JPH08287926A - Method for manufacturing solid oxide fuel cell - Google Patents

Abstract

(57) [Summary] [Object] The present invention reduces the contraction rate of the fuel electrode to suppress the generation of stress due to the difference in contraction behavior between the fuel electrode and the electrolyte, thereby preventing the separation of the electrolyte from the fuel electrode. Preventable,
Therefore, it is an object of the present invention to provide a method for producing a solid oxide fuel cell, in which the productivity of the solid oxide fuel cell is improved and the reliability and durability thereof are also improved. According to the present invention, in a method for producing a solid oxide fuel cell having a fuel electrode as a support, the fuel electrodes 4, 4 ', 9 are produced by sintering, and then reduction treatment is performed, and then the fuel electrode is produced. A fuel cell is manufactured by forming electrolytes 3, 3 ', 3 "and oxidizer electrodes 2, 2', 2" on 4, 4 ', 9'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid oxide fuel cell using a fuel electrode as a support.

[0002]

2. Description of the Related Art A solid oxide fuel cell uses a solid substance for all constituent materials of a fuel cell that generates electric power by supplying two kinds of gases, an oxidant and a fuel, to an oxidant electrode and a fuel electrode. It is a thing. Specifically, the following ceramics are listed as main materials.

Electrolyte: Yttria-stabilized zirconia (hereinafter, YSZ) Fuel electrode: Nickel zirconia cermet (hereinafter, Ni
-YSZ) Oxidizer electrode: lanthanum manganite (hereinafter, LSM) Of these materials, the electrolyte has a very low electric conductivity, and therefore it is desirable to make the thickness as thin as possible. However, a fuel cell using an extremely thin electrolyte has a weak mechanical strength, and it is difficult to increase the area of the cell. Therefore, by using a high-strength porous support made of calcia-stabilized zirconia or the like and configuring a fuel cell on it, even if the thickness of the low-conductivity electrolyte is reduced, it is necessary for stacking. It has become possible to manufacture a fuel cell having strength. FIG. 4 shows a perspective view of an example of a conventional solid oxide fuel cell using a porous support. In the figure, 1 is a porous support, 2 is an oxidant electrode, 3 is an electrolyte, 4 is a fuel electrode, 5 is an interconnector, and 6 is an oxidant gas flow path. The fuel gas flows outside the fuel electrode 4.

However, the support material such as calcia-stabilized zirconia is a substance that does not participate in the reaction of the battery, and the inclusion of such a support inside the battery lowers the power generation efficiency of the battery and is not preferred.

Therefore, in recent years, a fuel in which the thickness of the fuel electrode and the oxygen electrode is made thick to use these electrodes as a support, an electrolyte thin film is formed thereon, and the other electrode is further formed on the electrolyte thin film Batteries are now being manufactured.
FIG. 5 shows a perspective view of an example of a solid oxide fuel cell using such an electrode as a support. In the figure, 2'is an oxidizer electrode, 3'is an electrolyte, 4'is a hollow flat support fuel electrode,
5'is an interconnector, 7 is a fuel gas channel, and 8 is a dense film. The oxidant gas flows outside the fuel cell.

[0006]

Ni-YSZ, which is generally used as a fuel electrode material in a solid oxide fuel cell using such a fuel electrode as a support, is manufactured by a doctor blade method or an extrusion molding method. It is produced by molding a mixture of YSZ powder and nickel oxide powder, and sintering the molded body. The sintering is usually performed in the atmosphere, and nickel in the sintered support fuel electrode exists as nickel oxide. Then, after forming an electrolyte, an oxidant electrode and the like on the support fuel electrode, they are stacked to form a fuel cell stack, and reduction is performed by flowing a fuel gas. Since the volume of the fuel electrode decreases during this reduction, when an electrolyte is formed on the oxidized support substrate fuel electrode, there is a stress between them due to the difference in contraction behavior between the fuel electrode and the electrolyte during the reduction of the fuel electrode. Works. This stress causes peeling or damage of the electrolyte membrane, which lowers the productivity of the fuel cell and also reduces the reliability and durability.

