Separator for alkaline water electrolysis

Abstract

To provide a separator having sufficient mechanical qualities combined with high ionic conductivity, and a method for producing a separator for alkaline water electrolysis.SOLUTION: A separator for alkaline electrolysis comprises a porous support (10) and first (20b) and second (30b) porous layers provided on respectively one side and the other side of the porous support, in which the porous support has a thickness (d1) of 150 μm or less and the total thickness (d2) of the separator is less than 250 μm. Also a method is disclosed wherewith such a separator may be prepared.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a separator for alkaline water electrolysis and a separator obtained by this method. [Background technology]

[0002] Today, hydrogen is used in several industrial processes, for example, its use as a raw material in the chemical industry and as a reducing agent in the metallurgical industry. Hydrogen is the basic building block for the production of ammonia and, in turn, methanol, which is used in the production of fertilizers and many polymers. Refineries, where hydrogen is used to process intermediate oil products, are another area of use.

[0003] Hydrogen is also considered an important future energy carrier, meaning that it can store and deliver energy in a usable form. Energy is released through an exothermic combustion reaction with oxygen, thereby forming water. No greenhouse gases, including carbon, are emitted during such a combustion reaction.

[0004] In order to realize a low-carbon society, renewable energy utilizing natural energy such as solar and wind power is becoming increasingly important.

[0005] Electricity generation from wind and solar power systems is highly dependent on weather conditions, resulting in large fluctuations and imbalances between the supply and demand of electricity. To store surplus electricity, so-called power-to-gas technologies, in which electricity is used to produce gaseous fuels such as hydrogen, have attracted much interest in recent years. As the generation of electricity from renewable energy sources increases, so too does the demand for storage and transportation of the generated energy.

[0006] Alkaline water electrolysis is an important manufacturing process in which electricity may be converted into hydrogen.

[0007] In alkaline water electrolysis cells, so-called separators or diaphragms are used to separate electrodes of different polarity, to prevent short circuits between these electronically conducting components (electrodes), and to prevent recombination of hydrogen (formed at the cathode) with oxygen (formed at the anode) by avoiding gas crossover. While performing all these functions, the separator should be a high ionic conductor for the transport of hydroxyl ions from the cathode to the anode.

[0008] Separators typically include a porous support that reinforces the separator and facilitates its handling and installation in an electrolytic cell, as disclosed in US Patent No. 5,929,999 (Hydrogen Systems).

[0009] Patent Document 2 (VITO) discloses a process for preparing a reinforced separator. This process results in a membrane with symmetrical properties. The process includes the steps of providing a porous support as a web and a suitable dope solution, guiding the web in a vertical position, coating both sides of the web equally with the dope solution to produce a web-coated support, and subjecting the dope-coated web to a symmetrical surface pore-forming step and a symmetrical coagulation step to produce a reinforced membrane.

[0010] US Patent No. 5,999,232 and US Patent No. 5,999,232 (Agfa Gevaert and VITO) disclose manufacturing methods for producing reinforced membranes with symmetrical properties as described in US Patent No. 5,999,232. The porous supports used in these manufacturing methods have a thickness of more than 190 μm.

[0011] However, a porous support can reduce ionic conductivity through the separator and therefore reduce the efficiency of the electrolysis process.

[0012] Therefore, there is a need for separators that have sufficient mechanical qualities combined with high ionic conductivity. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] European Patent Application Publication No. 232923 [Patent Document 2] European Patent Application Publication No. 1776490 [Patent Document 3] International Publication No. 2009 / 147084 Brochure [Patent Document 4] International Publication No. 2009 / 147086 Brochure Summary of the Invention

[0014] An object of the present invention is to provide a separator having sufficient mechanical qualities and improved ionic conductivity.

[0015] This object is achieved by the separator defined in claim 1.

[0016] Another object of the present invention is to provide a method for manufacturing such a separator.

[0017] Further objects of the present invention will become apparent from the following description. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a schematic diagram of one embodiment of a separator according to the present invention. [Figure 2] 1 is a schematic diagram illustrating one embodiment of a method for manufacturing a separator according to the present invention. [Figure 3] 3 is a schematic diagram illustrating another embodiment of a method for manufacturing a separator according to the present invention. [Figure 4] Figure 4 shows the waviness observed on the separator prepared in the example (Figure 4A = S1; Figure 4B = S2). DETAILED DESCRIPTION OF THE INVENTION

[0019] Alkaline water electrolysis separator The separator (1) for alkaline electrolysis according to the present invention comprises a porous support (10) and first (20b) and second (30b) porous layers provided on one side and the other side of the porous support, respectively, and is characterized in that the thickness of the porous support (d1) is 150 μm or less, and the thickness of the separator (d2) is 250 μm or less.

