JP2001185160A - Solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell capable of preventing separation of a fuel pole and reducing difference in burnt contraction between the fuel pole and a solid electrolyte. SOLUTION: The solid electrolyte fuel cell comprises an air pole mold 51 solid electrolyte molds 53, 55 and a fuel pole mold 54 stacked in this sequence and burned, the fuel pole 33 having a thickness of 5-20 μm. The solid electrolyte fuel cell is formed by, for example, stacking first solid electrolyte mold 53 on the air pole molding 51 and laminating on the first solid electrolyte mold 53 the second solid electrolyte mold 55 on which the fuel pole mold 54 is stacked, so that the first solid electrolyte mold 53 contacts the second solid electrolyte mold 55, followed by burning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to a solid oxide fuel cell in which a solid electrolyte and a fuel electrode are sequentially laminated.

[0002]

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

[0003] In general, a cylindrical type and a flat type are known as solid oxide fuel cells. Flat fuel cells are
Although it has the feature that the power density per unit volume of power generation is high, there are problems such as incomplete gas sealing and non-uniformity of temperature distribution in the cell in practical use. On the other hand,
Cylindrical fuel cells are characterized by low mechanical strength of the cells, while maintaining a uniform temperature within the cells, although the output density is low. Both types of solid oxide fuel cells are being actively researched and developed utilizing their respective characteristics.

As shown in FIG. 6, a single cell of a cylindrical fuel cell has a porous cathode support tube 2 made of a LaMnO ₃ -based material having an open porosity of about 30 to 40%, and has a Y surface on its surface. _A solid electrolyte ₃ made of ₂ O ₃ stabilized ZrO ₂ is coated, and a porous Ni-zirconia fuel electrode 4 is provided on this surface. In the fuel cell module, each single cell is connected via a LaCrO ₃ -based current collector (interconnector) 5. The power is generated by the cathode support tube 2
Air (oxygen) 6 is supplied inside, and fuel (hydrogen) 7 is supplied outside, and the temperature is set at 1000 to 1050 ° C.

As a method of manufacturing the above-described fuel cell, for example, an insulating powder made of CaO-stabilized ZrO ₂ is formed into a cylindrical shape by an extrusion method or the like, and then fired to form a cylindrical support. Then, a slurry of an air electrode, a solid electrolyte, a fuel electrode, and a current collector is applied to the outer peripheral surface of the support, and the slurry is sequentially fired and laminated, or an electrochemical vapor deposition method is applied to the surface of the cylindrical support. An air electrode, a solid electrolyte, a fuel electrode, and a current collector are sequentially formed by (EVD method), a plasma spraying method, or the like.

In recent years, a so-called co-sintering method has been proposed, in which at least two of the constituent materials are simultaneously fired in order to simplify the manufacturing process of the cell and reduce the manufacturing cost. In this co-sintering method, for example, a solid electrolyte molded body and a current collector molded body are wound in a roll shape around a cylindrical air electrode molded body and simultaneously fired, and thereafter, a fuel electrode layer is formed on the surface of the solid electrolyte layer. How to Further, for simplification of the process, a co-sintering method has been proposed in which a fuel electrode compact is further laminated on the surface of the solid electrolyte compact and fired simultaneously.

This co-sintering method is a very simple process with a small number of manufacturing steps, and is advantageous in improving the yield and cost reduction in manufacturing cells. In such a fuel cell by the co-sintering method, Y ₂ O ₃ stabilized or partially stabilized ZrO _{2 is used.}
LaMn is used as an air electrode material in order to match the coefficient of thermal expansion with the solid electrolyte.
A perovskite-type composite oxide composed of O _{3 in} which a part of La is substituted with Y and Ca is used (see Japanese Patent Application Laid-Open No. 10-162847).

[0008]

However, when a solid electrolyte molded body and a fuel electrode molded body are laminated on a cylindrical air electrode molded body, and a cylindrical fuel cell is manufactured by using a co-sintering method, the burning becomes difficult. There is a problem that the fuel electrode itself peels off after the sintering, or the power generation performance deteriorates due to a large difference in firing shrinkage between the fuel electrode and the solid electrolyte.

That is, in the conventional co-sintering method, the thickness of the fuel electrode has not been optimized. For example, when the thickness of the fuel electrode compact is large, the thermal expansion coefficient between the fuel electrode and the solid electrolyte is large. However, there has been a problem that the fuel electrode itself peels off after sintering without being able to alleviate the above problem.

