Method of coating electrode ink

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 applying electrode ink.

Background Art

[0002] Conventionally, it has been known to use a catalyst layer-attached 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 layer-attached electrolyte membrane, a technique has been proposed in which 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 a catalyst layer-attached electrolyte membrane in which an electrode layer is joined to a solid polymer electrolyte membrane is used 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) disposed outside the solid polymer electrolyte membrane. However, when attempting to apply an electrode layer to the diffusion layer side, since the diffusion layer is composed of a porous body, there has been a problem that the electrode ink deeply penetrates and it is difficult to form an electrode layer.

Means for Solving the Problems

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

[0006] (2) It is preferable that the repeating step is performed until the surface of the gas diffusion layer is covered with the electrode ink.

[0007] (3) It is preferable that the heating step is performed by placing the gas diffusion layer on the plate-shaped heating means capable of raising the temperature.

[0008] (4) The present invention relates to an electrolyte membrane - electrode structure (for example, electrolyte membrane - electrode structure 1) having a gas diffusion electrode (for example, gas diffusion electrode 10) in which electrode layers (for example, electrode layer 2) are disposed on both surfaces of a solid polymer electrolyte membrane (for example, solid polymer electrolyte membrane 3), and a gas diffusion layer (for example, gas diffusion layer 4) is formed outside the electrode layer. The gas diffusion layer is composed of a porous sheet-like member (for example, sheet-like member 40), and the electrode layer includes an inner electrode layer (for example, inner electrode layer 2a) in which the electrode ink (for example, electrode ink 20) has penetrated and dried inside the gas diffusion layer, and an outer electrode layer (for example, outer electrode layer 2b) in which the electrode ink is disposed on the surface of the gas diffusion layer.

Advantages of the Invention

[0009] According to (1) above, since the electrode ink is applied with the gas diffusion layer heated from the lower surface, the electrode ink dries before reaching the lower surface of the gas diffusion layer and stays inside the gas diffusion layer. Then, by repeating the application and drying from that state, it becomes possible to quickly apply the electrode ink to the surface of the gas diffusion layer. Further, since a part of the electrode layer is integrally bonded with the gas diffusion layer inside the gas diffusion layer, when performing water electrolysis, a part of the electrode layer integrated with the gas diffusion layer in the aqueous solution exhibits an anchor effect, suppressing the peeling of the electrode layer 2.

[0010] According to (2) above, by repeating the application process and the drying process until the surface of the gas diffusion layer is covered with the electrode ink, the electrode layer is surely bonded so as to be difficult to peel from the gas diffusion layer, and the electrode layer can be applied to the gas diffusion layer.

[0011] According to (3) above, by placing the gas diffusion layer on the plate-shaped heating means capable of raising the temperature and heating it, it becomes possible to dry the gas diffusion layer while applying, 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 performing water electrolysis, a part of the electrode layer integrated with the gas diffusion layer in the aqueous solution exhibits an anchor effect, suppressing the peeling of the electrode layer.

Brief Description of Drawings

[0013]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Mode 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 FIG. 1, the method for coating the electrode ink of the present embodiment is used for manufacturing an electrolyte membrane-electrode assembly (MEA) 1 having a gas diffusion electrode (GDE) 10. In the electrolyte membrane-electrode assembly 1 of the present embodiment, electrode layers 2 are disposed on both sides of a solid polymer electrolyte membrane 3, a gas diffusion layer 4 is disposed outside the electrode layers 2, and the gas diffusion electrode 10 is configured 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, a nickel foam, a carbon cloth, or the like.

