JP5417687B2 - Method for producing solid polymer electrolyte fuel cell - Google Patents

Description

  The present invention relates to a method for producing a solid polymer electrolyte membrane fuel cell capable of suppressing pressure loss that occurs during a crimping process.

  A unit cell, which is a minimum power generation unit of a solid polymer electrolyte fuel cell (hereinafter sometimes referred to simply as a fuel cell), generally has a catalyst electrode layer (an anode side catalyst electrode layer and an anode side catalyst electrode layer) on both sides of a solid polymer electrolyte membrane. A cathode electrode side catalyst electrode layer), a gas diffusion layer disposed on both sides of the membrane electrode assembly, and a separator disposed outside the gas diffusion layer. Is.

In such a fuel cell, hydrogen (H ₂ ) and oxygen (O ₂ ) react with each other during operation, and generated water (H ₂ O) is generated in the fuel cell. When this generated water remains in the catalyst electrode layer, the generated water covers the catalyst surface and obstructs the contact between the catalyst and hydrogen gas or oxygen gas, so that the power generation efficiency of the fuel cell decreases. Therefore, it is necessary to efficiently discharge the generated water to the outside of the fuel cell, and in general, a water repellent layer is provided between the catalyst electrode layer and the gas diffusion layer. For such a water-repellent layer, for example, a water-repellent material such as a fluorine-based resin is used.

  However, when producing a fuel cell using the water repellent layer, there are the following problems. That is, when manufacturing a fuel cell, the components of the fuel cell are subjected to thermocompression bonding. At this time, if the heating temperature of thermocompression bonding is too high, the water-repellent layer is excessively softened and the thermocompression bonding pressure is equalized. There was a problem of not being transmitted to. As a result, a region with insufficient adhesion occurs between the layers constituting the fuel cell (pressure loss), which may cause a decrease in power generation efficiency of the fuel cell.

  For example, when a hydrocarbon-based electrolyte membrane is used as the solid polymer electrolyte membrane, it is generally necessary to set the heating temperature to about 150 ° C. or higher. In such a case, when polytetrafluoroethylene (PTFE) is used as the water-repellent material constituting the water-repellent layer, PTFE is remarkably softened at about 125 ° C. Problem arises.

  Note that Patent Document 1 discloses a method of manufacturing a fuel cell electrode that suppresses the occurrence of a poor adhesion portion. Specifically, it is disclosed that a hydrocarbon-based solid polymer electrolyte membrane and an electrode substrate are joined by pressure bonding, and a solution containing a fluorine-based resin is applied to a gas diffusion layer. However, since the hydrocarbon-based solid polymer electrolyte membrane has a high glass transition temperature, it has been necessary to heat it to a high temperature during bonding. As a result, the fluororesin (water repellent material) was softened by heat during bonding, causing pressure loss during pressure bonding, and there was a risk of poor adhesion without transmission of pressing force.

JP 2004-14202 A JP 2004-119398 A JP 2003-115302 A JP 2003-107202 A

  The present invention has been made in view of the above problems, and it is possible to suppress a pressure drop that occurs during the crimping process and to obtain a solid polymer electrolyte fuel cell with excellent power generation efficiency. The main object is to provide a method for producing a molecular electrolyte fuel cell.

  In order to achieve the above object, in the present invention, a water-repellent layer is formed by applying a water-repellent layer-forming composition containing a water-repellent material, a conductive material and a shape-retaining material to a gas diffusion layer. Forming a catalyst electrode layer containing an electrolyte material having a glass transition temperature higher than the softening temperature of the water repellent material on at least one of the water repellent layer and the solid polymer electrolyte membrane; And a thermocompression bonding step of thermocompression bonding the gas diffusion layer and the solid polymer electrolyte membrane so as to sandwich the water repellent layer and the catalyst electrode layer. A method for manufacturing a fuel cell is provided.

  According to the present invention, by including a shape-retaining material in the water-repellent layer, even when thermocompression bonding is performed at a heating temperature equal to or higher than the softening temperature of the water-repellent material, pressure relief due to softening of the water-repellent layer is achieved. Occurrence can be suppressed. That is, the thermocompression bonding step needs to be performed in a state where the catalyst electrode layer and the like are melted to some extent from the viewpoint of realizing good adhesion. Therefore, the heating temperature at the time of thermocompression bonding may be set near the glass transition temperature of the electrolyte material included in the catalyst electrode layer. In the present invention, since the glass transition temperature of the electrolyte material is higher than the softening temperature of the water-repellent material, when thermocompression bonding is performed at a heating temperature near the glass transition temperature of the electrolyte material, the water-repellent material is inevitably It can soften and cause pressure loss. In the present invention, even when thermocompression bonding is performed at a heating temperature at which the water-repellent material is softened, the water-repellent layer contains a shape-retaining material, thereby suppressing the softening of the entire water-repellent layer and reducing pressure loss. Occurrence can be prevented.

