JPS62198057A - Member for fuel cell - Google Patents

Abstract

PURPOSE:To reduce the contact resistance so as to be able to hold a high cell output by joining an electrode plate consisting of electro-conductive porous plate to a separator consisting of conductive metal plate at the upper ends of the projected ribs constructing grooves. CONSTITUTION:In an electrode plate 22 consisting of electro-conductive metallic porous plate metallic fine powder for constructing the electrode is holded in uniform distribution, and on the surface of the said plate 22 grooves 21 are previously provided for the pathway of fuel gas or oxidizing gas. As for the electrode metal for constructing such the electrode 22 some kinds of metallic fine powder commonly used for the electrode of a fused carbonate type fuel cell are suitable, e.g. nickel, nickel-chromium alloy or nickel-cobalt alloy and so on can be used desirably. The separator 23 is joined to the electrode plate 22 at the upper ends of the projected ribs 24 constructing the grooves 21, and as for the separator conventional separator materials e.g. stainless steel plate, nickel plate, nickel claded stainless steel plate and so on can be used usually.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to composite components for fuel cells, and in particular to electrodes, fuel gas or oxidizers for molten carbonate fuel cells. The present invention relates to a composite structural member having multiple functions as a gas passage, a current collector plate, and a separator.

(Prior art) In recent years, molten carbonate fuel cells, which use molten carbonate as an electrolyte and operate at high temperatures, have high power generation efficiency and can be used with many types of fuel, such as platinum. It is attracting attention because it does not require a precious metal catalyst, and high-quality waste heat is recovered for high-temperature operation, and its practical application is progressing.

A conventional representative example of such a molten carbonate fuel cell is shown in Section 3.
As shown in the figure. That is, a positive electrode 12 and a negative electrode 13 are stacked with an electrolyte plate 11 containing molten carbonate in between to form a single cell 14, and this single cell is made up of a current collector 15 and a quadrielectric separator 16.
A large number of layers are stacked together. In this way, the positive electrode of each unit cell is electrically connected to the negative electrode of the adjacent unit cell, thereby forming a molten carbonate fuel cell in which all the unit cells are connected in series. The separator 16 is normally provided with a groove 17 as a passage for fuel gas on one side, and a groove 18 as a passage for oxidizing gas on the other side. For example, hydrogen is supplied, and as oxidizing agents, for example, air and carbon dioxide gas are supplied to carry out a predetermined electrochemical reaction.

In such conventional molten carbonate fuel cells, the positive electrode is typically made by kneading fine nickel oxide powder with an organic binder and solvent as needed, and then using a cold press method or tape casting. A porous nickel oxide plate is used, which is formed into a plate shape by a method such as a nickel oxide method or a roll compression method, and then sintered at a high temperature to form a porous sheet with a porosity of, for example, about 60%. The negative electrode is a porous plate made by molding fine powder of a nickel alloy such as nickel-chromium or nickel-cobalt in the same manner as above, and then sintering it at high temperature under vacuum or in a hydrogen atmosphere. is used. Another known method is to uniformly fill a mold with fine metal powder and sinter it to obtain a porous metal plate as an electrode.

On the other hand, since separators are required to have high electrical conductivity, gas impermeability, and corrosion resistance, stainless steel or nickel-clad plates thereof have been conventionally used.

In the conventional molten carbonate fuel cell as described above, each of the above-mentioned components, namely, a positive electrode, an electrolyte plate, a negative electrode, a separator, and a current collector, are individually manufactured and then assembled in a predetermined order. Manufactured by laminating and assembling. However, the current collector may be omitted depending on the structure of the electrode or separator.

Therefore, in conventional molten carbonate fuel cells, even if each component is manufactured with high precision and assembled with good contact between each component, it is difficult to operate continuously for a long time. , each component undergoes non-uniform shape changes due to mechanical and thermal causes, such as expansion and contraction, and the contact resistance between each component gradually increases, thus leading to a decrease in battery output, Furthermore, it increases the heat generation of the battery.

In particular, the electrodes generally need to be about 1 day thick in order to downsize the battery volume and reduce internal resistance, and to activate the electrode reaction, the electrodes usually have a thickness of about 6
It is necessary to increase the porosity to about 0 to 70%, and on the other hand, in order to obtain the electromotive force required for a practical battery, it is necessary to form several dozen pieces into thin plates with an angle of 1 mm. However, the conventionally known electrodes as described above have low resistance to mechanical shock and are easily deformed, so they are easily damaged during battery assembly. Furthermore, during operation of the battery, it is necessary that the laminated state has sufficient strength against loads, thermal cycles, etc., and that shrinkage due to long-term heating is as small as possible.