[0020] The thickness d2 of the separator is preferably 225 μm or less, more preferably 200 μm or less, most preferably 175 μm or less, and particularly preferably 150 μm or less. If the thickness of the separator is less than 100 μm, the physical strength may be insufficient, and if the thickness exceeds 250 μm, the electrolysis efficiency may decrease.

[0021] The separator preferably has a resistance of 0.1 ohm cm in 30 wt % aqueous KOH at 80°C. 2 less than, more preferably 0.07 ohm cm 2 It has an ionic resistance of less than 1000 kJ / cm.

[0022] Ionic resistance may be determined with an Inolab® Multi 9310 IDS instrument available from VWR, part of Avantor, equipped with a TetraCon 925 conductivity cell available from Xylem.

[0023] The first and second porous layers disposed on the porous support may be the same or different.

[0024] As described in more detail below, the preferred separator is prepared by applying a coating solution, also commonly referred to as a dope solution, containing a polymeric resin, hydrophilic inorganic particles, and a solvent onto both surfaces of a porous support, followed by a phase inversion process in which the polymeric resin forms a three-dimensional porous polymer network, resulting in a porous layer.

[0025] When the dope solution is applied to both sides of the porous support, the dope solution impregnates the support, and the porous support is preferably completely impregnated with the dope solution.

[0026] After phase inversion, impregnation of the porous support ensures that the three-dimensional porous polymer network also extends into the porous support, which results in good adhesion between the porous layer and the porous support.

[0027] A preferred separator (1) is shown schematically in FIG.

[0028] The dope solution is applied to both sides of the porous support (10) and the porous support is completely impregnated with the applied dope solution. The applied dope layers are designated 20a and 30a.

[0029] After the phase inversion step (50), a separator is obtained which comprises a porous support (10) and porous layers (20b, 20b) on both sides of the support.

[0030] The pore size of the separator must be small enough to prevent the recombination of hydrogen and oxygen by avoiding gas crossover, while larger pore sizes are preferred to ensure efficient transport of hydroxyl ions from the cathode to the anode. Efficient transport of hydroxyl ions requires efficient permeation of the electrolyte into the separator.

[0031] The maximum pore diameter (PDmax) of the separator is preferably 0.05 to 2 μm, more preferably 0.10 to 1 μm, and most preferably 0.15 to 0.5 μm.

[0032] The two sides of the separator may have the same or different maximum pore sizes.

[0033] Preferred separators having the same pore size on both sides are disclosed in the above-mentioned Patent Documents 2 and 3.

[0034] A preferred separator having different pore sizes on both sides is disclosed in European Patent Application Publication No. 3652362. The maximum pore size PDmax(1) on the outer surface of the first porous layer is preferably 0.05 to 0.3 μm, more preferably 0.08 to 0.25 μm, and most preferably 0.1 to 0.2 μm, and the maximum pore size PDmax(2) on the outer surface of the second porous layer is preferably 0.2 to 6.5 μm, more preferably 0.2 to 1.50 μm, and most preferably 0.2 to 0.5 μm. The ratio of PDmax(2) to PDmax(1) is preferably 1.1 to 20, more preferably 1.25 to 10, and most preferably 2 to 7.5. A smaller PDmax(1) ensures efficient separation of hydrogen and oxygen, while a smaller PDmax(2) ensures good penetration of the electrolyte in the separator, resulting in sufficient ionic conductivity.

[0035] The pore size referred to is preferably measured using the bubble point test method described in American Society for Testing and Materials (ASMT) method F316.

[0036] The porosity of the separator is preferably 30 to 70%, more preferably 40 to 60%. A separator having a porosity in the above range generally has excellent ion permeability and excellent gas barrier properties because the pores of the diaphragm are continuously filled with the electrolyte solution.

[0037] porous support The porous support is used to reinforce the separator and ensure its mechanical strength.

[0038] The thickness (d1) of the porous support is 150 μm or less, preferably 125 μm or less, more preferably 100 μm or less, most preferably 75 μm or less, and particularly preferably 50 μm or less.

