JP2015053146A - Fuel electrode supported solid oxide fuel cell and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly durable fuel electrode supporting solid oxide fuel cell having a high output density, the strength of which is less likely to lower even if the fuel cell is exposed repeatedly to reduction atmosphere/oxidation atmosphere.SOLUTION: A fuel electrode supporting solid oxide fuel cell 100 has a fuel electrode 10, a solid oxide electrolyte film 20, an air electrode 30. The fuel electrode 10 includes a porous structure consisting of a solid oxide, and an aggregate of electrode particles having electrode catalytic ability and dispersed into the cavities of the porous structure. In the plan view of the fuel electrode 10 from the exposed surface of the solid oxide electrolyte film 20, the porous structure and the aggregate of electrode particles are distributed in patchy, and the area of the porous structure to that of the fuel electrode is 10-50% in the plan view.

Description

  The present invention relates to a fuel electrode-supported solid oxide fuel cell and a method for manufacturing the same.

  A solid oxide fuel cell (hereinafter referred to as a power source) that generates electricity by supplying a combustible gas such as hydrogen and an oxidizing gas containing oxygen to a fuel cell configured by separating a fuel electrode and an air electrode with a solid oxide electrolyte , Referred to as SOFC). This SOFC is expected to be a next-generation fuel cell because it has high power generation efficiency because of its high-temperature operation, and it can also generate power using fuel gas other than pure hydrogen.

  The SOFC mainly has an electrolyte support cell with a thick electrolyte and a fuel electrode support cell with a thick fuel electrode. Since the electrolyte has a large internal resistance during power generation, the electrolyte is used for the purpose of improving battery characteristics. A fuel electrode-supported cell that can reduce the thickness of the electrode is becoming widespread.

As the combustion electrode of the fuel electrode support type cell, nickel oxide (NiO, which is metal Ni when the fuel cell is operated) having an average particle diameter of about 1 μm and zirconia (ZrO ₂ ) fine particles having an average particle diameter of about 0.5 μm are used. Nickel-zirconia cermet obtained by mixing is known.

  Patent Document 1 includes a mixture of a zirconia coarse particle group, a zirconia fine particle group, and a nickel or nickel oxide particle group, and the particle size of each particle group is zirconia coarse particle> nickel or nickel oxide particle> zirconia. A fuel electrode material characterized by satisfying the relationship of fine particles, wherein a weight ratio of the zirconia coarse particles, the nickel or nickel oxide particles, and the zirconia fine particles is 7 to 4: 3 to 6: 1 is described. Yes. According to Patent Document 2, for example, in this fuel electrode material, YSZ coarse particles and NiO particles are first mixed for about 48 to 60 hours, and then the YSZ fine particle group is added to the mixture and further mixed for about 48 hours. Can be obtained.

JP 2009-224346 A

  Since hydrogen is supplied to the fuel electrode during the operation of the SOFC, the fuel electrode is in a reducing atmosphere. However, when the engine is stopped, air reaches the fuel electrode, so that the fuel electrode has an oxidizing atmosphere. Therefore, the fuel electrode is repeatedly exposed to the reducing atmosphere / oxidizing atmosphere repeatedly in the process of use where the SOFC is repeatedly turned on and off, and in the oxidizing atmosphere, Ni that is the electrode particles of the fuel electrode is oxidized to NiO. The volume of the particles will expand. This irreversible expansion of the electrode particles causes the deterioration of the strength of the fuel electrode, which is a cause of impairing the battery characteristics and life of the SOFC. In addition, Ni particles gradually agglomerate during the repetitive process of the reducing atmosphere / oxidizing atmosphere, which is a cause of deterioration of the battery characteristics of the SOFC.

  Therefore, there is a demand for a fuel electrode that does not deteriorate in strength even when repeatedly exposed to a reducing atmosphere / oxidizing atmosphere. However, according to the study by the present inventor, it has been found that the fuel electrode made from the conventional nickel-zirconia cermet or the fuel electrode material of Patent Document 1 does not satisfy this requirement.

