Electrode ink coating method

Abstract

To provide a method of coating an electrode ink that can form an electrode layer easily.SOLUTION: The method of coating an electrode ink for forming an electrode layer 2 on a porous gas diffusion layer 4 includes a heating step S1 of heating a lower surface of the gas diffusion layer 4 by heating means 5; a coating step S2 of coating an electrode ink 20 on the gas diffusion layer 4; a drying step S3 of drying the electrode ink 20 coated in the coating step S2; and a repeating step S4 of repeatedly performing the coating step S2 and the drying step S3. It is preferable that the repeating step S4 is performed until a surface of the gas diffusion layer 4 is covered with the electrode ink 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for coating an electrode ink.

Background Art

[0002] Conventionally, it has been known to use a catalyst-coated electrolyte membrane (CCM) in which an anode electrode layer and a cathode electrode layer are arranged and joined on both sides of a solid polymer electrolyte membrane for water electrolysis or the like. When manufacturing the catalyst-coated electrolyte membrane, a technique has been proposed in which an electrode ink constituting an electrode layer is applied to a base material constituting the solid polymer electrolyte membrane and dried (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When using a catalyst-coated electrolyte membrane in which an electrode layer is joined to a solid polymer electrolyte membrane for water electrolysis, the electrode layer may peel off during electrolysis. Therefore, it is conceivable to form an electrode layer on the diffusion layer of a gas diffusion electrode (GDE) arranged outside the solid polymer electrolyte membrane. However, when attempting to coat the electrode layer on the diffusion layer side, since the diffusion layer is composed of a porous body, there is a problem that the electrode ink deeply penetrates and it is difficult to form the electrode layer.

Means for Solving the Problems

[0005] (1) The present invention relates to a method for coating an electrode ink (e.g., electrode ink 20) ​​for forming an electrode layer (e.g., electrode layer 2) on a porous gas diffusion layer (e.g., gas diffusion layer 4), comprising: a heating step (e.g., heating step S1) of heating the lower surface of the gas diffusion layer with a heating means (e.g., heating means 5); a coating step (e.g., coating step S2) of coating the electrode ink onto the gas diffusion layer; a drying step (e.g., drying step S3) of drying the electrode ink coated in the coating step; and a repeating step (e.g., repeating step S4) of repeatedly performing the coating step and the drying step.

[0006] (2) The repeating process is preferably carried out until the surface of the gas diffusion layer is covered with the electrode ink.

[0007] (3) The heating step is preferably carried out by placing the gas diffusion layer on the heating means, which is a plate-shaped heating means that can be heated up.

[0008] (4) The present invention relates to an electrolyte membrane / electrode structure (e.g., electrolyte membrane / electrode structure 1) having an electrolyte membrane / electrode structure (e.g., electrolyte membrane / electrode structure 1) having an electrode layer (e.g., electrode layer 2) disposed on both sides of a solid polymer electrolyte membrane (e.g., solid polymer electrolyte membrane 3), and a gas diffusion layer (e.g., gas diffusion layer 4) formed on the outside of the electrode layer, wherein the gas diffusion layer is composed of a porous sheet-like member (e.g., sheet-like member 40), and the electrode layer has an inner electrode layer (e.g., inner electrode layer 2a) in which electrode ink (e.g., electrode ink 20) ​​is impregnated into the interior of the gas diffusion layer and dried, and an outer electrode layer (e.g., outer electrode layer 2b) in which the electrode ink is disposed on the surface of the gas diffusion layer. [Effects of the Invention]

[0009] According to (1) above, since the electrode ink is applied while the gas diffusion layer is heated from below, the electrode ink dries before it reaches the bottom surface of the gas diffusion layer and remains inside the gas diffusion layer. Then, by repeatedly applying and drying the ink from this state, it becomes possible to quickly apply the electrode ink to the surface of the gas diffusion layer. In addition, since a part of the electrode layer is bonded together with the gas diffusion layer inside the gas diffusion layer, when water electrolysis is performed, the part of the electrode layer that is bonded together with the gas diffusion layer in the aqueous solution acts as an anchor, suppressing the peeling of electrode layer 2.