[0039] It has been observed that as the thickness of the porous support decreases, the ionic conductivity through the reinforced separator increases.

[0040] However, to ensure sufficient mechanical properties of the reinforced separator, the thickness of the porous support is preferably 20 μm or more, more preferably 40 μm or more.

[0041] The porous support may be selected from the group consisting of a porous cloth, a porous metal plate, and a porous ceramic plate.

[0042] The porous support is preferably a porous fabric, more preferably a porous polymer fabric.

[0043] Porous polymer fabrics may be woven or nonwoven. Woven fabrics typically have better dimensional stability and uniformity of open area and thickness. However, the production of woven fabrics with a thickness of 100 μm or less is more complicated and results in more expensive fabrics. The production of nonwoven fabrics is relatively uncomplicated, even for fabrics with a thickness of 100 μm or less. Nonwoven fabrics may also have larger openings.

[0044] The open area of the porous support is preferably 30-80%, more preferably 40-70%, to ensure good penetration of the electrolyte into the support.

[0045] Suitable porous polymer fabrics are prepared from polypropylene, polyethylene (PE), polysulfone (PS), polyphenylene sulfide (PPS), polyamide / nylon (PA), polyethersulfone (PES), polyphenylsulfone (PPSU), polyethylene terephthalate (PET), polyetheretherketone (PEEK), sulfonated polyetheretherketone (s-PEEK), monochlorotrifluoroethylene (CTFE), copolymers of ethylene with tetrafluoroethylene (ETFE) or chlorotrifluoroethylene (ECTFE), polyimide, polyetherimide, and m-aramid.

[0046] Preferred polymer fabrics are prepared from polypropylene (PP) or polyphenylsulfide (PPS), most preferably polyphenylsulfide (PPS).

[0047] The polyphenylene sulfide-based porous support has high resistance to high temperatures and highly concentrated alkaline solutions, and high chemical stability against active oxygen generated from the anode during the water electrolysis process. In addition, polyphenyl sulfide can be easily processed into various forms such as woven or nonwoven fabrics.

[0048] The density of the porous support is preferably 0.1 to 0.7 g / cm 3 is.

[0049] The porous support is preferably a continuous web, which allows for manufacturing processes such as those disclosed in US Pat. Nos. 5,629,999 and 5,729,999.

[0050] The width of the web is preferably 30 to 300 cm, more preferably 40 to 200 cm.

[0051] polymer resin The porous layer preferably comprises a polymer resin.

[0052] The polymer resin forms a three-dimensional porous network, which is the result of a phase inversion process in the preparation of the separator, as described below.

[0053] The polymer resin may be selected from fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), olefin resins such as polypropylene (PP), and aromatic hydrocarbon resins such as polyethylene terephthalate (PET) and polystyrene (PS). The polymer resin may be used alone, or two or more of the polymer resins may be used in combination.

[0054] PVDF and vinylidene fluoride (VDF) copolymers are preferred due to their oxidation / reduction resistance and film-forming properties. Among these, terpolymers of VDF, hexanefluoropropylene (HFP) and chlorotrifluoroethylene (CTFE) are preferred due to their excellent swelling properties, heat resistance and adhesion to electrodes.

[0055] Another preferred polymer resin is an aromatic hydrocarbon resin due to its excellent heat resistance and alkali resistance. Examples of aromatic hydrocarbon resins include, for example, polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyacrylate, polyetherimide, polyimide, and polyamideimide.

[0056] Particularly preferred polymer resins are selected from the group consisting of polysulfone, polyethersulfone and polyphenylsulfone, with polysulfone being most preferred.

[0057] The molecular weight (Mw) of polysulfone, polyethersulfone, and polyphenylsulfone is preferably 10,000 to 500,000, more preferably 25,000 to 250,000. If Mw is too low, the physical strength of the porous layer may be insufficient. If Mw is too high, the viscosity of the dope solution may be too high.

[0058] Examples of polysulfones, polyethersulfones and combinations thereof are disclosed in European Patent Application Publication No. 3085815, paragraphs

[0021] to

[0032] .

[0059] inorganic hydrophilic particles The hydrophilic layer preferably contains hydrophilic particles.

[0060] Preferred hydrophilic particles are selected from metal oxides and metal hydroxides.

[0061] Preferred metal oxides are selected from the group consisting of zirconium oxide, titanium oxide, bismuth oxide, cerium oxide and magnesium oxide.

