Composite diaphragm for electrolytic cell and preparation method of composite diaphragm
By optimizing the titanium-zirconium synergistic effect and hydrothermal reaction, a composite membrane with high conductivity and chemical stability was prepared, which solved the problems of insufficient ion conductivity, chemical stability and mechanical properties of existing membrane materials used in electrolyzers, and realized the efficient and stable operation of electrolyzers.
Patent Information
- Application Number
- CN202511602591.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-04
- Publication Date
- 2026-01-13
AI Technical Summary
Existing membrane materials for electrolytic cells have shortcomings in terms of ionic conductivity, chemical stability, and mechanical properties, especially under high current density conditions. Furthermore, asbestos membranes are harmful to the human body, polyphenylene sulfide membranes have low ionic conductivity, and polytetrafluoroethylene membranes are expensive.
By constructing a stable conductive network through the synergistic effect of titanium and zirconium, optimizing hydrothermal reaction conditions, G-TZO nanowires were prepared. Combined with polyphenylene sulfide nonwoven fabric and functional gradient layer, a composite membrane was formed to ensure the high stability and uniform dispersion of the oxide. Impurities were removed during the calcination process, resulting in a composite material with high conductivity and chemical stability.
A composite diaphragm with low surface resistivity, high alkali absorption rate, low gas flux and long-term stability has been achieved, which is suitable for electrolytic cells and improves electrolysis efficiency and safety.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of diaphragm, in particular to a composite diaphragm for electrolytic cell and a preparation method thereof. BACKGROUND
[0002] Electrolytic cell is a key device for converting electrical energy into chemical energy, which is widely used in chemical production, metal smelting, new energy storage and conversion, and many other fields. In the electrolytic cell, the diaphragm plays a crucial role. It not only needs to allow ions to pass through to ensure the smooth progress of the electrolysis reaction, but also needs to effectively block the mixing of gas and liquid to prevent short circuit and side reactions, thereby ensuring the efficient and stable operation of the electrolytic cell.
[0003] Currently, the common diaphragm materials for electrolytic cell in the market mainly include asbestos diaphragm, polyphenylene sulfide (PPS) diaphragm, polytetrafluoroethylene (PTFE) diaphragm, etc. Asbestos diaphragm has good chemical stability and thermal stability, and low cost, and has been widely used in electrolysis fields such as chlor-alkali industry. However, asbestos fibers are harmful to human health, and long-term exposure may cause diseases such as asbestos lung and lung cancer. With the improvement of environmental protection and safety awareness, the use of asbestos diaphragm is gradually restricted. Polyphenylene sulfide diaphragm has excellent chemical corrosion resistance, high temperature stability and mechanical strength, and shows good performance in electrolytic cell. However, pure polyphenylene sulfide diaphragm has the problem of low ion conductivity, which limits its application in high current density electrolysis conditions. Polytetrafluoroethylene diaphragm is known for its extremely low surface energy and excellent chemical inertness, which can effectively block the penetration of gas and liquid, but it also has the defect of insufficient ion conductivity, and the cost is relatively high. In order to improve the performance of the diaphragm, researchers have begun to explore the preparation technology of composite diaphragm. By compounding materials with different properties, it is expected to combine the advantages of each material to prepare a composite diaphragm with high ion conductivity, good chemical stability and mechanical properties.
[0004] In the preparation of composite diaphragm, various functional components such as inorganic nanoparticles and conductive polymers are usually introduced to improve the overall performance of the diaphragm. However, the existing technology has obvious deficiencies in regulating the synergistic effect between these functional components. Based on this, the present application proposes a composite diaphragm for electrolytic cell and a preparation method thereof. SUMMARY
[0005] The present application proposes a composite diaphragm for electrolytic cell and a preparation method thereof. By titanium-zirconium synergistic effect, a stable conductive network is constructed to balance the mechanical strength and chemical stability. By optimizing the hydrothermal reaction temperature, time and the amount of precipitating agent, high crystallinity and uniform dispersion of G-TZO nanowires are realized. By calcining in air atmosphere, high stability of oxides is ensured. Finally, a composite diaphragm for electrolytic cell with low surface resistance, high alkali absorption rate, low gas flux and long stability is obtained.
