JPH02132763A - Fused carbonate type fuel cell - Google Patents

Abstract

PURPOSE:To extend the life of a cell and enhance the performance of the cell, by using an alloy containing Ni, Mn, Fe, Si, S, C, and Cu in a specific ratio by weight to form at least one kind of components i.e., an electrode reinforcing member, a current collecting plate and a separator. CONSTITUTION:At least one kind of components i.e., a separator 5, a current collecting plate 4, and an electrode reinforcing member 8 is made of a material the main component of which is NiCu containing 63.0 to 70.0% of Ni, less than 2.5% of Mn, less than 2.5% of Fe, less than 0.5% of Si, less than 0.024% of S, less than 0.3% of C and Cu for the rest. This material is not only as excellent in its molten-salt resisting performance under anode gas corrosion conditions as pure Ni, pure copper, but also is high in its high-temperature strength and besides its electric resistance is as high as half the electric strength of austenite type stainless steel; it has therefore excellent characteristics of a cell member. Problems such as consumption of carbonate due to generation of scale oxide, and increase of electric resistance, are hence restrained. The life of the cell can thus be extended and also the performance of the cell enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel molten carbonate fuel cell, and particularly to a molten carbonate fuel cell suitable for obtaining a high performance, long-life battery.

[Conventional technology]

In recent years, research and development of energy-saving equipment has become an important issue in response to oil resource issues. On the other hand, LN
Molten salt fuel cells that use G and coal gas aim to save energy and replace oil, and are a thermal power generation technology that is part of new energy development.

FIG. 1 shows the basic configuration of a molten carbonate fuel cell. A current collecting plate 4 is disposed on both sides, and a separator 5 is disposed on both sides of the Hayabusa current plate 4.

A perforated plate is used as the current collector plate 4. Moreover, a plurality of groove-shaped gas flow paths are formed in the separator 5.

Molten salt fuel cells are made using lithium carbonate (LizcO).
a) and an alkali metal salt such as potassium carbonate (KxcO3) as an electrolyte. 600-75 above its melting point
This is a fuel cell that operates in a temperature range of 0°C. The battery generates electricity by supplying hydrogen or hydrogen-containing gas as a fuel to the anode side and supplying air and decacarbonate gas as an oxidizing agent to the cathode side, and the following electrochemical reaction proceeds: .

Anode (hydrogen electrode): 2Hz+2Co8→C. 022
-+2HzO+4e″″ ・(1) Cathode (air electrode): Oz+2COz+4 e→2C
Oa2- (2) That is, hydrogen and carbonate ions at the anode react to generate water and carbon dioxide gas, and release electrons to the external circuit. On the other hand, at the cathode, oxygen and carbon dioxide gas react with electron ions from an external circuit to generate carbonate ions.

Here, the current collector plate 4 has the role of collecting the generated electricity, and the separator 5 has the role of taking out the electricity collected by the current collector plate 4 to the outside.

FIG. 2 shows the cross-sectional structure of the electrode. The electrode is formed of a Ni sintered body, and a wire mesh-like electrode reinforcing material 8 is contained inside the electrode to reinforce the electrode.

FIG. 3 shows the basic structure of a molten carbonate fuel cell. The separator 5 is a thin plate processed into a corrugated shape, and a gas flow path 9 is secured therein. In such a battery structure, a compressive force 11 is applied from the outside in order to prevent leakage of anode gas and cathode gas from the seal portion 10.

(Problems to be Solved by the Invention) Molten salt adheres to the surfaces of the current collector plate 4 and the separator in FIG. 3 and the electrode reinforcing material 8 in FIG. 2 during operation, and they are heated to 650°C. , are exposed to extremely severe corrosive environments.For this purpose, stainless steel such as SOS3161Q is generally used from the viewpoint of corrosion resistance.

However, even stainless steel is subject to significant corrosion in the above environment. In particular, corrosion is significant on the anode side, which is in an environment of hydrogen, carbon dioxide, and water vapor.

