Method for producing an ion-conducting membrane

Abstract

According to the present invention, there is provided a method for producing an ion-conducting membrane, the method comprising the steps of: (a) providing a substrate, (b) depositing a first dispersion on the substrate to form a first layer, the first dispersion comprising an ion-conducting polymer, (c) depositing a second dispersion on the first dispersion to form a second layer on the first layer, the second dispersion comprising an ion-conducting polymer, (d) providing a reinforcing component comprising pores such that the second dispersion impregnates at least a portion of the pores of the reinforcing component, and (e) drying the first layer and the second layer, where step (e) is performed after steps (c) and (d).

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an ion-conducting membrane, such as a proton exchange membrane. In particular, the present invention relates to a method for manufacturing an ion-conducting membrane for an electrochemical device, such as a fuel cell or an electrolyzer. The present invention also relates to an associated method for manufacturing a catalyst-coated ion-conducting membrane, and an associated method for manufacturing a membrane electrode assembly. [Background technology]

[0002] A fuel cell is an electrochemical cell that contains two electrodes separated by an electrolyte. A fuel, such as hydrogen or an alcohol, e.g., methanol or ethanol, is supplied to the anode, and an oxidant, such as oxygen or air, is supplied to the cathode. Electrochemical reactions occur at the electrodes, converting the chemical energy of the fuel and oxidant into electrical energy and heat. Electrocatalysts are used to facilitate the electrochemical oxidation of the fuel at the anode and the electrochemical reduction of oxygen at the cathode.

[0003] In a hydrogen- or alcohol-fueled proton exchange membrane fuel cell (PEMFC), the electrolyte is a solid polymer membrane that is electronically insulating and protonically conductive. Protons produced at the anode are transported across the membrane to the cathode, where they combine with oxygen to form water. The most widely used alcohol fuel is methanol, and this variation of the PEMFC is often called a direct methanol fuel cell (DMFC).

[0004] The main component of a PEMFC is known as a membrane electrode assembly (MEA) and is essentially composed of five layers. The central layer is a polymeric ion-conducting membrane. On either side of the ion-conducting membrane are electrocatalyst layers that contain electrocatalysts designed for specific electrocatalytic reactions. The electrocatalyst layers are electrically conductive. Finally, adjacent to each electrocatalyst layer is a gas diffusion layer. The gas diffusion layers must allow reactants to reach the electrocatalyst layers and must conduct the electrical current produced by the electrochemical reactions. The gas diffusion layers must therefore be porous and electrically conductive.

[0005] Conventionally, MEAs can be constructed by a number of methods, which are outlined below. (i) An electrocatalyst layer may be applied to the gas diffusion layer to form a gas diffusion electrode. Two gas diffusion electrodes can be placed on either side of an ion conductive membrane and stacked together to form a five-layer MEA. (ii) Electrode catalyst layers may be applied to both sides of the ion conductive membrane to form a catalyst coated ion conductive membrane, followed by application of gas diffusion layers to both sides of the catalyst coated ion conductive membrane. (iii) An MEA can be formed from an ion conductive membrane coated on one side with an electrocatalyst layer, a gas diffusion layer adjacent to the electrocatalyst layer, and a gas diffusion electrode on the opposite side of the ion conductive membrane.

[0006] Known construction methods typically involve heating the ion-conducting membrane to its glass transition temperature (T g ), which can damage the ion-conducting membrane and result in rejected products.

[0007] The polymeric ion-conducting membrane may include a reinforcing material, such as a planar porous material embedded within the thickness of the membrane, to improve the mechanical strength of the membrane and thus improve the durability of the MEA and the life of the fuel cell. MEAs that include reinforcing materials may be susceptible to membrane curl. It is desirable to avoid membrane curl.

[0008] Such polymer ion conducting membranes have also been applied to other electrochemical devices such as electrolysers. Electrolysis of water to produce high purity hydrogen and oxygen can be carried out in both alkaline and acid electrolyte systems using electrolysers. Acid electrolyte systems typically use solid proton conducting polymer electrolyte membranes and are known as polymer electrolyte membrane water electrolysers (PEMWEs). Within the cells of a PEMWE, a catalyst coated ion conducting membrane is used, which includes a (proton conducting) polymer electrolyte membrane with two catalyst layers (for the anode and cathode reactions, respectively) applied to both sides of the polymer electrolyte membrane. To complete the electrolysis cell, current collectors, typically metal meshes, are placed on either side of the catalyst coated ion conducting membrane. Such polymer ion conducting membranes used in electrolysers can be manufactured using the same or similar processes as those used to manufacture polymer ion conducting membranes for fuel cells and are subject to the same problems. Summary of the Invention

[0009] To facilitate the commercialization of electrochemical devices such as fuel cells and electrolysers, it is desirable to improve the manufacturing rate of ion-conducting membranes, which would increase the manufacturing rate of MEAs and improve manufacturing capacity and device throughput.

[0010] When producing a reinforced ion-conducting membrane, it is desirable for the reinforcing material to be embedded centrally within the thickness of the membrane. Typically, the production of a reinforced ion-conducting membrane involves at least three deposition and drying cycles, so that the reinforcing material can be centrally located within the thickness of the membrane. It is desirable to improve the efficiency of this process.

[0011] The present invention seeks to address at least some of the problems, desires, and needs described above. For example, the present invention provides a method for producing ion-conducting membranes, such as proton-conducting membranes, in a more efficient manner, thus increasing manufacturing throughput.

[0012] According to a first aspect of the present invention, there is provided a method of producing an ion-conducting membrane, the method comprising: (a) providing a substrate; (b) depositing a first dispersion on a substrate to form a first layer, the first dispersion comprising an ion-conducting polymer; (c) depositing a second dispersion onto the first dispersion to form a second layer on the first layer, the second dispersion comprising an ion-conducting polymer; (d) providing a reinforcing component comprising pores such that the second dispersion impregnates at least a portion of the pores of the reinforcing component; (e) drying the first layer and the second layer; Including, Step (e) is carried out after steps (c) and (d).

