JP5277792B2 - Electrolyte membrane-electrode assembly with auxiliary membrane, and polymer electrolyte fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an electrolyte membrane-electrode assembly with an auxiliary film capable of extracting sufficient electromotive force, and preventing cracks of a gas diffusion layer; and a polymer electrolyte fuel cell using the same. <P>SOLUTION: The electrolyte membrane-electrode assembly with the auxiliary film includes: a solid polymer electrolyte membrane 2; catalyst layers 3 each having an outline matching the electrolyte membrane 2, and respectively formed throughout both the surfaces of the electrolyte membrane 2; auxiliary films 4 respectively installed on the respective catalyst layers 3, each formed into a frame-like shape having an opening 41 at the center, and formed slightly larger than the catalyst layer 3; and diffusion layers 5 respectively installed on the catalyst layers 3 exposed from the openings 41 of the respective auxiliary films 4. Outer peripheral parts 45 of the respective auxiliary films 4 are stuck to each other, and inner peripheral parts 46 thereof are stuck to outer peripheral parts 31 of the catalyst layers 3. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an electrolyte membrane-electrode assembly with an auxiliary membrane, and a polymer electrolyte fuel cell using the same.

  A fuel cell is a cell in which electrodes are arranged on both sides of an electrolyte and generates electricity by an electrochemical reaction between hydrogen and oxygen, and only water is generated during power generation. Thus, unlike the conventional internal combustion engine, it is expected to spread as a next-generation clean energy system because it does not generate environmental load gas such as carbon dioxide. In particular, the polymer electrolyte fuel cell has a low operating temperature and low electrolyte resistance. In addition, it uses a highly active catalyst, so it can obtain high output even in a small size. Is expected to be put to practical use.

  This polymer electrolyte fuel cell uses a proton-conducting solid polymer electrolyte membrane, and an electrode composed of a catalyst layer and a gas diffusion layer formed slightly smaller than the electrolyte membrane is formed on both surfaces of the electrolyte membrane. ing. And it has the structure which installed the frame-shaped gasket in the outer peripheral edge part of the electrolyte membrane so that the circumference | surroundings of this electrode might be enclosed, and also pinched | interposed these with the separator (for example, refer FIG. 1 of patent document 1). In the polymer electrolyte fuel cell having this configuration, the outer peripheral edge of the electrolyte membrane on which the gasket is installed is a portion that does not contribute to power generation, and generally there is a problem that an expensive electrolyte membrane cannot be effectively used. .

In order to solve this problem, for example, in the polymer electrolyte fuel cell described in FIG. 1 of Patent Document 2, a catalyst layer is formed on both surfaces of the electrolyte membrane, and a gas diffusion layer is provided on the catalyst layer. Yes. In order to install the gasket, an auxiliary membrane extending outward from the outer peripheral edge of the electrolyte membrane-electrode assembly is separately provided. In this way, by providing an auxiliary membrane separately and installing a gasket on the auxiliary membrane, the portion of the electrolyte membrane that does not contribute to power generation is eliminated.
JP 2006-286560 A JP 2004-47230 A

  However, the polymer electrolyte fuel cell separately provided with the auxiliary membrane as described above has a problem that the electromotive force that can be taken out is lower than that of the polymer electrolyte fuel cell not having the auxiliary membrane. There is also a problem that the gas diffusion layer laminated on the catalyst layer is easily cracked. If the gas diffusion layer is cracked, a large amount of gas flows only in the cracked portion, which causes a problem of uneven gas diffusion and eventually uneven reaction.

  Therefore, the present invention provides an electrolyte membrane-electrode assembly with an auxiliary membrane that can sufficiently extract an electromotive force and prevent cracking of a gas diffusion layer, and a polymer electrolyte fuel cell using the same. The task is to do.

  As a result of earnestly studying what causes the problem that the electromotive force of the polymer electrolyte fuel cell having the auxiliary membrane is lowered and the gas diffusion layer is easily cracked, the present inventors have made a catalyst layer. It has been found that an auxiliary film interposed between the gas diffusion layer and the gas diffusion layer causes a drop in electromotive force and a crack. That is, by the presence of the auxiliary membrane on the outer peripheral edge of the catalyst layer, the gas diffusion layer is installed such that the central portion is installed on the catalyst layer and the outer peripheral edge runs on the auxiliary membrane. . For this reason, a step is formed on the upper surface of the gas diffusion layer, and the separator installed on the gas diffusion layer has non-uniform contact with the gas diffusion layer, resulting in a decrease in current collection efficiency, and thus an electromotive force. The present inventors have found that this is the case. In addition, since a step is formed at the boundary between the catalyst layer and the auxiliary membrane on the surface where the gas diffusion layer is installed, stress concentrates on the portion corresponding to the step of the gas diffusion layer and cracks occur in that portion. The present inventors have also found that this has occurred.

  Accordingly, an electrolyte membrane-electrode assembly with an auxiliary membrane according to the present invention has a solid polymer electrolyte membrane and an outer shape that matches the electrolyte membrane in order to solve the above-described problems, and both surfaces of the electrolyte membrane. A catalyst layer formed on the whole, an auxiliary membrane installed on each of the catalyst layers and having a frame shape having an opening in the center and formed slightly larger than the catalyst layer; and Gas diffusion layers installed on the catalyst layers exposed from the openings, and the auxiliary membranes are bonded to each other at the outer peripheral edges, and the inner peripheral edges are bonded to the outer peripheral edges of the catalyst layers. ing.