  Therefore, in view of the above problems, the present invention provides a fuel electrode-supported solid oxide fuel cell that has a high output density and is less likely to have a reduced strength even when repeatedly exposed to a reducing atmosphere / oxidizing atmosphere. And it aims at providing the manufacturing method.

The gist configuration of the present invention for achieving the above object is as follows.
(1) having a fuel electrode, a solid oxide electrolyte membrane formed on the fuel electrode, and an air electrode formed on a part of the solid oxide electrolyte membrane,
The fuel electrode includes a porous structure made of a solid oxide, and an aggregate of electrode particles having an electrode catalytic ability dispersed in voids of the porous structure,
In the plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the porous structure and the aggregate of the electrode particles are distributed in spots, and the area of the fuel electrode in the plan view is An anode-supported solid oxide fuel cell, wherein the porous structure has an area of 10 to 50%.

  (2) In a plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the average length of the porous structure is 10 to 10 on a line set to a length of at least 2 mm on the fuel electrode. The solid oxide fuel cell according to (1), which is 500 μm.

  (3) The number of the porous structures per unit length on a line set to a length of at least 2 mm on the fuel electrode in a plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane The solid oxide fuel cell according to the above (1) or (2), wherein is from 0.2 to 50 cells / mm.

(4) a step of forming a fuel electrode, a step of forming a solid oxide electrolyte membrane on the fuel electrode, and a step of forming an air electrode on a part of the solid oxide electrolyte membrane,
The step of forming the fuel electrode includes a first step of forming a porous structure made of a solid oxide, and a second step of dispersing an aggregate of electrode particles having electrocatalytic activity in the voids of the porous structure. Including a process,
In the plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the porous structure and the aggregate of the electrode particles are distributed in spots, and the area of the fuel electrode in the plan view is A method for producing a fuel electrode-supported solid oxide fuel cell, wherein the area of the porous structure is 10 to 50%.

  (5) In the first step, a porous foam is impregnated with the slurry of the solid oxide, and in the second step, the porous structure is impregnated with the slurry of the electrode particles, and then the porous structure is fired. The method for producing a solid oxide fuel cell according to the above (4), wherein the foam is burned off and then the porous structure is impregnated again with the slurry of the electrode particles.

  (6) After the second step, by applying an electrolyte material on the porous structure and firing the porous structure and the electrolyte material together, the fuel electrode and the solid oxide electrolyte membrane The method for producing a solid oxide fuel cell according to (4) or (5), wherein

  The anode-supported solid oxide fuel cell of the present invention has a high power density and is highly durable because it does not decrease in strength even when repeatedly exposed to a reducing atmosphere / oxidizing atmosphere. In addition, according to the method for producing a solid oxide fuel cell of the present invention, which is supported by a fuel electrode, it has a high power density and is resistant to a decrease in strength even when repeatedly exposed to a reducing atmosphere / oxidizing atmosphere. It is possible to obtain a fuel electrode-supported solid oxide fuel cell having a high level.

1 is a schematic cross-sectional view of a fuel electrode-supported solid oxide fuel cell 100 according to the present invention. It is a cross-sectional SEM image of the porous structure (before filling of an electrode particle) in one Example of this invention. In one Example of this invention, it is a photograph of the sample (before air electrode formation) seen from the solid oxide electrolyte membrane side. (A) is the figure which pulled straight line XY with respect to the photograph of FIG. 3, (B) is a schematic diagram of the cross section of the sample along the straight line XY of (A), (C) is ( It is a SEM photograph which shows a part of cross section of the sample along the straight line XY of A) (near the interface of a solid oxide electrolyte membrane and a fuel electrode). It is a flowchart explaining the process of the manufacturing method of a fuel electrode support type solid oxide fuel cell by one Embodiment of this invention.

  Embodiments of a fuel electrode-supported solid oxide fuel cell (SOFC) and a manufacturing method thereof according to the present invention will be described below.

  First, a SOFC manufacturing method according to an embodiment of the present invention will be described with reference to FIG. In this manufacturing method, first, in step S1, yttria-stabilized zirconia (YSZ) powder as a solid oxide and zirconia sol in which zirconia fine particles are dispersed as solid oxide are mixed to prepare a slurry.

