Manufacturing method for electrode catalyst layer of fuel cell and ball mill device

Abstract

This reduces the intrusion of foreign matter into the electrode catalyst layer of a fuel cell. [Solution] A manufacturing method for an electrode catalyst layer of a fuel cell to be provided in a fuel cell, in which catalyst particles are prepared, and the catalyst particles, ionomer, and solvent are mixed to prepare a catalyst ink, uses a ball mill device in which at least the surfaces of the grinding balls and the inner surface of the container are made primarily of cerium oxide.

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode catalyst layer of a fuel cell and a ball mill device. [Background technology]

[0002] A fuel cell is a power generation device that generates electricity by electrochemically reacting hydrogen and oxygen. A fuel cell is constructed using a membrane electrode assembly (MEA) as its basic unit, in which electrode catalyst layers are arranged on both sides of an electrolyte membrane. For example, a gas diffusion layer is arranged on the outside of each electrode catalyst layer of the MEA, and a separator is further arranged on the outside of the gas diffusion layer to form a fuel cell unit. Fuel cells are used as a set of multiple fuel cell units (hereinafter also referred to as a "fuel cell stack") required depending on the desired power.

[0003] In a fuel cell, a fuel gas containing hydrogen is supplied to an electrode catalyst layer on the anode electrode (fuel electrode) side, and an oxidizing gas containing oxygen is supplied to an electrode catalyst layer on the cathode electrode (air electrode) side, and electrical energy is obtained through electrochemical oxidation and reduction reactions that occur at each electrode. The electrode catalyst layers on the anode electrode side and the cathode electrode side each contain catalyst particles in which a catalytically active catalytic metal, such as platinum or a platinum alloy, is supported on a conductive support, such as a carbon support.

[0004] The electrode catalyst layer is formed, for example, by preparing a conductive support for supporting a catalytic metal, then preparing catalyst particles in which the catalytic metal is supported on the conductive support, mixing the catalyst particles, an ionomer, a solvent, etc. to prepare a catalyst ink, and processing the catalyst ink into a sheet. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-115810 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, when preparing the catalyst ink used to form the electrode catalyst layer, a ball mill is sometimes used to mix and disperse catalyst particles in the catalyst ink. A ball mill is a device that grinds materials by rotating a container containing the material to be ground and grinding balls. The balls of conventional ball mills are made of a high-strength material such as zirconia, and the container used is a stainless steel or steel container whose inner surface is lined with a layer of a high-strength material such as zirconia.

[0007] Generally, to minimize wear on the balls and the container, the inner surfaces of the balls and the container are made of the same material, but wear caused by contact between the container and the balls, or between the balls themselves, inevitably leads to contamination.When a conventional ball mill is used to prepare catalyst ink, for example, zirconia powder becomes contaminant and gets mixed into the catalyst ink, resulting in the introduction of foreign matter into the electrode catalyst layer.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and an object of the present disclosure is to provide a method for manufacturing an electrode catalyst layer of a fuel cell, and a ball mill device, which are capable of suppressing the intrusion of foreign matter into the electrode catalyst layer of the fuel cell. [Means for solving the problem]

[0009] In order to solve the above problems, according to an aspect of the present disclosure, there is provided a method for manufacturing an electrode catalyst layer of a fuel cell to be provided in a fuel cell, the method comprising: a catalyst particle preparation step of preparing catalyst particles; and a catalyst ink preparation step of preparing a catalyst ink by stirring a mixed dispersion liquid containing the catalyst particles, an ionomer, and a solvent, wherein the catalyst ink preparation step uses a ball mill apparatus in which at least the surfaces of the milling balls and the inner surface of a container are each composed mainly of cerium oxide.

