Separator for alkaline water electrolysis

Abstract

To provide a separator with sufficient mechanical quality and improved ion conductivity. [Solution] A separator for alkaline electrolysis comprising a porous support (10) and first (20b) and second (30b) porous layers provided on one side and the other side of the porous support, characterized in that 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. A method for preparing such a separator is also disclosed.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing 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, as a raw material in the chemical industry and as a reducing agent in the metallurgical industry. Hydrogen is a fundamental building block for the production of ammonia, and by extension, methanol, which is used in the manufacture of fertilizers and many polymers. Another area of ​​use is refineries, where hydrogen is used to process intermediate oil products.

[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. During such a combustion reaction, no greenhouse gases, including carbon, are emitted.

[0004] To realize a low-carbon society, renewable energy sources such as solar and wind power are becoming increasingly important.

[0005] Electricity generation from wind and solar power systems is highly dependent on weather conditions, leading to significant fluctuations and an imbalance between electricity supply and demand. So-called electricity-to-gas technology, where electricity is used to generate gaseous fuels such as hydrogen for storage, has attracted considerable attention in recent years. As the generation of electricity from renewable energy sources increases, so does the demand for storing and transporting the generated energy.

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

[0007] In alkaline water electrolysis cells, a so-called separator or diaphragm is used to separate electrodes of different polarities, preventing short circuits between these electron-conducting components (electrodes) and avoiding gas crossover, thereby preventing the recombination of hydrogen (formed at the cathode) and oxygen (formed at the anode). While performing all these functions, the separator should also be a high ionic conductor for the transport of hydroxyl ions from the cathode to the anode.

[0008] The separator typically includes a porous support. Such a porous support, as disclosed in Patent Document 1 (Hydrogen Systems), reinforces the separator and facilitates the operation of the separator and its introduction into the electrolytic cell.

[0009] Patent document 2 (VITO) discloses a process for preparing a reinforced separator. This process results in a film having symmetrical properties. The process includes the steps of providing a porous support as a web and a suitable doping solution; guiding the web into a vertical position; equally coating both sides of the web with the doping solution to produce a web-coated support; and applying a symmetrical surface pore formation step and a symmetrical solidification step to the doped web to produce a reinforced film.

[0010] Patent documents 3 and 4 (Agfa Gevaert and VITO) disclose manufacturing methods for producing reinforced films having symmetrical properties as described in Patent Document 2. The porous supports used in these manufacturing methods have a thickness of more than 190 μm.

[0011] However, porous supports can reduce ion conductivity through the separator, and therefore, the efficiency of the electrolytic process may decrease.

[0012] Therefore, a separator with sufficient mechanical quality combined with high ionic conductivity is required. [Prior art documents]

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0014] An object of the present invention is to provide a separator having sufficient mechanical quality 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] A further object of the present invention will become apparent from the following description.

Brief Description of the Drawings

[0018] [Figure 1] One aspect of the separator according to the present invention is schematically shown. [Figure 2] One aspect of the method for manufacturing the separator according to the present invention is schematically shown. [Figure 3] Another aspect of the method for manufacturing the separator according to the present invention is schematically shown. [Figure 4] The undulations observed on the separator prepared in the example are shown. (Fig. 4A = S1; Fig. 4B = S2).

Modes for Carrying Out the Invention

[0019] Separator for alkaline water electrolysis The separator (1) for alkaline electrolysis according to the present invention includes a porous support (10) and first (20b) and second (30b) porous layers provided on each of one side and the other side of the porous support, and 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. When the thickness of the separator is less than 100 μm, its physical strength may be insufficient, and when the thickness exceeds 250 μm, the electrolysis efficiency may decrease.

[0021] The separator preferably has an ion resistance of less than 0.1 ohm cm, more preferably less than 0.07 ohm cm, in a 30 wt% aqueous KOH solution at 80 °C. 2 less, and more preferably less than 0.07 ohm cm 2 and has an ion resistance of less than that.

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

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

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

[0025] When a doping solution is applied to both sides of a porous support, the doping solution impregnates the support. Preferably, the porous support is completely impregnated with the doping solution.

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

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

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

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

[0030] The pore size of the separator must be sufficiently small to prevent recombination of hydrogen and oxygen by avoiding gas crossover. On the other hand, a larger pore size is preferable to ensure efficient transport of hydroxyl ions from the cathode to the anode. Efficient transport of hydroxyl ions requires efficient penetration of the electrolyte into the separator.

[0031] The maximum pore size (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 separator may have the same or different maximum pore diameters on both sides.