[0062] Preferred metal hydroxides are selected from the group consisting of zirconium hydroxide, titanium hydroxide, bismuth hydroxide, cerium hydroxide, and magnesium hydroxide. Particularly preferred magnesium hydroxide is described in European Patent Application Publication No. 3660188, paragraphs

[0040] to

[0041] .

[0063] is disclosed in.

[0063] Another preferred hydrophilic particle is barium sulfate particle.

[0064] Other hydrophilic particles that may be used are nitrides and carbides of elements from Group IV of the periodic table.

[0065] The hydrophilic particles preferably have a D50 particle size of 0.05 to 2.0 μm, more preferably 0.1 to 1.5 μm, most preferably 0.15 to 1.00 μm, and particularly preferably 0.2 to 0.75 μm. The D50 particle size is preferably 0.7 μm or less, preferably 0.55 μm or less, and more preferably 0.40 μm or less.

[0066] The D50 particle size is also known as the median diameter or mean value of a particle size distribution. The D50 particle size is the value of 50% of the particle size in the cumulative distribution. For example, if D50=0.1um, then 50% of the particles are larger than 1.0um and 50% are smaller than 1.0um.

[0067] The D50 particle size is preferably measured using laser diffraction, for example using a Mastersizer from Malvern Panalytical.

[0068] The amount of hydrophilic particles relative to the total dry weight of the porous layer is preferably at least 50% by weight, more preferably at least 75% by weight.

[0069] The weight ratio of hydrophilic particles to polymeric resin is preferably greater than 60 / 40, more preferably greater than 70 / 30, and most preferably greater than 75 / 25.

[0070] Preparation of the separator A preferred method for preparing the separator described above is: - applying a dope solution as described below to both sides of the porous support; - performing a phase inversion on the applied dope solution, thereby forming first and second porous layers on one and the other side of the porous support, respectively; The porous support has a thickness (d1) of 150 μm or less, the separator has a thickness (d2) of 250 μm or less, and the shear rate is 100 s -1 and the viscosity of the dope solution measured at a temperature of 20° C. is characterized as being at least 20 Pa.s, more preferably at least 30 Pa.s, and most preferably at least 40 Pa.s.

[0071] Preferred methods for making reinforced separators are disclosed in U.S. Patent Nos. 5,629,999 and 5,729,999 for symmetric separators and EP 3,652,362 for asymmetric separators. These methods result in web-reinforced separators, in which the web, i.e., the porous support, is well embedded in the separator without the web appearing on the surface of the separator.

[0072] Another manufacturing method that may be used is disclosed in EP-A-3272908.

[0073] Dope Solution The dope solution preferably includes a polymer resin as described above, hydrophilic particles as described above, and a solvent.

[0074] The solvent of the dope solution is preferably an organic solvent capable of dissolving the polymer resin, and further, the organic solvent is preferably miscible with water.

[0075] The solvent is preferably selected from N-methyl-pyrrolidone (NMP), N-ethyl-pyrrolidone (NEP), N-butyl-pyrrolidone (NBP), N,N-dimethylformamide (DMF), formamide, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), acetonitrile, and mixtures thereof.

[0076] For health and safety reasons, a highly preferred solvent is N-butyl-pyrrolidone (NBP).

[0077] The dope solution may further contain other ingredients to optimize the properties of the resulting polymer layers, such as their porosity and the maximum pore size at their outer surface.

[0078] The doping solution preferably contains additives to optimize the surface and internal pore size of the porous layer. Such additives may be organic or inorganic compounds, or a combination thereof.

[0079] Organic compounds that may affect pore formation in the porous layer include polyethylene glycol, polyethylene oxide, polypropylene glycol, ethylene glycol, tripropylene glycol, glycerol, polyhydric alcohols, dibutyl phthalate (DBP), diethyl phthalate (DEP), diundecyl phthalate (DUP), isononanoic or neodecanoic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetate, polyethyleneimine, polyacrylic acid, methylcellulose, and dextran.

[0080] Preferred organic compounds that may affect pore formation in the porous layer are selected from polyethylene glycol, polyethylene oxide and polyvinylpyrrolidone.

[0081] Preferred polyethylene glycols have a molecular weight of 10,000 to 50,000, preferred polyethylene oxides have a molecular weight of 50,000 to 300,000, and preferred polyvinylpyrrolidones have a molecular weight of 30,000 to 100,000.