[0010] In order to solve the above problems, according to an aspect of the present disclosure, there is provided a method for manufacturing an electrode catalyst layer to be provided in a fuel cell, the method comprising: a catalyst particle preparation step of preparing catalyst particles; an ionomer coating step of coating the catalyst particles with an ionomer; and a catalyst ink preparation step of preparing a catalyst ink by stirring a mixed dispersion containing the ionomer-coated catalyst particles and a solvent, wherein a ball mill apparatus is used in at least one of the ionomer coating step and the catalyst ink preparation step, in which at least the surfaces of the milling balls and the inner surface of a container are each composed mainly of cerium oxide.

[0011] In order to solve the above-mentioned problems, according to another aspect of the present disclosure, there is provided a ball mill apparatus including a container having at least the inner surface of the container mainly composed of cerium oxide, and milling balls having at least the surfaces mainly composed of cerium oxide. [Effects of the Invention]

[0012] As described above, according to the present disclosure, it is possible to reduce the intrusion of foreign matter into the electrode catalyst layer of a fuel cell. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is an explanatory diagram showing an example of the configuration of a fuel cell; [Figure 2] 1 is a schematic diagram showing an example of the overall configuration of a ball mill apparatus. FIG. [Figure 3] FIG. 2 is a cross-sectional view showing an example of the configuration of a grinding ball in a ball mill device according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a cross-sectional view showing an example of the configuration of a container of the ball mill apparatus according to the embodiment. [Figure 5] FIG. 4 is a cross-sectional view showing another example of the configuration of the container of the ball mill apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0015] 1. Overview of this Disclosure Before describing a method for manufacturing an electrode catalyst layer of a fuel cell and a ball mill device according to an embodiment of the present disclosure, an overview of the present disclosure will be described.

[0016] As described above, when a conventional ball mill is used to prepare a catalyst ink for forming an electrode catalyst layer of a fuel cell, wear debris such as zirconia powder generated by wear of the milling balls and container can become foreign matter in the electrode catalyst layer. In the present disclosure, by improving the ball mill used to mix and disperse catalyst particles in the catalyst ink, it is possible to produce an electrode catalyst layer without causing wear debris to become foreign matter in the catalyst ink.

[0017] The method for manufacturing an electrode catalyst layer for a fuel cell according to the present disclosure is characterized in that the ball mill used to grind catalyst particles is a ball mill in which at least the surfaces of the grinding balls and the inner surface of the container are each made primarily of cerium oxide. In the present disclosure, the ball mill is a device that places grinding balls and materials in a container and rotates them, and the concept of the ball mill includes a bead mill.

[0018] Below, the basic configuration of a fuel cell stack will be described, followed by a description of a ball mill device used in the method for manufacturing an electrode catalyst layer of a fuel cell according to the present disclosure, and then a description of the method for manufacturing an electrode catalyst layer of a fuel cell.

[0019] In this specification, the term "catalyst particles" includes a catalyst support in which a catalytic metal is supported on a conductive support such as a carbon support, or a nitrogen-doped carbon catalyst prepared by heat-treating a precursor containing carbon, nitrogen, a transition metal, etc. Furthermore, the term "catalyst ink" refers to a paste-like material used to form an electrode catalyst layer that constitutes the anode or cathode of a fuel cell.

[0020] 2. Fuel Cell Stack First, an example of a fuel cell stack will be described. A fuel cell stack is composed of several tens to several hundreds of fuel cell units, each of which serves as a structural unit, stacked in the stacking direction. Each fuel cell unit has the function of generating electricity by reacting a fuel gas (hydrogen gas) with an oxidizing gas (oxygen in the air).

[0021] 1 is an explanatory diagram showing an example of the configuration of a fuel cell 10, showing a cross-sectional view of the fuel cell 10. The fuel cell 10 is configured as a membrane electrode assembly (MEA) having an anode electrode (hydrogen electrode) 13 and a cathode electrode (oxygen electrode) 15 on either side of an electrolyte membrane 11, which may be, for example, an ion exchange membrane. The fuel cell 10 also has a first separator 17 and a second separator 19 arranged to sandwich the anode electrode 13, the electrolyte membrane 11, and the cathode electrode 15. The anode electrode 13 has an anode catalyst layer (electrode catalyst layer) 13a and an anode diffusion layer 13b, and the cathode electrode 15 has a cathode catalyst layer (electrode catalyst layer) 15a and a cathode diffusion layer 15b.