[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 the electrode ink 20. The electrode ink 20 is a liquid containing a composition for forming an electrode, and may be, for example, a liquid containing a catalyst carrier carrying a catalyst, an ionomer (electrolytic polymer, electrolyte solution) having proton conductivity, and a dispersion solvent for dispersing the catalyst carrier 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, for example, a proton conduction membrane formed by forming a polymer belonging to a cation exchange resin and having proton conductivity into a film shape. Examples of the cation exchange resin include sulfonated vinyl-based polymers such as polystyrene sulfonic acid, perfluoroalkyl sulfonic acid polymers, perfluoroalkyl carboxylic acid polymers, polymers obtained by introducing a sulfonic acid group or a phosphoric acid group into heat-resistant polymers such as polybenzimidazole and polyether ether ketone, and polymers having a rigid polyphenylene obtained by polymerizing an aromatic compound composed of a phenylene chain as a main component and introducing a sulfonic acid group thereto.

[0018] In the method of applying the electrode ink of this embodiment, a coating device (not shown) and a plate-like heating means 5 called a surface plate are used. The coating device to be used is not particularly limited, but it is a device 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-like member having a flat surface, and is configured by providing a heater (not shown) on the plate-like 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-like member 40 placed on the heating means 5 rises. The heating means 5 may be a metal plate-like member with a thermoelectric heating device arranged thereon. The heater may be arranged inside the plate-like member or attached to the outside.

[0020] As shown in FIG. 2A, the sheet-like member 40 is placed on the heating means 5, and the lower surface of the sheet-like member 40 is heated by the 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 performing heating in the heating step S1, the electrode ink ۲۰ is applied onto the sheet-like member ۴۰ 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-like member 40. However, since the sheet-like member 40 is heated, the electrode ink 20 does not reach the lower surface of the sheet-like member 40, but remains slightly above the lower surface 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 applying the electrode ink 20 to the sheet-like member 40 with a blade coater, the coated sheet-like 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 FIG. 2A, when only coated once, the electrode ink 20 has penetrated into the sheet-like member 40. However, since the sheet-like member 40 is heated to 80 degrees or more by the heating means 5, the electrode ink 20 stays inside the sheet-like member 40 without reaching the lower surface of the sheet-like member 40.

[0024] As shown in FIGS. 2B to 2D, the above coating step S2 and drying step S3 are repeated (repeating step S4). The repeating step S4 is not particularly limited in the number of repetitions as long as it can be performed until the surface of the sheet-like member 40 is covered with the electrode ink 20. For example, it is preferable to repeat the coating step S2 and the drying step S3 about 8 times. As shown in FIGS. 2B and 2C, when the coating step S2 and the drying step S3 are repeated, the electrode ink 20 overlaps and thickens each time it is coated, and finally, as shown in FIG. 2D, it is arranged to cover the surface of the sheet-like member 40. By repeating the coating step S2 and the drying step S3, the electrode ink 20 is coated on 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 FIGS. 2B to 2D, among the electrode layers 2 formed by coating the electrode ink 20, the layer in which the electrode ink 20 has penetrated into 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 arranged on the surface of the sheet-like member 40 is the outer electrode layer 2b. Further, since the lowermost side of the electrode layer 2 does not reach the sheet-like member 40 by the heating means 5, a void layer 4a in which only the porous layer of the sheet-like member 40 is arranged is also formed between the lower surface of the inner electrode layer 2a and the lower surface of the sheet-like member 40.

[0026] The coating method having the above heating step S1, drying step S3, and repeating step S4 is used when forming each of the anode electrode layer 21 and the cathode electrode layer 22. In FIG. 1, for the sake of explanation, the anode electrode layer 21, the cathode electrode layer 22, and the solid polymer electrolyte membrane 3 are shown with a space therebetween for convenience. Actually, the anode electrode layer 21 and the cathode electrode layer 22 formed in the above steps are in contact with one side and the other side of the solid polymer electrolyte membrane 3, but are arranged in a non-bonded state.