  Since the electrolyte membrane-electrode assembly with an auxiliary membrane configured as described above includes an auxiliary membrane, a gasket can be installed on the auxiliary membrane. This eliminates the need to install a gasket on the electrolyte membrane, so that a catalyst layer can be formed on both surfaces of the electrolyte membrane, and all of the electrolyte membrane can contribute to power generation. Further, since the gas diffusion layer is installed on the catalyst layer in the opening of the auxiliary membrane, there is no step on the surface on which the gas diffusion layer is installed, and the upper surface of the gas diffusion layer is flat. Therefore, when a separator is installed on the gas diffusion layer, the separator is uniformly in contact with the gas diffusion layer, so that the current collection efficiency does not decrease, and a sufficient electromotive force can be taken out. Further, by flattening the surface on which the gas diffusion layer is installed, it is possible to solve the problem that stress concentrates on only a part of the gas diffusion layer and cracks occur. The auxiliary film has a frame shape, but the “frame shape” is a concept including a rectangular frame in plan view, a circular frame in plan view, and the like. In addition, the catalyst layer has an outer shape that matches the electrolyte membrane, but does not need to be completely matched. The auxiliary film is bonded to the catalyst layer or the like, and this “adhesion” is a concept including welding and adhesion.

  The auxiliary membrane-attached electrolyte membrane-catalyst layer assembly can have various configurations. For example, each auxiliary membrane is disposed on the catalyst layer side and adhered to the catalyst layer, a fuel gas, It is preferable to have a gas barrier layer that prevents permeation of the oxidant gas. In this way, the auxiliary membrane has a two-layer structure and is divided into a layer for adhering to the catalyst layer and a layer for preventing permeation of fuel gas and oxidant gas, so that each role can be surely fulfilled. Can be.

  Moreover, it is preferable that each said auxiliary | assistant film | membrane further has a 2nd contact bonding layer arrange | positioned in the outermost layer and adhere | attached with a gasket. According to this structure, a gasket can be reliably adhere | attached on an auxiliary | assistant film | membrane.

  In addition, a polymer electrolyte fuel cell according to the present invention has been made to solve the above-described problems, and is installed on each of the above-described electrolyte membrane-electrode assemblies with an auxiliary membrane and each auxiliary membrane. And a separator installed on each of the electrodes and the gasket.

  Thus, since the polymer electrolyte fuel cell according to the present invention uses any of the above-mentioned electrolyte membrane-electrode assemblies with an auxiliary membrane, the upper surface of the gas diffusion layer has no step. Therefore, since the separator uniformly contacts the gas diffusion layer, the current collection efficiency does not decrease, and a sufficient electromotive force can be taken out. In addition, since there is no step on the surface on which the gas diffusion layer is installed, it is possible to solve the problem that stress concentrates on a part of the gas diffusion layer and cracking occurs.

  According to the present invention, an electrolyte membrane-electrode assembly with an auxiliary membrane capable of taking out sufficient electromotive force and preventing cracking of a gas diffusion layer, and a polymer electrolyte fuel cell using the same are provided. can do.

  Hereinafter, embodiments of an electrolyte membrane-electrode assembly with an auxiliary membrane and a polymer electrolyte fuel cell according to the present invention will be described with reference to the drawings. FIG. 1 is a front sectional view of a polymer electrolyte fuel cell according to this embodiment, FIG. 2 is a plan view of the polymer electrolyte fuel cell according to this embodiment, and FIG. 3 is an electrolyte membrane-electrode assembly with an auxiliary membrane. It is an expanded front sectional view which shows the detail of the outer periphery part. In FIG. 2, the description of the separator and the gasket is omitted for easy understanding.

  As shown in FIGS. 1 and 2, the polymer electrolyte fuel cell 1 includes an electrolyte membrane-electrode assembly 20 including an electrolyte membrane 2, a catalyst layer 3, and a gas diffusion layer 5, and the electrolyte membrane-electrode assembly 20. The auxiliary film 4 extends outward from the auxiliary film 4, the gasket 6 installed on the auxiliary film 4, and the separator 7 that holds them. Hereinafter, each member will be described in detail.

  The electrolyte membrane 2 has a rectangular shape in plan view, and a catalyst layer 3 having substantially the same size and shape as the electrolyte membrane 2 is formed on the entire upper and lower surfaces of the electrolyte membrane 2. A structure in which the catalyst layer 3 is formed on both surfaces of the electrolyte membrane 2 is referred to as an electrolyte membrane-catalyst layer assembly 10.

  And the auxiliary membrane 4 is installed on each catalyst layer 3 so that this electrolyte membrane-catalyst layer assembly 10 may be clamped from the upper surface and the lower surface. The auxiliary membrane 4 has a frame shape having an opening 41 at the center, and the catalyst layer 3 is exposed from the opening 41 except for the outer peripheral edge 31, and the inner peripheral edge 46 (see FIG. 3) is bonded to the outer peripheral edge 31 of the catalyst layer 3. The auxiliary membrane 4 is formed to be slightly larger than the electrolyte membrane 2 and the catalyst layer 3, and the outer peripheral edge portions 45 (see FIG. 3) of the auxiliary membrane 4 located outside the catalyst layer 3 are bonded to each other. doing. The distance A from the outer peripheral edge of the auxiliary membrane 4 to the outer peripheral edge of the electrolyte membrane-catalyst layer assembly 10 is preferably 1 to 100 mm. The distance B from the inner peripheral edge of the auxiliary membrane 4 to the outer peripheral edge of the electrolyte membrane-catalyst layer assembly 10 is preferably 1 to 10 mm.

  The auxiliary membrane 4 having such a shape has a two-layer structure, and is a first gas-bonding layer 42 that prevents permeation of fuel gas and oxidant gas used for power generation of the fuel cell, and the catalyst layer 3. And an adhesive layer 43. The thickness of the gas barrier layer 42 is preferably 5 to 50 μm, and the thickness of the first adhesive layer 43 is preferably 1 to 50 μm.

