Composite diaphragm, and preparation method therefor and use thereof

Abstract

The present application relates to a composite diaphragm, and a preparation method therefor and the use thereof. The composite diaphragm comprises a three-dimensional porous support layer and a membrane material, wherein pores of the three-dimensional porous support layer are filled with the membrane material; the three-dimensional porous support layer comprises fiber filaments and / or a fiber cloth, and the fiber filaments and / or fiber filaments constituting the fiber cloth are hydrophilic fiber filaments and / or roughened fiber filaments. The composite diaphragm forms an elastic collapse-resistant support framework by means of multi-layer stacking, interweaving and winding of the fiber filaments, which improves the compression strength of the diaphragm; the treated fiber filaments can increase their contact with a casting solution, and the casting solution and the fiber network are interactively filled, which increases the contact volume between a liquid membrane and a phase separation non-solvent and delays the phase separation process during solidification so as to form a uniform sponge microporous dense structure, such that the formation of large finger-shaped through holes is inhibited, thereby facilitating the blocking of gas passage and improvement to the chemical stability. The casting solution is uniformly distributed in the fiber framework, and the membrane material is firmly anchored by the three-dimensional fiber network after solidification, such that the mechanical stability of the diaphragm is improved.

Description

Composite diaphragm and preparation method and application thereof TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of hydrogen production from alkaline electrolyte water, and particularly relates to a composite diaphragm for hydrogen production from alkaline electrolyte water and a preparation method thereof. BACKGROUND

[0002] Alkaline water electrolysis hydrogen production technology has high maturity and cost advantage, and has become the mainstream of industrial electrolytic hydrogen production. The diaphragm is a key material in the electrolytic tank, which separates the positive and negative electrode chambers, and provides a path for ion migration across the membrane in the electrolyte.

[0003] The composite diaphragm is one of the recognized upgrading and development directions of alkaline water electrolysis diaphragm materials in the industry, which is commonly coated with a blend of polymer and hydrophilic ceramic powder on both sides of the support wire mesh to form a membrane layer-wire mesh support layer-membrane layer sandwich structure. By controlling the pore structure and the intrinsic hydrophilicity of the ceramic powder through the film forming process, lower resistance is obtained, thereby reducing the electrolysis energy consumption. The composite diaphragm is thinner than the conventional PPS diaphragm, and the upper and lower membrane layers have poor folding, scratching and extrusion resistance, so the storage, handling, cutting and installation processes are relatively strict. Domestic alkaline water electrolytic tanks commonly use metal pole frame, four-fluorine sealing gasket and nickel-based metal mesh electrolysis, and the overall structure is relatively hard. Due to the processing tolerance, deformation, warping of these structural parts and the fact that the tank structure design does not adjust the compression amount and sealing method for the characteristics of the composite diaphragm, the compatibility of the composite diaphragm is poor. During the cutting or assembly process, it is easy to cause excessive folding angle cracking, scratching and membrane layer peeling due to careless operation, and excessive extrusion during the assembly and fastening process due to the incompatibility of the tank structure, which causes irreversible mechanical damage. This damage area not only increases the risk of gas leakage, but also causes local current concentration during long-term operation of the electrolytic tank, which accelerates the occurrence of phenomena such as overheating, alkali imbalance and cavitation, thereby causing continuous peeling and corrosion of the membrane layer and failure.

[0004] Therefore, on the basis of low resistance and strong gas separation performance, a robust composite diaphragm with high mechanical strength and stable membrane layer is developed, which is beneficial to the installation and use of domestic metal tank body, thereby improving the stability of the diaphragm and increasing the safety of hydrogen production.

[0005] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art.

[0006] SUMMARY

[0007] In order to solve the above problems, the present disclosure provides a composite diaphragm and a preparation method and application thereof.

[0008] The composite diaphragm of the present disclosure comprises a three-dimensional porous support layer and a film material, the pores of the three-dimensional porous support layer being filled with the film material; the three-dimensional porous support layer comprises fiber filaments and / or fiber cloth, the fiber filaments and / or the fiber filaments constituting the fiber cloth being hydrophilic fiber filaments and / or roughened fiber filaments.

[0009] According to an embodiment of the present disclosure, the hydrophilic fiber filaments are one or more of zirconium oxide fiber, zirconium silicate fiber, intrinsic hydrophilic modified fiber filaments and surface hydrophilic functional group modified fiber filaments; and the roughened fiber filaments are porous fiber filaments.

[0010] According to another embodiment of the present disclosure, the intrinsic hydrophilic modified fiber filaments comprise a fiber raw material and a hydrophilic agent, the hydrophilic agent being one or more of ZrO2, CeO2, SiO2, Al2O3, TiO2, BaSO4, BaCeO4, polyvinyl butyral ester (PVB), polyvinyl pyrrolidone (PVP); and / or the hydrophilic functional group comprises one or more of amino, sulfonic acid group, carboxyl, carbonyl, hydroxyl; and / or the porosity of the porous fiber filaments is 10-60%; and / or the fiber raw material is any one of PP, PES, PSU, PPS, PEEK, nylon fiber.

[0011] According to another embodiment of the present disclosure, the linear density of the fiber filaments is 0.3D-7D or the density is 2-6g / cm 3 ; the diameter of the fiber filaments is 10-150μm; the length of the fiber filaments is 30μm-7cm; and the basis weight of the fiber cloth is 30-500g / m2.

[0012] According to another embodiment of the present disclosure, the addition amount of the hydrophilic fiber filaments and / or the roughened fiber filaments is 30% or less of the total mass of the film material, preferably 2%-20%.

[0013] According to another embodiment of the present disclosure, the fiber cloth is any one of fiber-bonded cloth, needle-punched felt, non-woven cloth, and velvet cloth.

[0014] According to another embodiment of the present disclosure, the film material comprises hydrophilic inorganic powder, additives and polymer adhesive, the mass ratio of the hydrophilic inorganic powder to the polymer adhesive being 2:1-10:1, and the mass ratio of the additives to the polymer adhesive being 1:20-1:2.

