JP2003282093A - Electrolyte membrane-electrode junction for fuel cell and production process thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane-electrode junction in which an anode and a cathode are close to each other but isolated by a polymerelectrolyte membrane and which has a low internal resistance and a great effective reaction area. <P>SOLUTION: The electrolyte membrane-electrode junction using an electrolyte membrane containing an electrical insulator in the form of particles, fiber or fabric or an electrolyte portion having a higher modulus of elasticity than a peripheral portion thereof is produced by spraying the electrical insulator on the electrolyte membrane and joining electrodes on both surfaces thereof. Alternatively, the junction is produced by forming a composite electrolyte membrane in accordance with a method of coating the electrolyte membrane with a composite electrolyte solution containing a multifunctional monomer on a prescribed pattern to form an electrolyte layer having a high modulus of elasticity by irradiation of light and/or heating applying an electrolyte solution to the surface thereof and drying it, or the like, and joining electrodes on both surfaces thereof. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer electrolyte membrane-electrode assembly used in a polymer electrolyte fuel cell (hereinafter referred to as PEFC), and a method for producing the same.

[0002]

2. Description of the Related Art PEFC is an electrochemical conversion of chemical energy into electric energy and heat by electrochemically reacting a fuel gas such as hydrogen with an oxidant gas such as air containing oxygen. An example of an electrolyte membrane-electrode assembly (hereinafter referred to as MEA) that constitutes a power generation element of PEFC will be described with reference to FIG. An anode-side catalyst layer 94 and a cathode-side catalyst layer 96 are arranged in close contact with both surfaces of the polymer electrolyte membrane 91 that selectively transports protons. The catalyst layers 94 and 96 are layers in which carbon powder carrying a platinum-based metal catalyst as a main component is mixed with a proton conductive polymer electrolyte.

Outside these catalyst layers 94 and 96,
The MEA is configured by arranging the anode side gas diffusion layer 93 and the cathode side gas diffusion layer 95, which have gas permeability and electronic conductivity, in close contact with each other. Usually, for the gas diffusion layers 93 and 95, a conductive material having a gas-permeable property such as carbon paper or carbon cloth that is treated to be water-repellent is used.

In the PEFC using this MEA, the fuel gas or the oxidant gas is the gas diffusion layer 93 or 95.
The gas is supplied from a gas passage provided in a separator plate arranged on the outer side of, and reaches the catalyst layer 94 or 96 through the gas diffusion layer 93 or 95. In order to prevent these fuel gas and oxidant gas from leaking to the outside and mixing with each other, a gas sealing material or a gasket is placed around the gas diffusion layer 93 or 95 with a polymer electrolyte membrane interposed therebetween. There is.

In order to extract electric power from PEFC, protons must move in the polymer electrolyte membrane.
The protons are generated in the anode side catalyst layer 94 by the reaction of the following formula (1).

H ₂ → 2H ⁺ + 2e ⁻ (1)

In the cathode-side catalyst layer 96, water is produced by the reaction of the protons transferred from the anode and oxygen according to the following equation (2).

1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)

As the polymer electrolyte, a perfluorocarbon sulfonic acid having --CF ₂ --as a main chain and a side chain having a sulfonic acid group (--SO ₃ H) as a terminal functional group is introduced therein, for example, Nafion (Dupont). Company), Flem
Ion (manufactured by Asahi Glass Co., Ltd.) and Aciplex (manufactured by Asahi Kasei Co., Ltd.) are generally used. In these polymer electrolytes, the conductive paths formed by aggregating sulfonic acids and spreading in a three-dimensional network function as proton-conducting channels.

The performance of PEFC is evaluated by the potential difference (cell voltage) between the anode side gas diffusion layer 93 and the cathode side gas diffusion layer 95 when operated at the same current density. Since each constituent element of the MEA is connected in series in layers, the polymer electrolyte membrane 91, which is the layer having the highest internal resistance, is used.
Greatly influences the cell voltage, that is, the PEFC performance. Therefore, in order to reduce the internal resistance value of the MEA, that is, to increase the proton conductivity, it is necessary to use a polymer electrolyte membrane having a thinner film thickness.

There are two typical methods for manufacturing a conventional MEA. The first manufacturing method is a method in which a catalyst layer is first formed on the surface of a polymer electrolyte membrane and a gas diffusion layer is bonded to the catalyst layer. The catalyst layer is prepared by first applying a catalyst paste containing carbon powder on which a metal catalyst is supported in advance and a polymer electrolyte onto a support made of a film such as polypropylene, polyethylene terephthalate, or polytetrafluoroethylene and then drying it. Formed.

Next, the catalyst layer formed on the support is transferred to both sides of the polymer electrolyte membrane by hot pressing or hot roll. Then, the support is peeled from the catalyst layer,
A polymer electrolyte membrane with a catalyst layer is formed. In addition to the transfer method described above, there is also a method in which a catalyst paste is applied on the polymer electrolyte membrane by printing, spraying or the like and dried to form a catalyst layer on each side. By hot-pressing or hot-pressing with a hot roll, gas diffusion layers made of carbon paper, carbon cloth, etc. are attached to both surfaces of these catalyst layers to produce MEA.

In the second manufacturing method, a gas diffusion layer on which a catalyst layer has been previously formed is placed on both sides of the polymer electrolyte membrane with the catalyst layer inside, and thermocompression-bonded by a hot press or a heat roll. , A method of producing an MEA having the same structure as in the case of the first production method. The catalyst layer is formed by a method of applying a catalyst paste on the gas diffusion layer by a printing method, a spray method, or the like and then drying it.

Since the gas diffusion layer is carbon in a fibrous form, it is difficult to make its surface completely smooth, and usually a large number of small protrusions are present. Therefore, in the conventional MEA, when performing the thermocompression bonding with a hot press or a hot roll, or when assembling the unit cell, as shown in FIG.
As in 0 (b), the protrusions 99 on the gas diffusion layers 93 and 95 on the anode side and the cathode side compress and break through the catalyst layers 94 and 96 and the polymer electrolyte membrane 91,
The phenomenon that the anode and the cathode contact each other is likely to occur. Solving this problem is a very important issue for providing a PEFC that does not cause an internal short circuit.

