JPH03238758A - Fuel cell of solid electrolyte type - Google Patents

Abstract

PURPOSE:To simplify the construction of a fuel cell and reduce the internal resistance thereof by forming the films of a fuel electrode, a solid electrolyte and an air electrode in sequence on one side of a dense substrate comprising the same material as a fuel electrode part and having many through-holes. CONSTITUTION:In a solid electrolyte type fuel cell comprising a solid electrolyte 1, an air electrode 2 and a fuel electrode 3, one side of a dense substrate comprising the same material as the fuel electrode 3 and having many through-holes is applied with the films of the fuel electrode 3, the solid electrolyte 1 and the air electrode 2 respectively in that order. As the substrate is manufactured according to the aforesaid process, the high strength and small thickness thereof can be ensured. Also, even for a large fuel cell, compact construction can be applied. In addition, the internal resistance of the fuel cell can be lowered and the conductivity thereof can be increased, thereby improving cell performance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a solid oxide fuel cell, particularly its structure.

[Prior Art] Recently, fuel cells have been attracting attention and being developed as a device that directly converts the free energy change of a chemical reaction into electrical energy. A fuel cell is different from a normal chemical cell, but the difference is that the active material of the electrode is not contained within the battery container, and the negative electrode oxidizes the fuel, and the positive electrode oxidizes the fuel. It generates electricity by continuously supplying materials, and commercialization is being actively considered as one of the leading direct power generation systems. Among these fuel cells, solid electrolyte fuel cells using stabilized zirconia as an electrolyte are attracting attention as third generation fuel cells.

That is, zirconia (Z r O2) undergoes a crystal structure transition from monoclinic to tetragonal at around 1150° C., and at this time, a volume change of about 9% occurs. In order to prevent this volume change, oxides such as calcium and yttrium are dissolved in zirconia as a solid solution, and such a solid solution is called stabilized zirconia.

FIG. 6 is an explanatory diagram of the principle of such a fuel cell.

As shown in FIG. 6, an air electrode 2 is provided as a positive electrode on one surface of a solid electrolyte 1 such as stabilized zirconia, and a fuel electrode 3 is provided as a negative electrode on the other surface.

Air (02) flows through the air electrode 2, and fuel gas (02) flows through the fuel electrode 3.
When H, CO) is flowed, the reaction 02+4e→20 occurs on the air electrode 2 side, and the reaction 20 -02+46 occurs on the fuel electrode 3 side.

The electrons (e) generated by the above reaction move from the fuel electrode 3 side toward the air electrode 2, and the air electrode 2, which is the positive electrode,
Electricity flows between it and the fuel electrode 3, which is a negative electrode.

H2+l/202→H20 During this reaction, water generated at the same time is discharged from the system.

Solid electrolyte fuel cells are constructed as described above, but in order to realize the cell structure, conventional solid electrolyte 1
was used as a base, or another substance other than the solid electrolyte 1 and the electrode was used as a base.

FIG. 7 is a sectional view showing an example of a case where a solid electrolyte is used as a base.

As shown in FIG. 7, on one surface of a solid electrolyte 1 made of stabilized zirconia having a sufficient thickness as a base, there is a thin fuel electrode 3 made of a porous material sprayed with nickel oxide powder at high temperature. On the other surface of the solid electrolyte 1, a thin air electrode 2 made of a porous ceramic material such as L a M n03 is provided.

FIG. 8 is a sectional view showing an example of a case where the substrate is made of a substance other than the solid electrolyte 1 and the electrodes.

As shown in FIG. 8, a base 4 of sufficient thickness made of a porous material such as ceramics, e.g. alumina, zirconia, etc.
A fuel electrode 3 made of a thin Ni porous material, a solid electrolyte 1 made of stabilized zirconia, and an air electrode 2 made of a ceramic porous material are laminated on one surface of the electrode.

As mentioned above, the fuel cell includes a solid electrolyte 1, an air electrode 2.
One cell composed of a fuel electrode 3 and a base 4,
It is formed by stacking multiple layers.

FIG. 9 is a schematic cross-sectional view showing an example of such a fuel cell composed of multiple stages of cells.

As shown in FIG. 9, a plate-shaped air electrode 2 made of a ceramic porous sintered body is provided on one surface of the solid electrolyte 1, and a Ni porous sintered body is provided on the other surface of the solid electrolyte 1. A plate-shaped fuel electrode 3 is provided.

