JPS58100364A - Porous electrode plate for fuel cell - Google Patents

Abstract

PURPOSE:To improve the mechanical strength and the gas-diffusing performance of the flat part of an electrode plate, and increase the moldaility of the protruding parts of the electrode plate by making the length of carbon fibers contained in the flat part large than that of carbon fibers contained in the protruding parts. CONSTITUTION:At first, an aqueous dispersion liquid prepared by properly dispersing long carbon fibers 6A, is drawn through a filter so as to form a mat of the carbon fibers 6A on the filter. Next, after blocks are placed on parts of the mat of the carbon fibers A which correspond to gas flow paths 4, an aqueous dispersion liquid of short carbon fibers 6B is poured into spaces which correspond to projections 5, and filtered through both the above filter and the mat of the carbon fibers A so as to form mats of the carbon fibers 6B on the above mat of the carbon fibers 6A. Then, thus obtained body, after being dried, is impregnated with a binder 2 such as a phenol resin, and pressed and heated by heat press or something similar until the thickness of a flat part 3 and the height of the projections 5 become given dimensions so as to harden the binder 2. After that, thus obtained body is sufficiently carbonized by being heated at high temperature in an atmosphere of an inactive gas or in vacuum, thereby making a porous electrode plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a porous electrode plate for a fuel cell, and more particularly, to a porous electrode plate for a fuel cell in which vertical fibers and a binder are applied to the lining.

As porous electrode plates for fuel cells, those shown in FIGS. 1 and 2 are known.

In the former, carbon powder I is used as the main material, a binder 2 such as a phenol resin is mixed therein, and the binder 3 is hardened and bonded using a heat press or the like to form a flat plate Ils and a gas passage 4 on one side thereof. After a plurality of central stripes S are integrally molded, this is then ferruled at a high temperature. However, this electrode plate had the disadvantage that it was not only very brittle because the carbon $1 itself had a low**, but also that it was too dense, resulting in insufficient gas diffusion and low battery efficiency.

On the other hand, the latter uses carbon fiber 6 as the main material,
If carbon fibers 6 of 10 or more are used, sufficient mechanical strength can be obtained as electric fiI[, but since the long carbon fibers become an obstacle to molding, the flat plate part 3 and the plurality of protrusions are directly pressed using a heat press or the like. It is extremely difficult to form an electric aW with four concavo-convex shapes made of strips ss. Therefore, when using such long carbon fibers, first make a thick flat plate, and then cut the gas flow path 4 to form an uneven electrode consisting of the flat plate part 3 and a plurality of layers *III. Must be formed into a board. However, this cutting process is extremely troublesome and requires a large number of manufacturing man-hours, and when a flat plate is made mainly of long carbon fibers, the carbon fibers tend to line up parallel to the plate surface, making it difficult to make a straight line at right angles to the plate INK. Since the number of carbon fibers extending in the gas passage is relatively small, there is a drawback that the due south lls is easily chipped on both sides thereof, that is, on the wall surface of the gas passage 4 formed by cutting.

Even when carbon fiber 6 is used as the main material, it is possible to form an uneven electrode plate directly using a heat press or other K without cutting if the short fibers are less than 1 cm in size, but the entire Not only does the mechanical strength become lower, but the apparent density becomes higher and becomes denser than 1tK, which impairs gas diffusion. Further, when the fiber size is in the range of 1 to 10 cm, the gas diffusivity is relatively good, but the mechanical strength is insufficient and the moldability by K such as heat press is also poor.

The relationship between the length of such carbon fibers, moldability, gas diffusivity, and mechanical strength is shown in FIG. 3. In No. **, characteristic line X indicates strength, Y indicates gas diffusivity, and 2 indicates mechanical stiffness.

The purpose of this project is to provide a porous electrode plate for fuel cells that has excellent gas diffusivity and mechanical strength and can be easily molded.