[0015]

MEANS TO SOLVE THE PROBLEM This invention solves the above-mentioned conventional problems, and an anode and a cathode are reliably isolate | separated, internal resistance is low, and effective reaction surface area is large.
The purpose is to provide A. Further, the present invention aims to provide a method capable of easily producing such an MEA.

[0016]

A first electrolyte membrane-electrode assembly for a fuel cell according to the present invention has a polymer electrolyte membrane and a pair of electrodes arranged on both sides thereof, and the polymer electrolyte membrane comprises: At least a region sandwiched by the pair of electrodes includes a particulate, fibrous, or cloth-like electrical insulator.

The second electrolyte membrane-electrode assembly for a fuel cell according to the present invention has a polymer electrolyte membrane and a pair of electrodes arranged on both sides thereof, and the polymer electrolyte membrane has a high peripheral portion. It is characterized in that the portion of the polymer electrolyte having a higher elastic modulus than that of the molecular electrolyte is scattered or layered.

The first method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is a step of spraying or placing a particulate, fibrous or cloth-like electrical insulator on a polymer electrolyte membrane, And a step of bonding the catalyst layer side of the anode to one surface of the polymer electrolyte membrane on which the electrical insulator is sprinkled or placed and bonding the catalyst layer side of the cathode to the other surface. It is a thing.

A second method for producing an electrolyte membrane-electrode assembly for a fuel cell according to the present invention comprises a step of applying a polymer electrolyte solution on the first polymer electrolyte membrane, and a step of applying the polymer electrolyte solution on the coated surface. A step of spraying or placing a particulate, fibrous, or cloth-like electrical insulator, drying the polymer electrolyte solution having the electrical insulator sprayed or placed thereon, and a second step including the electrical insulator. A step of forming a polymer electrolyte membrane and forming a composite polymer electrolyte membrane in which the first and second polymer electrolyte membranes are bonded, and an anode catalyst layer on one surface of the composite polymer electrolyte membrane It is characterized by including the step of bonding and bonding the cathode catalyst layer to the other surface.

The third method for producing an electrolyte membrane-electrode assembly for a fuel cell according to the present invention is to disperse or place a particulate, fibrous or cloth-like electrical insulator on the first polymer electrolyte membrane. A step of forming a composite polymer electrolyte membrane by bonding a second polymer electrolyte membrane to the surface of the first polymer electrolyte membrane on the side on which the electrical insulator is sprayed or placed. It is characterized by including a step of bonding an anode catalyst layer to one surface of the composite polymer electrolyte membrane and bonding a cathode catalyst layer to the other surface.

A fourth method for producing an electrolyte membrane-electrode assembly for a fuel cell according to the present invention comprises a thermopolymerizable or photopolymerizable polyfunctional monomer and a polymer electrolyte on the first polymer electrolyte membrane. Forming a polymer electrolyte layer having a high elastic modulus in a predetermined pattern on the first polymer electrolyte membrane by applying a solution in a predetermined pattern, irradiating the applied solution with light and heating, or by heating. Step, the first
A step of applying a polymer electrolyte solution to the surface of the polymer electrolyte membrane on which the polymer electrolyte layer is formed, and a second polymer including the polymer electrolyte layer by drying the applied polymer electrolyte solution. Forming an electrolyte membrane and forming a composite polymer electrolyte membrane in which the first and second polymer electrolyte membranes are bonded, and binding a catalyst layer of an anode to one surface of the composite polymer electrolyte membrane , And a step of bonding a cathode catalyst layer to the other surface.

A fifth method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is to coat a polymer electrolyte solution on each side or simultaneously on the first polymer electrolyte membrane having a high elastic modulus, This is dried to form second and third polymer electrolyte membranes having low elastic moduli on both sides of the first polymer electrolyte membrane, and the first to third polymer electrolyte membranes are bonded to each other. Forming a composite polymer electrolyte membrane, and
The method further comprises the step of bonding an anode catalyst layer to one surface of the composite polymer electrolyte membrane and bonding a cathode catalyst layer to the other surface.

In the first to fifth methods for producing the electrolyte membrane-electrode assembly for a fuel cell of the present invention, the catalyst layer of the anode is bonded to one surface of the polymer electrolyte membrane or the composite polymer electrolyte membrane, and the other is bonded. In the step of bonding the catalyst layer of the cathode to the surface, it is preferable to bond them at least under pressure, and it is more preferable to bond them by thermocompression bonding.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolyte membrane-electrode assembly for a fuel cell according to the present invention is used for at least electrodes (gas diffusion layers) on the anode side and the cathode side in a polymer electrolyte membrane interposed between an anode and a cathode. The polymer electrolyte membrane in the sandwiched region contains an electric insulator that is harder or has a higher elastic modulus than the polymer electrolyte, or the polymer having a higher elastic modulus than the peripheral portion in the polymer electrolyte membrane. The greatest feature is that a part of the electrolyte is formed. According to the present invention, even when the polymer electrolyte membrane is compressed by the stress applied in the thermocompression bonding step during the manufacturing process, the polymer electrolyte membrane is damaged by the protrusions on the surface of the gas diffusion layer on the anode side and the cathode side. Can be suppressed. As a result, the anode and the cathode are surely separated from each other at a uniform interval close to each other, and the electrodes are reliably electrically insulated from each other. As a result, an MEA having no internal short circuit and a low internal resistance can be provided.

That is, the above-mentioned electric insulator or high-elasticity polyelectrolyte portion interposed between the anode and the cathode serves as a spacer for preventing both electrodes from approaching each other at a certain distance or less, so that the polyelectrolyte membrane is formed. Even when it is compressed and softened in the thermocompression bonding step, it is possible to prevent a short circuit due to the protrusion on the diffusion layer on the anode side or the cathode side coming into contact with the diffusion layer on the counter electrode.