[0013] By depositing the second dispersion as a second layer on the first dispersion before the first dispersion dries (i.e., to form a second wet layer on the first wet layer), the number of separate heat drying steps required during the manufacturing process is reduced, allowing for more efficient production of ion conductive membranes.

[0014] The first and second dispersions are different. The first and second dispersions typically have different physical properties, such as density, to help reduce the mixing rate between the first and second layers. Preferably, the density of the first dispersion is greater than the density of the second dispersion.

[0015] According to a second aspect of the present invention, there is provided a method of producing a catalyst coated ion conducting membrane, comprising the steps of: Providing an ion-conducting membrane produced using the method according to the first aspect; applying a catalyst layer to the ion-conducting membrane; A method for producing a catalyst coated ion conducting membrane is provided, comprising:

[0016] According to a third aspect of the present invention, there is provided a method of manufacturing a membrane seal assembly, comprising the steps of: Providing an ion-conducting membrane produced using the method according to the first aspect, or providing a catalyst-coated ion-conducting membrane produced using the method according to the second aspect; and applying a sealing component to the ion conductive membrane or catalyst coated ion conductive membrane; A method of manufacturing a membrane seal assembly is provided, comprising:

[0017] According to a fourth aspect of the present invention, there is provided a method for producing a membrane-electrode assembly, comprising the steps of: Providing an ion-conducting membrane produced using the method according to the first aspect; applying a gas diffusion electrode to the ion-conducting membrane; A method for producing a membrane-electrode assembly is provided, comprising:

[0018] According to a fifth aspect of the present invention, there is provided a method for producing a membrane-electrode assembly, comprising the steps of: Providing a catalyst coated ion conducting membrane according to the second aspect; applying a gas diffusion layer to the catalyst coated ion conductive membrane; A method for producing a membrane-electrode assembly is provided, comprising:

[0019] According to a sixth aspect, there is provided a method for producing a membrane-electrode assembly, comprising the steps of: Providing a membrane seal assembly according to a third aspect; applying a gas diffusion electrode to the membrane seal assembly; A method for producing a membrane-electrode assembly is provided, comprising:

[0020] According to a seventh aspect of the present invention there is provided an ion-conducting membrane for use in an electrochemical device obtainable using the method according to the first aspect.

[0021] Although the invention has been described above, the invention extends to any combination of the features set out above or in the following description, drawings or claims. For example, any feature disclosed in connection with one aspect of the invention may be combined with any feature of another aspect of the invention. [Brief description of the drawings]

[0022] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] 1 illustrates an exemplary method according to an embodiment of the present invention. [Diagram 2] 1 illustrates an exemplary method according to an embodiment of the present invention. [Diagram 3] FIG. 1 is an illustration of a deposition process in which a first and second layer are deposited simultaneously. [Figure 4] A second layer is shown over the first layer, the density of the second layer being less than the density of the first layer. [Diagram 5] A second layer is shown over the first layer, the second layer having a lower ionomer concentration than the first layer. [Figure 6] A second layer is shown over the first layer, the density of the second layer being less than the density of the first layer. [Figure 7] 1 is a scanning electron microscope (SEM) photograph of a cross section of an ion-conducting membrane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention provides a method for producing an ion-conducting membrane, such as a proton exchange membrane, which may be suitable for an electrochemical device, such as a fuel cell or an electrolyzer. The method comprises: (a) providing a substrate; (b) depositing a first dispersion on a substrate to form a first layer, the first dispersion comprising an ion-conducting polymer; (c) depositing a second dispersion onto the first dispersion to form a second layer on the first layer, the second dispersion comprising an ion-conducting polymer; (d) providing a reinforcing component comprising pores such that the second dispersion impregnates at least a portion of the pores of the reinforcing component; (e) drying the first layer and the second layer; Including, Step (e) is carried out after steps (c) and (d).

[0024] It will be apparent to those skilled in the art that many variations of the basic process above are possible, some of which are described in more detail below with reference to the drawings, but all such variations, whether or not explicitly described, are within the scope of the present invention.

[0025] By depositing the second dispersion as a second wet layer onto the first dispersion before the first dispersion dries, the number of separate heating and drying steps required during the manufacturing process is reduced. As a result, the method allows the ion-conducting membrane to be manufactured more quickly. Also, by using fewer heating and / or drying steps, the risk of damaging the ion-conducting membrane during manufacturing is reduced. This can result in a more reliable manufacturing process with fewer rejects.

[0026] The term "dispersion" as used herein means a system in which a dispersed phase (e.g. solid particles) is dispersed in a (liquid) continuous phase. The dispersed phase comprises an ion-conducting polymer. The continuous phase comprises one or more solvents.

[0027] The first and second dispersions typically have different physical properties, such as density, which can help the second dispersion form a separate layer on the first dispersion and can help reduce intermixing between the first and second layers prior to drying.

[0028] For example, one method is to control the relative density of the first and second dispersions. Preferably, the density of the first dispersion is greater than that of the second dispersion. The density of the second dispersion may be at least 0.5%, preferably at least 1%, more preferably at least 5% less than the density of the first dispersion, measured at 20° C. A lower density second dispersion can be deposited on top of the first dispersion such that the second dispersion floats on top of the first dispersion. Thus, the second dispersion forms a separate second layer on the first layer. The first and second layers remain as separate layers at least prior to the drying step. The laminated structure of the first and second layers is maintained for a time scale at least long enough for the drying step to be carried out. The drying step is typically initiated less than 10 minutes, preferably less than 3 minutes, more preferably less than about 1 minute, and most preferably less than about 30 seconds after the second dispersion is deposited. The first and second layers can be dried simultaneously. The layer may be dried at a temperature ranging from 50°C to 100°C, preferably from 60°C to 80°C inclusive.

[0029] Another method is to control the viscosity of the first and second dispersions. For example, if the viscosity of the first and / or second dispersion is high enough when the dispersions are deposited to form the first and second layers, respectively, the mixing speed between the first and second dispersions can be slowed down sufficiently so that the first and second layers remain as separate layers at least before the drying step. That is, the laminated structure of the first and second layers is maintained at least for a time scale long enough for the drying step to be performed.

[0030] A further method is to control the relative concentration of the ion-conducting polymer in the first and second dispersions. Preferably, the concentration of the ion-conducting polymer in the second dispersion is lower than the concentration of the ion-conducting polymer in the first dispersion. In this way, the second dispersion can be deposited onto the first dispersion to form two separate layers. The first and second layers can remain as separate layers at least on a time scale long enough for the drying step to be performed.

[0031] The first and second dispersions form separate layers, but some mixing may occur at the interface between the first and second dispersions. Such mixing may form a mixed layer at the interface. The blended layer comprises a mixture of the first and second dispersions. Preferably, there is minimal mixing between the first and second dispersions. The first and second dispersions remain as substantially separate wet layers. Preferably, the first and second layers remain as substantially separate layers when dry.

[0032] The first layer and the second layer form a layered structure. The layered structure may be metastable. For example, when a suitably high shear force is applied, the layered structure may be destroyed.

[0033] Reinforcing ingredients The method includes a step of providing a reinforcing component prior to the step of drying the first and second layers (i.e. prior to step (e)). The reinforcing component is preferably provided in the second layer. Preferably, the reinforcing component is a planar reinforcing component. The reinforcing component comprises pores. The second dispersion impregnates at least some of the pores of the reinforcing component. The reinforcing component becomes part of the second layer. Preferably, the second dispersion impregnates most (more preferably all) of the pores of the reinforcing component. For example, the second dispersion may impregnate at least 50%, preferably at least 75%, more preferably at least 90% of the pores of the reinforcing component (as a percentage of the total number of pores of the reinforcing component). The second dispersion may impregnate at least 50%, preferably at least 75%, more preferably at least 90% of the pore volume of the reinforcing component.

[0034] Preferably, the reinforcing component is provided in the second dispersion after the second dispersion is deposited on the first layer. That is, it is preferred to perform step (d) after step (c). Alternatively, the reinforcing component can be provided in the second dispersion such that the second dispersion impregnates at least a portion of the pores of the reinforcing component before the step of depositing the second dispersion on the first dispersion. That is, step (d) can be performed before step (c). In this case, the reinforcing component and the second dispersion can be deposited together on the first dispersion such that the second layer comprises the second dispersion and the reinforcing component.

[0035] The reinforcing component can provide mechanical strength to the ion-conducting membrane. The reinforcing component can include a porous reinforcing material, such as an expanded polytetrafluoroethylene (ePTFE) material, or a nanofiber network, such as a network including polybenzimidazole (PBI) fibers or glass fibers. The reinforcing component can include a plurality of openings, for example, as described in WO 2016 / 083785 A1.

[0036] The reinforcing component can have a thickness substantially the same as the thickness of the second layer, which can help control the position of the reinforcing component in the z-direction (i.e., in the through-plane direction).

[0037] The second dispersion can have a higher degree of wetting towards the reinforcing component than the first dispersion. This can substantially inhibit the first dispersion from impregnating the pores of the reinforcing component. "Wetting degree" (also called "wettability") is a measure of how well a liquid wets a surface (i.e., how well a liquid spreads across a surface). Wetting degree can be determined by measuring the contact angle of the liquid on the surface. The contact angle can be measured using known techniques, such as using a contact angle meter at room temperature. For example, the contact angle can be measured using a PCA-11 contact angle meter commercially available from Kyowa Interface Science Co., Ltd., Saitama, Japan. The larger the contact angle (up to 180°), the lower the wettability. The smaller the contact angle, the higher the wettability. The second dispersion can have a smaller contact angle towards the reinforcing component than the first dispersion, measured at a temperature of 25° C. using a contact angle meter.

[0038] The second dispersion can be substantially completely wettable towards the reinforcing component. For example, the second dispersion can have a contact angle of less than 90° towards the reinforcing component when measured using a contact angle meter at a temperature of 25°C. The surface tension of the second dispersion can be sufficiently low to completely wet the reinforcing component. For example, the second dispersion can have a surface tension of less than about 38 mN / m, preferably less than about 28 mN / m, more preferably less than about 24 mN / m when measured at a temperature of 25°C. The surface tension can be measured using a tensiometer utilizing the Wilhelmy plate principle, as described in Vazquez, G et al., J.Chem, Eng.Data, 1995, 40, 611-614.

[0039] The first dispersion can be substantially non-wetting towards the reinforcing component. For example, the first dispersion can have a contact angle of more than 90° towards the reinforcing component when measured using a contact angle meter at a temperature of 25°C. The surface tension of the first dispersion can be sufficiently high so that the first dispersion is substantially non-wetting towards the reinforcing component. For example, the first dispersion can have a surface tension of more than about 30 mN / m, preferably more than about 38 mN / m, more preferably more than about 42 mN / m when measured at a temperature of 25°C. The surface tension can be measured using a tensiometer utilizing the Wilhelmy plate principle, as described in Vazquez, G et al., J.Chem, Eng.Data, 1995, 40, 611-614. Preferably, the first dispersion does not impregnate the pores of the reinforcing component. For example, by using a first dispersion with a suitably low alcohol content and / or a suitably high water content (in weight percent based on the total weight of the continuous phase of the dispersion), the first dispersion can be substantially prevented from impregnating the pores of the reinforcing component. This allows the reinforcing component to be placed directly on the first layer without permeating the first layer. As a result, the position of the reinforcing component in the z-direction (i.e., in the planar direction) can be reliably controlled. In this way, membrane curl can be reduced or eliminated while also improving the efficiency of the manufacturing process. Furthermore, by providing an ion-conducting first layer separate from the reinforcing component, the ion conductivity across the ion-conducting membrane can be improved.