However, when the current collector plate 4, the separator 5, and the electrode reinforcing material 4 corrode, the electrolyte is absorbed by the corrosion products, resulting in loss of the electrolyte. Therefore, there is a problem of shortening the battery life.

Further, since the corrosion products have high electrical resistance, for example, if the separator is severely corroded, electrical contact loss occurs between the separator and the current collector plate 4, which causes a decrease in output.

An object of the present invention is to provide a molten carbonate fuel cell in which the separator 5, current collector plate 4, and electrode reinforcing material 8 have improved high-temperature corrosion resistance.

[Means to solve the problem]

The battery anode corrosion environment was simulated using commercially available austenitic and ferritic stainless steels, Ni-based alloys, iron-based alloys, Co-based alloys, carbon steel, pure copper, and pure Ni. Molten salt resistance test was conducted in the environment. As a result, it was found that pure copper and pure Ni showed almost no corrosion and had significantly superior melting resistance compared to other alloy materials.

However, pure Cu and pure Ni cannot be used for the separator 5, current collector plate 4, and electrode reinforcing material 8 because of their low high-temperature strength. This is because when the external compression pressure 11 shown in FIG. 1 is applied to the entire battery, stress also acts on the separator 5, the current collector plate 4, and the electrode reinforcing material. For example, if the high-temperature strength of the separator 5 is low, the waveform will collapse, and not only will the gas flow path 9 not be secured, but the current collector plate 4, electrode 2, and electrolyte plate 1 will also collapse, making it impossible to generate electricity. becomes.

Therefore, the present invention was achieved based on the knowledge obtained from the above basic experiments.

[Effect]

An alloy of Ni and copper is used to take advantage of the extremely excellent corrosion resistance of pure Ni and pure copper and to further increase high-temperature strength. Ni and copper form a complete solid solution and have high high temperature strength.

The present invention is a molten carbonate fuel cell in which a Ni--Cu alloy is applied to an anode side separator, a current collector plate, and an electrode reinforcing material. This Ni-based alloy containing Cu is especially JIS standard H366
1,3261 is preferred, with Cu remaining and Ni63.
0 to 70.0%, Mn 2.5% or less, Fe 2.5% or less, Si 0.5% or less, S 0.024% or less, C0.
It is a material whose main components are Ni and Cu, with a content of 3% or less.

This material not only has excellent molten salt resistance in an anode gas corrosive environment, similar to that of pure Nil copper, but also has high high temperature strength and has a lower electrical resistance than 172% of the conventionally used austenitic stainless steel. It has excellent properties as a member for molten salt fuel cells.

The battery of the present invention has a separator 5 as shown in FIG.
It is preferable that the outer frame 6 and the outer frame 6 are joined by brazing. This is because mechanical contact caused by the pressure 11 causes electrical contact loss between the separator 5 and the outer frame 6.

FIG. 4 shows a modification of the present invention.

That is, in the present invention, a base material 12 of an alloy having higher high temperature strength than the Ni-Cu alloy of the present invention is sandwiched in the center as shown in FIG.
) or on one side as shown in Figure 4(b).
A cladding material laminated with Cu alloy 13 may be applied to the separator or current collector plate. This material has a surface Ni-C
The u alloy 13 increases molten salt resistance, and the substrate 13 further increases high temperature strength.

Since the Ni--Cu alloy applied to the battery of the present invention has weak oxidation resistance at high temperatures, it is desirable that the atmosphere during the brazing step in FIG. 4 be a vacuum or an inert gas atmosphere.

〔Example〕

Table 1 shows the chemical composition (wt%) of the test materials used in the examples. Nα1 is a comparison material of pure Ni, and Nα2 is a JIS standard H3261 material of the present invention.

