JP2003045446A - Cell of solid electrolyte fuel cell, method for manufacturing it, and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell of a solid electrolyte fuel cell capable of solidifying the junction boundary between a first fuel electrode and a second fuel electrode, effectively preventing the first fuel electrode from being peeled off from a solid electrolyte, and maintaining high power generating capability for a long time, and a method for manufacturing it as well as the fuel cell. SOLUTION: This cell is equipped with a first fuel electrode 33a formed by a fuel electrode 33 simultaneously baked on the surface of the solid electrolyte 31 and the second fuel electrode 33b formed by baking it on the surface of the first fuel electrode 33a. Ceramic particles 41, 43 exist in the first fuel electrode 33a and the second fuel electrode 33b, and filmy and/or fine ceramic particles 47, 48 are deposited on the surface of iron group metallic particles 45, 46 forming the first fuel electrode 33a and the second fuel electrode 33b.

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, a method for producing the same, and a fuel cell, and in particular, a solid electrolyte and a fuel electrode are sequentially laminated on the surface of an air electrode. The present invention relates to a solid oxide fuel cell in which a first fuel electrode is simultaneously sintered, a manufacturing method thereof, and a fuel cell.

[0002]

2. Description of the Related Art Conventionally, a solid oxide fuel cell has a high power generation efficiency because its operating temperature is as high as 900 to 1050 ° C., and is expected as a third generation power generation system.

Cylindrical type and flat plate type are generally known as solid oxide fuel cell units. The flat type fuel cell is
Although it has a characteristic that the power density per unit volume of power generation is high, there are problems such as imperfect gas sealing and non-uniform temperature distribution in the cell when it is put to practical use. On the other hand,
Although the cylindrical fuel cell has a low power density, it has the characteristics that the mechanical strength of the cell is high and the temperature uniformity in the cell can be maintained. Both types of solid oxide fuel cells are being actively researched and developed by taking advantage of their respective characteristics.

As shown in FIG. 5, a cylindrical fuel cell has a porous air electrode support tube 2 made of LaMnO ₃ system material having an open porosity of about 30 to 40%, and Y ₂ O ₃ is formed on the surface thereof.
A solid electrolyte 3 made of stabilized ZrO ₂ is formed, and a porous Ni-zirconia fuel electrode 4 is further formed on this surface.

In the fuel cell module, each unit cell is connected via a LaCrO ₃ -based current collector (interconnector) 5. To generate electricity, air (oxygen) 6 is flown inside the cathode support tube 2 and fuel (hydrogen) 7 is flown outside, and 1000
It is carried out at a temperature of 1050 ° C.

As a method of manufacturing the fuel cell as described above, in recent years, in order to simplify the manufacturing process of the cell and reduce the manufacturing cost, at least two of the constituent materials are simultaneously fired, that is, a so-called co-fired method. A sintering method has been proposed. This co-sintering method is, for example, a method in which a solid electrolyte molded body and a current collector molded body are wound around a cylindrical air electrode molded body in a roll shape and simultaneously fired, and then a fuel electrode is formed on the solid electrolyte surface. is there. In order to simplify the process, a co-sintering method has also been proposed in which a fuel electrode compact is further laminated on the surface of a solid electrolyte compact, and co-firing is performed.

This co-sintering method is a very simple process and has a small number of manufacturing steps, and is advantageous for improving the yield in manufacturing cells and reducing costs.

[0008]

Since the fuel electrode contains metal particles as a main component and has a coefficient of thermal expansion greatly different from that of an air electrode, a solid electrolyte, and a current collector made of other ceramics, the fuel electrode molded body is solid. When the electrolyte molded body, the current collector molded body, and the fuel electrode molded body are laminated and co-fired, peeling and cracks occur unless the thickness of the fuel electrode molded body is reduced, so the thickness is 20 μm or less. However, the electric resistance is high in such a fuel electrode with a thickness of 20 μm or less,
There has been a problem that the generated current cannot be efficiently collected, resulting in a decrease in power generation efficiency.