Furthermore, the presence of the above spacer in the polymer electrolyte membrane makes it possible to increase the pressure applied during thermocompression bonding, and allows the softened polymer electrolyte to penetrate into the catalyst layer and the gas diffusion layer. be able to. This increases the area of the three-phase interface in which the reaction gas, the polymer electrolyte, and carbon coexist. As a result, the effective reaction surface area of MEA is increased, and the operating voltage of PEFC using the MEA can be increased.

1 (a) and 1 (b), a first embodiment of the present invention is shown.
2 shows a cross section of an example of the electrolyte membrane-electrode assembly for a fuel cell of FIG. A particulate electric insulator 12 is dispersed in the polymer electrolyte membrane 11, and the electric insulator 12 is interposed between both electrodes as a spacer between the anode 17 and the cathode 18.
Even if the protrusions 19 are present on the gas diffusion layers 13 and 15 in contact with the catalyst layers 14 and 16 on the anode side and the cathode side, the role of the electrical insulator 12 as a spacer causes the electric insulator 12 to function as shown in FIG. As shown in the figure, damage to the polymer electrolyte membrane 11 is suppressed, and an MEA is formed in which the anode 17 and the cathode 18 are separated from each other by a uniform distance.

FIG. 2 is a schematic enlarged cross section of the vicinity of the polymer electrolyte membrane and the electrode in the MEA of FIG. 1 (a). In the state before the thermocompression bonding in FIG. 2A, the polymer electrolyte membrane 21 and the carbon fibers 23 and 25 forming the gas diffusion layers on the anode side and the cathode side are located in the anode side catalyst layer and the cathode side. There are metal catalyst supporting carbon particles 24 and 26 in the side catalyst layer. Figure 2
In the state after the thermocompression bonding of (b), the polymer electrolyte membrane is heated to near the softening temperature and pressed, so that both the carbon fibers 23 and 25 and the carbon particles 24 and 26 come close to the electrical insulator 22. Alternatively, the polymer electrolyte membrane 21 is compressed and thinned until it contacts.

Since the gas diffusion layer is a material in which carbon fibers 23 and 25 such as carbon paper and carbon cloth are entangled with each other, the polymer electrolyte membrane 21 which is heated and softened penetrates into the gap between the networks. Further, since the catalyst layer is brittle, the carbon particles 24 and 26 and the carbon fibers 23 and 2 in which the layer structure is partially collapsed and dispersed during thermocompression bonding are dispersed.
5 and the polymer electrolyte membrane 21 penetrating therein are formed into a mixed layer. As a result, the area of the three-phase interface, which is necessary for the metal catalyst to act effectively, is expanded. Further, since the electric insulator 22 plays a role of a spacer for keeping the space between the anode and the cathode uniform, even when the substantial thickness of the polymer electrolyte membrane 21 for separating the both electrodes is made thin by thermocompression bonding. , Carbon fiber 2
The protrusions formed by the tips and protrusions of 3 and 25 will not penetrate or be damaged by the polymer electrolyte membrane 21.

The electrical insulator in the present invention may be dispersed in the polymer electrolyte membrane in a fibrous form other than the particulate form shown in FIG. Further, a cloth-like material may be used in a form laminated with the polymer electrolyte layer. Since the cloth-like electrical insulator has porosity, ionic conductivity is imparted by permeating the polymer electrolyte into the pores. Such an electric insulator is preferably present in the intermediate layer of the polymer electrolyte membrane as shown in FIG. As a result, the polymer electrolyte membrane and both electrodes can be bound more firmly, and both electrodes can increase the three-phase interface.

The particle size or thickness of the electrical insulator has a relationship corresponding to the film thickness of the polymer electrolyte membrane of MEA after pressure bonding. Therefore, the preferable value of the particle size or thickness of the electrical insulator is determined by the trade-off between the proton conductivity required for the polymer electrolyte membrane and the cross leak of the reaction gas. From the viewpoint of proton conductivity, 20 μm or less is preferable. Further, the cross leak between the fuel gas and the oxidant gas rapidly increases when the film thickness becomes several μm or less, and therefore from this viewpoint, 5 μm or more is preferable. Therefore, the particle size or thickness of the electrical insulator is preferably 5 to 20 μm.

In order for the electric insulator to play the role of a spacer between both electrodes, a material that is less likely to be plastically deformed during thermocompression bonding, that is, has characteristics such as higher elastic modulus and hardness at temperature during thermocompression bonding than the polymer electrolyte. It is necessary to select a material having As the material of the electric insulator, glass, ceramics, crystals of inorganic or organic substances, minerals such as mica, resin, rubber, ebonite, plant fiber and the like can be used. Also, electrical conductors such as metal and carbon coated with electrical insulators, as well as proton conductive resins with a high elastic modulus by cross-linking, cross-linking cation exchange resins with proton conductivity, inorganic porous It is also possible to use an electric insulator having a proton-conducting channel, such as one in which a polyelectrolyte is impregnated in a conductive substance.

FIG. 3 is a schematic enlarged cross section of the vicinity of the vicinity of the polymer electrolyte membrane and the electrode in one example of the second electrolyte membrane-electrode assembly for a fuel cell of the present invention. Figure 3
In the state before (a) thermocompression bonding, the polymer electrolyte membrane 31 and
Between the carbon fibers 33 and 35 forming the gas diffusion layers on the anode side and the cathode side, the metal catalyst-supporting carbon particles 34 and 36 forming the anode side catalyst layer and the cathode side catalyst layer are present. In the state after thermocompression bonding in FIG. 3B, the polymer electrolyte membrane 31 is thinned to a uniform thickness to a thickness substantially equal to the thickness of the polymer electrolyte portion 32 having a high elastic modulus. Then, the carbon fibers 33 and 35 are close to each other until they almost come into contact with the polymer electrolyte portion 32 having a high elastic modulus.

