JP6115238B2 - Membrane electrode structure and manufacturing method thereof - Google Patents

Description

  The present invention relates to a membrane electrode structure in a polymer electrolyte fuel cell and a method for producing the same.

  A fuel cell that reacts a fuel such as hydrogen with an oxidant such as oxygen and directly converts the resulting chemical energy into electric energy is alkaline, phosphoric acid, solid polymer, molten carbonate, depending on the type of electrolyte It is classified into solid oxide form. Polymer polymer fuel cell (PEFC) has a shorter start-up time than other fuel cells, can operate at low temperature, has high power density, and can be reduced in size and weight. Therefore, application as a portable power source, a household power source, and an in-vehicle power source is expected.

  The polymer electrolyte fuel cell includes a structure in which a pair of electrode catalyst layers are arranged on both sides of an electrolyte membrane called a membrane electrode assembly (MEA), and one of the electrode catalyst layers contains hydrogen. It is a battery that is sandwiched between a pair of separator plates that form a gas flow path for supplying a fuel gas and supplying an oxidant gas containing oxygen to the other electrode catalyst layer. A battery sandwiched between the pair of separator plates is called a single battery cell.

  Gaskets constituting a part of the membrane electrode structure are required to support the electrolyte membrane and contribute to the suppression of oxygen and hydrogen leakage and the maintenance of the humidity of the electrolyte membrane. From the viewpoint of process cost, a membrane electrode structure having a small number of parts and easy assembly is desired, and a membrane electrode structure capable of a lamination process is advantageous in manufacturing.

  A polymer electrolyte fuel cell is used by stacking a plurality of unit cells for the purpose of increasing power density and making the entire fuel cell compact. The number of sheets to be stacked varies depending on the required electric power. For portable power sources of general portable electric devices, several to about 10 sheets, for stationary electric and hot water supply machines for cogeneration, about 60 to 90 sheets, and for automobile applications, 250 to About 400 sheets. In order to increase the output, it is necessary to increase the number of stacks, and the cost of the unit cell greatly affects the cost of the entire fuel cell. From the viewpoint of process cost, a membrane electrode structure having a small number of parts and easy assembly is desired.

  A conventional membrane electrode structure has a structure in which the end of the membrane is sealed in order to protect the membrane or suppress hydrogen leakage (for example, Patent Document 1). After the membrane electrode structure is formed, the resin mold is sealed by wrapping the peripheral edge portion of the electrolyte membrane end using a liquid sealing material such as an elastomer by a method such as injection molding.

  In addition, another method for sealing the end portion of the electrolyte membrane different from the above-described sealing form is also known (for example, Patent Document 2). On the gasket, a reinforcing sheet having a welded layer at both ends is formed and welded to the membrane electrode structure, thereby sealing the end of the electrolyte membrane.

JP 2006-92924 A JP 2009-81118 A

  However, elastomers used in resin molds are expensive as gaskets, and in addition, it is necessary to take steps such as injection molding to place the gaskets so as to wrap around the periphery of the electrolyte membrane. Not suitable for.

  Also, the method of forming a welded layer on a film-like gasket is disadvantageous from the viewpoint of process cost because an increase in the number of parts such as a reinforcing sheet and a welded layer is unavoidable in addition to the gasket.

  As described above, the sealing of the end portion of the electrolyte membrane in the conventional membrane electrode structure has a problem that the number of parts is large, the assembly is complicated, and the cost is high, and it is a problem to solve such a problem. It was.

  As a means for solving the above problems, one embodiment of the present invention is a membrane electrode structure including an electrolyte membrane, a pair of catalyst layers sandwiching the electrolyte membrane, and a gasket disposed around the catalyst layer. The gasket has a shape that covers the end of the electrolyte membrane in a frame shape.

  Further, the gasket of the membrane electrode structure is a film made of a thermoplastic resin.

  Further, the gasket of the membrane electrode structure and the end of the electrolyte membrane are in close contact with each other through an adhesive layer or an adhesive layer.

  Further, the gasket of the membrane electrode structure is characterized in that it is formed by thermally welding two gasket layers protruding from the end of the electrolyte membrane in a range of 0.5 mm to 30 mm.

  Another aspect of the present invention is a method for producing a membrane electrode structure comprising an electrolyte membrane, a pair of catalyst layers sandwiching the electrolyte membrane, and a gasket disposed around the catalyst layer, the gasket comprising: A membrane electrode structure characterized in that the outer periphery of the first gasket layer and the second gasket layer disposed around the catalyst layer is blown to cover the end of the electrolyte membrane in a frame shape It is a manufacturing method of a body.

