JPH02242564A - Solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To prevent any damage of a cell due to a heat cycle and retain an excellent sealing property by composing a gas sealing part with a heat resisting porous sheet, in which a seal material is impregnatorily retained, interposed in a contact surface between a gas separation plate and a solid electrolyte. CONSTITUTION:A plate state cell 1 is composed of: a solid electrolyte 2 composed of an elaborate baked body of zirconia stabilized with 8% yttria, an anode electrode 3 composed of Ni-ZrO2 thermet, and a cathode electrode 4 composed of a perovskite type oxide such as LaCoO3, etc. A solid electrolyte fuel cell is formed with the cell 1 and a gas separation plate 5, in which each reaction gas supply path 3' and 4' is formed in a complexity direction each other on the back of each electrode 3 and 4, laminated each other, and a pas seal part is composed with a heat resisting porous sheet 6, in which a seal material becoming a high viscosity fusing body at a battery operation temperature is impregnated and retained, interposed in the contact surface between the plate 5 and the electrolyte 2. This enables any damage of a cell due to a heat cycle to be prevented, and an excellent seal property to be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a gas seal structure for a solid electrolyte fuel cell.

(B) Prior Art Solid oxide fuel cells (hereinafter referred to as 5OFC) are attracting attention as a completely solid-state third generation fuel cell following the phosphoric acid type and molten carbonate type.

This 5OFC utilizes the oxygen ion conductivity within the oxide solid (generally ZrO stabilized with Y 20 s), which eliminates all problems of electrolyte loss and allows for high operating temperatures of approximately 1000°C. Therefore, it has the characteristic of high power generation efficiency.

There are two types of 5OFC shapes: cylindrical and flat. The cylindrical shape is superior in terms of gas sealing, but it requires special techniques such as plasma spraying and EVD to create electrodes, and its structure makes it difficult to use. It has drawbacks such as difficulty in increasing the size of the cell and low output density per volume. On the other hand, the flat plate type has the advantage of being superior in mass production as the electrodes can be created by a coating method, and has the advantage of having a stacked structure in which many cells are stacked, increasing the output density per volume. The problem is that the seal is difficult.

The use of ceramic cement has been considered as a gas sealing method for flat-plate SOF Cs, but since ceramic cement is a solid seal and has a different coefficient of thermal expansion than each component of the battery, it can crack due to thermal cycles, resulting in poor sealing performance. There has been a problem in that gas leaks or cross leaks occur due to defects in the gas.

(c) Problems to be Solved by the Invention The present invention solves the above-mentioned problems by improving the seal structure of a flat plate type 5OFC.

(d) Means for Solving the Problems The present invention comprises a flat cell consisting of an anode, a solid electrolyte, and a cathode, and a gas separation plate in which reaction gas supply channels in intersecting directions are formed on the back surface of each of the electrodes. In a solid electrolyte fuel cell, the contact surface between the gas separation plate and the solid electrolyte is impregnated with a sealing material that becomes a highly viscous melt at the cell operating temperature. The gas seal part is constructed by interposing a quality sheet.

(E) Function In the present invention, the sealing melt is impregnated and retained in the heat-resistant porous sheet, so the melt does not wobble due to vibration or tilt of the stack, and the sealing material is similar to ceramic cement. Since it is not solid, it prevents cell damage due to thermal cycles and maintains good sealing performance.

(f) Example FIG. 1 is an exploded perspective view of the essential parts of the 5 OFC stack of the present invention, and FIG. 2 is an enlarged sectional view of the essential parts of the same.

The flat cell (1) consists of a solid electrolyte (2) consisting of a dense sintered body of zirconia stabilized with 8% ittria, and a N
an anode pole (3) made of i-ZrO2 cermet;
It is composed of a cathode electrode (41) made of a perovskite type oxide such as L a Co Os.

Solid electrolyte (2) has an outer dimension of 10 Qmm x 10 Qmm
, 'Thickness Q is 3 mm, and this solid electrolyte has a thickness of 5 m on each side facing each other in the direction in which the front and back intersect with each other.
A mask (thickness Q, 2 mm) is placed in advance, and an anode electrode (3) and a cathode electrode (4) are applied to each of the front and back surfaces of the electrolyte to a thickness of Q, 2 mm, and then the mask is removed.