[0027] According to the present embodiment, the following effects are obtained. (1) The coating method of the electrode ink for forming the electrode layer 2 on the porous gas diffusion layer 4 includes a heating step S1 of heating the lower surface of the gas diffusion layer 4 by a heating means 5, a coating step S2 of coating the 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 repeating the coating step S2 and the drying step S3. Since the electrode ink 20 is coated while the gas diffusion layer 4 is heated from the lower surface, the electrode ink 20 dries before reaching the lower surface of the gas diffusion layer 4 and remains inside the gas diffusion layer 4. Then, by repeating the coating and drying from that state, it becomes possible to quickly coat the electrode ink 20 on the surface of the gas diffusion layer 4. Further, since a part of the electrode layer 2 is integrally bonded with the gas diffusion layer 4 inside the gas diffusion layer 4, when performing water electrolysis, a part of the electrode layer 2 integrated with the gas diffusion layer 4 in the aqueous solution exhibits an anchor effect, and peeling of the electrode layer 2 is suppressed.

[0028] (2) According to the present embodiment, the repeating step S4 is performed until the surface of the gas diffusion layer 4 is covered with the electrode ink 20. By repeating the coating step S2 and the drying step S3 until the surface of the gas diffusion layer 4 is covered with the electrode ink 20, the electrode layer 2 is surely bonded so as to be difficult to peel from the gas diffusion layer 4, and the electrode layer 2 can be coated on 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 the plate-shaped heating means 5 capable of raising the temperature. By placing the gas diffusion layer 4 on the plate-shaped heating means 5 capable of raising the temperature and heating it, it becomes possible to dry the gas diffusion layer 4 while coating, and the efficiency of the manufacturing process is improved.

[0030] (4) According to this embodiment, the electrolyte membrane-electrode structure 1 having the gas diffusion electrode 10 in which the electrode layers 2 are arranged on both sides of the solid polymer electrolyte membrane 3 and the gas diffusion layer 4 is formed outside the electrode layers 2 is composed of the gas diffusion layer 4 and the porous sheet-like member 40, and the electrode layer 2 includes an inner electrode layer 2a in which the electrode ink 20 penetrates and dries inside the gas diffusion layer 4 and an outer electrode layer 2b in which the electrode ink 20 is arranged on the surface of the gas diffusion layer 4. Since the inner electrode layer 2a is integrally bonded to the gas diffusion layer 4 inside the gas diffusion layer 4, when performing water electrolysis, a part of the electrode layer 2 in which the inside of the aqueous solution is integrated with the gas diffusion layer 4 exhibits an anchor effect, and the peeling of the electrode layer 2 is suppressed.

[0031] Note that the present invention is not limited to the above embodiment, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention. The number of coating times, the drying temperature, the viscosity of the electrode ink 20, etc. are correlated with each other and may be appropriately changed as necessary.

Explanation of Reference Numerals

[0032] 1 Electrolyte membrane-electrode structure 2 Electrode layer 3 Solid polymer electrolyte membrane 4 Gas diffusion layer 4a Inner electrode layer 4b Outer electrode layer 5 Heating means 10 Gas diffusion electrode 20 Electrode ink 40 Sheet-like member

Claims

1. A method for coating an electrode ink for forming an electrode layer on a porous gas diffusion layer, comprising: a heating step of heating the lower surface of the gas diffusion layer by heating means; a coating step of coating the electrode ink on the gas diffusion layer; a drying step of drying the electrode ink coated in the coating step; and a repeating step of repeatedly performing the coating step and the drying step.

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

3. The method for coating an electrode ink according to claim 1 or 2, wherein the heating step is performed by placing the gas diffusion layer on the plate-shaped heating means capable of raising the temperature.

4. An electrolyte membrane / electrode structure having a gas diffusion electrode in which electrode layers are disposed on both sides of a solid polymer electrolyte membrane and a gas diffusion layer is formed outside the electrode layers, wherein the gas diffusion layer is composed of a porous sheet-like member, and the electrode layer has an inner electrode layer in which the electrode ink has penetrated and dried inside the gas diffusion layer and an outer electrode layer in which the electrode ink is disposed on the surface of the gas diffusion layer.

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