[0015] According to another embodiment of the present disclosure, the hydrophilic inorganic powder comprises one or more of titanium dioxide, zirconium dioxide, cerium dioxide, barium sulfate, calcium sulfate, barium titanate, calcium titanate, and has a particle size distribution of 0.1-20 μm; and / or the polymer binder is one or more of polyether sulfone, polyaryl sulfone, polyphenylene sulfone, bisphenol A polysulfone, sulfonated polyether sulfone, sulfonated polyaryl sulfone, and sulfonated polyphenylene sulfide; and / or the additive comprises one or more of polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), polypropylene glycol and ethylene oxide adduct (F127), polybenzimidazole (PBI), ammonium carbonate, and ammonium bicarbonate.

[0016] According to another embodiment of the present disclosure, the composite separator further comprises a wire mesh substrate; preferably, the wire mesh substrate is a wire mesh woven from polypropylene (PP), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), or a nylon material; more preferably, the wire mesh has a mesh count of 20-150 and a thickness of 30-350 μm.

[0017] According to another embodiment of the present disclosure, the composite separator has a thickness of 150-900 μm; and / or an average pore size of 35-150 nm; and / or a tensile strength of 15-30 MPa; and / or a film layer peeling strength of ≥500 N / m; and / or a wear rate of ≤2% after 1000 times of repeated friction under a load of 500 g; and / or a weight loss of ≤1.5% after 24 h of boiling in a 30 wt.% potassium hydroxide solution at 120°C.

[0018] A method for preparing the composite separator of the present disclosure, comprising: providing a casting solution comprising a film material, an organic solvent, and optionally a fiber; coating the casting solution onto a fiber cloth so that the casting solution fills the pores of the fiber cloth to form a first liquid film layer; or coating the casting solution containing the fiber onto a substrate surface to form a second liquid film layer; pre-solidifying the first liquid film layer or the second liquid film layer in air or a coagulation bath, followed by rolling, and then placing in a coagulation bath for solidification to remove the remaining organic solvent to form the composite separator.

[0019] wherein the overall thickness is reduced by 0-40% before and after rolling, and the solvent is reduced by 70-99.8% after pre-solidification. The rolling can be any one of single-roller rolling, double-roller rolling, or multi-roller rolling.

[0020] wherein the fiber or the fiber constituting the fiber cloth is a hydrophilic fiber and / or a roughened fiber; and the coating step is performed at a pressure of normal pressure to -100 kPa (gauge pressure).

[0021] According to another embodiment of the present disclosure, the intrinsic hydrophilic modified fiber is obtained by adding a hydrophilic agent, mixing, granulating and melt spinning, the hydrophilic agent is one or more of ZrO2, CeO2, SiO2, Al2O3, TiO2, BaSO4, BaCeO4, polyvinyl butyral ester (PVB), polyvinyl pyrrolidone (PVP); the hydrophilic functional group includes one or more of amino, sulfonic acid group, carboxyl, carbonyl, hydroxyl; the roughened fiber is obtained by adding a pore-forming agent, mixing, granulating and melt spinning, and then pore-forming, the pore-forming agent is any one of KOH, NaOH, K2SO4, Na2SO4, K2CO3, Na2CO3, KHCO3, NaHCO3, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polypropylene glycol and ethylene oxide adduct powder, and the pore-forming process is to remove the pore-forming agent by washing the original fiber obtained by spinning in multiple stages.

[0022] According to another embodiment of the present disclosure, the number of multiple-stage washing is ≥3 times, the pH value of the aqueous solution used in the first-stage washing is ≤8, the first-stage washing solution is a mixture of an acidic solution and an organic solvent, the acidic solution is an aqueous solution of any one of H2SO4, HNO3, HCl, HCOOH, H2C2O4, and the organic solvent is any one of ethanol, isopropanol, n-butanol; the volume of the acidic solution in the first-stage washing solution is 3-10 parts, and the volume of the organic solvent is 1-3 parts; the last-stage washing solution is pure water.

[0023] According to another embodiment of the present disclosure, the mass ratio of the hydrophilic additive or the pore-forming agent to the intrinsic fiber is 1:30-10:1.

[0024] According to another embodiment of the present disclosure, the temperature of the air pre-solidification is 10-150 degrees, the time is 0-30 min, and the humidity is 20-90% RH; the non-solvent of the coagulation bath is water or a mixed solvent of water and one of dimethyl sulfoxide, N-methyl pyrrolidone, N-ethyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, the temperature of the coagulation bath is 5-80 degrees, and the coagulation bath time is 2 min-2 h.

[0025] The application of the composite separator of the present disclosure in the production of hydrogen from alkaline electrolyte water.

[0026] The composite separator of the present disclosure will form an elastic collapse-resistant support bridge through multi-layer accumulation and interwoven winding of fiber filaments, thereby improving the extrusion resistance of the separator. The treated fiber filaments can increase their contact with the casting solution, and the casting solution and the fiber grid interact to fill, thereby increasing the contact volume of the liquid film and the phase separation non-solvent, and increasing the delay phase separation process to form a uniform sponge microporous structure when solidified into a film, thereby inhibiting the formation of finger-shaped large through holes, thereby facilitating the blocking of gas crossing and improving chemical stability. The casting solution is uniformly distributed in the fiber bridge, and after solidification into a film, the film material is firmly targeted by the three-dimensional fiber, thereby improving the mechanical stability of the separator. At the same time, an additional rolling step is added in the preparation process, which can further improve the density and mechanical strength of the film layer. The composite separator of the present disclosure has a film layer peeling strength of ≥500 N / m; under a 500 g load, the wear rate is ≤2% after 1000 times of repeated friction; and the weight loss is ≤1.5% after alkali boiling at 120°C for 24 h in a 30 wt.% potassium hydroxide solution. BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a schematic cross-sectional view of a composite separator according to an embodiment of the present disclosure.

[0028] FIG. 2 is a cross-sectional scanning electron microscope image of a composite separator prepared in Example 2.

[0029] FIG. 3 is a graph of the relationship between the electrolysis current and the voltage of the composite separators prepared in Examples 1-10 and Comparative Example 1.

