JP2001052725A - Material for peripheral member of cylindrical solid electrolyte fuel cell and cell making use of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for peripheral members of a cylindrical solid electrolyte fuel cell having high manufacturing efficiency and easy to maintain high durability, and a cell making use of it. SOLUTION: Plural films are formed by a porous fuel cell electrode 12 of a cermet obtained by mixing YSZ with Ni on the external peripheral surface of a base substance tube 11 having a porous cylindrical shape at a designated interval throughout its axial center direction, a porous solid electrolyte 13 of YSZ is formed into a film on the fuel cell electrodes 12, a porous air electrode 14 comprising a mixture obtained by mixing a perovskite compound oxide such as LaSrMnO3 with YSZ is formed into the solid electrolyte 13 in order to form a unit cell film, and a fine inter-connector 15 having a composition of strontium titanate perovskite compound oxide expressed by Sr1-xLaxTiO3 (provided, 0<x<=0.3) as a main ingredient is formed into a film between the unit cell films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a peripheral member of a cylindrical solid electrolyte fuel cell and a cell using the same.

[0002]

2. Description of the Related Art A schematic configuration of a cell of a cylindrical solid electrolyte fuel cell is shown in FIG.

As shown in FIG. 8, on the outer peripheral surface of a porous cylindrical base tube 111, a porous cermet made of a mixture of nickel and yttria-stabilized zirconia (hereinafter referred to as "YSZ") is provided. A plurality of fuel electrodes 112 are formed at predetermined intervals along the axial direction of the base tube 111. On these fuel electrodes 112, a porous solid electrolyte 113 made of YSZ is formed. On these solid electrolytes 113, a porous air electrode 114 made of a mixture of a perovskite-type composite oxide such as strontium-added lanthanum manganite (LaSrMnO ₃ ) and YSZ is formed. That is, a plurality of unit cell films composed of the fuel electrode 112, the solid electrolyte 113, and the air electrode 114 are formed on the outer peripheral surface of the base tube 111 at predetermined intervals in the axial direction.

A dense interconnector 115 made of a lanthanum chromite (LaCrO ₃ ) -based perovskite oxide is formed between adjacent unit cells, and one interconnector 115 is connected to one of the interconnectors. Fuel electrode 112 of one unit cell membrane and air electrode 1 of the other unit cell membrane
14 is connected. That is, the interconnector 11
Reference numeral 5 indicates that the unit cell membranes are connected in series.

In such a cylindrical solid electrolyte fuel cell, a cell is heated to a predetermined temperature (900 to 1000 ° C.), and a fuel gas such as hydrogen is supplied to the inside of the base tube 111. When an oxidizing gas such as air is supplied to the outside of the tube 111, the fuel gas and the oxidizing gas electrochemically react in the unit cell membrane, so that electric power can be obtained.

[0006]

As described above, the cells of the cylindrical solid electrolyte fuel cell are operated in a high temperature environment (900 to 900).
1000 ° C.) and exposed to an oxidizing and reducing atmosphere. For this reason, a conductive material that is chemically stable even in a high-temperature reducing atmosphere and has a small difference in thermal expansion coefficient from the solid electrolyte 113 is applied to the fuel electrode 112, and a chemical material is used in the air electrode 114 even in a high-temperature oxidizing atmosphere. A conductive material that is stable in terms of temperature and has a small difference in thermal expansion coefficient from the solid electrolyte 113 is used. In particular, the interconnector 115 must be made of a conductive material that is chemically stable even in a high-temperature oxidizing atmosphere and a high-temperature reducing atmosphere and has a small difference in thermal expansion coefficient from the electrodes 112 and 114 and the solid electrolyte 113. LaCrO like
_Three perovskite oxides are currently used.