[0010] When the thickness of the fuel electrode molded body is small, the solid electrolyte molded body has an end face in the cell length direction.
Even when the end faces of the fuel electrode formed body are aligned with each other in the cell length direction, after sintering, the end face of the fuel electrode moves largely inward from the end face of the solid electrolyte, that is, the fuel electrode is turned into the solid electrolyte. Observation of the interface structure shows that cracks (cracks) are progressing from the interface between the fuel electrode and the solid electrolyte toward the inside of the solid electrolyte. As a result, fuel gas leaks out, From the viewpoint of power generation performance, there has been a problem that, as the contraction difference increases, the polarization value of the fuel electrode site and the actual resistance value of the cell component increase from the initial stage.

An object of the present invention is to provide a solid oxide fuel cell which can prevent fuel electrode separation and reduce the difference in firing shrinkage between the fuel electrode and the solid electrolyte, thereby improving power generation performance. .

[0012]

Means for Solving the Problems The solid oxide fuel cell according to the present invention includes an air electrode molded product (including a calcined product) and a solid electrolyte molded product (including a calcined product). ), In a solid oxide fuel cell unit in which fuel electrode molded bodies are sequentially laminated and fired simultaneously, the fuel electrode has a thickness of 5 to 20 μm.

By adopting such a configuration, even if the air electrode molded body, the solid electrolyte molded body, and the fuel electrode molded body are sequentially laminated and fired simultaneously, the stress caused by the difference in firing shrinkage generated between the members. Therefore, the fuel electrode can be prevented from being separated from the solid electrolyte, and the difference in firing shrinkage between the fuel electrode and the solid electrolyte can be reduced.

As described above, since the difference in firing shrinkage between the fuel electrode and the solid electrolyte can be reduced, it is possible to prevent cracks generated in the solid electrolyte from the interface between the solid electrolyte and the fuel electrode. As a result, an increase in the polarization value between the fuel electrode and the solid electrolyte and an increase in the actual resistance value of the solid electrolyte component can be prevented, and accordingly, an initial high power density can be maintained for a long period of time.

Further, the first solid electrolyte molded body is laminated on the air electrode molded body (meaning that the calcined one is included),
The second solid electrolyte molded body in which the fuel electrode molded body is laminated on the first solid electrolyte molded body (meaning that the calcined one is included) is combined with the first solid electrolyte molded body and the second solid molded body. It is desirable that the electrolyte molded bodies be laminated so as to be in contact with each other and then fired.

For example, the first solid electrolyte molded body containing ZrO ₂ formed on the surface of the air electrode molded body is provided with ZrO _2.
The second solid electrolyte molded body is brought into contact with the first solid electrolyte molded body in the form of a sheet-shaped laminated molded body composed of a laminate of the second solid electrolyte molded body containing and the fuel electrode molded body containing metal particles. And then firing.

After a sheet-like laminated molded article of the second solid electrolyte molded article and the fuel electrode molded article is thus produced, this laminated molded article is applied to the first solid electrolyte molded article by the second solid electrolyte molded article. Are laminated so as to abut each other, so that when fired, the fuel electrode and the solid electrolyte can be firmly joined, and the fuel electrode can be prevented from peeling off from the solid electrolyte.

Further, it is desirable that the difference in firing shrinkage between the fuel electrode and the solid electrolyte be reduced so that the distance between the end face of the solid electrolyte and the end face of the fuel electrode is 0.15 mm or less.

The fuel electrode contains metal particles and ZrO ₂ particles, and the fuel electrode has a first fuel electrode layer on the solid electrolyte side and a second fuel electrode formed on the surface of the first fuel electrode layer. consists of a layer, the average particle diameter of the ZrO ₂ grains of the first fuel electrode layer, it is desirable to be smaller than the average particle size of the ZrO ₂ particles of the second fuel electrode layer.

This is because the fine ZrO ₂ particles of the first fuel electrode layer sufficiently support the periphery of the metal particles to suppress the growth of the metal particles of the fuel electrode, and the metal particles of the fuel electrode and the solid electrolyte Can be increased, the polarization value of the anode site can be reduced, and the ZrO ₂ particles having a large average particle size of the second anode layer can reduce firing shrinkage of the anode, The difference in firing shrinkage between the fuel electrode and the solid electrolyte can be reduced.

