 °C, and the viscous reactant was slowly added to 650.0 g deionized water over 30 min while stirring to allow the polymer to fully precipitate. After standing for 30 min, the mixture was centrifuged at 5000 r / min for 10 min, and the solid was collected. The solid was washed with deionized water until the pH of the washing solution reached 7.0, then washed once with ethanol, and subsequently vacuum dried at 70 °C for 12 h to obtain the polybenzimidazole precursor.

[0026] A2. 12.5 g of polybenzimidazole precursor was added to a mixed solvent consisting of 140.0 g of anhydrous N,N-dimethylacetamide and 4.0 g of anhydrous lithium chloride. The mixture was stirred at 75 °C for 7 h to allow the polybenzimidazole precursor to fully swell and disperse. The temperature was then lowered to 50 °C, and 2.5 g of phenylphosphonic acid, 5.0 g of zirconium oxychloride octahydrate, and 5.0 g of triethylamine were added. The reaction was continued for 5 h. Subsequently, 3.0 g of cerium(III) nitrate hexahydrate and 0.75 g of triethylamine were added. 8.0 g of citric acid, 8.0 g of urea, and 50.0 g of deionized water were reacted at 85 °C for 6 h, then transferred to a reaction vessel and solvothermal treated at 142.5 °C for 8 h. After cooling to 25 °C, the mixture was centrifuged at 6000 r / min for 10 min. The resulting solid was washed successively with deionized water and ethanol until the washing liquid had no obvious color. It was then vacuum dried at 65 °C for 12 h, ground, and passed through a 300-mesh sieve to obtain zirconium ceroxyphosphonate polybenzimidazole.

[0027] Preparation of sulfopropylphosphonic acid benzimidazole fluorinated copolymer: B1. Add 25.0g of polyvinylidene fluoride-hexafluoropropylene copolymer to 210.0g of anhydrous N-methylpyrrolidone and 45.0g of anhydrous dimethyl sulfoxide, and stir at 70℃ for 5h to allow the polyvinylidene fluoride-hexafluoropropylene copolymer to fully swell and disperse. Cool to 47.5℃. Separately, add 1.5g of potassium hydroxide to 2.0g of deionized water and stir until completely dissolved. Then add 0.4g of tetrabutylammonium bromide and stir for 10min to obtain a mixture. Add the mixture dropwise to the polyvinylidene fluoride-hexafluoropropylene copolymer dispersion system over a period of 10min. React at 47.5℃ for 2h to obtain an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0028] B2. 2.25 g of 2-aminoethylphosphonic acid, 4.0 g of triethylamine, and 15.0 g of anhydrous dimethyl sulfoxide were premixed for 30 min to obtain an organic dispersion of 2-aminoethylphosphonic acid. 2.75 g of the organic dispersion of 2-aminobenzimidazole and 2-aminoethylphosphonic acid was added to the activated polyvinylidene fluoride-hexafluoropropylene copolymer solution, and the mixture was reacted at 65 °C for 9 h to obtain a reaction solution. The reaction solution was added to a mixture of 500.0 g of ethanol and 500.0 g of deionized water while stirring for 20 min. The precipitate was collected by centrifugation at 5000 r / min for 10 min. The precipitate was washed three times with a mixture of ethanol and deionized water, and then washed twice with deionized water. The precipitate was then vacuum dried at 60 °C for 12 h to obtain benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene copolymer. Intermediate: The obtained benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate was added to 100.0 g of anhydrous N,N-dimethylacetamide and 30.0 g of anhydrous dimethyl sulfoxide and dispersed for 1 h. Then, 1.15 g of sodium 3-bromopropane sulfonate and 1.15 g of potassium carbonate were added, and the mixture was reacted at 82.5 °C for 8 h. After cooling, the mixture was centrifuged at 5000 r / min for 10 min. The resulting solid was washed with ethanol and deionized water until the pH of the washing solution reached 7.0. The solid was then vacuum dried at 60 °C for 12 h to obtain the sulfopropylphosphonic acid benzimidazole fluoride copolymer.