  Further, from the viewpoint of improving the power generation efficiency of the fuel cell, it is preferable to operate the fuel cell at a higher temperature. For this purpose, it is necessary to use a material having a high glass transition temperature for the electrolyte material contained in the catalyst electrode layer, the solid polymer electrolyte membrane, or the like. Specifically, a case where a hydrocarbon-based material is used as the electrolyte material and the solid polymer electrolyte membrane can be considered. In order to press-bond such a material having a high glass transition temperature, heat is applied at a higher temperature. It is necessary to perform a crimping process, and the above-described problem of pressure loss may occur remarkably. According to the present invention, even in such a case, the occurrence of pressure loss can be suppressed by using the shape-retaining material.

  Moreover, in the said invention, it is preferable that the glass transition temperature of the said electrolyte material is 130 degreeC or more. This is because even when an electrolyte material having a high glass transition temperature is used, the occurrence of pressure loss can be suppressed and a fuel cell excellent in power generation efficiency can be obtained.

  In the above invention, the water repellent material is preferably polytetrafluoroethylene. This is because a water repellent layer having excellent water repellency can be obtained.

  In the present invention, a water repellent layer forming step of applying a water repellent layer-forming composition containing a water repellent material, a conductive material and a shape-retaining material to a gas diffusion layer to form a water repellent layer; A catalyst electrode layer forming step of forming a catalyst electrode layer on at least one of a water repellent layer and a solid polymer electrolyte membrane having a glass transition temperature higher than a softening temperature of the water repellent material; and the solid polymer electrolyte membrane, And a thermocompression bonding step of thermocompression bonding the gas diffusion layer so as to sandwich the water repellent layer and the catalyst electrode layer. A method for producing a solid polymer electrolyte fuel cell is provided.

  According to the present invention, even when the water-repellent material is softened by thermocompression bonding at a high temperature, the presence of the shape-retaining material can suppress the pressure release, and the catalyst electrode layer and the solid polymer electrolyte Adhesion failure at the interface with the film can be suppressed.

  In the present invention, it is possible to suppress the pressure loss generated during the pressure bonding step, and it is possible to obtain a solid polymer electrolyte membrane fuel cell excellent in adhesion and power generation efficiency.

  Hereinafter, the method for producing a solid polymer electrolyte fuel cell of the present invention will be described in detail. The method for producing a solid polymer electrolyte fuel cell of the present invention can be roughly divided into two embodiments. Hereinafter, a method for producing a solid polymer electrolyte fuel cell of the present invention will be described for each embodiment.

A. First Embodiment First, a first embodiment of the method for producing a solid polymer electrolyte fuel cell of the present invention will be described. In this embodiment, the glass transition temperature of the electrolyte material included in the catalyst electrode layer is higher than the softening temperature of the water-repellent material included in the water-repellent layer.

  That is, in the method for producing a solid polymer electrolyte fuel cell according to this embodiment, a water repellent layer-forming composition containing a water repellent material, a conductive material and a shape-retaining material is applied to a gas diffusion layer, And forming a catalyst electrode layer containing an electrolyte material having a glass transition temperature higher than the softening temperature of the water-repellent material on at least one of the water-repellent layer and the solid polymer electrolyte membrane. And a thermocompression bonding step of thermocompression bonding the gas diffusion layer and the solid polymer electrolyte membrane so as to sandwich the water repellent layer and the catalyst electrode layer. Is.

  Next, the manufacturing method of the solid polymer electrolyte fuel cell of this embodiment is demonstrated using drawing. FIG. 1 is a process diagram showing an example of a method of manufacturing a fuel cell according to this embodiment. As shown in FIG. 1A, a water repellent layer 2 is formed on a gas diffusion layer 1 by applying a water repellent layer forming composition containing a water repellent material, a conductive material and a shape-retaining material. As shown in FIG. 1 (b), for example, a water layer forming step, a catalyst electrode layer forming step for forming the catalyst electrode layer 3 on the water repellent layer 2, and a gas diffusion layer as shown in FIG. 1 (c). 1 and a thermocompression bonding process in which the solid polymer electrolyte membrane 4 is thermocompression bonded so as to sandwich the water repellent layer 2 and the catalyst electrode layer 3. In this embodiment, the glass transition temperature of the electrolyte material included in the catalyst electrode layer 3 is higher than the softening temperature of the water repellent material included in the water repellent layer 2. Therefore, if the heating temperature at the time of thermocompression bonding is set near the glass transition temperature of the electrolyte material, the water repellent material may soften and cause pressure loss. In this embodiment, the water repellent layer 2 has a shape. By containing the holding material, softening of the water repellent layer 2 as a whole can be suppressed, and occurrence of pressure loss can be prevented. In this embodiment, as shown in FIG. 1 (d), two laminated bodies 5 each having a gas diffusion layer 1, a water repellent layer 2 and a catalyst electrode layer 3 are used to form a solid polymer electrolyte membrane 4. It may be installed so that both surfaces and the catalyst electrode layer 2 are in contact with each other, and thermocompression bonding may be performed.

