JPS6091567A - Fuel cell - Google Patents

Abstract

PURPOSE:To increase the electrolyte-holding ability of an electrolyte plate by preventing any leakage of an electrolyte from the periphery of a porous ceramic electrolyte plate by surrounding it with a high density ceramic member. CONSTITUTION:An electrolyte plate has a complex structure consisting of a porous ceramic electrolyte plate 1 and a high-density ceramic frame 8 surrounding the electrolyte plate 1. The outer dimensions of the ceramic frame 8 are equal to those of a separator 4. Since the electrolyte plate 1 is exposed owing to the ceramic frame 8, an electrolyte does not leak outside the cell. In this fuel cell, the area touching the electrolyte plate 1 as usual is used as wet seal section 7 for gas sealing and the outer area touching the ceramic frame 8 is used for sealing the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improving the performance of electrolyte plates in molten carbonate fuel cells.

[Background of the invention]

Fuel 111& has the advantage of high power generation efficiency and fewer restrictions on scale and location.In particular, compared to phosphoric acid type, molten carbonate type has higher efficiency, does not require expensive catalysts, and can use CO as a fuel. It has the advantages of

A conventional cell structure will be explained with reference to the attached drawings.

FIG. 1 shows the structure of a part of a stacked cell, and FIG. 2 shows a cross section of a single cell.

The cell structure has a carbonate toxin 1 in the center, an anode 2 and a cathode 3 on the top and bottom sandwiching it, and a separator 4 sandwiching them.

Power generation is performed by the following mechanism. In other words, fuel gas (H2, CO, etc.) and air pass through the grooves of fuel flow passages 5 and 9 and air flow passages 6 carved on the upper and lower surfaces of the separator, respectively, and pass through the anode 2.
The fuel diffuses into the cathode 3 and comes into contact with the electrolyte, and an oxidation reaction of the fuel takes place on the anode 2 side, while a reduction reaction of oxygen takes place on the cathode 3 side. Since the electrolyte only allows ions to pass through, the carbonate ions pass through the electrolyte to the cathode 3.
The electrons move from the anode 2 to the cathode 3 through the external circuit and the separator 4, which also serves as a current collector plate, making it possible to take out the 11L flow to the outside. .

Further, the electrolyte plate 1 has the same outer dimensions as the separator 4, and is in contact with the anode 2 and the cathode 3, as well as the separator 4 at the outer periphery, and the contact portion between the electrolyte plate 1 and the separator 4 (Wet seal part) The laxative fluid seeps into 7 and forms a wet seal, causing gas leakage'11.
It has a structure that prevents

In such a structure, since the outer periphery of the porous ceramic plate 1, which is an electrolyte plate, is exposed, the permeated electrolyte escapes from the outer periphery, reducing the amount of electrolyte retained, and as a result, the internal This increases resistance, which leads to deterioration of cell characteristics and is one of the causes of shortening cell life. Further, since the electrolyte plate 1 is porous, it has low strength and has problems such as changes in porosity, changes in shape, and cracks due to tightening of the battery and heat cycles caused by repeated stoppages of battery operation.

[Purpose of the invention]

It is an object of the present invention to provide an electrolyte plate that prevents leakage of σ' dissolved solute from the outer periphery and retains electrolyte.

[Summary of the invention]

The cause of electrolyte leakage from the outer periphery of the electrolyte plate is that the porous electrolyte plate permeated with electrolyte is exposed to the outside. As a solution to this problem, the exposed outer periphery of the electrolyte plate may be made of material (X) that does not allow the electrolyte to pass through. To this end, the material for the outer circumference is a high-density ceramic that is stable at operating temperatures (600 to 700°C), has good thermal expansion properties, and has excellent corrosion resistance.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 shows an electrolyte plate according to an embodiment of the present invention, which has a composite structure including an electrolyte plate 1 made of porous ceramic inside and a high-density ceramic frame 8 on the outer periphery.