[0033] Preferred separators having the same pore diameter on both sides are disclosed in the aforementioned 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 lower PDmax(1) ensures efficient separation of hydrogen and oxygen, while a lower PDmax(2) ensures good penetration of the electrolyte into the separator, resulting in sufficient ionic conductivity.

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

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

[0037] porous support Porous supports are used to reinforce separators and ensure their 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, in order 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 porous cloth, porous metal plate, and porous ceramic plate.

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

[0043] Porous polymer fabrics can be woven or nonwoven. Woven fabrics typically have better dimensional stability and uniformity of open areas and thickness. However, the manufacture of woven fabrics with a thickness of 100 μm or less is more complex and results in a more expensive fabric. The manufacture of nonwoven fabrics is relatively less complex, even for fabrics with a thickness of 100 μm or less. Also, nonwoven fabrics may have larger open areas.

[0044] The openings of the porous support are 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 and tetrafluoroethylene (ETFE) or chlorotrifluoroethylene (ECTFE), polyimides, polyetherimides, and m-aramids.

[0046] The preferred polymer fabric is prepared from polypropylene (PP) or polyphenyl sulfide (PPS), most preferably polyphenyl sulfide (PPS).

[0047] Polyphenylene sulfide-based porous supports exhibit high resistance to high temperatures and high-concentration alkaline solutions, as well as high chemical stability against reactive oxygen species generated from the anode during water electrolysis processes. It possesses qualitative properties. Furthermore, 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 / cm³. 3 That is the case.

[0049] The porous support is preferably a continuous web that enables manufacturing processes such as those disclosed in Patent Documents 2 and 3.

[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 contains a polymer resin.

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

[0053] Polymer resins 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). Polymer resins may be used alone, or two or more 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 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 the 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 doping solution may become 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 Furthermore, 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, paragraph

[0040] ~

[0063] It is disclosed to [the relevant authority].

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

[0064] Other hydrophilic particles that may be used are nitrides and carbides of Group IV elements in 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 or intermediate value of the particle size distribution. The D50 particle size is the particle size value of 50% in the cumulative distribution. For example, if D50 = 0.1 μm, then 50% of the particles are larger than 1.0 μm and 50% are smaller than 1.0 μm.

[0067] The D50 particle size is preferably measured using laser diffraction, for example, with 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, and more preferably at least 75% by weight.

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

[0070] Preparation of separators The preferred method for preparing the separator described above is: - The following steps involve applying the doping solution described below to both sides of the porous support; - The process includes the step of performing a phase inversion on the applied doping solution, thereby forming first and second porous layers on one and the other side of the porous support, The porous support has a thickness of 150 μm or less (d1), the separator has a thickness of 250 μm or less (d2), and the shear rate is 100 s. -1 Furthermore, the viscosity of the doped solution, measured at a temperature of 20°C, is characterized by 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 manufacturing reinforced separators are disclosed in Patent Documents 2 and 3 relating to symmetrical separators, and in European Patent Application Publication No. 3652362 relating to asymmetrical 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] Other manufacturing methods that may be used are disclosed in European Patent Application Publication No. 3272908.

[0073] dope solution The doping solution preferably comprises a polymer resin as described above, hydrophilic particles as described above, and a solvent.

[0074] The solvent in the doping solution is preferably an organic solvent capable of dissolving the polymer resin. Furthermore, the organic solvent is preferably miscible with water.

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

[0076] For health and safety reasons, N-butylpyrrolidone (NBP) is a very preferred solvent.

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

[0078] The doping solution preferably contains additives for optimizing the pore size on the surface and inside the porous layer. Such additives may be organic or inorganic compounds, or combinations thereof.

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

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

[0081] Preferred polyethylene glycol has a molecular weight of 10,000 to 50,000, preferred polyethylene oxide has a molecular weight of 50,000 to 300,000, and preferred polyvinylpyrrolidone has a molecular weight of 30,000 to 100,000.

[0082] Glycerol is a particularly preferred organic compound that can influence pore formation in the porous layer.

[0083] The amount of compounds that may affect pore formation is preferably 0.1 to 15% by weight, more preferably 0.5 to 5% by weight, relative to the total weight of the doped 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 doping solutions provided on both sides of the porous support may be the same or different.

[0087] Application of doping solution The doping solution may be applied to the surface of a substrate, preferably a porous support, by either a coating or casting technique.

[0088] The preferred coating technique is extrusion coating.

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

[0090] A slot coating die can maintain the doping solution at a predetermined temperature, uniformly distribute the doping solution onto a support, and adjust the coating thickness of the applied doping solution.