  The fuel cell manufacturing method of this embodiment includes a water repellent layer forming step, a catalyst electrode layer forming step, and a thermocompression bonding step. Each step will be described in detail below.

1. Water repellent layer forming step First, the water repellent layer forming step in the present embodiment will be described. The water repellent layer forming step is a step of forming a water repellent layer by applying a water repellent layer forming composition containing a water repellent material, a conductive material and a shape-retaining material to the gas diffusion layer.

  FIG. 2 is a schematic cross-sectional view showing an example of a water-repellent layer obtained by this step. As shown in FIG. 2, the water repellent layer 2 obtained by this step is formed on the gas diffusion layer 1 and has at least a water repellent material 6, a conductive material 7, and a shape retaining material 8. is there. The water repellent layer usually has a porous structure in order to allow gas to pass therethrough.

  Here, the water repellent material contained in the water repellent layer forming composition will be described first. The water repellent material imparts water repellency to the water repellent layer. Further, the water repellent material has a softening temperature lower than the glass transition temperature of the electrolyte material contained in the catalyst electrode layer, as will be described later. In the present embodiment, the “softening temperature of the water repellent material” refers to the temperature at which the elastic modulus of the water repellent material at 25 ° C. is measured and the value decreases to 1/5. In this embodiment, the softening temperature of the water-repellent material is not particularly limited as long as it is lower than the glass transition temperature of the electrolyte material contained in the catalyst electrode layer, but is usually in the range of 100 to 130 ° C. Is within.

  The water repellent material is not particularly limited as long as it has water repellency and can discharge generated water generated by the operation of the fuel cell to the outside of the fuel cell. Can be mentioned. Specific examples of such fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), and tetrafluoroethylene-perfluoroalkyl vinyl ether. Copolymer (PFA), perfluoroethylene-propene copolymer (FEP), vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, fluoroolefin-hydrocarbon copolymer, fluoroacrylate Examples thereof include a copolymer and a fluoroepoxy compound. Among these, in this embodiment, polytetrafluoroethylene and polyvinylidene fluoride are preferable, and polytetrafluoroethylene is particularly preferable. This is because a water repellent layer having excellent water repellency can be obtained.

  The content of the water-repellent material in the composition for forming a water-repellent layer is not particularly limited, but is, for example, in the range of 20 to 80% by mass, particularly in the range of 40 to 60% by mass in terms of solid content. It is preferable that

  Next, the shape retention material contained in the composition for forming a water repellent layer will be described. The shape retaining material is used to retain the shape of the water repellent layer when the water repellent material is softened in the thermocompression bonding step. The raw material of the holding material is not particularly limited as long as it can hold the shape of the water-repellent layer, and examples thereof include carbon, metal, and resin. Moreover, as a shape of the said shape maintenance material, fibrous form, a cylindrical shape, etc. can be mentioned, for example. Further, since the shape retaining material is used for retaining the shape of the water repellent layer, it may have conductivity or may not have conductivity. In an embodiment, it is preferable that the shape-retaining material has conductivity. This is because the conductivity of the water repellent layer can be improved.

  Specific examples of such a shape-retaining material include fibrous carbon, fibrous metal, tubular carbon, tubular metal, etc. Among them, fibrous carbon is preferable. Specific examples of the fibrous carbon include vapor grown carbon fiber (VGCF), rayon-based carbon fiber, polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, and the like. Among them, VGCF is preferable. .

  The VGCF is produced by gas phase pyrolysis of a gas such as a hydrocarbon in the presence of a metal catalyst. In this embodiment, the fiber diameter of the VGCF is not particularly limited, but is preferably, for example, 500 nm or less, and more preferably in the range of 1 to 300 nm. The fiber length of the VGCF is not particularly limited, but is preferably 100 μm or less, particularly 80 μm or less, and particularly preferably 50 μm or less. When the VGCF has a branched structure, the fiber length means the length from the branch point to the tip or other branch point. Moreover, it is preferable that the said VGCF is what improved the crystallinity by heating at the temperature of 2500 degreeC or more, for example. This is because the conductivity is improved by improving the crystallinity.