[0010] According to (2) above, by repeating the coating process and drying process until the surface of the gas diffusion layer is covered with electrode ink, the electrode layer can be securely bonded to the gas diffusion layer in a way that makes it difficult for the electrode layer to peel off, and the electrode layer can be coated onto the gas diffusion layer.

[0011] According to (3) above, by placing the gas diffusion layer on a plate-shaped heating means that can be heated, it becomes possible to dry the gas diffusion layer while coating it, thereby improving the efficiency of the manufacturing process.

[0012] According to (4) above, since the inner electrode layer is integrally bonded with the gas diffusion layer inside the gas diffusion layer, when water electrolysis is performed, a part of the electrode layer integrated with the gas diffusion layer in the aqueous solution acts as an anchor, suppressing the peeling of the electrode layer. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram illustrates the structure of the electrolyte membrane and electrode structure in this embodiment. [Figure 2A] This diagram illustrates the initial stages of the coating and heating processes in this embodiment. [Figure 2B] This diagram illustrates the intermediate state of the repeating process in this embodiment. [Figure 2C] This diagram illustrates the intermediate state of the repeating process in this embodiment. [Figure 2D] This diagram illustrates the state after the coating process of this embodiment has been completed. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. As shown in Figure 1, the electrode ink coating method of this embodiment is used in the manufacture of an electrolyte membrane / electrode structure (MEA) 1 having a gas diffusion electrode (GDE) 10. In the electrolyte membrane / electrode structure 1 of this embodiment, electrode layers 2 are arranged on both sides of a solid polymer electrolyte membrane 3, a gas diffusion layer 4 is arranged on the outside of the electrode layer 2, and the gas diffusion electrode 10 is constructed by forming the electrode layer 2 on the gas diffusion layer (GDL) 4.

[0015] The gas diffusion layer 4 is composed of a porous sheet-like member 40. The sheet-like member 40 may be, for example, nickel foam or carbon cloth.

[0016] The electrode layer 2 is a catalyst layer having an anode electrode layer 21 and a cathode electrode layer 22. The electrode layer 2 is formed by coating the gas diffusion layer 4 with electrode ink 20. The electrode ink 20 is a liquid containing a composition for forming electrodes, and may be, for example, a liquid containing a catalyst support bearing a catalyst, a proton-conducting ionomer (electrolytic polymer, electrolyte solution), and a dispersion solvent for dispersing the catalyst support and the ionomer. The dispersion solvent may be water. The viscosity of the electrode ink 20 may be, for example, about 1 to 10 mPas.

[0017] The solid polymer electrolyte membrane 3 is a proton-conducting membrane formed in film form from a polymer that belongs to the category of cation exchange resins and possesses proton conductivity. Examples of cation exchange resins include sulfonates of vinyl polymers such as polystyrene sulfonic acid, polymers in which sulfonic acid groups or phosphate groups are introduced into heat-resistant polymers such as perfluoroalkyl sulfonic acid polymers, perfluoroalkyl carboxylic acid polymers, polybenzimidazole, and polyether ether ketones, and polymers in which a rigid polyphenylene obtained by polymerizing aromatic compounds consisting of phenylene chains is the main component and a sulfonic acid group is introduced thereto.

[0018] In the method of applying the electrode ink of this embodiment, a coating device (not shown) and a plate-shaped heating means 5 called a surface plate are used. The coating device to be used is not particularly limited, but it is one that applies the electrode ink 20 while moving a blade, a bar coater, or other known applicator in a certain direction. For example, it may be performed using a blade coater.

[0019] The heating means 5 has a thin substantially rectangular parallelepiped plate-shaped member having a flat surface, and is configured with a heater (not shown) provided on the plate-shaped member. The surface of the heating means 5 is heated by the heater and the temperature rises. As a result, the temperature of the sheet-shaped member 40 placed on the heating means 5 rises. The heating means 5 may be one in which a thermoelectric heating device is arranged on a plate-shaped member made of metal. The heater may be arranged inside the plate-shaped member or attached to the outside.