Similar to the case of FIG. 2B, in FIG. 3B, the carbon fibers 33 and 35 and the polymer electrolyte membrane 31 in which the carbon particles 34 and 36 are softened by thermocompression bonding are
The three-phase interface is formed to increase the effective reaction surface area of MEA. In the above MEA in which the polymer electrolyte portion having a higher elastic modulus than the surroundings is formed in the polymer electrolyte membrane, the spacer portion can also be made to have proton conductivity, so that the operating voltage of PEFC using this can be increased. It becomes possible.

The above-mentioned high elastic modulus portion can be scattered in the polymer electrolyte membrane or formed into a layer. In particular, in order to more firmly bond the polymer electrolyte membrane and both electrodes and to increase the three-phase interface in both electrodes, these high elastic modulus portions are present in the intermediate layer of the polymer electrolyte membrane. It is preferable. For example, a high elastic polymer electrolyte cross-linked with a polymerizable polyfunctional monomer is interposed in a layer form in an intermediate layer of two low elastic modulus polymer electrolyte membranes by a solvent casting method, On a polymer electrolyte membrane formed by interspersing molecular electrolyte layers,
A polymer electrolyte membrane formed by the solvent casting method,
Alternatively, it is preferable to use a composite polymer electrolyte membrane such as one in which a polymer electrolyte membrane having a high elastic modulus formed by a heat extrusion method is interposed between two polymer electrolyte membranes formed by a solvent casting method.

The patterning of the highly elastic polyelectrolyte layer is conducted by interspersing the polyelectrolyte membrane in any form such as regular or irregular dots, islands, stripes, or meshes. Good. The patterning of the high-elasticity polyelectrolyte layer also includes forming a sheet-like layer having no holes. Since this highly elastic polymer electrolyte layer has proton conductivity, the proton conductivity of MEA is not impaired even when the sheet-like layer is used.

The high-elasticity polyelectrolyte layer in the above-mentioned polyelectrolyte membrane comprises, for example, a polymerizable polyfunctional monomer and a polyelectrolyte in an organic solvent, water or a mixed solvent thereof,
Formed by applying a solution dissolved at a concentration of 0.1 to 10% by weight and a solution of 5 to 20% by weight, respectively, on a low elastic modulus polymer electrolyte membrane, irradiating it with heat or ultraviolet rays, and crosslinking polymerizing. be able to. As the heat-polymerizable or photopolymerizable polyfunctional monomer, that is, a crosslinkable monomer, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, propylene ethylene glycol dimethacrylate, 1,4 -Butanediol dimethacrylate, 1,3
-Butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, trimethylolpropane trimethacrylate,
Glycerin dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, triethylene glycol diacrylate, propylene ethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, dimethylol tricyclo Decane diacrylate, trimethylol propane triacrylate, pentaerythritol triacrylate, neopentyl glycol diacrylate hydroxypivalate, polytetramethylene glycol diacrylate, and ditrimethylol propane tetraacrylate can be used.

The first method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is to disperse a particulate or fibrous electrical insulator on a polymer electrolyte membrane, or a cloth-shaped electrical insulator. It is characterized in that it is mounted, and one electrode is coupled to the dispersion surface or the mounting surface, and the other electrode is coupled to the other surface. This manufacturing method has an advantage that an MEA having an electric insulator serving as a spacer interposed between an anode and a cathode can be manufactured by an extremely simple process.

The manufacturing process of MEA by this manufacturing method is illustrated in FIG. However, the protrusions on the gas diffusion layer are omitted in the drawing. First, as shown in FIG. 4A, a particulate electric insulator 42 is uniformly dispersed on the polymer electrolyte membrane 41. Then, on both surfaces of the polymer electrolyte membrane 41, an anode side catalyst layer 44 and a cathode side catalyst layer 46 are formed by a transfer method.
To form a polymer electrolyte membrane with a catalyst layer. Next, the anode-side gas diffusion layer 43 and the cathode-side gas diffusion layer 45 are pressure-bonded and bonded to both surfaces of the catalyst layer-attached polymer electrolyte membrane, and as shown in FIG. A MEA having a spacer interposed between the anode and the cathode is produced. In this pressure bonding step, it is preferable to perform thermocompression bonding with a hot roll or hot press.

Dispersion of the electric insulator preferably prevents the electric insulator from being dispersed in a region other than the region in contact with the gas diffusion layer. For that purpose, a metal mask having a window having the same size as the gas diffusion layer is placed. A method of dispersing an electric insulator on the polymer electrolyte membrane is preferable. If there is a large amount of electric insulator in a region other than the region in contact with the gas diffusion layer, that is, in the peripheral portion of the polymer electrolyte membrane, it will be rather an obstacle when pressing a gasket to that portion in a later step.

The second method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is to coat a polymer electrolyte solution on a polymer electrolyte membrane, and coat the coated surface with a particulate or fibrous electrical insulator. Or by placing a cloth-like electric insulator, drying the coating solution to form a composite polymer electrolyte membrane, and bonding the anode and cathode to both surfaces of the composite polymer electrolyte membrane. is there.

The manufacturing process of the MEA by this manufacturing method is illustrated in FIG. However, the protrusions on the gas diffusion layer are omitted in the drawing. First, as shown in FIG. 5A, the first polymer electrolyte membrane 57a is formed on the support 59 by a casting method.
To form. Next, the polymer electrolyte solution 58 is applied onto the polymer electrolyte membrane 57a as shown in FIG. 5 (b). Next, as shown in FIG. 5C, before the applied polymer electrolyte solution 58 dries, a particulate electric insulator 5 is applied to the applied surface.
Spray 2 evenly and allow to settle. Next, by drying the applied polymer electrolyte solution 58 and removing the solvent,
As shown in FIG. 5D, the second polymer electrolyte membrane 57b is formed on the first polymer electrolyte membrane 57a. This allows
The composite polymer electrolyte membrane 51 having the electric insulator 52 dispersed therein is formed in the intermediate layer.

