JPS62276760A - Manufacture of complex electrode for fuel cell - Google Patents

Abstract

PURPOSE:To reduce the electrical resistance at the adhesive layer, by mixing a graphite powder to a thermosetting resin component as a carbonizing substance. CONSTITUTION:At both sides of a gas impermeable carbon thin plate, a porous carbon composition with penetrating hole group around its center of the thickness is attached integrally through a carbonizing substance, and then, a baking- carbonization process is given to produce a complex electrode for a fuel cell. In this manufacture process, to 100wt parts of a thermosetting resin initial condensate, a mixture of 30 to 70wt parts of graphite powder of mean particle diameter less than 80mum, 0.1 to 10wt parts of carbon fiber chops with the diameter less than 20mum and the length less than 1 mm, and 0.01 to 1 wt parts of a surface active agent is used. As the thermosetting resin initial condensate, a phenolic resin or a furan type resin with little residual carbon rate after the baking-carbonization is used.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a phosphoric acid fuel cell in which a porous carbon electrode plate and a gas-impermeable carbon separator plate are integrally formed. The present invention relates to a method of manufacturing a composite electrode for use.

``Prior art'' A fuel cell consists of a unit cell made by arranging a porous electrode plate supporting a catalyst and a gas-impermeable separator plate on both sides of a matrix layer holding phosphoric acid, and a large number of each unit cell. A predetermined stack structure is formed by connecting them in series. The shape of the electrode plate and separator plate can be divided into ribbed or flat plates depending on whether or not grooves are provided for gas flow for fuel and oxidizer.
Characteristics such as electrical conductivity, thermal conductivity, and ease of processing are required, and carbon materials are useful as materials that meet these required characteristics.

In this stack structure, in order to minimize the contact resistance between the electrode plates and separator plates, the entire stack must be firmly pressed and adhered, and the thickness of the electrode plates and separator plates must be adjusted to make the entire stack compact. It is necessary to make it thinner. However, since carbon materials do not have sufficient mechanical strength, they may be damaged during handling or battery assembly.

For these reasons, by integrally forming the porous carbon electrode plate and the gas-impermeable carbon separator temporary,
Attempts have been made to reduce contact resistance and increase mechanical strength to facilitate battery assembly. For example, the applicant proposed a method in which porous carbon electrode plates having a group of through holes approximately in the center of the thickness are integrally joined to both sides of a gas-impermeable carbon separator plate via a carbonizable material. (Tokugan Sho 6
O-290848). In this case, the carbonizable material used is an uncured carbon separator plate, an initial condensate of a thermosetting resin, or a mixture of the resin with fine powder such as coke, graphite, or glassy carbon.

"Problems to be Solved by the Invention" However, it is difficult to achieve both an increase in adhesive strength and a decrease in electrical resistance with the above-mentioned carbonizable material. In other words, the more resin components are advantageous in forming a strong adhesive layer, but this results in a relative increase in electrical resistance.On the other hand, blending fine graphite powder can prevent an increase in electrical resistance, but decreases adhesive strength. The problem is that there is a relative decline in

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

That is, in the present invention, a porous carbon molded body having a group of through holes approximately in the center of the thickness is integrally adhered to both sides of a gas-impermeable carbon thin plate via a carbonizable substance, and then fired and carbonized. In the method for producing a composite Ti electrode for a fuel cell, the carbonizable substance is 30 to 70 parts by weight of graphite powder with an average particle size of 80 μm or less based on 100 parts by weight of the thermosetting resin initial condensate;
0.1 to 10 parts by weight of carbon fiber chops with a diameter of 20 μm or less and a length of 1jIff or less and 0.01-I surfactant
This is a method for producing a composite electrode for a fuel cell, the structural feature of which is that it consists of a composition of an M placement part.

The porous carbon molded body is obtained by a method in which a composite of chopped carbon fibers and a thermosetting resin is sintered and carbonized.

For example, water-soluble phenolic resin and chopped carbon fibers are dispersed in water to form a slurry, and this slurry is injected into a mold of a predetermined shape, followed by pressure molding and heat curing. Ru. In this case, the through-hole group can be formed by inserting the rod-like body into a predetermined position in the mold and extracting the vaginal rod-like body after heat-hardening treatment. As the material of the rod-shaped body, metal, Teflon resin, or the like, which can be easily extracted from the molded and cured body, is used. Further, the slurry can also be formed using a papermaking method.