  On the catalyst layer 3 exposed from the opening 41 of the auxiliary membrane 4, a gas diffusion layer 5 having a rectangular shape in plan view is provided. The distance C (see FIG. 3) from the outer peripheral edge of the gas diffusion layer 5 to the inner peripheral edge of the auxiliary film 4 is preferably 0 to 5 mm. Moreover, the film thickness of the gas diffusion layer 5 is thicker than the film thickness of the auxiliary film 4, and is preferably 200 to 400 μm. The catalyst layer 3 and the gas diffusion layer 5 constitute an electrode E, and the electrode E formed on both surfaces of the electrolyte membrane 2 is called an electrolyte membrane-electrode assembly 20. As in the present embodiment, the electrolyte membrane-electrode assembly 20 provided with the auxiliary membrane 4 corresponds to the electrolyte membrane-electrode assembly with an auxiliary membrane of the present invention.

  A frame-like gasket 6 is installed on the auxiliary film 4, and a separator 7 is installed on the electrode E and the gasket 6. In the separator 7, a gas flow path 71 is formed in a region facing the gas diffusion layer 5.

  Next, the material of each component of the polymer electrolyte fuel cell 1 configured as described above will be described.

  The electrolyte membrane 2 is formed, for example, by applying a solution containing a hydrogen ion conductive polymer electrolyte on a substrate and drying it. Examples of the hydrogen ion conductive polymer electrolyte include a perfluorosulfonic acid-based fluorine ion exchange resin, more specifically, a perfluorocarbonsulfonic acid-based resin in which the C—H bond of a hydrocarbon ion-exchange membrane is substituted with fluorine. Examples include polymers (PFS polymers). By introducing a fluorine atom having high electronegativity, it is chemically very stable, the dissociation degree of the sulfonic acid group is high, and high ion conductivity can be realized. Specific examples of such a hydrogen ion conductive polymer electrolyte include “Nafion” (registered trademark) manufactured by DuPont, “Flemion” (registered trademark) manufactured by Asahi Glass Co., Ltd., and “Aciplex” manufactured by Asahi Kasei Corporation. ”(Registered trademark),“ Gore Select ”(registered trademark) manufactured by Gore, and the like. The concentration of the hydrogen ion conductive polymer electrolyte contained in the hydrogen ion conductive polymer electrolyte-containing solution is usually about 5 to 60% by weight, preferably about 20 to 40% by weight. In addition, the film thickness of the electrolyte membrane 2 is about 20-250 micrometers normally, Preferably it is about 20-80 micrometers. In addition to the hydrogen ion conductive polymer electrolyte membrane, an anion conductive solid polymer electrolyte membrane and a liquid substance-impregnated membrane are also included. Examples of the anion conductive electrolyte membrane include a hydrocarbon resin or a fluorine resin, and specific examples of the hydrocarbon resin include Aciplex (registered trademark) A201, 2111, 221 manufactured by Asahi Kasei Corporation, and Tokuyama. Neocepta (registered trademark) AM-1, AHA, etc. manufactured by Co., Ltd. may be mentioned, and examples of the fluorine-based resin may include Tosflex (registered trademark) IE-SF34 manufactured by Tosoh Corporation. Examples of the liquid substance-impregnated film include polybenzimidazole (PBI).

  The catalyst layer 3 is a known platinum-containing catalyst layer (cathode catalyst and anode catalyst). Specifically, the catalyst layer 3 contains carbon particles supporting catalyst particles and a hydrogen ion conductive polymer electrolyte. Examples of the catalyst particles include platinum and platinum compounds. Examples of the platinum compound include an alloy of platinum and at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, iron and the like. In general, the catalyst particles contained in the cathode catalyst layer are platinum, and the catalyst particles contained in the anode catalyst layer are an alloy of the metal and platinum. Moreover, as a hydrogen ion conductive polymer electrolyte, the same material as what is used for the electrolyte membrane 2 mentioned above can be used.

  The auxiliary film 4 is composed of a gas barrier layer 42 and a first adhesive layer 43. The gas barrier layer 42 is made of polyester, polyamide, polyimide, polymethyl having barrier properties against water vapor, water, fuel gas and oxidant gas. Tempen, polyphenylene oxide, polysulfone, polyether ether ketone, polyphenylene sulfide and the like can be preferably used. Specific examples of the polyester include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate.

  The material of the first adhesive layer 43 is preferably a polyolefin resin, such as medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α / olefin copolymer, polypropylene, polybutene, polyisobutene, Copolymer of ethylene and unsaturated carboxylic acid such as polyisobutylene, polybutadiene, polyisoprene, ethylene-methacrylic acid copolymer, or ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ionomer resin, An ethylene-vinyl acetate copolymer or the like can be used. In addition, acid-modified polyolefin resins and silane-modified polyolefin resins modified with them can be used. Among them, it is insulating to use polypropylene modified with unsaturated carboxylic acid or polyethylene modified with unsaturated carboxylic acid. Or it is preferable in terms of heat resistance.

  As the gas diffusion layer 5, various types of gas diffusion layers constituting a fuel electrode and an air electrode can be used. In order to efficiently supply fuel gas and oxidant gas as fuel to the catalyst layer 3, the gas diffusion layer 5 is porous. It is made of a conductive substrate. Examples of the porous conductive substrate include carbon paper and carbon cloth.

  As the gasket 6, it is possible to use a gasket that has a strength sufficient to withstand heat pressing and has a gas barrier property that does not leak fuel and oxidant to the outside. For example, a polyethylene terephthalate sheet or Teflon ( (Registered trademark) sheet, silicon rubber sheet, and the like.

  The separator 7 may be any known conductive plate that is known and stable even in the environment within the fuel cell. In general, a carbon plate in which a gas flow path 71 is formed is used. In addition, the separator 7 is made of a metal such as stainless steel, and the surface of the metal is formed with a coating made of a conductive material such as chromium, a platinum group metal or oxide thereof, or a conductive polymer. It is also possible to use a metal having a metal surface plated with a material such as silver, a platinum group composite oxide, or chromium nitride.

  Next, a method for producing the above-described polymer electrolyte fuel cell 1 will be described with reference to the drawings. FIG. 4 is an explanatory view showing a method for producing the polymer electrolyte fuel cell 1 according to this embodiment.