That is, the metal particles constituting the fuel electrode, ZrO
Regarding the average particle diameter of the _two particles, as the average particle diameter of the ZrO ₂ particles is smaller, a skeleton for suppressing the particle growth of the metal particles is more easily formed, and the effect of suppressing the particle growth of the metal particles is larger. on the other hand,
This is because the larger the average particle size of the ZrO ₂ particles, the smaller the firing shrinkage of the fuel electrode and the closer to the solid electrolyte.

[0022] In particular, the average particle diameter of the ZrO ₂ grains of the first fuel electrode layer is not more 0.8μm or less, ZrO ₂ of the second fuel electrode layer
It is desirable that the average particle size of the particles is 1 μm or more.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid oxide fuel cell according to the present invention is, for example, formed by forming an air electrode 32 on the inner surface and a fuel electrode 33 on the outer surface of a cylindrical solid electrolyte 31 as shown in FIG. 34, and a current collector 35 is
(Interconnector) is electrically connected.

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 surface of the solid electrolyte 31 near the exposed surface 37 and the notch 36 is covered with the current collector 35, Current collectors 35 are joined to the surfaces of both ends of the solid electrolyte 31 and the surface of the air electrode 32 exposed from the notch 36 of the solid electrolyte 31. A current collector 35 electrically connected to the air electrode 32 is formed on an outer surface of the cell body 34,
It is formed so as to cover the continuous same surface 39 having almost no level difference, and is not electrically connected to the fuel electrode 33. This current collector 35 is electrically connected to the fuel electrode of another cell via Ni felt when connecting the cells, thereby forming a fuel cell module. Continuous same surface 39
Is formed by polishing between both ends of the solid electrolyte until both ends of the solid electrolyte and a part of the air electrode are continuous and substantially flush with each other. The solid electrolyte 31 is, for example, 3 to
Partially stabilized or stabilized ZrO ₂ containing 15 mol% of Y ₂ O ₃ is used. Further, as the air electrode 32, for example, La is mainly composed of Ca or Sr of 10 to 20.
LaMnO ₃ with atomic% substitution is used. As the current collector 35, for example, LaCrO ₃ with Cr mainly substituted with 10 to 30 atomic% of Mg is used. The fuel electrode 33 is made of ZrO ₂ (Y ₂ O) containing 50 to 80% by weight of Ni.
₃ ) Cermet is used. The solid electrolyte 31, the air electrode 32, the current collector 35, and the fuel electrode 33 are not limited to the above examples, and may be made of known materials. In the solid oxide fuel cell of the present invention, the solid electrolyte 31 includes a first solid electrolyte 31a formed on the surface of the air electrode 32, and a second solid electrolyte 31b formed on the surface of the first solid electrolyte 31a. The fuel electrode 33 is formed on the surface of the second solid electrolyte 31b, and the thickness of the fuel electrode 33 is 5 to 20 μm.

The reason why the thickness of the anode 33 is set to 5 to 20 μm is that if the thickness of the anode 33 is smaller than 5 μm,
As the particles grow, the amount of shrinkage during firing increases.
If it is larger than 0 μm, after co-sintering, the fuel electrode 33
This is because the problem of the thermal expansion coefficient between the fuel electrode 33 and the solid electrolyte 31 cannot be alleviated, and the fuel electrode 33 itself peels off. Fuel electrode 33
The thickness of the fuel electrode 33 is desirably 10 to 20 μm from the viewpoint of reducing the contraction amount of the fuel electrode 33 and preventing the separation of the fuel electrode 33.

In the fuel electrode 33, the ZrO ₂ particles have an average particle size of 0.4 to 0.8 μm, and the Ni particles have an average particle size of 0.1 to 0.8 μm.
It is 2 to 0.6 μm. When the average particle size of the ZrO ₂ particles is smaller than 0.4 μm, the difference in firing shrinkage from the solid electrolyte tends to be significant, and when the average particle size of the Ni particles is larger than 0.6 μm. This is because there is a tendency that the number of contact points between Ni and ZrO ₂ particles cannot be increased. The average particle size of the Ni particles is 0.2
When the average particle size of the ZrO ₂ particles is smaller than 0.8 μm, it is difficult to uniformly mix the ZrO ₂ particles with the ZrO ₂ particles. This is because there is a tendency that uniform support cannot be achieved.