A current collector 5 made of a corrugated heat-resistant metal plate is provided on the outside of each of the air electrode 2 and the fuel electrode 3, and a current collector 5 made of a flat heat-resistant metal plate is provided on the outside of the current collector 5. An interconnector (separator) 6 is provided.

The electricity generated as described above by supplying air or oxygen to the air electrode 2 and hydrogen or fuel gas to the fuel electrode 3 is collected by a corrugated current collector 5 and connected to an interconnector (separator) 6. Collects electricity from each cell.

The advantage of these oxide sintered solid electrolyte fuel cells using stabilized zirconia is that they can have an all-solid structure and the reaction at the electrodes is simpler than in molten carbonate batteries. .

[Problems to be Solved by the Invention] When a substrate is made of a material other than the solid electrolyte 1 as shown in FIG. This makes the structure complicated, and since current flows in parallel within the electrodes, problems such as an increase in internal resistance of the battery arise.

In the conventional solid oxide fuel cell as described above, when a porous substrate is used as a strength member for subsequent film formation and also functions as a fuel electrode, the following problems arise. .

1) In order to efficiently carry out electrochemical reactions as a fuel electrode, the structure of the fuel electrode at the interface between the solid electrolyte and the fuel electrode should be porous, consisting of as fine particles as possible, so that the solid electrolyte, electrode and It is necessary to increase the three-phase interface of gas.

When a fuel electrode with such a fine structure is made to a predetermined thickness (approximately 2 inches) to serve as a strength member for subsequent film formation, the gas permeability within the substrate deteriorates due to the fine bore. As a result, a good battery cannot be obtained.

2) Contrary to the above, if the substrate is made porous with large pores due to large particles in order to improve gas permeability within the substrate, the number of three-phase interfaces decreases, making it impossible to obtain a good battery.

3) Of course, it is possible to combine 1) and 2) above and use the electrode material near the surface of a porous material with large bores as having a fine structure. Since the strength is lower than that of a dense material, it is necessary to make it thicker, which results in poor gas permeability. Furthermore, since porous materials have lower electrical conductivity than dense materials, they also cause deterioration in battery performance.

An object of the present invention is to provide a battery that solves the above-mentioned problems with solid oxide fuel cells and has a simple structure and low internal resistance.

[Means for Solving the Problems] The solid oxide fuel cell of the present invention includes a solid oxide fuel cell comprising a solid electrolyte, an air electrode, and a fuel electrode, which is made of the same material as the fuel electrode portion of the cell. A solid oxide fuel cell is characterized in that the fuel electrode, solid electrolyte, and air electrode are formed in this order on one side of a dense substrate having a large number of through holes.

The above fuel electrode material is a solid electrolyte fuel cell made of nickel-zirconia cermet, and as another embodiment, the substrate is provided with a tooth-shaped through hole. , a solid oxide fuel cell comprising a groove added to one of the through-holes of the substrate, and further characterized in that a grooved separator is used as a current collector of the cell configured as described above. It's a battery.

[Function] According to the solid oxide fuel cell of the present invention, 1> fuel gas permeability is improved because a substrate having a large number of through holes is used.

2) By providing a groove in the through hole, gas permeability to the electrode portion is further improved.

3) Since the substrate is made of a dense material, it can be made of a strong and thin material, resulting in a compact structure even when increasing in size.

4) Furthermore, since the substrate is made of a dense material, the conductivity of this part is high, improving battery performance.

5) Since the fuel electrode at the solid electrolyte interface, which is directly involved in the electrochemical reaction, has a fine structure, battery performance is improved.

Next, embodiments of the present invention will be described.

[Example Figures 1 (a) to (e) are explanatory diagrams showing the fabrication of a solid oxide fuel cell which is an example of the battery of the present invention, and Figures 2 and 3 are another example. An explanatory diagram showing a certain base (plate),
FIGS. 4(a) and 4(b) are explanatory diagrams showing the planes of the grooves, and FIG. 5 is an explanatory diagram showing the configurations of cells and current collectors.

In the figure, 1 is a solid electrolyte, 2 is an air electrode, 3 is a fuel electrode, 4 is a substrate (plate), 4a is a green sheet, 5 is a current collector, 6 is an interconnector (separator), 7 is a through hole, 8 9 is a groove, 9 is a grooved separator, and 10 is a cell.

■) As shown in Figure 1 (a), thickness 1~2III1
A green sheet 4a of nickel-zirconia cermet No. 1 is molded.