In order to solve such a problem, the present applicant first found that the solid electrolyte, the first fuel electrode,
A second fuel electrode is sequentially laminated, and an air electrode, a solid electrolyte,
A solid oxide fuel cell was proposed in which the first fuel electrode was co-fired and the second fuel electrode was baked on the surface of the first fuel electrode.

In the first fuel electrode, a sheet-shaped first fuel electrode compact containing a metal powder (or a metal oxide powder) and a ceramic powder is laminated on a solid electrolyte compact to form an air electrode, a solid electrolyte, Formed by co-firing with a current collector,
The surface of the first fuel electrode is coated with a paste composed of a metal powder (or a metal oxide powder), a ceramic powder, and an organic metal salt containing an element constituting the ceramic, and baked to form a second fuel electrode. Was there.

In such a solid oxide fuel cell, finer sub-particles are formed on the surface of the ZrO ₂ particles inside the first fuel electrode, which are firmly bonded to the ZrO ₂ film constituting the solid electrolyte by high temperature sintering. micron level ZrO ₂ fine particles are deposited deposited was sintered (baked), ZrO ₂ fine particles present in the lower portion of the second fuel electrode ZrO first fuel electrode ₂
It can be bonded and integrated with particles to form a strong interface.

However, there is a problem that the bonding strength between the first fuel electrode formed by co-firing and the solid electrolyte is still low. As a result, when power is continuously generated for a long period of time, there is a problem in that the first fuel electrode is likely to be separated from the solid electrolyte. In particular, in recent years, a small-diameter cylindrical cell having a diameter of 10 mm or less has been used. However, since such a small-diameter cell has a large curvature, the first and second
There is a problem that excessive stress is likely to be generated in the fuel electrode, and the first and second fuel electrodes are likely to peel off due to long-term power generation.

According to the present invention, the joint interface between the first fuel electrode and the second fuel electrode can be strengthened, and the first fuel electrode can be effectively prevented from peeling off from the solid electrolyte, so that high power generation capability can be maintained for a long period of time. An object of the present invention is to provide a solid oxide fuel cell, a method for producing the same, and a fuel cell.

[0014]

A solid oxide fuel cell according to the present invention is a solid oxide fuel cell in which a fuel electrode is formed on one surface of a solid electrolyte and an air electrode is formed on the other surface of the solid electrolyte. The fuel electrode includes a first fuel electrode formed by simultaneous firing on the surface of the solid electrolyte, and a second fuel electrode formed by baking on the surface of the first fuel electrode. Ceramic particles are present in the second fuel electrode, and a film and / or fine particles are formed on the surface of the iron group metal particles or iron group metal oxide particles forming the first fuel electrode and the second fuel electrode. It is characterized in that fine ceramic particles in the form of particles are deposited.

In such a solid oxide fuel cell, the fine ceramic particles of the first fuel electrode are mainly present on the solid electrolyte side, and the fine ceramic particles of the second fuel electrode are mainly present on the first fuel electrode side. However, for example, the film-shaped and / or fine-particle-shaped ZrO ₂ particles (fine ceramic particles) existing on the surface of the iron group metal particles or the iron group metal oxide particles forming the second fuel electrode are the first fuel electrode. The ZrO ₂ particles (ceramic particles) inside can be bonded and integrated with the surface to form a strong interface, and the bonding strength of the second fuel electrode to the first fuel electrode can be improved, and for example, the first fuel electrode can be formed. The film-like and / or fine-particle ZrO ₂ particles (fine ceramic particles) present on the surface of the iron-group metal particles or iron-group metal oxide particles are bonded and integrated to the surface of the ZrO ₂ particles inside the solid electrolyte, and thus solidified. World The possible formation, the bonding strength of the solid electrolyte of the first fuel electrode can be improved, can maintain a high power generation capacity long time.

In the present invention, the average particle size of the iron group metal particles or iron group metal oxide particles forming the second fuel electrode is the iron group metal particles or iron group metal oxide forming the first fuel electrode. It is desirable that the particle size is larger than the average particle size. According to this structure, since the iron group metal particles or iron group metal oxide particles forming the first fuel electrode are fine particles, a reaction field for forming the triple point can be sufficiently secured, while the second fuel electrode is formed. Since the iron group metal particles or iron group metal oxide particles are coarse particles, a porous structure can be secured, and in addition to the current collecting function, the reduction necessary for the electrode reaction and the gas permeability of the generated steam gas are sufficiently secured. be able to.