[0020] As shown in FIG. 2A, the sheet-shaped member 40 is placed on the heating means 5, and the lower surface of the sheet-shaped member 40 is heated with a heater (heating step S1). Considering the temperature at which the applied electrode ink 20 can be dried and the temperature at which the solvent contained in the electrode ink 20 volatilizes, the heating temperature is preferably in the range of 80 degrees to 100 degrees.

[0021] While heating is performed in the heating step S1, the electrode ink 20 is applied onto the sheet-shaped member 40 in parallel using a blade coater (coating step S2). In the state shown in FIG. 2A, the electrode ink 20 has penetrated into the sheet-shaped member 40. However, since the sheet-shaped member 40 is heated, the electrode ink 20 does not reach the lower surface of the sheet-shaped member 40 and remains slightly above the lower surface of the sheet-shaped member 40 in the thickness direction while being partially dried.

[0022] In the state of FIG. 2A, the electrode ink 20 applied in the coating step S2 is dried (drying step S3). In the drying step S3, after the electrode ink 20 is applied to the sheet-shaped member 40 with a blade coater, the coated sheet-shaped member is placed on the heating means 5 for a predetermined time, for example, about 50 seconds to 70 seconds. During that time, the applied electrode ink 20 is dried by the heat of the heating means 5.

[0023] As shown in Figure 2A, after only one coating, the electrode ink 20 soaks into the sheet-like member 40. However, because the sheet-like member 40 is heated to 80 degrees or higher by the heating means 5, the electrode ink 20 does not reach the bottom surface of the sheet-like member 40 and remains inside the sheet-like member 40.

[0024] As shown in Figures 2B to 2D, the coating process S2 and drying process S3 are repeated (repeated process S4). The number of repetitions of the repeating process S4 is not particularly limited, as long as it can be performed until the surface of the sheet-like member 40 is covered with electrode ink 20. For example, it is preferable to repeat the coating process S2 and drying process S3 about 8 times. As shown in Figures 2B and 2C, as the coating process S2 and drying process S3 are repeated, the electrode ink 20 builds up thicker with each coating, and as shown in Figure 2D, it is eventually arranged to cover the surface of the sheet-like member 40. By repeating the coating process S2 and drying process S3, the electrode ink 20 is coated onto the sheet-like member 40 to form the electrode layer 2. The thickness of the electrode layer 2 may be, for example, several tens of microns.

[0025] In Figures 2B to 2D, of the electrode layers 2 formed by coating with electrode ink 20, the layer in which the electrode ink 20 has soaked into the interior of the sheet-like member 40 and remains in a dried state is the inner electrode layer 2a, and the layer in which the electrode ink 20 is exposed and placed on the surface of the sheet-like member 40 is the outer electrode layer 2b. Furthermore, because the heating means 5 prevents the lowest part of the electrode layer 2 from reaching the sheet-like member 40, a void layer 4a is also formed between the lower surface of the inner electrode layer 2a and the lower surface of the sheet-like member 40, where only the porous layer of the sheet-like member 40 is located.

[0026] The coating method comprising the heating step S1, drying step S3, and repeating step S4 described above is used to form the anode electrode layer 21 and the cathode electrode layer 22, respectively. In Figure 1, for illustrative purposes, a gap is shown between the anode electrode layer 21 and the cathode electrode layer 22 and the solid polymer electrolyte membrane 3. In reality, the anode electrode layer 21 and the cathode electrode layer 22 formed in the above steps are in contact with one side of the solid polymer electrolyte membrane 3, but are not bonded to it.