[0029] Example 2 The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a high-toughness, oxidation-resistant, alkaline water electrolyzer diaphragm, the steps of which include: S1. Mix 160.0g of anhydrous N-methylpyrrolidone and 30.0g of anhydrous N,N-dimethylacetamide to obtain a mixed solvent; add 1.0g of dried anhydrous lithium chloride, 8.0g of polybenzimidazole resin and 35.0g of polyethersulfone resin to the mixed solvent, stir at 100℃, cool to 75℃, add 6.0g of polyvinylidene fluoride-hexafluoropropylene copolymer, 5.0g of polyvinylpyrrolidone, 3.0g of polyethylene glycol-400 and 2.0g of glycerol, continue stirring, add 3.0g of zirconium cerium oxyphosphonate polybenzimidazole and 4.0g of sulfopropylphosphonate benzimidazole fluoride copolymer, shear dispersion at 50℃, degas, to obtain a membrane forming slurry.

[0030] S2. 18.0g of polyphenylene sulfide fiber woven fabric is washed and dried to obtain pretreated polyphenylene sulfide fiber support fabric; the membrane forming slurry is uniformly coated on the surface of the pretreated polyphenylene sulfide fiber support fabric, so that the membrane forming slurry fully wets the polyphenylene sulfide fiber woven fabric and forms a continuous coating to obtain a coated polyphenylene sulfide fiber support fabric; the coated polyphenylene sulfide fiber support fabric is pre-evaporated at 25℃, then immersed in 20℃ deionized water for phase inversion to form a membrane, and then immersed in 40℃ deionized water for washing; the washed membrane is immersed in potassium hydroxide aqueous solution, activated at 50℃ for 4h, and dried at 45℃ to obtain a high-toughness oxidation-resistant alkaline water electrolyzer membrane.

[0031] Preparation of zirconium ceroxyphosphonate polybenzimidazole: A1. Under nitrogen protection, 9.9 g of 3,3′-diaminobenzidine free base, 7.4 g of isophthalic acid, 90.0 g of polyphosphoric acid and 5.0 g of phosphorus pentoxide were added to the reactor. The stirring was turned on to mix the materials evenly. The mixture was stirred at 110°C for 1 h, heated to 150°C for 3 h, and then heated to 200°C for 10 h. After the reaction was completed, the mixture was cooled to 80°C. The reactants were added to 500.0 g of deionized water to precipitate the polymer. The precipitate was centrifuged, washed and dried to obtain the polybenzimidazole precursor.

[0032] A2. 10.0 g of polybenzimidazole precursor was added to a mixed solvent consisting of 120.0 g of anhydrous N,N-dimethylacetamide and 3.0 g of anhydrous lithium chloride. The mixture was stirred at 70 °C for 6 h, cooled to 45 °C, and 2.0 g of phenylphosphonic acid, 4.0 g of zirconium oxychloride octahydrate and 4.0 g of triethylamine were added. The reaction was continued, followed by the addition of 2.0 g of cerium(III) nitrate hexahydrate, 0.5 g of citric acid, 6.0 g of urea and 40.0 g of deionized water. The mixture was reacted at 80 °C for 5 h, then transferred to a reaction vessel and solvated at 135 °C for 6 h. After cooling, the product was centrifuged, washed, dried, ground and sieved to obtain zirconium cerium oxyphosphonate polybenzimidazole.

