A Biphasic Continuous Sponge-Like Porous Structure Electrolyzed Water Composite Diaphragm and Preparation Method

Abstract

The present invention discloses an electrolyzed water composite diaphragm, which is composed of an alkali-resistant polymer and zirconia. The surface of the diaphragm has a porous layer, and the interior of the diaphragm has a bicontinuous porous structure. During preparation, an organic solvent and a diluent are first mixed, and then an alkali-resistant polymer and nano-zirconia particles are successively added to obtain a casting solution. The casting solution is placed on a clean glass plate and scraped to prepare a liquid film. Finally, it is quickly placed in a coagulation bath. By introducing an additive into the casting solution, preformed microphase separation is formed by temperature, and then solvent replacement occurs, and the liquid film falls off from the glass plate to obtain the diaphragm. The present invention has the performance characteristics of high porosity, uniform pore size, low resistance, good mechanical stability and long service life. The preparation is simple and reliable, reducing the use and maintenance costs of alkaline water electrolyzers.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by water electrolysis, and particularly relates to a biphasic continuous spongy porous structure electrolyzed water composite diaphragm and a preparation method thereof. Background Art

[0002] Fossil energy is a non-renewable energy source with decreasing reserves. As a high-energy clean energy, hydrogen energy has the advantages of recyclability and cleanliness. Therefore, the development of hydrogen energy is an effective way to reduce the consumption of fossil energy and promote the sustainable development of human society.

[0003] Hydrogen can be produced from various sources, including fossil fuels, biomass, and electrolysis of water. Among them, hydrogen production by electrolysis of water, as one of the technologies of renewable energy systems, provides a direct way to convert electrical energy into hydrogen energy. Currently, there are three types of electrolyzer systems for hydrogen production: alkaline water electrolyzers, proton exchange membrane electrolyzers, and solid oxide electrolyzers. Among them, hydrogen production by alkaline water electrolyzers is more commercialized compared to other hydrogen production methods by electrolysis of water due to its mature technology and low cost. However, there are still some aspects of this technology that need to be improved, such as maintenance costs and operating stability.

[0004] An alkaline electrolyzer mainly consists of a cell body, electrodes, and a diaphragm. Among them, the diaphragm plays a very important role in the alkaline electrolyzer. On the one hand, it must be able to prevent the mixing of hydrogen and oxygen to ensure the purity of hydrogen; on the other hand, it must allow ions in the solution to pass through to ensure the normal progress of the electrolysis process, and the diaphragm should preferably have a low resistance to reduce the energy consumption of the electrolyzer.

[0005] In the early stage of alkaline water electrolysis (AWE) research, asbestos was used as the diaphragm material for alkaline electrolyzers. However, its chemical properties are unstable under alkaline conditions, and toxic carcinogens will be produced during the hydrogen production process, so it has been internationally prohibited. Subsequently, it was found that polyphenylene sulfide (PPS) cloth has a better diaphragm effect and is non-toxic, so PPS cloth replaced asbestos cloth as the second-generation diaphragm. With the continuous progress of technology, a new generation of composite diaphragms with strong alkali resistance, high tensile strength, and excellent electrochemical properties, which have the advantages of both organic and inorganic diaphragms, have become a better choice for alkaline water electrolysis hydrogen production.

[0006] However, the surface of a general composite diaphragm is a dense layer, and it has a typical finger-like pore structure inside, making its resistance relatively large and its mechanical stability poor. Therefore, developing a composite diaphragm with high chemical and mechanical stability, high porosity and small pore diameter, as well as good gas barrier properties and wettability in a strongly alkaline medium has become an urgent technical problem to be solved in this technical field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a biphasic continuous sponge-like porous structure electrolyzed water composite diaphragm and a preparation method thereof, which have the performance characteristics of high porosity, uniform pore size, low resistance, good mechanical stability and long service life, and are simple and reliable to prepare, reducing the use and maintenance costs of alkaline water electrolyzers.