However, the LaCrO ₃ -based perovskite oxide has the following problems. (1) Since the expansion coefficient in the reducing atmosphere is larger than the expansion coefficient in the oxidizing atmosphere, distortion occurs between the oxidizing atmosphere side and the reducing atmosphere side, and the durability may be reduced. (2) Since the sintering temperature is high and it is difficult to integrally sinter with other materials, the manufacturing efficiency is low and the cost is high.

In view of the above, the present invention provides a material for peripheral members of a cylindrical solid electrolyte fuel cell which has high production efficiency and can easily maintain high durability, and an interconnector and a cell using the same. The purpose was.

[0009]

In order to solve the above-mentioned problems, the material of the peripheral members of the cylindrical solid electrolyte fuel cell according to the present invention is Sr _{1 -x} La _x TiO ₃ (where 0 <
(x ≦ 0.3) is a main component.

The material of the peripheral member of the above-mentioned cylindrical solid oxide fuel cell is characterized in that MgAl ₂ O ₄ is contained in y volume% (where 0 <y ≦ 30).

In the above-mentioned material for the peripheral member of the cylindrical solid electrolyte fuel cell, the peripheral member is an interconnector.

Further, in the cell of the cylindrical solid electrolyte fuel cell according to the present invention, a unit cell membrane composed of a fuel electrode, a solid electrolyte, and an air electrode is provided on an outer peripheral surface of a base tube at a predetermined interval through an interconnector in the axial direction. Wherein the interconnector has a main component of a composition represented by Sr _1-x La _x TiO ₃ (where 0 <x ≦ 0.3). It is characterized by.

[0013] In the above-mentioned cell of the cylindrical solid electrolyte fuel cell, the interconnector is characterized by containing MgAl ₂ O ₄ by y volume% (where 0 <y ≦ 30).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of materials for peripheral members of a cylindrical solid oxide fuel cell according to the present invention and a cell using the same will be described below, but the present invention is limited to the following embodiments. Not something.

First Embodiment A first embodiment of a material for peripheral members of a cylindrical solid oxide fuel cell according to the present invention and a cell using the same will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a main part of a cell.

As shown in FIG. 1, on the outer peripheral surface of a porous cylindrical base tube 11, a porous cermet made of a mixture of nickel and yttria-stabilized zirconia (hereinafter referred to as "YSZ") is provided. Of the fuel electrode 12 is
A plurality of films are formed at predetermined intervals over one axial direction. On these fuel electrodes 12, a porous solid electrolyte 13 made of YSZ is formed. On these solid electrolytes 13, a porous air electrode 14 made of a mixture of a perovskite-type composite oxide such as strontium-doped lanthanum manganite (LaSrMnO ₃ ) and YSZ is formed. That is, a plurality of unit cell films composed of the fuel electrode 12, the solid electrolyte 13, and the air electrode 14 are formed on the outer peripheral surface of the base tube 11 at predetermined intervals in the axial direction.

In addition, Sr is provided between adjacent cells.
_A dense interconnector 15 which is a peripheral member mainly composed of a strontium titanate-based perovskite-type composite oxide represented by _1-x La _x TiO ₃ (where 0 <x ≦ 0.3) is used. The interconnector 15 is connected to the fuel electrode 12 of one unit cell membrane and the air electrode 14 of the other unit cell membrane. That is,
The interconnector 15 connects the unit cell membranes in series.

In such a cylindrical solid electrolyte fuel cell, a cell is heated to a predetermined temperature (900 to 1000 ° C.), and a fuel gas such as hydrogen is supplied to the inside of the base tube 11. When an oxidizing gas such as air is supplied to the outside of the tube 11, the fuel gas and the oxidizing gas electrochemically react in the unit cell membrane, and electric power can be obtained.

Here, Sr _1-x La _x TiO ₃ (where 0 <x ≦ 0.3) has a small difference between the expansion coefficient in a reducing atmosphere and the expansion coefficient in an oxidizing atmosphere, and has a low sintering temperature. Therefore, in the interconnector 15 having such a composition as a main component, no distortion occurs between the oxidizing atmosphere side and the reducing atmosphere side, and the interconnectors 15, the solid electrolyte 13, etc. It can be easily sintered together.