Still another aspect of the present invention is a method for producing a membrane electrode structure comprising an electrolyte membrane, a pair of catalyst layers sandwiching the electrolyte membrane, and a gasket disposed around the catalyst layer,
The gasket is formed so as to cover the end of the electrolyte membrane in a frame shape by heat-sealing the outer periphery of the first gasket layer and the second gasket layer disposed around the catalyst layer. This is a method for manufacturing a membrane electrode structure.

  According to the present invention, by providing a gasket larger than the width dimension of the electrolyte membrane, the exposed end portion of the electrolyte membrane is sealed in a frame shape, and a membrane electrode structure excellent in gas leakage prevention is provided. Can do.

  In addition, according to the present invention, the end portion of the electrolyte membrane that is exposed only by welding the gasket can be sealed, so that the membrane electrode structure can be manufactured easily and inexpensively.

It is a schematic sectional drawing of the single battery cell of a polymer electrolyte fuel cell. 1 is a schematic top view of a membrane electrode structure in a polymer electrolyte fuel cell according to an embodiment of the present invention. It is a schematic sectional drawing of the membrane electrode structure in the polymer electrolyte fuel cell which concerns on one Embodiment of this invention. It is a schematic sectional drawing which shows 1 process of the manufacturing method of the membrane electrode structure which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Before describing an embodiment of the present invention, a polymer electrolyte fuel cell related to the present invention will be first described with reference to FIG.
As shown in FIG. 1, a unit cell 100 of a polymer electrolyte fuel cell includes a membrane electrode structure unit 10 and a pair of separators 17 that sandwich the membrane electrode structure unit 10. The membrane electrode structure 10 includes an anode side catalyst layer 12b, an anode side gas diffusion layer 13b, and an anode side gasket layer 16b on one surface of the electrolyte membrane 11, and the cathode side catalyst layer 12a on the other surface. A cathode side gas diffusion layer 13a and a cathode side gasket layer 16a.

  That is, the unit cell 100 of the polymer electrolyte fuel cell shown in FIG. 1 includes an electrolyte membrane 11 (mainly composed of a fluorine-based electrolyte membrane or a hydrocarbon electrolyte membrane) and a catalytic substance (mainly platinum ( Pt) or another metal (for example, Ru, Rh, Mo, Cr, Co, Fe, etc.) supported between the cathode side catalyst layer 12a and the anode side catalyst layer 12b, and the cathode side catalyst layer 12a and the anode side The catalyst layer 12b is sandwiched between the cathode-side gas diffusion layer 13a and the anode-side gas diffusion layer 13b to form the cathode 14 and the anode 15, and the cathode-side gasket layer 16a and the anode-side gasket layer 16b, which have a gas sealing function, are used. A membrane electrode structure 10 is configured. The membrane electrode structure 10 is sandwiched between a pair of separators 17 to form a single battery cell 100.

  Next, the membrane electrode structure 20 and the manufacturing method thereof in the polymer electrolyte fuel cell according to the embodiment of the present invention will be described in detail with reference to FIGS. In FIG. 1, the membrane electrode structure 10 has been described as including a cathode side gas diffusion layer 13a and an anode side gas diffusion layer 13b. However, in the embodiment of the present invention described with reference to FIGS. The membrane electrode structure 20 will be described as a configuration that does not include a cathode side gas diffusion layer and an anode side gas diffusion layer.

FIG. 2 is a schematic top view of the membrane electrode structure 20 in the polymer electrolyte fuel cell according to one embodiment of the present invention, and FIG. 3 is a schematic view taken along line II of the membrane electrode structure 20. It is sectional drawing.
As shown in FIG. 3, a membrane electrode structure 20 according to an embodiment of the present invention includes an electrolyte membrane 21 and a cathode-side catalyst layer 22a disposed on one surface (upper surface in FIG. 3) of the electrolyte membrane 21. And an anode-side catalyst layer 22b disposed on the other surface (the lower surface in FIG. 3) of the electrolyte membrane 21. As shown in FIGS. 2 and 3, a gasket 26 having a frame shape by welding is provided on the periphery of the cathode side catalyst layer 22 a and the anode side catalyst layer 22 b. That is, the gasket 26 is provided so as to surround the periphery of the cathode side catalyst layer 22 a and the anode side catalyst layer 22 b of the electrolyte membrane 21 and to cover the end portion of the electrolyte membrane 21.

