JP2024002714A - Method for manufacturing fuel cell assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a fuel cell assembly that can improve power generation performance.

SOLUTION: A method for manufacturing a fuel cell assembly includes a placement step of placing a microporous layer on a base material layer, an application step of applying catalyst ink to the microporous layer, a drying step of drying the applied catalyst ink to form a catalyst layer, and a joining step of joining a laminate obtained in the drying step to at least one surface of an electrolyte layer such that the catalyst layer is in contact with the surface of the electrolyte layer, and in the drying step, the catalyst ink is dried in a condition of 80°C or higher and 150°C or lower and within 1 minute.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present application relates to a method of manufacturing a fuel cell assembly.

In the manufacturing method of a fuel cell, it is mainstream to arrange a catalyst layer in an electrolyte layer. Such techniques are described in, for example, Patent Document 1 and Patent Document 2.

On the other hand, as a new manufacturing method for fuel cells, a micro porous layer (MPL) is placed on a gas diffusion layer (GDL), a catalyst layer is placed on the MPL, and a gas diffusion electrode (GDE) is placed on the MPL. A method has been developed that includes a step of manufacturing a GDE (Gass Diffusion Electrode) and then bonding an electrolyte membrane and a GDE. Such a technique is described in, for example, Non-Patent Document 1.

JP2009-64768A JP 2019-121551 Publication

T. Tanuma et. al. , “Impact Cathode Fabrication on Fuel Cell Performance”, Journal of The Electrochemical Society, Vol 161, No. 1 (2014), pp. F94-F98

In Non-Patent Document 1, the drying conditions of the catalyst layer arranged in the MPL are not specifically described. According to the present inventors, when a catalyst layer is placed in the MPL, the ionomer in the catalyst layer gradually seeps into the MPL together with the solvent, resulting in ionomer segregation in the catalyst layer, which increases concentration overpotential and activation overpotential. However, it was discovered that there is a problem in which the power generation performance (for example, output) of the fuel cell is significantly reduced.

Therefore, in view of the above circumstances, the main purpose of the present disclosure is to provide a method for manufacturing a fuel cell assembly that can improve power generation performance.

The present disclosure provides, as one aspect of solving the above problems, a step of arranging a microporous layer on a base material layer, a step of applying a catalyst ink to the microporous layer, and a step of drying the applied catalyst ink. , a drying step of forming a catalyst layer, and a joining step of joining the laminate obtained in the drying step to at least one surface of the electrolyte layer so that the catalyst layer is in contact with the surface of the electrolyte layer, the drying step Provided is a method for producing an assembly for a fuel cell, in which a catalyst ink is dried at a temperature of 80° C. or more and 150° C. or less and within 1 minute.

According to the method for manufacturing a fuel cell assembly of the present disclosure, power generation performance can be improved.

It is a flowchart of the manufacturing method 1 of the assembly for fuel cells. FIG. 2 is a schematic cross-sectional view of the joined body 100. FIG. 2 is a schematic cross-sectional view of a joined body 200. It is a measurement result of the gas diffusion resistance of an Example and a comparative example. These are the ECSA measurement results of Examples and Comparative Examples. It is a measurement result of the power generation performance of an Example and a comparative example.

[Method for manufacturing fuel cell assembly]
The method for manufacturing a fuel cell assembly of the present disclosure will be described in detail using a fuel cell assembly manufacturing method 1 (hereinafter sometimes referred to as "manufacturing method 1"), which is one embodiment.

FIG. 1 shows a flowchart of method 1 for manufacturing a fuel cell assembly. As shown in FIG. 1, the method 1 for manufacturing a fuel cell assembly includes a placement step S1 of disposing the microporous layer 20 on the base material layer 10, a coating step S2 of coating the microporous layer 20 with catalyst ink, A drying step S3 of drying the applied catalyst ink to form a catalyst layer 30, and a drying step S3 of drying the applied catalyst ink to form a catalyst layer 30 on at least one surface of the electrolyte layer 40 so that the catalyst layer 30 is in contact with the surface of the electrolyte layer 40. A joining step S4 of joining the laminate 50 is provided.

<Placement process S1>
In the placement step S1, the microporous layer 20 is placed on the base layer 10. The method of arranging the microporous layer 20 on the base material layer 10 is not particularly limited, and any known method can be employed.

For example, an MPL ink may be prepared by mixing the material constituting the microporous layer 20 with a solvent, and the obtained MPL ink may be applied to the base material layer 10 and dried. The method of applying the MPL ink is not particularly limited, and any known method can be used. Examples include spray coating, inkjet coating, die coating, and spin coating. Furthermore, the drying conditions for the MPL ink are not particularly limited and can be set as appropriate. For example, it may be dried while being heated.