Furthermore, it is desirable that the solid oxide fuel cell of the present invention has a cylindrical shape with an outer diameter of 10 mm or less. In such a small-diameter cell, since the curvature is large,
Excessive stress is likely to be generated in the first fuel electrode and the second fuel electrode, the manufacturing yield at the time of manufacturing may be reduced, and the first fuel electrode and the second fuel electrode may be easily separated due to long-term power generation. Therefore, the use of the solid oxide fuel cell of the present invention has great significance.

Further, the method for producing a solid oxide fuel cell of the present invention comprises a solid electrolyte molded body (including a calcined body) having a first fuel electrode molded body on one surface and an air electrode molded body (calculated body) on the other surface. A solid electrolyte fuel cell, the method comprising the steps of: firing a laminated body on which a fuel cell is formed); and a step of forming and baking a second fuel electrode compact on the surface of the first fuel electrode. In the method, the first fuel electrode compact and the second fuel electrode compact contain an iron group metal powder or iron group metal oxide powder, a ceramic powder, and an organic metal salt.

For example, by using an organic metal salt of Zr and Y, this organic metal salt precipitates on the solid electrolyte side at the stage of forming the first fuel electrode compact, and the iron group metal particles or the iron group metal are present here. YSZ (fine ceramic particles) in the form of film and / or fine particles is deposited on the surface of the oxide particles,
Z is integrated with YSZ of the solid electrolyte. Similarly, the organometallic salt precipitates on the first fuel electrode side at the stage of forming the second fuel electrode compact, and here, on the surface of the iron group metal particles or iron group metal oxide particles, a film-like and / or fine particles are formed. YSZs (fine ceramic particles) are deposited, and the YSZs are combined and integrated with the YSZs (ceramic particles) of the first fuel electrode to obtain the solid oxide fuel cell of the present invention.

The fuel cell of the present invention comprises a plurality of the above-described solid oxide fuel cell units housed in a reaction vessel.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, a solid oxide fuel cell of the present invention comprises a cell body 3 having a solid electrolyte 31 having a cylindrical air electrode 32 on the inner surface and a fuel electrode 33 on the outer surface.
4 is formed, and a collector (interconnector) 35 is electrically connected to the air electrode 32.

That is, the notch 36 is formed in a part of the solid electrolyte 31.
Is formed, a part of the air electrode 32 formed on the inner surface of the solid electrolyte 31 is exposed, and the exposed surface 37 and the surface of the solid electrolyte 31 near the notch 36 are covered with the current collector 35. The current collector 35 is joined to the surfaces of both end portions of the solid electrolyte 31 and the surface of the air electrode 32 exposed from the notches 36 of the solid electrolyte 31.

A current collector 35 electrically connected to the air electrode 32.
Is formed on the outer surface of the cell body 34, and both end surfaces and the exposed surface 37 of the solid electrolyte 31 formed in a continuous arc surface shape.
And is not electrically connected to the fuel electrode 33.

In the solid oxide fuel cell of the present invention, as shown in FIG. 2, the fuel electrode 33 is the first fuel formed by co-firing with the solid electrolyte 31, the air electrode 32, and the current collector 35. It is composed of a pole 33a and a second fuel pole 33b formed by baking on the surface of the first fuel pole 33a. These first fuel electrode 33a and second fuel electrode 33
As shown in FIG. 3, ceramic particles 41, 4 and
3 and the iron-group metal particles 45 and 46 have film-shaped and / or fine-particle-shaped fine ceramic particles 47 and 48 deposited thereon.