As shown in FIG. 4, an electrolyte membrane 2 made of the above-described material is prepared, and a catalyst layer forming transfer sheet 8 is placed on both surfaces of the electrolyte membrane 2 in an overlapping manner. Here, the transfer sheet 8 for forming a catalyst layer is one in which the transferred catalyst layer 3 is formed on a transfer substrate 81. The production method of the catalyst layer forming transfer sheet 8 will be described. First, the above-described carbon particles supporting the catalyst particles and the hydrogen ion conductive polymer electrolyte are mixed and dispersed in an appropriate solvent to prepare a catalyst paste. . Then, the catalyst paste is applied onto the transfer substrate 81 through a release layer as necessary in accordance with a known method so that the formed catalyst layer 3 has a desired film thickness. At this time, the catalyst paste is applied to the transfer substrate 81 so that the catalyst layer 3 has the same size and shape as the electrolyte membrane 2. Examples of the method for applying the catalyst paste include known coating methods such as screen printing, spray coating, die coating, and knife coating. Examples of the solvent include various alcohols, various ethers, various dialkyl sulfoxides, water, or a mixture thereof. Of these, alcohols are preferable. Examples of alcohols include monohydric alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol, and various polyhydric alcohols. As the transfer substrate 81, for example, polyimide, polyethylene terephthalate, polyparvanic acid aramid, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, polyethylene naphthalate. And the like. Further, heat resistance of ethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), etc. Fluorine resin can also be used. Further, the transfer substrate 81 may be coated paper such as art paper, coated paper, lightweight coated paper, non-coated paper such as notebook paper, copy paper, etc. in addition to the polymer film. The thickness of the transfer substrate 81 is usually about 6 to 100 μm, preferably about 10 to 30 μm, from the viewpoints of handleability and economy. Therefore, the transfer substrate 81 is preferably a polymer film that is inexpensive and easily available, and more preferably polyethylene terephthalate.

  Then, after applying the catalyst paste, the catalyst layer 3 is formed on the transfer substrate 81 by drying at a predetermined temperature and time. A drying temperature is about 40-100 degreeC normally, Preferably it is about 60-80 degreeC. Although depending on the drying temperature, the drying time is usually about 5 minutes to 2 hours, preferably about 10 minutes to 1 hour.

Returning to FIG. 4, the description of the method for producing the polymer electrolyte fuel cell will be continued. The transfer sheet 8 for forming a catalyst layer prepared as described above is arranged so that the catalyst layer 3 faces the electrolyte membrane 2 (FIG. 4A), and a heat press is applied from the back side of the transfer sheet 8 to apply the catalyst layer. 3 is transferred to the electrolyte membrane 2, and the transfer substrate 81 of the transfer sheet 8 is peeled off (FIG. 4B). In consideration of workability, it is preferable to simultaneously laminate the catalyst layer 3 on both surfaces of the electrolyte membrane 2, but the catalyst layer 3 can also be formed on each side. The pressure level of the heating press is usually about 0.5 to 20 MPa, preferably about 1 to 10 MPa in order to avoid transfer failure. Further, it is preferable to heat the pressing surface during this pressing operation in order to avoid transfer failure. The heating temperature is usually 200 ° C. or lower, preferably 150 ° C. or lower, in order to avoid damage or deformation of the electrolyte membrane 2. Thus, the electrolyte membrane-catalyst layer assembly 10 is formed by forming the catalyst layers 3 on both surfaces of the electrolyte membrane 2. At this time, each catalyst layer 3 is formed so as to cover the entire upper surface or lower surface of the electrolyte membrane 2.

  Next, the auxiliary membrane 4 is attached to the electrolyte membrane-catalyst layer assembly 10 thus formed (FIG. 4C). This process will be described in detail with reference to FIG. FIG. 5 is a plan view showing a process of attaching the auxiliary membrane 4 to the electrolyte membrane-catalyst layer assembly 10. As shown in FIG. 5, the two auxiliary films 4 made of the above-described materials are overlapped, and the remaining three sides with the one side remaining are welded together. As a result, the two auxiliary films 4 are formed into a bag body in which a welded portion is formed in a U-shape and the left side is open (FIG. 5A). As this welding method, various known methods can be adopted. For example, high-frequency welding, hot air welding, hot plate welding, impulse welding, trowel welding, ultrasonic welding, etc. can be adopted. .

  When the bag is formed by the auxiliary membrane 4, next, an easily removable region 44 that is slightly smaller than the catalyst layer 3 of the electrolyte membrane-catalyst layer assembly 10 is formed at the center of each auxiliary membrane 4 constituting the bag. (FIG. 5B). The easy removal region 44 refers to a region that can be easily removed. For example, the easy removal region 44 can be formed by making a perforation in the outer peripheral edge or making a cut while leaving only a part. The electrolyte membrane-catalyst layer assembly 10 is inserted into the bag body in which the easy-removal region 44 is formed in this manner from the unwelded left side and moved to a predetermined position (FIG. 5C). The predetermined position refers to a position where the catalyst layer 3 of the electrolyte membrane-catalyst layer assembly 10 faces the easy removal region 44 except for the outer peripheral edge 31.

After the electrolyte membrane-catalyst layer assembly 10 is moved to a predetermined position, the perforation at the outer periphery of the easy removal region 44 is cut and the easy removal region 44 is removed from each auxiliary membrane 4, thereby An opening 41 is formed at the center (FIG. 5D). As described above, when the easy removal region 44 is removed from each auxiliary membrane 4 to form the opening 41, the catalyst layer 3 of the electrolyte membrane-catalyst layer assembly 10 is removed from each opening 41 except for the outer peripheral edge 31. It will be exposed. In this state, the remaining portion of the auxiliary membrane 4 that has not been welded is welded by a known method, so that the auxiliary membrane 4 is formed by the outer peripheral edge 31 or the catalyst layer 3 of the electrolyte membrane -catalyst layer assembly 10. While being welded to the outer peripheral edge portion 21 of the electrolyte membrane 2, the outer peripheral edge portions 45 of the auxiliary membrane 4 are also welded together. The electrolyte membrane-catalyst layer assembly with an auxiliary membrane is completed through the above steps (FIGS. 5E and 4C).