An anode side catalyst layer 54 and a cathode side catalyst layer 56 are formed on both surfaces of this composite polymer electrolyte membrane 51 in the same manner as in FIG. 4 to produce a polymer electrolyte membrane with a catalyst layer. , The anode side gas diffusion layer 53 on both sides thereof
And, the cathode side gas diffusion layer 55 is pressure-bonded and combined,
As shown in FIG. 5E, the MEA in which the particulate electrical insulator 52 is interposed between the anode and the cathode as a spacer is manufactured. In the above-mentioned pressure-bonding step, it is preferable to perform heat-pressure bonding with a hot roll or hot press.

The third method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is to disperse a particulate or fibrous electrical insulator on the polymer electrolyte membrane, or to apply a cloth-shaped electrical insulator. Place it on the side of the polymer electrolyte membrane on which the electrical insulator is sprayed or placed to form another composite polymer electrolyte membrane by bonding another polymer electrolyte membrane to both sides of the composite polymer electrolyte membrane. , A method of combining an anode and a cathode.

The manufacturing process of the MEA by this manufacturing method is illustrated in FIG. However, the protrusions on the gas diffusion layer are omitted in the drawing. First, as shown in FIG. 6A, the first polymer electrolyte membrane 67 is cast on the support 69a by a casting method.
a is formed. Next, as shown in FIG. 6B, a particulate electric insulator is sprinkled on the first polymer electrolyte membrane 67a. Then, as shown in FIG. 6C, the second polymer electrolyte formed on the other support 69b by the casting method on the surface of the first polymer electrolyte membrane 67a on the side where the electric insulator is sprayed. The films 67b are superposed and the two are pressure-bonded by the heat roller 68.

As a result, as shown in FIG. 6 (d), the first and second polymer electrolyte membranes 67a and 67b are bonded to each other, and the electric insulator 52 is dispersed and present in the intermediate layer. 61 is formed. An anode side catalyst layer 64 and a cathode side catalyst layer 66 are formed on both surfaces of the composite polymer electrolyte membrane 61 by the same method as in the case of FIG.
A polymer electrolyte membrane with a catalyst layer is produced, and an anode side gas diffusion layer 63 and a cathode side gas diffusion layer 65 are formed on both sides of the polymer electrolyte membrane.
6A and 6B are bonded by pressure bonding to prepare an MEA in which the particulate electrical insulator 62 is interposed as a spacer between the anode and the cathode, as shown in FIG.

As the electric insulator used in the first to third manufacturing methods of the present invention, various forms such as cloth can be used, but it can be easily dispersed on the polymer electrolyte membrane. It is particularly preferable to use a particulate or fibrous material.

The fourth method for producing an electrolyte membrane-electrode assembly for a fuel cell according to the present invention is to provide a polymer electrolyte solution containing a thermopolymerizable or photopolymerizable polyfunctional monomer on a polymer electrolyte membrane in a predetermined manner. It is applied in a pattern, the polyfunctional monomer is cured to form a polymer electrolyte layer in a predetermined pattern, a polymer electrolyte solution is applied thereon and dried to form a composite polymer electrolyte membrane. This is a method of bonding an anode and a cathode to both surfaces of this composite polymer electrolyte membrane.

FIG. 7 illustrates the manufacturing process of MEA by this manufacturing method. However, the protrusions on the gas diffusion layer are omitted in the drawing. First, as shown in FIG. 7A, the first polymer electrolyte membrane 77a is cast on the support 79 by a casting method.
To form. Next, as shown in FIG. 7B, a polymer electrolyte solution 78 containing a polyfunctional monomer is applied on the first polymer electrolyte membrane 77a in a pattern of islands.
Next, as shown in FIG. 7C, the surface coated with the polyelectrolyte solution 78 containing the polyfunctional monomer is irradiated with ultraviolet rays to be cured, and the polyelectrolyte portions 72 having a high elastic modulus are scattered in an island shape. The pattern is formed.

Next, as shown in FIG. 7D, a polymer electrolyte solution 70 is applied to the surface of the first polymer electrolyte membrane 77a where the high elastic modulus polymer electrolyte portion 72 is formed, and this is applied. After drying, the second polymer electrolyte membrane 77b is formed.
As a result, as shown in FIG. 7E, the composite polymer electrolyte membrane 71 in which the polymer electrolyte portion 72 having a high elastic modulus is scattered in the intermediate layer is formed. The anode side catalyst layer 74 is formed on both surfaces of the composite polymer electrolyte membrane 71 by the same method as in the case of FIG.
And the cathode side catalyst layer 76 is formed to produce a polymer electrolyte membrane with a catalyst layer, and the anode side gas diffusion layer 73 and the cathode side gas diffusion layer 75 are pressure-bonded to both surfaces thereof to be bonded, as shown in FIG. , The cured polyelectrolyte layer intervenes as a spacer between the anode and the cathode.
Make EA.

The patterning of the cured polymer electrolyte layer may be regular or irregular dot-like, island-like, stripe-like, or mesh-like. Also,
Since this polymer electrolyte layer has proton conductivity, it may be patterned into a sheet having no holes. In the above-mentioned pressure-bonding step, it is preferable to perform heat-pressure bonding with a hot roll or hot press.

The fifth method for producing an electrolyte membrane-electrode assembly for a fuel cell of the present invention is a solvent casting method in which a polymer electrolyte solution is applied to both surfaces of a first polymer electrolyte membrane having a high elastic modulus and dried. The second and third polymer electrolyte membranes having a low elastic modulus are formed by the above method, and the anode and the cathode are bonded to both surfaces of the composite polymer electrolyte membrane having the three-layer structure.