[0030] In the drawings, the reference signs are explained as follows: 10 - three-dimensional porous support layer; 11 - fiber filament; 20 - film material; 21 - hydrophilic inorganic powder DETAILED DESCRIPTION

[0031] The present disclosure will be described in detail below with reference to specific embodiments.

[0032] As shown in FIG. 1, the composite separator according to an embodiment of the present disclosure includes a three-dimensional porous support layer 10 and a film material 20, and the pores of the three-dimensional porous support layer 10 are filled with the film material 20; the three-dimensional porous support layer 10 includes fiber filaments and / or fiber cloth, and the fiber filaments and / or the fiber filaments that make up the fiber cloth are hydrophilic fiber filaments and / or roughened fiber filaments.

[0033] In the present patent, "fiber filaments" appearing alone refer only to free fiber filaments and do not include fiber filaments in fiber cloth. When referring to fiber filaments in fiber cloth, "fiber filaments that make up the fiber cloth", "fiber filaments of the fiber cloth", and the like are used. "Hydrophilic fiber filaments" and "roughened fiber filaments" can be free fiber filaments or fiber filaments that make up fiber cloth.

[0034] In an alternative embodiment, the hydrophilic fiber yarns can be one or more of zirconium oxide fiber, zirconium silicate fiber, intrinsically hydrophilic modified fiber yarns and surface hydrophilic functional group modified fiber yarns. The intrinsically hydrophilic modified fiber yarns include a fiber raw material and a hydrophilic agent, the hydrophilic agent being one or more of ZrO2, CeO2, SiO2, Al2O3, TiO2, BaSO4, BaCeO4, polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP). The intrinsically hydrophilic modified fiber yarns can be obtained by adding the hydrophilic agent, mixing and granulating and melt spinning after the addition.

[0035] In an alternative embodiment, the hydrophilic functional groups include one or more of amino, sulfonic acid group, carboxyl, carbonyl, hydroxyl. The above hydrophilic functional groups can be connected to the surface of the fiber yarns by any appropriate modification method to form the surface hydrophilic functional group modified fiber yarns.

[0036] In an alternative embodiment, the roughened fiber yarns can be porous fiber yarns. The porosity of the porous fiber yarns is 10% to 60%.

[0037] In an alternative embodiment, the linear density of the fiber yarns 11 forming the three-dimensional porous support layer 10 is 0.3D to 7D or the density is 2 to 6 g / cm 3 ; the fiber yarn diameter is 10 to 150 μm; the fiber yarn length is 30 μm to 7 cm; the fiber cloth basis weight is 30 to 500 g / m 2 .

[0038] In an alternative embodiment, the addition amount of the hydrophilic fiber yarns and / or the roughened fiber yarns in the composite separator is 30% or less of the total mass of the membrane material 20. Preferably, it is 2% to 20%.

[0039] In an alternative embodiment, the fiber cloth can include the hydrophilic fiber yarns and / or the roughened fiber yarns. Of course, it can also be composed of unmodified fiber yarns. The fiber cloth can be any one of fiber bonded cloth, needle punched felt, non-woven fabric, and fleece.

[0040] In an alternative embodiment, the membrane material 20 includes the hydrophilic inorganic powder 21, the additive and the polymer binder, the mass ratio of the hydrophilic inorganic powder 21 to the polymer binder being 2: 1 to 10: 1, and the mass ratio of the additive to the polymer binder being 1:20 to 1:2.

[0041] In an optional embodiment, the hydrophilic inorganic powder 21 comprises one or more of titanium dioxide, zirconium dioxide, cerium dioxide, barium sulfate, calcium sulfate, barium titanate, calcium titanate. The hydrophilic inorganic powder 21 has a particle size distribution of 0.1-20 pm. The polymeric binder can be one or more of polyether sulfone, polyaryl sulfone, polyphenylene sulfone, bisphenol A polysulfone, sulfonated polyether sulfone, sulfonated polyaryl sulfone, sulfonated polyphenylene sulfide; and / or the additive comprises one or more of polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123), polypropylene glycol adduct with ethylene oxide (F127), polybenzimidazole (PBI), ammonium carbonate, ammonium bicarbonate.

[0042] In an optional embodiment, the composite separator can further comprise a wire mesh substrate. The wire mesh substrate can be a wire mesh woven from polypropylene (PP), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), nylon material.

[0043] In an optional embodiment, the composite separator has a thickness of 150-900 pm. The composite separator has an average pore size of 35-150 nm. The composite separator has a tensile strength of 15-30 MPa. The composite separator has a film layer peeling strength of ≥500 N / m. The composite separator has a wear rate of ≤2% after repeated friction for 1000 times under a load of 500 g. The composite separator has a weight loss of ≤1.5% after alkali boiling in a 30 wt.% potassium hydroxide solution at 120 °C for 24 h.

[0044] The method for preparing the composite separator of the present disclosure can comprise two ways. In the first way, the method comprises: providing a casting solution, the casting solution comprising the membrane material 20, an organic solvent, and optionally the fiber yarn 11; coating the casting solution onto a fiber cloth, so that the casting solution fills the pores of the fiber cloth to form a first liquid membrane layer; pre-solidifying the first liquid membrane layer in air or a coagulation bath, then rolling, and then placing in a coagulation bath to solidify and remove the remaining organic solvent to form the composite separator. In this method, the casting solution can or can not comprise the fiber yarn 11. When the composite separator comprises the fiber yarn, the fiber yarn 11 and the fiber cloth together form the three-dimensional porous support layer of the composite separator. When the casting solution does not comprise the fiber yarn, the fiber cloth is the three-dimensional porous support layer of the composite separator. The coating process can be at a pressure of normal pressure to -100 kPa (gauge pressure).

[0045] In the second method, the preparation method can include: providing a casting solution, the casting solution including the membrane material 20, an organic solvent, and the fiber filaments 11; applying the casting solution containing the fiber filaments 11 on the surface of the substrate to form a second liquid film layer; pre-solidifying the second liquid film layer in air or a coagulation bath, then rolling, and then placing in a coagulation bath to solidify and remove the remaining organic solvent to form the composite separator. In the method for preparing the composite separator, the three-dimensional porous support layer in the composite separator is formed by stacking the fiber filaments.