  Returning to FIG. 4, the description of the method for producing the polymer electrolyte fuel cell 1 will be continued. On the catalyst layer 3 exposed from the opening 41 of the electrolyte membrane-catalyst layer assembly described above, the gas diffusion layer 5 is laminated by thermocompression bonding, so that the electrolyte membrane-electrode assembly with the auxiliary membrane is formed. Completed (FIG. 4D). Subsequently, a gasket 6 is disposed on the auxiliary film 4 so as to surround the periphery of the electrode E composed of the catalyst layer 3 and the gas diffusion layer 5. The separator 7 is disposed on the gas diffusion layer 5 and the gasket 6 so that the gas flow path 71 faces the gas diffusion layer 5 so that the gas diffusion layer 5 and the separator 7 are electrically connected. By sandwiching the electrolyte membrane-electrode assembly with the separator 7, the solid polymer fuel cell 1 is completed (FIG. 4E).

  As described above, in the present embodiment, since the electrolyte membrane-electrode assembly 20 has the auxiliary membrane 4, the gasket 6 can be installed on the auxiliary membrane 4. Therefore, it is not necessary to install a gasket on the electrolyte membrane 2, the catalyst layer 3 can be formed on the entire electrolyte membrane 2, and the entire electrolyte membrane 2 can contribute to power generation. The gas diffusion layer 5 is formed on the catalyst layer 3 exposed from the opening 41 in the opening 41 of the auxiliary film 4. Since the gas diffusion layer 5 is thus formed in the opening 41 of the auxiliary film 4, the surface on which the gas diffusion layer 5 is formed is flat and the upper surface of the gas diffusion layer 5 can also be flat. Therefore, since the separator 7 is in uniform contact with the gas diffusion layer 5, the current collection efficiency does not decrease and a sufficient electromotive force can be taken out. Further, since the surface on which the gas diffusion layer 5 is installed is flat, it is possible to prevent stress from concentrating on a part of the gas diffusion layer 5 and causing cracks.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention. For example, in the above-described embodiment, a manufacturing method is employed in which the auxiliary membrane 4 is once formed into a bag and the electrolyte membrane-catalyst layer assembly 10 is inserted. However, the present invention is not particularly limited thereto. For example, the auxiliary membrane 4 in which the opening 41 is formed in advance on both surfaces of the electrolyte membrane-catalyst layer assembly 10 is arranged so that the first adhesive layer 43 faces the electrolyte membrane-catalyst layer assembly 10, respectively. The auxiliary membrane 4 may be welded to both surfaces of the electrolyte membrane-catalyst layer assembly 10 by a known welding method or the like to produce an electrolyte membrane-catalyst layer assembly with an auxiliary membrane.

In the above embodiment, the auxiliary membrane 4 is adhered to the electrolyte membrane-catalyst layer assembly 10 by welding. However, for example, the auxiliary membrane 4 can be adhered to the electrolyte membrane-catalyst layer assembly 10. In this case, as the material of the first adhesive layer 43 of the auxiliary film 4, for example, an acrylic, rubber, or silicone pressure sensitive adhesive can be used. Specifically, acrylic ester copolymers, methacrylic ester copolymers, natural rubber (NR), synthetic natural rubber (IR), styrene-butadiene rubber (SBR), polyisobutylene (PIB), butyl rubber (IIR) And silicone rubber. In this case, various methods can be employed as a method for causing the first adhesive layer 43 to adhere to the electrolyte membrane-catalyst layer assembly 10. For example, the auxiliary membrane 4 is disposed on the electrolyte membrane-catalyst layer assembly 10 and then the hand roller is rolled on the auxiliary membrane 4 to adhere the auxiliary membrane 4 to the electrolyte membrane- catalyst layer assembly 10 or press. It can also be crimped by. In addition, the pressure for adhesion is sufficiently lower than the pressure for thermocompression bonding. For example, the auxiliary membrane 4 is sufficiently joined to the electrolyte membrane-catalyst layer at a pressure of about 0.01 to 0.3 MPa. The body 10 can be adhered.

  Moreover, in the said embodiment, although the auxiliary | assistant film | membrane 4 is comprised from two layers, the gas barrier layer 42 and the 1st contact bonding layer 43, three or more layers may be sufficient. For example, as shown in FIG. 6, each auxiliary film 4 can have a three-layer structure. In this case, each auxiliary film 4 includes a first adhesive layer 43 and a gas barrier layer 42 in order from the electrolyte film 2 side. The second adhesive layer 47 is provided. The first adhesive layer 43 is configured to adhere to the electrolyte membrane-catalyst layer assembly 10. On the first adhesive layer 43, a gas barrier layer 42 for preventing permeation of fuel gas and oxidant gas used for power generation of the fuel cell is formed. Further, a second adhesive layer 47 configured to adhere to the gasket 6 is formed on the gas barrier layer 42. The second adhesive layer 47 has a higher melting point than the first adhesive layer 43, and the melting point of the second adhesive layer 47 is about 30 to 60 ° C. higher than the melting point of the first adhesive layer 43. It is preferable. Thus, by making the melting point of the second adhesive layer 47 higher than the melting point of the first adhesive layer 43, the following effects can be obtained. That is, when the auxiliary membrane 4 is welded to the electrolyte membrane-catalyst layer assembly 10, first, the auxiliary membrane 4 may be welded at a temperature higher than the melting point of the first adhesive layer 43 and lower than the melting point of the second adhesive layer 47. it can. Thereby, first, only the first adhesive layer 43 can be melted and the auxiliary membrane 4 can be welded to the electrolyte membrane-catalyst layer assembly 10. Then, by welding at a temperature higher than the melting point of the second adhesive layer 47, the second adhesive layer 47 can be melted and welded to the gasket 6. By adopting such a welding method, heat applied to the electrolyte membrane-catalyst layer assembly 10 can be reduced, and thermal damage can be reduced. The first adhesive layer 43 is preferably 1 to 50 μm, the thickness of the gas barrier layer 42 is preferably 6 to 20 μm, and the thickness of the second adhesive layer 47 is 1 to 50 μm. It is preferable that

