Method for manufacturing fuel cell

Abstract

The present invention relates to a method for manufacturing a fuel cell. The method for manufacturing a fuel cell comprises: a step of stacking a gas diffusion layer such as an anode diffusion layer (20) and a cathode diffusion layer (22), and a catalyst layer such as an anode catalyst layer (16) and a cathode catalyst layer (18) on an electrolyte membrane (14) and performing pressurization and heating sintering to form an electrolyte membrane-electrode structure (12); a preparatory treatment step of bringing superheated water vapor into contact with the electrolyte membrane-electrode structure (12); and an aging step of applying a voltage of a predetermined waveform between the anode electrode (26) and the cathode electrode (28) of the electrolyte membrane-electrode structure (12) that has undergone the preparatory treatment step.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a fuel cell. Background Art

[0002] In the manufacturing process of the fuel cell stack, the catalyst layer and the diffusion layer are bonded to both sides of the electrolyte membrane to form an electrolyte membrane-electrode structure. Then, the electrolyte membrane-electrode structure is sandwiched between the separator with the anode flow path and the separator with the cathode flow path to form a power generation cell. In addition, the power generation cells are stacked in dozens to hundreds of layers. Moreover, the stacked power generation cells are sandwiched between a pair of end panels, and a tightening load in the thickness direction is applied to make them integrated. The fuel cell stack is manufactured through the above process.

[0003] After that, a process is performed to activate the electrolyte membrane-electrode structure in the fuel cell stack. As an activation process, for example, a method of supplying hydrogen to the fuel cell stack and repeatedly generating electricity with a large current (power generation aging method) has been proposed. A method of supplying a small amount of hydrogen while applying a voltage of a predetermined waveform pattern to the fuel cell stack has also been proposed (Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5587286 Summary of the invention

[0007] Problems to be solved by the invention

[0008] According to the activation method of Patent Document 1, compared with the general power generation aging method, there is an advantage of being able to significantly reduce hydrogen consumption and processing time. However, for electrolyte membrane-electrode structures of different specifications formed by changing the process of bonding the catalyst layer and the diffusion layer to both sides of the electrolyte membrane, it was found in the activation method of Patent Document 1 that a sufficient activation effect cannot be obtained within the expected processing time. That is, in the activation method of Patent Document 1, there is a situation where, although the activation effect of the desorption reaction of hydrogen in the anode electrode is excellent, the activation effect of the redox reaction of the cathode electrode is not sufficient.

[0009] In order to obtain the desired activation effect, it is conceivable to perform a power generation aging method, but there is a problem that a large amount of hydrogen is required.

[0010] Therefore, an object of the present invention is to provide a method for manufacturing a fuel cell that can suppress hydrogen consumption and obtain a sufficient activation effect in a short time even when the manufacturing process of an electrolyte membrane-electrode assembly is changed.

[0011] Solutions for solving problems

[0012] One aspect of the present invention relates to a method for manufacturing a fuel cell, comprising: a step of stacking a gas diffusion layer and a catalyst layer on an electrolyte membrane and pressurizing and heating the electrolyte membrane to form an electrolyte membrane-electrode structure; a preliminary treatment step of bringing superheated water vapor into contact with the electrolyte membrane-electrode structure; and an aging step of applying a periodically varying voltage between an anode electrode and a cathode electrode of the electrolyte membrane-electrode structure that has undergone the preliminary treatment step.

[0013] Effects of the Invention

[0014] The manufacturing method of the fuel cell of the above viewpoint includes a preparatory treatment step of supplying superheated water vapor. Therefore, the barrier layer of the cathode electrode generated by the step of forming the electrolyte membrane-electrode structure can be removed, thereby improving the discharge performance of the generated water of the gas diffusion layer of the cathode electrode. As a result, the manufacturing method of the fuel cell of the above viewpoint can eliminate the diffusion barrier of oxygen to the catalyst layer on the cathode electrode side, thereby exerting a sufficient activation effect on the redox reaction of the cathode electrode.

[0015] The following embodiments will be described with reference to the accompanying drawings, and the above-mentioned objects, features, and advantages will be easily understood based on the description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a cross-sectional view showing a step of forming a catalyst on an electrolyte membrane according to an embodiment.

[0017] Figure 2 It means in Figure 1 A cross-sectional view showing a process of laminating an anode diffusion layer and a cathode diffusion layer on an electrolyte membrane.

[0018] Figure 3 It means to make Figure 2 A cross-sectional view of the process of integrating a stacked structure to form an electrolyte membrane-electrode structure.

[0019] Figure 4 It means to Figure 3 A cross-sectional view of a process of supplying superheated water vapor to both surfaces of an electrolyte membrane-electrode assembly.

[0020] Figure 5 It means in Figure 4 An explanatory diagram of the process of joining the electrolyte membrane-electrode structure to the frame member.