The film-shaped and / or fine-particle-shaped fine ceramic particles 47 and 48 are ZrO ₂ (YSZ) containing Y ₂ O ₃ in view of bonding with the ZrO ₂ type material forming the solid electrolyte 31. Is desirable. In addition, the solid electrolyte 3
The ceramic particles 41 and 43 added from the standpoint of improving the bonding strength with 1 are ZrO ₂ (YSZ) containing Y ₂ O _3.
Is desirable. As the iron group metal particles 45 and 46, Fe,
There are Co, Ni, etc., but Ni is preferable.

Instead of the iron group metal particles 45 and 46, iron group metal oxide particles may be used. In this case, the second
The reduction process after baking the fuel electrode 33b, or exposure to the reducing atmosphere during power generation, turns into metal particles.

The average particle size of the iron group metal particles 46 of the second fuel electrode 33b is made larger than the average particle size of the iron group metal particles 45 of the first fuel electrode 33a. As a result, the first fuel electrode 3
In 3a, the number of reaction sites of the metal particles 45 can be sufficiently formed from the viewpoint of the number of reaction sites of the metal particles 45. On the other hand, since the average particle size of the metal particles 46 of the second fuel electrode 33b is larger than that of the first fuel electrode 33a, the current collecting ability can be improved, and not only the gas deposited in the reaction but also the gas generated by the reaction can permeate. It is possible to maintain good sex.

Fine ceramic particles 4 of the first fuel electrode 33a
7 is mainly present on the surface side of the solid electrolyte 31, and the fine ceramic particles 48 of the second fuel electrode 33b are mainly the first ceramic particles.
It exists on the surface side of the fuel electrode 33a.

The fine ceramic particles 47 existing on the surface of the iron group metal particles 45 of the first fuel electrode 33a are solid electrolyte 3
The fine ceramic particles 48 bonded to the surface of the YSZ particles 49 constituting No. 1 and existing on the surface of the iron group metal particles 46 of the second fuel electrode 33b are bonded to the ceramic particles 41 in the first fuel electrode 33a. In the present invention, the ceramic particles 4
1 and 43 have a particle size of 1 μm or more, and the fine ceramic particles 47 and 48 have a particle size of 0.5 μm.

The solid oxide fuel cell of the present invention has a cylindrical shape with an outer diameter of 10 mm or less. Since such a small-diameter cell has a large curvature, internal stress is likely to occur during molding and firing, and the first fuel electrode 33a and the second fuel electrode 33
Since b tends to be easily peeled off, the use of the present invention is significant. It is most effective when the outer diameter is 5 mm or less.
The outer diameter of the cell in the present invention is the maximum outer diameter of the cell.

The solid electrolyte 31 contains, for example, 3 to 15 mol%.
Partially stabilized or stabilized ZrO ₂ containing Y ₂ O ₃ is used. Further, as the air electrode 32, for example, La
LaMnO _{3 in} which 10 to 30 atomic% of Ca or Sr is substituted with 5 to 20 atomic% of Y is used, and as the current collector 35, for example, L in which Cr is substituted with 10 to 30 atomic% of L is used.
aCrO ₃ is used.

As the first fuel electrode 33a and the second fuel electrode 33b, ZrO ₂ (Y ₂ O ₃ containing 50 to 80% by weight of Ni is used.
Included) cermet is preferably used.

Solid electrolyte 31, air electrode 32, current collector 3
5, the first fuel electrode 33a and the second fuel electrode 33b,
The material is not limited to the above example, and a known material may be used.

In the method of manufacturing the solid oxide fuel cell having the above structure, first, a cylindrical air electrode molded body is formed. This cylindrical air electrode formed body has, for example, La ₂ O ₃ , Y ₂ O ₃ , CaCO ₃ and Mn ₂ O ₃ according to a predetermined composition.
Weigh and mix the raw materials.

After that, for example, calcination is performed at a temperature of about 1500 ° C. for 2 to 10 hours, and then pulverized to a particle size of 4 to 8 μm. The prepared powder is mixed with a binder and kneaded to prepare a cylindrical air electrode formed body by an extrusion molding method, and further subjected to binder removal treatment and calcination at 1200 to 1250 ° C. to form a cylindrical air electrode temporary body. Create a fired body.

Next, the production of a paste for attaching the solid electrolyte compact will be described. The paste having a function as a Mn diffusion preventing layer includes a ZrO ₂ powder containing at least one of Y ₂ O ₃ and CaO and a YDC powder (Y ₂ O ₃
CeO ₂ ) doped with 30 wt% of O ₃ is mixed and calcined,
After that, toluene is added as a solvent to the above-mentioned mixed powder whose particle size has been adjusted, to prepare. This paste was applied to the surface of a cylindrical air electrode calcined body to form a coating film of the Mn diffusion preventing layer.

As the sheet-shaped first solid electrolyte molded body,
A slurry obtained by adding toluene, a binder, and a commercially available dispersant to ZrO ₂ powder containing Y ₂ O ₃ is prepared by a method such as a doctor blade, for example, 100 to 120 μm.
Using a molded product having a thickness of m, on the surface of the coating film of the Mn diffusion preventing layer formed on the surface of the cylindrical air electrode calcined body,
The first solid electrolyte molded body is attached and calcined to form a first solid electrolyte calcined body on the surface of the air electrode calcined body. The first
Although the solid electrolyte molded body was calcined, it does not have to be calcined.

Next, a sheet-shaped first fuel electrode compact is prepared. First, for example, Ni powder prepared in a predetermined ratio, Y
_To ZrO ₂ (YSZ) powder containing ₂ O ₃ , toluene,
An organometallic salt solution containing Zr and Y is added to prepare a slurry.

In the same manner as in the production of the first solid electrolyte molded body,
For example, a sheet-shaped second solid electrolyte molded body having a thickness of 15 μm is molded and dried. After printing and drying the slurry on the second solid electrolyte compact, the second solid electrolyte compact having the first fuel electrode compact formed on the first solid electrolyte calcined compact is treated with the first solid electrolyte. The second solid electrolyte molded body is wound around the calcined body so as to come into contact with the calcined body and laminated. By applying the slurry to the first fuel electrode, the organic metal salt settles toward the second solid electrolyte compact.

Next, as in the preparation of the solid electrolyte molded body, 10
A current collector molded body having a thickness of 0 to 120 μm is attached to a predetermined place.

Thereafter, the cylindrical air electrode calcined body, the coating film of the Mn diffusion preventing layer, the first solid electrolyte calcined body, the second solid electrolyte compact, the first fuel electrode compact and the collector compact were formed. The laminated body is, for example, at a temperature of 1400 to 1550 ° C. in the atmosphere and 4
The layers are co-fired at the same time.

Next, a second fuel electrode paste is prepared. Ni powder prepared in a predetermined ratio, ZrO ₂ containing Y ₂ O ₃
(YSZ) powder, organometallic salts of Zr and Y, and toluene are added to prepare a slurry.

The second fuel electrode is the air electrode, the solid electrolyte, the first
After co-sintering the fuel electrode and the current collector, the slurry of the second fuel electrode is applied and printed on the surface of the first fuel electrode and dried to form the second electrode.
A fuel electrode molded body was prepared and subjected to 1400 in the atmosphere.
It is carried out by heat treatment (baking) at a temperature of not more than ℃. Second
The organometallic salt settles to the first fuel electrode side by the slurry application printing of the fuel electrode.

The second fuel electrode produced in this manner has an excellent film surface condition and a good bonding condition at the interface with the underlying first fuel electrode. In addition to the current collection function, the YSZ forming the second fuel electrode is mixed and the mixing ratio is controlled so as to achieve structural stability between the members. It is possible to prevent an increase in polarization and actual resistance, collect the high initial power density obtained in a single cell, and maintain it for a long time.

In the above example, a cylindrical solid oxide fuel cell is described, but a flat plate fuel cell may be used.

Further, in the above example, the air electrode calcined body, the first
Although the example of forming the solid electrolyte calcined body has been described, these may be the air electrode molded body or the first solid electrolyte molded body.

