JPS61185869A - Fuel cell - Google Patents

Abstract

PURPOSE:To improve reliability by improving gas seal construction of a laminated interface end portion of a unit cell by sealing uneven portions on the laminated end face of the unit cell and small clearances of the laminated interface end portion with fluoro-group rubber paint having heat proofness and electrolyte proofness. CONSTITUTION:Fluro-group rubber paint 20 having heat proofness and electro lyte proofness is coated on the small clearances 19 on a laminated interface end portion of a unit cell and large uneven portions of the laminated end por tion, and putty 18 which is a sealing material for absorbing unevenness is coated thereon to be smooth so as to obtain sealed portions. In this process, as fluoro- group rubber paint, polyamine curing rubber, peroxide curing rubber, polyol curing rubber etc. are used. Then, inside and outside of a manifold can be sealed completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell, and more particularly to a fuel cell in which the gas seal structure at the end of the stacked interface of unit cells is improved.

[Technical Background of the Invention and Problems Therein] Fuel cells have conventionally been known as devices that directly convert energy contained in fuel into electrical energy. This fuel cell usually consists of a pair of porous electrodes sandwiching an electrolyte-impregnated matrix, with a fluid fuel such as hydrogen in contact with the back of one electrode, and a fluid such as oxygen with the back of the other electrode. Electrical energy is extracted from between the electrodes by bringing an oxidizing agent into contact and utilizing the electrochemical reaction that occurs.As long as the fuel and oxidizing agent are supplied, electrical energy can be extracted with high conversion efficiency. can be taken out.

By the way, the unit cell of a fuel cell based on the above-mentioned principle, especially using phosphoric acid as an electrolyte, is constructed as shown in FIG. As shown in the figure, the entire fuel cell device is configured.

That is, in FIG. 3, the unit cell has ribbed electrodes 2.3 (usually made of carbon material) formed of a porous material and provided with a catalyst on both sides of a matrix 1 impregnated with an electrolyte. The ribbed electrodes 2 and 3 have flow passages 4 and 5 for fluid fuel and fluid oxidant, respectively, on the opposite surface of the catalyst application surface. Furthermore, a separator 6 is arranged on the back surface of each ribbed electrode 2, 3 on the opposite side from the matrix 1.

In this way, the matrix 1, the ribbed electrode 2.3, and the separator 6 are stacked, and in this state, each stacked layer is stacked, leaving only the openings at both ends of the fluid fuel flow passage and the fluid oxidant flow passage of the ribbed electrode 2.3. The end face is hermetically sealed to form a unit cell.

A plurality of unit cells configured as shown in Fig. 3 are stacked,
As shown in FIG. 4, the unit cells are tightened with a predetermined pressure by a fastener 7 in order to establish electrical continuity between the unit cells. Thereafter, a manifold 10 having a fuel supply port 9 via a sealing material 8 is provided on one of the opposing end faces of this stacked body, and a manifold 12 having a fuel discharge port 1) and an electrolyte.
and a manifold 14 having an oxidizing agent supply port 13 on one of the other opposing end surfaces via a sealing material 8, and a manifold 16 having an oxidizing agent discharge port 15 on the other side, These manifolds10.
12, 14, and 16 are tightened with bolts or the like to maintain airtightness, thereby configuring the fuel cell device 17.

Therefore, in such a fuel cell device 1) in the electrolyte 7, when fluid fuel is supplied from the fuel supply port 9, this fuel branches through the flow path 4 of each unit cell and flows while being in contact with the back surface of the porous rib electrode 2. The fuel is then discharged from the electrolyte through the outlet 1). Furthermore, when a fluid oxidant is supplied from the oxidizer supply port 13, this oxidant flows through the flow path 5 of each unit cell and flows while contacting the back surface of the porous ribbed electrode 3.
Thereafter, the oxidizing agent is discharged from the oxidizing agent outlet 15. At this time, the fluid fuel is supplied into the porous ribbed electrode 2.3 by diffusion, and generates electrical energy as a fuel cell. Note that the output terminal is omitted in the figure.

Further, the fuel cell assembled in this manner is usually housed in a pressurized container and operated under high pressure conditions to prevent scattering of gas leaking from the manifold and to increase efficiency. here,
The pressurized container is pressurized and filled with inert gas to reduce the pressure difference between the reaction gas inside the manifold and the outside, and to prevent the reaction gas from leaking from the manifold into the pressurized container. The pressure inside the container is increased.

By the way, when attaching the manifold to the end face of the stacked unit cells of the fuel cell described above, the sealing part is smoothed with a heat-resistant and phosphoric acid-resistant putty material that absorbs the unevenness caused by the stacking. The manifold is attached via a gasket, which creates an airtight seal between the inside and outside of the manifold.

However, although heat-resistant and phosphoric acid-resistant putty materials alone can absorb large irregularities on the end faces of the laminated layers, they cannot completely fill the small gaps at the ends of the laminated interfaces. For this reason, it is not possible to completely seal the inside and outside of the manifold, and inert gas flows into the manifold from a pressurized container whose pressure is higher than that of the manifold. The fluid oxidizer is diluted, causing a decrease in concentration and resulting in a decrease in battery characteristics. for that,
Recently, there has been a strong desire for a more reliable sealing structure at the edge of the laminated interface.

[Object of the invention] The present invention was made in consideration of the above circumstances, and
The purpose is to improve the gas seal structure at the end of the laminated interface of the unit cell and to provide a fuel cell capable of improving reliability.