[0040] First Dispersion The first dispersion is a first ion-conducting membrane layer dispersion. The first dispersion comprises a continuous phase comprising one or more solvents. The first dispersion may comprise a continuous phase comprising (or consisting of) water, a polar solvent (other than water), or (preferably) a mixture thereof. The polar solvent may be a polar protic solvent. Preferably, the polar solvent is an alcohol, more preferably a C 1~4 It is an alcohol. 1~4The alcohol may be methanol, ethanol, propan-1-ol, propan-2-ol, n-butanol, iso-butanol, butan-2-ol, and tert-butyl alcohol, or a mixture thereof. 1~4 The alcohol is ethanol and / or propan-1-ol. Most preferably, 1~4 The alcohol is ethanol. Preferably, the continuous phase is water and C 1~4 More preferably, the continuous phase comprises (or consists essentially of) water and at least one of ethanol or propan-1-ol. Most preferably, the continuous phase comprises (or consists essentially of) water and ethanol.

[0041] The continuous phase of the first dispersion is a polar solvent other than water (e.g., C 1~4 The continuous phase may contain a polar solvent other than water in any combination of these range limits. Unless otherwise specified, the upper and lower limits of all numerical ranges disclosed in this application are included within the range.

[0042] The continuous phase of the first dispersion can contain water in an amount greater than 30% by weight, preferably in the range of 50 to 90% by weight, more preferably 60 to 80% by weight. The continuous phase can contain water in any combination of these range limits.

[0043] The first dispersion includes an ion-conducting polymer dispersed in a continuous phase. The ion-conducting polymer can be a proton-conducting polymer or an anion-conducting polymer, such as a hydroxyl anion-conducting polymer. Examples of suitable proton-conducting polymers include perfluorosulfonic acid ionomers (e.g., Nafion® (EI DuPont de Nemours and Co.), Aciplex® (Asahi Kasei), Aquivion™ (Solvay Speciality Polymers), Flemion® (Asahi Glass Co.), or ionomers based on sulfonated hydrocarbons, such as those available as fumapem® P, E or K series products from FuMA-Tech GmbH, JSR Corporation, Toyobo Corporation, etc. Examples of suitable anion-conducting polymers include A901 from Tokuyama and Fumasep FAA from FuMA-Tech GmbH.

[0044] The first dispersion may contain the ion-conducting polymer in an amount ranging from 5 to 80% by weight, preferably 10 to 50% by weight, more preferably 15 to 30% by weight, and most preferably 15 to 20% by weight, based on the total weight of the first dispersion. The first dispersion may contain the ion-conducting polymer in any combination of these range limits. For example, the first dispersion may contain the ion-conducting polymer in an amount ranging from 10 to 20% by weight.

[0045] Prior to step (e), the first layer is a first wet layer. Drying the first layer forms a first ion-conductive membrane layer, which is typically non-conductive. Suitably, the first layer (and thus the first ion-conductive membrane layer) is unreinforced (i.e. does not include a reinforcing component).

[0046] Second Dispersion The second dispersion is a second ion-conducting membrane layer dispersion. The second dispersion may include a continuous phase that includes (or consists of) water, a polar solvent (other than water), or (preferably) a mixture thereof. The polar solvent may be a polar protic solvent. Preferably, the polar solvent is an alcohol, more preferably a C 1~4 It is an alcohol. 1~4 The alcohol may be methanol, ethanol, propan-1-ol, propan-2-ol, n-butanol, iso-butanol, butan-2-ol, and tert-butyl alcohol, or a mixture thereof. 1~4 The alcohol is ethanol and / or propan-1-ol. Preferably, the continuous phase is water and C 1~4 More preferably, the continuous phase comprises (or consists essentially of) water and at least one of ethanol or propan-1-ol. Most preferably, the continuous phase comprises (or consists essentially of) water and ethanol.

[0047] The continuous phase of the second dispersion contains a higher weight percent of a polar solvent other than water (e.g., C 1~4 Alcohol).

[0048] The continuous phase of the second dispersion may include a lower weight percent of water than the continuous phase of the first dispersion, based on the total weight of each continuous phase.

[0049] The continuous phase of the second dispersion comprises a polar solvent other than water (e.g., C 1~4 Alcohol).

[0050] The continuous phase of the second dispersion can comprise water in an amount ranging from 0 to 50% by weight, preferably 10 to 40% by weight, and most preferably 20 to 30% by weight, based on the total weight of the continuous phase. The continuous phase can comprise water and non-water polar solvents in any combination of these ranges.

[0051] The second dispersion includes an ion-conducting polymer dispersed in the continuous phase. The ion-conducting polymer can be a proton-conducting polymer or an anion-conducting polymer, such as a hydroxyl anion-conducting polymer. Examples of suitable proton-conducting polymers include perfluorosulfonic acid ionomers (e.g., Nafion® (EI DuPont de Nemours and Co.), Aciplex® (Asahi Kasei), Aquivion™ (Solvay Speciality Polymers), Flemion® (Asahi Glass Co.), or ionomers based on sulfonated hydrocarbons, such as those available as fumapem® P, E or K series products from FuMA-Tech GmbH, JSR Corporation, Toyobo Corporation, etc. Examples of suitable anion-conducting polymers include A901 from Tokuyama and Fumasep FAA from FuMA-Tech GmbH. The ion-conducting polymers of the first and second dispersions can be the same or different.