[0006] The technical scheme of the present application is as follows: In a first aspect, the present application provides a preparation method of a composite diaphragm for electrolytic cell, comprising the following steps: (1) The polyphenylene sulfide non-woven fabric is uniformly passed through the h-BN / PVDF slurry at a speed of 2-4 cm / s, then enters the preheating zone, and is pre-evaporated at a temperature of 55±2℃ for 55-65 s; then enters the deionized water at 25±2℃ for 5-7 min, is washed with deionized water, and then enters the 60-70℃ oven for drying for 10-20 min to obtain a fiber reinforced layer for standby use; (2) The fiber reinforced layer is fixed flat on a glass plate carrier, and a doctor blade with a gap of 200 μm is used to uniformly coat the functional gradient layer on the reinforced layer, and the coated film is immediately moved into the pre-evaporation heating zone, and the temperature is controlled at 40-45℃, and the evaporation time is 90-100 s; (3) The film together with the carrier is immersed in deionized water at 25±1℃ for 2-4 min; it is quickly transferred to 28%-32% v / v NMP aqueous solution at 55-65℃ for 8-10 min; after being taken out, it is washed with deionized water, and is treated in the 80-90℃ oven for 15-20 min to obtain a base layer; (4) The base layer is subjected to nitrogen treatment, and a pressure of 3.0±0.2 MPa is applied for 10-15 min; an ultrasonic spraying device is used to uniformly spray the surface selection layer coating liquid on the surface of the functional layer subjected to pre-pressing treatment; the spraying amount is controlled so that the dry coating thickness is 3-5 μm, and the coating is first dried at 80±5℃ for 20-30 min to remove the solvent, and then heat treated at 130±5℃ for 30-40 min to obtain the composite diaphragm for electrolytic cell.
[0007] As a further technical scheme, the polyphenylene sulfide non-woven fabric has a thickness of 70-80 μm and a grammage of 55-65 g / m 2 .
[0008] As a further technical scheme, the configuration method of the h-BN / PVDF slurry comprises: slowly adding polyvinylidene fluoride into N-methyl pyrrolidone, and stirring in a water bath at 55-65℃ until completely dissolved; then adding boron nitride nanosheets with an average particle size of 1-2 μm and an average thickness of 5-10 nm, and dispersing for 30-40 min at 7000-8000 rpm using a high-speed shearing emulsifier to form the h-BN / PVDF slurry; and the weight ratio of the polyvinylidene fluoride, N-methyl pyrrolidone and boron nitride nanosheets is 1.5-2:0.5-1:97-98.
[0009] As a further technical solution, the preparation method of the casting solution comprises: first, vacuum drying the polysulfone and polyether sulfone ketone at 65-75 DEG C for 4-5 h to remove moisture; then, adding the polymers into N-methyl pyrrolidone, mechanically stirring at 70-80 DEG C under nitrogen protection for 6-8 h until completely dissolved, then adding polyvinyl pyrrolidone and hydroxyapatite nanowires with an average diameter of 40-50 nm and an average length of 5-10 microns in sequence, continuing to stir for 4 h, and finally standing for 12 h to remove bubbles, to obtain the casting solution.
[0010] As a further technical solution, the weight ratio of the polysulfone, polyether sulfone ketone, hydroxyapatite nanowires, N-methyl pyrrolidone and polyvinyl pyrrolidone is 8-9:4-5:3-4:70-75:10-12.
[0011] As a further technical solution, the preparation method of the surface selection layer coating solution comprises: mixing the G-TZO powder with ethylene glycol, and ultrasonic dispersing for 50-60 min to form a pre-dispersion; then, slowly adding the pre-dispersion into an ethanol solution of perfluorosulfonic acid resin, and magnetically stirring at room temperature for 22-24 h to obtain.
[0012] As a further technical solution, the weight ratio of the perfluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol is 85-90:5-10:5-7:5-8.
[0013] As a further technical solution, the preparation method of the G-TZO powder comprises: after pretreatment, adding titanium sulfate and zirconium chloride to the GO dispersion liquid at 250-300 rpm, and continuously stirring for 2-3 h, continuously adding urea, continuously stirring until completely dissolved, and adding dilute ammonia water drop by drop, and adjusting the pH value of the mixed solution to 2.0-2.5; then, transferring to a reaction kettle, adding hydrazine hydrate to the reaction kettle, and heating from room temperature to 180-200 DEG C at a rate of 2 DEG C / min, and reacting for 16-20 h; after the reaction is completed, naturally cooling to room temperature, centrifuging, washing and drying to obtain black G-TZO precursor powder; heating from room temperature to 400-500 DEG C at a rate of 3 DEG C / min under air, and keeping the temperature for 2-4 h to obtain.
[0014] After adding urea into the mixed solution and stirring until completely dissolved, dilute ammonia water is added dropwise to adjust the pH value of the mixed solution to 2.0-2.5. The adjustment of the pH value has an important influence on the crystallization process of the G-TZO precursor. A suitable pH value can control the hydrolysis and precipitation rate of metal ions, and promote the formation of ordered crystalline structure of metal ions on the GO surface. An unsuitable pH value can cause abnormal crystallization process, forming irregular crystal structure or agglomerates, affecting the performance of the G-TZO powder. Therefore, the pH adjustment and the crystallization process are mutually coordinated, which jointly determines the crystal structure and morphology of the G-TZO precursor.
[0015] As a further technical solution, the pretreatment step comprises: ultrasonic treatment of the GO dispersion solution under ice water bath conditions at a power of 400-500W for 30-40min.