[0033] Preparation of sulfopropylphosphonic acid benzimidazole fluorinated copolymer: B1. Add 20.0g of polyvinylidene fluoride-hexafluoropropylene copolymer to 180.0g of anhydrous N-methylpyrrolidone and 30.0g of anhydrous dimethyl sulfoxide, stir at 65℃ for 4h, cool to 45℃, dissolve 1.0g of potassium hydroxide in 1.0g of deionized water, and then add 0.2g of tetrabutylammonium bromide to obtain a mixture. Add this mixture to the above system and react at 45℃ for 1.5h to obtain an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0034] B2. 1.5 g of 2-aminoethylphosphonic acid, 3.0 g of triethylamine, and 10.0 g of anhydrous dimethyl sulfoxide were premixed to obtain an organic dispersion of 2-aminoethylphosphonic acid. 2.0 g of the organic dispersion of 2-aminobenzimidazole and 2-aminoethylphosphonic acid was added to the activated polyvinylidene fluoride-hexafluoropropylene copolymer solution, and the mixture was reacted at 60 °C for 8 h to obtain a reaction solution. The reaction solution was added to a mixture of 400.0 g of ethanol and 400.0 g of deionized water, centrifuged, washed, and dried to obtain a benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate. The obtained benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate was added to 80.0 g of anhydrous N,N-dimethylacetamide and 20.0 g of anhydrous dimethyl sulfoxide, dispersed, and then 0.8 g of... Sodium 3-bromopropane sulfonate and 0.8 g potassium carbonate were reacted at 75 °C, centrifuged, washed, and dried to obtain sulfopropionic acid benzimidazole fluoride copolymer.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a high-toughness, oxidation-resistant, alkaline water electrolyzer diaphragm, the steps of which include: S1. Mix 220.0g of anhydrous N-methylpyrrolidone and 60.0g of anhydrous N,N-dimethylacetamide to obtain a mixed solvent; add 3.0g of dried anhydrous lithium chloride, 16.0g of polybenzimidazole resin and 50.0g of polyethersulfone resin to the mixed solvent, stir at 120℃, cool to 85℃, add 12.0g of polyvinylidene fluoride-hexafluoropropylene copolymer, 10.0g of polyvinylpyrrolidone, 6.0g of polyethylene glycol-400 and 5.0g of glycerol, continue stirring, add 7.0g of zirconium cerium oxyphosphonate polybenzimidazole and 9.0g of sulfopropylphosphonate benzimidazole fluoride copolymer, shear dispersion at 60℃, degas, to obtain a membrane forming slurry.

[0036] S2. 30.0g of polyphenylene sulfide fiber woven fabric is washed and dried to obtain pretreated polyphenylene sulfide fiber support fabric; the membrane forming slurry is uniformly coated on the surface of the pretreated polyphenylene sulfide fiber support fabric, so that the membrane forming slurry fully wets the polyphenylene sulfide fiber woven fabric and forms a continuous coating to obtain a coated polyphenylene sulfide fiber support fabric; the coated polyphenylene sulfide fiber support fabric is pre-evaporated at 35℃, then immersed in 30℃ deionized water for phase inversion to form a membrane, and then immersed in 50℃ deionized water for washing; the washed membrane is immersed in potassium hydroxide aqueous solution, activated at 60℃ for 8h, and dried at 55℃ to obtain a high-toughness oxidation-resistant alkaline water electrolyzer membrane.

[0037] Preparation of zirconium ceroxyphosphonate polybenzimidazole: A1. Under nitrogen protection, 10.1g of 3,3′-diaminobenzidine free base, 7.8g of isophthalic acid, 120.0g of polyphosphoric acid and 10.0g of phosphorus pentoxide were added to the reactor. The stirring was started to mix the materials evenly. The mixture was stirred at 120℃ for 2h, heated to 160℃ for 4h, and then heated to 220℃ for 16h. After the reaction was completed, the mixture was cooled to 90℃, and the reactants were added to 800.0g of deionized water to precipitate the polymer. The precipitate was centrifuged, washed and dried to obtain the polybenzimidazole precursor.

[0038] A2. 15.0 g of polybenzimidazole precursor was added to a mixed solvent consisting of 160.0 g of anhydrous N,N-dimethylacetamide and 5.0 g of anhydrous lithium chloride. The mixture was stirred at 80 °C for 8 h, cooled to 55 °C, and 3.0 g of phenylphosphonic acid, 6.0 g of zirconium oxychloride octahydrate and 6.0 g of triethylamine were added. The reaction continued, followed by the addition of 4.0 g of cerium(III) nitrate hexahydrate, 1.0 g of citric acid, 10.0 g of urea and 60.0 g of deionized water. The mixture was reacted at 90 °C for 7 h, then transferred to a reaction vessel and solvated at 150 °C for 10 h. After cooling, the product was centrifuged, washed, dried, ground and sieved to obtain zirconium cerium oxyphosphonate polybenzimidazole.