[0022] It is known that during power generation in a fuel cell, hydrogen peroxide is generated in the anode catalyst layer 13a and the cathode catalyst layer 15a as a result of an electrochemical reaction, and hydroxyl radicals are generated from the hydrogen peroxide. Hydroxyl radicals may deteriorate the electrolyte membrane 11, and deterioration of the electrolyte membrane 11 may result in a decrease in the voltage of the fuel cell and a decrease in power generation performance. For this reason, for example, cerium oxide (cerium-containing oxide: CeO2) is mixed into the anode electrode 13, the cathode electrode 15, and the electrolyte membrane 11 as a radical quencher to suppress hydroxyl radicals. Cerium oxide dissolves cerium (IV) ions Ce4+, which decompose the hydroxyl radicals radicalized by hydrogen peroxide generated in the anode catalyst layer 13a and the cathode catalyst layer 15a, thereby suppressing deterioration of the electrolyte membrane 11.

[0023] In the above example, cerium oxide is mixed into the anode electrode 13, the cathode electrode 15, and the electrolyte membrane 11, but cerium oxide may be mixed into at least one of the anode electrode 13, the cathode electrode 15, and the electrolyte membrane 11.

[0024] <3. Ball mill equipment> Next, an example of the configuration of the ball mill device will be described.

[0025] Figures 2 to 4 are explanatory diagrams showing examples of the configuration of a ball mill apparatus. Figure 2 is a schematic diagram showing an example of the overall configuration of a ball mill apparatus. Figure 3 is a cross-sectional view showing an example of the configuration of milling balls, and Figure 4 is a cross-sectional view showing an example of the configuration of a container.

[0026] The ball mill apparatus 20 shown in Fig. 2 includes a container 21, a lid 23, grinding balls 25, and a rotating device 27. Workpiece 29 containing the material to be ground is placed into the container 21 together with the grinding balls 25, the lid 23 is attached to the container 21 to seal the interior of the container 21, and the rotating device 27 connected to the lid 23 is rotated to rotate the container 21. The rotation axis of the container 21 extends in a direction inclined with respect to the vertical direction, and the workpiece 29 and grinding balls 25 are agitated inside the container 21 as the container 21 rotates, and the material to be ground contained in the workpiece is ground by the grinding balls 25.

[0027] The ball mill apparatus to which the present disclosure is applied is not limited to the type shown in Fig. 2, and may be any of various types of conventionally known apparatuses. For example, the ball mill apparatus may be a uniaxial rotation type ball mill apparatus or a planetary type ball mill apparatus having multiple rotation axes.

[0028] The ball mill apparatus 20 according to this embodiment includes a container 21, at least the surface of which is primarily composed of cerium oxide, and milling balls 25, at least the surfaces of which are primarily composed of cerium oxide. As a result, even if the inner surface of the container 21 and the surfaces of the milling balls 25 are worn when mixing and dispersing catalyst particles in a catalyst ink for forming an electrode catalyst layer of a fuel cell, the resulting wear debris is the same as the cerium oxide that is mixed into the electrode catalyst layer as a radical quencher. This prevents wear debris from the ball mill apparatus 20 from becoming foreign matter for the electrode catalyst layer.

[0029] Furthermore, cerium oxide is a material that is less hard than zirconia, alumina, etc. Therefore, even if the inner surface of container 21 or the surface of grinding ball 25 were to crack and fragments were to get mixed into the catalyst ink, the risk of damaging the catalyst particles can be reduced.

[0030] "Containing cerium oxide as a main component" means that the cerium oxide content exceeds 50%. The cerium oxide content of at least the inner surface of the container 21 and at least the surfaces of the grinding balls 25 may be 80% or more, or even 95% or more. Materials that can be mixed with cerium oxide may be, for example, one or more of an electrode catalyst component, zirconia, and alumina. Examples of electrode catalyst components include platinum, cobalt, and carbon, but other materials may also be used. Desirably, the cerium oxide content of at least the inner surface of the container 21 and at least the surfaces of the grinding balls 25 is 100%.