[0016] In the preparation of the G-TZO powder, the GO dispersion solution is first pretreated by ultrasonic treatment under ice water bath conditions. This step can make the GO dispersion solution more uniform and reduce the agglomeration phenomenon, providing a good basis for subsequent mixing with metal ions. Subsequently, titanyl sulfate and zirconium chloride are added to the pretreated GO dispersion solution under stirring conditions, and the metal ions are fully contacted and mixed with GO under continuous stirring. The pretreated GO dispersion solution provides a uniform dispersion environment for the metal ions, and the stirring process promotes the adsorption and combination of the metal ions on the GO surface, which synergistically facilitates the formation of a uniform composite precursor.
[0017] In a second aspect, the application provides a composite diaphragm for an electrolytic cell, which is prepared by the preparation method of the composite diaphragm for an electrolytic cell.
[0018] The working principle and beneficial effects of the application are as follows: The G-TZO powder of the application uses GO (graphene oxide), titanyl sulfate, zirconium chloride, urea, etc. as raw materials, and the GO and titanium and zirconium compounds synergistically act. The two-dimensional structure of GO can be used as a carrier to uniformly disperse titanium and zirconium compounds, so that they form a nanoscale composite structure. In the subsequent reaction and treatment process, titanium and zirconium elements interact with GO, not only improving the conductivity of GO, but also utilizing the chemical stability of titanium and zirconium oxides to enhance the resistance of the composite material in the alkaline electrolytic environment. This synergistic effect enables the G-TZO powder to simultaneously have high conductivity and good chemical stability, providing key performance guarantees for the application of the composite diaphragm in the electrolytic cell.
[0019] In the preparation process of the G-TZO powder, the ice water bath environment can control the temperature of the reaction system, avoiding the destruction of the GO structure caused by the high temperature generated by ultrasonic treatment. Ultrasonic treatment can reduce the agglomeration of GO sheets, ensuring uniform and consistent composite structure. After adding titanyl sulfate and zirconium chloride, continuous stirring is performed to make metal ions uniformly adsorbed on the surface of GO. Urea is continuously added as a precipitating agent, which promotes the reaction between metal ions and GO to form a G-TZO precursor. In this process, the surface active sites of GO interact with metal ions, guiding the formation and growth of the precursor, so that the nanomaterial has a specific morphology and structure. During the hydrothermal process, the addition of hydrazine hydrate promotes the transformation of the G-TZO precursor to a stable crystal structure, forming a nanomaterial with good crystallinity and pore structure, which is crucial for ion conduction in the composite separator. The appropriate pore structure can provide ion transmission channels while ensuring the mechanical strength of the separator. Subsequently, the calcination process further removes impurities and organic matter in the G-TZO precursor, making the crystal structure more perfect and stable. Calcination in air atmosphere ensures that the oxides exist in the appropriate valence state, maintaining the chemical stability of titanium and zirconium oxides. By precisely controlling the calcination conditions, the G-TZO powder has an ideal crystal structure and chemical composition, thereby playing the best role in conductivity and stability in the composite separator. DETAILED DESCRIPTION
[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The raw materials in the present application are commercially available.
[0021] Embodiment 1 The present embodiment provides a preparation method of a composite separator for an electrolytic cell, comprising the following steps: (1) A polyphenylene sulfide non-woven fabric with a thickness of 75 μm, a grammage of 60 g / m 2 was uniformly passed through the immersion containing h-BN / PVDF slurry at a speed of 3 m / s, and then entered the preheating zone to pre-evaporate at a temperature of 55℃ for 60 s. Then it entered the deionized water at 25℃ for 6 min, was washed with deionized water, and then entered the 65℃ oven for drying for 15 min to obtain a fiber reinforced layer for standby use; The configuration method of the h-BN / PVDF slurry comprises: slowly adding polyvinylidene fluoride into N-methyl pyrrolidone, stirring in a 60°C water bath until completely dissolved; then adding boron nitride nanosheets with an average particle size of 1.5 μm and an average thickness of 8 nm, dispersing for 35 min at 7500 rpm using a high-speed shearing emulsifier to form a uniform and stable suspension slurry; the weight ratio of polyvinylidene fluoride, N-methyl pyrrolidone and boron nitride nanosheets is 1.8:0.8:97.4; (2) The fiber reinforced layer is fixed flat on the glass plate carrier, a casting solution of the functional gradient layer is uniformly coated on the reinforced layer using a doctor blade with a gap of 200 μm, and the coated film is immediately moved into a pre-evaporation heating zone, the temperature is controlled at 42°C, and the evaporation time is 95 s; The preparation method of the casting solution comprises: first, drying polysulfone and polyether sulfone ketone at 70°C under vacuum for 4.5 h to remove water; then, adding the polymers into N-methyl pyrrolidone, stirring mechanically at 75°C under nitrogen protection for 7 h until completely dissolved, then sequentially adding polyvinylpyrrolidone and hydroxyapatite nanowires with an average diameter of 45 nm and an average length of 8 μm, continuing to stir for 4 h, and finally standing for 12 h to remove bubbles to obtain a uniform and transparent casting solution; the weight ratio of polysulfone, polyether sulfone ketone, hydroxyapatite nanowires, N-methyl pyrrolidone and polyvinylpyrrolidone is 8.5:4.5:3.5:72:11; (3) The film is immersed in 25°C deionized water together with the carrier for 3 min; it is quickly transferred to a 60°C 30% v / v NMP aqueous solution and stays for 9 min; after being taken out, it is washed with deionized water and treated in an 85°C oven for 18 min to obtain the base layer; (4) The base layer is subjected to nitrogen treatment, a pressure of 3.0 MPa is applied and the pressure is maintained for 12 min; a surface selection layer coating solution is uniformly sprayed on the surface of the functional layer subjected to pre-pressing treatment using an ultrasonic spraying device; the spraying amount is controlled so that the dry coating thickness is 4 μm, the coating is first dried at 80°C for 25 min to remove the solvent, and then heat-treated at 130°C for 35 min to obtain the composite diaphragm for electrolytic cells.