[0046] The fiber filaments used in the above two methods can be hydrophilic fiber filaments and / or roughened fiber filaments. The fiber cloth can be composed of hydrophilic fiber filaments and / or roughened fiber filaments. Of course, the fiber cloth can also be composed of unmodified fiber filaments.

[0047] In the above two methods, the overall thickness is reduced by 0-40% before and after rolling. The solvent is reduced by 70-99.8% after pre-solidification. The rolling can use any one of single-roller rolling, double-roller rolling, and multi-roller rolling.

[0048] The composite separator formed by the above two methods has a three-dimensional support fiber uniformly filled in the membrane layer, an elastic and collapse-resistant support bridge formed by the multi-layer stacking and interweaving of the fiber, and improved extrusion resistance of the separator. After treatment, the fiber (hydrophilic modification and / or roughening modification) can increase its contact with the casting solution, the casting solution and the fiber grid interact with each other, the contact volume of the liquid film and the phase separation non-solvent is increased, the uniform sponge microporous structure is formed during solidification and film formation, the formation of finger-shaped large through holes is inhibited, thereby facilitating the blocking of gas penetration and improving the chemical stability. The casting solution is uniformly distributed in the fiber bridge, and the membrane material is firmly targeted by the three-dimensional fiber after solidification and film formation, thereby improving the mechanical stability of the separator. By adding a rolling step in the preparation process, the density and mechanical strength of the separator can be further improved.

[0049] The hydrophilic fiber filaments in the above two methods can be one or more of zirconium oxide fiber, zirconium silicate fiber, intrinsic hydrophilic modified fiber filaments, and surface hydrophilic functional group modified fiber filaments. The roughened fiber filaments can be porous fiber filaments.

[0050] In an optional embodiment, the intrinsic hydrophilic modified fiber filaments are obtained by adding a hydrophilic agent, mixing, granulating, and melt spinning. The hydrophilic agent can be one or more of ZrO2, CeO2, SiO2, Al2O3, TiO2, BaSO4, BaCeO4, polyvinyl butyral ester (PVB), and polyvinyl pyrrolidone (PVP). The mass ratio of the hydrophilic additive to the intrinsic fiber can be 1:30-10:1.

[0051] In optional embodiments, the hydrophilic functional groups include one or more of amino, sulfonic acid, carboxyl, carbonyl, hydroxyl. The above hydrophilic functional groups can be attached to the surface of the fiber filaments 11 in any suitable manner.

[0052] In optional embodiments, the roughened fiber filaments can be obtained by adding a pore-forming agent to the melt-spun pellets, or by removing the pore-forming agent after the pores are formed. The pore-forming agent can be any one of KOH, NaOH, K2SO4, Na2SO4, K2CO3, Na2CO3, KHCO3, NaHCO3, P123, F127 powder. The pore-forming process can be performed by washing the as-spun fiber filaments in multiple stages to remove the pore-forming agent. The number of multiple washing stages can be ≥ 3. The pH of the aqueous solution used in the first washing stage can be ≤ 8. The first washing solution can be a mixture of an acidic solution and an organic solvent. The acidic solution can be any one of H2SO4, HNO3, HCl, HCOOH, H2C2O4 aqueous solution. The organic solvent can be any one of ethanol, isopropanol, n-butanol. The volume of the acidic solution in the first washing solution can be 3-10 parts, and the volume of the organic solvent can be 1-3 parts. The final washing solution can be pure water. The mass ratio of the pore-forming agent to the intrinsic fiber can be 1:30-10:1.

[0053] In optional embodiments, the linear density of the fiber filaments 11 used in the above two methods can be 0.3D-7D or the density can be 2-6 g / cm 3 . The fiber filament diameter can be 10-150 μm. The fiber filament length can be 30 μm-7 cm. The fabric basis weight can be 30-500 g / m 2 .

[0054] In optional embodiments, the amount of the hydrophilic fiber filaments and / or the roughened fiber filaments added in the preparation method can be ≤ 30% of the total mass of the membrane material 20, that is, the amount of the fiber filaments 11 can be 0 when a fiber fabric is used. In this case, the fiber fabric includes the hydrophilic fiber filaments and / or the roughened fiber filaments. The amount of the organic solvent added in the casting solution can be 30%-70% of the total mass of the casting solution.

[0055] In optional embodiments, the membrane material 20 includes the hydrophilic inorganic powder 21, the additive, and the polymer binder. Preferably, the mass ratio of the hydrophilic inorganic powder 21 to the polymer binder can be 2:1-10:1, and the mass ratio of the additive to the polymer binder can be 1:20-1:2. The hydrophilic inorganic powder includes one or more of titanium dioxide, zirconium dioxide, cerium dioxide, barium sulfate, calcium sulfate, barium titanate, calcium titanate. The powder particle size distribution can be 0.1-20 μm.

[0056] In optional embodiments, the polymer binder can be one or two of polyether sulfone, polyaryl sulfone, polyphenylene sulfone, bisphenol A polysulfone, sulfonated polyether sulfone, sulfonated polyaryl sulfone, and sulfonated polyphenylene sulfide. The additive can include any one or two of PVB, PVP, P123, F127, PBI, ammonium carbonate, and ammonium bicarbonate.

[0057] In optional embodiments, the organic solvent, the polymer binder, the hydrophilic inorganic powder, the additive, and the optional fiber filament 11 can be mixed into a uniform casting solution. The order of addition can be arbitrary as long as a uniform slurry is formed. For example, but not limited to, a certain amount of the polymer binder is added into the organic solvent, the additive is dispersed uniformly, and then a certain amount of the hydrophilic inorganic powder and the fiber filament 11 are added. The mixing method can be arbitrary, such as ultrasonic dispersion, stirring dispersion, and grinding dispersion, but is not limited thereto.

[0058] Next, the casting solution is coated onto a fiber cloth or a substrate to form a first liquid film layer or a second liquid film layer, respectively. The fiber cloth can be any one of a fiber bonded cloth, a needle felt, a non-woven fabric, and a velvet cloth. The substrate can be any appropriate substrate, such as, but not limited to, a glass substrate.