[0039] Preparation of sulfopropylphosphonic acid benzimidazole fluorinated copolymer: B1. Add 30.0g of polyvinylidene fluoride-hexafluoropropylene copolymer to 240.0g of anhydrous N-methylpyrrolidone and 60.0g of anhydrous dimethyl sulfoxide, stir at 75℃ for 6h, cool to 50℃, dissolve 3.0g of potassium hydroxide in 3.0g of deionized water, and then add 0.6g of tetrabutylammonium bromide to obtain a mixture. Add this mixture to the above system and react at 50℃ for 2.5h to obtain an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution.

[0040] B2. Premix 3.0g of 2-aminoethylphosphonic acid, 5.0g of triethylamine, and 20.0g of anhydrous dimethyl sulfoxide to obtain an organic dispersion of 2-aminoethylphosphonic acid. Add 3.5g of the organic dispersion of 2-aminobenzimidazole and 2-aminoethylphosphonic acid to the activated polyvinylidene fluoride-hexafluoropropylene copolymer solution and react at 70℃ for 10h to obtain a reaction solution. Add the reaction solution to a mixture of 600.0g of ethanol and 600.0g of deionized water, centrifuge, wash, and dry to obtain a benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate. Add the obtained benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate to 120.0g of anhydrous N,N-dimethylacetamide and 40.0g of anhydrous dimethyl sulfoxide, disperse, and add 1.5g of... Sodium 3-bromopropane sulfonate and 1.5 g potassium carbonate were reacted at 90 °C, centrifuged, washed, and dried to obtain sulfopropionic acid benzimidazole fluoride copolymer.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that 5.0g of cerium oxyphosphonate zirconium polybenzimidazole is not added in step S1, while the rest is the same as in Example 1.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that, in step S1, 6.5g of sulfopropylphosphonic acid benzimidazole fluoride copolymer is not added; otherwise, it is the same as Example 1.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that, in step S1, 5.0g of cerium oxyphosphonate zirconium polybenzimidazole and 6.5g of sulfopropylphosphonate benzimazole fluoride copolymer are not added; otherwise, the same as in Example 1 is used.

[0044] The performance of the high-toughness, oxidation-resistant, alkaline water electrolyzer diaphragms obtained in Examples 1-3 and Comparative Examples 1-3 was tested.

[0045] The diaphragms prepared in Examples 1-3 and Comparative Examples 1-3 were cut into samples of the same size and placed in an environment of 25°C and 50% relative humidity for 24 hours before testing.

[0046] During the surface resistance test, the diaphragm is sandwiched between two inert electrodes. The electrolyte is a 30% potassium hydroxide aqueous solution. The test temperature is 80℃, and the effective test area is 10 cm². 2 First, the blank resistance of the electrolyte system without the diaphragm was tested, and then the total resistance after the diaphragm was clamped was tested. The high-frequency intercept resistance was obtained by AC impedance testing. The surface resistance was calculated by multiplying the total resistance by the effective test area after subtracting the blank resistance. Three samples were tested for each group of samples and the average value was taken.

[0047] During hydrogen permeability testing, the diaphragm was fixed in a gas permeation cell. Pure hydrogen was introduced into the inlet side, and nitrogen was introduced into the purge side. The test temperature was 80℃, the pressure difference was 0.1 MPa, and the effective permeation area was 10 cm². 2 After the hydrogen permeation reaches a stable state, the hydrogen concentration on the purge side is continuously collected. The hydrogen permeability is calculated based on the hydrogen permeation rate, membrane thickness, effective permeation area, test time, and pressure difference. Three samples are tested for each group of samples, and the average value is taken.

[0048] During the bubble point pressure test, the diaphragm was immersed in a 30% potassium hydroxide aqueous solution for 24 hours and then fixed in the bubble point test fixture to keep the diaphragm completely wet. The pressure was gradually increased from the gas side, and the generation of bubbles on the liquid side was observed. The pressure at which continuous and stable bubbles first appeared was recorded as the bubble point pressure. Three samples were tested for each group, and the average value was taken.

