JPH0997619A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight, economical fuel cell by using a gasket realizing high sealing capability at low fastening pressure. SOLUTION: A gasket 31 is arranged in the periphery of a unit cell comprising a positive electrode 12, an electrolyte plate 11, and a negative electrode 12, and the unit cells are stacked through a separator plate 2 to form a fuel cell. The gasket 31 is constituted by bonding a closed-cell spongy layer 33 to at least the one side of the separator plate 2 through an adhesive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell using pure hydrogen as a fuel or a reducing agent such as reformed hydrogen from methanol and fossil fuel and using air or oxygen as an oxidant, and particularly to a solid-state fuel cell. The present invention relates to a gasket for a polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art For example, a solid polymer electrolyte fuel cell is
It is known that when a cation exchange membrane which is a proton conductor is used as a solid polymer electrolyte and hydrogen is introduced as a fuel and oxygen is introduced as an oxidant, the following (formula 1) and (formula 2) reactions occur. ing.

[0003]

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[0004]

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At the negative electrode, hydrogen dissociates into protons and electrons. Protons move in the cation exchange membrane toward the positive electrode, and electrons move in a cell laminated in series with a conductive separator plate and an external circuit to reach the positive electrode, at which time power is generated. On the other hand, in the positive electrode, the protons that have moved in the cation exchange membrane, the electrons that have moved in the external circuit, and oxygen introduced from the outside react to generate water. Since this reaction is exothermic, hydrogen, oxygen, and electricity generate electricity, water, and heat as a whole.

The solid polymer electrolyte fuel cell is greatly different from other fuel cells in that the electrolyte is composed of an ion exchange membrane which is a solid polymer. A perfluorocarbon sulfonic acid membrane (Nafion, trade name, manufactured by DuPont, USA) is used for this ion exchange membrane, but the membrane must be sufficiently hydrated in order for this membrane to exhibit sufficient proton conductivity. There is. As a method for hydrating the ion exchange membrane, for example, J. Electrochem. So
c. 135 (1988) page 2209, a method is adopted in which the reaction gas is passed through a humidifier to introduce water vapor into the cell to prevent the ion exchange membrane from drying. As a method of sealing each cell, for example, J. Power Sources, 29 (1990) 3
As described on page 67, the area of the ion exchange membrane is made larger than the electrode area, and the peripheral portion of the ion exchange membrane which is not joined to the electrodes is sandwiched by upper and lower gaskets.

As a material for the gasket, a glass fiber cloth or fluororubber coated with polytetrafluoroethylene (trade name: Teflon manufactured by DuPont, USA) is used.

In US Pat. No. 4,826,741, silicone rubber and fluororubber are used.
In this structure, the gasket must absorb the thickness of the ion exchange membrane of about 50 to 200 μm and perform insulation and gas sealing between the adjacent separator plates. Therefore, it is necessary to perform fine processing by increasing the cell clamping pressure to crush the gasket, or to reduce the thickness of the portion of the gasket that contacts the ion exchange membrane by the thickness of the membrane.

[0009]

However, in the above-mentioned conventional method, as the number of laminated cells increases, the thickness of the ion-exchange membrane to be absorbed is integrated and becomes large, so that the absorption cannot be completed or a very large tightening pressure is applied. And other housings such as end plates and bolts and nuts become large in order to secure strength. In addition, there is a drawback that sufficient gas sealability cannot be secured due to variations in the thickness of the gasket, the ion exchange membrane, and the separator plate. Furthermore, since the thickness of the ion exchange membrane changes with the change of the water content, the conventional gasket material has a large stress relaxation property, so there is a risk that the initially secured sealing property will deteriorate during operation. Was.

The present invention solves the above-mentioned problems of the prior art. By using a gasket that exhibits a high sealing property at a low tightening pressure, a lighter and more economical fuel cell, particularly a solid polymer electrolyte fuel cell, is provided. The purpose is to provide.

[0011]

In order to achieve this object, according to the present invention, a gasket is placed around the periphery of a unit cell composed of a positive electrode, an electrolyte plate and a negative electrode, and a separator plate is interposed between the gaskets. In a fuel cell, a gasket has a structure in which a sponge layer of closed cells is adhered to at least one surface of a separator plate via an adhesive layer.

[0012]

In this structure, the closed-cell sponge layer absorbs the thickness of the ion exchange membrane by compressing the bubbles. In addition, since individual independent air bubbles are compressed against partial unevenness, the swell and roughness of the separator plate can be absorbed. Furthermore, since the closed air bubbles are compressed, stress relaxation is small, and since the sponge layer is adhered to the separator plate, the sponge layer is adhered to the substrate even when high-pressure gas is used inside. Does not escape to the outside.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is an external view of a laminated cell of a general solid polymer electrolyte fuel cell. Separator plates 2 made of a conductive material such as glassy carbon and insulating gaskets 1 are alternately stacked, and a copper current collector plate 3 is adhered to the outermost separator plate. This laminated body is sandwiched by stainless steel end plates 5 with an insulating plate 4 interposed therebetween, and the end plates are fastened with bolts and nuts.

Of course, the material of each part is not limited to the above materials as long as the conditions such as conductivity, insulation, heat resistance and gas permeability do not adversely affect the battery performance.