Gas-impermeable carbon thin plates are made by kneading graphite powder or coke powder, etc. whose particle size has been adjusted in advance, with a thermosetting resin liquid such as phenol or furan, molding the mixture, and then forming it into a thin plate of a predetermined thickness. It is obtained by roll rolling. This thin plate-shaped molded body is integrally bonded to the porous carbon molded body through a heat-curing carburizing substance. Then,
Composite 1 for fuel cells, in which a porous carbon electrode plate and a temporary gas-impermeable carbon separator are integrally joined by heating and firing in an inert atmosphere to carbonize! poles can be manufactured.

The present invention uses, as this carbonizable material, 30 to 70 parts by weight of graphite powder with an average particle size of 80 μm or less per 100 parts of the thermosetting resin initial condensate, and carbon fiber chopped with a diameter of 20 μm or less and a length of Law or less. A mixture of 1 to 10 parts by weight of surfactant and 0.01 to 1 part by weight of surfactant is used.

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

In this case, if the average particle size of the graphite powder exceeds 80 μm, the mechanical strength of the adhesive layer will decrease significantly. It is necessary to mix it in a proportion of 30 to 70 parts by weight.

Carbon fibers are composited to improve the strength of the adhesive layer.
In order to maintain the surface smoothness of the adhesive layer, it is necessary to use short ta fibers with a short fiber diameter and length.
0.1-m or less carbon fiber chop with a length of 1mx or less
It is blended in a proportion of 10 parts by weight. Further, it is important to suppress the amount of surfactant added in order to improve adhesive strength, and it is necessary to add the surfactant within the range of 0.01-1 mold extrusion.

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

"Example" 10 parts by weight of a water-soluble phenol resin (Priorfen J303 manufactured by Nippon Reichhold (Aji)) and 70 parts by weight of carbon were added to 20 parts by weight of water and stirred to uniformly disperse them to form a slurry. This slurry was injected into a mold fitted with a stainless steel rod, dried and pressure molded, and then
After heating and hardening at 0° C., the stainless steel rod was cooled and extracted.

In this way, a porous carbon electrode plate was manufactured, which was 150mm square, 2.3 mm thick, and had 30 through holes with a diameter Law approximately in the center of the thickness.

In addition, 100 parts by weight of liquid phenol resin was added to 100 parts by weight of artificial graphite powder with an average particle size of 5 μm, and the mixture was thoroughly kneaded.
This kneaded material was rolled, then molded into a flat plate, and then heated and hardened at 180°C for 3 hours to give a
A carbon separator plate having a size of 0 mm square and a thickness of 0.5H was manufactured.

As a carbonizable adhesive, 40.60 parts by weight of artificial graphite powder with an average particle size of 50 μm was added to 100 parts by weight of a phenolic resin initial condensate (PR940, manufactured by Sumitomo Durez Co., Ltd.), and carbon with a diameter of 16 μm, a length of 0, and 1 mm was added. Fiber chop 0.
5.3 parts by weight and 0.1 part by weight of diethyl dimethyl ammonium bromide as a surfactant were blended, and the mixture was sufficiently heated and kneaded to form a uniform paste. In addition, 2.5 parts by weight of para-toluene sulfonic acid chloride was added as a resin curing agent.

After this carbonizable adhesive was evenly applied to both sides of the surface separator plate, a porous carbon electrode plate was bonded with the through-holes perpendicular to each other, and pressure-cured for 12 hours at room temperature. The curing process was completed by heating at 180° C. for 3 hours. In this way, the temperature rises to 1100℃ at a heating rate of 5℃/h.
The temperature was raised to , and maintained for 3 hours to perform firing carbonization treatment.

The properties of this integrated composite were measured and shown in the attached table.

For comparison, an adhesive paste with the same composition as in the example was prepared without adding carbon fiber chops and surfactant, and an integrated bonded body was manufactured in the same manner, and its properties were as shown in the table. Also listed.

"Effects of the Invention" As is clear from the above explanation, by using the carbonizable adhesive of the present invention, it is possible to easily manufacture a composite electrode that maintains the electrical resistance at a low level while increasing the strength of the adhesive layer. Become. Therefore, it can greatly contribute to miniaturization and high efficiency of phosphoric acid fuel cells.

Claims (1)

[Claims] 1. A fuel cell composite in which a porous carbon molded body having a group of through holes approximately in the center of the thickness is integrally adhered to both sides of a gas-impermeable carbon thin plate via a carbonizable substance, and then fired and carbonized. In the method for manufacturing an electrode, the carbonizable substance has an average particle size of 80 μm based on 100 parts by weight of the thermosetting resin initial condensate.
30 to 70 parts by weight of the following graphite powder, 20 μm or less in diameter,
A method for producing a composite electrode for a fuel cell, characterized in that the composition comprises 0.1 to 10 parts by weight of chopped carbon fibers having a length of 1 mm or less and 0.01 to 1 part by weight of a surfactant.