However, conventional electrodes do not have satisfactory strength during operation, and are also subject to large deformation and shrinkage.

In addition, as mentioned above, high dimensional accuracy is generally required when manufacturing each component, but it is usually
, grooves are carved on the surface of the separator or electrode, but such processing also increases the dimensional accuracy requirements for manufacturing, and
This increases the number of battery manufacturing steps.

In addition, in conventional molten carbonate fuel cells, in order to obtain the voltage that is practically required, single cells are stacked in hundreds of layers, and each component requires several tens of layers. Since the batteries are also stacked, it is not easy to assemble and maintain the battery.

(Object of the Invention) As a result of intensive research in order to solve the various problems described above in molten carbonate fuel cells, the present inventors have discovered that some of the above-mentioned components including the electrode plate, namely the electrode plate. At the same time, we succeeded in obtaining an integrated composite component having multiple functions as at least a fuel gas and/or oxidant gas passage, as well as a current collector plate and a separator,
This has led to the completion of the present invention.

Accordingly, the present invention is directed to a composite component for fuel cells in general, and in particular to a composite component with multiple functions including electrodes for molten carbonate fuel cells. The purpose is to provide

(Structure of the Invention) A fuel cell component according to the present invention comprises an electrode plate made of a conductive porous plate having grooves carved on its surface for a fuel gas passage or an oxidant gas passage, and a conductive metal plate. It is characterized in that the electrode plate and the separator are joined at the upper edge of the protrusion forming the groove.

Hereinafter, the composite component for a fuel cell according to the present invention will be explained in detail.

The electrode plate used in the present invention has a conductive metal porous plate on which fine metal powder for forming the electrode is uniformly dispersed and supported, and a fuel gas passage or an oxidizing gas passage is preliminarily formed on the surface of the electrode plate. There are grooves carved into the surface.

The above-mentioned porous plate may be a porous plate made of a conductive metal material, such as a porous plate made of sintered metal, metal fiber, foamed metal, etc., or a porous plate whose surface is plated with a metal such as copper or nickel to make it conductive. A porous ceramic plate to which properties have been imparted, such as a sintered porous alumina plate, can be suitably used. Such a conductive porous plate usually has a porosity of about 50 to 90% and can be obtained as a commercial product. In particular, when used as an electrode in a molten carbonate fuel cell, the porous plate is preferably made of nickel or an alloy thereof, which has excellent conductivity, corrosion resistance, sintering resistance, etc. However, as will be described later, when used as a composite component that also serves as a positive electrode, for example, stainless steel may be used, and when used as a composite component that also serves as a negative electrode, for example, copper may be used.

The electrode metal used to construct such an electrode may be fine powder of a metal commonly used as an electrode for molten carbonate fuel cells, such as nickel, nickel-chromium alloy, nickel-cobalt alloy, etc. etc. are preferably used. However, the positive electrode may be made of nickel oxide, if necessary. Here, the thickness of the conductive porous plate is preferably as thin as possible, usually 0.3
The particle size of the electrode metal fine powder is preferably 1 to 20 μm, but is not limited to this.

Although the method for manufacturing such an electrode plate is not particularly limited, it is preferably manufactured by, for example, a blade method or a casting method.

In the blade method, a solvent and preferably an organic binder are added to the metal fine powder selected according to the electrode used, and if necessary, a deflocculant, a plasticizer, etc. are added, and the mixture is thoroughly mixed. , prepare a slurry. As the solvent, water is usually used, and therefore, as the organic binder, a water-soluble polymer such as polyvinyl alcohol, polyethylene glycol, carboxymethyl cellulose, or a derivative thereof is used.

Next, this slurry is cast onto, for example, a fluororesin-coated resin film, and the surface is shaped to have grooves using a grooved blade, and then dried to contain the fine metal powder and the fine electrode metal powder. Forms a thin sheet-like green body.

After this, a firing atmosphere is selected depending on the electrode to be used, and this is fired in a heating furnace to remove the solvent, binder, etc., and then sintered at a high temperature to form a porous material containing the electrode metal. A sintered plate can be obtained.

The amount of electrode metal fine powder in such a porous plate can be adjusted, for example, by appropriately selecting the concentration of the slurry and the thickness of the green body.

