JPH05174844A - Solid electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To provide a solid electrolyte type fuel cell able to prevent the leakage of gas with a simple structure, by providing steps provided with an insertion groove for an unit cell consisting of 3-layer structure on both ends of one face of a separator respectively, and providing on the other face of the separator recessed portions or notches able to fit in members like the step. CONSTITUTION:An unit cell of a fuel cell consists of a 3-layered plate constructed with a platelike porous positive electrode 13, a dense solid electrolyte film produced on the electrode 13 and a negative electrode 12 of a specified metal corresponding to the electrode 13 coated on the film 11 except a peripheral area. On both faces of a separator 14 grooves 14a, 14b perpendicular to each other are provided as gas channels respectively, and on both ends of one face of the separator 14, respective flat steps provided with a horizontal groove 14c for insertion of the unit cell are provided vertically. And on the other face of the separator 14, recessed portions or notches able to fit in members corresponding to flat steps of another separator 14 or outer terminal plates 15, 16 are provided respectively. Thereby the generation of gaps between unit cells can be prevented to obtain a proper gas seal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell having a good gas sealing property. More specifically, the present invention relates to a support membrane type solid electrolyte fuel cell in which a unit cell is attached to an insertion portion provided in a separator and which can prevent gas leakage due to the structure.

[0002]

2. Description of the Related Art A fuel cell uses a combustible chemical substance such as hydrogen, carbon monoxide, or hydrocarbon, or a fuel containing the same as an active material, and causes an oxidation reaction of the chemical substance or fuel to be performed electrochemically. A battery that directly converts energy changes in the oxidation process into electric energy, and is expected to have high energy conversion efficiency.

Among them, particularly high efficiency can be expected, and in recent years, the third generation solid oxide fuel cell following the first generation phosphoric acid type and the second generation molten carbonate type, especially the flat plate having a high degree of integration The type is drawing attention.

A flat plate solid oxide fuel cell is usually housed in a manifold and has a gas passage formed therein.
One of the problems with such a battery is gas leakage. This measure against gas leak is particularly important in a stack in which a flat plate-like porous electrode is used as a support and a dense electrolyte membrane is formed thereon, and various gas sealing methods for preventing gas leak have been proposed. For example, a method of forming a dense film on the side surface of the porous electrode to prevent gas leakage from the side surface (Japanese Utility Model Laid-Open No. 2-62659, JP-A-2-255).
No. 2) or a method of supplying gas from the center and flowing out to the outer peripheral portion (JP-A-2-168568, JP-A-2-2).
6869, JP-A-2-28662) and the like.

However, it is difficult for the former to partially form a dense portion on the porous electrode support, and for the latter, it is difficult to control the temperature rise due to the combustion of fuel gas at the outer periphery. However, the structure is complicated and the cost is high.

[0006]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the gas sealing technology for a stack having such a conventional porous electrode support and a dense electrolyte membrane and is a technically difficult porous body. The object of the present invention is to provide a solid oxide fuel cell that does not require partial densification and can be gas-sealed with a simple structure.

[0007]

Means for Solving the Problems The present inventors have conducted various studies to develop a solid oxide fuel cell having the above-mentioned preferable characteristics, and as a result, a separator is provided with a porous electrode support and a dense electrolyte membrane. It is possible to achieve the object by providing a stepped portion having the insertion portion of the electrode-electrolyte membrane integrated laminated type flat plate having and a concave stepped portion or notched stepped portion for stacking the unit cells provided corresponding thereto. The present invention has been completed based on the findings.

That is, according to the present invention, a flat plate-like porous electrode is used as a support, and a dense solid electrolyte membrane is formed thereon,
Further, in a battery in which unit cells composed of a three-layer structure plate on which the other electrode is formed are laminated via a separator, a grooved step portion for inserting the above three-layer structure plate is erected on both ends of one surface of the separator. In addition, the present invention provides a solid oxide fuel cell characterized in that a concave stepped portion or a notched stepped portion into which the stepped portion can be fitted is provided on the other surface.

The unit cell used in the present invention has a flat plate-like porous electrode as a support, and a dense solid electrolyte membrane on almost the entire surface thereof by plasma spraying, thermal CVD, electron beam evaporation,
The three-layer structure plate is formed by a sputtering method or the like, and the other electrode is preferably formed thereon with one pair of side edge portions left. An anode and / or a cathode is used as this flat plate-shaped porous electrode.