  On the other hand, examples of the fibrous metal include metal whiskers, examples of the cylindrical carbon include carbon nanotubes, and examples of the cylindrical metal include metal nanotubes.

  The content of the shape-retaining material in the composition for forming a water repellent layer is not particularly limited, but is, for example, in the range of 5 to 50% by mass, particularly in the range of 10 to 30% by mass in terms of solid content. It is preferable that

  Next, the conductive material contained in the water repellent layer forming composition will be described. The conductive material imparts conductivity to the water repellent layer. The conductive material is not particularly limited as long as it has conductivity, and examples thereof include conductive particles such as carbon black. Specific examples of the carbon black include oil furnace black, acetylene black, thermal black, and channel black. Of these, oil furnace black and acetylene black are preferred in this embodiment. It is because it is excellent in the effect which provides electroconductivity. The primary particle size of the conductive particles is not particularly limited, but is preferably 1 μm or less.

  Moreover, in this embodiment, when the shape retention material mentioned above has electroconductivity, the shape retention material can be used as an electroconductive material. In this case, the shape maintaining material and the conductive material are the same material. Since such a material is as described above, a description thereof is omitted here.

  The content of the conductive material in the composition for forming a water repellent layer is not particularly limited, but is, for example, in the range of 20 to 80% by mass, particularly in the range of 40 to 60% by mass in terms of solid content. It is preferable that If the content of the conductive material is too small, sufficient conductivity may not be imparted, and if the content of the conductive material is too large, the water repellency of the water repellent layer may be reduced. Because.

  Moreover, the said composition for water-repellent layer formation may have a solvent. Such a solvent is not particularly limited, and examples thereof include n-propanol, n-butanol, and n-pentanol.

  On the other hand, the gas diffusion layer used in the present embodiment is not particularly limited as long as it has sufficient heat resistance to the heating temperature when forming the water-repellent layer. Can be used. Specific examples include a carbon fiber gas diffusion layer.

In this step, the water repellent layer forming composition is formed on the gas diffusion layer by applying the water repellent layer forming composition to the gas diffusion layer and performing a heat treatment. The heating temperature at the time of the heat treatment is not particularly limited, but is usually about 350 ° C. Further, the weight of the water-repellent layer thus obtained is not particularly limited, but specifically, it is in the range of ^{2 to} 80 mg / cm ² , particularly in the range of 5 to 40 mg / cm ² . In particular, it is preferably in the range of 10 to ²⁰ mg / cm ² .

2. Next, the catalyst electrode layer forming step in this embodiment will be described. The catalyst electrode layer forming step is a step of forming a catalyst electrode layer containing an electrolyte material having a glass transition temperature higher than the softening temperature of the water repellent material on at least one of the water repellent layer and the solid polymer electrolyte membrane. .

  FIG. 3 is a schematic cross-sectional view illustrating the catalyst electrode layer obtained by this step. The catalyst electrode layer 3 obtained by this step may be formed on the water-repellent layer 1 as shown in FIG. 3 (a). As shown in FIG. 3 (b), the solid polymer layer 3 may be formed. It may be formed on the electrolyte membrane 4 or may be formed on the water repellent layer 1 and the solid polymer electrolyte membrane 4 as shown in FIG. Moreover, the catalyst electrode layer obtained by this process has an electrolyte material, a catalyst, and the electroconductive material for catalyst electrode layers at least. Hereinafter, the electrolyte material, the catalyst and the conductive material constituting the catalyst electrode layer, and the solid polymer electrolyte membrane used in this embodiment will be described.

First, the electrolyte material used for the catalyst electrode layer will be described. The electrolyte material is responsible for proton conduction in the catalyst electrode layer. Moreover, in this embodiment, the said electrolyte material has a glass transition temperature higher than the softening temperature of the water-repellent material mentioned above.
The glass transition temperature of the electrolyte material is higher than the softening temperature of the water repellent material. The difference between the glass transition temperature of the electrolyte material and the softening temperature of the water-repellent material is, for example, preferably in the range of 5 to 70 ° C, and more preferably in the range of 15 to 30 ° C. Further, the glass transition temperature of the electrolyte material is not particularly limited as long as it is higher than the softening temperature of the water-repellent material. It is preferable to be within the range, particularly within the range of 135 to 170 ° C.