FIG. 2 is a perspective view of a solid oxide fuel cell according to the present invention, and FIG.
FIG. 2 is an enlarged front view showing the vicinity of a boundary 1; As shown in FIG. 3, in the solid oxide fuel cell of the present invention,
The distance x between the end face A of the fuel electrode 33 in the cell length direction and the end face B in the cell length direction of the solid electrolyte 31 formed on the lower surface thereof is set to 0.15 mm or less. If the distance x between the end face A and the end face B is larger than 0.15 mm, the firing contraction difference between the fuel electrode 33 and the solid electrolyte 31 (first solid electrolyte 31a) is large, and cracks tend to be generated in the solid electrolyte 31. Because there is. The distance x between the end face A and the end face B is
From the viewpoint of preventing crack formation in the solid electrolyte 31, the thickness is desirably 0.10 mm or less.

In the solid oxide fuel cell of the present invention, first, a cylindrical air electrode molded body is formed. This cylindrical air electrode molded product is, for example, La
Raw materials of ₂ O ₃ , Y ₂ O ₃ , CaO, MnO ₂ are weighed,
After mixing, the mixture is calcined at a temperature of about 1500 ° C. for 2 to 10 hours, and then pulverized to a particle size of 4 to 8 μm.

A binder is mixed and kneaded with the prepared powder to produce a cylindrical air electrode molded body by an extrusion molding method, which is further subjected to a binder removal treatment and calcined at 1200 to 1250 ° C. A cathode calcined body is manufactured.

As a sheet-like first solid electrolyte molded body,
Toluene, a binder, a slurry obtained by adding a commercially available dispersant to a predetermined powder, by a method such as a doctor blade, for example, using a molded thing to a thickness of 100 ~ 120μm, the cylindrical air electrode calcined body The first solid electrolyte molded body is attached to the surface and calcined.

Next, a sheet-shaped fuel electrode molded body is manufactured. First, for example, NiO / YSZ prepared at a predetermined ratio
A slurry prepared by adding toluene and a binder to the mixed powder is prepared. Similarly to the production of the first solid electrolyte molded body, the molded body is dried and formed into a sheet-shaped second solid electrolyte molded body having a thickness of, for example, 15 μm.

After printing and drying the fuel electrode layer compact on the second solid electrolyte compact, a fuel electrode layer compact 54 is formed on the first solid electrolyte calcined body 53 as shown in FIG. The formed second solid electrolyte molded body 55 is wound and laminated so that the second solid electrolyte molded body 55 comes into contact with the first solid electrolyte calcined body 53. Reference numeral 51 denotes an air electrode calcined body.

The thickness of the fuel electrode layer compact is 9 to 60 μm. When the thickness of the fuel electrode layer molded body is less than 9 μm, the difference in firing shrinkage is promoted with the growth of Ni grains,
On the other hand, when the thickness is more than 60 μm, the fuel electrode is easily peeled off due to a mismatch in the coefficient of thermal expansion between the solid electrolytes. From such a point, the thickness of the fuel electrode compact is particularly 25 to 40 μm.
Is desirable.

The Ni / YSZ mixed powder constituting the fuel electrode layer compact has an average particle diameter of the Ni powder of 0.2 to 0.6 μm,
The raw material powder having an average particle size of YSZ powder of 0.4 to 0.8 μm is used.
Wet pulverization and mixing are performed using rO ₂ balls. If the particle diameter of the YSZ powder constituting the fuel electrode is larger than 0.8 μm, there is no problem in terms of the difference in firing shrinkage, but Ni particles are locally supported because Ni particles are not sufficiently supported on a micro level.

Further, Ni powder constituting the fuel electrode and YS
Even in the combination of each particle size with Z powder, the difference in firing shrinkage can be reduced. When the YSZ powder has a particle size of 0.8 μm or more, there is no problem from the viewpoint of the difference in shrinkage during firing, but N
The growth of i-particles cannot be suppressed, and as a result, the output performance decreases with an increase in the polarization of the fuel electrode site due to a decrease in the number of reaction sites.

As a result, the number of contacts between Ni and YSZ is reduced in terms of the number of reaction sites, and as a result, the polarization value of the fuel electrode site is extremely increased, and the output performance is reduced. On the other hand, if the Ni content ratio is higher than 80%, the thermal expansion coefficient of the solid electrolyte membrane tends to be inconsistent, and the separation tends to occur.