[0022] The preparation method of the surface selection layer coating solution comprises: The preparation method of the G-TZO powder comprises the following steps: 1500 mL of GO dispersion liquid with a concentration of 5 mg / mL is prepared, and the prepared GO dispersion liquid is pretreated by pulse ultrasonic treatment under the condition of ice water bath at a power of 450 W, 2 s of work and 1 s of interval, and for 5 min; the pretreated GO dispersion liquid is added into 64.2 g of titanyl sulfate and 38.5 g of zirconium oxychloride under stirring at 280 rpm, and the stirring is continued for 2.5 h; 45 g of urea is continuously added and stirred until completely dissolved; dilute ammonia water is added drop by drop, and the pH value of the mixed solution is adjusted to 2.2; then the mixed solution is transferred into a stainless steel hydrothermal reaction kettle with a polytetrafluoroethylene liner, the filling degree is controlled to be 70%, 1.1 mL of hydrazine hydrate is added into the reaction kettle, the temperature is increased from room temperature to 190 ℃ at a rate of 2 ℃ / min, and the reaction is carried out for 18 h; after the reaction is completed, the reaction kettle is naturally cooled to room temperature, and the filter cake after washing is dried in a vacuum drying box at 80 ℃ for 12 h to obtain a black G-TZO precursor powder; the G-TZO precursor powder is heated from room temperature to 450 ℃ at a rate of 3 ℃ / min under air, and the temperature is kept at 450 ℃ for 3 h to obtain a G-TZO powder. - The G-TZO powder is mixed with ethylene glycol, and ultrasonic dispersion is carried out for 55 min to form a pre-dispersion; then the pre-dispersion is slowly added into an ethanol solution of perfluorosulfonic acid resin, and magnetic stirring is carried out at room temperature for 23 h, so that the pre-dispersion is fully mixed and aged to obtain a G-TZO composite electrolyte; the weight ratio of the perfluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol is 88:8:6:7. The G-TZO powder is mixed with ethylene glycol, and ultrasonic dispersion is carried out for 55 min to form a pre-dispersion; then the pre-dispersion is slowly added into an ethanol solution of perfluorosulfonic acid resin, and magnetic stirring is carried out at room temperature for 23 h, so that the pre-dispersion is fully mixed and aged to obtain a G-TZO composite electrolyte; the weight ratio of the perfluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol is 88:8:6:7.