[0082] A particularly preferred organic compound that may affect pore formation in the porous layer is glycerol.

[0083] The amount of the compound that may affect pore formation is preferably 0.1 to 15% by weight, more preferably 0.5 to 5% by weight, based on the total weight of the dope solution.

[0084] Inorganic compounds that may affect pore formation include calcium chloride, magnesium chloride, lithium chloride and barium sulfate.

[0085] A combination of two or more additives that affect pore formation may be used.

[0086] The dope solutions on both sides of the porous support may be the same or different.

[0087] Dope solution application The dope solution may be applied onto the surface of the substrate, preferably a porous support, by any coating or casting technique.

[0088] The preferred coating technique is extrusion coating.

[0089] In a highly preferred embodiment, the dope solution is applied by a slot die coating technique, with two slot coating dies (FIGS. 2 and 3, 200 and 300) positioned on either side of the porous support.

[0090] The slot coating die can maintain the dope solution at a predetermined temperature, distribute the dope solution uniformly on the substrate, and adjust the coating thickness of the applied dope solution.

[0091] shear rate 100s -1 and the viscosity of the dope solution measured at a temperature of 20° C. is at least 20 Pa.s, more preferably at least 30 Pa.s, and most preferably at least 40 Pa.s.

[0092] The dope solution is preferably shear thinning. Shear rate: 100 s -1 Viscosity at shear rate 1s -1 is preferably at least 2, more preferably at least 2.5, and most preferably at least 5.

[0093] The porous support is preferably a continuous web, which is transported downward between slot coating dies (200, 300) as shown in FIGS.

[0094] Immediately after application, the porous support is impregnated with the dope solution.

[0095] Preferably, the porous support is completely impregnated with the applied dope solution.

[0096] Phase inversion process After applying the dope solution onto the porous support, the applied dope solution is subjected to a phase inversion process, in which the applied dope solution is converted into a porous hydrophilic layer.

[0097] In a preferred embodiment, both the dope solutions applied to the porous support are subjected to phase inversion.

[0098] Any phase inversion mechanism may be used to prepare the porous hydrophilic layer from the applied dope solution.

[0099] The phase inversion process preferably comprises a so-called liquid induced phase separation (LIPS) process, a vapor induced phase separation (VIPS) process, or a combination of a VIPS process and a LIPS process. Preferably, the phase inversion process comprises both a VIPS process and a LIPS process.

[0100] Both LIPS and VIPS are non-solvent induced phase inversion processes.

[0101] In the LIPS process, a porous support coated on both sides with a dope solution is contacted with a non-solvent that is miscible with the solvent of the dope solution.

[0102] Typically, this is done by immersing the porous support, coated on both sides with the dope solution, in a non-solvent bath, also called a coagulation bath.

[0103] The non-solvent is preferably water, water and N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylsulfoxide (DMSO), and dimethylacetamide (DM A mixture of water and an aprotic solvent selected from the group consisting of (A) and (B), an aqueous solution of a water-soluble polymer such as PVP or PVA, or a mixture of water and an alcohol such as ethanol, propanol or isopropanol.

[0104] The non-solvent is most preferably water.

[0105] The temperature of the coagulation bath is preferably 20 to 90°C, more preferably 40 to 70°C.

[0106] The migration of solvent from the coated polymer layer to the non-solvent bath and from the non-solvent to the polymer layer results in phase inversion and the formation of a three-dimensional porous polymer network. Impregnation of the applied dope solution into the porous support results in good adhesion of the resulting hydrophilic layer onto the porous support.

[0107] In a preferred embodiment, a continuous web (100) coated on both sides with dope solution is transported downward in a vertical position towards a coagulation bath (800), as shown in FIGS.

[0108] In the VIPS process, the porous support coated with the dope solution is exposed to a non-solvent vapor, preferably humid air.

[0109] Preferably, the solidification step includes both the VIPS step and the LIPS step. Preferably, the VIPS step is performed before the LIPS step. In a particularly preferred embodiment, the porous support coated with the dope solution is first exposed to humid air (VIPS step) before being immersed in a water bath (LIPS step).

[0110] In the manufacturing method shown in Figure 2, VIPS is performed in the region 400 between the slot coating die (200, 300) and the surface of the non-solvent in the coagulation bath (800), which is shielded from the environment using, for example, an insulating metal plate (500).

[0111] The degree and rate of water movement in the VIPS process can be controlled by adjusting the air velocity, air relative humidity and temperature, and exposure time.