In order to achieve this objective, the present invention has developed a porous electrode for fuel cells, which is made by carbonizing carbon fibers and a binder and integrally layering a flat plate part and a plurality of protrusions forming gas flow paths on one side of the warp. In the plate, the length of the carbon fibers located within the flat plate portion is made longer than the length of the carbon fibers located within the protrusion, thereby improving mechanical strength and gas diffusivity in the flat plate portion, and improving the protrusion. It is characterized by easy moldability in the strips.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

No. 411m is a sectional view of an electrode plate according to an embodiment of the present invention.

In this embodiment, long fibers m8A are used as the carbon fibers located in the flat plate part 3, which can provide the mechanical strength and gas diffusivity required for the electrode plate, and the protrusion part 5 forming the gas flow path 4 is used. As the carbon fibers located inside, short fibers 6B are used, which have good moldability and have a sufficiently low electrical resistance for the machine to easily extract the electromotive force of the electrodes to the outside.

Such an electrode 11 can be manufactured as follows, for example, by a filtration molding method. First, a dispersion aqueous solution in which long carbon fibers-6A are appropriately dispersed is filtered through a filter.
A matte layer of carbon fiber 6A is formed on the filter. Next, after placing the wires at the positions corresponding to the gas flow paths 4 on the mat of six carbon fibers, in the space between these wires, that is, the space corresponding to the protrusions 5, in the same manner as described above, short carbon fiber 6B
An aqueous dispersion solution of carbon fiber Ji16A is injected and filtered through a filter and a mat of carbon fiber Ji16A that has already been formed.
A mat of carbon fibers 6B is formed in a laminated state on the mat of A. As a result, the long carbon fibers 6 constituting the flat plate portion 3
A human mat and a mat of short carbon fibers 6B forming the plurality of protrusions S laminated on one side of the mat are completed. After drying this, it is impregnated with a binder 2 such as phenol resin, and then pressurized using a heat press or the like so that the thickness of the flat plate part 3 and the height of the protruding part 5 become the predetermined dimensions. The binder 2 is heated to harden, and further heated at high temperature in an inert gas or vacuum to be sufficiently carbonized to form a porous electrode plate.

According to the inventor's experiments, the length of the six long carbon fibers is 2 to 30 m, and the length of the short carbon fiber 6B is 0.1 to 1 m, and soo'c or more is sufficient. Carbonized ones were good.

Also, the diameters of carbon fibers 6A and 6B are both 10
A value of ~30μ is good; if this range is exceeded, problems such as clogging of the filter during filtration or the difficulty in adjusting the thickness during fabrication of the fibers occur because the elasticity of the fibers themselves is too strong.

First, a specific example of this embodiment will be described.

Adult example 1: Straw as 6 carbon fibers of flat plate s3,
Carbon fiber embroidery with a diameter of 12#, carbon fiber 11 on the protrusion 5
A mat with a thickness of 2 cm was made using a carbon fiber fabric with a length of 0.7 cm and a straight @ 12 μ as 16B, and phenol lI was added to this mat.
M120X was added, the resin was cured, and then carbonized and fired in soo'c. The electrode plate obtained in this way has a density o, 5p/c
d, bending strength 1[2 (IP/d, electrical resistance 0.10-1, bending strength 6 compared to conventional example using carbon powder as main material)
The battery efficiency is doubled and the battery efficiency is 10! In addition, the number of manufacturing steps was significantly reduced compared to the conventional example in which carbon fiber was used as the main material and the gas flow path was formed by cutting.

Specific example 2: carbon fiber 6A of flat plate s3, length 20cm,
Carbon fiber with a diameter of 20μ, carbon 11 on the protrusion 6B! m6B
An electrode plate was made in the same manner as in Example 1 using 1R* fiber (length: 0.4 m, diameter: 12 AI). This electrode plate has a bending strength of 30 mm/-, which is further 50 mm than that of Example 1.
%, and the battery efficiency was further improved by 5X compared to Example 1. Other characteristics and manufacturing steps were the same as in Example 1.

FIG. 5 is a sectional view of an electrode plate according to another embodiment of the present invention.