[0059] In optional embodiments, the composite separator can further include a screen substrate. That is, the screen substrate and the fiber cloth can be used simultaneously, or only the screen substrate can be used without the fiber cloth. When the fiber cloth is not used, the three-dimensional porous support layer is formed by the screen substrate and the fiber filament 11. When the screen substrate and the fiber cloth are used simultaneously, the three-dimensional porous support layer is formed by the screen substrate, the fiber cloth, and the optional fiber filament 11. The screen substrate can be a screen woven from PP, PPS, PTFE, PEEK, or nylon material. The screen mesh can be 20-150 mesh, and the thickness can be 30-350 μm.

[0060] In optional embodiments, the coating method in the above two methods can be any one of spraying, silk-screen coating, blade coating, roll coating, and dip coating. The coating can also be performed under negative pressure. The negative pressure is located on the side of the screen or the fiber cloth, and the negative pressure range is between normal pressure and -100 kPa.

[0061] In an optional embodiment, the first liquid film layer or the second liquid film layer can be pre-cured in air at a temperature of 10-150 degrees, for a time of 0-30 min, and in a humidity of 20-90% RH. The pre-curing time in air can be selected according to specific needs, such as but not limited to no pre-curing, i.e. the pre-curing time can be 0 min, 1 min, 3 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc. After pre-curing, the non-solvent used in the coagulation bath can be water or a mixture of water and one of dimethyl sulfoxide, N-methyl pyrrolidone, N-ethyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide. The coagulation bath temperature can be 5-80 degrees, and the coagulation bath time can be 2 min-2 h. The coagulation bath temperature and time can be appropriately selected according to needs, such as but not limited to, the coagulation bath temperature is 5 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, etc., and the coagulation time is 2 min, 10 min, 20 min, 30 min, 50 min, 1 h, 1.5 h, 2 h, etc.

[0062] The composite separator prepared by the above method can have a thickness of 150-900 pm. The film layer peeling strength is ≥500 N / m; the wear rate is ≤2% after repeated friction for 1000 times under a load of 500 g. The weight loss after alkali boiling at 120°C for 24 h in a 30 wt.% potassium hydroxide solution is ≤1.5%. The composite separator of the present disclosure can have both low resistance and strong air barrier performance, and the composite separator is a robust composite separator with high mechanical strength and stable film layer, which is conducive to the installation and use with domestic metal tank bodies, thereby improving the stability of the separator and increasing the safety of hydrogen production.

[0063] The present disclosure is further described below by specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present disclosure. In the following examples and comparative examples, the reagents, materials and instruments used are commercially available unless otherwise specified. The negative pressure in the following examples refers to the gauge pressure.

[0064] Example 1

[0065] Take 10 g of zirconium oxide and 30 g of PES mixed granulation, then melt spinning into fibers, the fiber diameter is 20 μm, the length is 0.5 mm, the first water washing solution is a mixed solution of 90% HCOOH and 10% isopropyl alcohol, then washed with deionized water for 4 times, and after drying, the finally obtained hydrophilic modified fiber silk is ready for use. Take 85 g of N,N-dimethylformamide, add 50 g of zirconium oxide powder (average particle size 100 nm) and 3 g of hydrophilic modified fiber silk, ultrasonic dispersion uniformly, then add 10 g of polysulfone solid, 2 g of P123 and 2 g of PVP, stirring and dissolving to obtain a uniform casting solution. Under normal pressure, uniformly coat it on the surface of glass to obtain a composite membrane liquid film, and pre-estimate in a 25℃ deionized water and DMF mixed non-solvent bath until the residual solvent is 10%, then take out and roll with a pair of rollers to reduce the thickness by 20%, then immerse in a 25℃ deionized water non-solvent bath for complete curing to remove the remaining solvent to obtain a three-dimensional elastic composite separator with the structure as shown in Figure 1.

[0066] The mechanical properties, initial bubble point pressure, average pore size, and surface resistance of the prepared composite separator are shown in Table 1. At the same time, in order to test the friction resistance stability of the composite separator, a 0.06 mm thick steel wool is used to rub the surface of the composite separator on a wear testing machine to simulate the process of the separator being rubbed by the electrode in the electrolytic water, wherein the rubbing load weight is 500 g, the rubbing frequency is 1000 times, and the wear rate and bubble point pressure of the separator after rubbing are tested, as shown in Table 1. The high temperature stability of the prepared composite separator is tested by hydrothermal alkaline boiling, which simulates the local high temperature and pressure conditions inside the electrolytic tank under actual working conditions. The alkali solution is a 30wt.% potassium hydroxide solution, the separator is immersed in the oven at 120℃ for 24 hours, and after cooling, the weight loss rate of the separator before and after hydrothermal treatment is calculated. The bubble point of the separator after hydrothermal treatment is shown in Table 1. The prepared composite separator is installed in an alkaline water electrolysis hydrogen production electrolytic tank to test the current-voltage relationship as shown in Figure 3.

[0067] Example 2

[0068] Take 10 g of potassium hydroxide and 30 g of PPS mixed granulation, then melt spinning into fibers, fiber diameter is 20 pm, length is 60 pm, the first water washing solution is a mixture of 70% H2C2O4 and 30% n-butanol solution, then washed with deionized water for 3 times, dried and finally obtained the roughened fiber for use. Take 85 g of N,N-dimethylformamide, add 50 g of zirconium oxide powder (average particle size 100 nm), and 10 g of roughened PPS fiber, ultrasonic dispersion uniformly, then add 10 g of polysulfone and 2 g of PVP, stirring to obtain a uniform casting solution. The casting solution is uniformly coated on the surface of the glass to obtain a composite membrane liquid film with a thickness of 600 pm. Pre-solidify in air with humidity of 50% and temperature of 80°C to 10% solvent residue, then take out and roll to reduce the thickness by 5%, then immerse in a deionized water non-solvent bath at 25°C to completely solidify and remove the remaining solvent to obtain a composite membrane. The composite membrane is tested for various performance tests according to Example 1, and the results are shown in Tables 1-2 and Figure 3. The cross-sectional SEM image of the composite membrane is shown in Figure 2.