  The electrolyte membrane 21 is formed to be slightly larger than both the catalyst layers 22a and 22b. In the gasket 26, two gasket layers (first gasket layer and second gasket layer) arranged around the ends of both catalyst layers 22a and 22b are made one turn more than both catalyst layers 22a and 22b. The large electrolyte membrane 21 is integrally arranged so as to cover the end portion.

  In the present embodiment, the gasket 26 is integrated by welding the protruding portions of the two gasket layers arranged slightly larger than the electrolyte membrane 21 to seal the end portion of the electrolyte membrane 21. Here, the two gasket layers arranged around the ends of the catalyst layers 22a and 22b are not particularly limited as long as they are layers made of a thermoplastic resin, which will be described later. It is desirable to use a film made of resin. In the case of a film, compared to an elastomer that requires injection molding, it can be manufactured at a low cost and with a single wafer, and a membrane electrode structure can be manufactured easily and inexpensively.

  Further, it is desirable that the gasket 26 is in contact with the electrolyte membrane 21 at a portion where the two gasket layers are integrated (in the case where the two gasket layers are formed of a film exhibiting a property of being welded by melting). Further, it is desirable that the gasket 26 and the end portion of the electrolyte membrane 21 are in close contact with each other through the adhesive layer or the adhesive layer 28. Thereby, an electrolyte membrane can be supported more firmly.

  The electrolyte membrane 21 used in the present embodiment may be one generally used for solid polymer fuel cells. For example, a fluorine-based electrolyte membrane or a hydrocarbon electrolyte membrane can be suitably used, and a fluorine-based electrolyte membrane is particularly desirable.

  The cathode side catalyst layer 22a and the anode side catalyst layer 22b may also be those generally used for solid polymer fuel cells. For example, carbon black or the like in which fine particles of platinum or an alloy of platinum and other metals (for example, Ru, Rh, Mo, Cr, Co, Fe, etc.) (the average particle diameter is preferably 10 nm or less) is supported on the surface. Produced from ink in which conductive carbon fine particles (average particle size is preferably about 20 to 100 nm) and polymer solution such as perfluorosulfonic acid resin solution are uniformly mixed in a suitable solvent (such as ethanol). Can be used.

  The gasket 26 is preferably a thermoplastic resin. Examples of the thermoplastic resin include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), SPS (syndiotactic polystyrene), PTFE (polytetrafluoroethylene), PI (polyimide), and the like. In particular, a thermoplastic resin having a high elastic modulus is desirable. A fiber reinforced resin may be used as the thermoplastic resin.

The gasket 26 is disposed on the surface and end of the electrolyte membrane 21 using an adhesive layer or adhesive layer 28 in which an adhesive material or an adhesive material is impregnated between fibers of the fibrous material. The pressure-sensitive adhesive layer or the adhesive layer 28 is used as necessary.
As the pressure-sensitive adhesive material or adhesive material contained in the pressure-sensitive adhesive layer or adhesive layer 28, a material having a main chain skeleton such as a polysiloxane skeleton, a polyether skeleton, a fluoroether skeleton, or a polyolefin skeleton can be used. In addition, since the electrolyte layer 21 is disposed on the electrolyte membrane 21, the adhesive layer or the adhesive layer 28 is a solvent-free system in order to avoid swelling of the electrolyte membrane 21 due to the solvent contained in the adhesive layer or the adhesive layer 28. Is desirable.
Since the fibrous material is impregnated with the pressure-sensitive adhesive material or the adhesive material, a material having high affinity with the pressure-sensitive adhesive material or the adhesive material is desirable. Furthermore, since two gasket layers are welded together, what is welded by fusion | melting is desirable. Moreover, considering the use as a gasket, in order to prevent an electrical short circuit, since it is calculated | required that it is electrical insulation, glass fibers, such as glass paper, and an alumina fiber are desirable.

  FIG. 4 is a schematic cross-sectional view showing one step in the method for producing a membrane electrode structure according to one embodiment of the present invention. As shown in FIG. 4, first, a cathode side catalyst layer 22 a and an anode side catalyst layer 22 b are formed on the electrolyte membrane 21. In forming the cathode-side catalyst layer 22a and the anode-side catalyst layer 22b, first, an ink containing a polymer electrolyte, a catalyst substance, a carbon carrier supporting the catalyst, and a dispersion medium is prepared. The prepared catalyst ink is applied onto the electrolyte membrane 21 using a doctor blade method, a dipping method, a screen printing method, a roll coating method, a spraying method or the like, or a spraying method. The side catalyst layer 22b is formed. Further, after applying a catalyst ink on the transfer substrate using the transfer substrate and once forming a catalyst layer on the transfer substrate, the cathode side catalyst layer 22a and the anode side catalyst layer are formed on the electrolyte membrane 21 by the transfer method. 22b may be formed.