[0031] The container 21 and the grinding balls 25 may each be entirely made of a material containing cerium oxide as a main component. However, since cerium oxide is a relatively inexpensive material, only the inner surface of the container 21 and a predetermined thickness of the surface of the grinding balls 25 may be made of a material containing cerium oxide as a main component.

[0032] As shown in Fig. 3, for example, the grinding ball 25 has a ball body 25a containing at least one of zirconia and alumina, and a coating layer (first coating layer) 25b containing cerium oxide as a main component provided on the surface of the ball body 25a. For example, the grinding ball may be a grinding ball of a conventional ball mill apparatus provided with a coating layer containing cerium oxide as a main component. This reduces the amount of cerium oxide used, which is relatively expensive, and prevents an increase in the cost of the ball mill apparatus 20. Furthermore, by using zirconia or alumina, which are stronger than cerium oxide, for the main body, a decrease in the grinding efficiency of the catalyst particles to be ground can be prevented.

[0033] 4, the container 21 has a stainless steel container body 21a and a coating layer (second coating layer) 21b, which is mainly composed of cerium oxide and is provided on the inner surface of the container body 21a. For example, the container 21 may be a conventional ball mill container with a coating layer mainly composed of cerium oxide provided on the inner surface. This reduces the amount of cerium oxide used, which is relatively expensive, and prevents an increase in the cost of the ball mill device 20.

[0034] 5, the container 21 may also include a protective layer 21c formed below the coating layer 21b, which is primarily composed of cerium oxide, and made of a material with higher abrasion resistance than cerium oxide. By providing such a protective layer 21c, even if the coating layer 21b of the container 21 thins with use, it is possible to prevent the stainless steel or other material contaminants from being mixed in with the ball bodies 25a of the grinding balls 25 due to wear of the container body 21a. To reduce the types of contaminants that may occur when the coating layer 21b of the container 21 and the coating layer 25b of the grinding balls 25 thin with use, the protective layer 21c may be made of the same material as the ball bodies 25a, such as zirconia or alumina.

[0035] Alternatively, the particle size of the cerium oxide present on at least the surface of the inner surface of the container 21 and at least the surface of the grinding balls 25 may be adjusted, and the surface roughness of the inner surface of the container 21 and the surface of the grinding balls 25 may be designed to an appropriate roughness. This makes it possible to control the particle size of cerium oxide that is mixed into the catalytic ink due to wear of the container 21 or the grinding balls 25. For example, if the particle size of the cerium oxide is small and the surface roughness of the inner surface of the container 21 and the surface of the grinding balls 25 is low, the risk of the surface of the container 21 or the grinding balls 25 peeling off is reduced, improving durability, but if peeling does occur, the size of the peeled pieces may be large. If the particle size of the cerium oxide mixed into the catalytic ink is too large, the area where the catalytic reaction occurs in the formed electrode catalyst layer may be blocked, potentially reducing the power generation efficiency of the fuel cell.

[0036] On the other hand, if the particle size of the cerium oxide mixed into the catalyst ink is too small, it may be difficult to arrange it in a position where it is effective as a radical quencher. Therefore, the crystal particle size of the cerium oxide may be smaller than the particle size of the conductive support of the catalyst particles used to form the electrode catalyst layer of the fuel cell, and may be, for example, in the range of 10 nm to 50 nm. This allows the catalyst ink to function effectively as a radical quencher for the fuel cell, even if wear debris from the inner surface of the container 21 and the grinding balls 25 is mixed into the catalyst ink.

[0037] In particular, the crystal grain size of the cerium oxide may be equal to the average grain size of the cerium oxide mixed as a radical quencher in the electrode catalyst layer. Note that "the crystal grain size is equal to the average grain size" includes, for example, the crystal grain size being within a range of plus or minus 5 nm of the average grain size.