[0069] Example 3

[0070] Take 10 g of potassium hydroxide and 30 g of PPS mixed granulation, then melt spinning into fibers of different lengths, fiber diameter is 30 pm, length is 5 cm and 2 cm, the first water washing solution is a mixture of 80% HCOOH and 20% ethanol solution, then washed with deionized water for 3 times, dried and finally obtained the roughened fiber for use. Take 85 g of DMF, add 50 g of zirconium oxide powder (average particle size 100 nm), and 1.5 g of roughened PPS fiber with length of 5 cm and 2 cm respectively, ultrasonic dispersion uniformly, then add 10 g of polysulfone and 2 g of P123, 2 g of PVP, stirring to obtain a uniform casting solution. Apply a pressure of -100 kPa to uniformly coat it on the surface of a 30-mesh PPS wire mesh substrate to obtain a composite membrane liquid film with a thickness of 600 pm. Pre-solidify in a deionized water and DMF mixed non-solvent bath at 25°C to 5% solvent residue, then take out and roll to reduce the thickness by 10%, then immerse in a deionized water non-solvent bath at 25°C to completely solidify and remove the remaining solvent to obtain a three-dimensional elastic composite membrane, and test various performance tests according to Example 1. The test results are shown in Tables 1-2 and Figure 3.

[0071] Example 4

[0072] Take 10 g of sodium hydroxide and 30 g of PPS mixed granulation, then melt spinning into fibers, fiber diameter is 30 pm, length is 5 cm, the first water washing solution is a mixture of 80% HCOOH and 20% ethanol solution, then washed with deionized water for 3 times, dried and finally obtained the roughened fiber. The obtained fiber is prepared into a non-woven process with a density of 100 g / m2 The fiber cloth was prepared by weighing 60g of N-methylpyrrolidone and adding 50g of zirconium oxide powder (average particle size 100nm). After ultrasonic dispersion, 10g of polysulfone and 2g of P123 were added and stirred to dissolve, resulting in a uniform casting solution. The solution was coated on the inside and outside of the PPS cloth under normal pressure and pre-cured in a non-solvent bath of deionized water and N-methylpyrrolidone at 25°C until 20% of the solvent remained. The solution was then removed and rolled with rollers until the thickness was reduced by 15%. The solution was then immersed in a non-solvent bath of deionized water at 25°C for complete curing and removal of the remaining solvent to obtain a three-dimensional elastic composite membrane. Various performance tests were carried out according to Example 1. The test results are shown in Table 1-2 and Figure 3.

[0073] Example 5

[0074] 10g of sodium hydroxide and 30g of PPS were weighed, mixed, granulated, and then melt-spun into fibers of different lengths: 30μm in diameter, 3cm, and 1mm in length. The first washing solution was a mixture of 80% HCOOH and 20% ethanol. After three washes with deionized water and drying, roughened fibers were finally obtained. The resulting 5cm and 2cm fibers, each in equal proportions, were then processed using a nonwoven process to form fibers with a density of 150g / m². 2 The fiber cloth was prepared by weighing 60g of N-methylpyrrolidone, adding 50g of zirconium oxide powder (average particle size 100nm), and 2g of roughened PPS fiber with a length of 1mm. After ultrasonic dispersion, 11g of polysulfone and 2g of ammonium carbonate were added and stirred to dissolve, resulting in a homogeneous casting solution. The solution was coated on the inside and outside of the PPS cloth under a pressure of -30kPa and pre-cured in deionized water to remove 80% of the organic solvent. After rolling until the thickness decreased by 30%, the remaining organic solvent was washed away in deionized water to obtain a three-dimensional elastic composite membrane. Various performance tests were carried out according to Example 1, and the test results are shown in Tables 1-2 and Figure 3.

[0075] Example 6

[0076] 20g of NaHCO3 and 40g of PP were weighed, mixed, granulated, and then melt-spun into fibers with a diameter of 30μm and a length of 5cm. The first washing solution was a mixture of 80% HCOOH and 20% ethanol. After washing with deionized water three times and drying, roughened fibers were finally obtained. The obtained fibers were uniformly compacted and needle-punched to form fibers with a diameter of 120g / m². 2The fiber cloth was prepared by weighing 60g of DMF and adding 50g of zirconium oxide powder (average particle size 100nm). The mixture was ultrasonically dispersed until uniform, then 8g of polysulfone and 0.5g of PVB were added. The mixture was stirred and dissolved to obtain a homogeneous casting solution. Pressure was applied to evenly coat the inside and outside of the PP cloth. Pre-curing was carried out at 80% humidity and 80℃ until the solvent content decreased by 80%. Then, the mixture was rolled with rollers until the thickness decreased by 30%. Finally, the membrane was immersed in a 25℃ deionized water non-solvent bath to remove the organic solvent N,N-dimethylformamide. After complete curing, a three-dimensional elastic composite membrane was obtained. Performance tests were conducted according to Example 1, and the results are shown in Tables 1-2 and Figure 3.

[0077] Example 7

[0078] Weigh out 20g of NaHCO3 and 40g of PES, mix and granulate, then melt spin into fibers with a density of 30g / m 2 The fiber cloth, with a fiber diameter of 30 μm, was initially washed with a solution of 80% HCOOH and 20% ethanol, followed by three washes with deionized water and drying to obtain a roughened fiber cloth. 85 g of DMF was weighed, and 50 g of zirconium oxide powder (average particle size 100 nm) was added. The mixture was ultrasonically dispersed, and then 8 g of polysulfone and 0.5 g of PVB were added. The mixture was stirred and dissolved to obtain a homogeneous casting solution, which was uniformly coated onto the inside and outside of the PES cloth under normal pressure. After pre-curing in a 25°C deionized water and DMF mixed solvent bath to remove 90% of the organic solvent, the mixture was rolled until the thickness decreased to 50%. Finally, it was immersed in 25°C deionized water to remove the organic solvent N,N-dimethylformamide and cured completely to obtain a three-dimensional elastic composite membrane. Various performance tests were conducted according to Example 1, and the test results are shown in Tables 1-2 and Figure 3.