The manufacturing process of the MEA by this manufacturing method is illustrated in FIG. However, the protrusions on the gas diffusion layer are omitted in the drawing. First, as shown in FIG. 8A, a polymer electrolyte having a concentration of about 5 to 20% by weight is formed on one surface of the first polymer electrolyte membrane 87 having a high orientation and a high elastic modulus by a heat extrusion method or the like. Apply solution 88a. Next, this is dried to form a second polymer electrolyte membrane 80a having a low elastic modulus on the first polymer electrolyte membrane 87 as shown in FIG. 8B. Next, as shown in FIG. 8C, the same polymer electrolyte solution 88b as 88a is applied to the other surface of the first polymer electrolyte membrane 87, and this is dried, as shown in FIG. 8D. Then, the third polymer electrolyte membrane 80b having a low elastic modulus is formed. In this way, the composite polymer electrolyte membrane 81 in which the polymer electrolyte membranes 80a and 80b having a low elastic modulus are combined is formed on both sides of the polymer electrolyte membrane 87 having a high elastic modulus.

An anode-side catalyst layer 84 and a cathode-side catalyst layer 86 are formed on both surfaces of this composite polymer electrolyte membrane 81 by the same method as in FIG. 4 to prepare a polymer electrolyte membrane with a catalyst layer. , The anode side gas diffusion layer 83 on both sides thereof
And the cathode side gas diffusion layer 85 is pressure-bonded and combined,
As shown in FIG. 8E, a MEA in which a polymer electrolyte membrane having a high elastic modulus is interposed as a spacer between an anode and a cathode.
To make.

In the above manufacturing process, the second and third
However, instead of this, the polymer electrolyte solution is applied to both surfaces of the first polymer electrolyte membrane, and these are dried to simultaneously form the second polymer electrolyte membrane.
Also, a method of forming the third polymer electrolyte membrane can be adopted. As a method of easily applying the polymer electrolyte solution on the first polymer electrolyte membrane, there are a printing method and a die coating method. In the above-mentioned pressure-bonding step, it is preferable to perform heat-pressure bonding with a hot roll or hot press.

In each of the above manufacturing processes, a gas diffusion layer is pressure-bonded onto a catalyst layer which is previously formed on a polymer electrolyte membrane by a transfer method to form an anode and a cathode, and at the same time an MEA is formed. However, in the production method of the present invention, instead of this, a method of forming an MEA by pressure-bonding an anode or a cathode having a catalyst layer formed on a gas diffusion layer to both sides of a polymer electrolyte membrane may be adopted. it can. It is also possible to adopt a method in which the gas diffusion layer is pressure-bonded onto the catalyst layer formed by applying the catalyst paste to the polymer electrolyte membrane by printing or the like to form the MEA. In the pressure bonding step in each of the above manufacturing processes, a hot press device, a hot roll device, or the like can be used. The pressure during thermocompression bonding is 20 to 50 kg / cm ² , and the temperature is 120 to 16
The temperature is preferably 0 ° C.

[0057]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 An MEA was manufactured by the manufacturing process shown in FIG. Polymer electrolyte (Flemion manufactured by Asahi Glass Co., Ltd.) 30 wt% ethanol solution (30 ml) was placed in a petri dish having a diameter of 20 cm, left at room temperature for one day and then dried at 130 ° C. for 30 minutes, and polymer having a thickness of 30 μm was cast. The electrolyte membrane 41 was produced. A metal mask with a 6 cm × 6 cm square window was placed on this polymer electrolyte membrane 41, and this was covered with a hollow hemispherical container made of acrylic resin and having a diameter of about 50 cm. As the insulator 42, a small amount of epoxy resin particles having a diameter of 20 μm (manufactured by Sekisui Chemical Co., Ltd .: Micropearl) was sprayed together with dry nitrogen gas. As a result, the electrical insulator 42 was evenly dispersed on the polymer electrolyte membrane 41.

Then, the catalyst paste was applied on a support of a polypropylene film (manufactured by Toray Industries, Inc.) having a thickness of 50 μm by a bar coater, dried at room temperature, and then 6 cm × 6 c.
It cut out in the square of m, and produced the catalyst layer with a support body.
The platinum content of this catalyst layer was about 0.2 mg / cm ² . The catalyst paste is carbon powder carrying a platinum catalyst.
It was prepared by adding 15 cc of distilled water to 0 g, and adding 25.0 g of a 9 wt% ethanol solution of a polymer electrolyte (Flemion, manufactured by Asahi Glass Co., Ltd.), and stirring the mixture with a stirrer for 1 hour while applying ultrasonic vibration. .

Then, on the surface of the polymer electrolyte membrane 41 in the area where the electric insulator 42 is sprayed and on the back surface of the area,
The catalyst layer side of the catalyst layer with the support was superposed on each other.
The outside is sandwiched between a polytetrafluoroethylene sheet and a heat-resistant rubber sheet, and a pressure of 40k is applied by a hot press machine.
The catalyst layer 44 was pressure-bonded under the conditions of g / cm ² and temperature of 135 ° C.
After transferring 46 and 46 to both sides of the polymer electrolyte membrane 41,
The support was peeled off.

Gas diffusion layers 43 and 45 are formed on both sides of the polymer electrolyte membrane with a catalyst layer thus produced, respectively.
Was placed and sandwiched between polytetrafluoroethylene sheets, and this was press-bonded at 135 ° C. by a hot press machine to fabricate an MEA. The distance between the anode-side catalyst layer 44 and the cathode-side catalyst layer 46 of the manufactured MEA is 18 to 20 μm,
The intervals were also uniform. Gas diffusion layers 43 and 45
After immersing carbon paper (manufactured by Toray Industries, Inc.) in a fluororesin dispersion liquid (ND-1 manufactured by Daikin Industries, Ltd.), 3
It was made by firing at 00 ° C.

Comparative Example 1 M was prepared in the same manner as in Example 1 except that the epoxy resin particles were not sprayed onto the polymer electrolyte membrane.
EA was made. However, in order to prevent contact between the anode and the cathode due to breakage of the polymer electrolyte membrane, the pressure applied in the crimping process by the hot press device is 3 times as much as that in the case of Example 1.
0% lower. The distance between the anode-side catalyst layer and the cathode-side catalyst layer of the produced MEA was 24-28 μm.