  In the above embodiment, the electrolyte membrane 2, the catalyst layer 3, and the gas diffusion layer 5 constituting the solid polymer fuel cell 1 are all described as a rectangular shape in plan view, but the shape is not particularly limited, For example, it can be a circular shape in plan view.

  The present invention will be described more specifically with reference to the following examples and comparative examples. In addition, this invention is not limited to the following Example.

Example 1
An electrolyte membrane-electrode assembly with an auxiliary membrane as shown in FIG. 1 was produced. As the electrolyte membrane 2, NRE212CS (manufactured by Dupont) having a film thickness of 53 μm cut to a size of 53 × 53 mm was used.

Next, a transfer sheet 8 for forming a catalyst layer was produced in the following manner. First, 2 g of platinum catalyst-supported carbon (platinum support amount: 45.7 wt%, manufactured by Tanaka Kikinzoku Co., Ltd., TEC10E50E), 1-butanol 10 g, 3-butanol 10 g, fluororesin (5 wt% Nafion binder, manufactured by DuPont) 20 g and 6 g of water was added, and these were stirred and mixed with a disperser to prepare an ink composition for forming a catalyst layer. Next, the ink was applied to a polyester film (Toray, X44, 25 μm) so that the weight of platinum after drying the catalyst layer was 0.4 mg / cm ² to prepare a transfer sheet 8 for forming a catalyst layer.

  The catalyst layer forming transfer sheet 8 produced as described above was cut into a size of 53 × 53 mm, and placed on both surfaces of the electrolyte membrane 2 so that the catalyst layer 3 was directed to the electrolyte membrane 2 side. The catalyst layer 3 was formed on both surfaces of the electrolyte membrane 2 by hot pressing under conditions of 135 ° C., 5.0 MPa, 150 seconds, and the electrolyte membrane-catalyst layer assembly 10 was produced. The catalyst layer 3 has a thickness of 20 μm.

  Subsequently, the auxiliary film 4 was produced. As the gas barrier layer 42 of the auxiliary film 4, biaxially stretched polyethylene naphthalate (manufactured by Teijin Limited, Teonex, 12 μm) was used. On this polyethylene naphthalate, unsaturated carboxylic acid graft-modified polypropylene was extruded at a thickness of 30 μm by melt extrusion to form a first adhesive layer 43. The auxiliary film 4 was cut to a size of 80 × 80 mm, and an opening 41 having a size of 50 × 50 mm was formed at the center. And the auxiliary membrane 4 is arrange | positioned centering on both surfaces of the electrolyte membrane-catalyst layer assembly | attachment 10, and the auxiliary membrane 4 is electrolyte membrane-catalyst layer by heat-pressing on conditions of 130 degreeC, 1.0 Mpa, and 30 second. It welded to the conjugate | zygote 10 and the electrolyte membrane-catalyst layer conjugate | zygote with an auxiliary membrane was produced.

  Subsequently, on the catalyst layer 3 exposed from the opening 41, a carbon paper (TGP-H-090, manufactured by Toray Industries, Inc., thickness 280 μm) cut into a size of 49 × 49 mm as the gas diffusion layer 5 is used. ) To form an electrolyte membrane-electrode assembly with an auxiliary membrane. On the gas barrier layer 42 of the electrolyte membrane-electrode assembly with an auxiliary membrane formed as described above, an ethylene-propylene rubber gasket 6 (NOK, EPDM, thickness: 250 μm) was placed.

(Example 2)
An electrolyte membrane-electrode assembly with an auxiliary membrane in which the auxiliary membrane 4 has a three-layer structure as shown in FIG. 6 was produced. The polymer electrolyte fuel cell of Example 2 is manufactured with the same material, dimensions, and manufacturing method as Example 1 described above except that the auxiliary membrane 4 has a three-layer structure. The auxiliary film 4 of Example 2 will be described. First, as the gas barrier layer 42, biaxially stretched polyethylene naphthalate (Teonex, 12 μm) was used. Unsaturated carboxylic acid graft-modified polyethylene was extruded to a thickness of 15 μm on the lower surface of the gas barrier layer 42 by melt extrusion to form a first adhesive layer 43. Further, an unsaturated carboxylic acid graft-modified polypropylene was extruded to a thickness of 15 μm on the upper surface of the gas barrier layer 42 to form a second adhesive layer 47. The auxiliary film 4 was cut to a size of 80 × 80 mm, and an opening 41 having a size of 50 × 50 mm was formed at the center. Then, the auxiliary membrane 4 is disposed on both surfaces of the electrolyte membrane-catalyst layer assembly 10 so that the first adhesive layers 43 having a melting point of 110 ° C. face each other, and heat is applied at 100 ° C., 1.0 MPa, and 30 seconds. The auxiliary membrane 4 was welded to the electrolyte membrane-catalyst layer assembly 10 by pressing to produce an electrolyte membrane-catalyst layer assembly with an auxiliary membrane. The melting point of 146 ° C. The second ethylene-propylene rubber gasket 6 on the adhesive layer 47 of the (NOK Corp., EPDM, thickness 200 [mu] m) after placing, 130 ° C., 1.0 MPa, under conditions of 30 seconds the heat pressed gasket 6 adhered to the second adhesive layer 47. The melting point of the adhesive layer was measured using a differential scanning calorimeter according to JISK7121.