[0023] Example 2 The preparation method of the composite diaphragm for the electrolytic cell comprises the following steps: (1) a polyphenylene sulfide non-woven fabric with a thickness of 70 μm and a grammage of 55 g / m 2 is uniformly passed through an impregnation containing h-BN / PVDF slurry at a speed of 2 cm / s, and then enters a preheating zone to pre-evaporate at a temperature of 55 ℃ for 55 s; then the fabric enters deionized water at 25 ℃ for 5 min, is washed with deionized water, and then enters a drying oven at 60 ℃ for 10 min to obtain a fiber reinforced layer for standby use; The configuration method of the h-BN / PVDF slurry comprises the following steps: polyvinylidene fluoride is slowly added into N-methyl pyrrolidone, and stirring is carried out in a water bath at 55 ℃ until the polyvinylidene fluoride is completely dissolved; then boron nitride nanosheets with an average particle size of 1 μm and an average thickness of 5 nm are added, a high-speed shearing emulsifier is used to disperse the boron nitride nanosheets at 7000 rpm for 30 min to form a uniform and stable suspension slurry; the weight ratio of the polyvinylidene fluoride, N-methyl pyrrolidone and boron nitride nanosheet is 1.5:0.5:97. (2) The fiber reinforced layer is fixed flat on the glass plate carrier, and the functional gradient layer casting solution is uniformly coated on the reinforced layer using a doctor blade with a gap of 200 pm. The coated film is immediately moved into a pre-evaporation heating zone, and the temperature is controlled at 40°C. The evaporation time is 90 s; The preparation method of the casting solution comprises: first, drying polysulfone and polyether sulfone ketone at 65°C under vacuum for 4 h to remove moisture. Then, the polymers are added to N-methyl pyrrolidone, mechanically stirred at 70°C under nitrogen protection for 6 h until completely dissolved, then polyvinyl pyrrolidone and hydroxyapatite nanowires with an average diameter of 40 nm and an average length of 5 pm are added in sequence, continue to stir for 4 h, and finally stand for 12 h to remove bubbles to obtain a uniform and transparent casting solution; the weight ratio of polysulfone, polyether sulfone ketone, hydroxyapatite nanowires, N-methyl pyrrolidone and polyvinyl pyrrolidone is 8:4:3:70:10; (3) The film is immersed in 25°C deionized water for 2 min, quickly transferred to 55°C 28% v / v NMP aqueous solution for 8 min, then taken out and washed with deionized water, and treated in an 80°C oven for 15 min to obtain the base layer; (4) The base layer is subjected to nitrogen treatment, and a pressure of 3.0 MPa is applied for 10 min. The surface selection layer coating solution is uniformly sprayed on the surface of the functional layer treated by pre-pressing using an ultrasonic spraying device. The spraying amount is controlled so that the dry coating thickness is 3 pm. First, the coating is dried at 80°C for 20 min to remove the solvent, and then heat treated at 130°C for 30 min to obtain the composite diaphragm for electrolytic cells; The preparation method of the surface selection layer coating solution comprises: The preparation method of the G-TZO powder comprises: taking 1000 mL of GO dispersion solution with a concentration of 5 mg / mL, and under ice water bath conditions, pulsed ultrasonic treatment is performed at a power of 400 W, working for 2 s and intermittent for 1 s, for 30 min. The pretreated GO dispersion solution is added to 64.2 g of titania sulfate and 38.5 g of zirconium oxychloride under stirring at 250 rpm, and the stirring is continued for 2 h. 45 g of urea is continuously added and stirred until completely dissolved. Dilute ammonia water is added dropwise, and the pH value of the mixed solution is adjusted to 2.0. Then, it is transferred to a stainless steel hydrothermal reaction kettle with a polytetrafluoroethylene liner, and the filling degree is controlled at 70%. 1.0 mL of hydrazine hydrate is added to the reaction kettle, and the temperature is increased from room temperature to 180°C at a rate of 2°C / min, and the reaction is carried out for 16 h. After the reaction is completed, it is naturally cooled to room temperature, and centrifugal washing (8000 rpm, 10 min) is alternately performed with deionized water and anhydrous ethanol until the pH value of the supernatant is neutral and no Cl is detected with 0.1M AgNO3 solution -The washed filter cake was dried in a vacuum drying oven at 80°C for 12h to obtain black G-TZO precursor powder; the G-TZO precursor powder was heated at a rate of 3°C / min from room temperature to 400°C under air and kept at the temperature for 2h to obtain; The G-TZO powder was mixed with ethylene glycol and ultrasonically dispersed for 50min to form a pre-dispersion; then the pre-dispersion was slowly added dropwise into an ethanol solution of perfluorosulfonic acid resin, and was magnetically stirred at room temperature for 22h to obtain a mixture after sufficient mixing and aging; the weight ratio of the perfluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol was 85:5:5:5.
[0024] Example 3 The present embodiment provides a preparation method of a composite diaphragm for an electrolytic cell, which comprises the following steps: (1) A polyphenylene sulfide non-woven fabric with a thickness of 80μm and a grammage of 65g / m 2 was uniformly passed through an immersion containing h-BN / PVDF slurry at a speed of 4cm / s, and then entered a preheating zone to pre-evaporate at a temperature of 55°C for 65s; then the fabric entered deionized water at 25°C for 7min, was washed with deionized water, and then entered a drying oven at 70°C for 20min to obtain a fiber reinforced layer for standby use; The preparation method of the h-BN / PVDF slurry comprises the following steps: polyvinylidene fluoride was slowly added into N-methyl pyrrolidone, and was stirred in a water bath at 65°C until completely dissolved; then boron nitride nanosheets with an average particle size of 2μm and an average thickness of 10nm were added, and a high-speed shearing emulsifier