JP2022066787A - Sub-gasket, fuel cell, and manufacturing method thereof - Google Patents

Abstract

To improve the adhesiveness of a sub-gasket.SOLUTION: In a sub-gasket (5) for a fuel cell which is a resin film containing amorphous resin, the sub-gasket (5) can be attached to an electrolyte membrane (1) by superimposing the sub-gasket (5) on a part of the electrolyte membrane (1) and heating and pressurizing the sub-gasket.SELECTED DRAWING: Figure 2

Description

The present invention relates to a sub-gasket, a fuel cell and a method for manufacturing the same.

The fuel cell has a structure in which a membrane electrode assembly that generates electricity by a chemical reaction of fuel gas is sandwiched between a pair of separators. A sub-gasket is attached to the membrane electrode assembly as a support (see, for example, Patent Document 1).

The sub-gasket is generally a frame-shaped resin film. Such a sub-gasket is manufactured by forming a film of a thermoplastic resin and then cutting it into a predetermined shape.

Japanese Unexamined Patent Publication No. 2007-180031

The sub-gasket is placed at a high temperature during power generation and comes into contact with a fuel gas such as hydrogen gas. Therefore, as the resin material for the sub-gasket, a highly functional resin having excellent strength, heat resistance, chemical resistance, etc., such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), so-called engineering plastic, is used.

Generally, engineering plastics have a relatively high crystallinity, but when used as a sub-gasket, they are stretched after film molding in order to increase the crystallinity. Such a film has low adhesiveness to each other or to other members such as a separator, and cannot be adhered to other members without an adhesive. Therefore, when assembling a fuel cell, an adhesive is applied to the film surface. A process was needed.

An object of the present invention is to improve the adhesiveness of a sub-gasket.

The gasket according to the present invention is a resin film containing an amorphous resin. According to such a configuration, the adhesiveness of the sub-gasket (5) can be enhanced.

The fuel cell according to the present invention includes an electrolyte membrane (1) and a sub-gasket (5) attached to the electrolyte membrane (1), and the sub-gasket (5) is a resin film containing an amorphous resin. It is a composition. According to such a configuration, the adhesiveness of the fuel cell (10) to the adjacent member of the sub-gasket (5) can be enhanced. In addition, the manufacturing process of the fuel cell (10) can be simplified.

The method for manufacturing a fuel cell according to the present invention is a method for manufacturing a fuel cell (10) including an electrolyte film (1) and a sub-gastaker (5) attached to the electrolyte film (1), and is a method for manufacturing a sub-gastaker (5). ) Is a resin film containing an amorphous resin, wherein the step of forming the resin film using the resin composition containing the amorphous resin and the resin film are overlapped with a part of the electrolyte film (1). It is a configuration including a step of obtaining an electrolyte film (1) to which a sub gasket (5) is attached by heating and pressurizing. According to such a configuration, the adhesiveness of the fuel cell (10) to the adjacent member of the sub-gasket (5) can be enhanced. In addition, the manufacturing process of the fuel cell (10) can be simplified.

The present invention may have only the invention-specific matters described in the claims of the present invention, and has a configuration other than the invention-specific matters together with the invention-specific matters described in the claims of the present invention. It may be a thing.

It is sectional drawing which shows the structure of the fuel cell of this embodiment. It is an enlarged sectional view which shows the sub-gasket. It is an enlarged sectional view which shows the example of the sub-gasket of a three-layer structure. It is an enlarged sectional view which shows the example of the sub-gasket which has a different thickness.

Hereinafter, embodiments of the sub-gasket, the fuel cell, and the method for manufacturing the same of the present invention will be described with reference to the drawings. The configuration described below is an example (representative) of the present invention, and the present invention is not limited to this configuration.

(Fuel cell)
FIG. 1 shows the configuration of a fuel cell 10 which is a polymer electrolyte fuel cell (PEFC).