[0052] The second dispersion may include the ion-conducting polymer in an amount ranging from 5 to 80% by weight, preferably 10 to 50% by weight, preferably 15 to 30% by weight, and most preferably 15 to 20% by weight, based on the total weight of the second dispersion. The second dispersion may include the ion-conducting polymer in any combination of these range limits. For example, the second dispersion may include the ion-conducting polymer in an amount ranging from 10 to 20% by weight. The first and second dispersions may include the ion-conducting polymer in substantially the same or different weight percents, based on the total weight of the respective dispersions. The first dispersion may include a different (i.e., higher or lower) weight percent of the ion-conducting polymer than the second dispersion, based on the total weight of the respective dispersions.

[0053] Prior to step (e), the second layer is a second wet layer. Drying the second layer forms a second ion-conducting membrane layer, which is typically non-conductive.

[0054] Steps (b) and (c) The first dispersion and the second dispersion can be deposited simultaneously. That is, the first dispersion can be deposited on the substrate at the same time as the second dispersion is deposited on the first dispersion. By depositing the first and second dispersions simultaneously, the manufacturing efficiency, manufacturing speed, and therefore the manufacturing capacity and throughput can be significantly improved.

[0055] The first and second dispersions can be independently deposited using a slot die (slot, extrusion) coating method (whereby the dispersion is squeezed onto the substrate by gravity or under pressure through a slot), knife coating, bar coating, inkjet printing, gravure printing, curtain coating, or spray coating method. These exemplary techniques can substantially avoid mixing between the first and second dispersions. The first and second dispersions can be deposited using the same or different techniques. Preferably, the first and second dispersions are deposited using a slot die coating method. More preferably, the first and second dispersions are deposited using a dual slot die coating method. The slot die coating method can include providing a slot die head including a first outlet and a second outlet. The first dispersion can be deposited onto the substrate through the first outlet. The second dispersion can be deposited onto the first dispersion through the second outlet. Slot die coating (or dual slot die coating) can provide a suitable method for depositing a second dispersion onto a first dispersion while minimizing turbulence and therefore mixing between the first and second layers.

[0056] Process (e) Step (e) is carried out after both steps (c) and (d). Step (e) comprises drying both the first and second layers. Step (e) suitably comprises removing substantially all of the solvent from the first and second layers.

[0057] Third Dispersion The method is: (f) depositing a third dispersion onto the second layer to form a third layer, the third dispersion comprising an ion-conducting polymer; (g) drying the third layer; It may further include.

[0058] Typically, the third dispersion is deposited after the step of drying the first and second layers (i.e. after step (e)). Alternatively, the third dispersion can be deposited on the second dispersion to form a third (wet) layer on the second (wet) layer. The step of drying the third layer forms a third ion-conductive membrane layer, which is typically non-conductive. Suitably, the third layer (and thus the third ion-conductive membrane layer) is unreinforced (i.e. does not include a reinforcing component).

[0059] The step of drying the first, second and third layers can form a three-layer ion-conducting membrane. The three-layer ion-conducting membrane includes a dried first layer, a dried second layer and a dried third layer, the dried second layer being disposed between the dried first layer and the third layer. The dried second layer includes a reinforcing component. Preferably, the dried first and third layers are not reinforced. The three-layer ion-conducting membrane can be non-conductive. The three-layer ion-conducting membrane can be suitable for use as an ion-conducting electrolyte in a fuel cell or a water electrolysis cell. That is, the ion-conducting membrane can be an electrolyte membrane.

[0060] If the second dispersion impregnates only some but not all of the pores of the reinforcing component, the third dispersion can impregnate the remaining unimpregnated pores of the reinforcing component. The third dispersion can have the same or a different composition as the first or second dispersion.

[0061] The third dispersion is a third ion-conducting membrane layer dispersion. The third dispersion can include a continuous phase that includes (or consists of) water, a polar solvent (other than water), or a mixture thereof. The polar solvent can be a polar protic solvent. Preferably, the polar solvent is an alcohol, more preferably a C 1~4 It is an alcohol. 1~4 The alcohol may be methanol, ethanol, propan-1-ol, propan-2-ol, n-butanol, iso-butanol, butan-2-ol, and tert-butyl alcohol, or a mixture thereof. 1~4The alcohol is ethanol and / or propan-1-ol. Preferably, the continuous phase is water and C 1~4 More preferably, the continuous phase comprises (or consists essentially of) water and at least one of ethanol or propan-1-ol. Most preferably, the continuous phase comprises (or consists essentially of) water and ethanol. The continuous phase of the third dispersion can have the same composition as the first or second dispersion.

[0062] The continuous phase of the third dispersion is a polar solvent other than water (e.g., C 1~4 Alcohol) in an amount of more than 40% by weight, preferably in the range of 50 to 90% by weight, or more preferably in the range of 70 to 80% by weight.

[0063] The continuous phase of the third dispersion may comprise water in an amount less than 60% by weight, preferably in the range of 10-50% by weight, more preferably 20-30% by weight.

[0064] The third dispersion includes an ion-conducting polymer dispersed in the continuous phase. The ion-conducting polymer can be a proton-conducting polymer or an anion-conducting polymer, such as a hydroxyl anion-conducting polymer. Examples of suitable proton-conducting polymers include perfluorosulfonic acid ionomers (e.g., Nafion® (EI DuPont de Nemours and Co.), Aciplex® (Asahi Kasei), Aquivion™ (Solvay Speciality Polymers), Flemion® (Asahi Glass Co.), or ionomers based on sulfonated hydrocarbons, such as those available as fumapem® P, E or K series products from FuMA-Tech GmbH, JSR Corporation, Toyobo Corporation, etc. Examples of suitable anion-conducting polymers include A901 from Tokuyama and Fumasep FAA from FuMA-Tech GmbH. The ion-conducting polymer of the third dispersion can be the same as the ion-conducting polymer of the first or second dispersion.

