JPS6243072A - Fuel cell - Google Patents

Abstract

PURPOSE:To increase sealing ability by sealing the end, parallel to grooves, of a ribbed electrode with thermoplastic resin film, forming recesses on the surface, which is in contact with a matrix, of the electrode, and embedding a material having affinity with phosphoric acid in the recesses. CONSTITUTION:A set of ribbed electrodes 3 which have passages 2 perpendicularly intersecting each other are arranged on each side of a matrix impregnated with phosphoric acid serving as electrolyte to form a unit cell. A plurality of unit cells are stacked with separators 5 interposed to form a fuel cell. The end 7, parallel to grooves 2, of the electrode 3 is sealed with a thermoplastic film 8, and two or more recesses 9 are formed on the surface, which is in contact with the matrix 1, of the electrode 3. A matrix 10 having affinity with phosphoric acid comprising phosphoric acid resistant particles such as silicon carbide and graphite is embedded in the recesses 9. Thereby, the matrix is uniformly distributed between ribbed electrodes, and sealing ability of gas is remarkably increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell in which the airtightness is particularly improved around the end of a ribbed electrode.

[Technical background of the invention and its problems]

2. Description of the Related Art Fuel cells are conventionally known as devices that directly convert energy contained in fuel into electrical energy. This fuel cell usually consists of a matrix impregnated with an electrolyte and a pair of ribbed electrodes made of a porous material with flow grooves placed between them to form a unit cell, and this unit cell is stacked in multiple layers with a separator in between. This is a configuration of a fuel cell stack.

Then, a fluid fuel such as hydrogen is brought into contact with the flow groove of one electrode, and a fluid oxidizer such as oxygen is brought into contact with the flow groove of the other electrode. It is operated to extract electrical energy from between the electrodes.

Here, the flow grooves of these ribbed electrodes form flow paths for fluid fuel and fluid oxidant, respectively, and when stacking the above unit cells, they are electrically conductive and gas permeable. In this method, a separator is sandwiched between each unit cell and laminated. In this laminated state, each laminated cross-section is hermetically sealed, leaving only the openings at both ends of the groove of the ribbed electrode.

Incidentally, the ribbed electrode is made of a porous body having pores, and is gas-sealed to prevent gas leakage from both ends parallel to the flow grooves. One example of this gas seal is to form a U-shaped thermoplastic film parallel to the groove at the end of the ribbed electrode (Japanese Patent Application No. 59-267166).
However, when a pair of ribbed electrodes are laminated one after another, the matrix cannot be completely applied to the ends of the laminate, which may cause gas to leak from the top of the thermoplastic resin film. In other words, since the thermoplastic resin film is water repellent and non-adhesive, the matrix aggregates on the film, creating gaps there.

As described above, in the configuration using the conventional sealing method, there is a problem in maintaining a perfect sealing function even during the production of the laminate, and a more reliable sealing structure has been desired.

[Purpose of the invention]

An object of the present invention is to provide a highly reliable fuel cell by improving the gas seal at the end of a ribbed electrode.

[Summary of the invention]

In the fuel cell according to the present invention, the ends of the ribbed electrical bridge parallel to the flow grooves are gas-sealed with a thermoplastic resin film, and furthermore, at least the surface of the thermoplastic resin film in contact with the matrix is provided with recesses. The present invention is characterized in that a phosphoric acid-philic substance is embedded in the recesses to reduce the water repellency of the thermoplastic resin film and to uniformly disperse the matrix between the ribbed electrodes.

[Embodiments of the invention]

The present invention will be described below with reference to an embodiment shown in FIGS. 1 and 2. First, in FIG. 1, a unit cell 4 is made by arranging a pair of ribbed 11m3.3 having flow grooves 2 in mutually orthogonal directions sandwiching a matrix 1 impregnated with phosphoric acid as an electrolyte. A fuel cell stack 6 is constructed by stacking a plurality of these with separators 5 in between.

In the fuel cell according to the present invention, the end 7 of the ribbed electrode 3 in FIG. A recess 9 is provided in the recess 9 (in which a diphilic phosphoric acid substance 10 is embedded).

Here, the shape of the recess 9 may be any shape such as spherical or cylindrical, and preferably the opening is narrow and widened toward the bottom so that the phosphoric acid-philic substance 10 is difficult to come out.

It is desirable that the size is several microns or more in inner diameter and several microns or more in depth, and that they are uniformly dispersed over the entire surface that contacts the matrix. Further, the area covered by the recesses is at least 1 inch or more with respect to the whole, and the larger the area of the recesses, the more phosphoric acid affinity can be increased, and the better the compatibility with the matrix.

There are two methods for providing the recess 9. One is to seal the end 7 before sealing with a thermoplastic film 8.
The other method is to provide recesses 9 in advance on the surface of the thermoplastic resin film that will be in contact with the matrix and then seal the film.The other method is to provide recesses 9 on the surface of the thermoplastic resin film after sealing. This is because the porosity of the end 7 of the ribbed dragonfly 3 made of carbon fiber is increased. As a result, the gaps between the carbon fibers become larger, and as a result, the recesses 9 are uniformly formed over the entire end. This porosity is desirably about 40% or more, and the larger the porosity is, the larger and deeper the recesses 9 will be. The recesses 9 are provided by mechanically cutting the surface, or by polishing with sandpaper or a relatively coarse hard powder such as silicon carbide or alumina.

