JPH1064565A - Solid electrolytic fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interconnector fine at such a temperature as exerting no damage to any battery composing material by fining the interconnector for providing connection between single elements by means of a slurry co- sintering method in a solid electrolytic fuel cell. SOLUTION: Oxide powder in which each nitrate of La, Sr, Cr is doped in LaCrO3 group perovskite type oxide is used for the interconnector of a solid electrolytic fuel cell. Or, furthermore, YSZ(yttria stabilized zirconium) is mixed in this powdery material. This mixed powder is formed in a disc shape, etc., and pressurized, and then sintered by the slurry co-sintering method. In this way, an interconnector with high relative density can be obtained. When PSZ or TiO is mixed is LaCrO3 group oxide in which alkaline earth metal is doped, fine substance can be obtained by sintering. Furthermore, by composing them in a mixture consisting of LaCrO3 group material and aluminum phosphate, hydrogen gas leakage quantity can be reduced under their operational condition.

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 (SOFC) having a good interconnect.

[0002]

2. Description of the Related Art In general, in a solid oxide fuel cell, an oxygen ion conductive solid electrolyte provided with electrodes is heated from 800.degree.
2,000 ℃ high temperature, this solid electrolyte as a partition,
A fuel gas is supplied to the ions, and air is supplied to the other, and an electrochemical reaction proceeds between the air electrode and the fuel electrode provided on both surfaces of the solid electrolyte type to extract electric power to the outside.

The cell structure of this solid oxide fuel cell is as follows:
Forming a fuel electrode, an electrolyte and an air electrode on a cylindrical base tube,
Using this as a single element, an interconnector for electrically connecting (series or parallel) the single elements is formed.

[0004] Here, the above-mentioned interconnector needs a role of a dense structure and an electronic conductor capable of blocking an oxidizing atmosphere and a reducing atmosphere, and has a thermal expansion coefficient equal to that of other constituent materials. It is necessary that it does not react with other battery constituent materials under an operating atmosphere. For this reason, LaCrO ₃ -based perovskite oxides have been conventionally used.

[0005] Further, in a method of manufacturing a fuel cell, an oxide slurry of an oxidizing material as a constituent material is formed for each constituent film and then integrally sintered at 1400 ° C.

[0006] Further, since the interconnector connects a single element, the following characteristics are required. A dense structure that prevents air and fuel leaks. High conductivity in both redox atmospheres. The coefficient of thermal expansion at the operating temperature and atmosphere should match that of the electrolyte. It should not expand in a reducing atmosphere.

[0007]

However, as described above, a LaCrO ₃ -based perovskite oxide has been used as an interconnector material, but this oxide is difficult to sinter and has a low sintering temperature. 1600 to improve
Although a temperature of at least ° C is required, firing at such a temperature simultaneously with other constituent materials is not suitable for practical use because other battery constituent materials are thermally damaged.

It is an object of the present invention to provide a solid oxide fuel cell having an interconnector formed at a temperature that is structurally stable even in a reducing atmosphere and does not damage the battery constituent materials.

[0009]

A first solid oxide fuel cell according to the present invention, which achieves the above object, comprises a single element comprising a fuel electrode, an electrolyte and an air electrode on a cylindrical base tube; A solid oxide fuel cell comprising an interconnector for electrically connecting the single elements, wherein the interconnector is densified by a slurry co-sintering method.

A second solid oxide fuel cell according to the present invention comprises:
In the first solid oxide fuel cell, the interconnect is made of a LaCrO ₃ -based oxide doped with alkaline earth.

A third solid oxide fuel cell according to the present invention comprises:
In the second solid oxide fuel cell, the interconnector may contain 30-40% by weight of YSZ (yttria-stabilized zirconia) and PSZ (partially stabilized zirconia) based on an alkaline earth-doped LaCrO ₃ -based oxide material.
Are mixed.

A fourth solid oxide fuel cell according to the present invention comprises:
In the first solid oxide fuel cell, said interconnector _{La 1-X M X CrO 3} (M here is an alkaline earth, x is a 0 to 0.2.), The mixture of TiO ₂ It is characterized by becoming.

According to the present invention, a dense film can be formed by sintering by the slurry co-sintering method. Here, in the present invention, the slurry co-sintering method refers to a solution obtained by mixing an oxide powder, a solvent, and a dispersion, and forms a slurry having a predetermined size in a base tube before sintering. After forming a film, it means sintering in one firing step to produce a cell. In addition,
The firing temperature is referred to as the co-sintering temperature.

A fifth solid oxide fuel cell according to the present invention comprises:
In the method for manufacturing a solid oxide fuel cell comprising a single element comprising a fuel electrode, an electrolyte and an air electrode on a cylindrical base tube and an interconnector for electrically connecting the single elements, The connector is made of a mixture of LaCrO ₃ -based material and aluminum phosphate.

According to the present invention, LaC having a small reduction expansion is used.
By adding aluminum phosphate as a sintering aid to the rO ₃ -based perovskite-type composite oxide, it is possible to produce a cell that is dense, does not undergo expansion breakdown even in a reducing atmosphere, and has little hydrogen leak.

[0016]

Embodiments of the present invention will be described below in detail.

Example 1 (La _0.9 Sr _0.1 ) CrO ₃ was used as an interconnector material. In the synthesis of the powder, the respective nitrates of La, Sr, and Cr as alkaline earth metals were weighed and mixed with distilled water to prepare an aqueous solution so that the amount of Sr substituted on the A site La was 10 mol%. This aqueous solution was heated in air at 150 ° C. to 200 ° C. and fitted by evaporation, and then calcined in air at 900 ° C. for 5 hours to obtain a single perovskite oxide. This perovskite oxide has an average particle size of
It is about 0.5 μm.

Next, YSZ (8 mol% Y ₂ O ₃ stability ratio) having an average particle size of 0.3 μm was added to the synthesized interconnector powder.
The powder was mixed at 0%, 20%, 30% and 40% by weight in weight%, and this mixed powder was mixed with a powder having a diameter of 2%.
It is molded into a disk having a thickness of 0 mm and a thickness of 1 mm, and is pressurized with a hydrostatic press at a pressure of 100 kg / cm ^2.
It was baked at 0 ° C. for 2 hours.

FIG. 1 shows the relationship between the YSZ powder concentration and the density of the mixed sintered body. When the YSZ was 30% or more, a relative density of about 92% was obtained. The density of the interconnector material and zirconia used was about 6 g / cm ³ , which was the same for both. Therefore, the relative density was measured by Archimedes method using the sintered pellet of the mixture.

Example 2 Body oxide prepared by dissolving ₃ mol% of Y ₂ O ₃ in PSZ (partially stabilized zirconia; ZrO ₂ ) having an average particle diameter of 0.3 μm was added to the interconnector powder produced in Example 1. Product) The powders were mixed at 0%, 20%, 30% and 40% by weight, and the mixed powder was molded into a disk having a diameter of 20 mm and a thickness of 1 mm, and then pressed under hydrostatic pressure. After pressurizing with a pressure device at a pressure of 100 kg / cm ² , it was fired in air at 1400 ° C. for 2 hours.

FIG. 1 shows the relationship between the PSZ powder concentration and the density of the mixed sintered body. When the PSZ was 30% or more, a relative density of about 95% was obtained.

Example 3 A single perovskite oxide having an average particle size of about 0.5 μm was obtained in the same manner as in Example 1.

Next, TiO ₂ powder having an average particle size of 0.3 μm was added to the synthesized interconnector powder in a weight% of 1% by weight.
3% by weight, 5% by weight and 10% by weight are mixed,
This mixed powder was molded into a disk having a diameter of 20 mm and a thickness of 1 mm, pressed with a hydrostatic pressure device at a pressure of 100 kg / cm ² , and then fired in air at 1400 ° C. for 2 hours.

[0024] Figure 2 shows a relationship between the density of the TiO ₂ powder concentration and the mixed sintered body, about 95% TiO ₂ is less than 3%
Was obtained.

Example 4 A single perovskite oxide having an average particle size of about 0.5 μm was obtained in the same manner as in Example 1. The obtained perovskite-type oxide and aluminum phosphate were mixed at a weight ratio of 7: 3, and this mixture and distilled water were mixed at a ratio of 1: 1 to form a slurry.