The solid electrolyte membrane is not particularly limited as long as it has oxygen ion conductivity, and known solids such as stabilized zirconia such as yttria-stabilized zirconia (YSZ) and calcia-stabilized zirconia (CSZ). An electrolyte material or a polycrystalline sintered solid electrolyte material composed of stabilized zirconia and a metal oxide such as alumina is densely formed on the flat plate-like porous electrode, and the thickness thereof is usually 0.01 to 0.3 mm, preferably 0.
About 0.2 to 0.25 mm is suitable. This thickness is 0.
If it exceeds 3 mm, the resistance becomes too large, which is not preferable.

The cathode and the anode as the electrodes used in the present invention are not particularly limited as long as they are conductive materials having corrosion resistance to the oxidant gas and the fuel gas, respectively, at high temperature, but La _x Sr _1-x MnO ₃ is used. Cathode material, Ni-
It is preferable to use ZrO ₂ cermet as the anode material.
The electrode on the side other than the electrode as the substrate for forming an electrolyte membrane is usually deposited by using a plasma spraying method in addition to a method of applying a predetermined powder on the solid electrolyte plate by a brush coating method or a screen printing method. It The electrode formed by this coating is dried or burned out to remove the binder and / or the medium.

The separator used in the present invention is usually the above-mentioned 3
A plurality of grooves are provided on both surfaces of a dense conductive plate having no gas leakage, which is one less than the number of layered structure plates, preferably in mutually intersecting directions between the surfaces to form gas flow paths for fuel gas and oxidant gas, respectively. In addition, a grooved step portion for inserting the three-layer structure plate, preferably a flat step portion with a horizontal groove, is erected on both ends of one surface of the one surface, and an equivalent portion of the step portion is fitted on the other surface. A concave step portion or a notch step portion that can be mounted is provided. Further, the contact between the separators and the sealing surface must be electrically insulated, and an insulating film of alumina or the like may be formed thereon by a thermal spraying method or an insulating thin plate may be sandwiched therebetween.

In the external terminal plate, a plurality of grooves are provided on one surface of two dense conductive plates having no gas leak, and a gas flow path for an oxidant gas and a gas flow path for a fuel gas are formed on each surface. Preferably, it has a structure of one surface of the above-mentioned separator adapted to each corresponding electrode.

As described above, the separator electrically connects the electrodes of the adjacent single cells, and has grooves on both sides which serve as flow passages for the fuel gas and the oxidant gas, and each flow passage has its own cathode. The passages of each gas on the side of the anode and the side of the anode. A plurality of grooves serving as the respective gas passages are arranged in parallel, and preferably the groove on one surface and the groove on the other surface are arranged in a direction intersecting with each other, particularly in a right angle direction. With this arrangement, after the cells are integrated, the inlet and outlet of the fuel gas and the inlet and the outlet of the oxidant gas can be arranged on the same side end face, and the gas supply / exhaust system is configured as an integrated cell. Can be simple and easy.

As the conductive plate used for the separator and the terminal plate, a metal such as nickel or cobalt, nickel,
Alloys containing chromium, cobalt, etc., various sintered bodies such as lanthanum chromite composite oxides doped with alkaline earth metals and Co, Ni, Fe, Zn and other metals, silicon carbide, molybdenum silicide, chromium silicide, etc. Conductive ceramics, nickel metal, nickel-based alloy,
Cobalt metal or cobalt-based alloy and at least one inorganic compound selected from alumina, silica, titania, indium oxide, stannic oxide, silicon carbide and silicon nitride, or lanthanum chromite complex oxide or yttrium chromite. Examples thereof include a sintered body obtained by firing a conductive inorganic oxide such as a complex oxide with a non-oxidizing atmosphere, for example, in a reducing atmosphere or in a vacuum.

The nickel-based alloy is Ni-Cr.
System alloy, Ni-Cr-Fe system alloy, Ni-Cr-Mo system alloy, Ni-Cr-Mo-Co system alloy, Ni-Cr-M
o-Fe alloys and the like, and cobalt-based alloys,
Co-Cr type alloy, Co-Cr-Fe type alloy, Co-C
Examples thereof include r-W based alloys and Co-Cr-Ni-W based alloys.