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

Thereafter, a laminate of the cylindrical air electrode molded body 51, the solid electrolyte molded bodies 53 and 55, the fuel electrode molded body 54 and the current collector molded body is formed into four layers at a temperature of 1400 to 1550 ° C. in the atmosphere. Co-firing is performed at the same time.

In the solid electrolyte fuel cell having the above-described structure, even if the air electrode molded body, the solid electrolyte molded body, and the fuel electrode molded body are sequentially laminated and fired simultaneously, firing shrinkage generated between members does not occur. Since the reaction caused by the difference in the amount and thermal expansion can be mitigated, the separation of the fuel electrode from the solid electrolyte can be prevented, and the difference in firing shrinkage between the fuel electrode and the solid electrolyte can be reduced, whereby cracks generated inside the solid electrolyte can be reduced. As a result, an increase in the polarization value between the fuel electrode and the solid electrolyte and an increase in the actual resistance value of the solid electrolyte component can be prevented, and the initial high power density can be maintained for a long period of time.

Instead of winding and laminating the fuel electrode molded body around the surface of the solid electrolyte molded body, a sheet-shaped laminated molded body of the second solid electrolyte molded body and the fuel electrode molded body is prepared. Since the laminated molded body is laminated so that the second solid electrolyte molded body abuts on the first solid electrolyte molded body, the fuel electrode and the solid electrolyte can be firmly joined, and the fuel electrode can be prevented from being separated from the solid electrolyte. .

FIG. 5 shows another solid oxide fuel cell unit according to the present invention.
Is composed of a first fuel electrode layer 33a on the solid electrolyte side and a second fuel electrode layer 33b on the outer surface, and the average particle size of the ZrO ₂ particles of the first fuel electrode layer 33a is determined by the second fuel electrode layer 33b. Zr
It is smaller than the average particle size of the O ₂ particles. Here, the average particle size of the ZrO ₂ particles of the first fuel electrode layer 33a is set to 0.8 μm or less, and the ZrO _{2 of} the second fuel electrode layer 33b is
The average particle size of the particles is 1 μm or more, and the other configurations are the same as those in the above example.

Here, the reason why the average particle size of the ZrO ₂ particles of the first fuel electrode layer 33a is 0.8 μm or less is that the ZrO ₂ particles of the first fuel electrode layer are formed around the metal particles (Ni) by the fine ZrO ₂ particles. Is sufficiently supported, the grain growth of the metal particles of the fuel electrode 33 is suppressed, and the number of contact points between the metal particles of the fuel electrode 33 and the solid electrolyte 31 can be increased.

The reason why the average particle size of the ZrO ₂ particles in the second fuel electrode layer 33b is 1 μm or more is that the second fuel electrode layer 33b
b, ZrO ₂ particles having a large average particle diameter make the fuel electrode 33
This is because the firing shrinkage of the fuel electrode 33 and the solid electrolyte 31 can be reduced.
Although the metal particles of the fuel electrode grow at the firing temperature, the ZrO ₂ particles hardly grow.

Such a solid oxide fuel cell has the following features:
After printing and drying the first fuel electrode layer molded body on the surface of the second solid electrolyte molded body, the second fuel electrode layer molded body is printed and dried on the first fuel electrode layer molded body. It can be manufactured in the same manner as described above except that it is laminated on the surface of the first solid electrolyte calcined body.

In the above example, a cylindrical solid electrolyte fuel cell has been described, but a flat fuel cell may be used.

Further, in the above example, the air electrode molded body and the first solid electrolyte molded body were temporarily calcined, and then the second solid electrolyte molded body and the fuel electrode molded body were formed. A first solid electrolyte molded body, a second solid electrolyte molded body, and a fuel electrode molded body may be formed on the air electrode molded body.

[0047]

Example 1 In order to produce a cylindrical solid oxide fuel cell by a co-sintering method, a cylindrical air electrode molded body was first produced by the following procedure.

Commercially available La ₂ O _{3 having} a purity of 99.9% or more;
Starting from Y ₂ O ₃ , CaCO ₃ and Mn ₂ O ₃
The mixture was weighed so as to have a composition of La _0.56 Y _0.14 Ca _0.3 MnO ₃ , an organic binder was added thereto, and the mixture was extruded, and a calcined cathode was formed by debuiling and calcining.