For example, a green body containing fine nickel powder as metal fine powder is obtained, and it is heated for 100 minutes in an oxidizing atmosphere such as air.
By firing at a temperature of 0° C. or higher for an appropriate period of time, a porous plate containing nickel oxide on the surface and therefore usable as a positive electrode can be obtained. Also,
A porous material that can be used as a negative electrode is prepared by preparing a green body containing fine metal powder, for example, nickel-chromium alloy powder, and sintering it at a temperature of 1000°C or higher in a hydrogen atmosphere or a vacuum atmosphere. You can get quality plates.

In addition, according to the casting method, fine metal powder selected according to the electrode used is uniformly filled into a mold having predetermined grooves.
An electrode plate can be obtained by sintering this in a heating furnace in a suitable atmosphere in the same manner as described above.

The composite component according to the present invention is thus formed by integrally joining an electrode plate having a groove on its surface and a separator to each other at the upper edge of the protrusion forming the groove of the electrode plate. There is.

FIG. 1 shows an example of a composite component for a fuel cell according to the present invention, including an electrode plate as described above.

That is, this component A has an electrode plate 22 on which grooves 21 are carved as fuel gas passages or oxidant gas passages.
A separator 23 is joined to the upper edge of the protrusion 24 forming the groove. As the separator, conventional separator materials such as stainless steel plates, nickel plates, and nickel-coated stainless steel plates can be used.

FIG. 2 shows another composite component according to the invention. In this component B, electrode plates 22 each having a groove 21 are joined to both sides of a separator 23. This component is used with one electrode serving as a negative electrode and the other electrode serving as a positive electrode. That is, in the battery, the negative electrode of one cell and the positive electrode of an adjacent cell are integrated with the separator 23 interposed therebetween. Therefore, by stacking these components with an electrolyte plate sandwiched between them, a battery can be constructed.

(Effects of the Invention) According to the composite structural member for fuel cells of the present invention, in the production of molten carbonate fuel cells, it is possible to significantly reduce the number of layers of individually separated structural members, and to Multiple components are joined together to improve strength, so even when the battery is operated for a long time,
It is possible to prevent deterioration of the contact condition due to non-uniform deformation of each component, and thus it is possible to reduce contact resistance and maintain high battery output.

In addition, in conventional molten carbonate fuel cells, the strength of the components, especially the electrodes, is insufficient, and great care is required when laminating and assembling other components. According to the composite component according to the present invention, since the electrode is integrated with the separator, the strength is high and furthermore, cracking due to thermal stress during use can be prevented. In addition, in the component according to the present invention, grooves as fuel gas or oxidant gas passages are already formed integrally with the electrode plate when molded, so these passages are formed on the surface of the electrode plate, as in conventional electrode plates and separators. There is no need to engrave it.

Furthermore, by using the component according to the present invention, as mentioned above, in the production of molten carbonate fuel cells, the number of assembled parts is reduced, so the dimensional accuracy in lamination is improved, and lamination and assembly are facilitated. Therefore, the efficiency of battery manufacturing can be increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of a composite component for a fuel cell according to the present invention, and FIG. 2 is a sectional view of a main part showing an embodiment of another composite component according to the present invention. , FIG. 3 is a partially exploded perspective view showing the main part configuration of a typical example of a conventional molten carbonate fuel cell. DESCRIPTION OF SYMBOLS 11... Electrolyte plate, 12... Positive electrode, 13... Negative electrode, 14... Cell, 15... Current collector, 16... Separator, 17... Fuel passage, 18... - Oxidizing agent passage, 21...Groove, 22...Electrode plate, 23...Separator, 24...Protrusion body. Figure 1 Figure 3] 5

Claims (3)

[Claims] (1) An electrode plate made of a conductive porous plate with grooves carved on its surface for a fuel gas passage or an oxidizing gas passage;
1. A fuel cell component comprising a separator that is a conductive metal plate, the electrode plate and the separator being joined at the upper edge of a protrusion forming the groove. (2) The fuel cell component according to claim 1, wherein electrode plates are bonded to both sides of the separator. (3) Claim 1, characterized in that the electrode plate contains nickel, nickel-chromium alloy, or nickel-cobalt alloy as the electrode metal, and the separator is a nickel plate, a stainless steel plate, or a nickel-coated stainless steel plate.
Section 2 or Section 2 Components for fuel cells.