[0112] The exposure time may be adjusted by varying the distance d between the slot coating die (200, 300) and the surface of the non-solvent in the coagulation bath (800) and / or the speed at which the elongated web 100 is transported from the slot coating die toward the coagulation bath.

[0113] The relative humidity within the VIPS region (400) may be controlled by the temperature of the coagulation bath and the shielding of the VIPS region (400) from the environment and the coagulation bath.

[0114] The velocity of the air may be regulated by the rotational speed of the ventilator (420) within the VIPS region (400).

[0115] The VIPS steps performed on one side of the separator and the other side of the separator resulting in the second porous polymer layer may be the same (FIG. 2) or different (FIG. 3).

[0116] After the phase inversion step, preferably the LIPS step in a coagulation bath, a washing step may be performed.

[0117] Preferably, the phase inversion step or the optional washing step is followed by a drying step. Separator manufacturing

[0118] 2 and 3 show a schematic representation of a preferred embodiment for producing a separator according to the present invention.

[0119] The porous support is preferably a continuous web (100).

[0120] The web is unwound from the supply roller (600) and guided downwards in a vertical position between the two coating units (200) and (300).

[0121] In these coating units, the dope solution is coated on both sides of the web. The coating thickness on both sides of the web can be adjusted by optimizing the viscosity of the dope solution and the distance between the coating unit and the surface of the web. Preferred coating units are described in EP 2296825, paragraphs

[0043] ,

[0047] ,

[0048] ,

[0060] ,

[0063] , and FIG. 1.

[0122] The web, coated on both sides with the dope solution, is then transported a distance d downwards towards the coagulation bath (800).

[0123] In the coagulation bath, the LIPS process takes place.

[0124] The VIPS process takes place in a VIPS zone prior to entering the coagulation bath. In Figure 2, the VIPS zone (400) is the same on both sides of the coated web, while in Figure 3, the VIPS zones (400(1)) and (400(2)) are different on both sides of the coated web.

[0125] The relative humidity (RH) and air temperature within the VIPS area may be optimized using insulating metal plates. In Figure 2, the VIPS area (400) is completely shielded from the environment by such metal plates (500). Therefore, the RH and air temperature are primarily determined by the temperature of the coagulation bath. The air velocity within the VIPS area may be regulated by a ventilator (420).

[0126] In FIG. 3, VIPS regions 400(1) and 400(2) are different from each other. The VIPS region 400(1) on one side of the coated web, including the metal plate 500(1), is identical to the VIPS region 400 in FIG. 2. The VIPS region 400(2) on the other side of the coated web is different from region 400(1). There is no metal plate shielding the VIPS region 400(2) from the environment. However, the VIPS region 400(2) is now shielded from the coagulation bath by the insulating metal plate 500(2). Additionally, there is no ventilator within VIPS region 400(2). This results in the VIPS region 400(1) having a higher RH and air temperature compared to the RH and air temperature of the other VIPS region 400(2).

[0127] High RH and / or high air velocity in the VIPS region typically results in larger maximum pore sizes.

[0128] The RH in one VIPS region is preferably greater than 85%, more preferably greater than 90%, and most preferably greater than 95%, while the RH in another VIPS region is preferably less than 80%, more preferably less than 75%, and most preferably less than 70%.

[0129] After the phase separation process, the reinforced separator is then transported to a winding system (700).

[0130] After providing a liner on one side of the separator, the separator and applied liner may be rolled up.

[0131] electrolytic cell The separator for alkaline water electrolysis according to the present invention may be used in an alkaline water electrolysis cell.

[0132] An electrolytic cell typically consists of two electrodes, an anode and a cathode, separated by a separator. An electrolyte is present between both electrodes.

[0133] When electrical energy (voltage) is applied to an electrolysis cell, hydroxyl ions in the electrolyte are oxidized to oxygen at the anode, and water is reduced to hydrogen at the cathode. The hydroxyl ions formed at the cathode migrate through a separator to the anode. The separator prevents mixing of the hydrogen gas and oxygen gas formed during electrolysis.

[0134] The electrolyte solution is typically an alkaline solution. A preferred electrolyte solution is an aqueous solution of an electrolyte selected from sodium hydroxide or potassium hydroxide. Potassium hydroxide electrolytes are often preferred due to their higher specific conductivity. The concentration of the electrolyte in the electrolyte solution is preferably 20 to 40 wt % based on the total weight of the electrolyte solution. The temperature of the electrolyte solution is preferably 50 to 120°C, more preferably 75 to 100°C.