Such an electrolyte material is not particularly limited as long as it has proton conductivity, and examples thereof include hydrocarbon-based electrolyte materials and perfluorocarbon sulfonic acid-based electrolyte materials. Hydrocarbon electrolyte materials are preferred. Since the hydrocarbon-based electrolyte material has a high glass transition temperature and needs to be thermocompression bonded at a high temperature, there is a high possibility that the above-described pressure loss will occur, and the shape-retaining material used in this embodiment exhibits its effect sufficiently. Because it can.
Although it does not specifically limit as said hydrocarbon type electrolyte material, For example, what introduce | transduced the proton conductive group into the hydrocarbon type raw material etc. can be mentioned. Examples of the hydrocarbon raw material include polyether sulfone resin (PES), polyether sulfone resin (PES), polyether ether ketone resin (PEEK), polyphenylene sulfide resin (PPS), and polyphenylene oxide resin (PPO). And polybenzimidazole resin (PBI). Examples of the proton conductive group include a sulfonic acid group, a carboxyl group, a phosphite group, a phosphonic acid group, and a hydroxyl group, and among them, a sulfonic acid group is preferable. This is because the proton conductivity is excellent.

  Moreover, the method for introducing a proton conductive group into the hydrocarbon-based material is not particularly limited as long as it is a method capable of obtaining a desired hydrocarbon-based electrolyte material. For example, when introducing a sulfonic acid group into PES, PES is dissolved in a predetermined solvent, and a solution containing a sulfonic acid group-containing compound such as Trimetylsilylchlorosulfonate is added dropwise to the solution to cause a reaction. The method of obtaining the precipitation of a product by adding a poor solvent etc. can be mentioned. The product can be identified by NMR and IR.

  On the other hand, examples of the perfluorocarbon sulfonic acid-based solid polymer electrolyte membrane include Nafion (trade name, manufactured by DuPont), Flemion (trade name, manufactured by Asahi Glass Co., Ltd.), Aciplex (trade name, manufactured by Asahi Kasei Co., Ltd.), and the like. Can be mentioned.

  Moreover, it does not specifically limit as a conductive material and a catalyst used for a catalyst electrode layer, The thing similar to the material used for a general fuel cell can be used. For example, examples of the conductive material include carbon black, and examples of the catalyst include Pt.

  Next, the solid polymer electrolyte membrane used in this embodiment will be described. The solid polymer electrolyte membrane is sandwiched between the catalyst electrode layers and is responsible for proton conduction between the two catalyst electrode layers. The glass transition temperature of the solid polymer electrolyte membrane is not particularly limited as long as a fuel cell having good adhesion can be obtained, but is equal to or lower than the glass transition temperature of the electrolyte material. Is preferred.

  The solid polymer electrolyte membrane is not particularly limited as long as it has proton conductivity. For example, hydrocarbon solid polymer electrolyte membrane, perfluorocarbon sulfonic acid solid polymer electrolyte membrane Among them, a hydrocarbon-based solid polymer electrolyte membrane is preferable. Since the hydrocarbon-based solid polymer electrolyte membrane has a high glass transition temperature and needs to be thermocompression bonded at a high temperature, there is a high possibility that the above-described pressure release occurs, and the shape-retaining material used in this embodiment has a sufficient effect. It is because it can be demonstrated to. Since the hydrocarbon-based solid polymer electrolyte membrane and the perfluorocarbon sulfonic acid-based solid polymer electrolyte membrane can be the same as the hydrocarbon-based solid electrolyte material and the perfluorocarbon sulfonic acid-based electrolyte material, The description here is omitted. Further, the solid polymer electrolyte membrane may be the same material as the electrolyte material, or may be a material different from the electrolyte material. In this embodiment, the solid polymer electrolyte membrane is The material is preferably the same as the electrolyte material. That is, in the present embodiment, the solid polymer electrolyte membrane and the electrolyte material are preferably hydrocarbon materials, and the solid polymer electrolyte membrane and the electrolyte material are the same hydrocarbon material. More preferred.

  The method for forming the catalyst electrode layer on the gas diffusion layer or the solid polymer electrolyte membrane is not particularly limited, and a general method can be used. Specific examples include a method of applying a catalyst electrode layer-forming composition containing a material constituting the catalyst electrode layer on a gas diffusion layer or a solid polymer electrolyte membrane and drying the composition.