Thus, the coating surface of each tfi(3)(4) is 90m+X
100Inm tape, 5mm x 100m on two opposing sides
It is baked leaving a non-coated surface of m.

The gas separation plate (5) interposed between these cells (1) is made of a heat-resistant metal such as a nickel-chromium alloy, and has an anode gas supply path (3) and a cathode gas supply path on each of its front and back surfaces in intersecting directions. It has a path (4).

When assembling the battery, the contact surface between the gas separation plate (5) and the solid electrolyte (2) and the uncoated surface of the electrodes (3) and (4) are impregnated with a sealing material that becomes a highly viscous melt at the battery operating temperature. heat-resistant porous sheet) (6) (6) is placed.

This porous sheet (G) (6) is a tape-shaped felt made of ceramic fiber made of a mixture of alumina and silica, and has dimensions of 5 mm x 1.00 mm and a thickness of h.
0.3 mm. On this sheet, powder of low expansion borosilicate glass (trade name: Pyrex glass) is applied for 30 minutes.
It is melt impregnated at 1200''C at a concentration of mg/cm2, and after cooling is assembled into a battery as described above.

Although not shown, an anode gas supply/discharge manifold and a cathode gas supply/discharge manifold are attached to opposing peripheral surfaces of the battery, respectively.

When the battery is started, it is heated to 1000 DEG C. under predetermined conditions, and as a result of this temperature increase, the impregnated glass in the porous sheet (6) turns into a highly viscous melt, forming a gas seal section. Then, hydrogen was used as the anode gas and air was used as the cathode gas, and discharge was performed at 300 mA/cm'.

Figure 3 is a characteristic diagram showing the results of a cycle test in which the battery was repeatedly operated (operating temperature: 1.000'C) and stopped (storage temperature: room temperature). However, the rate of characteristic deterioration due to heat cycling was about 10 mV/time for the battery of the present invention, while it was about 1.20 m\77 times for the conventional battery. .

As described above, the present invention significantly improves deterioration due to thermal cycles. This is thought to be because it maintains sealing performance, becomes solid when the battery is stopped, is reinforced by the porous sheet, and absorbs the difference in thermal expansion even when the battery is stopped, so no cracks occur.

In this example, a heat-resistant porous sheet was used, but a mixed fiber of alumina and silica was used, but porous zirconia felt may also be used, and as a sealing material, in addition to glass, KCl. , etc. or P1]0.Bi, 0. Oxides such as can also be used.

(l.) Effects of the Invention As described above, according to the present invention, the sealing material interposed at the contact surface between the solid electrolyte and the gas separation plate is a molten material impregnated and held in a heat-resistant porous sheet, which is different from the conventional ceramic material.・As it is not a solid like lxcement, it prevents cell damage due to heat cycles, and the melt does not shift even when subjected to vibrations or tilting, and maintains good sealing performance over a long period of time, preventing gas leaks. Cross leaks can be prevented.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of the main parts of the solid electrolyte fuel cell of the present invention.
FIG. 2 is an enlarged sectional view of the main part of the battery, and FIG. 3 is a characteristic diagram comparing and showing the rate of characteristic deterioration due to thermal cycles of the battery. ]゛Cell, 2: Solid electrolyte, 3: Anode electrode, -1' cathode electrode, 5: Gas separation plate, 6゛Heat-resistant porous sheet.

Claims (3)

[Claims] (1) A flat cell consisting of an anode, a solid electrolyte, and a cathode, and a gas separation plate in which gas supply channels in intersecting directions are formed on the back surface of each electrode are stacked alternately, and the gas A solid body characterized in that a gas sealing portion is formed by interposing a heat-resistant porous sheet impregnated with a sealing material that becomes a highly viscous molten material at battery operating temperatures on the contact surface between the separator plate and the solid electrolyte. Electrolyte fuel cell. (2) The solid electrolyte fuel cell according to claim 1, wherein the sealing material that becomes a high-viscosity melt is porsilicate glass. (3) The solid electrolyte fuel cell according to claim 1, wherein the heat-resistant porous sheet is a ceramic fiber felt containing at least one of zirconia, alumina, silica, and magnesia.