[0021] Figure 6 It is an explanatory diagram showing a process of laminating a framed electrolyte membrane-electrode assembly and a separator to form a fuel cell stack.

[0022] Figure 7This is an explanatory diagram showing a process of applying a voltage of a predetermined waveform to a fuel cell stack for aging. DETAILED DESCRIPTION

[0023] The method for manufacturing a fuel cell according to this embodiment is as follows Figure 1 to Figure 7 First, the steps are described. Figure 1 to Figure 3 The process of forming the electrolyte membrane-electrode assembly 12 is shown.

[0024] like Figure 1 As shown, in the initial process, an anode catalyst layer 16 is formed on one side of the electrolyte membrane 14, and a cathode catalyst layer 18 is formed on the other side of the electrolyte membrane 14. The electrolyte membrane 14 is formed of a polymer solid electrolyte such as a fluorine-based resin having hydrogen conductivity. The electrolyte membrane 14 is provided as a sheet rolled into a roll. The rolled electrolyte membrane 14 is stretched. An ink containing an anode catalyst is applied to one side of the electrolyte membrane 14. An ink containing a cathode catalyst is applied to the other side of the electrolyte membrane 14. The electrolyte membrane 14 coated with the ink containing the catalyst is fired to a predetermined temperature in a heating furnace to form an anode catalyst layer 16 and a cathode catalyst layer 18. Moreover, the ink containing the anode catalyst and the ink containing the cathode catalyst contain at least a proton conductive resin (electrolyte component) in addition to carbon particles (catalyst particles) carrying a metal catalyst. In the subsequent process, the electrolyte membrane 14 formed with the anode catalyst layer 16 and the cathode catalyst layer 18 is wound into a roll.

[0025] Then, in Figure 2 In the process shown, the electrolyte membrane 14 is stretched into a sheet. In the subsequent process, the anode diffusion layer 20 is stacked on the anode catalyst layer 16, and the cathode diffusion layer 22 is stacked on the cathode catalyst layer 18. After the fluorine-based water-repellent is fixed to the surface of the main diffusion layer 20a formed of a porous sheet such as carbon paper, the microporous layer 20b is applied and fired to form the anode diffusion layer 20. The microporous layer 20b is a layer having pores with a smaller diameter than the main diffusion layer 20a. The anode diffusion layer 20 is stacked on the anode catalyst layer 16 in a manner that the microporous layer 20b is adjacent to the anode catalyst layer 16.

[0026] In addition, the cathode diffusion layer 22 is made in the same manner as the anode diffusion layer 20. That is, a waterproofing agent is fixed to the surface of a main diffusion layer 22a formed of a porous sheet such as carbon paper. Thereafter, a microporous layer 22b is applied and fired on the surface of the main diffusion layer 22a to form the cathode diffusion layer 22. Alternatively, the microporous layer 22b of the cathode diffusion layer 22 may be composed of a plurality of layers having different pore diameters. The cathode diffusion layer 22 is laminated on the electrolyte membrane 14 in such a manner that the microporous layer 22b is adjacent to the cathode catalyst layer 18.

[0027] Through the above process, Figure 2 The stacked structure 24 shown is completed. Furthermore, the order of stacking the anode diffusion layer 20 and the cathode diffusion layer 22 is not limited to the order described above. The cathode diffusion layer 22 may be stacked before the anode diffusion layer 20, or both may be stacked at the same time. Figure 2 The sheet-like stacked structure 24 having the cross-sectional structure shown is formed by cutting into a predetermined shape, such as a rectangular shape of a predetermined size, which matches the size of the fuel cell.

[0028] Then, if Figure 3 As shown, the stacked structure 24 is pressurized and heated using a pressurizing device 29. Thus, the anode diffusion layer 20 and the cathode diffusion layer 22 are integrated with the electrolyte membrane 14 to form the electrolyte membrane-electrode structure 12. In this process, the bonding strength between the electrolyte membrane 14 and the anode catalyst layer 16, and the bonding strength between the electrolyte membrane 14 and the cathode catalyst layer 18 are increased. That is, the electrolyte components contained in the anode catalyst layer 16 penetrate into the gaps of the anode diffusion layer 20. In addition, the electrolyte components contained in the cathode catalyst layer 18 penetrate into the gaps of the cathode diffusion layer 22. Moreover, the infiltrated electrolyte components act like adhesives. As a result, the anode diffusion layer 20 and the cathode diffusion layer 22 are firmly bonded and integrated with the electrolyte membrane 14. Thus, an anode electrode 26 formed by stacking the anode catalyst layer 16 and the anode diffusion layer 20 in sequence is formed on one side of the electrolyte membrane 14. Furthermore, a cathode electrode 28 in which the cathode catalyst layer 18 and the cathode diffusion layer 22 are stacked in this order is formed on the other surface of the electrolyte membrane 14 , and the electrolyte membrane-electrode assembly 12 is completed.