The fuel cell 10 includes a membrane electrode assembly (MEA) 3, a sub-gasket 5, and a pair of separators 4. One unit in which MEA3 is sandwiched by this pair of separators 4 is called a cell. The fuel cell 10 may be a stack of a plurality of cells. The MEA 3 includes an electrolyte membrane 1 and a pair of electrodes 2 on both sides of the electrolyte membrane 1.

The electrolyte membrane 1 is an ion-conducting polymer electrolyte membrane. Examples of the polymer electrolyte that can be used for the electrolyte membrane 1 include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Aquivion (registered trademark); aromatic systems such as sulfonated polyether ether ketone (SPEEK) and sulfonated polyimide. Polymers; Examples thereof include aliphatic polymers such as polyvinyl sulfonic acid and polyvinyl phosphoric acid.

Of the pair of electrodes 2, one of the electrodes 2 is an anode and is also called a fuel electrode. The other electrode 2 is a cathode and is also called an air electrode. As fuel gas, hydrogen gas is supplied to the anode and air containing oxygen gas is supplied to the cathode.

At the anode, a reaction occurs that produces electrons (e ⁻ ) and protons (H ⁺ ) from hydrogen gas (H ₂ ). The electrons move to the cathode via an external circuit (not shown). This movement of electrons causes an electric current to be generated in the external circuit. Protons move to the cathode via the electrolyte membrane 1.

At the cathode, oxygen ions (O _2- ⁾ are generated from oxygen gas (O ₂ ) by electrons transferred from an external circuit. Oxygen ions combine with protons (2H ⁺ ) that have moved from the electrolyte membrane 1 to become water ( _H2O ).

The electrode 2 includes a catalyst layer 21. The electrode 2 of the present embodiment includes a gas diffusion layer 22 and a microporous layer 23 in order to improve the diffusivity of the fuel gas. The gas diffusion layer 22 and the microporous layer 23 are arranged on the separator 4 side of the catalyst layer 21 in this order.

The catalyst layer 21 promotes the reaction of hydrogen gas and oxygen gas by the catalyst. The catalyst layer 21 includes a catalyst, a carrier that supports the catalyst, and ionomers that coat them. Examples of the catalyst include metals such as platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh), palladium (Pd), tungsten (W), mixtures of these metals, alloys and the like. Among them, platinum, a mixture containing platinum, an alloy, or the like is preferable from the viewpoints of catalytic activity, toxicity to carbon monoxide, heat resistance, and the like.

Examples of the carrier include mesoporous carbon or a conductive porous metal compound having pores such as Pt black. Mesoporous carbon is preferable from the viewpoint of good dispersibility, large surface area, and small particle growth at high temperature even when the amount of catalyst supported is large. As the ionomer, a polymer electrolyte having the same ion conductivity as that of the electrolyte membrane 1 can be used.

The gas diffusion layer 22 may be provided for the purpose of uniformly diffusing the fuel gas supplied to the fuel cell 10 over the entire surface of the catalyst layer 21. The gas diffusion layer 22 can be formed by arranging a gas diffusion layer sheet as the outermost layer of the MEA3. Examples of the gas diffusion layer sheet include porous fiber sheets such as carbon fibers having conductivity, gas permeability and gas diffusion, and metal sheet materials such as foamed metal and expanded metal.

The microporous layer 23 may be provided for the purpose of improving the drainage property of water generated during power generation and reducing the electric resistance of the gas diffusion layer 22. The microporous layer 23 can be formed by coating an ink containing a conductive material such as carbon particles on the gas diffusion layer 22 and drying it. The ink may optionally contain a reinforcing material such as carbon fiber or a binder.

The separator 4 is also called a bipolar plate. The separator 4 has an uneven structure. This uneven structure can be formed by press-molding a metal substrate such as titanium, a titanium alloy, or stainless steel. The uneven structure can also be formed by molding a composition containing carbon.

The recess 4a of the separator 4 forms a fluid flow path between the separator 4 and the MEA3. The flow path is not only a supply path for fuel gas, but also a discharge path for water generated by a chemical reaction during power generation. When cooling water is used to cool the fuel cell 10, the flow path is also used as a cooling water passage.