[0135] The electrodes typically comprise a substrate provided with a so-called catalyst layer, which may be different for the anode, where oxygen is formed, and the cathode, where hydrogen is formed.

[0136] Typical substrates are made from conductive materials selected from the group consisting of nickel, iron, mild steel, stainless steel, vanadium, molybdenum, copper, silver, manganese, platinum group elements, graphite, and chromium. The substrate may also be made from a conductive alloy of two or more metals or a mixture of two or more conductive materials. Preferred materials are nickel or nickel-based alloys. Nickel has good stability in strong alkaline solutions, good electrical conductivity, and is relatively inexpensive.

[0137] The catalytic layer disposed on the anode preferably has a high oxygen generating capacity. The catalytic layer preferably contains nickel, cobalt, iron, and a platinum group element. The catalytic layer may contain these elements as elemental metals, compounds (e.g., oxides), composite oxides, or alloys of multiple metal elements, or mixtures thereof. Preferred catalytic layers include plated nickel, plated alloys of nickel and cobalt or nickel and iron, composite oxides containing nickel and cobalt such as LaNiO3, LaCoO3, and NiCo2O4, compounds of platinum group elements such as iridium oxide, or carbon materials such as graphene.

[0138] Raney nickel structures are formed by selectively leaching aluminum or zinc from Ni-Al or Ni-Zn alloys. The lattice vacancies formed during leaching result in a large surface area and a high density of lattice defects, which are active sites for electrocatalytic reactions to occur.

[0139] The catalyst layer may also include organic materials such as polymers to improve durability and adhesion to the substrate.

[0140] The catalyst layer provided on the cathode preferably has high hydrogen generation capacity, and preferably contains nickel, cobalt, iron, and a platinum group element. To achieve this, the catalyst layer may contain a metal, a compound such as an oxide, a composite oxide or alloy composed of multiple metal elements, or a mixture thereof. Preferred catalyst layers are formed from Raney nickel, a Raney alloy composed of a combination of multiple materials (e.g., nickel and aluminum, nickel and tin), a porous coating prepared by plasma spraying a nickel compound or a cobalt compound, an alloy or composite compound of nickel and an element selected from cobalt, iron, molybdenum, silver, and copper, elemental metals and oxides of platinum group elements (e.g., platinum and ruthenium) having high hydrogen production capacity, a mixture of elemental metals or oxides of these platinum group element metals with a compound of another platinum group element (e.g., iridium or palladium) or a compound of a rare earth metal (e.g., lanthanum and cerium), and a carbon material (e.g., graphene).

[0141] To provide greater catalytic activity and durability, the above materials may be stacked in multiple layers or may be included in a catalyst layer.

[0142] Organic materials such as polymeric materials may be included to improve durability or adhesion to the substrate.

[0143] In so-called zero-gap electrolysis cells, the electrodes are placed in direct contact with the separator, thereby reducing the space between them. Mesh or porous electrodes are used to allow the separator to fill with electrolyte and efficiently remove the oxygen and hydrogen gases that form. Such zero-gap electrolysis cells have been observed to operate at higher current densities.

[0144] A typical alkaline water electrolyser contains several electrolysis cells, also called a stack of electrolysis cells as described above. [Example]

[0145] material All materials used in the following examples were readily available from standard sources such as Aldrich Chemical Co (Belgium) and Acros (Belgium) unless otherwise stated. Water used was deionized water.

[0146] PPS-cloth-1, a 100 μm thick polyphenylene sulfide woven fabric.

[0147] PPS-Cloth-2, a 300 μm thick polyphenylene sulfide woven fabric.

[0148] Zr02, zirconium oxide particles having a D50 particle size of approximately 0.70 μm as measured with a Mastersizer available from Malvern Panalytical.

[0149] Polysulfone, Udel P1700 NT LCD, polysulfone resin available from SOLVAY.

[0150] Glycerol, a pore expander commercially available from MOSSELMAN.

[0151] NEP, N-ethyl-pyrrolidone commercially available from BASF.

[0152] NBP, N-butyl-pyrrolidone commercially available from Taminco.

[0153] measurement Flatness / Waviness The flatness / waviness of the separator was evaluated by visual inspection.