was used to disperse the mixture at 8000rpm for 40min to form a uniform and stable suspension slurry; the weight ratio of polyvinylidene fluoride, N-methyl pyrrolidone and boron nitride nanosheets was 2:1:98; (2) The fiber reinforced layer was evenly fixed on a glass plate carrier, and a doctor blade with a gap of 200μm was used to uniformly coat the functional gradient layer casting solution on the reinforced layer, and the coated film was immediately moved into a pre-evaporation heating zone, and the temperature was controlled at 45°C, and the evaporation time was 100s; The preparation method of the casting solution comprises the following steps: polysulfone and polyether sulfone ketone were vacuum dried at 75°C for 5h to remove water; then the polymers were added into N-methyl pyrrolidone, and were mechanically stirred at 80°C under nitrogen protection for 8h until completely dissolved, then polyvinylpyrrolidone and hydroxyapatite nanowires with an average diameter of 50nm and an average length of 10μm were added in sequence, and the stirring was continued for 4h, and finally the mixture was left to stand for 12h to remove bubbles, to obtain a uniform and transparent casting solution; the weight ratio of polysulfone, polyether sulfone ketone, hydroxyapatite nanowires, N-methyl pyrrolidone and polyvinylpyrrolidone was 9:5:4:75:12; (3) immerse the membrane together with the carrier in deionized water at 25℃ for 4 min; quickly transfer to 32% v / v NMP aqueous solution at 65℃ for 10 min; after taking out, rinse with deionized water, and obtain the base layer after treatment in a 90℃ oven for 20 min; (4) pass the base layer into nitrogen, and apply a pressure of 3.0 MPa for 15 min; uniformly spray the surface selection layer coating liquid on the surface of the function layer treated by pre-pressing by using an ultrasonic spraying device; control the spraying amount so that the dry coating thickness is 5 μm, dry at 80℃ for 30 min to remove the solvent, and then heat treat at 130℃ for 40 min to obtain the composite diaphragm for electrolytic cell; The preparation method of the surface selection layer coating liquid comprises: The preparation method of the G-TZO powder comprises: taking 2000 mL of GO dispersion liquid with a concentration of 5 mg / mL, under the condition of ice water bath, pulse ultrasonic at a power of 500 W, work for 2 s, and intermittent for 1 s, and treat for 40 min; add 64.2 g of titanyl sulfate and 38.5 g of zirconium oxychloride to the pretreated GO dispersion liquid under stirring at 300 rpm, and continue to stir for 3 h; continue to add 45 g of urea, and continue to stir until completely dissolved; add dilute ammonia water drop by drop, and adjust the pH value of the mixed solution to 2.5; then transfer to a stainless steel hydrothermal reaction kettle with a polytetrafluoroethylene liner, control the filling degree to 70%, add 1.2 mL of hydrazine hydrate to the reaction kettle, and heat from room temperature to 200℃ at a rate of 2℃ / min, and react for 20 h; after the reaction is completed, naturally cool to room temperature, and centrifugally wash (8000 rpm, 10 min) alternately with deionized water and anhydrous ethanol until the pH value of the supernatant is neutral and there is no Cl detected by using 0.1M AgNO3 solution; dry the washed filter cake in a vacuum drying oven at 80℃ for 12 h to obtain black G-TZO precursor powder; heat from room temperature to 500℃ at a rate of 3℃ / min under air, and heat at the temperature for 4 h to obtain; - Mix the G-TZO powder with ethylene glycol, and ultrasonic disperse for 60 min to form a pre-dispersion; then slowly drop the pre-dispersion into a full-fluorosulfonic acid resin ethanol solution, and magnetically stir at room temperature for 24 h to fully mix and mature to obtain; the weight ratio of the full-fluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol is 90:10:7:8.
[0025] Comparative Example 1 On the basis of Example 1, the amount of titanyl sulfate is changed to 80.0 g, and the amount of zirconium oxychloride is changed to 22.7 g in Comparative Example 1, and the total metal ion molar mass is kept close to that of Example 1.
[0026] Comparative Example 2 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the amount of urea in Comparative Example 2 was changed to 22.5 g.
[0027] Comparative Example 3 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the hydrothermal reaction temperature in Comparative Example 3 was changed to 170℃.
[0028] Comparative Example 4 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the hydrothermal reaction time in Comparative Example 4 was changed to 9 h.
[0029] Comparative Example 5 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the calcination condition in Comparative Example 5 was changed to heating to 450℃ at 3℃ / min under nitrogen atmosphere, and holding for 3 h.
[0030] Comparative Example 6 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the weight ratio of perfluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol in Comparative Example 6 was changed to 85:8:12:5.
[0031] Comparative Example 7 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the G-TZO powder in Comparative Example 7 was changed to graphene / zirconium oxide composite, and the preparation method was as follows: the pretreated GO dispersion liquid was only added with 38.5 g of zirconium oxychloride under 280 rpm, without adding titanium sulfate, and stirring was continued for 2.5 h, and then 45 g of urea was added, and the subsequent steps were the same as those of Example 1.
[0032] Comparative Example 8 Adjustment was made on the basis of Example 1, and the difference from Example 1 was that the G-TZO powder in Comparative Example 8 was changed to graphene / titanium oxide composite, and the preparation method was as follows: the pretreated GO dispersion liquid was only added with 64.2 g of titanium sulfate under 280 rpm, without adding zirconium oxychloride, and stirring was continued for 2.5 h, and then 45 g of urea was added, and the subsequent steps were the same as those of Example 1.