(Base material layer 10)
The base material layer 10 is not particularly limited as long as the microporous layer 20 can be arranged thereon. For example, the base layer 10 may be a release sheet or a gas diffusion layer. Any release sheet may be used as long as the microporous layer 20 can be removed. Such release sheets are known. For example, resin sheets such as Kapton sheets can be used. The gas diffusion layer is not particularly limited as long as it has conductivity and can flow and diffuse fuel gas (for example, hydrogen) or oxidant gas (for example, oxygen or air). For example, the gas diffusion layer may be made of a conductive member having gas permeability, such as a porous carbon material such as carbon paper or carbon cloth; a porous metal material such as a metal mesh or a metal foam. Further, the gas diffusion layer may be a porous channel made of expanded metal or the like. As the expanded metal, for example, one described in JP-A No. 2012-199093 may be used.

When the base material layer 10 is a release sheet, the release sheet may be removed from the bonded body and the gas diffusion layer may be placed there, as described below. When the base layer 10 is a gas diffusion layer, the microporous layer 20 is formed directly on the gas diffusion layer in step S1. From the viewpoint of improving the adhesiveness between the gas diffusion layer and the microporous layer 20, the microporous layer 20 may be formed directly on the gas diffusion layer. That is, the base material layer 10 may be used as a gas diffusion layer.

(Microporous layer 20)
The microporous layer 20 is a porous layer having electronic conductivity and proton conductivity. Microporous layer 20 includes an ionomer and a conductive material. The ionomer is not particularly limited as long as it has proton conductivity. Examples of the ionomer include fluorine-based ion exchange resins. Specific examples include fluoroalkyl polymers such as polytetrafluoroethylene; fluoroalkyl polymers such as perfluoroalkylsulfonic acid polymers; The conductive material is not particularly limited as long as it has electronic conductivity. Examples include carbon materials such as carbon black and VGCF (vapor grown carbon fiber). The ratio of the ionomer to the conductive material is not particularly limited, and may be set as appropriate depending on the purpose.

<Coating process S2>
In the coating step S2, catalyst ink is coated on the microporous layer 20. The method of applying the catalyst ink to the microporous layer 20 is not particularly limited, and any known method can be employed. Examples include spray coating, inkjet coating, die coating, and spin coating.

(catalyst ink)
The catalyst ink is obtained by mixing the material constituting the catalyst layer 30 and a solvent. The material constituting the catalyst layer 30 includes a catalyst and an ionomer. Although the catalyst is not particularly limited, platinum, platinum alloy, etc. may be used, for example. Further, as the catalyst, a carrier-supported catalyst in which platinum or the like is supported on a conductive carrier may be used. Examples of the conductive carrier include carbon material carriers such as carbon particles. The ionomer is not particularly limited, but the above-mentioned ionomers may be used. The ratio between the catalyst and the ionomer is not particularly limited, and may be set as appropriate depending on the purpose. The solvent is not particularly limited, and examples include water and C1 to C4 lower alcohols. These may be used alone or in combination. The proportion of the solvent is not particularly limited and may be appropriately set depending on the purpose.

<Drying step S3>
In the drying step S3, the catalyst ink applied in the coating step S2 is dried to form the catalyst layer 30. Here, the catalyst ink is dried more rapidly than conventionally. The purpose of the drying step S3 is to remove the solvent in the catalyst ink so that the ionomer and the solvent do not permeate into the microporous layer 20.

According to the present inventors, when the catalyst ink is applied to the microporous layer 20, the ionomer in the catalyst ink gradually permeates into the microporous layer 20 together with the solvent, resulting in ionomer segregation in the catalyst layer 30, which causes concentration overvoltage. It has been found that there is a problem in that the activation overvoltage increases and the power generation performance (for example, output) of the fuel cell significantly decreases. Therefore, in the drying step S3, the catalyst ink is dried more rapidly than before. As a result, it is possible to suppress the ionomer in the catalyst ink from penetrating into the microporous layer 20 together with the solvent, thereby suppressing the ionomer segregation in the catalyst layer 30, and thereby the fuel cell obtained from the assembly has a concentration overvoltage and Activation overvoltage is suppressed and output decrease is suppressed. That is, the fuel cell using the assembly manufactured by manufacturing method 1 can improve gas diffusivity and catalytic activity, and can also improve power generation performance.