  Next, in step S2, the porous foam is impregnated with this slurry. As a result, the porous foam is burned out, and the YSZ powder and the zirconia fine particles in the sol are integrated, while the porous structure has a large amount of voids (partly occupied by the porous foam at this stage). Is formed.

  In step S3, NiO powder as electrode particles having electrode catalytic ability and YSZ particle powder are added to zirconia sol to prepare an electrode particle slurry. In step S4, the porous structure is impregnated with electrode particle slurry. Thereby, the electrode particles are filled in the void portion where the porous foam does not exist inside the porous structure.

  In step S5, heat treatment is performed at a temperature of 1100 ° C. or lower. As a result, the porous foam is burned out. An example of this porous structure is shown in FIG. In this heat treatment, the YSZ powder and the zirconia fine particles are not sintered.

  In step S6, the electrode structure slurry is impregnated again into the porous structure, and drying or the like is performed as appropriate. As a result, the aggregate of NiO particles is dispersed in the voids newly generated by burning out the porous foam. In this embodiment, the electrode particles are NiO at the stage of the SOFC manufacturing process, but in principle at the stage of power generation by SOFC, the electrode particles are Ni. However, as described above, expansion due to an irreversible oxidation reaction in which Ni becomes NiO during the use of SOFC is a problem to be solved.

  In step S6, at least one surface of the porous structure is polished and flattened. In step S7, an electrolyte material is applied on the polished surface of the porous structure. Thereafter, in step S8, the porous structure and the electrolyte material are co-fired by a heat treatment at about 1400 ° C. Thereby, a fuel electrode and a solid oxide electrolyte membrane are formed.

  Finally, in step S9, an SOFC cell is completed by forming an air electrode on the solid oxide electrolyte membrane. At this time, in order to prevent a short circuit between the fuel electrode and the air electrode, the air electrode is formed not on the entire surface of the solid oxide electrolyte membrane but on a part of the surface. Therefore, an exposed surface is generated in the solid oxide electrolyte membrane.

  Next, an SOFC according to an embodiment of the present invention that can be obtained by this manufacturing method will be described with reference to FIGS. Referring to FIG. 1, SOFC 100 includes a fuel electrode 10, a solid oxide electrolyte membrane 20 formed on the fuel electrode 10, and an air electrode formed on a part of the solid oxide electrolyte membrane 20. 30.

  One of the characteristic configurations of this embodiment is the structure of the fuel electrode 10 described below. First, the fuel electrode 10 has a porous structure as shown in FIG. The porous structure is formed by integrating the YSZ powder and the zirconia fine particles in the sol. In particular, nano-level zirconia fine particles in the sol function as a binder that firmly bonds the YSZ powders in the course of the sol-gel reaction. For this reason, the porous structure has a very high strength. Moreover, the porous structure does not contain NiO particles, and the NiO particles are dispersed in the voids of the porous structure. Therefore, even if the electrode particles expand from Ni to NiO, they only occur in the voids of the porous structure and do not directly affect the strength of the porous structure. Based on these actions, the SOFC of this embodiment has high durability that is hard to decrease in strength even when repeatedly exposed to a reducing atmosphere / oxidizing atmosphere.

  The electrode particle slurry also contains sol-derived zirconia fine particles, and these also bind NiO particles to the surface of the voids of the porous structure in the course of the sol-gel reaction, and partly the surface of the NiO particles. Cover partially. A part of the YSZ powder in the electrode particle slurry partially covers the surface of the NiO particles, and the remaining part is dispersed in the gaps (not shown). For this reason, aggregation of the electrode particles in a reducing atmosphere can be suppressed. In addition, by limiting the oxidation area of the Ni particles during SOFC power generation, irreversible expansion of the electrode particles can be suppressed.