In the fuel cell of the present invention, for example, as shown in FIG. 4, an oxygen-containing gas chamber partition plate 5 is provided in a reaction vessel 51.
3, the combustion chamber partition plate 55 and the fuel gas chamber partition plate 57 are used to form the oxygen-containing gas chamber A, the combustion chamber B, the reaction chamber C, and the fuel gas chamber D.
Are formed. The plurality of bottomed cylindrical solid oxide fuel cell units 59 are housed in the reaction vessel 51, and these solid oxide fuel cell units 59 are formed on the combustion chamber partition plate 55. The opening 61 is inserted and fixed in the insertion hole 60, and the opening 61 projects from the combustion chamber partition plate 55 into the combustion chamber B, and the oxygen-containing gas introduction pipe fixed to the oxygen-containing gas chamber partition plate 53 is provided therein. One end of 63 is inserted. In the combustion chamber partition plate 55, in order to discharge excess unreacted fuel gas from the reaction chamber C to the combustion chamber B,
A plurality of exhaust holes 64 are formed, and the fuel gas chamber partition plate 57 is provided with a supply hole for supplying the fuel gas chamber D into the reaction chamber C.

Further, in the reaction vessel 51, a fuel gas inlet port 65 for introducing a fuel gas composed of hydrogen, for example,
An oxygen-containing gas introduction port 67 for introducing air and an exhaust port 69 for discharging the gas burned in the combustion chamber B are formed.

In such a solid oxide fuel cell, the oxygen containing gas from the oxygen containing gas chamber A, for example, air is supplied into the solid oxide fuel cell 59 through the oxygen containing gas introducing pipe 63, respectively. Further, the fuel gas from the fuel gas chamber D is supplied between the plurality of solid oxide fuel cell units 59 to react in the reaction chamber C to generate electric power, and surplus air and unreacted fuel gas are burned in the combustion chamber B. Then, the burned gas is discharged to the outside through the exhaust port 69.

The fuel cell of the present invention is not limited to the fuel cell of FIG. 4 described above, and it is sufficient that a plurality of the above-mentioned fuel cells are accommodated in the reaction container.

[0051]

Example In order to manufacture a cylindrical solid oxide fuel cell unit by the co-sintering method, first, a cylindrical air electrode calcined body was manufactured by the following procedure. La with a purity of 99.9% or more on the market
₂ O ₃ , Y ₂ O ₃ , CaCO ₃ , and Mn ₂ O ₃ were used as starting materials and calcined at 1500 ° C. (La _0.56 Y _0.14 Ca _0.3 ).
_0.97 MnO ₃ was prepared, and then pulverized to a particle size of 4 μm. Using this, cylindrical support tubes with different outer diameters were extruded and then de-heated and calcined at 1250 ° C. A calcined body was prepared.

Next, a slurry was prepared by using ZrO ₂ powder containing Y ₂ O _{3 in an amount} of 8 mol% and having an average particle size of 1 to ₂ μm, and a slurry having a thickness of 100 μm and a thickness of 15 μm was prepared by a doctor blade method. A sheet as a first and second solid electrolyte molded body was produced.

Next, the production of the first fuel electrode compact will be described. The Ni powder having an average particle diameter of 0.5 to 1.5 μm contained Y ₂ O _{3 in an amount} of 8 mol% and had an average particle diameter of 0.1.
6 μm ZrO ₂ (YSZ) powder and Zr and Y organometallic salts were prepared, and the YSZ powder and Zr and Y were adjusted so that the Ni / YSZ ratio (weight fraction) was 65/35.
Each of the organometallic salts of was prepared and a slurry was prepared.

Thereafter, the prepared slurry is printed on the entire surface of the second solid electrolyte compact so as to have a thickness of 30 μm, and then dried, and the first fuel electrode compact is placed on the second solid electrolyte compact. Formed.

On the other hand, the slurry for the second fuel electrode compact is
Y ₂ O ₃ is added to Ni powder having an average particle diameter of 5 to 10 μm
ZrO having an average particle size of 0.6 μm contained at a ratio of mol%
₂ (YSZ) powder and respective organometallic salts of Zr and Y were prepared, and the Ni / YSZ ratio (weight fraction) was 72/2.
8 was mixed and mixed to prepare a slurry.

