JPH0626128B2 - Method for manufacturing composite electrode for fuel cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a composite electrode for a phosphoric acid fuel cell in which a porous carbon electrode plate and a gas impermeable carbon separator plate are integrally formed. .

"Prior Art" A fuel cell is a unit cell in which a porous electrode plate carrying a catalyst and a gas impermeable separator plate are arranged on both sides of a matrix layer holding phosphoric acid to form a unit cell, and a large number of each unit cell is formed. By connecting in series, a predetermined stack structure is formed. The shape of the electrode plate and the separator plate is divided into ribbed or flat plates depending on whether or not the gas flow grooves of the fuel and the oxidant are provided, but these members have heat resistance, corrosion resistance,
Properties such as electrical conductivity, thermal conductivity, and easy processing method are required, and carbon materials are used as those satisfying the required properties.

In this stack structure, the entire stack should be firmly clamped and adhered in order to minimize the contact resistance between the electrode plate and the separator plate, and the thickness of the electrode plate and the separator plate should be reduced in order to further reduce the overall size. Is required to be thin. However, since the carbon material has insufficient mechanical strength, it may be damaged during handling or battery assembly.

For this reason, by integrally forming the porous carbon electrode plate and the gas impermeable carbon separator plate,
Attempts have been made to facilitate battery assembly by reducing contact resistance and increasing mechanical strength. For example, the applicant has proposed a method of integrally joining a porous carbon electrode plate having a group of through holes at approximately the center of the thickness to both surfaces of a gas impermeable carbon separator plate via a carbonizing material. (Japanese Patent Application Sho 6
0-290848). In this case, as the carbonizing substance, an uncured carbon separator plate, an initial condensate of a thermosetting resin, or a resin in which fine powder such as coke, graphite or glassy carbon is mixed is used.

"Problems to be Solved by the Invention" However, it is difficult for the above-mentioned carbonizable substance to achieve both an increase in adhesive strength and a decrease in electrical resistance. That is, the more the resin component is, the more advantageous it is to form a strong adhesive layer, but the electrical resistance is relatively increased. On the other hand, the addition of graphite fine powder can prevent the electrical resistance from increasing. Is relatively low.

"Means for Solving Problems" The present invention aims to solve the above problems and improve the adhesive strength and electric resistance of the adhesive layer.

That is, according to the present invention, a porous carbon compact having a through-hole group at approximately the center of its thickness is integrally adhered to both surfaces of a gas-impermeable carbon thin plate through a carbonizing substance, and then subjected to firing carbonization treatment. In the method for producing a composite electrode for a fuel cell, 30 to 70 parts by weight of graphite powder having an average particle size of 80 μm or less and a diameter of 20 μm are used with respect to 100 parts by weight of a phenol-based or furan-based thermosetting resin initial condensate in the carbonaceous material. A method for producing a composite electrode for a fuel cell, which is characterized in that the composition comprises 0.1 to 10 parts by weight of a carbon fiber chop having a length of 1 mm or less and 0.01 to 1 parts by weight of a surfactant.

The porous carbon molded body is obtained by a method in which a composite of carbon fiber chops and a thermosetting resin is subjected to firing and carbonization treatment.
For example, it is manufactured by dispersing a water-soluble phenolic resin and a carbon fiber chop in water to form a slurry, injecting the slurry into a mold having a predetermined shape, followed by pressure molding and heat curing treatment. In this case, the through-hole group can be formed by inserting the rod-shaped body at a predetermined position in the mold, and extracting the rod-shaped body after the heat curing treatment. As a material for the rod-shaped body, a metal, tetrafluoroethylene resin, or the like that can be easily extracted from the molded and hardened body is used. Further, the slurry can be molded by using a papermaking method.

A gas-impermeable carbon thin plate is a thin plate with a predetermined thickness after kneading graphite powder or coke powder whose particle size has been adjusted in advance with a thermosetting resin liquid such as phenol or furan, and kneading the mixture or molding. It is obtained by roll-rolling. This thin plate-shaped molded body is integrally attached to the porous carbon molded body via a heat-curable carbonizing substance. Then
A composite electrode for a fuel cell in which a porous carbon electrode plate and a gas impermeable carbon separator plate are integrally joined can be manufactured by heating in an inert atmosphere and firing and carbonizing.

In the present invention, as the carbonizing substance, 30 to 70 parts by weight of graphite powder having an average particle size of 80 μm or less, carbon fiber chops having a diameter of 20 μm or less and a length of 1 mm or less are used per 100 parts by weight of the thermosetting resin initial condensate. 1-10 parts by weight and surfactant
Use a mixture of 0.01 to 1 part by weight.

As the thermosetting resin initial condensate used in the present invention, it is preferable to use a phenol-based or furan-based resin having a high residual carbon rate after firing and carbonization. Further, as the graphite powder to be mixed, either artificial graphite or natural graphite can be used, and the carbon fiber chop can be graphite fiber chop. As the surfactant, any of cations, anions, neutral surfactants and the like may be used.