Length 40 mm, outer diameter 21 mm, inner diameter 17
The slurry was applied on a zirconia base tube having a thickness of 1 mm, dried at room temperature, and then fired at 1400 ° C. in the atmosphere.

A slurry of (La _0.9 Sr _0.1 ) CrO ₃ was prepared without mixing aluminum phosphate, and the slurry was applied on a zirconia base tube having a length of 40 mm, an outer diameter of 21 mm and an inner diameter of 17 mm, and dried at room temperature. After that, firing was performed at 1400 ° C. in the air.

With respect to these coated substrate tubes, the amount of hydrogen gas leak was examined. FIG. 3 shows an outline of the leak inspection apparatus. In FIG. 3, reference numeral 11 denotes an interconnector-coated base tube, 12 denotes a support tube, 13 denotes a cap, 14
Denotes an electric furnace, 15 denotes a hydrogen gas flow meter, 16 denotes a nitrogen gas flow meter, 17 denotes a hydrogen exhaust, and 18 denotes a nitrogen exhaust.

In the inspection method, hydrogen was flowed at 100 cc / min inside one of the base tubes 11, and nitrogen was flowed at 100 cc / min outside the base tubes 11. Temperature 1
The temperature was raised to 000 ° C., and nitrogen gas outside the base tube 11 was subjected to gas chromatography analysis to measure the amount of hydrogen leak. The results are shown in Table 1 below.

[0030]

[Table 1]

As is clear from the results in Table 1, the hydrogen gas leak amount of the interconnector mixed with aluminum phosphate was about 1.8% at 1000 ° C., which was extremely good. Leaked about 15%.

[0032]

As described above in detail with the embodiments of the present invention, according to the present invention, the interconnector is sintered by the slurry co-sintering method.
Can provide a precise one.

The interconnector is made of LaCrO ₃ -based oxide doped with alkaline earth,
Since YSZ or PSZ is mixed by weight%, a material having a higher relative density can be obtained.

Similarly, by mixing TiO ₂ with LaCrO ₃ -based oxide, a dense one can be provided.

Further, by using a mixture of a LaCrO ₃ material and aluminum phosphate, the amount of hydrogen gas leak can be reduced under operating conditions.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a YSZ powder concentration and a density of a mixed sintered body according to Example 1.

FIG. 2 is a graph showing a relationship between a Ti addition amount and a relative density according to Example 2.

FIG. 3 is a schematic diagram of an apparatus for inspecting a hydrogen gas leak amount according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Interconnector coating base pipe 12 Support pipe 13 Cap 14 Electric furnace 15 Hydrogen gas flow meter 16 Nitrogen gas flow meter 17 Hydrogen exhaust 18 Nitrogen exhaust

Claims (5)

[Claims] 1. A solid electrolyte fuel cell comprising a single element comprising a fuel electrode, an electrolyte and an air electrode on a cylindrical base tube and an interconnector for electrically connecting the single elements. A solid oxide fuel cell, wherein the interconnector is densified by a slurry co-sintering method. 2. The solid oxide fuel cell according to claim 1, wherein the interconnect is La-doped with alkaline earth.
A solid oxide fuel cell comprising a CrO ₃ -based oxide. 3. The solid oxide fuel cell according to claim 2, wherein said interconnect is La-doped with alkaline earth.
30-40% by weight of YSZ in CrO ₃ -based oxide material
A solid oxide fuel cell comprising a mixture of (yttria stabilized zirconia) and PSZ (partially stabilized zirconia). 4. The solid oxide fuel cell according to claim 1, wherein said interconnect is La _{1 -X} MX CrO ₃ (where M is an alkaline earth and x is 0 to 0.2). )
A solid oxide fuel cell characterized by mixing TiO ₂ . 5. Production of a solid oxide fuel cell comprising a single element composed of a fuel electrode, an electrolyte and an air electrode on a cylindrical base tube and an interconnector for electrically connecting the single elements. in the method, the solid electrolyte type fuel cell, characterized in that the interconnector is made of a mixture of a LaCrO ₃ system material and aluminum phosphate.