[0027] This embodiment provides the following effects. (1) A method for coating an electrode ink to form an electrode layer 2 on a porous gas diffusion layer 4 comprises a heating step S1 of heating the lower surface of the gas diffusion layer 4 with a heating means 5, a coating step S2 of coating electrode ink 20 onto the gas diffusion layer 4, a drying step S3 of drying the electrode ink 20 coated in the coating step S2, and a repeating step S4 of repeating the coating step S2 and the drying step S3. Since the electrode ink 20 is applied while the gas diffusion layer 4 is heated from below, the electrode ink 20 dries before reaching the bottom surface of the gas diffusion layer 4 and remains inside the gas diffusion layer 4. By repeatedly applying and drying the ink in this state, it becomes possible to quickly coat the surface of the gas diffusion layer 4 with the electrode ink 20. In addition, because a portion of the electrode layer 2 is integrally bonded with the gas diffusion layer 4 inside the gas diffusion layer 4, when water electrolysis is performed, the portion of the electrode layer 2 that is integrated with the gas diffusion layer 4 in the aqueous solution acts as an anchor, suppressing the peeling of the electrode layer 2.

[0028] (2) According to this embodiment, the repeated process S4 is carried out until the surface of the gas diffusion layer 4 is covered with the electrode ink 20. By repeating the coating process S2 and the drying process S3 until the surface of the gas diffusion layer 4 is covered with the electrode ink 20, the electrode layer 2 is securely bonded to the gas diffusion layer 4 in a way that makes it difficult for the electrode layer 2 to peel off, and the electrode layer 2 can be coated onto the gas diffusion layer 4.

[0029] (3) According to this embodiment, the heating step S1 is performed by placing the gas diffusion layer 4 on a plate-shaped heating means 5 that can be heated up. By placing the gas diffusion layer 4 on a plate-shaped heating means 5 that can be heated, and heating it, it becomes possible to dry the gas diffusion layer 4 while coating it, thereby improving the efficiency of the manufacturing process.

[0030] (4) According to this embodiment, the electrolyte membrane / electrode structure 1 has an electrolyte membrane / electrode structure 1 having an electrode layer 2 arranged on both sides of a solid polymer electrolyte membrane 3 and a gas diffusion layer 4 formed on the outside of the electrode layer 2, wherein the gas diffusion layer 4 is composed of a porous sheet-like member 40, and the electrode layer 2 is composed of an inner electrode layer 2a in which electrode ink 20 has permeated into the inside of the gas diffusion layer 4 and dried, and an outer electrode layer 2b in which electrode ink 20 is arranged on the surface of the gas diffusion layer 4. Because the inner electrode layer 2a is integrally bonded with the gas diffusion layer 4 inside the gas diffusion layer 4, when water electrolysis is performed, a portion of the electrode layer 2 that is integrated with the gas diffusion layer 4 in the aqueous solution acts as an anchor, suppressing the peeling of the electrode layer 2.

[0031] It should be noted that the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. The number of coatings, drying temperature, viscosity of the electrode ink 20, etc., are correlated with each other and may be changed as appropriate. [Explanation of Symbols]

[0032] 1 Electrolyte membrane / electrode structure 2 electrode layer 3 Solid polymer electrolyte membrane 4. Gas diffusion layer 4a Electrode inner layer 4b Electrode outer layer 5 Heating means 10 Gas diffusion electrode 20 Electrode Ink 40 Sheet-like member

Claims

1. A method for coating an electrode ink to form an electrode layer on a porous gas diffusion layer, A heating step of heating the lower surface of the gas diffusion layer with a heating means, A coating step in which the electrode ink is applied to the gas diffusion layer while being heated by the heating means, thereby partially drying the electrode ink before it reaches the lower surface of the gas diffusion layer, A drying step for drying the electrode ink coated in the coating step, The process comprises a repeating step which involves repeatedly performing the coating step and the drying step. A method for coating electrode ink, wherein the heating step is performed by placing the gas diffusion layer on a plate-shaped heating means that can be heated up.

2. The method for coating an electrode ink according to claim 1, wherein the repeated step is performed until the surface of the gas diffusion layer is covered with the electrode ink.

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