[0008] To solve the above technical problems, the present invention provides an electrolyzed water composite diaphragm composed of an alkali-resistant polymer and zirconia. The diaphragm surface has a porous layer and a biphasic continuous porous structure inside. The thickness is 100-500 μm, the porosity is 30-80%, the pore size is 50-100 nm, and the surface resistance is 0.030-0.100 Ω·cm 2 , and the tensile strength is 2-7 MPa.

[0009] Further, the diaphragm thickness is 200-300 μm; the porosity is 50-70%; the pore size is 50-100 nm; the surface resistance is 0.040-0.070 Ω·cm 2 ; the tensile strength is 3-5 MPa. The smaller the diaphragm thickness and the larger the porosity, the smaller its surface resistance, but the mechanical strength and toughness decrease; the larger the thickness and the smaller the porosity, its mechanical strength and toughness are better, but the surface resistance becomes larger. Therefore, the ultimate purpose of the above condition parameters is to obtain a composite diaphragm with excellent comprehensive performance and eliminate the short-board effect.

[0010] A preparation method of an electrolyzed water composite diaphragm includes the following steps:

[0011] A: Mix and stir an organic solvent and a diluent in proportion for 1-3 h to obtain a first mixed solution, wherein the mass ratio of the organic solvent to the diluent is 1:1 to 1:5;

[0012] B: Add an alkali-resistant polymer to the first mixed solution and stir for 24 h to obtain a second mixed solution, wherein, in the second mixed solution, the mass proportion of the alkali-resistant polymer is 0.1-0.3;

[0013] C: Add nano-zirconia particles to the second mixed solution obtained in step B and stir for 4-6 h. After degassing, a uniform milky white casting solution is obtained, wherein the mass ratio of zirconia to the alkali-resistant polymer is 0.5:1-3:1;

[0014] D: Place the casting solution obtained in step C on a clean glass plate and use a scraper to scrape the casting solution to prepare a liquid film;

[0015] E: Rapidly place the liquid film prepared in step D into the coagulation bath. The polymer and diluent in the liquid film first undergo thermally induced phase separation (because heat transfer is much faster than mass transfer), and then the organic solvent and diluent in the liquid film exchange with water to form a bicontinuous sponge-like porous structure. The liquid film detaches from the glass plate to obtain the separator.

[0016] Furthermore, the organic solvent in step A is one or more of N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide, and the diluent is one or more of diethylene glycol, polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400. The mass ratio of the organic solvent to the diluent is 1:1.7 - 1:2.5.

[0017] Furthermore, the alkali-resistant polymer in step B is one or more combinations of polysulfone, polyethersulfone, polyphenylsulfone, and poly(phenylene sulfone), and the mass ratio of the alkali-resistant polymer is 0.15 - 0.2.

[0018] Furthermore, the mass ratio of zirconia added in step C to the alkali-resistant polymer is 1:1 - 2:1.

[0019] Furthermore, the distance between the doctor blade and the glass plate in step D is 100 - 750 μm, preferably 200 - 500 μm.

[0020] Furthermore, the temperature of the coagulation bath in step E is 30 - 70 °C, and the coagulation bath time is 1 - 10 min.

[0021] Advantages of the present invention:

[0022] 1. The film-forming system consists of an alkali-resistant polymer, an organic solvent, and a diluent, and has a low critical solution temperature (LCST). Rapid thermally induced phase separation can be achieved by controlling the temperature of the coagulation bath, forming a porous layer on the surface of the membrane, rather than the surface dense layer obtained by traditional solvent phase separation; the pore size is small, and a symmetric bicontinuous sponge-like porous structure is formed throughout the cross-section of the membrane, thereby forming a composite separator with high chemical and mechanical stability, high porosity and small pore size, and good gas barrier property and wettability in a strong alkaline medium.

[0023] 2. In the present invention, the casting process is simple, the microporous structure of the separator is adjustable and controllable and easy to produce and prepare, with low cost and high efficiency.