Therefore, according to the cell using the material of the peripheral member of the cylindrical solid electrolyte fuel cell for the interconnector, high durability can be maintained and the production efficiency can be improved.

In this embodiment, an interconnector is exemplified as a peripheral member. However, the present invention is not limited to this. For example, a dense current-carrying member applied to a cylindrical solid electrolyte fuel cell is used. Can also be applied.

[Second Embodiment] A second embodiment of a material for peripheral members of a cylindrical solid oxide fuel cell according to the present invention and a cell using the same will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of a main part of the cell.
However, the same members as those in the first embodiment described above are denoted by the same reference numerals as those used in the description of the first embodiment, and description thereof is omitted.

As shown in FIG. 2, Sr _1-x La _x TiO ₃ (where 0 <x ≦ 0.
The composition of the strontium titanate-based perovskite complex oxide represented by 3) as a main component is MgAl ₂ O ₄
Are densely interconnected, which are peripheral members containing y volume% (where 0 <y ≦ 30).

Here, MgAl_TwoO_FourIs the y volume% (just
0 <y ≦ 30) Sr added _1-xLa_xTiO_Three
(However, 0 <x ≦ 0.3) is better than when it is not added.
When the coefficient of thermal expansion decreases and y = 30, the conventional material
LaCrO_ThreeSlightly lower coefficient of thermal expansion than
To be suppressed.

Therefore, according to the cell using the material of the peripheral member of the cylindrical solid electrolyte fuel cell for the interconnector, the same effect as that of the first embodiment can be obtained. Needless to say, since the thermal expansion coefficient of the interconnector can be suppressed, the durability can be further improved.

[0026]

EXAMPLE In order to confirm the effects of the materials of the peripheral members of the cylindrical solid electrolyte fuel cell according to the present invention and the cells using the same, the following confirmation tests were conducted.

[Test 1: Reactivity with materials of other members] Strontium carbonate (SrCO ₃ ), lanthanum oxide (La)
₂ O ₃ ) and titanium dioxide (TiO ₂ ) using Sr _0.9
La _0.1 TiO ₃ (hereinafter referred to as "SLT".) To synthesize. Next, SLT is mixed with each of NiO (fuel electrode material), YSZ (solid electrolyte material), and LaSrMnO ₃ (air electrode material) (mixing ratio is 1: 1:
1) After performing X-ray diffraction measurement of these powders, heat treatment (1400 ° C. × 5 hours) is performed. Thereafter, X-ray diffraction measurement of these powders is performed again, and measurement data before and after the heat treatment are compared. Thus, the presence or absence of a reaction product due to the heat treatment was confirmed.

As a result, it was found that SLT did not form a reaction product with the above materials. Therefore, even if SLT is used as a material for an interconnector, it can be said that SLT is stable without reacting with other members at the time of manufacture.

[Test 2: Sinterability] 1400 ° C., 1440
The densities of the SLT sintered at each of the temperatures of 1 ° C. and 1470 ° C. were measured by the Archimedes method. The result is shown in FIG. For comparison, the densities of LaCrO ₃ sintered at temperatures of 1400 ° C. and 1500 ° C. were also measured by the Archimedes method.

As can be seen from FIG. 3, the relative density of SLT was larger than that of LaCrO ₃ . Therefore, S
LT has higher sinterability than LaCrO ₃ and can be said to be easily sintered.

[Test 3: Thermal expansion] MgAl ₂ was added to SLT.
O ₄ is added at various ratios (0 vol%, 10 vol%, 20 vol%, and 30 vol% in four patterns) and sintered (140%).
(0 ° C.), and cut out into a rod shape (3 × 4 × 14 mm) to determine the coefficient of thermal expansion (atmosphere: air, temperature: 1000 ° C.). FIG. 4 shows the results. The thermal expansion coefficient of LaCrO ₃ is 9.5 × 10 ⁻⁶ / ° C. (literature value).