The specific drying conditions are that the catalyst ink is dried at 80° C. or higher and 150° C. or lower and within 1 minute. If the drying temperature is less than 80° C., the solvent in the catalyst ink may not be able to be rapidly dried. Therefore, from the viewpoint of rapidly drying the solvent, the drying temperature may be 100° C. or higher. If the drying temperature exceeds 150° C., there is a possibility that the material (catalyst or ionomer) constituting the catalyst layer 30 will not be able to withstand the heat. Therefore, in consideration of the thermal durability of the material constituting the catalyst layer 30, the drying temperature may be set to 140° C. or lower. If the drying time exceeds 1 minute, the ionomer may seep into the microporous layer 20 and the power generation performance of the fuel cell using the assembly 100 may deteriorate. Therefore, from the viewpoint of further suppressing the penetration of the ionomer into the microporous layer 20, the drying time may be 50 seconds or less. The lower limit of the drying time is not particularly limited as long as the catalyst ink can be dried. For example, the drying time may be 10 seconds or more.

The method of drying the catalyst ink is not particularly limited. For example, the catalyst ink may be dried using a dryer or the like while blowing heated air. Alternatively, the catalyst ink may be dried using a heating element such as a hot plate. From the viewpoint of increasing the drying speed, a method of blowing heated air may be adopted as a drying method.

(Catalyst layer 30)
The catalyst layer 30 is formed by drying the catalyst ink. Since the material constituting the catalyst layer 30 has been described above, the description thereof will be omitted here.

<Joining process S4>
In the bonding step S4, the laminate 50 obtained in the drying step S3 is bonded to at least one surface of the electrolyte layer 40 so that the catalyst layer 30 is in contact with the surface of the electrolyte layer 40. As a result, a bonded body 100 is obtained. The laminate 50 is a laminate in which the base material layer 10, the microporous layer 20, and the catalyst layer 30 are laminated. When the base material layer 10 is a gas diffusion layer, the laminate 50 becomes a gas diffusion electrode (GDL).

The method for joining the electrolyte layer 40 and the laminate 50 is not particularly limited, and any known method may be used as appropriate. For example, the electrolyte layer 40 and the laminate 50 may be joined by applying pressure and heating using a hot press or a hot roll. The bonding conditions may be set as appropriate within a range that does not impair the effects of the present disclosure.

The electrolyte layer 40 and the laminate 50 may be bonded to each other only on one side of the electrolyte layer 40 or on both sides. Here, the microporous layer 20 is typically provided only on the cathode side in order to suppress flooding in the fuel cell. Therefore, the electrolyte layer 40 and the laminate 50 may be bonded to only one surface of the electrolyte layer 40.

When joining the laminate 50 to only one surface of the electrolyte layer 40, the electrolyte layer 40 may be used with the catalyst layer 60 disposed on the other surface in advance. Further, in this case, in addition to bonding one surface of the electrolyte layer 40 and the laminate 50, the other surface of the electrolyte layer 40 (catalyst layer 60) and the gas diffusion layer 70 may be bonded. . Alternatively, after the bonding step S4, the gas diffusion layer 70 may be bonded to the other surface (catalyst layer 60) of the electrolyte layer 40.

(Electrolyte layer 40)
The electrolyte layer 40 is not particularly limited as long as it is a resin having proton conductivity. Examples include fluorine-based electrolytes and carbon-based electrolytes. Examples of the fluorine-based electrolyte include polytetrafluoroethylene (PTFE) and perfluorosulfonic acid ionomer.

(Joint body 100, 200)
Next, the joined bodies 100 and 200 manufactured by the manufacturing method 1 will be explained. 2 and 3 show schematic cross-sectional views of the joined bodies 100 and 200. Note that the joined bodies 100 and 200 shown in FIGS. 2 and 3 are only examples, and the joined bodies manufactured by the manufacturing method of the present disclosure are not limited thereto.

First, the joined body 100 will be explained. As shown in FIG. 2, the assembly 100 includes an electrolyte layer 40, catalyst layers 30 and 60 disposed on one and other surfaces of the electrolyte layer 40, and one surface of the catalyst layer 30 (the electrolyte layer 40 is A microporous layer 20 disposed on one surface (opposite surface) of the microporous layer 20, and a base material layer 10 (release sheet) disposed on one surface of the microporous layer 20 (a surface opposite to the catalyst layer 30). ing. By removing the base material layer 10 (release sheet) from such an assembly 100, a membrane electrode assembly 110 can be obtained. Then, by arranging a gas diffusion layer and a separator on both sides of the membrane electrode assembly 110 in the stacking direction, a fuel cell can be manufactured.

