JPH07312223A - Fuel cell - Google Patents

Abstract

PURPOSE:To provide a light and highly economical fuel cell by using a gasket exhibiting high sealing property with low fastening pressure. CONSTITUTION:In a fuel cell having a gasket 31 arranged on the periphery of a unit cell consisting of a positive electrode 12, an electrolytic plate 11, and a negative electrode 12, and laminated through a separator plate 2, the gasket has a closed cell sponge layer 33 integrally adhered on at least one surface of a rubber plate 32.

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]

[Chemical 1]

[0004]

[Chemical 2]

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) p. 2209, a method is adopted in which water vapor is introduced into the cell by passing the reaction gas through a humidifier 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 that is not joined to the electrodes is sandwiched by upper and lower gaskets.

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

Further, in US Pat. No. 4,826,741, silicon rubber and fluorine rubber 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 integrally bonded to at least one surface of a rubber plate.

[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. Further, since the closed air bubbles are compressed, stress relaxation is small, and the sponge layer is adhered to the substrate of the rubber solid layer, so that the sponge layer and the substrate are adhered even when a high pressure gas is used inside. The sponge layer does not escape to the outside due to the force.

[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 thickness of 0.8 m.
m ethylene-propylene rubber (EPDM) 22 with 0.7 mm thick EPDM closed-cell sponge layer 2 on one side.
3 is adhered. The gasket 21 of the present invention is
Independent air bubbles in the portion in contact with the ion exchange membrane 11 are compressed more than in the portion sandwiched between the separator plates 2 to absorb the thickness of the ion exchange membrane 11 and between the separator plates and between the ion exchange membrane and the separator. Was able to do both seals. The tightening pressure is 10 kg / cm when the conventional bubble-free fluororubber is used.
^{While 2} was required, in the case of the gasket of the present invention, 3 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 shifted to the outside and blown out, whereas in the case of the gasket of the present invention, a hard rubber plate was used. Became a core material, and the adhesive force between the rubber plate and the sponge layer prevented the sponge layer from being displaced, so that blowout did not occur.

(Embodiment 2) FIG. 2 shows a cross section of a cell of Embodiment 2 of the present invention. In the gasket 31, a 0.4 mm-thick EPDM closed-cell sponge layer 33 was adhered to both surfaces of a 0.7 mm-thick EPDM plate 32. In addition to the sealing effect similar to that of Example 1, since the sponge layer also exists on the surface in contact with the separator plate, the sponge layer absorbs irregularities on the surface of the separator plate, further increasing the sealing effect. Therefore, it becomes possible to suppress the processing accuracy of the contact surface of the separator plate to a low level. A sealing pressure of 2 kg / cm ² was sufficient when this gasket was used.

Although the above-mentioned materials are used as the material of the gasket in this embodiment, since the operating temperature of this solid polymer electrolyte fuel cell is 100 ° C. or lower, various elastic materials can be used. However, since the ion exchange membrane has a sulfonic acid group as its exchange group and shows acidity, the contact surface of the gasket must be acid resistant.

Any material can be selected as long as the above heat resistance and acid resistance conditions 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 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 integrally bonded to at least one surface of a rubber 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 closed-cell sponge layer is adhered to the rubber plate, 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 Rubber Plate 23 Sponge Layer 31 Gasket of Example 2 32 Rubber plate 33 Sponge layer

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 sponge layer of closed cells on at least one side of a rubber plate. A fuel cell with a structure in which the two are bonded together. 2. A gasket is provided around the periphery of a unit cell composed of a solid polymer ion exchange membrane and a positive electrode and a negative electrode having electrode catalyst layers on both sides in contact with the ion exchange membrane,
In a fuel cell stacked with a separator plate interposed,
A fuel cell using a gasket having a structure in which a sponge layer of closed cells is integrally bonded to at least one surface of a rubber plate.