3. Next, the thermocompression bonding process in this embodiment will be described. The thermocompression bonding process in this embodiment is a process in which the gas diffusion layer and the solid polymer electrolyte membrane are thermocompression bonded so as to sandwich the water repellent layer and the catalyst electrode layer.
In this step, for example, as shown in FIG. 1 (c), the catalyst electrode layer 3, the water repellent layer 2 and the gas diffusion layer 1 are placed on one side of the solid polymer electrolyte membrane 4 to perform thermocompression bonding. For example, as shown in FIG. 1 (d), a laminate 5 may be installed on both surfaces of the solid polymer electrolyte membrane 4 to perform thermocompression bonding. Especially, in this embodiment, it is preferable to install a laminated body on both surfaces of a solid polymer electrolyte membrane, and to perform thermocompression bonding. This is because a membrane electrode assembly can be obtained in a single step.

  Further, the heating temperature in this step is not particularly limited as long as it is a temperature at which a fuel cell excellent in adhesion can be obtained. Specifically, it is performed near the glass transition temperature of the electrolyte material. Further, when the glass transition temperature of the solid polymer electrolyte membrane is equal to or higher than the glass transition temperature of the electrolyte material, the heating temperature may be set near the glass transition temperature of the solid polymer electrolyte membrane.

  For example, when PTFE is used as the water repellent material and a hydrocarbon-based electrolyte material is used as the electrolyte material included in the catalyst electrode layer, the heating temperature in the thermocompression bonding process is particularly limited as long as a fuel cell with good adhesion can be obtained. Although not specifically, it is specifically preferable to be within the range of 110 to 200 ° C, more preferably within the range of 120 to 180 ° C, and particularly within the range of 130 to 160 ° C.

  In addition, the pressurizing pressure in this step varies depending on the type of the solid polymer electrolyte membrane and the like, the heating temperature, etc., and specifically in the range of 1 to 20 MPa, particularly in the range of 2 to 15 MPa, In particular, it is preferably within a range of 3 to 10 MPa.

  In this step, the method for performing thermocompression bonding is not particularly limited, and a commercially available thermocompression bonding machine can be used.

B. Second Embodiment Next, a second embodiment of the method for producing a solid polymer electrolyte fuel cell of the present invention will be described. This embodiment is an embodiment in which the glass transition temperature of the solid polymer electrolyte membrane is higher than the softening temperature of the water repellent material contained in the water repellent layer.

  That is, in the method for producing a solid polymer electrolyte fuel cell according to this embodiment, a water repellent layer-forming composition containing a water repellent material, a conductive material and a shape-retaining material is applied to a gas diffusion layer, Forming a catalyst electrode layer on at least one of the water-repellent layer forming step, the water-repellent layer, and a solid polymer electrolyte membrane having a glass transition temperature higher than the softening temperature of the water-repellent material And a thermocompression bonding step of thermocompression bonding the solid polymer electrolyte membrane and the gas diffusion layer so as to sandwich the water-repellent layer and the catalyst electrode layer.

  According to this embodiment, even when the water-repellent material is softened by thermocompression bonding at a high temperature, the presence of the shape-retaining material can suppress the pressure loss, and the catalyst electrode layer and the solid polymer Adhesion failure at the interface with the electrolyte membrane can be suppressed. For example, when the solid polymer electrolyte membrane has a high glass transition temperature, it is necessary to thermocompress each constituent member at a high temperature when forming the membrane electrode assembly. At this time, when thermocompression bonding is performed at a high temperature, the water-repellent layer is softened and the water-repellent layer is released. As a result, the pressing force through the gas diffusion layer is not sufficiently transmitted to the catalyst electrode layer, and adhesion failure may occur at the interface between the catalyst electrode layer and the solid polymer electrolyte membrane. On the other hand, in this embodiment, even when thermocompression bonding is performed at a heating temperature at which the water repellent material is softened, the water repellent layer is softened as a whole by including a shape-retaining material in the water repellent layer. It is possible to suppress the occurrence of pressure loss.

  Next, the manufacturing method of the solid polymer electrolyte fuel cell of this embodiment is demonstrated using drawing. The manufacturing method of this embodiment (second embodiment) is in principle the same as the manufacturing method of the first embodiment shown in FIG. However, in this embodiment, the glass transition temperature of the solid polymer electrolyte membrane 4 is higher than the softening temperature of the water repellent material contained in the water repellent layer 2.

  The fuel cell manufacturing method of this embodiment includes a water repellent layer forming step, a catalyst electrode layer forming step, and a thermocompression bonding step. Each step will be described in detail below.

1. Water-repellent layer forming step The water-repellent layer-forming step in this embodiment is performed by applying a water-repellent layer-forming composition containing a water-repellent material, a conductive material, and a shape-retaining material to a gas diffusion layer to form a water-repellent layer. It is a process to do. The water-repellent layer forming step in this embodiment is the same as the water-repellent layer forming step described in the above “A. First embodiment”, and thus the description thereof is omitted here.