(Example 3)
An electrolyte membrane-electrode assembly with an auxiliary film was produced by the same material, dimensions, and manufacturing method as in Example 1 except that the material of the auxiliary film 4 was different and the bonding conditions of the auxiliary film 4 were different. In addition, the auxiliary film 4 used biaxially stretched polyethylene terephthalate (manufactured by Teijin Ltd., Teflex, thickness 20 μm) as the gas barrier layer 42. On this polyethylene terephthalate, unsaturated carboxylic acid graft-modified polyethylene was extruded at a thickness of 30 μm by melt extrusion to form a first adhesive layer 43. The auxiliary membrane 4 is placed centered on both surfaces of the electrolyte membrane-catalyst layer assembly 10 and hot-pressed under the conditions of 100 ° C., 1.0 MPa, and 30 seconds, whereby the auxiliary membrane 4 is joined to the electrolyte membrane-catalyst layer. It adhered to the body 10 to produce an electrolyte membrane-electrode assembly with an auxiliary membrane . On the gas barrier layer 42 of the electrolyte membrane-electrode assembly with an auxiliary membrane formed as described above, an ethylene-propylene rubber gasket 6 (NOK, EPDM, thickness: 250 μm) was placed.

Example 4
Except that the electrolyte membrane 2 and the transfer sheet 8 for forming a catalyst layer are cut to a size of 56 × 56 mm, the electrolyte membrane-electrode assembly with an auxiliary membrane is the same material, dimensions, and manufacturing method as in Example 1 described above. Was made. Then, an ethylene propylene rubber gasket 6 (manufactured by NOK, EPDM, thickness 250 μm) was placed on the gas barrier layer 42.

(Example 5)
Except for the point that the material of the auxiliary membrane 4 is different and the press conditions when the auxiliary membrane 4 is adhered to the electrolyte membrane-catalyst layer assembly 10 are different, the same materials, dimensions, and manufacture as in Example 1 described above. By the method, an electrolyte membrane-electrode assembly with an auxiliary membrane was produced.

  In addition, as the auxiliary film 4 of Example 5, Proswell (manufactured by Nitto Denko Corporation, PW-3610A) was used. The proswell is composed of a gas barrier layer 42 made of polyimide having a thickness of 25 μm and a first adhesive layer 43 made of acrylic resin having a thickness of 10 μm. The pressing conditions for adhering the auxiliary membrane 4 to the electrolyte membrane-catalyst layer assembly 10 were normal temperature (25 ° C.), 0.3 MPa, and 30 seconds. On the gas barrier layer 42 of the electrolyte membrane-electrode assembly with an auxiliary membrane formed in this manner, an ethylene propylene rubber gasket 6 (manufactured by NOK, EPDM, thickness 250 μm) was placed.

(Comparative Example 1)
As Comparative Example 1, the same electrolyte membrane-electrode assembly with an auxiliary membrane as in Example 1 was produced except that the size of the gas diffusion layer 5 and the lamination method were different (see FIG. 7). The gas diffusion layer 5 was cut into the same size of 53 × 53 mm as the electrolyte membrane 2 and the catalyst layer 3. The gas diffusion layer 5 was installed on the catalyst layer 3 with the auxiliary membrane 4 interposed therebetween. On the gas barrier layer 42 of the electrolyte membrane-electrode assembly with this auxiliary membrane, an ethylene propylene rubber gasket 6 (NODM, EPDM, thickness 250 μm) was placed.

(Comparative Example 2)
The same material as in Example 1 except that the gas diffusion layer 5 was cut to a size of 53 × 53 mm and the electrolyte membrane 2 and the transfer sheet 8 for forming a catalyst layer were cut to a size of 50 × 50 mm. Then, an electrolyte membrane-electrode assembly with an auxiliary membrane was produced using the dimensions and the manufacturing method (see FIG. 8). On the gas barrier layer 42 of this electrolyte membrane-electrode assembly with an auxiliary membrane, an ethylene propylene rubber gasket 6 (NOK, EPDM, thickness 250 μm) was placed.

(Comparative Example 3)
The same material as in Example 5 except that the gas diffusion layer 5 was cut to a size of 53 × 53 mm and the electrolyte membrane 2 and the transfer sheet 8 for forming a catalyst layer were cut to a size of 50 × 50 mm. Then, an electrolyte membrane-electrode assembly with an auxiliary membrane was produced using the dimensions and the manufacturing method (see FIG. 8). Then, a gasket 6 made of ethylene propylene rubber (manufactured by NOK, EPDM, thickness: 250 μm) was placed on the gas barrier layer 42 of the electrolyte membrane-electrode assembly with an auxiliary membrane .

(Comparative Example 4)
The same material as in Example 2 except that the gas diffusion layer 5 was cut to a size of 53 × 53 mm and the electrolyte membrane 2 and the transfer sheet 8 for forming a catalyst layer were cut to a size of 50 × 50 mm. Then, an electrolyte membrane-electrode assembly with an auxiliary membrane was produced using the dimensions and the manufacturing method (see FIG. 8). Then, the auxiliary film-coated membrane - the gasket 6 made of ethylene propylene rubber on the electrode assembly the second adhesive layer 47 (NOK Corp., EPDM, thickness 200 [mu] m) after placing, 130 ° C., 1.0 MPa For 30 seconds.

