JP2000067889A - Method for preparing interconnector film for solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an output loss following a contact resistance with a collector at the time of a power generation by an inexpensive wet method and realize a high output of a cell by forming a lanthanum chromite film on the oxidation atmosphere side and a nickel oxide film on the reduction atmosphere side and calcinating it. SOLUTION: In order to form an interconnector film of a solid electrolyte fuel cell, electric conductivity is outstandingly lowered on the reduction atmosphere side in an interconnector of only a lanthanum chromite on the reduction atmosphere side and since a nickel oxide is converted to nickel and a conductivity is enhanced when the nickel oxide film is provided on the reduction atmosphere side, it is preferable that a lanthanum chromite film is formed on the oxidation atmosphere side and the nickel oxide film is formed on the reduction atmosphere side. Then, a calcination temperature of the interconnector film is preferably 1300 to 1550 deg.C. Moreover, an average particle diameter of the nickel oxide powder is preferably 1-20 μm in order to prevent a calcination- breaking of the film and prepare a fine film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an interconnector film for a solid oxide fuel cell, which relates to providing a lanthanum chromite film on an oxidizing atmosphere side and a nickel oxide film on a reducing atmosphere side, followed by firing. In particular, the present invention relates to a method of manufacturing an interconnector film suitable for reducing contact resistance with a current collector during power generation of a fuel cell and reducing output loss due to Joule heat loss in an interconnector section.

[0002]

2. Description of the Related Art Heretofore, as a current collecting method of an interconnector made of lanthanum chromite, a power generation test was performed by directly joining lanthanum chromite and a current collector.

[0003] Japanese Patent Application Laid-Open No. 4-282566 discloses that an oxidation-resistant ceramic layer and a reduction-resistant metal layer are preferable as the structure of the interconnector.

[0004]

When current is collected by bringing the lanthanum chromite film into contact with the current collector, the contact resistance with the current collector increases, the output loss accompanying Joule heat loss increases, and a high output is obtained. Can not.

In Japanese Patent Application Laid-Open No. 4-282566, it is described that the structure of an interconnector comprises an oxidation-resistant ceramic layer and a reduction-resistant metal layer. However, when an interconnector film having this structure is used for a solid oxide fuel cell, Since it is difficult to perform sintering in an oxidizing atmosphere due to the provision of the method described above, it is difficult to fabricate by a normal wet method, and the manufacturing method is limited to a CVD / EVD method or a thermal spraying method. Although the interconnector film can be manufactured by these methods, it is necessary to form the film under special atmosphere and physical conditions shielded from the air, so that expensive equipment is required, and the film for large members is required. It is not practical because it is difficult to attach, the productivity is low, and the cost is high. Although a metal layer can be prepared by using a plating method, this method is also impractical because of the large number of steps, resulting in high cost.

According to the present invention, in the manufacture of an interconnector membrane for a solid oxide fuel cell, it is possible to reduce the output loss due to contact resistance with a current collector during power generation by an inexpensive wet method, and to increase the output of the cell. It is an object of the present invention to provide a method for producing an interconnector film that can be used.

[0007]

To achieve the above object, the present invention provides a method for forming an interconnector film of a solid oxide fuel cell, comprising a lanthanum chromite film on an oxidizing atmosphere side and a lanthanum chromite film on a reducing atmosphere side. A nickel oxide film is formed and fired.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In a typical application of the present invention, a porous ceramic substrate is an air electrode of a solid oxide fuel cell, and a somewhat dense ceramic substrate is an intermediate layer between the air electrode and an interconnector. Pre-coat layer)
And the interconnector is a co-sintered body of lanthanum chromite and nickel oxide. The interconnector of a solid oxide fuel cell is required to have the following properties.However, the method for forming a dense sintered film of lanthanum chromite and nickel oxide of the present invention is a method for forming such an interconnector. It is suitable. -High electrical conductivity. Since the role of the interconnector is to establish electrical continuity between the unit cells of the solid oxide fuel cell, it is the most basic requirement. If the electric conductivity is low, the self-consumption of electric power in the interconnector increases, and the power generation efficiency of the cell decreases. Electrical conductivity, 10S · cm at a film formation condition ^{- 1} or more (more preferably 40S · cm ^{- 1} or more) is required. -Low air permeability. Fuel gas (H ₂ , CO, etc.) and oxidant (air, etc.) flow on the front and back surfaces of the interconnector, but if these mix through the interconnector, the power generation performance of the cell will be reduced. Breathability is 0.01
(M ³ / m ² · hr · atm) or less (more preferably 0.
0001 (m ³ / m ² · hr · atm) or less).・ Durable in both oxidation and reduction.・ The thermal expansion coefficient is YSZ (yttria stabilized zirconia)
And similar to other cell components. -Low reactivity with air electrode materials such as LaSrMnO ₃ and LaCaMnO ₃ and YSZ. -It can be formed into a thin film. Since a current flows through the interconnector in the thickness direction, the thinner the resistance, the lower the resistance. A film thickness of 200 μm or less is required.