[0049] During the tensile strength test, the diaphragm was cut into strip specimens with an effective clamping distance of 50 mm. The specimens were stretched at 50 mm / min at 25°C. The maximum load before the specimen broke was recorded. The tensile strength was calculated based on the maximum load and the initial cross-sectional area of ​​the specimen. Five specimens were tested in each group and the average value was taken. During the elongation at break test, strip specimens and tensile conditions with the same tensile strength are used. The displacement change of the specimen at the time of breakage is recorded. The elongation at break is calculated based on the fracture displacement and the initial effective clamping distance. Five specimens are tested in each group and the average value is taken.

[0050] When testing the tensile strength retention rate after oxidation treatment, the initial tensile strength of the diaphragm was first determined according to the aforementioned method. Then, the diaphragm was immersed in an oxidation treatment solution containing 30% potassium hydroxide and 3% hydrogen peroxide by mass and treated at 80°C for 168 hours. After removal, it was washed with deionized water until no residual alkali solution remained on the surface and dried at 60°C until the mass was constant. The tensile strength after oxidation treatment was then determined according to the aforementioned tensile strength test method. The tensile strength retention rate after oxidation treatment was calculated based on the ratio of the tensile strength after oxidation treatment to the initial tensile strength. Five samples were tested for each group of samples, and the average value was taken.

[0051] The performance test data above are shown in Table 1.

[0052] Table 1 Performance Test Results The test results in Table 1 clearly show that Examples 1-3 exhibit significant improvements over Comparative Examples 1-3 in terms of ion conduction, gas barrier safety, pore structure stability, mechanical toughness, and oxidation resistance. This demonstrates that the present invention can effectively solve the problems of high surface resistivity, increased hydrogen cross-permeability, insufficient pore stability, poor flexibility, and mechanical performance degradation after long-term operation of existing alkaline water electrolyzer diaphragms under strong alkaline and oxidizing environments.

[0053] Specifically, the surface resistivity of Examples 1-3 is 0.152-0.171 Ω·cm. 2 This is significantly lower than the 0.243 Ω·cm of Comparative Example 1. 2 Comparative Example 2: 0.198 Ω·cm 2 And 0.286 Ω·cm in Comparative Example 3 2 This indicates that the simultaneous introduction of zirconium cerium oxyphosphonate polybenzimidazole and benzimidazole sulfonate fluorinated copolymer improves the alkali wetting and retention capacity and ion transport continuity inside the membrane, thereby reducing the ohmic impedance during electrolysis.

[0054] The hydrogen permeability of Examples 1-3 was 3.8 × 10⁻⁶. -12 -4.5×10 -12 mol·cm-1 ·s -1 ·bar -1 This is lower than the 6.9 × 10⁻⁶ of Comparative Example 1. -12 mol·cm -1 ·s -1 ·bar -1 Comparative Example 2: 5.8 × 10 -12 mol·cm -1 ·s -1 ·bar -1 And Comparative Example 3's 9.6 × 10 -12 mol·cm -1 ·s -1 ·bar -1 Meanwhile, the bubble point pressures of Examples 1-3 were 0.43-0.48 MPa, which were higher than those of Comparative Example 1 (0.34 MPa), Comparative Example 2 (0.38 MPa), and Comparative Example 3 (0.27 MPa). This indicates that the composite interface structure formed by the present invention can improve the uniformity of pores and wet sealing ability, reduce the risk of hydrogen cross-permeation, and improve the safety isolation performance of the diaphragm in the alkaline water electrolyzer.

[0055] From the perspective of mechanical properties, the tensile strength of Examples 1-3 was 39.8-42.6 MPa and the elongation at break was 22.4-27.6%, which were significantly higher than those of Comparative Example 3 (25.7 MPa and 9.8%), and also better than Comparative Examples 1 and 2, which lacked one of the modified compounds (zirconium ceroxyphosphonate polybenzimidazole or benzimidazole sulfonate fluorinated copolymer), respectively. This indicates that a relatively stable reinforcement and toughening system was formed between the polyphenylene sulfide fiber woven fabric, polyethersulfone resin, polybenzimidazole resin and the two modified compounds, reducing the embrittlement problem caused by the debonding of the inorganic clusters and organic resin interfaces.