[0032] As can be seen from Figure 4, the coefficient of thermal expansion as the additive amount of MgAl ₂ O ₄ is increased is reduced, MgAl ₂
When the added amount of O ₄ is 30% by volume, the coefficient of thermal expansion becomes 9.4.
× 10 ⁻⁶ / ° C., a value slightly smaller than the coefficient of thermal expansion of LaCrO ₃ . Therefore, the low thermal expansion material Mg
By adding Al ₂ O ₄ , the coefficient of thermal expansion of SLT is suppressed, which is more preferable from the viewpoint of thermal expansion.

[Test 4: Swellability in reducing atmosphere] SLT
SL and 30 vol% of MgAl ₂ O ₄ added
T (hereinafter referred to as “SLT-MA”) is sintered (1400).
° C) and cut out into a rod shape, and by comparing the length of the sample before and after reduction, the expandability in a reducing atmosphere (reduction expansion coefficient) was determined. The result is shown in FIG. For comparison, the reduction expansion coefficient of LaCrO ₃ was also determined. Further, it is generally said that the reduction expansion coefficient allowable as a material of the interconnector is within ± 0.1%.

As can be seen from FIG. 5, LaCrO ₃ is
While the reduction expansion coefficient was 0.17%, SLT had a reduction expansion coefficient of -0.044%, and SLT-MA had a reduction expansion coefficient of 0.007%. Therefore, it can be said that SLT and SLT-MA have a reduction expansion coefficient that does not cause any problem as a material of the interconnector.

[Test 5: Cracking property during reduction heat cycle] SLT-MA slurry was applied to a base tube, sintered (1400 ° C) and then reduced (900 ° C). Was not observed. When the cracking property during the reduction heat cycle was examined using LaCrO ₃ in the same manner as described above, LaCrO ₃ did not sinter at 1400 ° C. and thus was not compared.

[Test 6: Dependence of coefficient of thermal expansion on composition ratio]
Property] x is set to various values (0.05, 0.1, 0.2, 0.3
Sr) _1-xLa_xTiO_ThreeHeating
(1000 ° C.), the coefficient of thermal expansion was measured. as a result
Is shown in FIG.

As can be seen from FIG. 6, even if the value of x was changed within the above range, there was no significant change in the coefficient of thermal expansion.
Therefore, if the value of x is within the above range, Sr _1-x La _x
It can be said that the thermal expansion coefficient of TiO ₃ hardly depends on the composition ratio.

[Test 7: Dependence of electric conductivity on composition ratio]
Property] x is set to various values (0.05, 0.1, 0.2, 0.3
Sr) _1-xLa_xTiO_ThreeConductivity
(Atmosphere: air and reducing atmosphere, temperature: 900 ° C)
Each was measured. FIG. 7 shows the result.

As can be seen from FIG. 7, the value of x is between 0.1 and
When it was between 0.2 and 0.2, the conductivity became maximum in both the air atmosphere and the reducing atmosphere. Therefore, from the viewpoint of conductivity, it can be said that the value of x is most preferably in the range of 0.1 to 0.2.

[0040]

The material of the peripheral member of the cylindrical solid oxide fuel cell according to the present invention is mainly composed of a composition represented by Sr _1-x La _x TiO ₃ (where 0 <x ≦ 0.3). Therefore, the peripheral member does not generate distortion between the oxidizing atmosphere side and the reducing atmosphere side, and can be easily sintered integrally with another member such as an electrode or a solid electrolyte. As a result, high durability can be maintained and manufacturing efficiency can be increased.

Further, since MgAl ₂ O ₄ is contained in y volume% (where 0 <y ≦ 30), the coefficient of thermal expansion of the peripheral members can be suppressed, and the durability can be further improved.