In the present invention, it is preferable to form a lanthanum chromite film on the oxidizing atmosphere side and to form a nickel oxide film on the reducing atmosphere side. The reason for this is that the electrical conductivity of the interconnector containing only lanthanum chromite is significantly reduced on the reducing atmosphere side, and that when a nickel oxide film is provided on the reducing atmosphere side, nickel oxide is changed to nickel and conductivity is improved.

In the present invention, the firing temperature of the interconnector film is preferably 1300 to 1550 ° C. The reason for this is that if the temperature is 1300 ° C. or less, the activity of the sintering aid of lanthanum chromite (calcium chromate for Ca doping, strontium chromate for Sr doping) is low, and it is difficult to obtain a dense film. This is because firing at a higher temperature than other materials is not practical in manufacturing a solid oxide fuel cell. In addition,
The atmosphere at the time of firing is preferably an Air atmosphere in consideration of other materials (particularly, air electrode materials).

In the present invention, the substance to be doped into lanthanum chromite is not particularly limited. Ca,
Sr, Mg, Co, Zn, Ti, Li and the like can be adopted.
The firing temperature of the interconnector film is 1300-1550
Lanthanum chromite containing Ca is preferred from the viewpoint of producing a dense film at a temperature of ° C.

In the present invention, the average particle size of the nickel oxide powder is preferably 0.1 to 20 μm. The reason is as follows.
If the thickness is smaller than 1 μm, the sintering property is too high, which may cause the film to be cut off or peeled off. If it is larger than 20 μm, the sintering property is too low, so that it is difficult to produce a dense film.

In the present invention, the method for synthesizing the powder for the lanthanum chromite film is not particularly limited. A coprecipitation method, a powder mixing method, a spray pyrolysis method, a sol-gel method, an evaporation to dryness method and the like can be employed. Among them, the spray pyrolysis method is preferred from the viewpoints of high uniformity of composition, low contamination of impurities such as silica and iron, and short working process (low cost).

[0014]

The present invention will be described more specifically below. FIG. 1 is a sectional view showing the structure of a cell of a cylindrical cell type solid oxide fuel cell according to one embodiment of the present invention. (A) is an overall longitudinal sectional view, and (B) is a transverse sectional view showing a BB section of (A).

The cell assembly 1 shown in FIG. 1 includes a cylindrical cell 3 and an air introduction pipe 5. The cylindrical cell 3 is a bottomed ceramic tube having a cross-section having a laminated structure and an open top and a closed bottom. The air introduction pipe 5 is a ceramic tube having a simple cross-sectional structure (for example, YS having a linear expansion coefficient substantially equal to that of the cylindrical cell 3)
Z or Al ₂ O ₃ which is excellent in thermal shock resistance). The air introduction tube 5 is inserted into the inner hole of the cylindrical cell 3 from the cell open end 21, and the tip of the air introduction tube 5 reaches near the bottom of the cell inner hole. The gap between the bottom of the cell 3 and the lower end 25 of the air introduction pipe 5 is 10 mm as an example. From the lower end 25 of the air introduction pipe 5, air (oxidizing agent) is supplied into the cell 3 as described above. The air rises inside the cell 3 and electrochemically reacts with the fuel gas existing outside the cell 3 to generate power.

The cross-sectional structure of the cell 3 will be described with reference to FIG. The cell 3 has a laminated structure of several layers (films). First, the air electrode 11 exists in the innermost ring shape. The air electrode 11 also has a role as a strength member (support) for supporting the cell. This air electrode 11
Is the Strontium Do Printemps Manga Night (LS
M) is a porous body. The air electrode 11 serves as a cathode while air passes through it.

Next, the solid electrolyte membrane 13 is present on the surface of the air electrode 11. This solid electrolyte membrane 13 has a part (interconnector 17,
18). The solid electrolyte membrane 13 is a dense membrane of yttria-stabilized zirconia (YSZ). The solid electrolyte membrane 13 has O ²⁻ ions passing therethrough,
It functions as a shielding film so that the air inside the cell 3 and the fuel gas outside the cell 3 are not directly mixed.

Next, the fuel electrode 15 exists in a substantially ring shape outside the solid electrolyte membrane 13. This fuel electrode 15
There is a part (part around the interconnectors 17 and 18) that is partially interrupted on the left side of the figure. The fuel electrode 15 is made of Ni
-YSZ cermet porous membrane. The fuel gas passes through the fuel electrode 15 and becomes an anode.

