JPS61227368A - Fuel cell - Google Patents

Abstract

PURPOSE:To maintain stable performance of a fuel cell over a long period by using a thermoplastic resin film in each rib electrode so as to prevent its warping. CONSTITUTION:A thermoplastic resin film 4 is heated and pressed into a peripheral region in the end section 2a of the rib electrode 2 of each cell unit to form a gas seal section having an I-shaped cross section. Due to the I-shaped cross section, this gas seal section has minimal stress concentration and therefore warping of the rib electrode 2 is almost prevented as compared to the conventional rib electrode thereby maintaining stable performance over a long period. Since the film 4 does not protrude from the end surface of the electrode base as distinct from the conventional method of directly sealing the end surface, rib electrodes 2 can be easily stacked together.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell in which airtightness can be improved, particularly around the ends of ribbed electrodes.

(Technical background of the invention and its problems) Fuel cells are conventionally known as devices that directly convert energy contained in fuel into electrical energy.The ribbed electrode type fuel cell stack 10 As shown in the figure, a pair of ribbed electrodes 2 made of normal carbon material are arranged with a matrix 1 impregnated with phosphoric acid as an electrolyte sandwiched by a plurality of grooves 5 regularly arranged in parallel in directions perpendicular to each other. A unit cell 6 is constructed by stacking a plurality of unit cells 6 with separators 3 interposed therebetween.

By the way, since the ribbed electrode 2 is a porous body having pores with an average diameter of about 10 microns, the leakage A causes crossover between the fluid fuel B and the fluid oxidizer C, as shown in FIG. ,Finally.

There is a risk that the fuel cell will not be able to operate. For this reason, gas seals are provided from both ends to prevent gas diffusion and leakage. As one of these sealing methods,
There is a method in which a heat-resistant, phosphoric acid-resistant film is heated and press-fitted onto the end portion 2a of the ribbed electrode 2.

As shown in Fig. 8, this film is heated and press-fitted by placing a U-shaped thermoplastic resin film 4 at the end of the ribbed electrode 2, and press-fitting the film from the top and bottom while heating. It can be sealed relatively easily and has excellent sealing properties.

However, in the film formed by this method, the electrode warps as the temperature decreases after heating and press-fitting.

In this state, it becomes difficult to stack the batteries.

As a result of various investigations into the causes of this warping, it was found that warping occurs because stress is concentrated in a portion due to the difference in linear thermal expansion between the film and the electrode base material. As described above, structures using conventional sealing methods have problems in maintaining a stable sealing function over a long period of time, and a more reliable sealing structure has been desired.

[Purpose of the invention]

An object of the present invention is to provide a fuel cell with improved reliability by improving the gas seal structure of the ribbed electrode end.

[Summary of the invention]

In the fuel cell according to the present invention, a unit cell is constructed by arranging a pair of ribbed electrodes in which a rib-like flow path through which a fluid fuel or a diagonal oxidizer passes, sandwiching a matrix impregnated with an electrolyte. In a fuel cell stack constructed by laminating a plurality of layers with separators interposed therebetween, a thermoplastic resin film is formed by heating and press-fitting mold 1 around the end of the ribbed electrode, thereby reducing the amount of water from the end of the ribbed electrode. It is characterized by preventing leaves and preventing stress concentration from occurring due to the thermoplastic resin film.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 shows an example of the configuration of a ribbed electrode 2 of a unit cell in a fuel cell according to the present invention. That is, a thermoplastic resin film 4 is heated and press-fitted into the periphery of the end portion 2a of the ribbed electrode in the unit cell 6 to form a gas seal portion. Here, the thermoplastic resin film 4 may be any material as long as it has pressure resistance and phosphoric acid resistance, and is preferably made of PTFE, PFA, or FE.
It is a fluororesin such as P. Its thickness is 0.0
Use one of about 1 to 1 kaku.

On the other hand, as a method of heating and press-fitting the thermoplastic resin film 4 into the end portion 2a of the ribbed electrode 2 in a ■ shape.

For example, as shown in FIG. 2, a slit 7 is provided at the end of the ribbed electrode 2, and a thermoplastic resin film 4 is placed on the upper and lower surfaces so that its approximate center is located in the slit 7. After melting by heating above the melting point, pressure is applied from the upper and lower surfaces at a pressure of 2 to 35 kg/a# for 1 minute or more. By applying pressure, the melted film enters the slit 7 and further impregnates the periphery of the slit 7 and the remaining thickness,
Finally, the films 4 from the upper and lower surfaces are connected as a surface.

At the same time, part of the film is impregnated from the top and bottom surfaces and fixed by the left and right electrode base materials, so the shrinkage stress of the film remains, but as a result.

It is a type 1 that is well balanced vertically and horizontally.