In the present invention, a unit cell composed of these three-layer structure plates, a separator, and an external terminal plate are used, and
The layer structure plate is attached to the insertion part of the predetermined separator, and a predetermined number of layers are laminated to form a multi-stage series structure of a single cell,
By properly adjusting the number of stacked single cells and providing external terminal plates at both ends, a battery body composed of a series-type stacked multi-stage cell composed of a large number of single cells can be assembled. At that time, between the separators, between the three-layer structure plate and the separator, between the separator and the external terminal plate, or between the three-layer structure plate and the external terminal plate, for example, at the edge portion of the separator or the external terminal plate along the groove direction, etc. To prevent gas from leaking.

The encapsulant used when forming the battery body by laminating the three-layer structure plate, the separator and the external terminal plate as described above becomes a softened state at the operating temperature of the battery, or Those having a softening temperature equal to or higher than the operating temperature and solidifying at the operating temperature, and having corrosion resistance to the raw material gas such as fuel gas and oxidant gas and the generated gas at the operating temperature, for example, fuel gas When hydrogen or oxygen or air is used as the oxidant gas, it is not particularly limited as long as it has reduction resistance, oxidation resistance and water vapor resistance, but has a softening point of 500 ° C. or higher, preferably 600 ° C. to 12 ° C.
Glass at 00 ° C is preferred. Examples of such glass include soda lime glass, borate glass, borosilicate glass, and aluminosilicate glass. These glasses are used in the form of plates and felts, or they are dispersed in an organic substance such as an organic binder to form a paste, which is applied to the required sealing part, and after assembling a battery, the organic substance is burned out. Then, the glass may be restored.

The softening point is the operating temperature of the battery (900 to 110).
The glass having a temperature of 0 ° C. or less is preferably one having a viscosity of 10 ² to 10 ⁷ poise at the operating temperature of the battery. When the glass has a softening point of not less than the operating temperature of the battery (900 to 1100 ° C.), the temperature is once raised to the softening point or more and then lowered to the operating temperature to solidify the gas. In this case, the coefficient of thermal expansion of glass is 6 × 10 ⁻⁶
12 × 10 ⁻⁶ cm ⁻¹ is desirable. Further, it may be one that undergoes a phase transition from a glass phase to a more stable crystal phase with long-term use at high temperature.

The means for interposing the above-mentioned sealant is, for example, means for applying and laminating the above paste-like glass, that is, glass paste, on at least one surface of the solid electrolyte plate and the separator on which electrodes are formed, and the solid for which electrodes are formed. Means for sandwiching and laminating the glass between the electrolyte plate and the separator, applying the glass paste on at least one surface of the solid electrolyte plate and the separator on which the electrode is formed,
Means for laminating with the glass interposed therebetween may be used.

When the sealing agent for preventing gas leak is dispersed in an organic substance to be used as a paste, the paste is applied to a required sealing portion to assemble a battery, and then the organic substance is added. The sealing material for gas leak prevention is restored by removing it by drying, evaporation or burnout.

Next, in the present invention, the desired fuel cell is manufactured by accommodating the thus assembled cell body, that is, the laminated multi-stage cells in the manifold. In this manifold, four chambers partitioned by the inner surface of the manifold and the peripheral surface of the cell inscribed therein supply fuel gas and oxidant gas,
It has a structure that serves as a discharge space, serves as a member for forming a gas passage, and also serves as an outer wall.

[0023]

EXAMPLE A solid oxide fuel cell main body consisting of three-stage series cells was produced as follows according to the assembly mode of FIG.
A plate-like porous anode 1 made of Ni / ZrO ₂ (1/1 weight ratio) cermet and having a thickness of 1.0 mm in each cell 1
The stabilized zirconia added with 8 mol% of yttria was plasma-irradiated on the No. 3 as an electrolyte 11 having a thickness of 0.05 mm. La ₀ . ₉ Sr ₀ . ₁ MnO ₃ powder was dispersed in an organic binder and applied to a thickness of 0.2 mm to form a cathode. In this way the porous anode,
A three-layer structure plate composed of an electrolyte and a cathode was prepared.
The separator 14 is made of a Ni-based alloy and has grooves 14a and 14b as gas passages which are substantially orthogonal to each other on both sides, and has flat steps with horizontal grooves 14c for inserting the three-layer structure plate at both ends of the one surface. In addition to being erected upright, a concave step portion or a notch step portion into which a flat step portion or the like can be almost fitted is provided on multiple surfaces.