  The thickness of the fuel electrode 10 is not particularly limited as long as the fuel electrode can be used as a SOFC support, but is preferably 0.2 to 5 mm. This is because if the thickness is 0.2 mm or more, the fuel electrode can be reliably used as a support, and if the thickness is 5 mm or less, the fuel gas can be supplied to the electrolyte surface without excess or deficiency.

  The thicknesses of the solid oxide electrolyte membrane 20 and the air electrode 30 may be values generally used in the electrode-supported SOFC, and can be about 5 to 50 μm and about 10 to 100 μm, respectively.

  Here, this embodiment has a great feature in a plan view when the fuel electrode is viewed from the exposed surface of the solid oxide electrolyte membrane. In the present embodiment, the porous structure and the aggregate of the electrode particles are distributed in a patch shape in the plan view. This can be understood from FIG. That is, when the polished surface of the fuel electrode is observed through the solid oxide electrolyte membrane, the portion of the polished surface where the porous structure is exposed appears bright (white), and the aggregate of electrode particles is exposed. The part looks dark (black). Since the porous structure on the polished surface of the fuel electrode is made of the same material as the electrolyte membrane, the electrolyte membrane has a structure rooted in the fuel electrode, and stress is generated at the interface with the electrolyte membrane during oxidation and reduction. However, peeling and breakage of the electrolyte membrane can be suppressed. Since the contrast can be further enhanced by oxidizing the cell, this treatment is preferably performed as necessary.

  Here, in the present invention, the area of the porous structure relative to the area of the fuel electrode (hereinafter referred to as “area ratio A”) in a plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane is 10 to 10. It is important that it is 50%. When the area ratio A is less than 10%, the strength of the porous structure itself as a skeleton is not sufficient, and furthermore, the bonding strength with the electrolyte membrane cannot be ensured sufficiently. End up. On the other hand, when the area ratio A exceeds 50%, there is no problem from the viewpoint of durability, but a sufficient amount of electrode particles cannot be filled in the voids of the porous structure, and a high output density cannot be obtained. By setting the area ratio A to 10 to 50%, both high power density and durability can be achieved.

  FIG. 3 shows the entire surface of the solid oxide electrolyte membrane before forming the air electrode. In the polished surface of the fuel electrode, the exposed portion of the porous structure and the exposed portion of the aggregate of electrode particles are uniformly dispersed. Therefore, even in a plan view of FIG. The area is 10-50%.

  In the present embodiment, it is preferable that the average length of the porous structure is 10 to 500 μm on a line set to a length of at least 2 mm on the fuel electrode in the plan view. On this line, the number of porous structures per unit length (hereinafter referred to as “extension density of the porous structures”) is preferably 0.2 to 50 / mm.

  This will be described with reference to FIGS. Since FIG. 4A is a photograph before the air electrode is formed, a straight line XY having a maximum length on the circular fuel electrode is set. 4B and 4C are cross-sectional views of the sample along the straight line XY. In the SEM image of FIG. 4C, the shaded portion is a portion made of zirconia (that is, the porous structure and the electrolyte membrane in the fuel electrode). The non-shaded part in the fuel electrode is an aggregate of electrode particles. In the upper part of FIG. 4C, the length of the porous structure is shown as x1 and x2 along the straight line XY. In the present embodiment, it is preferable that the average length of the porous structure on the straight line XY including a portion not shown in FIG. 4C is 10 to 500 μm. 4C shows two porous structures on the straight line XY, the extension density of the porous structures on the straight line XY is 0.2 to 50 / mm. It is preferable.

  Since the exposed portion of the porous structure and the exposed portion of the aggregate of electrode particles are uniformly dispersed on the polished surface of the fuel electrode, the line set on the fuel electrode is not particularly limited. The length is arbitrarily set to be at least 2 mm on the exposed surface of the solid oxide electrolyte membrane (the surface on which the air electrode is not formed after the air electrode is formed).