[0024] 3. In the prepared composite separator for alkaline water electrolysis, the pore size structure can be regulated by the content ratio of the polymer and the diluent and the temperature of the coagulation bath, thereby forming a three-dimensional sponge-like porous structure, endowing the separator with excellent electrochemical properties and physical characteristics. Description of the Drawings

[0025] Figure 1 It is the preparation flow chart of the composite separator of the present invention;

[0026] Figure 2 It is the microscopic morphology diagram of the composite separator material prepared in Example 1 of the present invention;

[0027] Figure 3 It is the microscopic morphology diagram of the composite separator material prepared in Example 2 of the present invention;

[0028] Figure 4 It is the microscopic morphology diagram of the composite separator material prepared in Example 3 of the present invention;

[0029] Figure 5 It is the microscopic morphology diagram of the composite separator material prepared in Example 4 of the present invention;

[0030] Figure 6 It is the microscopic morphology diagram of the composite separator material prepared in Example 5 of the present invention;

[0031] Figure 7 It is the microscopic morphology diagram of the composite separator material prepared in Example 6 of the present invention;

[0032] Figure 8 It is the microscopic morphology diagram of the composite separator material prepared in Comparative Example 1 of the present invention;

[0033] Figure 9 It is the microscopic morphology diagram of the composite separator material prepared in Comparative Example 2 of the present invention;

[0034] Figure 10 It is the microscopic morphology diagram of the composite separator material prepared in Comparative Example 3 of the present invention;

[0035] Figure 11 It is the microscopic morphology diagram of the composite separator material prepared in Comparative Example 4 of the present invention. Detailed implementation manners

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited are not intended to limit the present invention.

[0037] An embodiment of the electrolyzed water composite diaphragm proposed by the present invention is composed of an alkali-resistant polymer and zirconium dioxide. The diaphragm surface has a porous layer, and the interior has a bicontinuous porous structure, which can also be called a bicontinuous three-dimensional sponge-like porous structure. The bicontinuous pores can be understood as having pores extending from the first side of the diaphragm towards the second side and pores extending from the second side of the diaphragm towards the first side. There are also through holes in the transverse direction between the pores, thus forming a three-dimensional sponge-like structure. The diaphragm thickness is 200 - 300 um; the porosity is 50 - 70%; the pore diameter is 50 - 100 nm; the surface resistance is 0.040 - 0.070 Ω·cm 2 ; the tensile strength is 3 - 5 MPa. The smaller the diaphragm thickness and the larger the porosity, the smaller its surface resistance, but the mechanical strength and toughness decrease; the larger the thickness and the smaller the porosity, its mechanical strength and toughness are better, but the surface resistance becomes larger. Therefore, the ultimate goal of the above condition parameters is to obtain a composite diaphragm with excellent comprehensive performance, so that it does not have a short board effect, and has the performance characteristics of high porosity, uniform pore diameter, low resistance, good mechanical stability and long service life, further reducing the use and maintenance costs of alkaline water electrolyzers.

[0038] The present invention also proposes a method for preparing a composite diaphragm using the reverse thermally induced phase separation method to form a bicontinuous (gas-solid) three-dimensional sponge-like porous structure that is the same inside and outside, which is specifically described in detail in the following cases:

[0039] Example 1

[0040] Prepare a polyethersulfone composite diaphragm material for alkaline water electrolysis, as shown in reference Figure 1 . (1) Weigh 50 g of N,N-dimethylacetamide (DMAc) solvent and place it in a beaker. Then weigh 75 g of PEG200 and add it to the beaker (the ratio is 1:1.5). After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 22.06 g of polyethersulfone (15%) and add it to the pre-mixed organic solution. After mechanical stirring for 24 h, a transparent and homogeneous polymer solution is obtained; (3) Weigh 22.06 g of zirconium dioxide particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h and degassing, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the doctor blade and the glass plate to 500 μm, and slowly and uniformly move the doctor blade to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to undergo phase separation and solvent exchange to obtain a composite diaphragm. Its surface and cross-sectional micro-morphology are as shown in Figure 2 . The performance test results are shown in Table 1.

[0041] Example 2

[0042] Preparation of a polyethersulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of the N,N-dimethylacetamide (DMAc) solvent and place it in a beaker. Subsequently, weigh 115 g of PEG200 (1:2.3) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 29.12 g of polyethersulfone (15%) and add it to the pre-mixed organic solution. After mechanical stirring for 24 h, a transparent and homogeneous polymer solution is obtained; (3) Weigh 29.12 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the blade and the glass plate to 500 μm, and slowly and uniformly move the blade to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to undergo phase separation and solvent exchange to obtain a composite diaphragm, the surface and cross-sectional micro-morphology of which is as Figure 3 shown, and the performance test results are shown in Table 1.

[0043] Example 3

[0044] Preparation of a polyethersulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of the N,N-dimethylacetamide (DMAc) solvent and place it in a beaker. Subsequently, weigh 75 g of PEG200 (1:1.5) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 25.6 g of polyethersulfone (17%) and add it to the pre-mixed organic solution. After mechanical stirring for 24 h, a transparent and homogeneous polymer solution is obtained; (3) Weigh 25.6 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the blade and the glass plate to 500 μm, and slowly and uniformly move the blade to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to undergo phase separation and solvent exchange to obtain a composite diaphragm, the surface and cross-sectional micro-morphology of which is as Figure 4 shown, and the performance test results are shown in Table 1.

[0045] Example 4

[0046] Preparation of polyethersulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of N,N-dimethylacetamide (DMAc) solvent into a beaker, and then weigh 115 g of PEG200 (1:2.3) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 33.8 g of polyethersulfone (17%) and add it to the pre-mixed organic solution. After mechanical stirring for 24 h, a transparent and homogeneous polymer solution is obtained; (3) Weigh 33.8 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the scraper and the glass plate to 500 μm, and slowly and uniformly move the scraper to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to cause phase separation and solvent exchange, and obtain a composite diaphragm. Its surface and cross-sectional micro-morphologies are as shown in Figure 5 shown, and the performance test results are shown in Table 1.

[0047] Example 5

[0048] Preparation of polyethersulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of N,N-dimethylacetamide (DMAC) solvent into a beaker, and then weigh 115 g of PEG200 (1:2.3) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 33.8 g of polyethersulfone (17%) and add it to the pre-mixed organic solution. After mechanical stirring for 24 h, a transparent and homogeneous polymer solution is obtained; (3) Weigh 33.8 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the scraper and the glass plate to 500 μm, and slowly and uniformly move the scraper to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 50 °C for a water bath for 5 min to cause phase separation and solvent exchange, and obtain a composite diaphragm. Its surface and cross-sectional micro-morphologies are as shown in Figure 6 shown, and the performance test results are shown in Table 1.

[0049] Example 6

[0050] Prepare a polyethersulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of N,N-dimethylacetamide (DMAc) solvent into a beaker, and then weigh 115 g of PEG200 (1:2.3) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 33.8 g (17%) of polyethersulfone and add it to the pre-mixed organic solution, and mechanically stir for 24 h to obtain a transparent and homogeneous polymer solution; (3) Weigh 33.8 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the scraper and the glass plate to 500 μm, and slowly and uniformly move the scraper to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 70 °C for a water bath for 5 min to undergo phase separation and solvent exchange to obtain a composite diaphragm, whose surface and cross-sectional micro-morphologies are as Figure 7 shown, and the results of its performance tests are shown in Table 1.

[0051] In the above-mentioned multiple embodiments, PEG200 is introduced as a non-solvent additive into the casting solution. As the amount of PEG200 increases, the interaction between polyethersulfone and the mixed solvent weakens, and a preformed liquid-phase PEG200 / polyethersulfone bicontinuous structure is formed by using temperature, laying the foundation for the eventual formation of a sponge-like porous structure. In addition, as the mass ratio of PEG200 / DMAc increases, the viscosity of the casting solution also increases, thereby affecting the solvent exchange rate between the casting solution and the coagulation bath, and finally effectively controlling the microporous structure of the diaphragm.

[0052] In addition, comparative experiments are carried out with other diluents, namely PEG300 and PEG400, as additives. Films are prepared under the conditions of organic solvent (NMP): diluent = 1:2.3, alkali-resistant polymer (PES) with a solid content of 17%, a coagulation bath (deionized water) at 50 °C, and a scraper gap of 500 μm (reference can be made to Example 5). Compared with the diaphragm prepared with PEG200, the overall performance is slightly reduced.

[0053] Comparative Example 1

[0054] Different from the examples, a polyethersulfone composite diaphragm material for alkaline water electrolysis was prepared without adding PEG200. (1) Weigh 100 g of N,N-dimethylacetamide (DMAc) solvent into a beaker, and then weigh 20.48 g (17%) of polyethersulfone and add it to the organic solution. Stir mechanically for 24 h to obtain a transparent and homogeneous polymer solution; (2) Weigh 20.48 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (3) Place the above casting solution on a clean glass plate, adjust the distance between the doctor blade and the glass plate to 500 μm, and slowly and uniformly move the doctor blade to make the casting solution spread and form a liquid film on the glass plate; (4) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to cause phase separation and solvent exchange, and obtain a composite diaphragm. The surface and cross-sectional microtopography are as shown in Figure 8 shown, and the performance test results are shown in Table 1.

[0055] Comparative Example 2

[0056] Different from the examples, polysulfone (PSU) was used as the alkali-resistant polymer to prepare a polysulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of N,N-dimethylacetamide (DMAc) solvent into a beaker, and then weigh 115 g of PEG200 (1:2.3) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous premixed organic solution is obtained; (2) Weigh 33.8 g (17%) of polysulfone and add it to the premixed organic solution. Stir mechanically for 24 h to obtain a transparent and homogeneous polymer solution; (3) Weigh 33.8 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the doctor blade and the glass plate to 500 μm, and slowly and uniformly move the doctor blade to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 70 °C for a water bath for 5 min to cause phase separation and solvent exchange, and obtain a composite diaphragm. The surface and cross-sectional microtopography are as shown in Figure 9 shown, and the performance test results are shown in Table 1.

[0057] Comparative Example 3

[0058] Different from the examples, N,N-dimethylformamide (DMF) was used as an organic solvent to prepare a polyethersulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 50 g of N,N-dimethylformamide (DMF) solvent into a beaker, and then weigh 115 g of PEG200 (1:2.3) and add it to the beaker. After mechanical stirring for 2 h, a transparent and homogeneous pre-mixed organic solution is obtained; (2) Weigh 33.8 g (17%) of polyethersulfone and add it to the pre-mixed organic solution, and mechanically stir for 24 h to obtain a transparent and homogeneous polymer solution; (3) Weigh 33.8 g of zirconia particles (1:1), and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (4) Place the above casting solution on a clean glass plate, adjust the distance between the blade and the glass plate to 500 μm, and slowly and uniformly move the blade to make the casting solution spread and form a liquid film on the glass plate; (5) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to cause phase separation and solvent exchange, and obtain a composite diaphragm. Its surface and cross-sectional micro-morphologies are as shown in Figure 10 shown, and the performance test results are shown in Table 1.

[0059] Comparative Example 4

[0060] Different from the examples, N-methylpyrrolidone (NMP) was used as an organic solvent, and polysulfone (PSU) was used as an alkali-resistant polymer to prepare a traditional polysulfone composite diaphragm material for alkaline water electrolysis. (1) Weigh 100 g of N-methylpyrrolidone (NMP) solvent into a beaker and stir it. Then weigh 18 g of polysulfone polymer and slowly add it to the organic solvent in batches while stirring. After mechanical stirring for 4 h, a transparent and homogeneous polysulfone solution is obtained; (2) Weigh 54 g of zirconia particles and slowly add them to the polymer solution in batches while stirring. After mechanical stirring for 4 h, a milky white and homogeneous casting solution is obtained; (3) Place the above casting solution on a clean glass plate, adjust the distance between the blade and the glass plate to 500 μm, and slowly and uniformly move the blade to make the casting solution spread and form a liquid film on the glass plate; (4) Quickly place the above liquid film in deionized water at 30 °C for a water bath for 5 min to cause phase separation and solvent exchange, and obtain a composite diaphragm. Its surface and cross-sectional micro-morphologies are as shown in Figure 11 shown, and the performance test results are shown in Table 1.