2) As shown in FIG. 1(b), a through hole 7 with a diameter of 0.5 am is made in the green sheet 4a.

3) Next, as shown in FIG. 1(C), the green sheet 4a is fired at 1200 DEG C. to obtain the substrate 4.

4) As shown in FIG. 1(d), a thickness of 30~
40. A fine fuel electrode 3 made of nickel zirconia cermet is thermally sprayed and manufactured.

5) Next, solid electrolyte 1 is deposited by PVD method, and a composite oxide of lanthanum and manganese (LaMnO
3) A ceramic porous sintered body such as the one described above is thermally sprayed to provide an air electrode 2.

In the battery configured as above, if necessary, as shown in FIG.
A current collector 5 made of a corrugated heat-resistant metal plate such as a nickel alloy (Inconel 600) containing 16% Cr and 7% Fe is provided, and on the outside of the current collector, a conductive wire is provided to connect the single cells in series. For example, magnesium-doped lanthanum chromium oxide (L
A flat separator (interconnector) 6 made of ceramic (aCrMo2SgO,L03) is provided to complete the solid oxide fuel cell.

In such a solid oxide fuel cell, electricity generated by supplying air or oxygen to the air electrode 2 and hydrogen or fuel gas to the fuel electrode 33 is collected by a corrugated current collector 5, and is collected by a separator. 6 collects electricity from each cell 10.

In the step 1) of this battery, a tapered through hole 7 is provided in the green sheet 4a as shown in FIG. 7, gas permeability can be increased.

In addition, on the upper part of the through hole 7, as shown in FIG.
), as shown in (b), the cell reaction can be further promoted by adding grooves 8.

As another embodiment, as shown in FIG. 5, it is preferable to use a grooved separator 9 because the structure is simple.

Note that the electrode of the present invention is applicable not only to a flat plate type solid electrolyte fuel cell as shown in FIG. 1, but also to a multi-tube type solid electrolyte fuel cell.

[Effects of the Invention] According to the solid electrolyte fuel cell of the present invention, ■) By forming the cell structure H3 layer on a substrate having strength,
It becomes possible to manufacture large-area batteries.

2) Since a large number of through holes are provided in the substrate, fuel gas permeability is improved and battery performance is improved.

3) Since the substrate is relatively dense, it has higher conductivity than a porous substrate, improving battery performance.

4) Since a relatively dense substrate is used, the strength is increased and the battery can be made thinner and more compact than when a porous substrate is used.

5) Since the material for the fuel electrode and the material for the substrate are the same, they are compatible with each other, and there is no damage due to differences in thermal expansion coefficients, resulting in a battery with stable performance.

It has the following effects.

[Brief explanation of drawings]

FIGS. 1(a) to (e) are explanatory diagrams showing the fabrication of a solid oxide fuel cell which is an embodiment of the battery of the present invention, and FIGS. 2 and 3 are explanatory diagrams of another embodiment of the battery substrate. , Figure 4(a)
, (b) is an explanatory diagram showing the plane of the groove, Fig. 5 is an explanatory diagram showing the structure of the cell and current collector, Fig. 6 is an explanatory diagram of the principle of the fuel cell, and Figs. 7 and 8 are conventional diagrams. FIG. 9 is a schematic cross-sectional view showing an example of a conventional fuel cell consisting of multiple stages of cells. In the figure, 1: solid electrolyte, 2: air electrode, 3: fuel electrode, 4: substrate (plate), 4a nitrogen sheet, 5: current collector, 6: interconnector (separator), 7: through hole, 8 : groove, 9: grooved separator, 10: cell.

Claims (5)

[Claims] (1) In a solid electrolyte fuel cell consisting of a solid electrolyte, an air electrode, and a fuel electrode, on one side of a dense substrate made of the same material as the fuel electrode part of the cell and having many through holes. A solid electrolyte fuel cell characterized in that the fuel electrode, the solid electrolyte, and the air electrode are formed in this order. (2) The fuel electrode material is nickel, zirconia,
The solid oxide fuel cell according to claim 1, characterized in that it is made of cermet. (3) The solid oxide fuel cell according to claim 1 or 2, wherein the substrate is provided with a tapered through hole. (4) The solid oxide fuel cell according to any one of claims 1 to 3, wherein a groove is added to one of the through holes of the substrate. (5) The solid oxide fuel cell according to any one of claims 1 to 4, wherein a grooved separator is used as a current collector of the cell.