  Next, the cathode side gasket layer 26a (first gasket layer) is formed on the electrolyte membrane 21 around the cathode side catalyst layer 22a. In order to form the cathode-side gasket layer 26a, first, an adhesive material or an adhesive material is impregnated between the fibers of the fibrous material cut into a frame shape, and then disposed around the cathode-side catalyst layer 22a. The side pressure-sensitive adhesive layer or adhesive layer 28a is formed. Next, for example, a film-like cathode-side gasket layer 26a is disposed on the surface of the cathode-side adhesive layer or adhesive layer 28a. Alternatively, a fibrous material impregnated with an adhesive material or an adhesive material is disposed around the cathode side catalyst layer 22a in a state where the adhesive material or the adhesive material does not solidify, and then, for example, a film-like cathode side gasket is formed on the surface thereof. The layer 26a may be disposed.

  Further, a gasket film to be the cathode gasket layer 26a is prepared, and an adhesive layer or an adhesive layer in which an adhesive material or an adhesive material is impregnated between fibers of the fibrous material is formed on the gasket film. Next, the pressure-sensitive adhesive layer or adhesive layer-attached gasket film may be cut into a frame shape and then disposed around the cathode-side catalyst layer 22a.

  Next, in order to form the anode-side gasket layer 26b (second gasket layer), an adhesive material or an adhesive material between the fibers of the fibrous material obtained by inverting the one manufactured by the above process and cut into a frame shape After forming the anode-side pressure-sensitive adhesive layer or adhesive layer 28b impregnated with, for example, a film-like anode-side gasket layer 26b is disposed on the surface thereof. Similarly to the cathode side gasket layer 26a, the fibrous material impregnated with the adhesive material or the adhesive material is disposed around the anode side catalyst layer 22b in a state where the adhesive material or the adhesive material is not solidified, and then the surface thereof For example, a film-like anode-side gasket layer 26b may be disposed.

  Further, similarly to the cathode side gasket layer 26a, a gasket film which is a member of the anode side gasket layer 26b is prepared, and an adhesive layer or an adhesive material is impregnated between the fibers of the fibrous material on the gasket film. Alternatively, an adhesive layer is formed. Next, the pressure-sensitive adhesive layer or adhesive layer-attached gasket film may be cut into a frame shape and then disposed around the anode side catalyst layer 22b.

  Finally, the cathode side gasket layer 26a and the anode side gasket layer 26b are welded by fusing. Usually, fusing welding is carried out by cutting two stacked films with a fusing blade heated to a temperature equal to or higher than the melting temperature of the film, and welding the cut surface by contact with the fusing blade. Therefore, the fusing temperature needs to be equal to or higher than the melting points of the cathode-side gasket layer 26a and the anode-side gasket layer 26b to be used. In order to improve the mechanical strength of the fusing seal portion, it is desirable to carry out at a higher temperature for a longer time. At this time, the outer peripheral portions of the cathode side gasket layer 26 a and the anode side gasket layer 26 b, specifically, only the portion protruding from the electrolyte membrane 21 is melted without biting the end portion of the electrolyte membrane 21. Preferably, the fusing part is in close contact with the end of the electrolyte membrane 21 via an adhesive layer or an adhesive layer. Moreover, you may weld the edge part of the cathode side gasket layer 26a and the anode side gasket layer 26b by heat-sealing using a flat heating wire instead of fusing.

  Here, when the portion of the cathode side gasket layer 26a and the anode side gasket layer 26b that protrudes from the electrolyte membrane 21 is melted, the portion of the cathode side gasket layer 26a and anode side gasket layer 26b that protrudes from the electrolyte membrane 21 is: A range of 0.5 mm to 30 mm from the end of the electrolyte membrane is desirable. Thereby, the unnecessary use of a gasket can be reduced and an electrolyte can be sealed in a frame shape.