In this case, when the average particle size of the graphite powder exceeds 80 μm, the mechanical strength of the adhesive layer is greatly reduced, and in order to maintain the conductivity and the electric resistance at a low level and to maintain the mechanical strength, It is necessary to blend in a proportion of 70 parts by weight.

The carbon fibers that are combined to improve the strength of the adhesive layer are
In order to maintain the surface smoothness of the adhesive layer, it is necessary to use short fibers having a short fiber diameter and length, and the diameter is 20 μm.
Below, carbon fiber chops with a length of 1 mm or less are 0.1 to 10
It is compounded in a ratio of parts by weight. Further, it is important to suppress the amount of the surfactant added to improve the adhesive strength as small as possible, and it is necessary to add it within the range of 0.01 to 1 part by weight.

[Operation] In the present invention, by blending a graphite powder into a thermosetting resin component as a carbonizing substance, the electrical resistance of the adhesive layer is reduced, and the mechanical strength is reduced by combining carbon fiber chops. Is effectively prevented by. Furthermore,
The added surfactant increases the interfacial adhesion performance between the electrode plate and the separator plate and functions to improve the adhesion strength.

"Example" 10 parts by weight of a water-soluble phenolic resin (Priiophen J303 manufactured by Reichhold Japan Ltd.) and 70 parts by weight of carbon fiber chop (average diameter 10 µm, average length 8 mm) were added to 20 parts of water.
It was added to the parts by weight and stirred, and uniformly dispersed to obtain a slurry. This slurry was poured into a mold having a stainless rod-shaped body inserted therein, dried and pressure-molded, then heat-cured at 140 ° C., and then cooled to pull out the stainless rod. In this way, a porous carbon electrode plate having a 150 mm square, a thickness of 2.3 mm, and 30 through holes having a diameter of 1 mm at approximately the center of the thickness was manufactured.

Further, 100 parts by weight of a liquid phenol resin was added to 100 parts by weight of an artificial graphite powder having an average particle size of 5 μm and sufficiently kneaded,
This kneaded material is rolled and then molded into a flat plate by molding, followed by heat-curing treatment at 180 ° C. for 3 hours.
A carbon separator plate having a size of 0 mm square and a thickness of 0.5 mm was manufactured.

As a carbonizing adhesive, 40 or 60 parts by weight of artificial graphite powder having an average particle size of 50 μm and 100 parts by weight with respect to 100 parts by weight of a phenol resin initial condensate (PR940, Sumitomo Dures Co., Ltd.)
Carbon fiber chops of 6 μm and length of 0.1 mm are 0.5, 3
By weight, diethyl dimethyl ammonium bromide as a surfactant was mixed in a proportion of 0.1 part by weight, and the mixture was sufficiently heated and kneaded to prepare a uniform paste. As a resin curing agent, paratoluene / sulfonic acid chloride was added to 2.5
Added in parts by weight.

This carbonizing adhesive was uniformly applied to both sides of the separator plate, and then the porous carbon electrode plates were adhered so that the groups of through holes were orthogonal to each other, and pressure-bonded and cured at room temperature for 12 hours, then 180 The curing treatment was completed by heating at 0 ° C. for 3 hours. The integrated joined body thus obtained was placed in a crucible made of graphite, the periphery was covered with coke packing, and then the temperature was raised to 1100 ° C. at a heating rate of 5 ° C./h in an electric furnace.
It was held for a period of time for carbonization treatment by firing.

Various properties of this integrated joined body were measured and shown in a separate table.

For comparison, a carbon fiber chop and a surfactant were not blended, except that an adhesive paste having the same composition as that of the example was prepared, and an integrated joined body was produced by the same method, and its characteristics are shown in the table. Also described in.

"Effects of the Invention" As is clear from the above description, by using the carbonizing adhesive of the present invention, it is possible to easily manufacture a composite electrode in which the strength of the adhesive layer is increased and the electric resistance is kept low. Become. Therefore, the phosphoric acid fuel cell can be greatly contributed to miniaturization and high efficiency.

Claims (1)

[Claims] 1. A fuel which is integrally carbonized on both sides of a gas-impermeable carbon thin plate and has a through-hole group at approximately the center of its thickness through a carbonizing substance, and is then calcined and carbonized. In the method for producing a composite electrode for a battery, the carbonizable substance is 30 to 70 parts by weight of graphite powder having an average particle size of 80 μm or less, and a diameter of 20 μm or less with respect to 100 parts by weight of a phenol- or furan-based thermosetting resin initial condensate. A method for producing a composite electrode for a fuel cell, which comprises a composition of 0.1 to 10 parts by weight of carbon fiber chops having a length of 1 mm or less and 0.01 to 1 parts by weight of a surfactant.