When the three-layer structure plate is inserted into the flat step portion of the separator and the separators are stacked, the flat step portion of one separator and the concave step portion or the notch step portion of the other separator are fitted to each other in a substantially conforming manner. No gap is generated between the unit cells.

External terminal boards 15 and 16 at both ends of the laminated cell
Has a structure on one surface of a separator that is suitable for each corresponding electrode. That is, the external terminal board 1 whose anode side faces
6 has a gas passage only on the facing side, that is, on the inner side, and has the flattened step portion on the facing side, and the other side, that is, the outer side is a flat surface, and the external terminal plate 15 facing the cathode side is The gas passage is provided only on the facing side, that is, the inner side, and the concave step portion or the notched step portion is provided on the facing side, and the other surface side, that is, the outer side is a flat surface.

The unit cell composed of this three-layer structure plate, the separator, and the external terminal were integrated so that each single cell had three layers.

FIG. 2 shows a gas sealing method for the integrated cell. The fuel gas flowing out from the side surface of the porous anode 13 is sealed between the flat step portion of the separator 14 and the dense electrolyte 11. Further, the oxidant gas is sealed between the lower surface of the upper separator 14 and the dense electrolyte 11. Gas leaks between the separators 14 are adhered and sealed with a zirconia-based inorganic adhesive at the overlapping portions of the four corners of the separator.
This portion is sprayed with an alumina film for electrical insulation. A glass paste having a softening point of about 800 ° C. was applied to these sealed portions for gas sealing. This glass paste softens sufficiently at the operating temperature of the battery to seal the gas.

The battery body thus integrated was placed in a cylindrical alumina manifold. The contact portion between the manifold and the battery body was coated with glass paste and gas-sealed.
A platinum lead wire was inserted into the external terminal for electrical connection.

The laminated cell manufactured in this manner is shown in FIG.
Insert into the cylindrical manifold 32 as shown in
The outlets of a and 14b were arranged so as to face the tube wall. If the contact points (4 points) between the battery body 31 and the manifold 32 are sealed with the same glass paste as above, the grooves 14a, 14
Both ends of b correspond to the four gas passages 33 to 36 formed by the wall of the manifold 32 and the battery body 31, respectively. In addition, a platinum lead wire was welded to the electrical outlet to electrically connect it.

The three-stage stacked solid oxide fuel cell thus produced was heated. 1 from room temperature to 150 ° C
The solvent of the glass paste was evaporated by heating at a temperature of ° C / min. The temperature was raised from 150 ° C to 350 ° C at 5 ° C / min. At 350 ° C. or higher, in order to prevent oxidation of the anode on the hydrogen passage side, nitrogen gas was flown and the temperature was raised to 1000 ° C. at 5 ° C./min. Then, the temperature was maintained at 1000 ° C., hydrogen was flown to the anode side and oxygen was flown to the cathode side to start power generation. Table 1 shows the discharge characteristics of a cell in which the area of the electrolyte portion is 25 cm ² .

[0031]

[Table 1] The open circuit voltage is 3.3V and the gas cross leak is 5.0 of hydrogen.
% Or less, indicating a good sealing property.

[0032]

According to the present invention, a solid oxide fuel cell can be manufactured easily and inexpensively by a simple manufacturing process. Further, the gas seal can be satisfactorily performed with a sealant similar to that of the self-supporting membrane type flat battery.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of an assembly mode of series cells.

FIG. 2 is an explanatory view showing a gas sealing method for an integrated cell.

FIG. 3 is an explanatory view of a fuel cell, which is a completed product, in which a cell body composed of three-stage series cells is housed in a manifold.

[Explanation of symbols]

 11 Electrolyte 12 Cathode 13 Anode 14 Separator 14a, 14b Groove 14c Horizontal groove 15, 16 External terminal plate 31 Battery body 32 Manifold 33-36 Gas passage

[Procedure amendment]

[Submission date] August 8, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Yoshida 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (2)

[Claims] 1. A unit cell composed of a three-layer structure plate having a flat plate-like porous electrode as a support, a dense solid electrolyte membrane formed thereon, and the other electrode formed thereon, with a separator interposed therebetween. In the laminated battery, a grooved step portion for inserting the above-mentioned three-layer structure plate is provided upright on both ends of one surface of the separator, and a concave step portion or notch into which the equivalent of the step portion can be almost fitted on the other surface. A solid oxide fuel cell having a step portion. 2. The solid oxide fuel cell according to claim 1, wherein the cell body is housed in a manifold.