JPS61148765A - Electrode plates equipped with ribs for fuel cell - Google Patents

Abstract

PURPOSE:To improve air permeability, conductivity and mechanical strength of electrode plates in the caption through the formation of the electrode plates equipped with ribs by using carbon fiber fabrics for the board part with its entanglement part bonded with a carbide and using short carbon fibers for the rib part with its intersecting points bonded with a carbide. CONSTITUTION:One unit of a fuel cell is formed by installing electrode plates 1, 2 equipped with ribs, which support catalyst through the interposition of electrolyte. The electrode plates 1, 2 are constituted by forming its board part 9 by means of one to several carbon fiber fabrics 10 with its part of warp and weft entanglement bonded with a carbide produced through calcination of phenol fibers, forming the rib part 7 by means of short carbon fibers 11 with its intersecting points bonded with a carbide and uniting both with the same carbide. Through the use of carbon fiber fabrics, it is possible to secure high air permeability, good conductivity and firm form-maintaining capability and thereby improve performance and durability of the electrode plates greatly.

Description

[Detailed description of the invention] Ll Upper 5 + 1m Emperor 1 The present invention relates to a ribbed electrode plate used in a fuel cell.

BACKGROUND ART In fuel cells, especially high-temperature fuel cells that use an aqueous phosphoric acid solution as an electrolyte, the electrode plates are made of carbon material because it is chemically stable.

Such electrode plates often have a large number of porous ribs arranged in parallel with each other on one surface of a porous substrate, or electrode plates with ribs.

As a ribbed electrode plate, for example, US Pat. No. 4,165.
627@ specification and Japanese Patent Application Laid-open No. 100364/1983, short carbon fibers are used for both the substrate and the ribs, and the short fibers are bound together with carbide at their intersections. Something is known. However, such conventional plates have drawbacks as explained below.

In other words, the characteristics of a fuel cell electrode plate are largely influenced by the so-called gas permeability, which allows fuel gas and reference gas to pass through the substrate, and the electrical conductivity in the thickness direction, and it is important to maintain a balance between the two. However, since the above conventional electrode plate uses only short fibers as the carbon fibers 1, it is very difficult to control the bulk during manufacturing, and the short fibers tend to become too clogged or become coarse and bulky. However, if the short fibers are too clogged, the conductivity will increase but the porosity will decrease and the gas permeability will decrease, and if the short fibers become bulky, the gas permeability will improve but the conductivity will decrease and the gas permeability and conductivity will decrease. It's hard to find a balance between genders.

However, if the electrode plate does not have a good balance between gas permeability and electrical conductivity, a fuel cell with high power generation efficiency cannot be obtained.

In addition, since the above-mentioned conventional electrode plate uses only short carbon fibers, its mechanical strength is not inherently high, and the bond caused by the carbide is broken by some mechanical, electrical, or chemical action. In this case, the short fibers separate into pieces, and not only are they unable to maintain their shape, but their conductivity is greatly reduced. In particular, on the surface of the substrate facing the phosphoric acid aqueous solution that serves as the electrolyte, carbide embrittlement is likely to occur due to phosphoric acid, but when the bonds caused by the carbide are broken and the short fibers are separated, this surface is exposed to the catalyst. This has a large impact on the characteristics of the battery.

Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned drawbacks of conventional electrode plates, and to provide a fuel cell rib that has high gas permeability, electrical conductivity, and mechanical strength, and is excellent in durability. To provide polar plates.

Means for Solving 45. The present invention to achieve the above object provides an electrode plate having a large number of parallel porous ribs provided on one surface of a porous substrate, wherein the substrate is coated with carbon. fiber fabric is used,
and the warp and weft of the carbon fiber fabric are bound with carbide at their intersections, carbon fiber short fibers are used for the ribs, and the carbon fiber short fibers are bound with carbide at their intersections. It is characterized by a ribbed electrode plate for fuel cells.

To explain this invention in more detail, FIG. 2 is a schematic perspective view showing one unit of a stacked fuel cell. In FIG. 2, an electrolyte 3 made of, for example, an aqueous phosphoric acid solution is supported between two electrode plates 1.2. Further, between each electrode plate 1.2 and the electrolyte 3, a catalyst 4.5 made of, for example, platinum black is supported. Pole plate 1
．． 2 has a total thickness of about 2 to 5 mm.

Each plate 1.2 also has a large number of mutually parallel ribs 7 on one side thereof, and the ribs 7 form a groove 8 whose width and depth are both about 1 to 2.5 mm. is formed. That is, the two plates 1.2 are ribbed plates, and the plates 1 and 2 are arranged so that their sides without ribs 7 face each other and their grooves 8 are orthogonal to each other. Fuel gas (hydrogen gas,
A reference gas (air or oxygen gas) is flowed into the groove 8 of the other electrode plate.

A stacked fuel cell is constructed by stacking a large number of such units, and between each stack there is a partition plate 6, such as a graphite plate, that does not allow fuel gas or reference gas to pass through.
It is separated by

The electrode plate 1 (2) has a substrate 9 and ribs 7, as shown in FIG. 1 (schematic perspective view). However, the board 9
One to several sheets of carbon fiber fabric 10 are used, and carbide (not shown) is attached to the intersection of the warp and weft of the carbon fiber fabric 10, binding the warp and weft to each other. There is. Therefore, disturbances in the arrangement of warp and weft threads, that is, misalignment of stitches, do not easily occur.

On the other hand, for the ribs 7, short carbon fibers 11 are used. The short fibers are similarly bound together by carbide (not shown) at their intersections. The substrate 9 and the ribs 7 are also integrally bonded with the carbide used in the carbon m-fiber fabric 10 and the carbon fiber short fibers 11.