(Evaluation method)
With respect to the electrolyte membrane-electrode assemblies with auxiliary membranes of Examples 1 to 5 and the electrolyte membrane-electrode assemblies of Comparative Examples 1 to 4, separators 7 were installed to produce polymer electrolyte fuel cells. The current-voltage characteristics of the molecular fuel cell were evaluated. At that time, when the resistance value (Ω) of the electrolyte membrane-electrode assembly with an auxiliary membrane sandwiched between the separators 7 was measured with a resistance meter, the resistance value of Example 1 was 4.7 mΩ, Example 2 was 5.0 mΩ, Example 3 is 4.8 mΩ, Example 4 is 3.8 mΩ, and Example 5 is 4.0 mΩ, while Comparative Example 1 is 20.0 mΩ, Comparative Example 2 is 26.7 mΩ, and Comparative Example 3 is It was 47.0 mΩ and Comparative Example 4 was 29.0 mΩ. The electromotive force is 0.990 V in Example 1, 0.984 V in Example 2, 0.995 in Example 3, 0.989 V in Example 4, and 0.975 V in Example 5, whereas The comparative example 1 was 0.828V, the comparative example 2 was 0.350V, the comparative example 3 was 0.404V, and the comparative example 4 was 0.366V.

Moreover, about the electrolyte membrane-electrode assembly with an auxiliary membrane of the said Examples 1-5 and the electrolyte membrane-electrode assembly with an auxiliary membrane of Comparative Examples 1-4, the separator 7 was installed and a polymer electrolyte fuel cell was installed. Each was produced and the load fluctuation cycle test was implemented. The measurement conditions at this time were a cell temperature of 80 ° C., a fuel utilization rate of 70%, an oxidant utilization rate of 40%, and a humidification temperature of 50 ° C. In addition, as a load variation cycle test, a cycle in which power was generated at a current density of 0.3 A / cm ^{2 for} 1 minute and then generated at a current density of 0.01 A / cm ^{2 for} 1 minute was repeated. As a result of the load fluctuation cycle test, the voltage does not decrease even after 1600 hours for the fuel cell of Example 1 and 1000 hours for the fuel cell of Examples 2 to 5, and this load fluctuation cycle test. When the electrolyte membrane was confirmed later, the electrolyte membrane was not damaged. On the other hand, in the fuel cell of Comparative Example 1, a decrease in voltage was confirmed at the time when 100 hours had elapsed, and after the load fluctuation cycle test was conducted, damage to the electrolyte membrane 2 was visually confirmed. In the fuel cells of Comparative Examples 2 to 4, the load fluctuation cycle test could not be measured, and the durability time was 0 hour. This is considered to be caused by a gas leak from between the opening 41 of the auxiliary membrane 4 and the electrolyte membrane-catalyst layer assembly. Moreover, as a result of measuring the leakage current amount after the load fluctuation cycle test, the leakage current amount of the fuel cell of Examples 1 to 5 was 1 mA / cm ² or less, whereas the leakage current amount of the fuel cell of Comparative Example 1 was 20 mA / cm ^2. cm ² or more, in the amount of leakage current of the fuel cell of Comparative example 2-4 is 30 mA / cm ² or more, the electrolyte membrane breakage or gas leakage by sealing poor were seen. Table 1 shows the test results.

  As described above, since the polymer electrolyte fuel cells of Examples 1 to 5 have a lower resistance value and a higher electromotive force than the polymer electrolyte fuel cells of Comparative Examples 1 to 4, the current collection efficiency is high. It was found that the fuel cell performance was high.

1 is a front sectional view showing an embodiment of a polymer electrolyte fuel cell according to the present invention. 1 is a plan view showing an embodiment of a polymer electrolyte fuel cell according to the present invention. It is an expanded front sectional view showing the details of the outer periphery part of the membrane electrode assembly with an auxiliary membrane concerning this embodiment. It is explanatory drawing which shows the manufacturing method of the polymer electrolyte fuel cell which concerns on this embodiment. It is explanatory drawing which shows the manufacturing method of the electrolyte membrane-catalyst layer assembly | attachment with an auxiliary membrane which concerns on this embodiment. It is front sectional drawing which shows other embodiment of the polymer electrolyte fuel cell which concerns on this invention. 2 is a front sectional view showing a polymer electrolyte fuel cell of Comparative Example 1. FIG. It is front sectional drawing which shows the polymer electrolyte fuel cell of Comparative Examples 2-4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte fuel cell 2 Electrolyte membrane 21 Outer peripheral edge part 3 of electrolyte membrane Catalyst layer 31 Outer peripheral edge part 4 of catalyst layer Auxiliary film 41 Opening part 42 Barrier layer 43 First adhesive layer 45 Outer peripheral edge part 46 of auxiliary film Inner peripheral edge portion 47 of the auxiliary membrane Second adhesive layer 5 Gas diffusion layer 6 Gasket 7 Separator 10 Electrolyte membrane-catalyst layer assembly 20 Electrolyte membrane-electrode assembly

Claims (4)

A solid polymer electrolyte membrane;
A catalyst layer having an outer shape that matches the electrolyte membrane, and formed on each of both surfaces of the electrolyte membrane;
An auxiliary membrane that is installed on each of the catalyst layers and has a frame shape having an opening in the center and is formed slightly larger than the catalyst layer;
A gas diffusion layer installed only on the catalyst layer exposed from the opening of each auxiliary membrane, and
Each of the auxiliary membranes is an electrolyte membrane-electrode assembly with an auxiliary membrane in which outer peripheral edges are bonded to each other and an inner peripheral edge is bonded to an outer peripheral edge of the catalyst layer.   2. The auxiliary according to claim 1, wherein each auxiliary film includes a first adhesive layer that is disposed on the catalyst layer side and adheres to the catalyst layer, and a gas barrier layer that prevents permeation of fuel gas and oxidant gas. Electrolyte membrane-electrode assembly with membrane.   Each said auxiliary | assistant film | membrane is an electrolyte membrane electrode assembly with an auxiliary | assistant film | membrane of Claim 2 which further has a 2nd contact bonding layer arrange | positioned in the outermost layer and adhere | attaches with a gasket. An electrolyte membrane-electrode assembly with an auxiliary membrane according to any one of claims 1 to 3,
A gasket installed on each auxiliary membrane;
Separators respectively installed on the electrodes and gaskets;
A solid polymer fuel cell comprising:

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