Next, after sealing, a method for forming recesses 9 on the surface of the thermoplastic resin film 8 is to heat the end portion 7 to a temperature higher than the melting point of the film with the surface in contact with the matrix facing upward, and re-fuse the film. Due to the decrease in viscosity of the film and its own weight, the film is gradually lowered in layers from the surface of the ribbed electric bridge 3 toward the inside.

As the film descends, the carbon fibers protrude from the surface, and the gaps between the carbon fibers become recesses. Further, the recesses 9 can be formed by mechanically cutting the surface or polishing with hard powder having relatively fine particles.

It is preferable to use a material that is resistant to phosphoric acid and easily wetted by phosphoric acid, such as silicon carbide, graphite, activated carbon, etc. , and silicon, which does not dissolve when reacted with phosphoric acid and produces phosphates.

Elemental metals or oxides such as titanium, tin, aluminum, and zinc can also be used. These shapes are
Preferably, the particles are as fine as possible, for example, the average particle diameter is about 0.45 μm. The force of the front particles is easily embedded in the recesses and is easy to be uniform - yet a smooth surface is easily formed, and the thickness of the matrix can be made uniform.

Next, as a method of putting these phosphoric acid-loving substances 10 into the recesses 9, after putting the fine particulate phosphoric acid-loving substances 110 into the recesses 9 and pushing them in by applying pressure from above with a spatula, roller, etc. Remove excess phosphoric acid substances.

This method improves the compatibility between the thermoplastic resin film and the matrix, but if dry particles are used, the phosphoric acid in the matrix may be absorbed and the viscosity of the matrix may change. Before applying the matrix, add a small amount of phosphoric acid to the phosphoric acid material 10, which needs to be absorbed by the phosphoric acid material in the recesses in advance, and knead it.
It is also possible to put the kneaded product into the recess 9 and push it in by applying pressure from above. In this case, the weight ratio of phosphoric acid to the phosphoric acid substance is approximately 1:1 or less, and it is desirable that the amount of phosphoric acid is as small as possible.If the weight ratio becomes 1:1 or more, the viscosity of the kneaded product decreases; The diphosphoric acid covers the surface of the recessed portion and becomes water-repellent, and the phosphoric acid-philic substance is repelled, so that the phosphoric acid-philic acid effect may not be obtained.

In this manner, the surface can be improved to be phosphoric acid philic by providing a recess on the surface of the surface that will come into contact with the MAX and embedding a phosphoric acid philic substance therein.

Therefore, the matrix 1 can be applied to the child's body up to the end of the laminate without agglomerating, and it is possible to prevent the thermoplastic resin film 8 from leaking from the top.

An example of a manufacturing method using silicon carbide as the phosphoric acid material 10 and 1 lum of PF' as the thermoplastic resin film 8, using a material with a high porosity at the end 7 of the ribbed electrode 3. In this case, the end portion 7 of the ribbed electrode 3 has a porosity of 70
A head with an average pore diameter of 65 μm was used.

U-shaped PP as thermoplastic resin film 8 on end 7
After placing the film (O, 2SH layer) on the film and heating it to 340C to melt the film, pressurize it with a pressure of 10φ layer for 5 minutes to make it integral. On the surface of the surface that comes into contact with Tsukusu.

A fine hemispherical recess 9 was obtained, the average diameter is μ
The number was approximately 2,500 eccentric. The recess 9 (using ultrafine silicon carbide (average particle size 0.45μ) as the diphilic phosphoric acid substance 8) 105% to this silicon carbide
! J phosphoric acid was added at a weight ratio of 1:0.8, kneaded, placed in the recess 9, and further pushed in with a roller so that a surface pressure of about 2 ψ billion was applied from above. When Matrix 1 was applied to this electrographic image and the aggregation property was examined, almost no aggregation was observed, and the affinity with Matrix 1 was significantly improved. Further, after one test, no leakage from the top of the thermoplastic resin film was observed.

〔Effect of the invention〕

As described above (according to the second aspect of the present invention), the edges of the ribbed IT electrode parallel to the flow grooves are sealed with a thermoplastic resin film, and at least the surface of the film that contacts the matrix is provided with a recess. By filling the recess with a phosphoric acid substance, the gas sealing properties of the ribbed electrode end are improved, improving the reliability of the fuel cell.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of a fuel cell stack of a fuel cell according to the present invention, and FIG. 2 is a cross-sectional view showing an enlarged end portion of a ribbed electrode according to the present invention. 1.゛°matrix 2...Flow groove 3...Ribbed electrode 4...Unit cell 5...Separator
6... Fuel cell stack 7... Electric bridge end
8... Thermoplastic resin film 9... Concave portion
10...Pro-phosphoric acid substance agent Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata Figure 1 Figure 2

Claims (2)

[Claims] (1) A unit cell is constructed by arranging a pair of ribbed electrodes in which fluid fuel or fluid oxidant flow grooves are formed between a matrix impregnated with an electrolyte, and multiple unit cells are stacked with a separator in between. In the fuel cell stack configured as above, the ends of the ribbed electrodes parallel to the flow grooves are gas-sealed with a thermoplastic resin film;
Furthermore, a fuel cell characterized in that a recess is provided at least on the surface of the thermoplastic resin film in contact with the matrix, and a phosphoric acid-philic substance is embedded in the recess. (2) The fuel cell according to claim 1, wherein phosphoric acid-resistant particles such as silicon carbide and graphite are used as the phosphoric acid-philic substance.