  The reason for paying attention to the average length of the porous structure is that it is a parameter characterizing that the structure is distributed in a three-dimensional network. The reason why the extension density of the porous structure is focused is that the structure is distributed in a three-dimensional network, and is a parameter that characterizes the strength of the structure without impairing the catalyst performance. When the average length of the porous structure is 10 μm or more, the porous structure has the strength to withstand the expansion and contraction associated with the oxidation / reduction of the anode catalyst, and when it is 500 μm or less, the catalyst performance of the anode is inhibited. A void that does not occur can be secured. When the extension density of the porous structure is 0.2 to 50 / mm, the balance between the strength of the porous structure and the voids is good.

  Here, a total of three values, that is, the area ratio A, the average length of the porous structure, and the extension density, are obtained based on an image obtained by photographing the SOFC cell (air electrode non-forming portion) from the solid oxide electrolyte membrane side. be able to. As described above, in FIG. 4A, the bright portion where the porous structure is exposed and the dark portion where the aggregate of electrode particles is exposed can be clearly distinguished in the polished surface. Therefore, brightness (brightness by visible light (contrast)) is used as a parameter in the image, and an appropriate threshold value is set for this value. When the porous structure is exposed, the aggregate of electrode particles exceeds the threshold value. The exposed part should be less than the threshold value. By the image processing, a region that is equal to or greater than the threshold is classified as region A, and a region that is less than the threshold is classified as region B. The area ratio A is obtained by area of area A / (total area of area A + B). The average length of the porous structure is obtained as the average length of the region A on the set line. The extension density of the porous structure is obtained as the extension density of the region A on the set line.

  Hereinafter, each step will be described in order with reference to FIG. 5 again.

(Step S1)
The solid oxide powder may be at least one selected from the group consisting of zirconia, alumina, silica, and ceria, but is preferably zirconia or ceria, particularly preferably stabilized zirconia. . This is because the ion transport number can be stably maintained in a reducing atmosphere / oxidizing atmosphere to which the fuel electrode is exposed. Examples of the stabilized zirconia include yttria stabilized zirconia (YSZ), calcia stabilized zirconia, and magnesia stabilized zirconia. The average particle size of the solid oxide powder may be appropriately determined in consideration of the average pore size of the porous foam, for example, 0.1 to 10 μm.

  As the material of the solid oxide fine particles dispersed in the sol, at least one selected from the group consisting of zirconia including stabilized zirconia, alumina, silica, and ceria can be used. The average particle size of the solid oxide fine particles is preferably 0.1 μm or less. This is because when the thickness exceeds 0.1 μm, the effect of promoting the sintering of the oxide coarse particles is reduced. As such a sol, any commercially available product can be used. Zr-30BS manufactured by Nissan Chemical Industries, Ltd. as the zirconia sol, Alumina Sol-100 manufactured by Nissan Chemical Industries, Ltd. as the alumina sol, Nissan Chemical Industries as the silica sol. Examples of Snowtex Co., Ltd. and Ceriasol include CZ-30B manufactured by Nissan Chemical Industries, Ltd.

  To the slurry, a surfactant, a dispersant, a thickener or the like may be added to adjust the viscosity within a range that does not impair the effects of the present invention.

(Step S2)
By controlling the pore diameter and porosity of the porous foam, the area ratio A, the average length of the porous structure, and the extension density can be controlled. Although depending on the viscosity of the slurry prepared in step S1, in the case of a slurry having a viscosity of about 1000 cP, it is desirable that the pore diameter is 150 to 300 μm and the porosity is 70 to 95%. If the pore diameter is less than 150 μm, the slurry is not impregnated, and if it exceeds 300 μm, the slurry cannot be retained, and the length of the structure is shortened. If the porosity is less than 75%, the slurry is not impregnated, and if the porosity is more than 95%, the slurry cannot be retained and the length of the structure is shortened.

(Steps S3, S4, S6)
Examples of the electrode particles include NiO particles, but particles obtained by adding copper or cobalt to NiO particles may be used. The average particle diameter of the electrode particles is preferably 0.4 to 4.0 μm. When the thickness is 0.4 μm or more, the aggregation of the electrode particles can be sufficiently suppressed to enhance the durability of the fuel electrode. When the thickness is 4.0 μm or less, the active sites of the electrode particles can be sufficiently secured and high electrode performance can be obtained. Can do.

  As the sol, the same sol as in step S1 can be used. The material of the solid oxide fine particles may be the same as or different from that in step S1.

  The average particle diameter of the YSZ particle powder in the electrode particle slurry can be 0.2 to 1.0 μm. Further, in place of YSZ, at least one selected from the group consisting of zirconia, alumina, silica, and ceria may be used.

  To the slurry, a surfactant, a dispersant, a thickener or the like may be added in order to adjust the viscosity within a range that does not impair the effects of the present invention.

(Step S5)
This heat treatment is performed in the atmosphere at a temperature at which the porous foam is burned off, specifically at 300 to 1000 ° C., for 0.5 to 3 hours, although the powder and the fine particles in the sol are not sintered. . If this heat treatment is performed at a temperature equal to or higher than the sintering temperature of the solid oxide, the compact is greatly shrunk. When the electrolyte material is applied and sintered after the fuel electrode is completed, the molded body no longer contracts, whereas the electrolyte material contracts greatly. At this time, cracks may occur in the solid oxide electrolyte membrane due to a difference in shrinkage between the molded body and the electrolyte material. Therefore, in this embodiment, the solid oxide is not sintered at this stage, and the amount of shrinkage at this stage is reduced by forming the porous structure by the progress of the sol-gel reaction and the burning of the porous foam. And the said shrinkage | contraction difference in a subsequent process can be made small and generation | occurrence | production of a crack can be suppressed.

(Step S7)
Polishing is performed to flatten the surface of the porous structure, and the removal thickness may typically be about 100 to 1000 μm. Since the distribution of voids in the porous structure is uniform in the thickness direction, the area ratio A, the average length of the porous structure, and the extension density do not vary greatly depending on the polishing amount.

(Steps S8 and S9)
The electrolyte material may be a ceramic material such as YSZ, and the slurry may be applied onto the porous structure. Firing of the porous structure and the molded body electrolyte material is performed, for example, in the atmosphere at a temperature of 1300 to 1500 ° C. for 1 to 10 hours. Thereby, the ceramic component in the porous structure and the molded body electrolyte material is sintered, and the final fuel electrode and the solid oxide electrolyte membrane are completed. As a result, it is possible to reduce the shrinkage difference between the molded body and the electrolyte material and suppress the occurrence of cracks.

(Step S10)
The air electrode can be produced by a conventional method. For example, La _x Sr _1-x MnO ₃ (x = 0.8 or the like) may be used as an air electrode material, and the slurry may be applied and fired on the solid oxide electrolyte membrane after firing.

  In the present specification, the “average particle diameter” means the particle diameter at an integrated value of 50% (50% cumulative particle diameter: D50) in the particle size distribution obtained by the laser diffraction / scattering method for the powder included in the slurry. As for sol, it shall conform to the manufacturer's indication of the commercial product used. Further, in this specification, “the thickness of the fuel electrode, the solid oxide electrolyte membrane, and the air electrode” is an average of arbitrary five points when the cross section of the sample filled with the resin is polished and observed by SEM. Value.

(Example of the present invention)
The SOFC according to the present invention was prepared by the following procedure according to the present invention. First, YSZ powder (average particle size D50: 0.5 μm) is 65% by mass in zirconia sol (zirconia concentration: 30% by mass, average particle size: 63 nm, ZR-30BS manufactured by Nissan Chemical Industries, Ltd.). To prepare a slurry. The slurry was impregnated with a porous foam (Fuji Chemical Co., Ltd., Belita F (A), average pore size: 200 μm, porosity 90%), and then dried in the atmosphere at 105 ° C. for 1 hour. As a result, a porous structure (thickness: 1 mm) in which YSZ powder was bonded via sol-derived zirconia fine particles was completed. That is, at this stage, the zirconia fine particles and the YSZ powder are bonded although the bonding force is weak.

  Next, zirconia sol (zirconia concentration: 30% by mass, average particle size: 63 nm, ZR-30BS manufactured by Nissan Chemical Industries, Ltd.), NiO powder (average particle size D50: 1.0 μm) and YSZ powder (average particle size) Diameter D50: 0.5 μm) was added at a mass ratio of 2: 1 to prepare an electrode particle slurry.