FIG. 4 shows an embodiment in which a porous ceramic electrolytic plate 1 and a high-density ceramic frame 8 are combined into a single cell.

The outer dimensions of this high-density ceramic frame 8 are equal to the outer dimensions of the separator 4, and by being sandwiched between the separator 4 combined with the porous ceramic electrolyte plate 1, the high-density ceramic frame 8 is isolated from the outside world. The contacting porous ceramic electrolyte plate 1 is no longer exposed, resulting in a structure in which the electrolyte does not leak to the outside.

Here, the width of the high-density ceramic material is Sepano 4 electrolytic J
This separator 4 is narrower than the width of the holding part.
In the part that holds down the electrolyte, the part that is in contact with the porous ceramic electrolyte plate is used as the conventional wet seal part 7 for gas sealing, and the outer part that is in contact with the high-density ceramic frame 8 is used for electrolyte sealing. It has a structure. In addition, the high-density ceramic frame 8 has the effect of reinforcing the porous ceramic electrolyte plate 1, which is weak in strength. Coating can be prevented by supporting the load and proper electrolyte plate thickness can be maintained throughout.

FIG. 5 shows another embodiment of the present invention, in which, in contrast to the above-described divided structure of the high-density ceramic frame 8 and the porous ceramic electrolyte plate 1, the density of the outer peripheral part of the porous electrolyte plate 1 is It has an integrated structure in which a density changing section 9 is provided that gradually becomes lower toward the end. Since the outer periphery of the density changing portion 9 has a sufficiently high density and almost no electrolyte permeates therein, leakage n6 of the electrolyte from the outer periphery can be prevented. In this case as well, by making the width of the density changing part 9 narrower than the width of the part of the separator that presses the electrolyte plate,
The wet seal part 7 is completely formed and has a structure that also provides a gas sealing effect.

The integrated structure simplifies cell assembly, and since the density of the ceramic gradually changes in the density changing section 9, stress concentration due to thermal deformation is reduced, increasing the strength and reliability of the electrolyte plate. It gets expensive.

〔Effect of the invention〕

As mentioned above, the outer circumference s' of the porous ceramic electrolyte plate
iBy using high-density ceramic, leakage of electrolyte from the outer periphery is prevented and the electrolyte retention capacity of the electrolyte plate is increased.Furthermore, the high-density ceramic part also serves as reinforcement for the porous electrolyte plate. It has the effect of extending cell life.

[Brief explanation of the drawing]

Fig. 1 is a structural diagram of a conventional laminated cell, Fig. 2 is a cross-sectional view of a conventional single cell, Fig. 3 is a structural diagram of an electrolyte plate of the present invention, and Fig. 4 is a cross-section of an example of an electrolyte plate with a split structure. 1g1 FIG. 5 is a cross-sectional view of an embodiment of an electrolyte plate having an integral structure. 1... Electrolyte plate (porous part), 2... Anode, 3
...Cathode, 4...Separator, 5...Fuel flow path, 6...All air flow path, 7...Wet seal portion, 8
... High-density ceramic frame, 9... Electrolyte plate (density changing part). Agent Patent Attorney Akio Takahashi 2nd Sen

Claims (1)

[Claims] 1. In a molten carbonate fuel cell, an electrolyte plate V made of porous ceramic that serves to hold an electrolyte is made with a high density on its outer periphery, and the density is different between the inside and outside. A fuel cell characterized by having an electrolyte plate made of ceramic. 2. A fuel cell according to claim 1, characterized in that the electrolyte plate has an electrolyte plate in which the ceramic density at the outer circumferential portion of the electrolyte plate is gradually increased from the porous interior toward the outer circumferential portion. 3. A fuel cell according to claim 1, characterized by having an electrolyte plate having a structure in which a high-density outer peripheral portion and a porous interior of the electrolyte plate are separated. 4. In claim 2, item 3, the starting point of the densification of the outer periphery of the electrolyte plate and the boundary point between the high-density outer periphery and the porous interior are located outside of the inner edge of contact with the separator. A fuel pond characterized by: