Composite separator for alkaline water electrolysis and method for producing and using the same

Abstract

The application provides a composite diaphragm for alkaline water electrolysis and a preparation method and application thereof, and the composite diaphragm for alkaline water electrolysis comprises a skin layer, a finger-shaped porous layer and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support body. The special heterostructure design of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer can not only obtain the diaphragm for alkaline water electrolysis with an ultra-high bubble point, but also the diaphragm has an extremely low surface resistance, hydrophilicity and ultra-fast wettability. The support body arranged in the three-dimensional porous layer can effectively enhance the mechanical strength of the diaphragm for alkaline water electrolysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alkaline water electrolysis, in particular to a composite diaphragm for alkaline water electrolysis and a preparation method and application thereof. BACKGROUND

[0002] Clean energy hydrogen energy has a wide application prospect as one of the important energy carriers in the future. Alkaline water electrolysis, as a mature green hydrogen production technology, has room for further reduction in energy consumption. Generally, an alkaline water electrolysis device includes an electrolytic tank, electrodes and a diaphragm. When powered on, hydrogen gas is generated on the cathode side and oxygen gas is generated on the anode side.

[0003] For a diaphragm for alkaline water electrolysis, it is required to have properties such as ion permeability, mechanical strength, gas tightness and electrical insulation. Among them, ion permeability directly affects the electrolysis efficiency of the alkaline water electrolysis tank using the diaphragm. Improving the ion permeability of the diaphragm can reduce the surface resistance of the diaphragm, thereby improving the electrolysis efficiency of the alkaline water electrolysis tank. Mechanical strength requires the diaphragm to have good mechanical strength so as to withstand the friction between the electrodes and the diaphragm of the electrolytic tank. Gas tightness requires the diaphragm to have the property of blocking gas, and the generated gas cannot permeate the diaphragm, that is, the diaphragm only allows ions to permeate. Electrical insulation means that the diaphragm cannot conduct electricity and needs to be in an insulating state.

[0004] The diaphragm for alkaline water electrolysis in the prior art is difficult to simultaneously consider the above four aspects of performance or needs to be further improved, and therefore the present application aims to provide a diaphragm for alkaline water electrolysis which simultaneously has excellent ion permeability, mechanical strength, gas tightness and electrical insulation. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a composite diaphragm for alkaline water electrolysis and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a composite diaphragm for alkaline water electrolysis, comprising a skin layer, a finger-shaped porous layer and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support.

[0007] According to the composite diaphragm for alkaline water electrolysis provided by the present application, the average pore diameters of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 30-50 nm, 300-500 nm and 100-200 nm, respectively.

[0008] According to the composite diaphragm for alkaline water electrolysis provided by the present application, the width of the finger-shaped pores of the finger-shaped porous layer is 2-10 μm.

[0009] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0010] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0011] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0012] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0013] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0014] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0015] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively.

[0016] The composite diaphragm for alkaline water electrolysis provided by the application has a skin layer, a finger-shaped porous layer and a three-dimensional porous layer, and the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively. 2 , and the bubble point is 18-25 bar.

[0017] In a second aspect, the application provides a preparation method of the composite diaphragm for alkaline water electrolysis.

[0018] The preparation method provided by the application comprises the following steps: mixing inorganic nano-particles, organic high-molecular polymers, a binder and a solvent to prepare a film casting solution;

[0019] The support is completely immersed in the film casting solution, the film casting solution on one side of the support is scraped flat, and a diaphragm in a wet state is prepared; the diaphragm is pre-evaporated, and then the diaphragm is soaked in a mixed solution of water and an organic solvent, a rapid phase inversion occurs on the surface through a phase inversion process, a dense skin layer structure is formed, a delayed phase separation occurs in the inside, a finger-shaped porous layer and a three-dimensional porous layer are gradually formed from the surface layer to the inside, and the composite diaphragm for alkaline water electrolysis is obtained.

[0020] In a third aspect, the present application provides use of the composite separator for alkaline water electrolysis in electrolysis of water.

[0021] The present application provides a composite separator for alkaline water electrolysis, a preparation method and application thereof, by adopting the special heterogeneous structure design of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer, the composite separator for alkaline water electrolysis with an ultra-high bubble point can be obtained, and the composite separator has an extremely low surface resistance, hydrophilicity and ultra-fast wettability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the structure of the prepared separator in the embodiment of the present application.

[0023] Figure 2 The figure is a scanning electron microscope image of the cross section of the prepared separator in the embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is described clearly and completely below. Obviously, the described embodiments are some embodiments of the present application, rather than 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 protection scope of the present application.

[0025] In the description of the present specification, the description of the terms “one embodiment”, “some embodiments”, “example”, “specific example” or “some examples” means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the embodiments of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0026] In a first aspect, the present application provides a composite separator for alkaline water electrolysis, comprising a skin layer, a finger-shaped porous layer and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support.

[0027] The present application adopts the special heterogeneous structure design of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer, so that the composite separator for alkaline water electrolysis with an ultra-high bubble point can be obtained, and the composite separator has an extremely low surface resistance, hydrophilicity and ultra-fast wettability. The support in the three-dimensional porous layer can effectively enhance the mechanical strength of the composite separator for alkaline water electrolysis.

[0028] In some embodiments of the present application, the support is horizontally embedded in the three-dimensional porous layer, and the area of the support is equal to the horizontal cross-sectional area of the three-dimensional porous layer.

[0029] In some embodiments of the present application, the average pore diameters of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 30-50 nm, 300-500 nm and 100-200 nm, respectively.

[0030] In some embodiments of the present application, the width of the finger-shaped pores of the finger-shaped porous layer is 2-10 μm, and is further preferably 2 μm.

[0031] The present application has found that, by setting the average pore diameters of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer and the width of the finger-shaped pores of the finger-shaped porous layer within the above ranges, the gas barrier property can be achieved without hindering the ion transmission.

[0032] In some embodiments of the present application, the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm, respectively.

[0033] The present application controls the thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer within the above ranges, thereby controlling the overall thickness of the composite separator within the range of about 400 μm, which is advantageous for reducing the resistance of the separator.

[0034] In some embodiments of the present application, the skin layer comprises, in mass fraction, 3-9 parts of inorganic nano-particles, 80-90 parts of organic polymer and 0.1-0.5 parts of binder.

[0035] In some embodiments of the present application, the finger-shaped porous layer and the three-dimensional porous layer each comprise, in mass fraction, 40-60 parts of inorganic nano-particles, 40-60 parts of organic polymer and 0.1-0.5 parts of binder.

[0036] It should be noted that, in specific embodiments, the compositions of the finger-shaped porous layer and the three-dimensional porous layer do not necessarily have to be completely the same, and each can be within the above ranges.

[0037] In some embodiments of the present application, the inorganic nano-particles are one or a combination of strontium titanate and barium titanate, and the size is 10-200 nm.

[0038] In the prior art, the inorganic nano-particles are generally selected from one or more of alumina, zirconia, silica and zinc oxide, and the present application selects one or a combination of strontium titanate and barium titanate, which has the advantage of longer stability.

[0039] In some embodiments of the present application, the organic polymer is one or more of polyether sulfone, polysulfone, polyether ether ketone, chitosan.

[0040] In some embodiments of the present application, the binder is one or more of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA).

[0041] In some embodiments of the present application, the support is one or more of PP mesh, PPS mesh, PP non-woven fabric, PPS non-woven fabric.

[0042] The PP mesh of the present application is a mesh woven from polypropylene fibers. The polypropylene fiber is a synthetic fiber spun from isotactic polypropylene obtained by polymerization of propylene. The polypropylene fiber has the characteristics of light weight, high strength, good elasticity, corrosion resistance, electrical insulation, etc.

[0043] The PPS mesh of the present application is a mesh woven from polyphenylene sulfide fibers. The polyphenylene sulfide fiber is made by melt spinning of polyphenylene sulfide. It is amber in color, with a strength of 0.18-0.26 N / tex, an elongation of 25-35%, and an initial modulus of 2.65-3.53 N / tex. It has good heat resistance and is mainly used as a high-temperature filter fabric, with a temperature resistance of up to 190°C. The fiber also has excellent resistance to chemicals and hydrolysis, as well as flame retardant properties.

[0044] In some embodiments of the present application, the fiber diameter of the support is 50-150 μm, and the pore size of the support is 100-400 μm.

[0045] Further, in some embodiments of the present application, the support is a mesh with a fiber diameter of 150 μm, and the pore size of the support is 400 μm.

[0046] The composite separator for alkaline water electrolysis provided by the present application has a surface resistance of 0.13-0.14 Ω·cm 2 , and a bubble point of 18-25 bar.

[0047] In a second aspect, the present application provides a preparation method of the above-mentioned composite separator for alkaline water electrolysis.

[0048] The preparation method provided by the present application comprises: mixing inorganic nanoparticles, organic polymer, binder and solvent to prepare a casting solution;

[0049] The support is completely immersed in the casting solution, the casting solution on one side of the support is scraped flat, and a wet-state diaphragm is prepared; the diaphragm is pre-evaporated, and then the diaphragm is immersed in a mixed solution of water and an organic solvent, rapid phase inversion occurs on the surface through a phase inversion process, a dense skin layer structure is formed, internal delayed phase separation occurs, and a finger-shaped porous layer and a three-dimensional porous layer are gradually formed from the surface layer to the inside, so that the composite diaphragm for alkaline water electrolysis is obtained.

[0050] The solvent is selected from one or more of dimethyl sulfoxide, N-methyl pyrrolidone, N,N-dimethylformamide, and acetonitrile.

[0051] In a third aspect, the present application provides a use of the composite diaphragm for alkaline water electrolysis in electrolysis of water.

[0052] For example, the present application provides an alkaline water electrolysis device comprising any of the composite diaphragms for alkaline water electrolysis.

[0053] The alkaline water electrolysis device generally comprises an electrolytic tank, electrodes, and a diaphragm, and hydrogen is generated on the cathode side and oxygen is generated on the anode side when electricity is applied. The alkaline water electrolysis device of the present application uses the composite diaphragm which simultaneously has ion permeability, mechanical strength, air tightness, and electrical insulation, so that the electrolysis efficiency of the alkaline water electrolysis device can be improved, the diaphragm can withstand the friction between the electrodes and the diaphragm of the electrolytic tank, the diaphragm has the property of blocking gas, the generated gas cannot permeate the diaphragm, and the diaphragm cannot conduct electricity, and is in an insulating state. In summary, it is safe and efficient.

[0054] The following are specific examples, and if no special instructions are given, the raw materials are obtained through a regular commercial channel.

[0055] Example 1

[0056] The present embodiment provides a composite diaphragm for alkaline water electrolysis, which is composed of a skin layer, a finger-shaped porous layer, and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support.

[0057] Specifically, the average pore diameters of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer are 30 nm, 300 nm, and 100 nm, respectively; and the width of the finger-shaped pores of the finger-shaped porous layer is 2 μm.

[0058] The thicknesses of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer are 3 μm, 200 μm, and 100 μm, respectively.

[0059] The support is a PP net, the diameter of the PP fibers is 150 μm, the pore diameter of the PP net is 400 μm, the support is horizontally embedded in the three-dimensional porous layer, and the area is equal to the horizontal cross-sectional area of the three-dimensional porous layer.

[0060] The skin layer contains 3 parts of inorganic nanoparticles (strontium titanate, particle size 100 nm), 90 parts of organic polymer (polyether sulfone), and 0.5 parts of binder (polyvinyl alcohol) by mass fraction;

[0061] The finger-shaped porous layer and the three-dimensional porous layer each contain 50 parts of inorganic nanoparticles (strontium titanate, particle size 100 nm), 50 parts of organic polymer (polyether sulfone), and 0.5 parts of binder (polyvinyl alcohol).

[0062] The preparation method is as follows:

[0063] S1, prepare the casting solution components: polyether sulfone (5% by mass fraction), strontium titanate (43% by mass fraction), polyvinyl alcohol (2% by mass fraction), and solvent (NMP, 50% by mass fraction);

[0064] S2, first mix and stir the casting solution components in S1 for 10 h, then completely immerse the support in the casting solution, and then use a flat blade to scrape the casting solution on one side of the support using a diaphragm manufacturing device (MSK-AFA-L1000 scraper, same below); a wet composite diaphragm is prepared; the gap between the scrapers is set to 400 microns;

[0065] S3, evaporate the above wet composite diaphragm for 10 min, and then place it in a phase inversion liquid for phase inversion; the phase inversion temperature is 20°C; the phase inversion liquid is a mixture of water and NMP (volume ratio 1:1); the phase inversion time is 10 s. Through the phase inversion process, the surface undergoes rapid phase inversion, forming a dense skin layer structure, and the inside undergoes delayed phase separation, gradually forming a finger-shaped porous layer and a three-dimensional porous layer from the surface to the inside, thereby forming a porous structure.

[0066] S4, after phase inversion, dry the membrane, cut and store it, and obtain the diaphragm.

[0067] The structure of the composite diaphragm obtained in this example is shown in Figure 1 The cross-sectional scanning electron microscope image is shown in Figure 2 .

[0068] Example 2

[0069] The composite diaphragm for alkaline water electrolysis provided in this example is composed of a skin layer, a finger-shaped porous layer, and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support.

[0070] Specifically, the average pore diameters of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer are 35 nm, 357 nm, and 140 nm, respectively; wherein the width of the finger-shaped pores of the finger-shaped porous layer is 2 microns;

[0071] The thicknesses of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer are 3 microns, 200 microns, and 100 microns, respectively;

[0072] The support is a PP net, the diameter of the PP fiber is 150 pm, the pore size of the PP net is 400 pm, and the support is horizontally embedded in the three-dimensional porous layer and has an area equal to the horizontal cross-sectional area of the three-dimensional porous layer.

[0073] The skin layer contains 9 parts of inorganic nanoparticles (barium titanate, particle size 200 nm), 80 parts of organic polymer (polysulfone), and 0.3 parts of binder (polyvinyl alcohol) by mass fraction;

[0074] The finger-shaped porous layer and the three-dimensional porous layer each contain 60 parts of inorganic nanoparticles (barium titanate, particle size 200 nm), 40 parts of organic polymer (polysulfone), and 0.5 parts of binder (polyvinyl alcohol).

[0075] The preparation method is as follows:

[0076] S1, prepare the casting solution components: polysulfone (5% by mass fraction), barium titanate (43% by mass fraction), polyvinyl alcohol (2% by mass fraction), and solvent (NMP, 50% by mass fraction);

[0077] S2, first mix and stir the casting solution components in S1 for 10 h, then completely immerse the support in the casting solution, and then use a flat blade to scrape the casting solution on one side of the support using a diaphragm manufacturing device (MSK-AFA-L1000 scraper, same below); a wet composite diaphragm is prepared; the gap between the scrapers is set to 400 microns;

[0078] S3, evaporate the above wet composite diaphragm for 10 min, then place it in a phase inversion liquid for phase inversion; the phase inversion temperature is 20°C; the phase inversion liquid is a mixture of water and NMP (volume ratio 1:1); the phase inversion time is 10 s. Through the phase inversion process, the surface undergoes rapid phase inversion, forming a dense skin layer structure, and the inside undergoes delayed phase separation, gradually forming a finger-shaped porous layer and a three-dimensional porous layer from the surface to the inside, thereby forming a porous structure.

[0079] S4, after phase inversion, dry the membrane of water, cut and store it, and obtain the diaphragm.

[0080] Example 3

[0081] The embodiment provides a composite diaphragm for alkaline water electrolysis, which is composed of a skin layer, a finger-shaped porous layer, and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support.

[0082] Specifically, the average pore diameters of the skin layer, the finger-shaped porous layer, and the three-dimensional porous layer are 40 nm, 300 nm, and 134 nm, respectively; wherein the width of the finger-shaped pores of the finger-shaped porous layer is 2 pm;

[0083] The thickness of the skin layer, the finger-like porous layer and the three-dimensional porous layer is 3 μm, 200 μm and 100 μm, respectively.

[0084] The support is a PP net, the diameter of the PP fiber is 150 μm, the pore size of the PP net is 400 μm, and the support is horizontally embedded in the three-dimensional porous layer with an area equal to the horizontal cross-sectional area of the three-dimensional porous layer.

[0085] The skin layer contains 6 parts of inorganic nanoparticles (strontium titanate, particle size 10 nm), 85 parts of organic polymer (polyether ether ketone) and 0.5 parts of adhesive (polyvinylpyrrolidone) by mass fraction;

[0086] The finger-like porous layer and the three-dimensional porous layer each contain 40 parts of inorganic nanoparticles (strontium titanate, particle size 10 nm), 60 parts of organic polymer (polyether ether ketone) and 0.5 parts of adhesive (polyvinylpyrrolidone).

[0087] The preparation method is as follows:

[0088] S1, prepare the casting solution components: polyether ether ketone (5% by mass fraction), strontium titanate (43% by mass fraction), polyvinylpyrrolidone (2% by mass fraction) and solvent (NMP, 50% by mass fraction);

[0089] S2, first mix and stir the casting solution components in S1 for 10 h, then completely immerse the support in the casting solution, and then use a flat blade to scrape the casting solution on one side of the support using a diaphragm manufacturing device (MSK-AFA-L1000 scraper, same below); a wet composite diaphragm is prepared; the gap between the scrapers is set to 400 microns;

[0090] S3, evaporate the above wet composite diaphragm for 10 min, then put it into a phase transfer liquid for phase transfer; the phase transfer temperature is 20°C; the phase transfer liquid is a mixture of water and NMP (volume ratio 1:1); the phase transfer time is 10 s. Through the phase transfer process, the surface undergoes rapid phase transfer, forming a dense skin layer structure, and the inside undergoes delayed phase separation, gradually forming a finger-like porous layer and a three-dimensional porous layer from the surface to the inside, thereby forming a porous structure.

[0091] S4, after phase transfer, dry the membrane, cut and store it to obtain a diaphragm.

[0092] Comparative Example 1

[0093] This comparative example provides a composite diaphragm for alkaline water electrolysis, which is PPS, purchased from TORAY company.

[0094] Comparative Example 2

[0095] The comparative example provides a composite separator for alkaline water electrolysis, which is ZIRFON PERL UTP 500, purchased from Agfa-Gevaert Company.

[0096] Comparative Example 3

[0097] The comparative example provides a composite separator for alkaline water electrolysis, which is prepared as follows:

[0098] S1, prepare the casting solution components: polyarylether sulfone (mass fraction 2%), nano zirconium oxide (particle size 20 nm, mass fraction 90%), N-methyl pyrrolidone (NMP, mass fraction 8%);

[0099] S2, first mix and stir the casting solution components in S1 for 40 h, then completely immerse the support in the casting solution, and then use a flat blade to scrape the casting solution on one side of the support using a separator manufacturing device; a wet composite separator is prepared; the gap between the blades is set to 500 microns;

[0100] The support of the present example uses a polypropylene fiber mesh with a fiber diameter of 30 microns and a mesh width of 800 microns, and the area of the support is consistent with the area of the separator;

[0101] S3, place the above-mentioned wet composite separator into a phase inversion liquid for phase inversion; the phase inversion temperature is 40°C; the phase inversion liquid is a mixture of water and NMP (volume ratio 1:1); the phase inversion time is 20 s. In this process, the organic high molecular resin in the casting solution coagulates, the solvent dissolves in water, and the high molecular resin and the solvent undergo phase separation, thereby forming a porous structure.

[0102] S4, after phase inversion, dry the membrane, cut and store it, and obtain the separator.

[0103] Performance test

[0104] (I) The performance of the composite separator sample was tested, and the results are shown in Table 1.

[0105] The test method of the surface resistance is as follows:

[0106] The separator was cut into small pieces, soaked in a 30wt% KOH solution for 1 day, and then the resistance was tested using an electrochemical workstation.

[0107] The test method of the bubble point is as follows:

[0108] The separator was cut into small pieces, soaked in high-purity water, and placed into a bubble point membrane pore size analyzer (BSD-PB) for testing; a gas pressure was applied to one side of the membrane, and when a gas flow of 1 mL / min was detected on the other side of the membrane, the pressure was taken as the bubble point of the separator. The calculation formula of the bubble point is as follows:

[0109]

[0110] In the formula, D = pore diameter, unit: μm; γ = surface tension of liquid, unit: dyn / cm; θ = contact angle, unit: degree; ΔP = pressure difference, unit: KPa.

[0111] The breaking strength is determined by a conventional test method in the art.

[0112] Table 1

[0113]

[0114] (II) The pore size of the diaphragm is evaluated, the thickness is tested, and the porosity is calculated, and the results are shown in Table 2.

[0115] Pore size evaluation: the average pore size of the film is tested by the bubble point method, and the wetting liquid is high-purity water;

[0116] Porosity calculation:

[0117] Porosity (%) = (wet film weight - dry film weight) / density of water / volume of wet film × 100.

[0118] Table 2

[0119] Sample Pore size (nm) Thickness (um) Porosity (%) Example 1 48 410 63 Example 2 44 395 61 Example 3 36 405 60 Comparative Example 1 140 518 60 Comparative Example 2 135 493 54 Comparative Example 3 69 505 56

[0120] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A composite diaphragm for alkaline water electrolysis, characterized in that: It comprises a skin layer, a finger-shaped porous layer and a three-dimensional porous layer connected in sequence; wherein the three-dimensional porous layer contains a support body; The average pore sizes of the skin layer, finger-shaped porous layer and three-dimensional porous layer are 30-50 nm, 300-500 nm and 100-200 nm respectively; and / or, the width of the finger-shaped pores of the finger-shaped porous layer is 2 to 10 μm; The fiber diameter of the support is 50-150 μm, and the pore size of the support is 100-400 μm; The thicknesses of the skin layer, the finger-shaped porous layer and the three-dimensional porous layer are 1-5 μm, 200-250 μm and 100-150 μm respectively; The skin layer comprises, by weight, 3-9 parts of inorganic nanoparticles, 80-90 parts of organic high molecular polymer, and 0.1-0.5 parts of a binder; And / or, the finger-shaped porous layer and the three-dimensional porous layer each contain 40-60 parts of inorganic nanoparticles, 40-60 parts of organic high molecular polymer and 0.1-0.5 parts of binder; The inorganic nanoparticles are one or a combination of strontium titanate and barium titanate; and the size is 10-200 nm.

2. The composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that The organic high molecular polymer is one or more of polyethersulfone, polysulfone, polyetheretherketone and chitosan.

3. The composite diaphragm for alkaline water electrolysis according to claim 1, characterized in that The support body is one or more of PP net, PPS net, PP non-woven fabric, and PPS non-woven fabric.

4. The composite diaphragm for alkaline water electrolysis according to claim 1 or 2, characterized in that: The surface resistance of the composite diaphragm is 0.13-0.14Ω.cm 2 , the bubble point is 18-25bar.

5. The method for preparing the composite diaphragm for alkaline water electrolysis according to any one of claims 1 to 4, characterized in that: include: Mixing inorganic nanoparticles, organic high molecular polymer, binder and solvent to prepare a casting solution; The support body is completely immersed in the casting liquid, and the casting liquid on one side of the support body is scraped flat to prepare a wet membrane; the membrane is pre-evaporated, and then the membrane is immersed in a mixed solution of water and an organic solvent. Through a phase transformation process, a rapid phase transformation occurs on the surface to form a dense cortical structure, and delayed phase separation occurs inside, gradually forming a finger-shaped porous layer and a three-dimensional porous layer from the surface to the inside, thereby obtaining the composite membrane for alkaline water electrolysis.

6. Use of the composite diaphragm for alkaline water electrolysis according to any one of claims 1 to 4 in electrolyzed water.

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