[0029] In the electrolyte membrane-electrode structure 12 formed in the above process, a bonding interface layer 30a containing a large amount of solid electrolyte is formed near the interface between the anode catalyst layer 16 and the microporous layer 20b of the anode diffusion layer 20. A bonding interface layer 30c containing a large amount of solid electrolyte is formed near the interface between the cathode catalyst layer 18 and the microporous layer 22b of the cathode diffusion layer 22. In this way, according to the manufacturing method of the fuel cell of this embodiment, compared with the case where the anode catalyst layer 16 is formed on the microporous layer 20b of the anode diffusion layer 20 and then bonded to the electrolyte membrane 14, it is easy to form a bonding interface layer 30a (barrier layer) that hinders the movement of substances at the interface between the microporous layer 20b and the anode catalyst layer 16. In addition, at the interface of the cathode catalyst layer 18, the bonding interface layer 30c is also formed as a barrier layer.

[0030] Therefore, in this embodiment, if Figure 4As shown, a preliminary treatment process is performed to supply superheated water vapor to the electrolyte membrane-electrode assembly 12. In the preliminary treatment process, superheated water vapor is supplied to the anode electrode 26 and the cathode electrode 28 of the electrolyte membrane-electrode assembly 12, respectively. The superheated water vapor is supplied in a pressurized and heated state. In addition, the superheated water vapor is sprayed and supplied in a manner of blowing to the anode electrode 26 and the cathode electrode 28 as a fluid composed only of H2O molecules.

[0031] In the heat treatment with superheated water vapor, the configuration of the superheated water vapor injection nozzle (not shown) and the electrolyte membrane-electrode assembly 12 is carefully considered. Therefore, even without gas replacement, heat treatment can be performed in a low-oxygen or oxygen-free state. Specifically, the electrolyte membrane-electrode assembly 12 is covered with a cover (not shown) that prevents the inflow of the surrounding atmosphere (oxygen). The pressure in the cover is adjusted to be higher than the surrounding (atmosphere) and superheated water vapor is supplied from the injection nozzle. Thus, even without gas replacement, heat treatment can be performed in a low-oxygen or oxygen-free state.

[0032] The superheated water vapor has excellent heat conductivity and can be heat treated in an oxygen-free state. In addition, when the superheated water vapor is sprayed in a manner of blowing the superheated water vapor to the anode electrode 26 and the cathode electrode 28, the gas pressure acts. As a result, the heat treatment can be performed without oxidizing the catalyst particles. When the superheated water vapor is supplied to the bonding interface layers 30a and 30c, the moisture in the superheated water vapor swells the particles of the solid electrolyte and increases the fluidity of the solid electrolyte. Moreover, the bonding interface layers 30a and 30c formed by the solid electrolyte with increased fluidity are squeezed and expanded to the surroundings by the jet of the superheated water vapor.

[0033] As a result, the porosity of the bonding interface layers 30a and 30c increases. That is, in the bonding interface layer 30a between the anode diffusion layer 20 and the anode catalyst layer 16, the gaps through which substances (hydrogen or water) can flow increase, thereby improving the diffusivity of hydrogen between the anode diffusion layer 20 and the anode catalyst layer 16. In addition, in the bonding interface layer 30c between the cathode diffusion layer 22 and the cathode catalyst layer 18, the gaps through which substances (oxygen, water) can flow increase, thereby improving the diffusivity of oxygen between the cathode diffusion layer 22 and the cathode catalyst layer 18.

[0034] Then, if Figure 5 As shown, after the preparatory treatment step, the frame member 32 is joined to the electrolyte membrane-electrode structure 12. The frame member 32 is formed of, for example, a resin, and is formed to surround the outer periphery of the electrolyte membrane-electrode structure 12. The frame member 32 is joined near the outer peripheral end of the electrolyte membrane-electrode structure 12. Through the above steps, the electrolyte membrane-electrode structure 34 with a frame is completed.

[0035] Then, if Figure 6 As shown in FIG. 1 , the assembly process is performed to alternately stack a plurality of framed electrolyte membrane-electrode structures 34 and a plurality of separators 36 to assemble a fuel cell stack 38. The two sides of the framed electrolyte membrane-electrode structure 34 in the thickness direction are sandwiched by the separators 36, thereby forming a power generation cell 40. The power generation cell 40 is stacked in dozens to hundreds of layers. In addition, as shown in FIG. Figure 7 As shown, a current collector plate, an insulator plate, and an end plate 42 (not shown) are arranged in order from the inside at each end of the stacked body composed of a plurality of power generation cells 40. Furthermore, a fastening unit 44 is mounted on the end plates 42 at both ends, and the fastening unit 44 applies a fastening load to the stacked body of the power generation cells 40. Thus, the assembly of the fuel cell stack 38 is completed.