[Summary of the Invention] In order to achieve the above object, the present invention seals the irregularities on the stacked end faces of unit cells and the small gaps at the stacked interface edges with a fluorine-based rubber paint having heat resistance and electrolyte resistance. It is characterized by

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1(a) and 1(b).
) and FIG. 2. Figure 1 (a> is
This is a cross-sectional view showing an example of the configuration of the stacked interface end portion of the unit cell in the fuel cell according to the present invention, and FIG. 1(b) also shows the configuration of a conventional seal portion.

In other words, in this example, a fluorine-based rubber paint 20 having heat resistance and phosphoric acid resistance is applied to the small gap 19 at the edge of the laminated interface and the large irregularities on the end face of the laminated layer of the unit cell configured as described above, and the unevenness is applied thereon. A seal portion is formed by smoothing with putty material 18, which is an absorbent sealing material. Here, as the fluorine rubber paint, for example, polyamine vulcanized rubber, peroxide vulcanized rubber, polyol vulcanized rubber, etc. are used.

Conventionally, as shown in FIG. 1(b), only the uneven portions of the end faces of the stack are smoothed with a putty material 18.

Next, a manifold for supplying and discharging fluid fuel and fluid oxidizer was attached to the seal portion through a gasket 21 at a surface pressure of 5.5 to 97 cd, and the leak rate, that is, the leak coefficient was measured. In this case, the leakage coefficient is evaluated as 1 per unit seal length M at a differential pressure of 100100a.
It was determined from the amount of leakage over time, and the results are shown in Table 1 below.

[Table 1] From the table, the conventional method has a leakage coefficient of 0.151d/hr・
The leakage coefficient was 100avAQ, but with the seal configuration of this example, the leakage coefficient is 0.058se/hr'am.
-100#1) Electrolyte 1AQ, and in this example, it is possible to obtain a sealing effect approximately 2.5 times greater than that of the conventional method.

On the other hand, fuel cells undergo cooling and heating cycles when they are started and stopped, and there is a concern that their sealing function may deteriorate, so we conducted a heat cycle test that simulated these cycles to investigate changes in the leakage coefficient. In this case, the heat cycle was carried out in the range from room temperature to 200°C, and the results are shown in FIG.

From the figure, no significant change was observed in the leakage coefficient due to the heat cycle, and the initial value was 0.058jIi! /hr-shoes/100IIWAQ was 0.0601d/hr-shoes/100#IIIAq even at the 30th heat cycle, which shows that it has an extremely stable sealing function.

Furthermore, the change in leakage coefficient with respect to power generation time was determined using a fuel cell equipped with the seal structure according to this example. In this case, the power generation conditions are 205°C, 220mA/d, and 150mA/d.
The leak coefficient after 0 hours of operation was as shown in Table 2 below.

[Table 2] From the above results, it can be seen that a stable sealing function was maintained in terms of leakage coefficient.

As described above, by providing a fuel cell with the seal structure of this embodiment, the small gap 19 at the end of the laminated interface of the unit cell is completely filled with the fluorocarbon rubber paint 20, and the inside and outside of the manifold are separated. It is possible to completely seal it. This eliminates the possibility of inert gas flowing into the manifold from the pressurized container and diluting the fluid fuel and fluid oxidizer, which are reactive gases, making it possible to expect highly efficient and stable battery performance. .

[Effects of the Invention] As explained above, according to the present invention, a fluorine-based rubber paint is applied to the stacked end faces and the stacked interface ends of the unit cell, and a heat-resistant and electrolyte-resistant uneven absorbing coating is applied thereon. A smooth seal is formed with putty material, and a manifold for supplying and discharging fluid fuel and fluid oxidizer is attached via a gasket, maintaining extremely stable sealing function, improving reliability and long life. It is possible to provide a fuel cell that can be used for various purposes.

[Brief explanation of the drawing]

FIG. 1(a) is a sectional view showing one embodiment of the present invention.
Figure (1) Electrolyte> is a cross-sectional view showing the configuration of the sealing part according to the conventional method, Figure 2 is a characteristic diagram showing changes in sealing function according to the same example, and Figure 3 shows the stacked structure of the unit cell of the fuel cell. FIG. 4 is an exploded perspective view showing a fuel cell incorporating the same unit cell. 1... Matrix, 2, 3... Electrode with lip, 8゜18... Seal material, 20... Fluorine rubber paint, 2
2...Laminated end face. 1) Electrolyte i! ! !

Claims (4)

[Claims] (1) In a fuel cell constructed by stacking a plurality of unit cells each comprising a pair of ribbed electrodes in which flow paths for fluid fuel and fluid oxidizer are formed, sandwiching a matrix impregnated with an electrolyte, A fluorine-based rubber paint is applied to the stacked end faces and the stacked interface ends of the unit cell, and a smooth seal is formed on top of this using a heat-resistant and electrolyte-resistant putty material for absorbing unevenness. A fuel cell characterized by having a structure in which a manifold for supplying and discharging fluid fuel and fluid oxidizer is attached. (2) The fuel cell according to claim (1), wherein the fluorine-based rubber paint is polyamine vulcanized rubber. (3) The fuel cell according to claim (1), wherein the fluorine-based rubber paint is peroxide vulcanized rubber. (4) The fuel cell according to claim (1), wherein the fluorine-based rubber paint is polyol vulcanized rubber.