Therefore, the manufacturing method 1 may include a step of removing the base material layer 10 after the bonding step S4. Further, as an embodiment, the present disclosure provides manufacturing of a fuel cell including a step of arranging a gas diffusion layer and a separator on both sides of the assembly (membrane electrode assembly 110) obtained by manufacturing method 1 in the stacking direction. A method may be provided.

Next, the joined body 200 will be explained. As shown in FIG. 3, the assembly 200 includes an electrolyte layer 40, catalyst layers 30 and 60 disposed on one side and the other side of the electrolyte layer 40, and one side of the catalyst layer 30 (the electrolyte layer 40 is a microporous layer 20 disposed on one surface of the microporous layer 20 (the surface opposite to the catalyst layer 30); a base layer 10 (gas diffusion layer) disposed on one surface of the microporous layer 20 (the surface opposite to the catalyst layer 30); A gas diffusion layer 70 is provided on the other surface of the layer 60 (the surface opposite to the electrolyte layer 40). Such an assembly 200 is a membrane electrode gas diffusion layer assembly (MEGA). By arranging separators on both sides of the assembly 200 in the stacking direction, a fuel cell can be manufactured.

Therefore, as one embodiment, the present disclosure may provide a method for manufacturing a fuel cell, which includes a step of arranging separators on both sides of the assembly 200 obtained by manufacturing method 1 in the stacking direction.

Here, a known separator may be used as the separator. Examples include a carbon separator made of a composite material containing carbon fiber at a high concentration and a resin, and a metal separator made of a metal material.

The method for manufacturing a fuel cell assembly of the present disclosure has been described above using one embodiment. According to the method for manufacturing a fuel cell assembly of the present disclosure, power generation performance can be improved.

Hereinafter, the present disclosure will be further described using Examples.

[Preparation of zygote for evaluation]
<Example>
MPL ink (materials: carbon black and polytetrafluoroethylene) was applied to a release sheet (Kapton sheet) and dried. A catalyst ink was applied onto the obtained microporous layer and rapidly dried. After the resulting laminate and electrolyte membrane were thermally transferred (joined), the release sheet was removed. A membrane electrode assembly was thereby obtained. Gas diffusion layers were disposed on both sides of the obtained membrane electrode assembly to produce an evaluation assembly of the example.

<Comparative example>
Catalyst ink was applied to the fluorine-based backsheet and dried normally. The obtained catalyst layer was thermally transferred (bonded) to an electrolyte membrane to obtain a membrane electrode assembly. Gas diffusion layers were arranged on both sides of the obtained membrane electrode assembly to produce an evaluation assembly of a comparative example.

[evaluation]
<Gas diffusion resistance>
The gas diffusion resistance of the evaluation assembly was measured by the limiting current method (oxygen concentration 1%). The results are shown in Figure 4.

<Active surface area>
The electrochemically active surface area (ECSA) of the catalyst of the evaluation conjugate was measured by the CV (cyclic voltammetry) method. The results are shown in FIG.

<Power generation performance>
The power generation performance of the evaluation zygote was measured. The results are shown in FIG.

<Results>
From FIGS. 4 to 6, the examples showed higher gas diffusivity, catalytic activity, and power generation performance than the comparative examples. This is considered to be because the rapid drying of the catalyst ink suppressed the ionomer in the catalyst ink from penetrating into the microporous layer together with the solvent, thereby suppressing ionomer segregation in the catalyst layer. On the other hand, since the catalyst ink was not rapidly dried in the comparative example, it is thought that the ionomer in the catalyst ink soaked into the fluorine-based backsheet together with the solvent, resulting in ionomer segregation in the catalyst layer. Therefore, it is considered that the power generation performance decreased due to the increase in concentration overvoltage and activation overvoltage.

10 Base material layer 20 Microporous layer 30 Catalyst layer 40 Electrolyte layer 50 Laminated body 60 Catalyst layer 70 Gas diffusion layer 100, 200 Joined body

Claims (1)

a placement step of placing the microporous layer on the base material layer;
a coating step of applying catalyst ink to the microporous layer;
a drying step of drying the applied catalyst ink to form a catalyst layer;
a joining step of joining the laminate obtained in the drying step to at least one surface of the electrolyte layer so that the catalyst layer is in contact with the surface of the electrolyte layer,
In the drying step, the catalyst ink is dried at a temperature of 80° C. or higher and 150° C. or lower and within 1 minute.
A method for manufacturing a fuel cell assembly.