The interconnectors 17, 18 (FIG. 1)
(A), (B) left side is a film extending in the axial direction of the cell 3 in a band shape on the air electrode 11. Interconnector 17
Is a calcium dope lanthanum chromite film, and the interconnectors 18 are nickel oxide films, each of which is a dense film. The interconnectors 17 and 18 are connected to the air electrode to expose a conductive portion with the air electrode on the outer surface of the cell 3.
And plays a role of blocking the inside and outside of the cell 3. The interconnectors 17 and 18 are not in contact with the fuel electrode 15 to avoid conduction.

The intermediate layer 16 of the air electrode and the interconnector between the interconnector 17 and the air electrode 11
This layer is provided to suppress the diffusion of the sintering aid into the air electrode when the interconnector film is fired, and is preferably provided.

A current collector 19 made of Ni felt is arranged on the interconnector 18. The other surface of the current collector 19 is in contact with the fuel electrode surface 15 'of the left cell 3'.

Next, the results of a power generation performance test using a test cell
Will be described. A test cell was created under the following conditions.
Was. (1) Cell specifications-Type: Self-supporting air electrode type, cell outer diameter 13mm, cell
Length 200mm ・ Air electrode: Material La_0.75Sr_0.25MnO_Three, Outer diameter 13m
m, thickness 1.5mm, conductivity 100S ・ cm^{― 1}, Stoma
Extrusion rate → sintering 35% Solid electrolyte membrane: Material 8mol% Y2O3 stabilized Zr
O2, thickness 20μm, slurry coating → firing ・ Interconnector: Example: Material La_0.8Ca_0.2CrO_Three(40 μm thick,
Slurry coat → firing) NiO (thickness 20μm, slurry
In this example, a lanthanum chromite film was formed on the oxidizing atmosphere side.
The film is fired, and a nickel oxide film is formed on the reducing atmosphere side.
Lanthanum chromium on the oxidizing atmosphere side.
A nickel oxide film on the reducing atmosphere side
When co-firing, the material La_0.8Ca_0.2CrO_ThreeYou
And NiO, thickness 60 μm, conductivity 40 S · cm^{― 1},
Slurry coating → firing etc. can be considered. Comparative Example 1: Material La_0.8Ca_0.2CrO_Three, Thickness 40μ
m, conductivity 30S · cm ^{― 1}, Slurry coating → firing Comparative Example 2: Material La_0.8Ca_0.2CrO_ThreeAnd Ni, thickness
45 μm (La_0.8Ca_0.2CrO_Three40 μm film, slurry
Leacoat method, Ni film 5μm, electroless plating method), conductive
Rate 40Scm^{― 1} ・ Fuel electrode: Material YSZ ・ Ni cermet, thickness 60μ
m, conductivity 1400S · cm^-1, Porosity 40%, Slur
Leacoat → firing

(2) Manufacturing method Air electrode (support): An organic binder, glycerin and water were added to the above LSM powder and kneaded. Next, the compound was extruded. After the extrusion molding, the roundness was adjusted in a green state. Thereafter, drying and degreasing were performed, followed by firing at 1350 to 1500 ° C. for 10 hours.

-Interconnector film formation: Example: L is applied to the interconnector film formation section on the air electrode.
After a _0.8 Ca _0.2 MnO ₃ film is formed and fired, La _0.8 Ca _0.2
After forming a CrO ₃ film by slurry coating, it was baked at 1400 ° C. for 10 hours. An NiO film was formed thereon by slurry coating and baked at 1400 ° C. for 10 hours. In the case where a lanthanum chromite film is formed on the oxidizing atmosphere side, a nickel oxide film is formed on the reducing atmosphere side, and co-firing is performed, La _0.8 Ca is formed on the interconnector film forming portion on the air electrode.
After forming and firing a _0.2 MnO ₃ film, a La _0.8 Ca _0.2 CrO ₃ film is formed by a slurry coat, then a NiO film is formed by a slurry coat, and firing at 1400 ° C. for 10 hours is considered. Comparative Example 1: after forming fired La _0.8 Ca _0.2 MnO ₃ films interconnector film forming unit of the air superb, La _0.8 Ca
After forming a _0.2 CrO ₃ film by slurry coating, 1400
C. for 10 hours. Comparative Example 2: La _0.8 Ca _0.2 MnO ₃ film was formed on the interconnector film forming portion on the air electrode, and after firing, La _0.8 Ca
_{After a 0.2} CrO ₃ film was formed by slurry coating, a metal nickel film was formed by electroless plating. (Hereinafter referred to as metallization)

Solid electrolyte membrane formation: The YSZ was formed on the underlayer by slurry coating and baking. -Fuel electrode film formation: The above-mentioned Ni-YSZ cermet was formed on the above-mentioned solid electrolyte layer by slurry coating and firing.
The reduction treatment of NiO is performed by (H ₂ + 11% H ₂ O): N ₂
= 3: 97 at 1000 ° C for 3 hours in an atmosphere.