FIG. 4 is a view showing a cross-sectional view of a general laminated battery internal cell. Electrodes 12 are bonded to both surfaces of the central ion exchange membrane 11, and grooved separator plates 2 are located above and below the bonded body. The area of the ion exchange membrane is electrode 1
It is larger than 2, and the periphery is sandwiched by gaskets to insulate between the seals of each cell and the separator plates. As shown in the figure, when the gas passage 13 is installed inside the laminate (internal manifold type) as required, the gasket also seals the gas passage.
The grooved separator plate 2 can have various structures such as a case where a porous grooved plate is fitted in the groove portion or a mesh is used, and this structure does not limit the present invention.

(Embodiment 1) FIG. 1 shows a cross section of a cell according to Embodiment 1 of the present invention. In the figure, the gasket 21 has a 0.7 mm-thick ethylene-propylene rubber (EPDM) sponge layer 23 of closed cells on one surface of the separator plate and an adhesive layer 22.
It is bonded through. Gasket 21 of the present invention
Is an independent bubble in the portion in contact with the ion exchange membrane 11,
It was possible to seal between the separator plates and between the ion exchange membrane and the separator while absorbing the thickness of the ion exchange membrane 11 by being compressed more than the portion sandwiched between the separator plates 2. The tightening pressure is 10 kg / when using the conventional bubble-free fluororubber.
Whereas cm ² was required, in the case of the gasket of the present invention, 3.5 kg / cm ² or more was sufficient. Further, since the sheet having only the sponge layer is very soft, when the internal pressure of the cells and the gas passages became high, the gasket was displaced to the outside and blown out, whereas in the case of the gasket of the present invention, the adhesive layer was used. The sponge layer was prevented from being displaced due to the adhesive force of and no blowout occurred.

(Embodiment 2) FIG. 2 shows a cross section of a cell of Embodiment 2 of the present invention. The gasket 31 is formed by adhering a 0.4 mm-thick EPDM closed-cell sponge layer 33 to one surface of an acrylic plate 32 having a thickness of 0.5 mm, and adhering the acrylic plate 32 to the separator plate 2 via an adhesive layer 34. is there. In addition to the sealing effect similar to that of Example 1, the gasket has the core material, so that it can be easily adhered to the separator plate without sagging, and no displacement occurred during adhesion.

In this embodiment, the above-mentioned material was used as the material of the gasket, but since this solid polymer electrolyte fuel cell has an operating temperature of 150 ° C. or lower, various elastic materials such as fluororubber can be used. . However, the ion exchange membrane has a sulfonic acid group as its exchange group and exhibits acidity,
Further, since water is generated and the reaction gas is humidified, the contact surface of the gasket is required to have acid resistance, water vapor resistance, hot water resistance and the like.

Any material can be selected as long as the above-mentioned conditions such as heat resistance, acid resistance, steam resistance, and hot water resistance are satisfied, and the present invention is not limited to the materials of the examples.

Further, in the present embodiment, the method of sealing the ion exchange membrane from one direction by using one gasket was shown, but the same method can be achieved by using the method of sandwiching the ion exchange membrane by using two gaskets. The effect was obtained. Further, although the solid polymer electrolyte fuel cell has been described as an example in the above-mentioned embodiment, the same effect is exhibited also in the phosphoric acid fuel cell, the alkaline fuel cell and the like.

[0022]

As described above, according to the present invention, in the fuel cell, the gasket has a structure in which a sponge layer of closed cells is adhered to at least one surface of the separator plate. This allows
Since the sponge layer of closed cells absorbs the thickness of the ion exchange membrane and the unevenness of the separator plate by compressing the bubbles, excellent sealing performance can be realized with a small tightening pressure. Also,
Since the sponge layer of closed cells is adhered to the separator plate via the adhesive layer, the sponge layer does not escape to the outside due to the adhesive force even when high-pressure gas is used inside.

Due to the above effects, the tightening pressure can be greatly reduced, so that the strength of the end plate, the separator, the electrode, etc. can be reduced. For example, instead of the end plate conventionally made of stainless steel, It is possible to use materials such as engineered plastics, and it is possible to realize a fuel cell that is small, lightweight, and highly economical.

[Brief description of drawings]

FIG. 1 is a sectional view of a cell according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a cell according to a second embodiment of the present invention.

FIG. 3 is an external view of a general solid polymer electrolyte fuel cell

FIG. 4 is a sectional view of a general cell.

[Explanation of symbols]

 1 Gasket 2 Separator Plate 3 Current Collector Plate 4 Insulating Plate 5 End Plate 6 Hydrogen Inlet 7 Hydrogen Outlet 8 Oxygen Inlet 9 Oxygen Outlet 10 Drain Drain 11 Ion Exchange Membrane 12 Electrode 13 Gas Passage 21 Gasket 22 of Example 1 22 Adhesive Layer 23 Sponge Layer 31 Gasket of Example 2 32 Acrylic plate 33 Sponge layer 34 Adhesive layer

Front page continuation (72) Inventor Nobuo Eda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A fuel cell in which a gasket is arranged around the periphery of a unit cell composed of a positive electrode, an electrolyte plate and a negative electrode, and a separator plate is interposed between the gaskets, and the gasket is a closed-cell sponge layer on at least one surface of the separator plate. A fuel cell having a structure in which are adhered via an adhesive layer. 2. A gasket is arranged around the periphery of a unit cell composed of an ion exchange membrane made of a solid polymer and a positive electrode and a negative electrode having at least an electrode catalyst layer on the surface in contact with the ion exchange membrane, with a separator plate interposed therebetween. A fuel cell in which a gasket having a structure in which a sponge layer of closed cells is adhered to at least one surface of a separator plate via an adhesive layer in a stacked fuel cell is used.