JPH05174846A - Solid electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To prevent the leakage of gas with a simple structure by arranging the dense film side of an unit cell electrode on a holed face of a separator and sealing the four peripheral sides so as to supply gas from the separator through the holes. 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 11 produced on the electrode 13 and a negative electrode 12 of a specified metal coated on the film 11. On one face of a separator 14, grooves 14a are provided as fuel gas channels, and on the other face of the separator 14 a large number of holes 14c are provided for supplying gas. In addition, channels 14b connected through to the holes 14c in the inner portion of the separator are provided so as to open on the both sides of the separator where no grooves 14a are provided. These separators 14 are laminated so as that the holed face of a separator 14 is positioned in the electrode side of another separator.

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 provides a support membrane type solid electrolyte capable of preventing a gas leak due to the structure, which is provided with a hole for gas supply on one surface of a separator and communicates with an internal passage opening to a side end. It relates to a fuel cell.

[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 cell 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, Japanese Patent Laid-Open No. 2-2).
552) or a method of supplying gas from the center and flowing out to the outer peripheral portion (JP-A-2-168568 and JP-A-2).
No. 26869, 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 combustion of the fuel gas in the outer peripheral portion. It is unavoidable that the structure is complicated and costly.

[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]

The inventors of the present invention have conducted various studies to develop a solid oxide fuel cell having the above-mentioned preferable characteristics, and as a result, the dense membrane side of the electrode has a separator hole. Placed on the surface, by sealing the four sides in the usual way and supplying gas through the holes from the separator,
The inventors have found that the object can be achieved and completed the present invention.

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, the other electrode composed of a dense film was formed thereon 3
In a battery in which unit cells composed of a layered structure plate are laminated via a separator, a plurality of grooves are provided on one surface of the separator to form a predetermined gas flow path, and a hole for gas supply is provided on the other surface, and the hole is provided. A solid oxide fuel cell characterized in that a passage communicating with the inside of the separator is provided so as to open to a corresponding pair of side end portions, and the other surface of the separator is arranged so as to be on the side of the other electrode. Is provided.

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
It is one in which a plurality of grooves are provided on one side of a dense conductive plate with no gas leak, which is one less than the number of layer structure plates, and a predetermined gas flow path, usually a fuel gas flow path, is formed on the other surface. A gas supply hole is provided, and a passage communicating with the hole is provided so as to open from the inside of the separator to a corresponding pair of side end portions, preferably to the pair of side end portions where the groove is not formed. is there. The separator is arranged so that the other surface is on the side of the other electrode made of a dense film.

Further, the external terminal plates at both ends of the laminated cell are two dense conductive plates having no gas leak, each having a gas flow path for fuel gas and a gas flow path for oxidant gas formed therein. It has a structure on one side of a separator that is compatible with the corresponding electrode. That is, the external terminal facing the anode side has a groove as a gas passage only on the facing side, that is, the inside, and the other side, that is, the outside is a flat surface, and the external terminal facing the cathode side is the facing side. That is, it has a hole for gas supply only on the inner side, and a passage communicating with the hole is formed from the inside of the external terminal to a pair of corresponding side end portions, preferably the same as the pair of side end portions where the groove is not formed in the separator. It is provided so as to open to the side, and the other side, that is, the outside is a flat surface.

As described above, the separator electrically connects the electrodes of the adjacent single cells, has a groove for one gas flow passage on one surface, and has a gas supply hole for the other gas on the other surface. A passage internally communicating with this hole opens at a side end portion to form the other gas flow passage, and each flow passage constitutes a passage for each gas on each electrode side of the cell. A plurality of gas passages are arranged, and preferably, they are arranged in a direction intersecting with each other, particularly in a direction perpendicular to each other. 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. The holes have various shapes such as a grid point or a grid shape, a zigzag grid point shape, and a vertical, horizontal, or oblique long hole shape. The passage communicating with this hole has various shapes such as a wide slit and a large number of parallel through holes.

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 board are used, and a predetermined number of these are stacked to form a single-cell multi-stage series structure.
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. In that case, a separator is interposed between the separators, the three-layer structure plate and the separator, the separator and the external terminal plate, or the three-layer structure plate and the external terminal plate so as 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
A stabilized zirconia containing 8 mol% of yttria was plasma-irradiated on the surface of No. 3 to form a dense electrolyte 11 having a thickness of 0.05 mm. La ₀ . ₉ Sr ₀ .
₁ MnO ₃ powder is dispersed in an organic binder to a thickness of 0.
2 mm was applied to make a cathode. In this way, a three-layer structure plate composed of the porous anode, the electrolyte and the cathode was produced.

The separator 14 is made of a Ni-based alloy and has a plurality of grooves 14a formed on one surface thereof to form a fuel gas flow path, and a gas supply hole 14c formed on the other surface thereof, and a passage 14b communicating with the holes. Is provided so as to open from the inside of the separator to the pair of side end portions where the groove is not opened. The other surface is laminated so that it is on the side of the other electrode made of a dense film.

Further, the external terminal boards 15 at both ends of the laminated cell,
Reference numeral 16 is made of a Ni-based alloy and has a structure of one surface of a separator suitable for each corresponding electrode. That is, the external terminal 15 facing the anode side has a groove as a gas passage only on the facing side, that is, the inner side, and the other surface side, that is, the outer side is a flat surface, and the external terminal 16 facing the cathode side is the same. While having a hole for gas supply only on the facing side, that is, on the inner side, the passage communicating with the hole is opened from the inside of the external terminal to the same side as the pair of side end portions where the groove of the separator is not opened. It is provided 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.
The single cell is laminated such that the porous anode 13 is on the groove 14a side and the cathode 12 is on the hole 14c side.

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 upper surface of the hole 14c of the separator 14 and the dense electrolyte 11 and the contact portions 14d of the upper and lower separators. Further, the oxidant gas is sealed between the upper surface of the hole 14c of the separator 14 and the dense electrolyte 11. An alumina film is sprayed on the contact portions 14d of the upper and lower separators 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 laminated cell manufactured in this manner is shown in FIG.
Insert into the cylindrical manifold 32 as shown in
a, the outlet of the passage 14b is arranged so as to face the tube wall.
Contact points between battery body 31 and manifold 32 (4 locations)
If gas is sealed with the same glass paste as above, the groove 14
Both ends of a and the passage 14b correspond to the wall of the manifold 32 and the four gas passages 33 to 36 formed by the battery main body 31, respectively. Further, a platinum lead wire was welded to the external terminal of the electricity take-out portion and electrically connected.

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 .

[0030]

[Table 1] The open circuit voltage is 3.4V and the gas cross leak is 5.0 of hydrogen.
% Or less, indicating a good sealing property.

[0031]

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 Codes] 11 Electrolyte 12 Cathode 13 Anode 14 Separator 14a Groove 14b Passage 14c Hole 15, 16 External Terminal Plate 17 Sealant 31 Battery Main Body 32 Manifold 33-36 Gas Passage

Continued 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 in which a flat plate-like porous electrode is used as a support, a dense solid electrolyte membrane is formed thereon, and the other electrode made of the dense membrane is further formed thereon. In a battery laminated via a separator, a plurality of grooves are provided on one surface of the separator to form a predetermined gas flow path, and a gas supply hole is provided on the other surface, and a passage communicating with the hole is formed inside the separator. To the corresponding pair of side ends, and the other surface of the separator is arranged so as to be on the side of the other electrode. 2. The solid oxide fuel cell according to claim 1, wherein the cell body is housed in a manifold.