Tables 1 and 3 show the results of the tensile test at 650°C. In the tensile Table 2 corrosion test, the gas atmosphere was set to H2, the same as the anode side of the battery.
: COz = 8 0 : 2 0 (water vapor 3 cc
/h addition), the test piece was immersed in a mixed carbonate in an alumina crucible, and the test was carried out at 650'C for 300 hours.

Table 2 shows the corrosion test results. The comparative pure Ni material and the material of the present invention exhibit excellent corrosion resistance with almost no corrosion even under the severe corrosion test conditions described above. In addition, SUS, which has been applied in the past, was conducted under the same corrosion test conditions as above.
The thinning thickness of 3 1 614 is 13.25 μm,
It is significantly inferior to the above two.

Table 3 Test temperature = 650″C The strength of the comparison material pure Ni is 10.5 kg/n
mn2-, whereas the invention material has 21. 0k
g/mm2, and it is clear that the material of the present invention is significantly higher.

As a demonstration test, a corrugated plate separator (0.3t) with the components shown in Table 1 and a current collector plate (0.3t) were installed on the anode side metal member.
), an electrode reinforcing material (0.13φ) was applied, a battery as shown in FIG. 3 (electrode surface M: 100 m square) was prepared, and a power generation test was conducted. As a result, battery performance is approximately 10% higher than before.
% improved. Further, after the power generation test, corrosion and deformation of the metal member applied to the anode side were investigated, but as with the experimental results described above, the corrosion and deformation were extremely slight.

As described above, it is clear that the material of the present invention has high molten salt resistance and high temperature strength, and is therefore suitable for the separator 5, current collector plate 4, and electrode reinforcing material 8 for molten carbonate fuel cells.

〔Effect of the invention〕

Since the material of the present invention has extremely excellent molten salt resistance, drawbacks such as consumption of carbonate and increase in electrical resistance due to oxide scale formation are suppressed, so it is useful for extending battery life and improving performance. effective.

[Brief explanation of the drawing]

Figure 1 is an assembled perspective view of a molten carbonate fuel cell, and Figure 2 is a sectional view of the anode and cathode electrodes. FIG. 3 is a sectional view showing the structure of a molten carbonate fuel cell, and FIG. 4 is a sectional view of the Ni--Cu alloy cladding material of the present invention. DESCRIPTION OF SYMBOLS 1... Electrolyte plate, 2... Anode electrode, 3... Cathode electrode, 4... Current collector plate, 5... Separator, 6
...Outer frame, 7...Gas supply pipe, S...Electrode reinforcing material, 9...Gas flow path, 10...Battery seal portion, 11.
...External pressure, 12...Base material, 13-Ni-Cu alloy. (voluntary) Amended statement

Claims (1)

[Claims] 1. An anode electrode and a cathode electrode containing an electrode reinforcing material are arranged above and below an electrolyte plate impregnated with molten carbonate, and current is collected above and below the anode and cathode electrode. In a molten carbonate fuel cell having a structure in which a plate is arranged and a separator is arranged above and below the current collector plate, an electrode reinforcing material having a wire mesh shape, a current collector plate having a punched porous shape, and a corrugated plate At least one type of separator having a shape is, by weight, Ni 63.0 to 70.0%, Mn 1.25% or less, Fe 2.5% or less, Si 0.5% or less, S0.024
% or less, C0.3% or less, and the balance Cu. 2. The molten carbonate/salt fuel cell according to claim 1, wherein the corrugated plate separator made of the alloy is joined to the battery outer frame by brazing. 3. The molten carbonate fuel cell according to claim 2, wherein the outer frame to be brazed to the corrugated plate separator is made of stainless steel, a Ni-based alloy, or an iron-based alloy. 4. In any one of claims 1 to 3, the separator and the current collector plate have a Ni-Cu alloy on the surface and a stainless steel, Ni-based alloy, iron-based alloy, or Co-based alloy on the inner surface. Molten carbonate fuel cell is a cladding material with a laminated structure.