[0091] shear rate 100s -1 Furthermore, the viscosity of the doped 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 doping solution is preferably shear-thinning. Shear rate 100 s -1 Shear rate 1s for viscosity -1 The viscosity ratio 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 Figures 2 and 3.

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

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

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

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

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

[0099] The phase inversion process preferably includes 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 includes 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 doping solution is brought into contact with a non-solvent that is miscible with the solvent in the doping solution.

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

[0103] The non-solvent is preferably water, water and N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DM A mixture with an aprotic solvent selected from the group consisting of AC), 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 transfer 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 doping solution into the porous support results in sufficient adhesion of the resulting hydrophilic layer onto the porous support.

[0107] In a preferred embodiment, a continuous web (100) coated on both sides with a doping solution is transported vertically downward toward a coagulation bath (800), as shown in Figures 2 and 3.

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

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

[0110] In the manufacturing method shown in Figure 2, VIPS is performed in region 400 between the slot coating die (200, 300) and the non-solvent surface in the solidification bath (800), and this region 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, relative humidity and temperature of the air, and exposure time.

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

[0113] The relative humidity within the VIPS region (400) may be adjusted by the temperature of the solidification bath, as well as by shielding the VIPS region (400) from the environment and the solidification bath.

[0114] The air velocity may be adjusted by the rotation 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, which result in a second porous polymer layer, may be the same (Figure 2) or different (Figure 3).

[0116] A washing step may be performed after the phase inversion step, preferably the LIPS step in the solidification bath.

[0117] It is preferable to perform a drying step after a phase inversion step or an optional cleaning step. Manufacturing of separators

[0118] Figures 2 and 3 schematically show preferred embodiments for manufacturing 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 downward in a vertical position between the two coating units (200) and (300).

[0121] In these coating units, a dope solution is coated on both sides of the web. The coating thickness on both sides of the web may be adjusted by optimizing the viscosity of the dope solution and the distance between the coating unit and the surface of the web. A preferred coating unit is described in European Patent Application Publication No. 2296825, paragraphs

[0043] ,

[0047] ,

[0048] ,

[0060] ,

[0063] , and Figure 1.

[0122] Next, the web, coated on both sides with the doping solution, is transported downward over a distance d toward the coagulation bath (800).

[0123] The LIPS process is carried out in the coagulation bath.

[0124] The VIPS process is performed within the VIPS region before entering the coagulation bath. In Figure 2, the VIPS region (400) is identical on both sides of the coated web, whereas in Figure 3, the VIPS regions (400(1)) and (400(2)) are different on both sides of the coated web.

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

[0126] In Figure 3, VIPS regions (400(1)) and (400(2)) are distinct from each other. VIPS region (400(1)) on one side of the coated web, which includes a metal plate (500(1)), is identical to VIPS region (400) in Figure 2. VIPS region (400(2)) on the other side of the coated web is distinct from region (400(1)). There is no metal plate shielding VIPS region (400(2)) from the environment. However, VIPS region (400(2)) is shielded from the solidification bath here by an insulating metal plate (500(2)). Furthermore, there is no ventilator within VIPS region 400(2). This results in VIPS region (400(1)) having higher RH and temperature compared to the other VIPS region (400(2)).

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

[0128] The RH within one VIPS region is preferably greater than 85%, more preferably greater than 90%, and most preferably greater than 95%, while the RH within 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 the winding system (700).

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

[0131] electrolytic cell The alkaline water electrolysis separator 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. The electrolyte is located between both electrodes.

[0133] When electrical energy (voltage) is applied to an electrolytic cell, the 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 move to the anode through the separator. The separator prevents the mixing of 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 20-40% by weight of the total weight of the electrolyte solution. The temperature of the electrolyte solution is preferably 50°C-120°C, more preferably 75°C-100°C.

[0135] The electrode typically includes a substrate on which a so-called catalyst layer is provided. The catalyst layer may differ between 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. Substrates may also be made from conductive alloys of two or more metals, or mixtures of two or more conductive materials. Preferred materials are nickel or nickel-based alloys. Nickel has good stability in strong alkaline solutions, good conductivity, and is relatively inexpensive.

[0137] The catalyst layer provided on the anode preferably has high oxygen generation capacity. The catalyst layer preferably contains nickel, cobalt, iron, and platinum group elements. The catalyst layer may contain these elements as elemental metals, compounds (e.g., oxides), composite oxides, or alloys composed of multiple metallic elements, or mixtures thereof. Preferred catalyst layers include plated nickel, nickel and cobalt or nickel and iron plated alloys, nickel and cobalt composite oxides such as LaNiO3, LaCoO3, and NiCo2O4, platinum group element compounds 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 high density of lattice defects, which serve as active sites for electrocatalytic reactions.