[0056] In terms of oxidation resistance, the tensile strength retention rate of Examples 1-3 after oxidation treatment was 89.6-92.5%, which was significantly higher than that of Comparative Example 1 (75.8%), Comparative Example 2 (83.4%), and Comparative Example 3 (68.2%). Among them, the oxidation resistance retention rate of Comparative Example 1 decreased significantly after the absence of cerium oxyphosphonate zirconium polybenzimidazole, indicating that the modified compound plays an important role in mitigating damage from oxidizing species.

[0057] In Comparative Example 2, the lack of sulfopropylphosphonic acid benzimidazole fluorine copolymer resulted in a decrease in elongation at break to 12.7% and tensile strength to 30.4 MPa, indicating that the modified compound makes a significant contribution to flexible interface bridging and crack resistance.

[0058] Comparative Example 3, lacking both modified compounds (zirconium ceroxyphosphonate polybenzimidazole and benzimidazole sulfonate fluorinated copolymer), had the worst performance in all indicators, further demonstrating the synergistic effect between the two modified compounds.

[0059] In summary, Examples 1-3 improve hydrophilicity retention, ion solubilization, and oxidation resistance by using zirconium ceroxyphosphonate polybenzimidazole, and improve interfacial bonding and flexibility by using sulfopropylphosphonate benzimidazole fluoride copolymer, thereby solving the technical problem that existing membranes cannot simultaneously achieve low surface resistivity, low hydrogen permeation, high bubble point pressure, high toughness, and oxidation stability.

Claims

1. A method for preparing a high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm, characterized in that the steps include... include: S1. By weight, mix 160.0-220.0 parts of anhydrous N-methylpyrrolidone and 30.0-60.0 parts of anhydrous N,N-dimethylacetamide to obtain a mixed solvent; add 1.0-3.0 parts of dried anhydrous lithium chloride, 8.0-16.0 parts of polybenzimidazole resin and 35.0-50.0 parts of polyethersulfone resin to the mixed solvent, stir at 100-120℃, and cool to 7℃. At 5-85℃, add 6.0-12.0 parts of polyvinylidene fluoride-hexafluoropropylene copolymer, 5.0-10.0 parts of polyvinylpyrrolidone, 3.0-6.0 parts of polyethylene glycol-400 and 2.0-5.0 parts of glycerol, continue stirring, add 3.0-7.0 parts of zirconium cerium oxyphosphonate polybenzimidazole and 4.0-9.0 parts of sulfopropylphosphonate benzimazole fluoride copolymer, shear dispersion, degassing, to obtain membrane film-forming slurry; S2. Wash and dry 18.0-30.0 parts of polyphenylene sulfide fiber woven fabric to obtain pretreated polyphenylene sulfide fiber support fabric; A membrane-forming slurry is coated onto the surface of a pretreated polyphenylene sulfide (PPS) fiber support fabric to obtain a coated PPS fiber support fabric. The coated PPS fiber support fabric is pre-evaporated at 25-35°C, then immersed in deionized water at 20-30°C, and then washed in deionized water at 40-50°C. The washed membrane is then immersed in a potassium hydroxide aqueous solution, activated at 50-60°C, and dried at 45-55°C to obtain a high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer membrane.

2. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 1, characterized in that, In step S1, the polybenzimidazole resin is Celazole U-60 grade polybenzimidazole resin; the shear dispersion temperature is 50-60℃.

3. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 1, characterized in that, In step S2, the activation time at 50-60℃ is 4-8 hours.

4. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 1, characterized in that, The preparation method of the cerium oxyphosphonate zirconium polybenzimidazole includes: A1. By weight, under nitrogen protection, 9.9-10.1 parts of 3,3′-diaminobenzidine free base, 7.4-7.8 parts of isophthalic acid, 90.0-120.0 parts of polyphosphoric acid and 5.0-10.0 parts of phosphorus pentoxide are mixed and stirred at 110-120℃. The mixture is then heated to 150-160℃ and further heated to 200-220℃. After cooling to 80-90℃, 500.0-800.0 parts of deionized water are added. The mixture is then centrifuged, washed, and dried to obtain the polybenzimidazole precursor. A2. Add 10.0-15.0 parts of polybenzimidazole precursor to a mixed solvent of 120.0-160.0 parts of anhydrous N,N-dimethylacetamide and 3.0-5.0 parts of anhydrous lithium chloride, stir at 70-80℃, cool to 45-55℃, add 2.0-3.0 parts of phenylphosphonic acid, 4.0-6.0 parts of zirconium oxychloride octahydrate and 4.0-6.0 parts of triethylamine, and continue the reaction; then add 2.0-4.0 parts of cerium(III) nitrate hexahydrate, 0.5-1.0 parts of citric acid, 6.0-10.0 parts of urea and 40.0-60.0 parts of deionized water, react at 80-90℃, then transfer to a reaction vessel, solvothermal treat at 135-150℃, cool, centrifuge, wash, dry, grind and sieve.

5. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 4, characterized in that, In step A1, the stirring time at 110-120℃ is 1-2 hours; the reaction time at 150-160℃ is 3-4 hours; and the reaction time at 200-220℃ is 10-16 hours.

6. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 4, characterized in that, In step A2, the stirring time is 6-8 hours at 70-80℃; the reaction time is 5-7 hours at 80-90℃; and the solvothermal treatment time is 6-10 hours at 135-150℃.

7. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 1, characterized in that, The preparation method of the sulfoprophosphonic acid benzimidazole fluoride copolymer includes: B1. By weight, 20.0-30.0 parts of polyvinylidene fluoride-hexafluoropropylene copolymer are added to 180.0-240.0 parts of anhydrous N-methylpyrrolidone and 30.0-60.0 parts of anhydrous dimethyl sulfoxide. The mixture is stirred at 65-75°C, cooled to 45-50°C, and a mixture containing 1.0-3.0 parts of potassium hydroxide, 1.0-3.0 parts of deionized water and 0.2-0.6 parts of tetrabutylammonium bromide is added. The mixture is reacted at 45-50°C to obtain an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution. B2. Premix 1.5-3.0 parts of 2-aminoethylphosphonic acid, 3.0-5.0 parts of triethylamine, and 10.0-20.0 parts of anhydrous dimethyl sulfoxide to obtain an organic dispersion of 2-aminoethylphosphonic acid; add 2.0-3.5 parts of the organic dispersion of 2-aminobenzimidazole and 2-aminoethylphosphonic acid to an activated polyvinylidene fluoride-hexafluoropropylene copolymer solution, and react at 60-70℃ to obtain a reaction solution; add the reaction solution to a mixture of 800.0-1200.0 parts of ethanol and deionized water. The intermediate was obtained by centrifugation, washing, and drying to obtain benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene. The benzimidazole-aminoethylphosphonic acid double-grafted polyvinylidene fluoride-hexafluoropropylene intermediate was added to 80.0-120.0 parts of anhydrous N,N-dimethylacetamide and 20.0-40.0 parts of anhydrous dimethyl sulfoxide, dispersed, and then 0.8-1.5 parts of sodium 3-bromopropanesulfonate and 0.8-1.5 parts of potassium carbonate were added. The reaction was carried out at 75-90℃, followed by centrifugation, washing, and drying.

8. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 7, characterized in that, In step B1, the stirring time at 65-75℃ is 4-6 hours; the reaction time at 45-50℃ is 1.5-2.5 hours.

9. The method for preparing the high-toughness, oxidation-resistant, alkaline-resistant water electrolyzer diaphragm according to claim 7, characterized in that, In step B2, the reaction time is 8-10 hours at 60-70°C.

10. A high-toughness, oxidation-resistant, alkaline-resistant water electrolysis cell diaphragm, characterized in that, The high-toughness, oxidation-resistant, and alkaline-resistant water electrolyzer diaphragm is prepared according to any one of claims 1-9.

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