If the peripheral member is an interconnector, the above-described effects can be exhibited most efficiently.

In the cell of the cylindrical solid electrolyte fuel cell according to the present invention, a plurality of unit cell membranes composed of a fuel electrode, a solid electrolyte, and an air electrode are provided on an outer peripheral surface of a base tube at predetermined intervals through an interconnector in an axial direction. In the cell of the formed cylindrical solid electrolyte fuel cell, the interconnector is Sr.
_{Since the} composition represented by _1-x La _x TiO ₃ (where 0 <x ≦ 0.3) is the main component, the interconnector does not generate distortion between the oxidizing atmosphere side and the reducing atmosphere side. Further, it can be easily sintered integrally with an electrode, a solid electrolyte or the like. As a result, high durability can be maintained and manufacturing efficiency can be increased.

The interconnector is made of MgAl ₂ O.
_{Since 4} is contained in y volume% (where 0 <y ≦ 30), the coefficient of thermal expansion of the interconnector can be suppressed, and the durability can be further increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a first embodiment of a cell of a cylindrical solid oxide fuel cell according to the present invention.

FIG. 2 is a schematic configuration diagram of a main part of a second embodiment of a cell of a cylindrical solid oxide fuel cell according to the present invention.

FIG. 3 Sr _0.9 La _0.1 TiO ₃ and LaCrO ₃
3 is a graph showing a relationship between a sintering temperature and a relative density of the sintering.

FIG. 4 MgAl ₂ to Sr _0.9 La _0.1 TiO _3
4 is a graph showing the relationship between the addition ratio of O ₄ and the coefficient of thermal expansion.

FIG. 5 is a graph showing a reduction expansion coefficient of each material.

FIG. 6 is a graph showing the relationship between the ratio of La in Sr _1-x La _x TiO ₃ and the coefficient of thermal expansion.

FIG. 7 is a graph showing the relationship between the ratio of La in Sr _1-x La _x TiO ₃ and conductivity.

FIG. 8 is a schematic configuration diagram of a main part of an example of a cell of a conventional cylindrical solid electrolyte fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Base pipe 12 Fuel electrode 13 Solid electrolyte 14 Air electrode 15, 25 Interconnector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Sawada 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd. Basic Technology Research Institute (72) Inventor Toshiro Nishi 5-717 Fukahoricho, Nagasaki-shi, Nagasaki No. 1 Sanshige Kogyo Co., Ltd. Nagasaki Laboratory F-term (reference) 5H026 AA06 CV02 EE13 HH05

Claims (5)

[Claims] 1. Sr _1-x La _x TiO ₃ (where 0 <
(x ≦ 0.3) as a main component, a material for peripheral members of a cylindrical solid oxide fuel cell. 2. The material for a peripheral member of a cylindrical solid electrolyte fuel cell according to claim 1, wherein the material contains MgAl ₂ O ₄ in y volume% (0 <y ≦ 30). Of peripheral members of a solid electrolyte fuel cell. 3. A material for a peripheral member of a cylindrical solid electrolyte fuel cell according to claim 1, wherein the peripheral member is an interconnector. . 4. A unit comprising a fuel electrode, a solid electrolyte, and an air electrode
The battery membrane is interconnected on the outer peripheral surface of the base tube in the axial direction.
Cylindrical solid with multiple films formed at predetermined intervals through a connector
In a cell of an electrolyte fuel cell, the interconnector
Sr_1-xLa _xTiO_Three(However, 0 <x ≦ 0.3)
Cylinder characterized by having the composition represented by the main component
Type solid electrolyte fuel cell. 5. The cylindrical solid electrolyte fuel cell according to claim 4, wherein the interconnector is made of MgAl _2.
A cell of a cylindrical solid oxide fuel cell, characterized by containing y volume% of O ₄ (where 0 <y ≦ 30).