[0139] The catalyst layer may also contain organic substances 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. The catalyst layer preferably contains nickel, cobalt, iron, and platinum group elements. Desired activity and durability. To achieve this, the catalyst layer may contain metals, compounds such as oxides, composite oxides or alloys composed of multiple metal elements, or mixtures thereof. Preferred catalyst layers are formed from Raney nickel; Raney alloys composed of combinations of multiple materials (e.g., nickel and aluminum, nickel and tin); porous coatings produced by plasma spraying nickel compounds or cobalt compounds; alloys and composite compounds of nickel with elements selected from, for example, cobalt, iron, molybdenum, silver, and copper; elemental metals and oxides of platinum group elements (e.g., platinum and ruthenium) with high hydrogen-generating ability; mixtures of these platinum group elemental metals or oxides with compounds of other platinum group elements (e.g., iridium or palladium), or compounds of rare earth metals (e.g., lanthanum and cerium); and carbon materials (e.g., graphene).

[0141] To provide higher catalytic activity and durability, the above-mentioned materials may be laminated in multiple layers or incorporated into the catalyst layer.

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

[0143] In so-called zero-gap electrolytic cells, the electrodes are positioned in direct contact with the separator, thereby reducing the space between the two electrodes. Mesh-type or porous electrodes are used to allow the separator to be filled with electrolyte and to efficiently remove the formed oxygen and hydrogen gases. Such zero-gap electrolytic cells have been observed to operate at higher current densities.

[0144] A typical alkaline water electrolysis cell contains several electrolytic cells, also known as a stack of the electrolytic cells described above. [Examples]

[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 specified. Deionized water was used.

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

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

[0148] ZrO2, measured with a mastersizer available from Malvern Panalytical, is a zirconium oxide particle with a D50 particle size of approximately 0.70 μm.

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

[0150] Glycerol is a pore-dilating agent commercially available from MOSSELMAN.

[0151] N-ethylpyrrolidone, commercially available from NEP and BASF.

[0152] NBP, N-butylpyrrolidone, is a commercially available product from Taminco.

[0153] measurement Flatness / Waviness The flatness and curvature of the separators were evaluated by visual inspection.

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

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

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

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

[0158] Separators S-1 to S-3 were prepared as schematically shown in Fig. 2.

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

[0160] Next, the coated support was transported towards a water bath (coagulation bath, 800) maintained at 65 °C.

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

[0162] Next, the coated support was immersed in the water bath for 2 minutes, during which liquid-induced phase separation (LIPS) occurred.

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

[0164] The obtained Separators S-1 to S-3 had the total thicknesses 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 doping solution was 100s -1 When measured at a temperature of 20°C, if the viscosity is at least 20 Pa.s, it is clear that a separator containing a thin cloth of 150 μm or less has sufficient flatness / undulation.

[0167] For separators with thicker fabric (e.g., 300 μm), the flatness / wavyness is when the viscosity of the doping solution is 100 s -1 Even if measured at 20°C and the reading is less than 20 Pa.s, it is still considered sufficiently good.

Claims

1. A separator for alkali electrolysis (1) comprising a porous support (10) and first (20b) and second (30b) porous layers provided on one and the other side of the porous support, characterized in that 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. The separator according to claim 1, wherein the thickness of the porous support is 100 μm or less.

3. The separator according to claim 1 or 2, wherein the thickness of the separator is less than 225 μm.

4. 0.1 ohm cm in a 30 wt% KOH aqueous solution at 80°C ２ A separator according to any one of claims 1 to 3, having an ion resistance of less than 1.

5. A separator according to any one of claims 1 to 4, wherein the openings of the porous support are 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. The separator according to claim 6, wherein the polymer resin is at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenyl sulfide.

8. The separator according to claim 6 or 7, 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 according to 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 manufacturing a separator for alkaline water electrolysis, - A step of applying a doping solution containing a polymer resin, hydrophilic inorganic particles, and a solvent to both sides of a porous support; - A step of performing a phase inversion on the applied doping 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 A method characterized in that the viscosity of the doped solution measured at a temperature of 20°C is at least 20 Pa·s.

12. The method according to 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-dimethylformamide (DMF), formamide, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), and acetonitrile.

13. The method according to 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 step includes a vapor-induced phase separation (VIPS) step and a liquid-induced phase separation (LIPS) step.

15. Alkaline water electrolysis apparatus, comprising a separator positioned between the cathode and the anode, as defined in any one of claims 1 to 10.

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