[0079] Example 8

[0080] 10g of potassium hydroxide and 30g of PPS were weighed, mixed, granulated, and then melt-spun into fibers with a diameter of 50μm and a length of 7cm. The first washing solution was a mixture of 80% HCOOH and 20% ethanol. After three washes with deionized water and drying, roughened fibers were finally obtained. The obtained fibers were then processed using a nonwoven process to produce fibers with a density of 60g / m³. 2 The fiber cloth was prepared by weighing 85g of DMF, adding 50g of zirconium oxide powder (average particle size 100nm), ultrasonically dispersing it evenly, then adding 8g of polysulfone and 0.5g of PVB, stirring to dissolve and obtain a homogeneous casting solution, which was then uniformly coated on the inside and outside of the PPS cloth. After pre-curing at 30% humidity and 85℃ to remove 90% of the solvent, it was rolled until the thickness decreased by 30%, and then immersed in deionized water at 25℃ to remove the organic solvent, thus obtaining a three-dimensional elastic composite membrane. Performance tests were conducted according to Example 1, and the results are shown in Tables 1-2 and Figure 3.

[0081] Example 9

[0082] ZrO2 melt-spun into fiber with a diameter of 60 μm and a length of 0.5 mm, and a diameter of 100 μm and a length of 0.5 mm. 60 g of DMF was weighed, 50 g of zirconium oxide powder (average particle size 100 nm) and 5 g of ZrO2 fiber were added, and the mixture was ultrasonically dispersed until uniform. Then 8 g of polysulfone and 0.5 g of PVB were added, and the mixture was stirred and dissolved to obtain a uniform casting solution. The casting solution was uniformly coated inside and outside a 50-mesh PPS mesh, and after 95% of the organic solvent was removed in a 25°C deionized water and DMF mixed solvent bath, the thickness was reduced by 0.2% by rolling, and then the composite membrane was completely solidified in deionized water at 25°C and placed in a 60°C oven for drying for 3 min to obtain a three-dimensional elastic composite membrane. The performance tests were carried out according to Example 1, and the test results are shown in Tables 1-2 and Figure 3. 2

[0083] Example 10

[0084] ZrO2 melt-spun into fiber with a diameter of 60 μm and a length of 0.5 mm. 60 g of DMF was weighed, 50 g of zirconium oxide powder (average particle size 100 nm) and 5 g of ZrO2 fiber were added, and the mixture was ultrasonically dispersed until uniform. Then 8 g of polysulfone and 0.5 g of PVB were added, and the mixture was stirred and dissolved to obtain a uniform casting solution. The casting solution was uniformly coated inside and outside a 50-mesh PPS mesh, and after 95% of the organic solvent was removed in a 25°C deionized water and DMF mixed solvent bath, the thickness was reduced by 0.2% by rolling, and then the composite membrane was completely solidified in deionized water at 25°C and placed in a 60°C oven for drying for 3 min to obtain a three-dimensional elastic composite membrane. The performance tests were carried out according to Example 1, and the test results are shown in Tables 1-2 and Figure 3.

[0085] Comparative Example 1

[0086] 85 g of DMF was weighed, 50 g of zirconium oxide powder (average particle size 100 nm) was added, and the mixture was ultrasonically dispersed until uniform. Then 10 g of polysulfone solid, 2 g of P123, and 2 g of PVP were added, and the mixture was stirred and dissolved to obtain a uniform casting solution. The casting solution was uniformly coated on a 50-mesh silk mesh substrate to obtain a composite membrane liquid film, and after pre-solidification in air for 30 s, the composite membrane was obtained by immersing in a 25°C deionized water and DMF mixed non-solvent bath to remove the organic solvent N,N-dimethylformamide. The performance tests of the composite membrane were carried out according to the method of Example 1, and the test results are shown in Tables 1-2 and Figure 3.

[0087] Table 1 Performance test results

[0088] ​From the data in Table 1, it can be seen that the treated fibers can greatly increase the contact with the casting solution, improve the overall mechanical strength of the separator and the peeling strength of the membrane layer and the base web. After the aging of high temperature hydrothermal and friction experiment, the bubble point pressure of the separator prepared by the treated fibers does not decrease obviously, and the mass wear rate is also reduced by an order of magnitude, which shows that the composite separator can tolerate local high temperature and electrode friction under actual working conditions, and has great guarantee for the safety of electrolytic hydrogen production.

[0089] Table 2 shows the relationship between different current densities and cell voltages of each example and comparative example in Figure 3.

[0090] Table 2 performance test results

[0091] From the data of Table 2 and Figure 3, it can be seen that under the same current density, the cell voltage of the electrolysis cell using the separator of the present disclosure (Examples 1-10) is lower than that of the separator not containing hydrophilic and / or roughened fiber (Comparative Example 1). This shows that the addition of hydrophilic and / or roughened fiber improves the affinity with the casting solution, thereby improving the wettability of the separator with the electrolyte, so that the resistance of ion transmission can be reduced to cause lower resistance.

[0092] As can be seen from Figure 2, the membrane material interacts with the fiber grid, the membrane material is evenly distributed in the fiber bridge, and the membrane material is firmly targeted by the three-dimensional fiber, improving the mechanical stability of the separator. There are no finger-shaped large holes in the composite membrane, which is beneficial to block the gas from crossing, and improves the chemical stability of the composite separator.

[0093] The preferred embodiments of the present disclosure disclosed above are only used to help explain the present disclosure. The preferred embodiments do not describe all the details, nor limit the disclosure to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present disclosure. The present disclosure selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present disclosure, so that those skilled in the art can well understand and utilize the present disclosure. The present disclosure is limited only by the claims and their full scope and equivalents.

Claims

1. A composite separator, characterized by, The composite diaphragm comprises a three-dimensional porous support layer and a membrane material, and the pores of the three-dimensional porous support layer are filled with the membrane material. The three-dimensional porous support layer comprises fiber filaments and / or fiber cloth, and the fiber filaments and / or the fiber filaments constituting the fiber cloth are hydrophilic fiber filaments and / or roughened fiber filaments.

2. The composite separator of claim 1, wherein The hydrophilic fiber filaments are one or more of zirconium oxide fiber, zirconium silicate fiber, intrinsic hydrophilic modified fiber filaments and surface hydrophilic functional group modified fiber filaments. The roughened fiber filaments are porous fiber filaments.