2. Catalyst electrode layer forming step The catalyst electrode layer forming step in the present embodiment is the step of forming the catalyst electrode layer on at least one of the water repellent layer and the solid polymer electrolyte membrane having a glass transition temperature higher than the softening temperature of the water repellent material. It is a process to do. In this embodiment, as in the first embodiment described above, the catalyst electrode layer may be formed on the water repellent layer, or the catalyst electrode layer may be formed on the solid polymer electrolyte membrane. The catalyst electrode layer may be formed on the surfaces of both the water repellent layer and the solid polymer electrolyte membrane (see FIG. 3 described above).

The solid polymer electrolyte membrane used in this embodiment is sandwiched between the catalyst electrode layers and is responsible for proton conduction between the two catalyst electrode layers. In this embodiment, the solid polymer electrolyte membrane has a glass transition temperature higher than the softening temperature of the water repellent material described above.
The glass transition temperature of the solid polymer electrolyte membrane is higher than the softening temperature of the water repellent material. The difference between the glass transition temperature of the solid polymer electrolyte membrane and the softening temperature of the water repellent material is, for example, preferably in the range of 5 to 70 ° C., more preferably in the range of 15 to 30 ° C. Further, the glass transition temperature of the solid polymer electrolyte membrane is not particularly limited as long as it is higher than the softening temperature of the water repellent material. It is preferable to be in the range of 200 ° C, particularly in the range of 135 to 170 ° C.

  Such a solid polymer electrolyte membrane is not particularly limited as long as it has proton conductivity, and examples thereof include hydrocarbon-based solid polymer electrolyte membranes and perfluorocarbon sulfonic acid-based solid polymer electrolyte membranes. Among them, a hydrocarbon-based solid polymer electrolyte membrane is preferable. Since the hydrocarbon-based solid polymer electrolyte membrane has a high glass transition temperature and needs to be thermocompression bonded at a high temperature, there is a high possibility that the above-described pressure release occurs, and the shape-retaining material used in this embodiment has a sufficient effect. It is because it can be demonstrated to. The material of the solid polymer electrolyte membrane is the same as that described in the above “A. First embodiment”, and the description thereof is omitted here.

  Next, the catalyst electrode layer used in this embodiment will be described. The catalyst electrode layer used in the present embodiment usually contains an electrolyte material, a conductive material, and a catalyst. In this embodiment, the electrolyte material is responsible for proton conduction in the catalyst electrode layer. The glass transition temperature of the electrolyte material is not particularly limited as long as a fuel cell having good adhesion can be obtained, but it is equal to or lower than the glass transition temperature of the solid polymer electrolyte membrane. Is preferred.

  The electrolyte material is not particularly limited as long as it has proton conductivity, and examples thereof include hydrocarbon electrolyte materials and perfluorocarbon sulfonic acid electrolyte materials. From the viewpoint of versatility, perfluorocarbon sulfonic acid electrolyte materials are preferred. On the other hand, a hydrocarbon-based electrolyte material is preferable from the viewpoint that the glass transition temperature is high and the effects of the present invention can be sufficiently exhibited. The material of the electrolyte material is the same as that described in the above “A. First embodiment”, and thus the description thereof is omitted here. Further, the electrolyte material may be the same material as the solid electrolyte, or may be a material different from the solid electrolyte. In this embodiment, the electrolyte material is the solid polymer electrolyte membrane. The same material is preferable. That is, in the present embodiment, the electrolyte material and the solid polymer electrolyte membrane are preferably hydrocarbon materials, and the solid polymer electrolyte membrane and the electrolyte materials are the same hydrocarbon material. More preferred.

  The conductive material and the catalyst used for the catalyst electrode layer are not particularly limited, and the same materials as those used for general fuel cells can be used. For example, examples of the conductive material include carbon black, and examples of the catalyst include Pt.

  Further, the method for forming the catalyst electrode layer on the gas diffusion layer or the solid polymer electrolyte membrane, and other matters are the same as the contents described in the above “A. First embodiment”. Description of is omitted.