[0033] Test Example: The separators prepared in the foregoing Examples 1-3 and Comparative Examples 1-8 were tested as follows: Surface resistance and alkali absorption rate test: Referring to the national electronic industry standard SJ-T 10171, the composite separator was treated in a 30wt% potassium hydroxide solution at 80℃ for 30 days, and then tested.
[0034] Gas permeability test: The gas permeability was tested by a Bunsen gas permeability tester, and the gas flux under 5 bar was tested in an ethanol system.
[0035] Stability test: Electrochemical test was performed with zero-gap electrolytic cell. Active nickel material on nickel foam substrate was used for cathode and anode electrode, electrolyte was 30wt% potassium hydroxide solution, and the flow rate was 20sccm for both cathode and anode side, current density was 300mA / cm 2 The test was carried out as follows, and the time taken for the cell voltage to decay by 10%.
[0036] The results are shown in Table 1 below: Table 1
[0037] In combination with the above, it can be seen that Examples 1-3 all exhibit low face resistance, high alkali absorption rate, low gas flux and high stability, indicating that the preparation parameters are well optimized. Example 1 is the best, with the lowest face resistance, the highest alkali absorption rate, the lowest gas flux and the longest stability. The slight decline in performance of Examples 2 and 3 due to parameter fine-tuning is still within an acceptable range, reflecting the robustness of the preparation method.
[0038] Comparative Example 1 adjusts the amount of titanyl sulfate and zirconium oxychloride, keeping the total metal ion molar mass similar, the face resistance increases, the alkali absorption rate decreases, the gas flux increases and the stability decreases. This shows that the change in titanium-zirconium ratio destroys the ideal crystal structure of the G-TZO powder, leading to a decrease in electrical conductivity and chemical stability. The total metal ion molar mass is similar but the ratio is unbalanced, affecting the synergistic effect of the oxides.
[0039] Comparative Example 2 reduces the amount of urea by half, the face resistance increases significantly, the alkali absorption rate decreases, the gas flux increases and the stability decreases. As a precipitating agent, a decrease in the amount of urea leads to incomplete formation of G-TZO precursors, poor morphology of nanomaterials, and thus reduced uniformity and durability of the separator.
[0040] Comparative Example 3 reduces the hydrothermal reaction temperature to 170°C, the face resistance is high, the alkali absorption rate is low, the gas flux is high and the stability is poor. Insufficient hydrothermal temperature results in low crystallinity of G-TZO and poor development of pore structure, affecting the ion conduction and mechanical strength of the separator.
[0041] Comparative Example 4 shortens the hydrothermal reaction time to 9h, the face resistance further increases, the alkali absorption rate is low, the gas flux is high and the stability decreases significantly. Insufficient reaction time leads to insufficient synthesis of G-TZO, uneven size and distribution of nanomaterials, and exacerbates the aging of the separator.
[0042] Comparative Example 5 changes the calcination condition to nitrogen atmosphere, the face resistance is relatively low, but the gas flux is relatively high and the stability is extremely poor. Nitrogen calcination partially reduces G-TZO, enhancing electrical conductivity, but reducing the chemical stability of the oxides, which are easily degraded in the electrolytic environment, leading to a shortened lifespan.
[0043] Comparative Example 6 adjusts the surface selection layer coating liquid ratio, increases the G-TZO powder ratio, the surface resistance is high, the alkali absorption rate is low, the gas flux is high and the stability is the lowest. The excess of G-TZO powder destroys the integrity of the coating, causing cracks and pores, increasing the gas permeation and reducing the mechanical strength.
[0044] Comparative Example 7 adjusts the G-TZO powder to graphene / zirconium oxide composite, the surface resistance is high, the alkali absorption rate is low, the gas flux is high and the stability is poor. The lack of titanium component leads to a significant decrease in electrical conductivity, and the zirconium oxide is not stable in the alkaline environment, and the diaphragm is easy to fail.
[0045] Comparative Example 8 adjusts the G-TZO powder to graphene / titanium oxide composite, the surface resistance is high, the alkali absorption rate is low, the gas flux is high and the stability is poor. The lack of zirconium component makes titanium oxide easy to corrode in high temperature lye, reducing durability, while the electrical conductivity is not as good as G-TZO composite.