3. The composite separator of claim 2, wherein The intrinsic hydrophilic modified fiber filaments comprise a fiber raw material and a hydrophilic agent, and the hydrophilic agent is one or more of ZrO2, CeO2, SiO2, Al2O3, TiO2, BaSO4, BaCeO4, polyvinyl butyral ester, polyvinyl pyrrolidone; and / or The hydrophilic functional group comprises one or more of amino, sulfonic acid group, carboxyl, carbonyl, hydroxyl; and / or The fiber raw material is one or more of PP, PES, PSU, PPS, PEEK, nylon fiber.

4. The composite separator of claim 2, wherein The porosity of the porous fiber filaments is 10-60%.

5. The composite separator of claim 1, wherein The linear density of the fiber yarn is 0.3D-7D or density 2-6g / cm 3 ; the fiber yarn diameter is 10-150μm; the fiber yarn length is 30μm-7cm; the fiber cloth grammage is 30-500g / m 2 .

6. The composite separator of claim 1, wherein The addition amount of the hydrophilic fiber filaments and / or the roughened fiber filaments is 30% or less of the total mass of the membrane material; preferably, 2-20%.

7. The composite separator of claim 1, wherein The membrane material comprises hydrophilic inorganic powder, additive and polymer binder, the mass ratio of the hydrophilic inorganic powder to the polymer binder is 2:1-10:1, and the mass ratio of the additive to the polymer binder is 1:20-1:2; Preferably, the hydrophilic inorganic powder comprises one or more of titanium dioxide, zirconium dioxide, cerium dioxide, barium sulfate, calcium sulfate, barium titanate, calcium titanate, and the particle size distribution of the hydrophilic inorganic powder is 0.1-20 μm; and / or The polymer binder is one or more of polyether sulfone, polyaryl sulfone, polyphenylene sulfone, bisphenol A polysulfone, sulfonated polyether sulfone, sulfonated polyaryl sulfone, sulfonated polyphenylene sulfide; and / or The additive comprises one or more of polyvinyl butyral, polyvinyl pyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polypropylene glycol and ethylene oxide adduct, polybenzimidazole, ammonium carbonate, ammonium bicarbonate. The fiber cloth is any one of fiber bonded cloth, needle felt, non-woven fabric, and velvet.

8. The composite separator of claim 1, wherein It also comprises a wire mesh substrate; preferably, the wire mesh substrate is a wire mesh woven from polypropylene, polyphenylene sulfide, polytetrafluoroethylene, polyether ether ketone, and nylon material; more preferably, the mesh number of the wire mesh is 20-150 meshes, and the thickness is 30-350 μm.

9. The composite separator of claim 1, wherein It comprises:

10. A method of producing the composite separator according to any one of claims 1 to 9, characterized by, A casting solution is provided, which comprises a membrane material, an organic solvent and optional fiber filaments; The casting solution is coated on the fiber cloth, so that the casting solution fills the pores of the fiber cloth to form a first liquid membrane layer; Alternatively The casting solution containing the fiber filaments is coated on the surface of the substrate to form a second liquid membrane layer; The first liquid membrane layer or the second liquid membrane layer is pre-solidified in air or a coagulation bath, then rolled, and then placed in a coagulation bath for solidification to remove the remaining organic solvent to form the composite diaphragm; ​ The fiber yarn or the fiber yarns constituting the fiber cloth are hydrophilic fiber yarns and / or roughened fiber yarns; the coating step is coating under normal pressure to -100 KPa (gauge pressure); the overall thickness decreases by 0-40% before and after rolling; and the pre-solidification is reduced by 70-99.8% in the organic solvent.

11. The method of claim 10, wherein the composite separator is prepared by the steps of: The intrinsic hydrophilic modified fiber yarns are obtained by mixing, granulating and melt spinning after adding a hydrophilic agent, the hydrophilic agent being one or more of ZrO2, CeO2, SiO2, Al2O3, TiO2, BaSO4, BaCeO4, polyvinyl butyral ester, and polyvinyl pyrrolidone; The hydrophilic functional groups include one or more of amino groups, sulfonic acid groups, carboxyl groups, carbonyl groups, and hydroxyl groups; The roughened fiber yarns are obtained by mixing, granulating and melt spinning after adding a pore-forming agent and pore-forming, the pore-forming agent being any one of KOH, NaOH, K2SO4, Na2SO4, K2CO3, Na2CO3, KHCO3, NaHCO3, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, and polypropylene glycol and ethylene oxide adduct powder, and the pore-forming process being removing the pore-forming agent from the original fiber yarn obtained by spinning through multi-stage water washing; The mass ratio of the hydrophilic additive or the pore-forming agent to the intrinsic fiber is 1:30-10:

1. The number of multi-stage water washing is ≥3 times, the pH value of the water solution used in the first-stage water washing is ≤8, the first-stage water washing solution is a mixture of an acidic solution and an organic solvent, the acidic solution is an aqueous solution of any one of H2SO4, HNO3, HCl, HCOOH, and H2C2O4, and the organic solvent is any one of ethanol, isopropanol, and n-butanol; the volume of the acidic solution in the first-stage water washing solution is 3-10 parts, and the volume of the organic solvent is 1-3 parts; and the last-stage water washing solution is pure water.

12. The method of claim 11, wherein the composite separator is prepared by the steps of: The temperature of the air pre-solidification is 10-150 degrees, the time is 0-30 min, and the humidity is 15-90% RH; 13. The method of claim 10, wherein the composite separator is prepared by the steps of: (a) preparing a porous polymer layer; (b) preparing a porous inorganic layer; and (c) combining the porous polymer layer and the porous inorganic layer. The non-solvent of the coagulation bath is water or a mixed solvent of water and one of dimethyl sulfoxide, N-methyl pyrrolidone, N-ethyl pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide, and the temperature of the coagulation bath is 5-80 degrees, and the coagulation bath time is 2 min-2 h.

14. Use of the composite separator in any one of claims 1-9 in the production of hydrogen from alkaline electrolyte water. ​

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