  The porous foam after drying was impregnated with the electrode particle slurry. Thereby, the electrode particles are filled in the void portion where the porous foam does not exist inside the porous structure. Thereafter, heat treatment was performed in the atmosphere at 500 ° C. for 1 hour to burn off the porous foam. Note that the YSZ powder is not sintered in the heat treatment at 1100 ° C. or lower. Thereafter, the porous structure was impregnated with the electrode particle slurry again. As a result, the voids newly generated by burning the porous foam are filled with the electrode particles. Thereafter, the porous structure was dried in the atmosphere at 100 ° C. for 1 hour.

  The surface of the porous structure after drying was polished to 500 μm. An electrolyte slurry was prepared by dispersing YSZ powder (average particle diameter D50: 0.5 μm) in a solvent in which 5% by mass of ethyl cellulose was dissolved in α-terpineol so as to be 50% by mass. An electrolyte slurry was formed on the polished surface of the porous structure by a screen printing method. Thereafter, the porous structure and the electrolyte material were co-fired by heat treatment at 1400 ° C. for 3 hours in the atmosphere. Thereby, the fuel electrode and the solid oxide electrolyte membrane were completed.

An air electrode slurry was prepared by dispersing (La _0.8 Sr _0.2 ) MnO ₃ powder in a solvent in which 5% by mass of ethyl cellulose was dissolved in α-terpineol so as to be 50% by mass. An air electrode slurry was applied on the electrolyte membrane. Then, the air electrode was completed by heat treatment at 1200 ° C. for 3 hours in the atmosphere.

  The SOFC cell obtained as described above has a thickness of 600 μm (fuel electrode: 500 μm, electrolyte membrane: 20 μm, air electrode: 80 μm) and a circular shape with a diameter of 200 mm. However, in order to prevent a short circuit between the fuel electrode and the air electrode, the air electrode has a circular shape of 18 mm (the center of the circle coincides with the electrolyte membrane). That is, the exposed surface of the electrolyte membrane was a donut shape with a width of 2 mm.

  FIG. 2 shows the porous structure in the process of producing this sample, and FIG. 3 shows the sample viewed from the solid oxide electrolyte membrane side before the air electrode is formed. As is apparent from FIG. 2, the porous structure is formed by integrating the YSZ powder and the sol-derived zirconia fine particles, while having a large amount of voids inside to form a three-dimensional network structure. Further, as apparent from FIG. 3, in the fuel electrode, the portion of the porous structure and the portion of the assembly of electrode particles were distributed in a patch shape in a plan view from the electrolyte membrane side. The area (area ratio A) of the porous structure relative to the area of the fuel electrode in a plan view of the fuel electrode viewed from the exposed surface of the electrolyte membrane was determined by the method described above and found to be 30%. In addition, a curve (straight line having a diameter of 19 mm) connecting the center positions of 2 mm in width was set on the exposed surface of the electrolyte. On this curve, the extension density of the porous structure was 10 pieces / mm, and the average length thereof was 30 μm.

(Invention Example 2 / Comparative Example)
By changing the average pore diameter of the porous foam in the range of 90 to 200 μm, the area ratio A, the extension density and the average length of the porous structure on the curve were changed, An SOFC cell was produced.

(Comparative Example 2)
NiO powder (average particle size D50: 1.0 μm) 45% by mass, YSZ powder (average particle size D50: 0.5 μm) 45% by mass, and carbon (average particle size D50: 3 μm) 2 mass % Mixed powder was produced. Next, 67% by mass of the mixed powder was mixed with a solvent in which 5% by mass of polyvinyl petital was dissolved in α-terpineol to prepare a slurry. The obtained slurry was formed into a sheet by a doctor blade method. The molded body thus obtained was fired in the atmosphere at 1400 ° C. for 5 hours to produce a fuel electrode (thickness: 2.5 mm). The electrolyte membrane and the air electrode were produced in the same manner as in the present invention to obtain a SOFC cell.