In this way, by heating, press-fitting and sealing the thermoplastic resin film 4 into the shape with less stress concentration, it is possible to maintain stable performance over a long period of time with almost no warpage compared to conventional films. was confirmed. In addition, since the end face is not directly sealed as in the conventional method, there is no protrusion due to the film 4, and the end face is kept perpendicular and parallel to the electrode base material itself, so there is an advantage that lamination is easy.

Here, the width of the slit 7 is about 0.01 to 1 square.

If it is 1- or more, the shrinkage of the film 4 is large, and a depression is formed in the film portion above the slit 7.

Furthermore, there is a risk that the electrode may warp and crack.

Furthermore, if the length is less than 0.01 m, the amount of film 4 that can be inserted will be small and the seal will be insufficient. The depth of the slit 7 is such that the remaining thickness of the electrode is 0.2 m or more.

In the embodiment shown in FIG. 2, the slits 7 are formed from two directions on the upper and lower surfaces with the same width and depth, but they may have different widths and depths. Also, the remaining thickness 2' of the electrode 2 is 0.2 m.
If it is 5t or more, slit 7 can be made only from one side,
The thermoplastic resin film 4, which produces the same effect, may be heated and press-fitted into the mold 1 at any position within the end, preferably near the center between the end face and the groove 5. Moreover, it goes without saying that the sealing effect will be further improved if a plurality of slits 7 are provided and the film is heated and press-fitted.

Next, the other actual flow side for forming the thermoplastic resin film 4 will be explained. In the embodiment shown in FIG. 2, the film 4 impregnates and seals the remaining thickness 2' of the electrode base material, but in the third embodiment, the film 4 on the upper and lower surfaces is impregnated without intervening the electrode base material. are directly connected as a surface and sealed. This is a method in which the end of the ribbed electrode 2 is divided into two parts, and thermoplastic films 4 are placed on the upper and lower surfaces so that the divided sides become the center, and heated and press-fitted. From the top and bottom of the film 4,
It flows along the divided surface while impregnating the periphery thereof, and finally the upper and lower films are connected as a surface and sealed, and at the same time, the two divided ends 2a are integrated. In addition, a part is impregnated from the upper and lower surfaces to form the first type. The position of dividing into two may be anywhere as long as an H-shape can be formed, but preferably near the center between the end face and the groove.

In this method, the film flows along the dividing plane, and the films on the upper and lower surfaces are directly connected to each other as a surface, so that the sealing performance is good. However, in order to prevent the divided southern end from moving when the film is press-fitted, it is necessary to press from the end face direction.

In Fig. 4, in order to further ensure the sealing performance, the end of the ribbed electrode 2 is divided into two parts using a film to secure the sealing surface in advance. In this method, the thermoplastic resin films 4 of 2 are placed on each other, heated and press-fitted from the upper and lower surfaces. When the film is melted and then press-fitted, an I-shaped seal structure is formed almost simultaneously with the press-fitting and is integrated, so no warpage occurs.

Although it takes time to process the film into a U-shape, the sealing performance is more reliable.

In Fig. 5, in order to improve sealing performance and workability, a thermoplastic resin film 4 of 1 type made in advance by extrusion casting, etc. is used, and the end of the ribbed electrode 2 and the divided end are each made of 1 type. This method involves sandwiching it between films, heating it, and press-fitting it. Almost simultaneously with press-fitting, a type 1 seal structure is formed and both are integrated. This method requires a type 1 film obtained in advance by extrusion casting or the like, but it is easy to work with and has perfect sealing properties.

〔Effect of the invention〕

As described above, according to the present invention, by using a ribbed electrode formed with a thermoplastic resin film having a gas-sealed structure at the end, there is no warpage caused by the thermoplastic film, and as a result, stable performance can be achieved. Can be maintained for a long time. That is,
Improvements in reliability and life characteristics can be expected.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the end of the ribbed electrode used in the fuel cell of the present invention, and FIGS. 2 to 5 show a method of forming a thermoplastic film on the end of the ribbed electrode used in the present invention. 6 is a vertical perspective view showing an example of the structure of a fuel cell, FIG. 7 is a sectional view showing an example of the structure of an electrode end of a conventional fuel cell, and FIG. FIG. 2 is a perspective view of an electrode end of a conventional fuel cell. 1... Matrix 2... Ribbed electrode 3...
・Separator 4...Thermoplastic resin film 5...Gas groove 6...Unit self...
Slit IO...Fuel cell stack (8733) Agent Patent attorney Yoshiaki Inomata (and 1 other person) Figure 1 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] A unit cell is constructed by arranging a pair of ribbed electrodes in which a rib-like flow path is formed through which a fluid fuel or a fluid oxidizer passes, sandwiching a matrix impregnated with an electrolyte, and this unit cell is connected to a plurality of unit cells via a separator. 1. A fuel cell stack configured by stacking the ribbed electrodes, characterized in that a thermoplastic resin film heated and press-fitted into an I-shape for gas sealing is formed around the end of the ribbed electrode.