(Sub-gasket)
The sub-gasket 5 of the present embodiment is a frame body having an opening in the center. The sub-gasket 5 is attached to the electrolyte membrane 1 and functions as a support. Further, the sub-gasket 5 abuts on the separator 4 to seal the inside of the fuel cell 10.

The sub-gasket 5 is a resin film containing an amorphous resin. The sub-gasket 5 may be a resin film made of an amorphous resin, or may be a mixed resin film in which a crystalline resin is used in combination with the amorphous resin. The resin film may contain an additive if necessary.

As used herein, the amorphous resin refers to a thermoplastic resin having no melting point (Tm) but having a glass transition temperature (Tg) in differential scanning calorimetry (DSC). Further, the crystalline resin refers to a thermoplastic resin having a melting point in DSC.

Even after the crystalline resin reaches the glass transition temperature (Tg) by heating, it does not soften significantly until it exceeds the melting point (Tm), but the amorphous resin contained in the sub-buffer 5 reaches the glass transition temperature (Tg). When it reaches it, it softens rapidly. Therefore, when the sub-gasket 5 is heated to a temperature equal to or higher than the glass transition temperature (Tg) of the amorphous resin, the viscosity increases due to the softening of the amorphous resin in the sub-gasket 5, and the sub-gaskets 5 are adjacent to each other or adjacent to the sub-gasket 5. It is possible to improve the adhesiveness with the surface of members such as the electrolyte film 1 and the separator 4. This is because the softened amorphous resin component enters the uneven surface and hardens by cooling. Therefore, the adhesiveness of the sub-gasket 5 to the adjacent member can be enhanced, and by heating the sub-gasket 5, the sub-gasket 5 can be adhered to the adjacent member without using an adhesive.

FIG. 2 is an enlarged cross-sectional view of the sub-gasket 5 before arranging the separator 4. The sub-gasket 5 is arranged around the electrolyte membrane 1, and the peripheral edge of the central opening of the sub-gasket 5 and the end of the electrolyte membrane 1 are overlapped with each other. The area of the electrolyte membrane 1 is larger than the active area in which the catalyst layer 21 is laminated, and the electrolyte membrane 1 protrudes from the active area. Two sub-gaskets 5 are arranged on both sides of the electrolyte membrane 1 so as to sandwich the end of the protruding electrolyte membrane 1.

When the sub-gasket 5 is pressurized in the direction Y1 from the separator 4 toward the electrolyte membrane 1, the surface 5a of the sub-gasket 5 that does not overlap with the electrolyte membrane 1 moves in the direction Y2, and the surface 5a of the sub-gasket 5 faces the other sub-gasket 5. It comes into contact with the surface 5a. When the sub-gasket 5 is heated in this state, the amorphous resin in the sub-gasket 5 softens, and the surfaces 5a of the sub-gasket 5 in contact with each other adhere to each other. Further, the surface 5b of the sub-gasket 5 that overlaps with the electrolyte membrane 1 also adheres to the electrolyte membrane 1 by softening the amorphous resin. As described above, since the adhesive is adhered without the adhesive, the process of applying the adhesive can be omitted, and the manufacturing process of the fuel cell 10 can be simplified.

Examples of the amorphous resin include polycarbonate (PC), polyether sulfone (PES), polyphenyl ether (PPE or PPO), polyamide-imide (PAI), polystyrene (PS), polymethyl methacrylate (PMMA), and acrylonitrile. Examples thereof include a butadiene / styrene copolymer (ABS). The amorphous resin is not limited to these homopolymers, and copolymers of monomers of each homopolymer can also be used. In addition, one of these can be used alone or in combination of two or more.