A current collector of Ni felt was mounted on the interconnector film in contact with the interconnector film, and the interconnector film and the current collector were adhered in the same atmosphere (described below) during the operation of the SOFC.

This cell was operated under the following conditions. (3) Power generation conditions ・ Fuel: (H ₂ + 11% H ₂ O) ・ Oxidizing agent: Air ・ Cell temperature: 1000 ° C. ・ Fuel utilization rate: 85%

(4) Test Results FIG. 2 shows that the interconnectors were La _0.8 Ca _0.2 CrO ₃
The SOFC cell of this example, in which the film was fired by slurry coating and then the NiO film was fired by slurry coating,
FIG. 5 is a graph comparing the power generation characteristics of the SOFC cell of Comparative Example 1 in which the interconnector was a La _0.8 Ca _0.2 CrO ₃ film and was not metallized and the SOFC cell of Comparative Example 2 in which the interconnector was metallized with a metal nickel film. is there. The horizontal axis indicates the current area density, and the vertical axis indicates the output area density. Note that the current density was changed by changing the resistance of the external circuit. As shown in FIG. 2, the peak of the output density is about 0.1 W / cm ^{2 in} the case of the metallization of Comparative Example 1 which is about 0.1 W / cm ² , whereas the peak of the output density is 0.3 W in the example and the comparative example 2. / C
The output was about three times as high as about m ² . This is because, in Comparative Example 1, the contact resistance at the interface between the interconnector and the current collector significantly increased with an increase in the current density, and the Joule loss in the same portion increased, whereas the contact resistance in Example and Comparative Example 2 decreased. Probably because it was low. As described above, as shown in this example, a lanthanum chromite film is formed and baked on the oxidizing atmosphere side, and a nickel oxide film is formed and baked on the reducing atmosphere side. It turned out to show the same performance as the connector.

[0029]

As described above, according to the present invention, in the interconnector of the solid oxide fuel cell, the lanthanum chromite is formed on the oxidizing atmosphere side and the nickel oxide is formed on the reducing atmosphere side and fired. In the case of an interconnector film, a cell having a high output density comparable to that obtained by metallizing the interconnector film can be produced. Further, an interconnector film exhibiting the same performance as an expensive method such as a plating method can be manufactured by an inexpensive wet method.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a cell (assembly) of a cylindrical cell type solid oxide fuel cell according to one embodiment of the present invention.

[Fig. 2] La _0.8 Ca _0.2 CrO ₃ interconnector
The SOFC cell of the present example in which the film was formed and fired with a slurry coat and then the NiO film was formed and fired with a slurry coat, and the SOFC cell of Comparative Example 1 in which the interconnector was a La _0.8 Ca _0.2 CrO ₃ film and metallization was not performed 9 is a graph showing a comparison between power generation characteristics of SOFC cells of Comparative Example 2 in which metallization was performed using an interconnector as a La _0.8 Ca _0.2 CrO ₃ film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cell assembly drawing 3 Cylindrical cell 5 Air introduction pipe 11 Air electrode 15 Fuel electrode 16 Intermediate layer between air electrode and interconnector 17 Interconnector (lanthanum chromite film) 18 Interconnector (nickel oxide film) 19 Current collector (Ni felt) 21 Cell top (open end) 25 Inlet tube tip

Claims (7)

[Claims] 1. A method for forming an interconnector film of a solid oxide fuel cell, comprising forming a lanthanum chromite film on an oxidizing atmosphere side and a nickel oxide film on a reducing atmosphere side, and firing. Method for producing interconnector membrane for solid oxide fuel cell. 2. A method for forming an interconnector film of a solid oxide fuel cell, comprising forming a lanthanum chromite film on an oxidizing atmosphere side, forming a nickel oxide film on a reducing atmosphere side, and co-firing. A method for producing an interconnector membrane for a solid oxide fuel cell, comprising: 3. A method for forming an interconnector film for a solid oxide fuel cell, comprising forming and firing a lanthanum chromite film on an oxidizing atmosphere side and forming and firing a nickel oxide film on a reducing atmosphere side. A method for producing an interconnector membrane of a solid oxide fuel cell, which is characterized in that: 4. The method for producing an interconnector film for a solid oxide fuel cell according to claim 1, wherein the interconnector film is formed by a wet method. 5. The method for producing an interconnector membrane for a solid oxide fuel cell according to claim 1, wherein the sintering temperature of the interconnector membrane is 1300 to 1550 ° C. 6. The method for producing an interconnector film for a solid oxide fuel cell according to claim 1, wherein the firing temperature of the lanthanum chromite film and the nickel oxide film is 1300 to 1550 ° C. 7. The nickel oxide powder used for the nickel oxide film has an average particle size of 0.1 to 20 μm.
7. The method for producing an interconnector membrane for a solid oxide fuel cell according to 6.