3. Thermocompression bonding step The thermocompression bonding step in the present embodiment is a step of thermocompression bonding the gas diffusion layer and the solid polymer electrolyte membrane so as to sandwich the water repellent layer and the catalyst electrode layer. The thermocompression bonding process in the present embodiment is the same as the contents described in the thermocompression bonding process described in the above “A. First embodiment”, and thus the description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example]
(Production of water repellent layer)
4 g of PTFE powder (Daikin Kogyo Co., Ltd., softening temperature 121 ° C.) as a water repellent material, 5 g of carbon fine powder as a conductive material, and 4 g of vapor-grown carbon fiber (VGCF, Showa Denko) as a shape-retaining material are mixed. An aqueous layer forming composition was obtained. This water repellent layer forming composition was applied to a carbon fiber gas diffusion layer (TGP060, manufactured by Toray Industries, Inc.) and baked at 350 ° C. to obtain a water repellent layer.
(Preparation of catalyst electrode layer)
1 g of platinum-supported carbon powder, 5 g of water, 6 g of ethanol, and 1.5 g of Nafion (trade name, manufactured by DuPont) 20% solution were mixed to obtain a composition for forming a catalyst electrode layer. This catalyst electrode layer forming composition was spray-coated on the water repellent layer and dried to obtain a catalyst electrode layer on the water repellent layer. Thereby, the laminated body by which the diffusion layer, the water repellent layer, and the catalyst electrode layer were laminated | stacked in this order was obtained.

(Production of membrane electrode composite)
Prepare a solid polymer electrolyte membrane (SF702x, manufactured by Asahi Kasei Co., Ltd.) with a glass transition temperature of 140 ° C., and use two of the above laminates so that both sides of the solid polymer electrolyte membrane are in contact with the catalyst electrode layers of the laminate The membrane electrode assembly was obtained by performing thermocompression bonding for 4 minutes under the conditions of 150 ° C. and 8 MPa.

[Comparative example]
A membrane electrode assembly was obtained in the same manner as in Example except that no vapor-grown carbon fiber was used for the water repellent layer.

[Evaluation]
Using the membrane electrode assemblies obtained in Examples and Comparative Examples, a power generation test was performed under the conditions of a cell temperature of 80 ° C., a stoichiometric ratio of 2/2, an anode gas humidification dew point of 45 ° C. and a cathode gas humidification dew point of 55 ° C. The obtained current-voltage curve is shown in FIG. As is clear from FIG. 4, the membrane electrode assembly obtained in the example had superior power generation efficiency as compared with the membrane electrode assembly obtained in the comparative example.
In addition, the gas diffusion layer was mechanically peeled from the membrane electrode composites obtained in the examples and comparative examples, and the surface of the electrolyte membrane with a catalyst electrode layer (water-repellent layer) after peeling was observed. The adhesion between the membrane and the catalyst electrode layer was evaluated. As shown in FIG. 5 (a), a uniform water-repellent layer (black part) and a remaining gas diffusion layer base material (white linear part) were confirmed on the surface of the electrolyte membrane with catalyst electrode layer of the example. It was done. On the other hand, on the surface of the electrolyte membrane with a catalyst electrode layer of the comparative example, as shown in FIG. Spots) were confirmed. From this, it became clear that the Example showed the outstanding electrolyte membrane-catalyst electrode layer bondability compared with the comparative example.

It is process drawing which shows an example of the manufacturing method of the fuel cell of this invention. It is a schematic sectional drawing which shows an example of the water repellent layer obtained by a water repellent layer formation process. It is a schematic sectional drawing which illustrates the catalyst electrode layer obtained by a catalyst electrode layer formation process. It is a graph which shows the current-voltage curve in a power generation test. It is an image which shows the surface (water-repellent layer) of the electrolyte membrane with a catalyst electrode layer after gas diffusion layer peeling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas diffusion layer 2 ... Water repellent layer 3 ... Catalyst electrode layer 4 ... Solid polymer electrolyte membrane 5 ... Laminated body 6 ... Water repellent material 7 ... Conductive material 8 ... Shape maintenance material

Claims (3)

A water repellent material, a conductive material and a shape-retaining material are mixed to prepare a water repellent layer forming composition, and the water repellent layer forming composition is applied to the gas diffusion layer to form a water repellent layer. A water repellent layer forming step;
A catalyst electrode layer forming step of forming a catalyst electrode layer on at least one of the water repellent layer and a solid polymer electrolyte membrane having a glass transition temperature higher than the softening temperature of the water repellent material;
A thermocompression bonding step of thermocompression bonding the solid polymer electrolyte membrane and the gas diffusion layer so as to sandwich the water repellent layer and the catalyst electrode layer;
I have a,
A method for producing a solid polymer electrolyte fuel cell, wherein the solid polymer electrolyte membrane has a glass transition temperature of 135 ° C. or higher .   2. The method for producing a solid polymer electrolyte fuel cell according to claim 1, wherein the solid polymer electrolyte membrane is a hydrocarbon-based solid polymer electrolyte membrane.   3. The method for producing a solid polymer electrolyte fuel cell according to claim 1, wherein the water repellent material is polytetrafluoroethylene.

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