From the viewpoint of heat resistance, the amorphous resin is a polycarbonate (Tg: about 150 ° C.) having a glass transition temperature (Tg) of 100 ° C. or higher, an acrylonitrile-butadiene-styrene copolymer (Tg: about 110 ° C.), and the like. Alternatively, polymethyl methacrylate (Tg: about 100 ° C.) is preferable, and polycarbonate or an acrylonitrile-butadiene-styrene copolymer having a glass transition temperature (Tg) of 110 ° C. or higher is preferable. The operating temperature of the fuel cell 10 is usually about room temperature to 100 ° C., and if the glass transition temperature (Tg) of the amorphous resin is 100 ° C. or higher as described above, the sub-gasket 5 has sufficient heat resistance. Is easy to obtain.

Examples of the crystalline resin that can be used in combination with the amorphous resin include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetheretherketone (PEEK), and polyphenylsulfide (PPS). ), Liquid crystal polymer (LCP) and the like. One of these can be used alone or in combination of two or more.

The content of the amorphous resin in the resin film is at least 10% by mass or more. The higher the content, the better the adhesiveness. Therefore, from the viewpoint of improving the adhesiveness, the content is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more.

As exemplified, many crystalline resins are high-performance engineering plastics such as PEN and PEEK, while many amorphous resins are general-purpose resins. From the viewpoint of not only adhesiveness but also cost reduction, the content of the amorphous resin in the resin film is particularly preferably 100% by mass. When the sub-gasket 5 is manufactured, the unnecessary film discharged by cutting the resin film may be reused, but the resin film made of 100% by mass amorphous resin is easy to reuse.

The content ratio of the amorphous resin is preferably higher on the surface side than on the inner side in the thickness direction of the resin film. The higher the proportion of the amorphous resin on the surface of the resin film, which is the adhesive surface with the adjacent member, the higher the adhesiveness with the adjacent member.

For example, a resin composition which is a mixture of a plurality of types of resins including an amorphous resin is melt-extruded to form a resin film having a single-layer structure, which is then heated to soften the amorphous resin on the surface side. By migrating, the content of the amorphous resin on the surface side can be increased. This transition can be performed by hot pressing when attaching the sub-gasket 5 to the electrolyte membrane 1. The heating time during hot pressing is usually several seconds to several minutes, but it may take longer than usual for migration.

The resin film as the sub-gasket 5 may have a multilayer structure. In this case, it is preferable that the content ratio of the amorphous resin in the layer on the surface side is larger than that on the inner side in the thickness direction of the film. Such a resin film can be formed by, for example, a coextrusion method such as a feed block method or a multi-manifold method, or an extrusion laminating method in which each layer is melt-extruded and laminated in order.

FIG. 3 shows an example of a sub-gasket 5A having a three-layer structure. In the sub-cascade 5A, a resin film made of an amorphous resin can be used as the outermost layer 51 in contact with the electrolyte membrane 1 or the separator 4, and a resin film made of a crystalline resin can be used as the inner layer 52. Since the outermost layer 51 is softened and the adhesiveness is enhanced by heating and pressurizing such a sub-gasket 5A, the sub-gasket 5A can be combined with the electrolyte membrane 1, the separator 4, or another facing sub-gasket 5A without using an adhesive. Can be glued.

When a resin film containing an amorphous resin is used for the outermost layer 51 in the multilayer structure, a resin film made of a thermosetting resin can be used as the inner layer 52. Examples of the thermosetting resin include polyimide (PI), melamine resin, phenol resin and the like.

The glass transition temperature (Tg) of the amorphous resin is preferably higher than the temperature set as the temperature at the time of power generation of the fuel cell 10, more preferably 10 ° C or higher than the set temperature, and more preferably 20 ° C or higher. Higher is more preferred. The amorphous resin having such a glass transition temperature (Tg) is difficult to soften even at a high temperature during power generation, and film deformation due to softening can be suppressed.

For example, when the temperature of the fuel cell 10 at the time of power generation is set to 90 to 130 ° C., polycarbonate having a glass transition temperature (Tg) of 150 ° C. can be used as the amorphous resin. When the temperature at the time of power generation is set to 90 to 150 ° C., a polyether sulfone (PSU) having a glass transition temperature (Tg) of 230 ° C. can be used as the amorphous resin.