[0038] <4. Method for manufacturing electrode catalyst layer> Next, an example of a method for manufacturing an electrode catalyst layer of a fuel cell using the above-mentioned ball mill apparatus will be described. Note that the method for manufacturing an electrode catalyst layer according to this embodiment can be performed in the same manner as a conventional method for manufacturing an electrode catalyst layer, except that the above-mentioned ball mill apparatus is used. Below, first and second examples of the method for manufacturing an electrode catalyst layer will be briefly described, but the method can also be applied to manufacturing methods other than the first and second examples.

[0039] (4-1. First example) The first example of the method for manufacturing an electrode catalyst layer includes a catalyst particle preparation step of preparing catalyst particles, and a catalyst ink preparation step of preparing a catalyst ink by stirring a mixed dispersion containing the catalyst particles, an ionomer, and a solvent, and the catalyst ink preparation step uses the above-mentioned ball mill apparatus in which at least the surfaces of the milling balls and the inner surface of the container are each composed mainly of cerium oxide.

[0040] (Catalyst particle preparation process) First, a conductive support such as a carbon support is prepared, and a catalytic metal is supported on the conductive support to produce catalyst particles. A conventionally known method may be used to support the catalytic metal on the conductive support. For example, the catalytic metal may be mixed with a support dispersion in which a carbon support is dispersed, and the mixture may be redispersed in ethanol or the like after filtering and washing, and then dried using a vacuum pump or the like.

[0041] The conductive support may be any material that is in the form of fine particles, has conductivity, and is not affected by the catalyst, such as carbon black, graphite, activated carbon, carbon fiber, carbon nanotubes, and fullerene.

[0042] The catalytic metal may include at least one of platinum and a platinum alloy, such as an alloy of platinum and at least one metal material selected from the group consisting of tin, molybdenum, cobalt, iridium, ruthenium, rhodium, nickel, and gold.

[0043] The catalyst particle preparation step is not limited to the step of preparing the catalyst support. For example, a nitrogen-doped carbon catalyst may be prepared by heat-treating a precursor containing carbon, nitrogen, a transition metal, and the like in an atmosphere of an inert gas or ammonia.

[0044] (Catalyst ink preparation process) Next, the prepared catalyst particles are mixed with an ionomer and a solvent to prepare a mixed dispersion, and the mixed dispersion is stirred using a ball mill device 20 to pulverize the catalyst particles, thereby preparing a catalyst ink. In the catalyst ink preparation step, the catalyst particles are pulverized by the ball mill device 20, and the ionomer penetrates into the pores of the catalyst particles. This allows the ionomer to coat the surface of the catalyst metal.

[0045] The ionomer may be a proton-conductive one, for example, a perfluorosulfonic acid resin such as Nafion (registered trademark). The solvent is not particularly limited and may be appropriately selected depending on the ionomer to be used, etc. The solvent may be, for example, water, alcohols, ketones, ethers, sulfoxides, amides, or mixtures thereof.

[0046] In this embodiment, cerium oxide is mixed into the mixed dispersion as a radical quencher. However, if cerium oxide is mixed only into the electrolyte membrane of the fuel cell, cerium oxide does not need to be mixed into the catalyst ink.

[0047] Even if wear debris generated by wear of the container 21 and the grinding balls 25 of the ball mill device 20 gets mixed into the catalyst ink during the catalyst ink preparation process, most of the wear debris becomes cerium oxide particles, which therefore function as radical entanglers in the fuel cell and do not become foreign matter.

[0048] (Electrode catalyst layer formation process) The catalyst ink is then processed into a sheet to form an electrode catalyst layer. For example, the catalyst ink is applied or sprayed onto a transfer substrate, followed by degassing and drying to form the electrode catalyst layer. The formed electrode catalyst layer is then bonded to the electrolyte membrane by thermocompression bonding. Alternatively, the catalyst ink may be applied or sprayed directly onto the electrolyte membrane, followed by removing the solvent and drying to form the electrode catalyst layer directly on the electrolyte membrane.