The present invention has been made in view of the above circumstances. By reducing the contraction rate of the fuel electrode, the generation of stress due to the difference in contraction behavior between the fuel electrode and the electrolyte is suppressed, and the electrolyte from the fuel electrode is reduced. It is an object of the present invention to provide a method for manufacturing a solid oxide fuel cell, which can prevent peeling of the solid oxide fuel cell and the like, thereby improving the productivity of the solid oxide fuel cell and also improving its reliability and durability.

[0008]

In order to achieve the above object, the first aspect of the present invention is to provide a method for producing a solid oxide fuel cell having a fuel electrode as a support, after the fuel electrode is produced by sintering. Then, a reduction treatment is performed, and then an electrolyte and an oxidizer electrode are formed on the fuel electrode to produce a fuel cell.

A second aspect of the present invention is characterized in that, in the method for producing a solid oxide fuel cell according to the first aspect, nickel zirconia cermet is used as a material for the fuel electrode.

[0010]

The function of the solid oxide fuel cell manufacturing method of the present invention is as follows. Ni-YSZ, which is the material for the support fuel electrode, is sintered and then reduced once to form an electrolyte thin film, and then an oxidizer electrode is formed on the electrolyte thin film. In the process of the present invention, the support anode is re-oxidized when the electrolyte is produced, and thereafter, even if the fuel gas is introduced into the fuel cell to carry out the reduction of the support anode, the volume contraction at that time does not occur. , Which is much smaller than the case where the electrolyte thin film is formed without performing the reduction treatment of the support fuel electrode. Therefore, the stress applied to the electrolyte at the time of reduction due to the introduction of the fuel gas is reduced, the fuel cell is less likely to be damaged, and its reliability and durability are improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings with reference to the drawings. The present invention is not limited to the following examples. [Embodiment 1] FIG. 1 is a flowchart showing a manufacturing process of a solid oxide fuel cell according to an embodiment of the present invention. Tosoh TZ-8Y is used for YSZ powder which is a raw material for the support fuel electrode.
(Particle size: about 0.3 μm), while nickel oxide powder contains nickel oxide for ceramics manufactured by Furuuchi Chemical (particle size: about 1 μm).
μm or less) was used. Nickel oxide is 60% by weight
So that YSZ and nickel oxide are weighed, put them in a ball mill, add ethanol, and then mix for 24 hours to obtain nickel oxide-Y
An SZ mixed powder was prepared. Next, to the mixed powder 100, after adding about 10 methylcellulose water-soluble polymer as a binder and 15 water (mixing ratio on a weight basis),
A clay-like material was obtained by kneading with a raw material kneader.
The clay-like material produced in this way was made into a hollow flat plate-shaped extrusion molded product having a flow passage for flowing a fuel gas therein by a vacuum extrusion molding machine. After drying, 400 ℃
Degreasing is performed by heating for 4 hours at
Sintering was performed by heating in the air at 00 ° C. for 2 hours. The thus-sintered Ni-YSZ support fuel electrode was placed in a reducing atmosphere furnace, and 100% was applied in a stream of 90% nitrogen and 10% hydrogen.
Heat treatment was performed at 0 ° C. for 2 hours to reduce the support fuel electrode. Next, an electrolyte thin film was formed on one surface and an interconnector thin film was formed on the other surface of the thus prepared support fuel electrode in the reduced state. In this case, each film was formed by a thermal spraying machine using the atmospheric spraying method. The material used is YSZ with 8 mol% yttria added to the electrolyte.
(Particle size: 10 to 50 μm), and lanthanum chromite (particle size: 10 to 50 μm) was used as the interconnector material. The thickness of each layer was 100 μm. Further, an oxidizer electrode was formed on the surface of the electrolyte thus produced, to obtain a solid oxide fuel cell. The formation of the electrodes at this time was performed by slurry coating and sintering. The raw material is La _0.8 Sr _0.2 having a perovskite structure.
A powder of MnO _{3 having} a particle size of 1 to ₃ μm was used. The slurry was obtained by adding 20% by weight of polyethylene glycol and ethanol to the raw material powder. The applied slurry is degreased by heating at 400 ° C. for 4 hours, and then 1
The fuel cell was formed by sintering at 300 ° C. for 2 hours. The thickness of the sintered oxidant electrode was about 50 μm. The fuel cell manufactured in this example has the same shape as the cell shown in FIG. The length of this cell is 10
It was 0.4 mm.