When the sub-cascade 5 also contains a crystalline resin, the glass transition temperature (Tg) of the amorphous resin is preferably lower than the melting point of the crystalline resin used in combination. The amorphous resin having such a glass transition temperature (Tg) is easy to soften under the melting temperature of the crystalline resin and is easy to form a film. Further, when the sub-gasket 5 is heated and bonded to an adjacent member, it can be bonded with a small amount of heat energy. Since the crystalline resin is not melted during bonding, it is possible to suppress film deformation and the like.

For example, when polyethylene naphthalate having a melting point of 265 ° C. is used as the crystalline resin, polycarbonate having a glass transition temperature (Tg) of 150 ° C. can be used as the amorphous resin.

The thickness of the resin film as the sub-gasket 5 may be uniform, but may differ depending on the position. For example, the thickness of the portion of the resin film that does not overlap with the electrolyte membrane 1 can be made larger than the thickness of the overlapping portion.

FIG. 4 shows an example of a sub-gasket 5B having a different thickness. The thickness d1 of the portion of the sub-gasket 5B that does not overlap with the electrolyte membrane 1 is larger than the thickness d2 of the overlapping portion. In the region where the thickness d2 is large, the distance between the facing sub-gaskets 5B is short, and the sub-gaskets 5B can be bonded to each other without a gap. Therefore, it is easy to insulate between the anode and the cathode with the sub-gasket 5B, and it is easy to prevent a short circuit.

The resin film containing the amorphous resin may be about 1.5 to 3 times thicker than the resin film made of the crystalline resin from the viewpoint of increasing the heat resistance. For example, in the case of a resin film made of a crystalline resin, when the thickness at which a certain gas barrier property is obtained is 25 to 100 μm, the thickness of the resin film containing the amorphous resin can be 40 to 200 μm.

(Fuel cell manufacturing method)
The fuel cell 10 can be manufactured as follows. First, a resin film is formed using a resin composition containing an amorphous resin. The film forming method is not particularly limited, and known methods such as a melt extrusion method, a casting method, and a coextrusion method can be used. The resin film is cut into a rectangular shape having a predetermined size by a cutter. The inside of the rectangular resin film is further cut into a rectangular shape by a cutter to manufacture a sub-gasket 5 having an opening in the center.

On the other hand, the coating device coats the electrolyte membrane 1 with the ink for forming the catalyst layer 21, and forms the electrolyte membrane 1 (CCM: Catalyst Coated Membrane) on which the catalyst layer 21 is laminated. The end portion of the electrolyte membrane 1 in this CCM is overlapped with the peripheral edge portion of the opening of the sub-gasket 5, and is hot-pressed. The conditions of the hot press are not particularly limited, but for example, the temperature is 150 to 180 ° C. and the pressure is 0.1 to 2 MPa. By the hot press, the overlapping portion of the sub-gasket 5 and the electrolyte membrane 1 is adhered, and the sub-gasket 5 is attached to the electrolyte membrane 1.

Next, the ink for forming the microporous layer 23 is coated on the porous substrate for the gas diffusion layer 22, and the gas diffusion layer 22 on which the microporous layer 23 is laminated is formed. The gas diffusion layer 22 is arranged on both sides of the CCM so that the microporous layer 23 is in contact with the CCM. Further, separators 4 are arranged on both sides thereof, and a fuel cell 10 in which a gas diffusion layer 22, a microporous layer 23, and a separator 4 are laminated in this order is manufactured on both sides of the CCM.

As described above, according to the present embodiment, since the resin film containing the amorphous resin is used as the sub-gasket 5, the sub-gasket 5 and the fuel cell 10 can be manufactured with a small number of processes.