Example 2 An MEA was manufactured by the manufacturing process shown in FIG. Polymer electrolyte (Asahi Glass Co., Ltd.)
Product: Flemion) 7 wt% ethanol solution was applied to a support 59 made of a polypropylene film (manufactured by Toray Industries, Inc.) having a film thickness of 50 μm by a mini die coater, left at room temperature, and then dried at 130 ° C. for 10 minutes. Thickness 5μ
m of the polymer electrolyte membrane 57a was formed. Then, on the polymer electrolyte membrane 57a, as a polymer electrolyte solution 58, a polymer electrolyte (Asahi Glass Co., Ltd .: Flemion) 7% by weight ethanol solution was applied by a mini die coater, and the application was performed immediately after the application. The same electrical insulator 52 as in Example 1 was sprayed evenly. Then, after leaving it at room temperature, 130
By drying at 30 ° C. for 30 minutes, a composite polymer electrolyte membrane 51 having a thickness of 30 μm was produced.

Then, in the same manner as in Example 1, the catalyst layer 5
4 and 56 were transferred and formed on both surfaces of the composite polymer electrolyte membrane 51, the gas diffusion layers 53 and 55 were arranged outside the catalyst layers 54 and 56, and pressure-bonded to produce MEA. The distance between the anode-side catalyst layer 54 and the cathode-side catalyst layer 56 was 18 to 20 μm, and the distance was also uniform.

Example 3 An MEA was manufactured by the manufacturing process shown in FIG. The composite polymer electrolyte solution 78 was screen-printed on the polymer electrolyte membrane 77a having a thickness of 5 μm formed on the support 79 by the same method as in Example 2 using a printing plate having a 1 mm square mosaic pattern. As the composite polymer electrolyte solution 78, a polymer electrolyte (Flemion manufactured by Asahi Glass Co., Ltd.), a cross-linkable monomer (1,6-hexanediol diacrylate), and an ultraviolet polymerization initiator (manufactured by Ciba-Gaigi Co., Ltd .: Darocur 1) are used.
173) at 9% by weight, 2% by weight, and 0.
An ethanol solution containing a concentration of 1% by weight was used.

After the composite polymer electrolyte solution 78 printed on the polymer electrolyte membrane 77a is dried at room temperature, the printed surface is irradiated with ultraviolet rays of 100 mW / cm ² for 60 seconds by a high pressure mercury lamp, and then at 130 ° C. And dried for 30 minutes. As a result, the monomers in the printed composite polymer electrolyte solution 78 were cross-linked and polymerized to form a cured high elastic modulus polymer electrolyte portion 72. Next, the polymer electrolyte membrane 7 on the side where the high-elasticity polymer electrolyte portion 72 is patterned
On the surface of 7a, a polymer electrolyte (made by Asahi Glass Co., Ltd .: Flem
Ion) 7 wt% ethanol solution was applied with a mini die coater, left at room temperature, and dried at 130 ° C. for 30 minutes to prepare a composite polymer electrolyte membrane 71 having a thickness of 30 μm.

Then, in the same manner as in Example 1, the catalyst layer 7
4 and 76 were respectively transferred and formed on both surfaces of the composite polymer electrolyte membrane 71, and using this polymer electrolyte membrane with a catalyst layer, an MEA was produced in the same manner as in Example 1. The distance between the anode side catalyst layer 74 and the cathode side catalyst layer 76 is 2
It was 0 to 22 μm. The intervals were also uniform.

A PEFC unit cell was constructed by using each MEA produced in Example 1, Comparative Example 1, Example 2, and Example 3. FIG. 9 shows a sectional view of a unit cell using the MEA of Example 1 as a representative example of these. First, ME
The gaskets 100 and 101 were thermocompression-bonded to both sides of the peripheral edge of the polymer electrolyte membrane 41 in A to form MEA with a gasket. Gas diffusion layer 43 or 45
A separator plate 104 or 105 having an anode gas flow path 102 or a cathode gas flow path 103 was attached to the outside of the. Further, cooling water flow paths 106 and 107 are arranged outside the separator plates 104 and 105, respectively.

The temperature of each of the cells thus produced was maintained at 75 ° C., and hydrogen gas heated and humidified so that the dew point was 70 ° C. on the anode side and the dew point of 30 ° C. on the cathode side. The heated and humidified air was supplied to each.
These single cells were operated under the conditions of hydrogen utilization rate of 70% and oxygen utilization rate of 40%, and the relationship between discharge current density and cell voltage was examined. The result is shown in FIG.

It can be seen from FIG. 11 that Examples 1 to 3 all show the same good battery characteristics, even though they were operated under relatively dry conditions. On the other hand, Comparative Example 1 showed a lower cell voltage as compared with Examples 1 to 3.
From the cross-sectional investigation of the MEA, in Comparative Example 1, it was confirmed that the distance between the anode and the cathode was 24 to 28 μm, which was larger than that in Examples 1 to 3, and the thickness of the electrolyte membrane was thick. As a result, it is considered that in Comparative Example 1, the internal resistance increased and the cell voltage decreased. Further, in Comparative Example 1, there is a portion where the distance between the electrodes is as extremely thin as 10 μm, and depending on how to balance the pressing force during thermocompression bonding,
It was found that there is a risk that the polymer electrolyte membrane will be broken and the anode and the cathode will come into contact with each other.

[0071]

According to the present invention, an MEA having a low internal resistance and a large effective reaction surface area can be provided without causing a short circuit between electrodes. It becomes possible to construct a highly reliable high performance fuel cell using this MEA.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an electrolyte membrane-electrode assembly according to the present invention.

FIG. 2 is an enlarged vertical sectional view of a main part of an electrolyte membrane-electrode assembly according to the present invention.