[0061] As can be seen from the attached drawings, the surfaces of Examples 1-3 exhibit a dense layer, while the cross-sections are all finger-like pore structures. The surfaces and cross-sections of Examples 4-6 both exhibit a three-dimensional network pore structure. This is because as the ratio of the organic solvent to the diluent increases, a more stable and uniform double-continuous structure is formed in the liquid phase, making it easier to form a three-dimensional network during phase separation. By comparing Example 2 and Example 4, it can be found that even though the ratio of the organic solvent to the diluent is the same, the difference in the polymer solid content also leads to the formation of different pore structures. This is because as the polymer solid content increases, the viscosity of the casting solution increases and the increase amplitude is relatively high. During phase separation, the resistance to solvent replacement increases and the rate decreases, resulting in the failure to form finger-like pores. By comparing the data in Table 1, it is found that although Examples 1-3 have a finger-like pore structure that is more conducive to transmission, they have higher surface resistance and bubble points. This is the result of the influence of the dense surface layer. On the other hand, by comparing Examples 4-6, it can be found that as the coagulation bath temperature increases, the pore structure becomes more porous, and thus the surface resistance and bubble points also decrease. Finally, the preferred examples are 4-6.

[0062] Table 1 shows the relevant preparation conditions and performance test results of the diaphragms in Examples 1-6 and Comparative Examples 1-4

[0063]

[0064]

[0065] The above-described examples are merely preferred examples given to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention.

Claims

1. A preparation method of an electrolyzed water composite diaphragm, characterized in that, The electrolyzed water composite diaphragm is composed of an alkali-resistant polymer and zirconia dioxide. The surface of the diaphragm has a porous layer, and the interior of the diaphragm has a bicontinuous porous structure. The thickness of the diaphragm is 100 - 500 μm, the porosity is 30 - 80%, the pore diameter is 50 - 100 nm, and the surface resistance is 0.030 - 0.100 Ω·cm 2 , including the following steps: A: Mix the organic solvent and the diluent in proportion and stir for 1 - 3 h to obtain the first mixed solution, where the mass ratio of the organic solvent to the diluent is 1:2.3; the organic solvent is N,N-dimethylacetamide and the diluent is polyethylene glycol 200; B: Add the alkali-resistant polymer to the first mixed solution and stir for 24 h to obtain the second mixed solution, where in the second mixed solution, the mass proportion of the alkali-resistant polymer is 0.1 - 0.3; the alkali-resistant polymer is polyethersulfone; C: Add the nano-zirconia particles to the second mixed solution prepared in step B and stir for 4 - 6 h, and after degassing, obtain a uniform milky white casting solution, where the mass ratio of zirconia to the alkali-resistant polymer is 1:1; D: Place the casting solution prepared in step C on a clean glass plate and use a scraper to scrape the casting solution to prepare a liquid film; E: Quickly place the liquid film prepared in step D into a coagulation bath. First, the polymer and the diluent in the liquid film undergo thermally induced phase separation, and then the organic solvent and the diluent in the liquid film exchange with water, and the liquid film falls off from the glass plate to obtain the separator.

2. The preparation method of the electrolyzed water composite diaphragm according to claim 1, characterized in that, The diaphragm has a thickness of 200-300 μm, a porosity of 50-70%, a pore size of 50-100 nm, and a surface resistance of 0.040-0.070 Ω·cm 2 .

3. According to the preparation method of the electrolyzed water composite separator described in claim 1, the distance between the scraper and the glass plate in step D is 100 - 750 μm.

4. According to the preparation method of the electrolyzed water composite separator described in claim 1, the temperature of the coagulation bath in step E is 30 - 70 °C, and the coagulation bath time is 1 - 10 min.

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