In this embodiment, the carbon fibers in the flat plate part 3 are composed of two layers, and the carbon fibers 6B in the protruding strip part 5 and the carbon fibers 6A in the anti-central striation layer in the flat plate part 3 are each in the fourth layer. Using the same carbon fiber as in the embodiment shown in the figure, the carbon fiber of the layer on the protrusion side of the flat plate part 3 is used. * As 6C, the diameter is larger than the carbon fibers 6'A and 6B, and the length is shorter than the carbon fiber 6 and longer than the carbon fiber 6B.

As a specific example, the carbon fibers 6A and 68 are the same as those in Specific Example 1, and the carbon fiber 6C has a length of 5 cm.
, carbon fibers with a diameter of 20μ were used.

Such an electrode plate is also made by doffing, in which a carbon fiber 6C 11II solution is injected and filtered onto a carbon fiber 6A mat that has already been formed with a filter to form a carbon*6C mat in a laminated state. By simply adding it, it can be manufactured in the same manner as the above-mentioned method for manufacturing the a4'ejA electric ma.

In the twelfth embodiment, in addition to the effects similar to those of the previous embodiment, the following effects can also be obtained. That is, when the electrolytic solution in the electrolyte placed on the side opposite to the protruding part of Senbin S30 is sucked up by the capillary phenomenon between the carbon fibers in the electrode plate, the part of the flat plate part 3 on the protruding part side has a large diameter. Since a larger space is formed between each carbon fiber 60 than in other parts, the suction force due to capillary action in this part becomes weaker. As a result, it is possible to prevent the electrolyte from being excessively drawn up from the electrolyte to the electrode plate, and to significantly extend the liquid retention life of the electrolyte, that is, the life of the battery.

As explained above, according to the present invention, carbon l/1. Since long fibers were used as the can and short fibers were used as the carbon fibers located in the protrusions, the mechanical strength and gas diffusivity of the electrode plate could be improved, and the protrusions could be easily formed. It becomes possible to manufacture an electrode plate with fewer man-hours without requiring cutting.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views showing each side of a conventional porous electrode plate, and Figure 3 is a characteristic showing the relationship between carbon fiber length, formability, gas diffusivity, and mechanical strength in a porous electrode plate. 4 and 5 are cross-sectional views of porous electrode plates according to embodiments of the present invention. 2... Binder, 3... Flat plate part, 4...
...Gas flow path, G... Protrusion, 6A...
...Long carbon fiber, 6B...Short carbon fiber,
6C...Thick carbon fiber. 1,''゛,゛1'1 Fig. 722 73 Difficult-m Young long-wood 41ml ``75FjrX

Claims (1)

[Scope of Claims] 1. A porous electrode for fuel cells in which carbon fibers and a binder are carbonized to form a flat plate part and a plurality of central grooves that constitute gas flow paths in 70 pieces. Porous electricity purchase fiII for fuel cells [411 image] in which the length of the longitudinal fibers located within the 1,000 ag is longer than the length of the carbon fibers located within the protrusions. 2, II Permission Request No. 118, Paragraph 1, it is stated that the longitudinal fibers located in the flat plate portion are thicker than the carbon fibers located in the protrusion portion (4111). Electricity 1i1E. 3. In a porous electrical plate for ms batteries, in which a flat plate part and a plurality of central parts forming gas flow channels 41 are integrally formed on one side of the flat plate part by combining carbon iron and a binder, - If the length of the carbon fibers located in the ligating part is longer than the length of the longitudinal fibers located in the ridge part,
A porous material for fuel cells, characterized in that the poles of the vertical fibers located in the vI & komebe part of the plate part are made thicker than the carbon fiber poles located in the anti-central part of the flat plate part. Electrode plate. 4. In claim 3, the length of the longitudinal fibers located in the protruding part @ part of the flat plate part is - the #lts fiber located in the opposite part of the flat plate part on the side of the protruding part. A porous electrode plate for fuel cells that has a shorter length than the original length.