[0065] The third dispersion may include the ion-conducting polymer in an amount ranging from 5 to 80% by weight, preferably 10 to 50% by weight, preferably 15 to 30% by weight, and most preferably 15 to 20% by weight, based on the total weight of the second dispersion. The third dispersion may include the ion-conducting polymer in any combination of these range limits. For example, the third dispersion may include the ion-conducting polymer in an amount ranging from 10 to 20% by weight. The third dispersion may include substantially the same weight percent of the ion-conducting polymer as the first and / or second dispersion, based on the total weight of the respective dispersions.

[0066] Preferably, the third layer has substantially the same thickness (in the z-direction) as the first layer. The dried third layer can have the same thickness as the dried first layer. Thus, any reinforcing component can be reliably located in the center (z-direction) of the membrane between the first and third layers, reducing membrane curl. By providing the first and third layers on either side of the reinforcing component, ionic conductivity across the ion-conducting membrane can be improved.

[0067] Base material The method can further include removing the substrate after drying the first and second layers. If a third layer is deposited, the substrate can be removed after drying the third layer.

[0068] The substrate provides a surface onto which the first dispersion is deposited.

[0069] The substrate can be a backing layer. The backing layer provides support for the ion conductive membrane during manufacture and can provide support and strength during subsequent storage and / or transportation if not immediately removed. The material from which the backing layer is made should provide the necessary support, be preferably compatible with the first dispersion, be preferably impermeable to the first dispersion, be able to withstand the process conditions involved in the manufacture of the ion conductive membrane, and be easily removed without damaging the ion conductive membrane. Examples of materials suitable for use include fluoropolymers such as polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymers (PFA), fluorinated ethylene propylene (FEP - copolymer of hexafluoropropylene and tetrafluoroethylene), and polyolefins such as biaxially oriented polypropylene (BOPP). Other examples include laminates, multilayer extrudates, and coated films / foils that can retain their mechanical strength / integrity at high temperatures, e.g., temperatures up to 200°C. Examples include laminates of poly(ethylene-co-tetrafluoroethylene) and polyethylene naphthalate (PEN), laminates of polymethylpentene (PMP) and PEN, and laminates of polyperfluoroalkoxy (PFA), polyethylene terephthalate (PET), and polyimide (PI). Laminates can have two or more layers, such as ETFE-PEN-ETFE, PMP-PEN-PMP, PFA-PET-PFA, PEN-PFA, FEP-PI-FEP, PFA-PI-PFA, and PTFE-PI-PTFE. The layers can be bonded using adhesives such as acrylic or polyurethane.

[0070] The substrate can be a catalyst layer. The catalyst layer can be on a backing layer as defined above, and the first dispersion is deposited on the catalyst layer. The method can further comprise removing the backing layer from the catalyst layer after the step of drying the first and second layers (or after step (g) if present). When the substrate is a catalyst layer, the backing layer can be a gas diffusion layer. The gas diffusion layer can remain attached to the catalyst layer.

[0071] The catalyst layer comprises a catalyst. The catalyst layer may be for an electrode (e.g., anode or cathode) of a fuel cell or electrolyser. The catalyst is preferably an electrocatalyst. The catalyst may be a finely divided unsupported metal powder or may be a supported catalyst in which small metal nanoparticles are dispersed on a conductive particulate carbon support. The electrocatalyst metal is preferably (i) the platinum group metals (i.e., platinum, palladium, rhodium, ruthenium, iridium, and osmium); (ii) gold or silver; (iii) Base metals; or (iv) Alloys or mixtures containing one or more of these metals or their oxides. The preferred electrocatalyst metal is platinum, which may be alloyed with other precious or base metals. When the electrocatalyst is a supported catalyst, the loading of metal particles on the carbon support material is suitably in the range of 10-90 wt.%, preferably 15-75 wt.%, of the weight of the resulting electrocatalyst.

[0072] 1-3 illustrate an exemplary method of the present invention. The dimensions (e.g., thickness) of each layer are not drawn to scale for clarity. The same reference numbers are used throughout the drawings to refer to identical features and method steps.

[0073] Referring to FIG. 1, a first dispersion is deposited on a substrate 100 to form a first layer 110. The first dispersion includes an ion-conducting polymer. A second dispersion is deposited on the first dispersion while it is still wet to form a second layer 120 on the first layer 110. The second dispersion includes an ion-conducting polymer. The second dispersion typically has a lower density than the first dispersion such that the second dispersion floats on the first dispersion. The first and second layers 110, 120 form a layered structure. A porous reinforcing component, such as an ePTFE material or a network of PBI fibers, is placed on the second layer 120 while the second dispersion is still wet, providing a reinforced second layer 125. The second dispersion impregnates the pores of the reinforcing component. Preferably, the first dispersion exhibits a lower degree of wetting towards the reinforcing component compared to the second dispersion, so that the first dispersion does not impregnate the pores of the reinforcing component. The reinforcing component is present in the second layer. The reinforcing component is present on the first layer 110. The first and second layers are then dried to form a reinforced ion-conducting membrane 150 comprising an unreinforced first layer 110 and a reinforced second layer 125. The substrate 100 can then be removed, if desired.

[0074] FIG. 2 shows a further embodiment of the invention. The first dispersion, the second dispersion and the reinforcing component are deposited and dried in the same manner as described in connection with FIG. 1. The embodiment of FIG. 2 includes an additional subsequent step of depositing a third dispersion on the second layer 125 to form a third layer 130. The third dispersion includes an ion-conducting polymer. The third layer 130 is then dried. The resulting product is a reinforced ion-conducting membrane 250 including a reinforced second ion-conducting layer 125 centrally disposed between the unreinforced first and third ion-conducting layers 110, 130. The substrate 100 can then be removed, if desired. The reinforced ion-conducting membrane 250 can be used in a fuel cell or electrolyzer.