[0036] Afterwards, if Figure 7 As shown, the fuel cell stack 38 is subjected to an aging treatment. The aging treatment includes the following steps: a small amount of hydrogen is supplied to the plurality of anode electrodes 26, and a voltage of a predetermined waveform supplied from the power supply device 46 is applied to the fuel cell stack 38. For example, the activation method described in Patent Document 1 can be performed. As a result, the anode catalyst layer 16 and the cathode catalyst layer 18 are activated, thereby improving the power generation performance.

[0037] The fuel cell manufacturing method of the present embodiment is completed through the above steps. The fuel cell manufacturing method of the present embodiment achieves the following effects.

[0038] The manufacturing method of the fuel cell of the present embodiment includes: a process of stacking gas diffusion layers (for example, anode diffusion layer 20 and cathode diffusion layer 22) and catalyst layers (for example, anode catalyst layer 16 and cathode catalyst layer 18) on the electrolyte membrane 14 and pressurizing and heating to form an electrolyte membrane-electrode structure 12; a preparatory treatment process of bringing superheated water vapor into contact with the electrolyte membrane-electrode structure 12; and an aging process of applying a voltage of a predetermined waveform between the anode electrode 26 and the cathode electrode 28 of the electrolyte membrane-electrode structure 12 that has undergone the preparatory treatment process.

[0039] According to the above-described method for manufacturing a fuel cell, by performing the preliminary treatment step of supplying superheated steam, an aging effect equivalent to that of the power generation aging method that generates large current while consuming a large amount of hydrogen can be obtained.

[0040] In the above-mentioned method for manufacturing a fuel cell, a preliminary treatment step is performed to supply superheated water vapor to both the anode electrode 26 side and the cathode electrode 28 side of the electrolyte membrane-electrode assembly 12. This can improve the diffusivity of the bonding interface layer 30a between the anode catalyst layer 16 and the anode diffusion layer 20 and the diffusivity of the bonding interface layer 30c between the cathode catalyst layer 18 and the cathode diffusion layer 22.

[0041] In the above-mentioned method for manufacturing a fuel cell, a preliminary treatment step may be performed to spray a jet of superheated water vapor onto the surface of the electrolyte membrane-electrode assembly 12. In addition to the swelling effect of the superheated water vapor, there is also the effect of gas pressure generated by the jet, thereby being able to more effectively improve the diffusibility of the bonding interface layers 30a, 30c.

[0042] In the above-mentioned method for manufacturing a fuel cell, the preparatory treatment step may be performed in an oxygen-free atmosphere. According to this method, oxidation of the catalyst surface can be prevented.

[0043] The manufacturing method of the fuel cell further includes: a step of bonding separators 36 to both sides of the electrolyte membrane-electrode structure 12 that has undergone the preliminary treatment step to form a power generation cell 40; and a stacking step of stacking a plurality of power generation cells 40 to form a fuel cell stack 38. An aging step may also be performed after the stacking step. According to this structure, a stable aging effect can be obtained regardless of the manufacturing process of the electrolyte membrane-electrode structure 12.

[0044] In the above, the present invention has been described by taking the preferred embodiments as examples. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

Claims

1. A method for manufacturing a fuel cell, comprising: A first step of laminating a gas diffusion layer and a catalyst layer on an electrolyte membrane and performing pressurization and heating sintering to form an electrolyte membrane-electrode structure, wherein a bonding interface layer containing a solid electrolyte and preventing material movement is formed between the gas diffusion layer and the catalyst layer; a preliminary treatment step of bringing superheated water vapor into contact with the electrolyte membrane-electrode assembly formed in the first step; and an aging step of applying a voltage of a predetermined waveform between the anode electrode and the cathode electrode of the electrolyte membrane-electrode assembly that has undergone the pretreatment step, In the preparatory treatment step, the jet of superheated water vapor is sprayed toward the surface of the membrane-electrode assembly to increase the porosity of the bonding interface layer.

2. The method for manufacturing a fuel cell according to claim 1, characterized in that: In the preparatory treatment step, superheated water vapor is supplied to both the anode electrode and the cathode electrode of the membrane-electrode assembly.

3. The method for manufacturing a fuel cell according to claim 1, characterized in that: The preparatory treatment step is performed in an oxygen-free atmosphere.

4. The method for manufacturing a fuel cell according to any one of claims 1 to 3, characterized in that: Also includes: a step of bonding separators to both surfaces of the electrolyte membrane-electrode assembly subjected to the preparatory treatment step to form a power generation cell; as well as a stacking step of stacking a plurality of the power generation cells to form a fuel cell stack; The aging step is performed after the lamination step.

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