[0154] Figure 4 shows the waviness observed for S1 and S2.

[0155] viscosity 100s -1 The viscosity of the dope solution at 20°C was measured using a Kinexus LAB+ Rheometer available from Malvern Panalytical using the "Cup & Bob" configuration.

[0156] Example 1 Preparation of separators S-1 to S-3 A dope solution was prepared by mixing the ingredients in Table 1. [Table 1]

[0157] 100 s measured as described above -1 The viscosity of the dope solution at this temperature is shown in Table 1.

[0158] Separators S-1 to S-3 were prepared as shown schematically in FIG.

[0159] The dope solution was coated on both sides of a 1.3 m wide PPS fabric according to Table 2 using a slot die coating technique at 3 m / min.

[0160] The coated substrate was then transported towards a water bath (coagulation bath, 800) maintained at 65°C.

[0161] Before entering the water bath, the VIPS step was performed in a closed area (400, d = 7 cm, RH = 98%, ventilation).

[0162] The coated support was then placed in a water bath for 2 minutes, during which time liquid-induced phase separation (LIPS) occurred.

[0163] After an in-line washing step in water at 70° C. for 5 minutes, the resulting separator was rolled up without drying and then cut into the desired format.

[0164] The resulting separators S-1 to S-3 had the total thickness shown in Table 2.

[0165] The flatness / waviness of the separator evaluated as described above is shown in Table 2. [Table 2]

[0166] From the results in Table 2, the applied dope solution -1 It is clear that a separator comprising a thin fabric of 150 μm or less has sufficient flatness / waviness when it has a viscosity of at least 20 Pa.s measured at a temperature of 20° C.

[0167] For separators with thicker fabrics (e.g., 300 μm), the flatness / waviness is determined when the viscosity of the dope solution is 100 s -1 , even if it is less than 20 Pa.s measured at a temperature of 20°C, it is still considered to be satisfactory.

Claims

1. A separator (1) for alkaline electrolysis comprising a porous support (10) and first (20b) and second (30b) porous layers provided on one and the other sides of the porous support, respectively, wherein the porous support has a thickness (d1) of 150 μm or less, and the separator has a thickness (d2) of less than 250 μm.

2. 2. The separator according to claim 1, wherein the thickness of the porous support is 100 μm or less.

3. 3. The separator of claim 1 or 2, wherein the separator has a thickness of less than 225 μm.

4. 0.1 ohm cm in 30 wt % aqueous KOH at 80°C ２ The separator of any one of claims 1 to 3, having an ionic resistance of less than 0.05%.

5. The separator of any one of claims 1 to 4, wherein the open area of the porous support is from 30 to 80%.

6. The separator according to any one of claims 1 to 5, wherein the first and second porous layers comprise a polymer resin and hydrophilic inorganic particles.

7. 7. The separator according to claim 6, wherein the polymer resin is at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfide.

8. 8. The separator according to claim 6, wherein the hydrophilic inorganic particles are selected from at least one of the group consisting of zirconium oxide, zirconium hydroxide, magnesium oxide, magnesium hydroxide, titanium oxide, titanium hydroxide, and barium sulfate.

9. The separator of claim 8, wherein the hydrophilic inorganic particles have a particle size D50 of 0.7 μm or less.

10. The separator according to any one of claims 1 to 9, wherein the first porous layer and the second porous layer are the same.

11. A method for producing a separator for alkaline water electrolysis, comprising: - applying a dope solution comprising a polymeric resin, hydrophilic inorganic particles and a solvent to both sides of the porous support; performing a phase inversion on the applied dope solution, thereby forming first and second porous layers on one and the other side of the porous support; The porous support has a thickness (d1) of 150 μm or less, the separator has a thickness (d2) of less than 250 μm, and the shear rate is 100 s －１ and the viscosity of the dope solution measured at a temperature of 20°C is at least 20 Pa.s.

12. 12. The method of claim 11, wherein the solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N-butyl-2-pyrrolidone, N,N-dimethyl-formamide (DMF), formamide, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), and acetonitrile.

13. The method of claim 12, wherein the solvent is N-butyl-2-pyrrolidone.

14. The method according to any one of claims 11 to 13, wherein the phase inversion process comprises a vapor induced phase separation (VIPS) process and a liquid induced phase separation (LIPS) process.

15. An alkaline water electrolysis apparatus comprising a separator as defined in any one of claims 1 to 10 located between a cathode and an anode.

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