[0075] In either the method of FIG. 1 or FIG. 2, the first and second dispersions can be deposited simultaneously. That is, the second dispersion can be deposited on the first dispersion while the first dispersion is still being deposited. Preferably, the first and second dispersions contact or form an interface with each other before forming the first and second layers, respectively. FIG. 3 shows an exemplary method of depositing the first and second dispersions simultaneously. Although FIG. 3 shows a preferred dual head slot die coating process, alternative coating techniques can be used.

[0076] The substrate 300 is positioned under a slot die head 302. The slot die head 302 is a dual slot die head including a first outlet 304 and a second outlet 306. A first ionomer dispersion 310 is deposited onto the substrate 300 through the first outlet 304. The first ionomer dispersion 310 forms a first layer 312. By way of example, the first ionomer dispersion 310 can have a continuous phase including 40% by weight ethanol and 60% by weight water (based on the total weight of the continuous phase).

[0077] While the first ionomer dispersion 310 is still wet, a second ionomer dispersion 320 is deposited onto the first ionomer dispersion 310 to form a second layer 322. By way of example, the second ionomer dispersion 320 has a continuous phase that includes 80% by weight ethanol and 20% by weight water (based on the total weight of the continuous phase). The first ionomer dispersion 310 is denser than the second ionomer dispersion 320. There is minimal mixing between the first and second ionomer dispersions.

[0078] As the first and second ionomer dispersions are deposited, the slot die head 302 moves in the direction of the x-mark relative to the substrate 300. Typically, the slot die head 302 is moved at a substantially constant speed during the deposition process, which can help to provide a uniform coating thickness.

[0079] FIG. 3 shows a process of providing a porous reinforcing component 330 in the second layer 322. The porous reinforcing component 330 is placed on the second ionomer dispersion 320 while the first and second ionomer dispersions 310, 320 are still wet. The second ionomer dispersion 320 impregnates the pores of the reinforcing component 330. However, the first layer 312 does not impregnate the pores of the reinforcing component 330. Without wishing to be bound by any theory or speculation, it is believed that the lower wettability of the first layer 312 to the reinforcing component substantially prevents the reinforcing component from sinking into the first layer 312. The reinforcing component is present in the second layer 322. The reinforcing component 330 is present directly on the first wet layer 312. Thus, the reinforcing component 330 can be reliably positioned in the z-direction (the vertical direction shown in FIG. 3), which may help to avoid curling of the membrane.

[0080] Example 1 A first dispersion containing 10 wt. % ethanol and 90 wt. % water (based on the total weight of the continuous phase), 25 wt. % ionomer (based on the total weight of the first dispersion) was added to the sample vial. A dye was also added to the first dispersion for ease of identification. The dye did not otherwise substantially affect the properties of the dispersion.

[0081] A second dispersion containing 80 wt% ethanol and 20 wt% water (based on the total weight of the continuous phase) and about 17 wt% ionomer (based on the total weight of the second dispersion) was added dropwise such that the droplets flowed down the sidewall of the sample vial. The second dispersion was less dense than the first dispersion. As shown in FIG. 4, the second dispersion 420 formed a separate layer on top of the first dispersion 410.

[0082] The layered structure was metastable: it could be irreversibly destroyed by the application of shear (mixing) forces; however, the layers remained stable for up to 48 hours if left undisturbed.

[0083] Example 2 A first dispersion containing 10 wt. % ethanol and 90 wt. % water (based on the total weight of the continuous phase), 25 wt. % ionomer (based on the total weight of the first dispersion) was added to the sample vial. A dye was also added to the first dispersion for ease of identification. The dye did not otherwise substantially affect the properties of the dispersion.

[0084] A second dispersion containing 10 wt% ethanol and 90 wt% water (based on the total weight of the continuous phase) and 15 wt% ionomer (based on the total weight of the second dispersion) was added dropwise so that the droplets ran down the side wall of the sample vial. The second dispersion had a lower ionomer concentration than the first dispersion. As shown in FIG. 5, the second dispersion 520 formed a separate layer on top of the first dispersion 510.

[0085] The layered structure was metastable: it could be irreversibly destroyed by the application of shear (mixing) forces; however, the layers remained stable for up to 48 hours if left undisturbed.

[0086] Example 3 A first dispersion containing 25% by weight ethanol and 75% by weight water (based on the total weight of the continuous phase), 20% by weight ionomer (based on the total weight of the first dispersion) was added to a sample vial.

[0087] A second dispersion containing 30 wt% ethanol and 70 wt% water (based on the total weight of the continuous phase) and 20 wt% ionomer (based on the total weight of the second dispersion) was added dropwise such that the droplets flowed down the sidewall of the sample vial. The second dispersion was less dense than the first dispersion. As shown in FIG. 6, the second dispersion 620 formed a separate layer on top of the first dispersion 610.

[0088] The layered structure was metastable: it could be irreversibly destroyed by the application of shear (mixing) forces; however, the layers remained stable for up to 48 hours if left undisturbed.

[0089] Example 4 The first dispersion was coated onto a polyethylene terephthalate (PET) substrate using bar coating to form a first layer. The first dispersion included a continuous phase of 60 wt% water and 40 wt% ethanol based on the total weight of the continuous phase. The first dispersion further included an ionomer in an amount of about 17 wt% based on the total weight of the first dispersion. The wet layer thickness of the first layer was 30 μm.

[0090] The second dispersion was coated onto a separate PET substrate using bar coating to form a second layer. The second dispersion included a continuous phase of 20 wt% water and 80 wt% ethanol based on the total weight of the continuous phase. The second dispersion further included an ionomer in an amount of about 17 wt% based on the total weight of the second dispersion. The wet layer thickness of the second layer was 200 μm.