When the sub-gasket 5 is a resin film made of a crystalline resin, it is common that a process of forming the film and then stretching the film is carried out. The crystallinity of the crystalline resin tends to gradually increase, and the increase in the crystallinity tends to cause fluctuations in the film size and non-uniformity of the film. By increasing the crystallinity in advance by stretching, such fluctuations can be reduced.

Since a resin film having high crystallinity has low adhesiveness to an adjacent member, a process of applying an adhesive to form an adhesive layer is further carried out. Here, when the protective sheet is provided on the adhesive layer, a process of laminating the protective sheet and a process of peeling off the protective sheet at the time of adhesion are also required.

Therefore, when a resin film made of a crystalline resin is used as the sub-gasket 5, the following process is carried out when the sub-gasket 5 is formed and incorporated into the fuel cell 10.
Step S1: Film formation Step S2: Film stretching Step S3: Adhesive is coated to form an adhesive layer Step S4: Protective sheet is laminated on the adhesive layer Step S5: Protective sheet is peeled off from the film Step S6: CCM Heat press the film

On the other hand, a resin film containing an amorphous resin, such as the sub-gasket 5 of the present embodiment, has higher adhesiveness to an adjacent member than a resin film made of a crystalline resin. Since the sub-gasket 5 can be adhered to the adjacent member by heating and pressurizing without using an adhesive, each process of forming the adhesive layer, laminating and peeling the protective sheet can be omitted. Further, in the case of a resin film made of an amorphous resin, the crystallinity does not increase with time, so that the stretching process is unnecessary.

That is, the following three steps are sufficient.
Step S1: Film formation Step S2: Film stretching Step S6: Heat-pressing the film on the CCM In the case of a resin film having an amorphous resin content of 100% by mass, the stretching process of step S2 can also be omitted.

As described above, since the sub-gasket 5 can be manufactured and the fuel cell 10 can be assembled with a small number of processes, the manufacturing process of the fuel cell 10 can be simplified. Also, the cost of the adhesive can be reduced.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

10 ... Fuel cell, 3 ... MEA, 1 ... Electrolyte membrane, 2 ... Electrode, 4 ... Separator, 5 ... Sub-gasket

Claims (8)

It is a sub-gasket (5) of the fuel cell (10) and
A resin film containing an amorphous resin,
Sub-gasket (5). The sub-gasket (5) according to claim 1, wherein the content ratio of the amorphous resin on the surface side of the resin film is higher than that on the inside. The resin film has a multilayer structure and has a multilayer structure.
The sub-gasket (5) according to claim 2, wherein the content ratio of the amorphous resin in the surface side layer is higher than that in the inner layer. The sub-gasket (5) according to any one of claims 1 to 3, wherein the glass transition temperature of the amorphous resin is higher than the temperature set as the temperature at the time of power generation of the fuel cell (10). The resin film further contains a crystalline resin and
The subgasket (5) according to any one of claims 1 to 4, wherein the glass transition temperature of the amorphous resin is lower than the melting point of the crystalline resin. The fuel cell (10) includes an electrolyte membrane (1).
The end portion of the resin film is arranged so as to be overlapped with the end portion of the electrolyte membrane (1).
The sub-gasket (5) according to any one of claims 1 to 5, wherein the thickness of the portion of the resin film that does not overlap with the electrolyte membrane (1) is larger than the thickness of the overlapping portion. A fuel cell (10) provided with an electrolyte membrane (1) and a sub-gasket (5) attached to the electrolyte membrane (1).
The fuel cell (10) in which the sub-gasket (5) is a resin film containing an amorphous resin. A method for manufacturing a fuel cell (10) including an electrolyte membrane (1) and a sub-gasket (5) attached to the electrolyte membrane (1).
The sub-gasket (5) is a resin film containing an amorphous resin.
The step of forming the resin film using the resin composition containing the amorphous resin, and
A step of obtaining the electrolyte membrane (1) to which the sub-gasket (5) is attached by superimposing the resin film on a part of the electrolyte membrane (1) and heating and pressurizing the resin film.
A method for manufacturing a fuel cell (10) including.

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