<Evaluation of power generation characteristics>
Using each SOFC cell produced in the present invention example and the comparative example, the cell temperature was maintained at 800 ° C., hydrogen was introduced into the fuel electrode, and air was introduced into the air electrode, and the maximum output density was measured. The measurement results are shown in Table 1. The maximum power density of Comparative Example 2 was 0.8 W / cm ² .

<Evaluation of durability against redox cycle>
The following oxidation-reduction cycle tests were performed on each of the 20 SOFC cells produced in the inventive examples and comparative examples. That is, each SOFC is put in a container kept at 800 ° C., and the inside of the container is kept in a reducing atmosphere of 99.9% H ₂ for 30 minutes, and then the atmosphere in the container is replaced with nitrogen, and then the atmosphere is oxidized in an air atmosphere for 30 minutes. This cycle was repeated 100 times. After the cycle test, the percentage of cells in which there was no crack in the fuel electrode was determined. The results based on the following evaluation criteria are shown in Table 1. In Comparative Example 2, cracks occurred in all SOFC cells after 10 cycles.
(Evaluation criteria)
◎: 80% or more ○: 70% or more and less than 80% △: 60% or more and less than 70% ×: less than 60%

  From Table 1, when the area ratio A is 5%, the cycle durability is low, and when the area ratio A is 70%, the maximum output density is low. However, when the area ratio A is 10 to 50%, it was possible to obtain a relatively high maximum output density while maintaining cycle durability. In particular, this effect was more sufficiently obtained when the average length of the porous structure was 10 to 500 μm.

  The present invention is useful for the solid oxide fuel cell industry and various industries to which it can be applied.

DESCRIPTION OF SYMBOLS 10 Fuel electrode 20 Solid oxide electrolyte membrane 30 Air electrode 100 Solid oxide fuel cell (SOFC)

Claims (6)

A fuel electrode, a solid oxide electrolyte membrane formed on the fuel electrode, and an air electrode formed on a part of the solid oxide electrolyte membrane,
The fuel electrode includes a porous structure made of a solid oxide, and an aggregate of electrode particles having an electrode catalytic ability dispersed in voids of the porous structure,
In the plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the porous structure and the aggregate of the electrode particles are distributed in spots, and the area of the fuel electrode in the plan view is An anode-supported solid oxide fuel cell, wherein the porous structure has an area of 10 to 50%.   In a plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the average length of the porous structure is 10 to 500 μm on a line set to a length of at least 2 mm on the fuel electrode. The solid oxide fuel cell according to claim 1.   In a plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the number of the porous structures per unit length on a line set to a length of at least 2 mm on the fuel electrode is 0. The solid oxide fuel cell according to claim 1 or 2, wherein the number is 2 to 50 / mm. A step of forming a fuel electrode, a step of forming a solid oxide electrolyte membrane on the fuel electrode, and a step of forming an air electrode on a part of the solid oxide electrolyte membrane,
The step of forming the fuel electrode includes a first step of forming a porous structure made of a solid oxide, and a second step of dispersing an aggregate of electrode particles having electrocatalytic activity in the voids of the porous structure. Including a process,
In the plan view of the fuel electrode viewed from the exposed surface of the solid oxide electrolyte membrane, the porous structure and the aggregate of the electrode particles are distributed in spots, and the area of the fuel electrode in the plan view is A method for producing a fuel electrode-supported solid oxide fuel cell, wherein the area of the porous structure is 10 to 50%.   In the first step, the porous foam is impregnated with the slurry of the solid oxide, and in the second step, the porous structure is impregnated with the slurry of the electrode particles, and then the porous foam is burned off by firing. 5. The method for producing a solid oxide fuel cell according to claim 4, wherein the porous structure is impregnated with the electrode particle slurry again. After the second step, the fuel electrode and the solid oxide electrolyte membrane are formed by applying an electrolyte material on the porous structure and firing the porous structure and the electrolyte material together. A method for producing a solid oxide fuel cell according to claim 4 or 5.