[0091] While the second layer was still wet, an expanded PTFE sheet (available from Ningbo Quantum Seal Co. Ltd.) was placed into the second layer until the pores of the expanded PTFE sheet were completely impregnated with the second dispersion. The expanded PTFE sheet was then placed on top of the first layer while the first and second dispersions were still wet. The expanded PTFE sheet was pulled down onto the first layer to ensure good contact between the expanded PTFE sheet and the first layer.

[0092] The first layer and the reinforced second layer were dried at 80° C. in a convection oven to form an ion-conducting membrane comprising a first non-reinforced layer and a second reinforced layer. FIG. 7 shows an SEM image of a cross section of the dried ion-conducting membrane on a backing film 700. The first layer 710 consists only of the ion-conducting polymer. The second layer 720 comprises the reinforcing component and the ion-conducting polymer. The first layer 710 is in direct contact with the reinforced second layer 720, but remains separate. In this example, the first dispersion has a lower wettability for the reinforcing component than the second dispersion. As a result, the first dispersion does not impregnate the pores of the reinforcing component, and the first layer remains as a separate layer of known thickness, even if the reinforcing component is added while the first layer is still wet. Thus, the through-plane positional placement of the reinforcing component can be reliably controlled while reducing the number of drying steps required to produce an ion-conducting membrane.

Claims

1. 1. A method for producing an ion-conducting membrane, the method comprising: (a) providing a substrate; (b) depositing a first dispersion onto the substrate to form a first layer, the first dispersion comprising an ion-conducting polymer; (c) depositing a second dispersion onto the first dispersion to form a second layer on the first layer, the second dispersion comprising an ion-conducting polymer; (d) providing a reinforcing component comprising pores such that the second dispersion impregnates at least a portion of the pores of the reinforcing component; (e) drying the first layer and the second layer; Including, Step (e) is carried out after steps (c) and (d). A method for producing an ion-conducting membrane.

2. The method of claim 1 , wherein the first dispersion has a density greater than the density of the second dispersion.

3. 3. The method of claim 1, wherein the second dispersion has a surface tension that is less than the surface tension of the first dispersion.

4. 3. The method of claim 1 or 2, wherein the second dispersion has a higher degree of wetting towards the reinforcing component than the first dispersion.

5. The method of claim 1 or 2, wherein the reinforcing component has a thickness substantially the same as a thickness of the second layer.

6. 3. The method of claim 1 or 2, wherein the first dispersion comprises a continuous phase comprising water, a polar solvent other than water, or a mixture thereof.

7. 7. The method of claim 6, wherein the continuous phase of the first dispersion comprises a polar solvent other than water in an amount less than 70 wt.%, preferably in the range of 10 to 50 wt.%, or more preferably 20 to 40 wt.%, based on the total weight of the continuous phase.

8. The method of claim 1 or 2, wherein the second dispersion comprises a continuous phase comprising water, a polar solvent other than water, or a mixture thereof.

9. 9. The method of claim 8, wherein the continuous phase of the second dispersion comprises the polar solvent other than water in an amount ranging from and including 50 to 100% by weight, preferably 60 to 90% by weight, or more preferably 70 to 80% by weight, based on the total weight of the continuous phase.

10. The method of claim 1 or 2, wherein the first dispersion and the second dispersion are deposited simultaneously.

11. 3. The method of claim 1 or 2, wherein the first dispersion and / or the second dispersion is deposited using a slot die coating method, a knife coating method, a bar coating method, an inkjet printing method, a gravure printing method, a curtain coating method, or a spray coating method.

12. 12. The method of claim 11, wherein the slot die coating method comprises providing a slot die head including a first outlet and a second outlet, wherein the first dispersion is deposited onto the substrate through the first outlet and the second dispersion is deposited onto the first dispersion through the second outlet.

13. (f) depositing a third dispersion onto the second layer to form a third layer, the third dispersion comprising an ion-conducting polymer; (g) drying the third layer; The method of claim 1 or 2, further comprising:

14. 14. The method of claim 13, wherein the step of depositing the third dispersion occurs after the steps of drying the first and second layers.

15. The method of claim 13 , wherein the third layer has a thickness substantially the same as a thickness of the first layer.

16. The method of claim 1 or 2, further comprising the step of removing the substrate after the step of drying the first and second layers.

17. The method of claim 1 or 2, wherein the substrate is a catalyst layer.

18. 1. A method for producing a catalyst-coated ion-conducting membrane, comprising: Providing an ion-conducting membrane produced using the method of claim 1 or 2; applying a catalyst layer to the ion-conducting membrane; 1. A method for producing a catalyst-coated ion-conducting membrane, comprising:

19. 1. A method of manufacturing a membrane seal assembly, comprising: Providing an ion-conducting membrane produced using the method of claim 1 or 2; applying a sealing component to the ion-conducting membrane; A method of manufacturing a membrane seal assembly, comprising:

20. A method for manufacturing a membrane-electrode assembly, comprising: Providing an ion-conducting membrane produced using the method of claim 1 or 2; applying a gas diffusion electrode to the ion-conducting membrane; A method for producing a membrane-electrode assembly, comprising:

21. A method for manufacturing a membrane-electrode assembly, comprising: providing a catalyst-coated ion-conducting membrane produced using the method of claim 18; applying a gas diffusion layer to the catalyst coated ion conductive membrane; A method for producing a membrane-electrode assembly, comprising:

22. A method for manufacturing a membrane-electrode assembly, comprising: Providing a membrane seal assembly manufactured using the method of claim 19; applying a gas diffusion electrode to the membrane seal assembly; A method for producing a membrane-electrode assembly, comprising:

23. An ion-conducting membrane for an electrochemical device obtainable using the method according to claim 1 or 2.

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