[0049] (4-2. Second example) A second example of the method for producing an electrode catalyst layer includes a catalyst particle preparation step of preparing catalyst particles, an ionomer coating step of coating the catalyst particles with an ionomer, and a catalyst ink preparation step of stirring a mixed dispersion containing the ionomer-coated catalyst particles and a solvent to prepare a catalyst ink, and in at least one of the ionomer coating step and the catalyst ink preparation step, the above-mentioned ball mill apparatus is used, in which at least the surfaces of the milling balls and the inner surface of the container are made primarily of cerium oxide.

[0050] (Catalyst particle preparation process) First, similarly to the first example, a conductive support such as a carbon support is prepared, and a catalyst metal is supported on the conductive support to produce catalyst particles.

[0051] (Ionomer coating process) Next, the prepared catalyst particles are coated with an ionomer. In the ionomer coating step, the catalyst particles are pulverized in a ball mill 20, and the ionomer penetrates into the pores of the catalyst particles. This allows the ionomer to coat the surface of the catalyst metal. The coating method is not particularly limited and may be, for example, a method using a homogenizer, a ball mill, a shear mixer, a roll mill, etc. In the present disclosure, a ball mill device 20 is used in at least one of the ionomer coating process and the catalyst ink preparation process.

[0052] Even if wear debris generated by wear of the container 21 and the grinding balls 25 of the ball mill device 20 gets mixed into the catalyst particles during the ionomer coating process, most of the wear debris becomes cerium oxide particles, which therefore function as radical entanglers in the fuel cell and do not become foreign matter.

[0053] (Catalyst ink preparation process) Next, a solvent is mixed with the ionomer-coated catalyst particles to prepare a mixed dispersion, and the mixed dispersion is stirred using a ball mill 20 to pulverize the catalyst particles, thereby preparing a catalyst ink. In this embodiment, cerium oxide is mixed into the mixed dispersion as a radical quencher. However, if cerium oxide is mixed only into the electrolyte membrane of the fuel cell, cerium oxide does not need to be mixed into the catalyst ink.

[0054] Even if wear debris generated by wear of the container 21 and the grinding balls 25 of the ball mill device 20 gets mixed into the catalyst ink during the catalyst ink preparation process, most of the wear debris becomes cerium oxide particles, which therefore function as radical entanglers in the fuel cell and do not become foreign matter.

[0055] (Electrode catalyst layer formation process) Next, as in the first example, the catalyst ink is processed into a sheet to form an electrode catalyst layer.

[0056] <5. Effects> As described above, the method for manufacturing an electrode catalyst layer for a fuel cell according to the present disclosure uses a ball mill apparatus 20 equipped with a container 21, at least the inner surface of which is primarily composed of cerium oxide, and grinding balls 25, at least the surfaces of which are primarily composed of cerium oxide. Cerium oxide is a substance that functions as a radical quencher that suppresses deterioration of the electrolyte membrane of a fuel cell. Therefore, even if wear debris generated by wear of the container 21 and grinding balls 25 of the ball mill apparatus 20 gets mixed into the catalyst ink, it does not become a foreign substance for the fuel cell. Therefore, a decrease in the power generation efficiency of the fuel cell can be suppressed.

[0057] In the ball mill apparatus 20 of the present disclosure, the grinding balls 25 may include a ball body 25a containing at least one of zirconia and alumina and a coating layer 25b containing cerium oxide as a main component provided on the surface of the ball body 25a, and the container 21 may include a coating layer 21b containing cerium oxide as a main component provided on the inner surface of the container 21 and a protective layer 21c made of a material having a higher abrasion resistance than cerium oxide and provided below the coating layer 21b. This prevents contamination caused by wear of the container 21 from including unnecessary foreign matter other than the constituent material of the grinding balls 25.