[0046] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing a composite diaphragm for an electrolytic cell, characterized in that, Includes the following steps: (1) The polyphenylene sulfide nonwoven fabric is passed through the impregnation of h-BN / PVDF slurry at a speed of 2-4 cm / s, and then enters the preheating zone. It is pre-evaporated at a temperature of 55±2℃ for 55-65s; then it is immersed in deionized water at 25±2℃ for 5-7min, rinsed with deionized water, and dried in an oven at 60-70℃ for 10-20min to obtain the fiber reinforcement layer for later use. (2) Fix the fiber reinforcement layer flat on the glass plate carrier, use a scraper with a gap of 200μm to evenly coat the functional gradient layer casting solution on the reinforcement layer, and immediately move the coated film into the pre-evaporation heating zone, control the temperature at 40-45℃ and the evaporation time at 90-100s. (3) Immerse the membrane and the carrier in deionized water at 25±1℃ for 2-4 min; quickly transfer to 28%-32% v / v NMP aqueous solution at 55-65℃ for 8-10 min; after taking it out, rinse with deionized water and treat in an oven at 80-90℃ for 15-20 min to obtain the substrate layer. (4) Nitrogen gas is introduced into the substrate layer and a pressure of 3.0±0.2MPa is applied for 10-15 minutes. Using an ultrasonic spraying device, the surface selective coating liquid is uniformly sprayed onto the surface of the pre-pressed functional layer. The spraying amount is controlled so that the dry coating thickness is 3-5μm. The solvent is removed by drying at 80±5℃ for 20-30 minutes, and then heat-treated at 130±5℃ for 30-40 minutes to obtain the composite diaphragm for the electrolytic cell.
2. The method for preparing a composite diaphragm for an electrolytic cell according to claim 1, characterized in that, The polyphenylene sulfide nonwoven fabric has a thickness of 70-80 μm and a basis weight of 55-65 g / m². 2 .
3. The method for preparing a composite diaphragm for an electrolytic cell according to claim 1, characterized in that, The preparation method of the h-BN / PVDF slurry includes the following steps: slowly adding polyvinylidene fluoride to N-methylpyrrolidone and stirring in a water bath at 55-65℃ until completely dissolved; then adding boron nitride nanosheets with an average particle size of 1-2μm and an average thickness of 5-10nm, and dispersing them at 7000-8000rpm for 30-40min using a high-speed shear emulsifier to form the h-BN / PVDF slurry; the weight ratio of polyvinylidene fluoride, N-methylpyrrolidone and boron nitride nanosheets is 1.5-2:0.5-1:97-98.
4. The method for preparing a composite diaphragm for an electrolytic cell according to claim 1, characterized in that, The preparation method of the casting solution includes the following steps: First, polysulfone and polyethersulfone ketone are vacuum dried at 65-75℃ for 4-5 hours to remove moisture. Then, the polymer is added to N-methylpyrrolidone and mechanically stirred at 70-80℃ under nitrogen protection for 6-8 hours until completely dissolved. Then, polyvinylpyrrolidone and hydroxyapatite nanowires with an average diameter of 40-50 nm and an average length of 5-10 μm are added sequentially, and stirring is continued for 4 hours. Finally, the mixture is allowed to stand for 12 hours to remove bubbles, and the casting solution is obtained.
5. The method for preparing a composite diaphragm for an electrolytic cell according to claim 4, characterized in that, The weight ratio of polysulfone, polyethersulfone ketone, hydroxyapatite nanowires, N-methylpyrrolidone and polyvinylpyrrolidone is 8-9:4-5:3-4:70-75:10-12.
6. The method for preparing a composite diaphragm for an electrolytic cell according to claim 1, characterized in that, The preparation method of the surface selective coating liquid includes: mixing G-TZO powder with ethylene glycol and ultrasonically dispersing for 50-60 min to form a pre-dispersion; then slowly adding the pre-dispersion dropwise to an ethanol solution of perfluorosulfonic acid resin and magnetically stirring at room temperature for 22-24 h to ensure thorough mixing and maturation.
7. The method for preparing a composite diaphragm for an electrolytic cell according to claim 6, characterized in that, The weight ratio of the perfluorosulfonic acid resin, ethanol, G-TZO powder and ethylene glycol is 85-90:5-10:5-7:5-8.
8. The method for preparing a composite diaphragm for an electrolytic cell according to claim 6, characterized in that, The preparation method of the G-TZO powder includes: after pretreatment of GO dispersion, adding titanium oxysulfate and zirconium chloride at 250-300 rpm and stirring continuously for 2-3 hours, adding urea and stirring until completely dissolved, adding dilute ammonia dropwise to adjust the pH of the mixed solution to 2.0-2.5; then transferring to a reaction vessel, adding hydrazine hydrate to the reaction vessel, and heating from room temperature to 180-200℃ at a rate of 2℃ / min for 16-20 hours; after the reaction is completed, naturally cooling to room temperature, centrifuging, washing, and drying to obtain black G-TZO precursor powder; and then heating in air at a rate of 3℃ / min from room temperature to 400-500℃ and holding for 2-4 hours to obtain the product.
9. The method for preparing a composite diaphragm for an electrolytic cell according to claim 8, characterized in that, The pretreatment includes the following steps: treating the GO dispersion with ultrasound at 400-500W power for 30-40 minutes under ice-water bath conditions.
10. A composite diaphragm for an electrolytic cell, characterized in that, It is prepared by the method for preparing a composite diaphragm for an electrolytic cell according to any one of claims 1-9.