JPS6322422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for sealing a gas separation plate and a unit cell in a stacked fuel cell.

A conventional fuel cell of this type is shown in FIG. In the figure, 1 and 1' are gas separation plates,
2 is a gasket for sealing the oxidizer electrode, 3 is the oxidizer electrode, 4 is the electrolyte matrix, and 5 is the fuel electrode. The oxidizer electrode 3, the electrolyte matrix 4, and the fuel electrode 5 constitute a single cell. 6 is a gasket for sealing the fuel electrode. The second one is a stack of unit bodies 1 to 6 in FIG.
0 is air as an oxidizing agent, and 11 is fuel.

Next, the operation will be explained. gas separation plate 1,
1', electrodes, gaskets and electrolyte matrix are stacked in the order shown in FIG. That is, the oxidizer electrode 3 is placed inside the window frame-shaped gasket 2 of the oxidizer electrode 3.
The electrolyte matrix 4 is placed on top of the electrolyte matrix 4, and the fuel electrode 5 fitted inside the window frame-shaped gasket 6 of the fuel electrode 5 is placed on top of the electrolyte matrix 4. This process is repeated to stack a plurality of unit bodies as shown in FIG. 2 to assemble a stacked fuel cell. After assembly, air 10 and fuel 11 are supplied to the current collector plate 8.
The output is extracted from the battery and the stacked battery is operated.

Conventional stacked fuel cells are constructed as described above, so in order to seal the gas and liquid between the gas separation plate and the cell, the thickness of both electrodes and their respective gaskets must be equal in the stacked state. The thickness had to be designed based on the material constants of the electrodes and gasket. In addition, as gaskets require considerable elasticity, fluoro rubber materials are used, but they have drawbacks such as severe deterioration in batteries that use phosphoric acid electrolytes at high temperatures, making it difficult to maintain long-term sealing performance. It was hot.

This invention was made to eliminate the drawbacks of the conventional gaskets as described above, and each gasket was replaced with FEP (tetrafluoroethylene).
A stacked fuel cell that uses a material that can withstand high-temperature phosphoric acid and can be melt-molded, such as PFA (perfluoroalkyl vinyl ether copolymer) or PFA (perfluoroalkyl vinyl ether copolymer), to create a seal between the gas separation plate and the unit cell. The purpose is to provide a manufacturing method for.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 3, 1 and 1' are gas separation plates;
16 and 16' are sealing surfaces of the gas separation plates 1 and 1' for the fuel electrode 14, 17 and 17' are phosphoric acid supply grooves, and 18 and 18' are phosphoric acid supply holes; ′
It is connected with. 11 is a sealing material between the oxidizing agent electrode 12 and the gas separation plate 1, and 12 is the oxidizing agent electrode. 13 is an electrolyte matrix, 14 is a fuel electrode, 15 is a hollow band-shaped sealing material between the fuel electrode 14 and the gas separation plate 1', and 19 is this hollow portion.

Next, the operation will be explained. First, the fuel-side sealing material 15 is placed on the sealing surface 16' of the gas separation plate 1', and the fuel electrode 14 is placed between the inner sides of the sealing materials 15 and 15.
In other words, the sealing materials 15 and 15 are placed along both sides of the fuel electrode 14, respectively, and placed on the gas separation plate 1'. At this time, the fuel electrode 14 is brought into contact with the convex part of the fuel flow groove of the gas separation plate, and at the same time, the phosphoric acid supply groove 17' of the gas separation plate 1' is made to coincide with the hollow part 19 of the sealing material 15. do.
Next, the electrolyte matrix 13 is placed, and the oxidizer electrode 12 and the sealing material 11 are laminated along it, and the gas separation plate 1 is placed on top to form a unit. Thereafter, the above operations are repeated to assemble a stacked fuel cell consisting of a plurality of units as shown in FIG. The above sealing material is PFA or
Resistant to phosphoric acid under high temperature like FEP, PTFE
Unlike (tetrafluoroethylene polymer), it must be made of a material that can be melt-molded. Further, the sealing material at this time is made of powder molded so that its thickness is somewhat thicker than the thickness of each electrode.

Now, pressure is applied to the assembled stacked fuel cell using a pressing plate or the like in the stacking direction. The pressure at this time is preferably in the range of 1 to 5 kg/cm ² as in the case of battery operation. After this, either the battery itself is placed in an inert gas atmosphere, or an inert gas is flowed in place of the fuel 11 and air 12, the electrodes are placed in an inert gas atmosphere and the sealing material is fused. Heat treat as much as possible. For both PFA and FEP, heat treatment should be carried out near their respective melting points (melting point ±50°C). This is because the higher the temperature is than the melting point, the more the sealing material partially decomposes and cannot exhibit its sealing properties, and when heat treated at a temperature much lower than the melting point, the fusion does not progress completely and the mechanical strength of the sealing material is weak. , and the sealing performance is also poor.

During the heat treatment, pressure is simultaneously applied in the stacking direction, so the sealing material, which was initially somewhat thicker than the electrodes, becomes as thick as the electrodes. From this state, the temperature of the stacked battery is lowered to the operating temperature of the battery, and phosphoric acid reaches the electrolyte matrix 13 from the phosphoric acid supply hole through the sealing material hollow part 19 of the fuel cell, making the entire electrolyte wet.

After the above operations, operate the stacked fuel cell,
Get the output.

In addition, in the above embodiment, the sealing materials 11 and 15
Although the sealing material has been described as being powder-molded, it may also be a sealing material that is melt-molded and the same effects as in the above embodiments can be obtained.

Further, in the above embodiment, the shape of the sealing material of the fuel electrode and the oxidizer electrode was as shown in FIG. It has the effect of

As described above, according to the present invention, a sealing material made of a material that is thicker than the thickness of the electrode and is resistant to phosphoric acid at high temperatures and can be melted by heat is placed along the side surface of the electrode between the electrolyte matrix and the gas separation plate. The cells were placed and heat treated while applying pressure in the laminated direction of the cell and the gas separation plate so that the sealant was fused to the electrolyte matrix and the gas separation plate. Even without strictly adjusting the thickness, the sealing material is fused to the same thickness as the electrode, the electrolyte matrix and gas separation plate are integrated, and a highly reliable seal can be obtained. be.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the structure of a conventional fuel electrode unit, FIG. 2 is a perspective view of a conventional stacked fuel cell, and FIG. 3 is a structure of a unit according to an embodiment of the present invention. FIG. 2 is an exploded perspective view. In the figure, 11 and 15 are sealing materials. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a stacked fuel cell in which a plurality of unit cells and gas separation plates each having a fuel electrode, an electrolyte matrix, and an oxidizer electrode are stacked, the fuel cell being thicker than the thickness of the electrodes and under high temperature conditions. A sealing material made of a material that can withstand phosphoric acid and can be melted by heat is placed along the side surface of the electrode between the electrolyte matrix and the gas separation plate, and in the stacking direction of the cell and the gas separation plate. A method for manufacturing a stacked fuel cell, wherein the sealing material is fused to the electrolyte matrix and the gas separation plate by heat treatment while applying pressure. 2. Production of a stacked fuel cell according to claim 1, wherein either one of a tetrafluoroethylene-hexafluoropropylene copolymer and a perfluoroalkyl vinyl ether copolymer is used as a sealing material. Method.