  In FIG. 4, the cathode-side adhesive layer or adhesive layer 28 a and the anode-side adhesive layer or adhesive layer 28 b are provided on the portion of the cathode-side gasket layer 26 a and the anode-side gasket layer 26 b that protrudes from the electrolyte membrane 21. However, if only the cathode side gasket layer 26a and the anode side gasket layer 26b can be welded, the protruding portion is provided with a cathode side adhesive layer or adhesive layer 28a and an anode side adhesive layer or adhesive layer 28b. It does not have to be.

  Through the above-described steps shown in FIG. 4, the cathode side adhesive layer or adhesive layer 28a and the anode side adhesive layer or adhesive layer 28b become the adhesive layer or adhesive layer 28 shown in FIG. The layer 26a and the anode side gasket layer 26b become the gasket 26 shown in FIG. 3, and the membrane electrode structure 20 shown in FIG. 3 can be formed. Further, the membrane electrode structure 20 in which the end portion of the electrolyte membrane 21 is sealed with the gasket 26 can be easily manufactured by the above steps.

  Hereinafter, the membrane electrode structure of the polymer electrolyte fuel cell of the present embodiment and the manufacturing method thereof will be described by way of specific examples. In addition, the Example mentioned later is an Example of one Embodiment of this invention, and this invention is not limited only to this Example.

  A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum-supported amount of 50% and Nafion (registered trademark, manufactured by DuPont), which is a 20% by mass polymer electrolyte solution, were mixed at a mixing ratio of 1: 1. Of water (boiling point: 100.0 ° C.) and ethylene glycol (boiling point: 197.9 ° C.) mixed solvent. The solid content ratio at this time was set to 14%. Subsequently, a dispersion treatment was performed with a planetary ball mill to prepare a catalyst ink.

The catalyst ink was applied to a transfer sheet by a doctor blade method, and the catalyst ink applied on the transfer sheet was dried in an air atmosphere at a temperature of 80 ° C. for 5 minutes to obtain a catalyst layer of an example. At this time, the thickness of the catalyst layer was adjusted so that the supported amount of the catalyst substance Pt was 0.4 mg / cm ² .

Subsequently, Nafion (registered trademark) XL (manufactured by DuPont) was used as the electrolyte membrane, and the two transfer sheets and the electrolyte were placed so that the catalyst layer punched into a 5 cm ² square shape and both surfaces of the electrolyte membrane face each other. A membrane was placed. Thereafter, the electrolyte membrane sandwiched between these two transfer sheets was heated to 130 ° C. and subjected to hot pressing for 10 minutes under pressure to obtain a structure of the electrolyte membrane and the catalyst layer.

  A central portion of a gasket film (gasket film with an adhesive layer) having an adhesive layer in which a fibrous material made of polyethylene naphthalate was impregnated with an adhesive material made of fluoroether was punched out to produce a frame-like gasket film with an adhesive layer. The opening size of this gasket film with an adhesive layer is 50 mm square. Subsequently, the produced gasket film with an adhesive layer was bonded to the two catalyst layers of the above structure. Finally, the protruding portion of the gasket film with an adhesive layer from the end of the electrolyte membrane is melted and welded using a desktop sealer (P-200 / manufactured by Fuji Impulse), so that the membrane electrode structure in the present invention is obtained. Obtained.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a polymer electrolyte fuel cell single cell or a stack in a polymer electrolyte fuel cell, particularly a fuel cell automobile or a household fuel cell.

DESCRIPTION OF SYMBOLS 100 ... Single cell 10 ... Membrane electrode structure 11 ... Electrolyte membrane 12a ... Cathode side catalyst layer 12b ... Anode side catalyst layer 13a ... Cathode side gas diffusion layer 13b ... Anode side gas diffusion layer 14 ... cathode 15 ... anode 16a ... cathode side gasket layer 16b ... anode side gasket layer 17 ... separator 20 ... membrane electrode structure 21 ... electrolyte membrane 22a ... Cathode side catalyst layer 22b ... Anode side catalyst layer 26 ... Gasket 26a ... Cathode side gasket layer 26b ... Anode side gasket layer 28 ... Adhesive layer or adhesive layer 28a ... Cathode side adhesive layer or adhesive layer

Claims (1)

A method for producing a membrane electrode structure comprising an electrolyte membrane, a pair of catalyst layers sandwiching the electrolyte membrane, and a gasket disposed around the catalyst layer ,
The gasket is formed so as to cover the end portion of the electrolyte membrane in a frame shape by fusing the outer periphery of the first gasket layer and the second gasket layer disposed around the catalyst layer. A method for producing a membrane electrode structure.

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