The above fuel cell was mounted on an alumina cell holder, heated to 1000 ° C. in an electric furnace, and hydrogen as a fuel gas and air as an oxidant gas of 100 ml / min were flowed into the fuel cell. The support fuel electrode was reduced. The cell length after reduction was 100.0 mm. Therefore, the contraction rate of the fuel cell due to the reduction was 0.4%.

[Comparative Example 1] As a comparative example, a fuel cell was prepared by the following method without performing reduction treatment before forming an electrolyte membrane.

Using the same raw materials as in Example 1, the processes from mixing of raw materials to sintering were carried out in the same manner as in Example 1. Without reducing the prepared fuel electrode sintered body, the electrolyte film and the interconnector film were sprayed in the oxidized state in the same manner as in Example 1, and further an oxidizer electrode was formed to prepare a fuel cell unit. did. The length of this fuel cell is 100.7 mm
Met. Then, in the same manner as in Example 1, the support fuel electrode was reduced in the cell holder. The length of the fuel cell after reduction was 99.6 mm. Therefore, the contraction rate of the support fuel electrode due to the reduction treatment was 1.1%. The length of the fuel cell before and after the reduction and the contraction rate due to the reduction,
The results of Example 1 are shown in Table 1.

[0015]

[Table 1]

[Embodiment 2] FIG. 2 is a flow chart showing a manufacturing process of a solid oxide fuel cell according to another embodiment of the present invention.

Using the same YSZ powder and nickel oxide powder as in Example 1, a mixed powder of nickel oxide and YSZ in which the weight ratio of nickel oxide was 60% was prepared in the same manner as in Example 1. Next, 100 parts by weight of polyvinyl butyral as a binder and 10 parts by weight of di-n-butyl phthalate as a plasticizer were added to 100 parts of the mixed powder.
In addition, 100 to which a mixed solvent of toluene and isopropanol (23:77) was further added was mixed for 24 hours using a ball mill to prepare a slurry. The slurry is used to form a sheet with a doctor blade device having a blade height set to 1 mm, and after drying, the sheet is cut into a rectangle of a predetermined size so that these sheets have a predetermined thickness. Laminated. A hot press was used for pressure-bonding the laminate, and pressure-bonding was performed under the conditions of a pressure of 0.2 kg / cm ² , a temperature of 80 ° C., and a pressure time of 1 minute. Substrates thus laminated were degreased and sintered under the same conditions as in Example 1 to prepare a fuel electrode for a solid oxide fuel cell. And Example 1
Reduction was carried out in the same manner as in.

Further, in the same manner as in Example 1, an electrolyte and an oxidizer electrode were formed on the support fuel electrode to obtain a fuel cell. The length of this fuel battery cell was 100.2 mm. FIG. 3 is a perspective view showing the outer appearance of the fuel cell manufactured in this example. In the figure, 2 "is an oxidant electrode, 3" is an electrolyte, 6 "is an oxidant gas flow channel, 7" is a fuel gas flow channel,
Reference numeral 9 is a support fuel electrode, and 10 and 10 ″ are grooved interconnectors.

An interconnector 1 made of lanthanum chromite in which a fuel cell composed of an oxidizer electrode 2 ", an electrolyte 3" and a support fuel electrode 9 is provided with grooves for forming gas flow paths 6 ", 7".
It was sandwiched from above and below with 0, 10 ″, and further mounted on an alumina cell holder, and hydrogen and air were introduced as fuel gas under the same conditions as in Example 1 to carry out reduction of the support fuel electrode. The length of the fuel cell of No. 3 was 99.7 mm, and the contraction rate due to reduction was 0.5%.

[Comparative Example 2] As a comparative example, a fuel cell was manufactured by the following method without performing reduction treatment before forming an electrolyte membrane.