[0058] Furthermore, in the ball mill apparatus 20 of the present disclosure, by making the crystal grain size of the cerium oxide present on at least the surface of the inner surface of the container 21 and at least the surfaces of the milling balls 25 smaller than the grain size of the catalyst particles, it is possible to prevent a decrease in the power generation efficiency of the fuel cell from being caused by the cerium oxide particles being too large, which would block the area where the catalytic reaction occurs in the electrode catalyst layer. Furthermore, even if wear debris from the inner surface of the container 21 and the milling balls 25 gets mixed into the catalyst ink, it can still function effectively as a radical quencher for the fuel cell.

[0059] Furthermore, in the ball mill apparatus 20 of the present disclosure, by making the crystal particle size of the cerium oxide on at least the surface of the inner surface of the container 21 and on at least the surface of the grinding balls 25 equal to the average particle size of the cerium oxide mixed as a radical quencher into the catalyst particles, even if wear debris from the inner surface of the container 21 and the grinding balls 25 gets mixed into the catalyst ink, it can function effectively as a radical quencher for the fuel cell.

[0060] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the technology of the present disclosure is not limited to such examples. It is clear that a person skilled in the art of the technology to which the present disclosure pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0061] 10: Fuel cell 11: Electrolyte membrane 13: Anode electrode 13a: Anode catalyst layer (electrode catalyst layer) 13b: Anode diffusion layer 15: Cathode electrode 15a: Cathode catalyst layer (electrode catalyst layer) 15b: Cathode diffusion layer 17: First separator 19: Second separator 20: Ball mill device 21: Container 21a: Container body 21b: Coating layer (second coating layer) 21c: Protective layer 23: Lid 25: Grinding balls 25a: Ball body 25b: Coating layer (first coating layer) 27: Rotating device

Claims

1. A method for manufacturing an electrode catalyst layer of a fuel cell provided in a fuel cell, comprising: a catalyst particle preparation step of preparing catalyst particles; a catalyst ink preparation step of preparing a catalyst ink by stirring a mixed dispersion liquid containing the catalyst particles, an ionomer, and a solvent, In the catalyst ink preparation step, a ball mill apparatus is used in which at least the surfaces of the grinding balls and the inner surface of the container are made primarily of cerium oxide.

2. A method for manufacturing an electrode catalyst layer provided in a fuel cell, comprising: a catalyst particle preparation step of preparing catalyst particles; an ionomer coating step of coating the catalyst particles with an ionomer; a catalyst ink preparation step of preparing a catalyst ink by stirring a mixed dispersion containing the ionomer-coated catalyst particles and a solvent, In at least one of the ionomer coating step and the catalyst ink preparation step, a ball mill apparatus is used in which at least the surfaces of the milling balls and the inner surface of the container are each composed mainly of cerium oxide.

3. a container having at least the inner surface thereof mainly composed of cerium oxide; A ball mill device comprising: grinding balls whose surfaces are at least mainly composed of cerium oxide.

4. The grinding ball comprises a ball body containing at least one of zirconia and alumina, and a first coating layer formed on the surface of the ball body and containing cerium oxide as a main component, 4. The ball mill apparatus according to claim 3, wherein the container comprises: a second coating layer formed on the inner surface of the container and containing cerium oxide as a main component; and a protective layer formed below the second coating layer and made of a material having higher abrasion resistance than cerium oxide.

5. the ball mill device is used to pulverize catalyst particles to be mixed into an electrode catalyst layer of a fuel cell; the crystal grain size of the cerium oxide present at least on the surface of the inner surface of the container and at least on the surfaces of the grinding balls is smaller than the grain size of the catalyst particles; The ball mill apparatus according to claim 3 .

6. the ball mill device is used to pulverize catalyst particles to be mixed into an electrode catalyst layer of a fuel cell; the crystal grain size of the cerium oxide on at least the surface of the inner surface of the container and on at least the surfaces of the grinding balls is equal to the average grain size of the cerium oxide mixed as a radical quencher with the catalyst particles; The ball mill apparatus according to claim 3 .

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