JPS58129770A - Electrode for molten salt fuel cell - Google Patents

Abstract

PURPOSE:To obtain an electrode not deformed even when sintered under the atmosphere further provided with large strength, by using a metallic porous body and metal powder used with said porous body as a framework, filled and sintered in an air gap of the porous body. CONSTITUTION:A porous body consisting of metal is used as a framework. This porous body is manufactured in such a manner that metal is plated to foaming resin such as, for instance, foaming polyurethane and then the foaming resin is removed, and the porous body with at least 80% preferably 90-98% porosity is used. For the metal used here, higher heat resistance and stength can be obtained in case of using especially a porous body of nickel chrome alloy. After filling metal powder in such a porous body, sintering is performed normally under a reducing atmosphere of hydrogen or inactive atmosphere of nitrogen, argon, etc. at temperature of 750-1,100 deg.C. In this treatment, a threedimensional net shaped porous body and metal powder are integrally formed, and an electrode not deformed under an operational condition of a molten salt fuel cell further provided with large strength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode for a molten salt fuel cell.

Recently, fuel cells used for power generation have been actively developed, and increasing the capacity of molten salt fuel cells is being considered.

A molten salt fuel cell is constructed by stacking unit cells as shown in FIG. In this figure, 1 and 7 are end plates, and in order to increase the capacity of the fuel electrode side spacer 2 and fuel electrode 3, which also serve as current collectors between these end plates 1 and 7, large electrodes are required. However, large electrodes are easily deformed and there are many problems in manufacturing ones with high strength. That is, when the electrode is deformed during operation, the contact resistance between the electrode and the current collecting surface increases, resulting in a decrease in performance. In some cases, there is still a risk of clogging the gas flow path. Indeed, low electrode strength can even lead to catastrophic failure of sintered or felted electrode structures. For this reason, attempts have been made to strictly control the sintering conditions of the electrode, to use a wire mesh as a skeleton, etc., but it has not yet been possible to obtain an electrode sufficient to solve the problem.

The present invention aims to eliminate these problems and provide a large-sized molten salt fuel cell electrode that does not undergo deformation and has high strength. It is characterized by having a skeleton and metal powder filled and sintered into the voids thereof.

In the present invention, a porous body made of metal is used as the skeleton. This porous body is manufactured by, for example, plating a metal on a foamed resin such as foamed polyurethane, and then removing the foamed resin, and has a porosity of 80% or more, preferably 90 to 98%.
are used. If the metal used here is nickel or nickel, higher heat resistance and strength can be obtained. The porous body thus produced has pores in at least three directions of the plane. In many cases, holes are formed in at least three directions, even in two directions below the plane. It can be said to be a porous material with pores facing in all directions. Such porous bodies are collectively referred to as three-dimensional network porous bodies, which are filled with metal powder and then sintered, but sintering is usually carried out in a hydrogen-reducing atmosphere or an inert atmosphere such as nitrogen or argon. Temperature 750-1100C under active atmosphere
It will be held in Through this treatment, the three-dimensional network porous body and the metal powder are integrated, and an electrode that does not deform under the operating conditions of a molten salt fuel cell and has high strength can be obtained. Note that instead of performing the sintering treatment in a hydrogen-reducing atmosphere or an inert atmosphere, it can also be performed in an air atmosphere.

Generally, when metal powder is sintered in an air atmosphere, the metal powder is oxidized, making it impossible to obtain a strong sintered body, that is, an electrode. Unfortunately, during the operation of a molten salt fuel cell, the cathode, the oxygen electrode of the cell, is itself continuously oxidized, and this oxidation reaction slows down rapidly, and in some cases, the electrode collapses. Therefore, methods are used to prevent electrode oxidation by sintering in a hydrogen-reducing atmosphere or inert atmosphere, and treating the sintered electrode with lithium salt or forming a spinel-type surface with nickel oxide and cobalt oxide. However, in the case of the present invention, even without such oxidation prevention treatment, the material does not deform not only when sintered in a hydrogen-reducing atmosphere or an inert atmosphere, but also when sintered in an atmospheric atmosphere. Moreover, an electrode with high strength can be obtained.

When the electrode thus obtained was used as an oxygen electrode, good results were observed in terms of both battery performance and life.

Next, implementation U will be explained.

Example 1 A three-dimensional network porous body made of nickel or nickel-chromium association is filled with metal powder made of nickel, iron, or iron-titanium alloy, and sintered under the conditions shown in Table 1 to a thickness of 1.5 mm.
Samples A1 and 2 in the same table are the conventional ones shown for relative softness, and the bending strength at the start of deformation in the case of the example is the same as that of the conventional one. This shows that the strength is significantly higher than that in the case.

Example 2 A performance test of a molten salt fuel cell was conducted at an operating temperature of 650C using the 'a electrode made in the same manner as in Example 1. When the test was conducted using the conventional electrode area of sample A1, at the beginning of the test there was one voltage o, sv, ゛g flow density 100 mA/c1n2, but after 50 hours after the start So, heavy pressure O, SVX current density 50mA-/cm
It dropped to 2. When this battery was disassembled and examined, it was found that part of the electrode had collapsed, and the damage was blocking the reactant gas flow path. On the other hand, sample number 3 is considered to be negative,
When the test was carried out using sample reports 4 to 7 as gruesome, when samples 4 and 5 using nickel as the gold wire powder were used, the voltage was O and SV during 100 hours of continuous operation.

It exhibited performance at a current density of 100 mA/crn2. It's a moat, a sample shop that uses iron-titanium and iron as metal powder 6
-7, in 100 hours of continuous operation, the performance was inferior to samples JP6.4 to 5; however, low voltage 0.8VX current density of 85 mA/cm2 was maintained.

After testing, these batteries were disassembled and examined (7). No structural deterioration was observed in either case.

Example 3 Using the conditions shown in Table 1 of Example 1, a size of 100
A large electrode with a size of 0 mm x 10100 O and a thickness of 1.5 wn was manufactured. Samples using the conditions of samples A1 and A2 shown as comparative examples were deformed during the compacting operation, and cracks were observed in some parts, but samples using the conditions of samples A3 to A7 were not sintered. No deformation occurred during the tying operation, and no cracks were observed, indicating that it is possible to manufacture large electrodes.

As described above, the electrode for a molten salt fuel cell according to the present invention makes it possible to provide a large-sized electrode with high strength without causing deformation, and is an industrially effective dog.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the constituent elements of a unit cell of a molten salt fuel cell. ■, 7... End plate, 2... Fuel electrode side spacer (also serves as current collector), 3... Fuel electrode, 4... Electrolyte plate, 5...
... Air electrode, 6... Air electrode side spacer (also serves as current collector). Agent Patent attorney Hiroo Nagasaki (8) (and 1 other person) [Eng.

Claims (1)

[Scope of Claims] 1. An electrode for a bath-molten salt fuel cell characterized by comprising a metal porous body and a metal powder using the porous body as a skeleton and filling and sintering the voids of the porous body. . 2゜After the porous body deposits metal on the surface of the foam,
The electrode for a molten salt fuel cell according to claim 1, wherein the foam is decomposed and removed. 3. The electrode for a molten salt fuel cell according to claim 1 or 2, wherein the metal is nickel or a nickel-chromium alloy.