Using the same raw materials as in Example 2, the processes from mixing of raw materials to sintering were performed in the same manner as in Example 2. Without reducing the produced fuel electrode sintered body, the electrolyte membrane was sprayed in the oxidized state in the same manner as in Example 2, and further an oxidizer electrode was formed to produce a fuel cell. The length of this fuel battery cell was 100.2 mm. Next, in the same manner as in Example 2, the support fuel electrode was reduced in the cell holder. Length of fuel cell after reduction is 99.0m
It was m. Therefore, the contraction rate of the support fuel electrode due to the reduction treatment was 1.2%. The length of the fuel cell before and after the reduction and the shrinkage rate due to the reduction are shown in Table 2 together with the results of Example 2.

[0022]

[Table 2]

The molded body before sintering may be produced by a press molding method other than the extrusion molding method and the doctor blade method shown in the examples. Further, the shape of the support fuel electrode is, in addition to the hollow flat plate shape and the rectangle used in the examples, a cylindrical shape, a rectangular tube shape, a disk shape, a polygon other than the rectangular shape,
It may be a corrugated plate or the like. Further, the composition of the atmosphere gas in the reduction treatment before the production of the electrolyte membrane is preferably about nitrogen: hydrogen = 9: 1 in consideration of work safety and the like.
A gas having a higher hydrogen composition ratio may be used. When the flow rate of the atmosphere gas is high and the hydrogen composition ratio in the gas is high,
It may be less than 100 ml / min used in the examples, and conversely, when the hydrogen composition ratio is small, it is desirable to further increase the flow rate. Furthermore, the processing temperature during reduction is
If the temperature is too high, the sintering of the support fuel electrode will proceed and the gas permeability will decrease, and if the temperature is too low, the reduction treatment will take time, so a temperature of about 1000 ° C. is desirable.

[0024]

As described above, according to the method for producing a solid oxide fuel cell of the present invention, an electrolyte membrane is prepared on a support fuel electrode which has been reduced in advance,
By introducing the fuel gas into the solid oxide fuel cell after the production of the fuel cell, when reducing the support fuel electrode,
It is possible to reduce the contraction rate of the support fuel electrode.
As a result, generation of stress due to the difference in contraction behavior between the fuel electrode and the electrolyte is suppressed when the reduction is performed after the fuel cell is assembled, and the separation of the electrolyte from the support fuel electrode is less likely to occur. For this reason, the productivity of the solid oxide fuel cell is improved, and the reliability and durability of the solid oxide fuel cell are also improved, and an extremely large effect can be obtained from the industrial viewpoint.

[Brief description of drawings]

FIG. 1 is a flow chart showing a manufacturing process of a solid oxide fuel cell device according to an embodiment of the present invention.

FIG. 2 is a flow chart showing a manufacturing process of a solid oxide fuel cell device according to another embodiment of the present invention.

FIG. 3 is an exploded perspective view showing an appearance of a fuel cell according to another embodiment of the present invention.

FIG. 4 is a perspective view showing an example of a solid oxide fuel cell using a porous support.

FIG. 5 is a perspective view showing an example of a solid oxide fuel cell having an electrode as a support.

[Explanation of symbols]

1 ... Porous support, 2, 2 ', 2 "... Oxidizer electrode, 3,
3 ', 3 "... Electrolyte, 4 ... Fuel electrode, 4' ... Hollow flat plate support fuel electrode, 5, 5 ... Interconnector, 6, 6" ... Oxidant gas flow path, 7, 7 "... Fuel gas flow Road, 8 ... Dense film, 9
... Support fuel electrode 10,10 "... Grooved interconnector.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumi Manabe 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Himeko Kanagawa 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A method for producing a solid oxide fuel cell using a fuel electrode as a support, wherein a fuel electrode is produced by sintering, and then reduction treatment is performed, and then an electrolyte and an oxidant electrode are formed on the fuel electrode. A method for producing a solid oxide fuel cell, which is characterized by producing a fuel cell. 2. The method for producing a solid oxide fuel cell according to claim 1, wherein nickel zirconia cermet is used as the material of the fuel electrode.