FIG. 3 is an enlarged vertical sectional view of a main part of another electrolyte membrane-electrode assembly according to the present invention.

FIG. 4 is a vertical cross-sectional view illustrating the steps of manufacturing an electrolyte membrane-electrode assembly according to the first manufacturing method of the present invention.

FIG. 5 is a vertical cross-sectional view illustrating the steps of manufacturing an electrolyte membrane-electrode assembly according to the second manufacturing method of the present invention.

FIG. 6 is a vertical cross-sectional view illustrating the steps of manufacturing an electrolyte membrane-electrode assembly according to the third manufacturing method of the present invention.

FIG. 7 is a vertical cross-sectional view illustrating the steps of manufacturing an electrolyte membrane-electrode assembly according to the fourth manufacturing method of the present invention.

FIG. 8 is a vertical cross-sectional view illustrating the steps of manufacturing an electrolyte membrane-electrode assembly according to the fifth manufacturing method of the present invention.

FIG. 9 is a vertical sectional view of a unit cell of a fuel cell according to an example of the present invention.

FIG. 10 is a vertical cross-sectional view of a conventional electrolyte membrane-electrode assembly.

FIG. 11 is a diagram showing operating characteristics of the unit cells of the example of the present invention and the comparative example.

[Explanation of symbols]

11, 21, 31, 41, 51, 57, 67, 77, 8
1, 90 Polymer electrolyte membrane 12, 22, 42, 52, 62 Electrical insulator 13, 15, 43, 45, 53, 55, 63, 65, 7
3, 75, 83, 85, 93, 95 Gas diffusion layers 14, 16, 44, 46, 54, 56, 64, 66,
74, 76, 84, 86, 94, 96 Catalyst layer 17 Anode 18 Cathode 19, 99 Protrusions 23, 25, 33, 35 Carbon fibers 24, 26 34, 46 Carbon particles 32, 72 Polymer electrolyte part having high elastic modulus 58, 88 polymer electrolyte solution 59, 69, 79 support 51, 61, 71, 81 composite polymer electrolyte membrane 68 heat roller 78 composite polymer electrolyte solution 87 polymer electrolyte membrane 100, 101 with high elastic modulus gasket 102, 103 gas flow paths 104, 105 separator plates 106, 107 cooling water flow paths

Claims (7)

[Claims] 1. A polymer electrolyte membrane and a pair of electrodes arranged on both sides thereof, and at least a region of the polymer electrolyte membrane sandwiched between the pair of electrodes is in the form of particles, fibers, or a cloth. Membrane-electrode assembly for a fuel cell, characterized in that the electrolyte membrane-shaped electrode insulation is included. 2. A polymer electrolyte membrane and a pair of electrodes arranged on both sides thereof, wherein a portion of the polymer electrolyte having a higher elastic modulus than that of the polymer electrolyte in the peripheral portion is present in the polymer electrolyte membrane. An electrolyte membrane-electrode assembly for a fuel cell, characterized by being scattered or layered. 3. A step of spraying or placing a particulate, fibrous, or cloth-like electrical insulator on the polymer electrolyte membrane,
And a step of bonding the catalyst layer of the anode to one surface of the polymer electrolyte membrane on which the electrical insulator is sprinkled or placed, and bonding the catalyst layer of the cathode to the other surface. For manufacturing electrolyte membrane-electrode assembly for automobile. 4. A step of applying a polyelectrolyte solution on a first polyelectrolyte membrane, and a particulate, fibrous, or cloth-like electrical insulator is sprayed or placed on the application surface of the polyelectrolyte solution. The step of placing, the polymer electrolyte solution sprayed or placed with the electrical insulator is dried to form a second polymer electrolyte membrane containing the electrical insulator, and the first and second polymer electrolytes And a step of forming a composite polymer electrolyte membrane in which the membranes are bonded, and a step of bonding an anode catalyst layer to one surface of the composite polymer electrolyte membrane and a cathode catalyst layer to the other surface. A method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising: 5. A step of spraying or placing a particulate, fibrous, or cloth-like electrical insulator on the first polymer electrolyte membrane, or spraying or mounting the electrical insulator of the first polymer electrolyte membrane. A step of forming a composite polymer electrolyte membrane by bonding a second polymer electrolyte membrane to the surface on which it is placed, and combining a catalyst layer of the anode with one surface of the composite polymer electrolyte membrane, A method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising the step of bonding a cathode catalyst layer to the other surface. 6. A step of applying a solution containing a thermopolymerizable or photopolymerizable polyfunctional monomer and a polymer electrolyte in a predetermined pattern on the first polymer electrolyte membrane, and irradiating the applied solution with light. And heating, or a step of forming a polymer electrolyte layer having a high elastic modulus in a predetermined pattern on the first polymer electrolyte membrane by heating, or forming the polymer electrolyte layer of the first polymer electrolyte membrane The step of applying a polyelectrolyte solution to the surface on the side where the polyelectrolyte solution is applied, the applied polyelectrolyte solution is dried to form a second polyelectrolyte membrane including the polyelectrolyte layer, and the first and second Forming a composite polymer electrolyte membrane in which the polymer electrolyte membrane is bonded, and bonding the catalyst layer of the anode to one surface of the composite polymer electrolyte membrane and the catalyst layer of the cathode to the other surface Having a process A method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising: 7. A polymer electrolyte solution is applied onto one surface or both surfaces of the first polymer electrolyte membrane having a high elastic modulus at the same time and dried, and the polymer electrolyte solution is dried to form each of both surfaces of the first polymer electrolyte membrane. A second and a third polymer electrolyte membrane having a low elastic modulus to form a composite polymer electrolyte membrane in which the first to third polymer electrolyte membranes are bonded to each other, and the composite polymer electrolyte A method for producing an electrolyte membrane-electrode assembly for a fuel cell, comprising the step of bonding an anode catalyst layer to one surface of the membrane and bonding a cathode catalyst layer to the other surface.