Next, commercially available La _{2 having} a purity of 99.9% or more is used.
O ₃ , Cr ₂ O ₃ , and MgO are used as starting materials, and La
(Mg _0.3 Cr _0.7 ) _0.97 O ₃ Weighed and mixed to obtain a composition, calcinated and pulverized at 1500 ° C. for 3 hours, and a slurry is prepared using this solid solution powder. A molded body was produced.

As the paste for the Mn diffusion preventing layer, 8% Y ₂ O ₃ was used.
ZrO ₂ powder (8YSZ) containing mol% and YD represented by the composition formula (CeO ₂ ) 0.7 (Y ₂ O ₃ ) 0.3
C powder was mixed so that 8YSZ: YDC = 1: 9 (weight fraction), and toluene was added to this mixed powder as a solvent to prepare.

First, the Mn diffusion preventive layer paste is applied to the air electrode calcined body, and the first solid electrolyte molded body is wound around the coated film in a roll shape so that both ends thereof are open 1150. It was calcined under the condition of 5 ° C for 5 hours. After the calcination, the first solid electrolyte calcined body was ground in a circular arc shape so as to expose the air electrode calcined body between both ends.

Then, the second solid electrolyte calcined body surface is subjected to a second
The second solid electrolyte molded body on which the fuel electrode molded body is formed is laminated so that the first solid electrolyte calcined body and the second solid electrolyte molded body are in contact with each other, and after drying, current collector molding is performed on the polished surface. The body was attached, and thereafter, firing was performed in the atmosphere at 1550 ° C. for 3 hours to prepare 50 co-sintered bodies.

A second electrode was formed on the surface of the first fuel electrode of this co-sintered body.
The fuel electrode was printed using a mesh plate, and then heat-treated and baked under the conditions of 1400 ° C. for 1 hour in the air atmosphere to prepare a cell having a maximum outer diameter of 4 to 15 mm.

N in the first and second fuel electrodes of the produced cell
The average particle size of the iO particles was determined. For the evaluation of the manufactured second fuel electrode, the number of non-defective products in 50 cells was calculated using a scanning electron microscope (SEM) based on the presence or absence of peeling of the end portion, and the production yield is shown in Table 1.

Also, using 10 well-produced cells, air was flown inside the cell and hydrogen was flown outside at 1000 ° C., the initial value when the output value became stable, and after 100 hours of holding, The performance was measured and evaluated, and after 100 hours, the number of cells decreased to 2/3 or less of the initial value was calculated, and the number of non-defective products was described. The output density in the table is the average value of 10 cells. The results of these measurements are shown in Table 1. When the first and second fuel electrodes produced by using the organic metal salt were observed with a scanning electron microscope (SEM), fine-grained fine ceramic particles were present on the surface of the NiO particles. These fine ceramic particles were mainly present in the lower layers of the first and second fuel electrodes. On the other hand, fine ceramic particles were not present on the surface of NiO particles in the first and second fuel electrodes produced without using the organometallic salt.

[0063]

[Table 1]

From Table 1, the sample of the present invention has an outer diameter of 10
Even when the diameter becomes smaller than mm and the curvature becomes large, by adding the organic metal salt to each of the first and second fuel electrodes, the interface between the first fuel electrode and the second fuel electrode is firmly bonded and , The bonding strength between the first fuel electrode and the solid electrolyte can be improved, the yield at the time of manufacturing cells can be improved, and the initial value of the power density is high.
Even after the lapse of 00 hours, the output density hardly decreased, and there was no cell in which the output density decreased to ⅔ or less of the initial value, and it can be seen that the high output density can be maintained for a long period of time.

On the other hand, sample No. 1 containing no organometallic salt in the slurry of the first fuel electrode was used. In Nos. 1, 5, and 9, the production yield was good, but the output density was low in the initial stage, and after 100 hours, the output density decreased to 2/3 or less in many cells. In particular, it can be seen that the smaller the cell outer diameter, the more defects. When the cell with the reduced power density was observed by SEM,
A part of the fuel electrode was peeled off from the solid electrolyte.

Further, sample No. 1 containing no organometallic salt in the slurry of the second fuel electrode was used. In No. 10, the production yield was poor, and the rate of decrease in output density after 100 hours was large.