Note that the short fibers may intersect in contact with each other, or may intersect apart from each other.

The above-mentioned carbon fiber is a pitch-based carbon fiber, a polyacrylonitrile-based carbon fiber, or the like. The single yarn diameter is approximately 5 to 15 μm. Carbon fibers or graphite-based carbon fibers may be used, but graphite-based carbon fibers, especially polyacrylonitrile carbon fibers, are preferable because they have high electrical conductivity, corrosion resistance, and excellent mechanical properties. Most preferred. Fabrics made of such carbon fibers include plain woven fabrics, satin woven fabrics, and twill woven fabrics. Among these, plain weave is most preferable because it has the most interlacing of warp and weft yarns and has a stable structure. These fabrics provide the plates with high gas permeability, through-thickness conductivity, and mechanical strength.

In order to fully exhibit these characteristics, the above-mentioned fabric is
Preferably, the crimp rate is 20-200% and the lino weight per cm3 is 0.08-0.3 g. Here, the crimp rate is calculated using the formula, C=[(LL')/L']x100, where C
: Crimp rate (%) L: Length of the warp or weft measured when stretched straight L': Defined as the length of the warp or weft measured when forming the fabric. As is clear from this definition, a high crimp rate means a high degree of bending of the warp and weft at their intersection. Therefore, the higher the crimp rate, the more the warp and weft yarns are oriented in the thickness direction of the fabric, which forms a conductive path in the thickness direction. The weave or weave of the fabric also forms a passageway for the fuel gas and reference gas.

On the other hand, the above-mentioned short carbon fibers are used in the ribs, but the average length of the carbon fibers is comparatively low, as the ribs are required to have high electrical conductivity as well as gas permeability. The thickness is preferably about 50 to 80 μm so that the S conductivity can be improved by closely arranging the layers.

The carbides that bind the warp and weft of carbon fiber fabrics and the short fibers are organic fibers such as phenol fibers, polyvinyl alcohol fibers, and cellulose fibers, as well as pulp, phenolic resins, polyvinyl alcohol resins, tar, and pitch. It is obtained by burning and carbonizing organic matter. Therefore, the proportion of carbide in the electrode plate is 3 to 3% by weight for carbon fiber woven fabrics and short fibers.
The amount of carbide may be about 1 to 10.

The ribbed electrode plate according to the present invention can be manufactured by various methods, and a preferred example thereof will be shown below.

That is, first, a desired number of carbon fiber fabrics are laminated to form a laminate having a thickness of approximately 0.1 to 2.5 mm, and this is impregnated with a methanol solution of phenolic resin. At this time, the concentration of the phenol resin is preferably about 5 to 50% by weight, and the amount of impregnation is preferably about 5 to 40% by weight.

Carbon fiber fabrics impregnated in advance with a methanol solution of phenol resin may be laminated.

Next, as a lower mold, a split mold having a large number of parallel grooves with widths and depths of about 1 to 2.5 mm is used, and in the grooves of the lower mold, short carbon fibers and organic Add a mixture of fibers or organic powder (organic fiber or organic powder content: 5 to 50% by weight) so that it is slightly thicker than the depth of the groove, and roughly stack the laminate on top of it, Close the upper mold and heat at 100 to 200'C for several tens of minutes. Then, the organic matter binds the warp and weft of the carbon fiber fabric at their intersections, binds the short carbon fibers to each other at their intersections, and bonds the woven fabric and the short fibers at the interface. A so-called electrode plate material having a shape as shown in FIG. 1 is obtained.

Next, the above-mentioned electrode plate material is fired for several tens of minutes in an inert atmosphere such as nitrogen gas at a temperature of approximately 1000°C or higher to carbonize the above-mentioned organic matter and obtain a ribbed electrode plate according to the present invention. .

The electrode plate according to the present invention uses carbon fiber fabric for the substrate,
Furthermore, since the warp and weft yarns are bound together with carbide at their intersections, they are excellent in gas permeability, electrical conductivity, and mechanical strength.

That is, since woven fabrics have weave patterns determined by the weave structure, weave density, etc., high gas permeability can be obtained by selecting and using a woven fabric having an appropriate weave structure and weave density. In addition, the warp and weft of the woven fabric are crimped, and the carbon fibers extend from the front to the back and from the back to the front, and this forms a conductive path, so the warp and weft are bound with conductive carbide. Combined with this, the conductivity in the thickness direction is dramatically improved compared to when short fibers are used. Roughly speaking, woven fabrics have continuous fibers, and the warp and weft are interlaced in a U-shape pattern, so they have good shape retention, but in this invention, the warp and weft are bound together with carbide, making it durable. Your sexuality will further improve. Moreover, even if the binding caused by the carbide is broken by mechanical, electrical or chemical action, it will not fall apart unlike when short fibers are used.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing one embodiment of the electrode plate according to the present invention, and FIG. 2 is a schematic perspective view showing one unit of a stacked fuel cell using the electrode plate shown in FIG. 1 above. FIG. 1.2: Electrode plate 3: Electrolyte 4.5: Catalyst 6: Partition plate 7: Lip 8: Groove 9: Substrate 10: Carbon fiber fabric 11: Carbon fiber short fiber

Claims (1)

[Claims] An electrode plate comprising a large number of mutually parallel porous ribs provided on one surface of a porous substrate, wherein a carbon fiber fabric is used for the substrate, and the warp and weft of the carbon fiber fabric are intersected at their intersections. A ribbed electrode plate for a fuel cell, characterized in that the ribs are bound together with carbide, carbon fiber short fibers are used in the ribs, and the carbon fiber short fibers are bound together with carbide at their intersections.