[0067]

As described in detail above, in the solid oxide fuel cell of the present invention, the film existing on the surface of the iron group metal particles or iron group metal oxide particles forming the second fuel electrode. -Shaped and / or fine-grained fine ceramic particles can be bonded and integrated with the surface of the ceramic particles inside the first fuel electrode to form a strong interface, and the bonding strength of the second fuel electrode to the first fuel electrode can be improved. Is present on the surface of the iron group metal particles or iron group metal oxide particles forming the first fuel electrode.
Membrane-shaped and / or fine-grained fine ceramic particles can be bonded and integrated with the surface of the ZrO ₂ particles inside the solid electrolyte to form a strong interface, and the bonding strength of the first fuel electrode to the solid electrolyte can be improved. It is possible to obtain a solid oxide fuel cell having a high power generation capacity for a period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cylindrical solid oxide fuel cell unit of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the fuel electrode of FIG. 1 and its vicinity.

FIG. 3 is an explanatory view showing a part of the fuel electrode of FIG. 1 in an enlarged manner.

FIG. 4 is an explanatory diagram showing a fuel cell of the present invention.

FIG. 5 is a perspective view showing a conventional cylindrical solid oxide fuel cell unit.

[Explanation of symbols]

31 ... Solid electrolyte 32 ... Air electrode 33 ... Fuel pole 33a. ． ． First fuel pole 33b. ． ． Second fuel pole 35 ... Current collector 41 ... Ceramic particles of the first fuel electrode 43. ． ． Second fuel electrode ceramic particles 45 ... Iron group metal particles of the first fuel electrode 46 ... Iron group metal particles of the second fuel electrode 47 ... Fine ceramic particles for the first fuel electrode 48. ． ． Fine grain ceramic particles of the second fuel electrode

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Claims (7)

[Claims] 1. A solid electrolyte fuel cell in which a fuel electrode is formed on one surface of a solid electrolyte and an air electrode is formed on the other surface, wherein the fuel electrode is formed by cofiring the surface of the solid electrolyte. A first fuel electrode and a second fuel electrode formed by baking on the surface of the first fuel electrode, wherein ceramic particles are present in the first fuel electrode and the second fuel electrode, and A solid characterized in that film-shaped and / or fine-particle-shaped fine ceramic particles are deposited on the surface of iron group metal particles or iron group metal oxide particles constituting the first fuel electrode and the second fuel electrode. Electrolyte fuel cell. 2. The average particle size of the iron group metal particles or iron group metal oxide particles constituting the second fuel electrode is more than the average particle size of the iron group metal particles or iron group metal oxide particles in the first fuel electrode. The solid electrolyte fuel cell according to claim 1, wherein the solid electrolyte fuel cell is also large. 3. The fine ceramic particles of the first fuel electrode are mainly present on the solid electrolyte side, and the fine ceramic particles of the second fuel electrode are mainly present on the first fuel electrode side. The solid oxide fuel cell according to 1 or 2. 4. The fine ceramic particles of the first fuel electrode are bonded to the surface of the solid electrolyte, and the fine ceramic particles of the second fuel electrode are bonded to the ceramic particles in the first fuel electrode. The solid oxide fuel cell according to any one of claims 1 to 3. 5. The solid oxide fuel cell according to any one of claims 1 to 4, which has a cylindrical shape with an outer diameter of 10 mm or less. 6. A step of firing a laminated body in which a first fuel electrode molded body is formed on one surface of a solid electrolyte molded body and an air electrode molded body is formed on the other surface, and a second fuel electrode is formed on the surface of the first fuel electrode. A method for manufacturing a solid oxide fuel cell, comprising the steps of forming a molded body and baking the molded body, wherein the first fuel electrode molded body and the second fuel electrode molded body are iron group metal powder or iron group metal oxide. And a ceramic powder, and an organic metal salt are contained in the solid electrolyte fuel cell. 7. A fuel cell, characterized in that a plurality of solid oxide fuel cell units according to any one of claims 1 to 5 are housed in a reaction vessel.