Next, a slurry was prepared using ZrO ₂ powder containing Y ₂ O ₃ at a ratio of 8 mol% and having an average particle size of 1 to ₂ μm, and was then 100 μm thick by a doctor blade method.
Then, sheets as first and second solid electrolyte molded bodies having a thickness of 15 μm were prepared.

Next, the production of the fuel electrode compact will be described. For a Ni powder having an average particle size of 0.4 μm, Y ₂ O ₃ having an average particle size in the range of 0.4 to 0.8 μm is used.
The several kinds prepared ZrO ₂ powder containing a proportion of 8 mole%, Ni / YSZ ratio (weight fraction) of from 55/45 7
Several kinds were blended so as to be in the range of 5/25, pulverized and mixed, and slurried.

Thereafter, the prepared slurry was printed on the entire surface of the second solid electrolyte molded body to a thickness of 9 to 65 μm to prepare a fuel electrode molded body. Therefore, the end surfaces of the second solid electrolyte molded body and the fuel electrode molded body are flush with each other. Table 1 shows the content ratio of the Ni / YSZ mixed powder constituting the fuel electrode, the particle size of each powder, the sheet thickness of the fuel electrode, and the film thickness after firing.

Next, commercially available La _{2 having} a purity of 99.9% or more is used.
Starting from O ₃ , Cr ₂ O ₃ and MgO, this is
a (Mg _0.3 Cr _0.7 ) _0.97 O ₃ The mixture was weighed and mixed so as to obtain a composition, and then calcined and pulverized at 1500 ° C. for 3 hours to obtain a solid solution powder having an average particle diameter of 1 to 2 μm. A slurry was prepared using the solid solution powder, and a 100 μm-thick formed current collector was formed by a doctor blade method.

First, the first solid electrolyte calcined body was wound around the air electrode calcined body in a roll shape so that both ends thereof were opened, and calcined at 1150 ° C. for 5 hours. After calcining, the first solid electrolyte calcined body was polished flat so as to expose the air electrode calcined body, and worked so as to form the same continuous surface.

Next, the second solid electrolyte molded body having the fuel electrode molded body formed thereon is placed on the first solid electrolyte calcined body so that the first solid electrolyte molded body and the second solid electrolyte molded body are in contact with each other. After laminating and drying, the formed current collector was adhered to the same continuous surface, and then co-sintered at 1500 ° C. for 6 hours in the atmosphere to produce a co-sintered body.

In order to evaluate the fuel electrode of the produced co-sintered body, the difference in shrinkage at the interface between the second solid electrolyte and the fuel electrode after co-sintering and the presence or absence of film peeling of the fuel electrode were confirmed. The contraction difference at the interface between the second solid electrolyte and the fuel electrode is obtained by measuring the distance x between the end face B of the solid electrolyte and the end face A of the fuel electrode in the longitudinal direction of the cell. Observed visually. Table 1 shows the results.

[0056]

[Table 1]

From Table 1, it can be seen that Sample Nos. 1
The difference in shrinkage after firing was 0.28 mm, which was much larger than that of other samples, and the progress of cracks into the solid electrolyte was observed from the interface observation. Sample No. In No. 6, the whole fuel electrode was peeled off from the interface with the solid electrolyte immediately after the co-sintering was performed. On the other hand, in the sample of the present invention, no separation of the fuel electrode was observed, the difference in shrinkage after firing was 0.13 mm or less, and no cracks were observed in the interface observation, and a good interface was formed. I was

Example 2 Sample No. 1 used in Example 1 1, 2, 3, 8, and 12 solid oxide fuel cells were prepared, and the output density, actual resistance, and polarization of the fuel electrode site were measured. Table 2 shows the results.

First, in order to manufacture a cylindrical cell, a sealing member was joined to one end of the co-sintered body. The joining of the sealing member was performed in the following procedure. 8 mol% of Y ₂ O ₃
A slurry was prepared by adding water as a solvent to ZrO ₂ powder having an average particle size of 1 μm and containing one end of the co-sintered body, and one end of the co-sintered body was immersed in the slurry to have a thickness of 100 μm. It was applied to the outer peripheral surface and dried at a temperature of 120 ° C. for 1 hour. A molded body having a cap shape as a sealing member was subjected to isostatic pressing (rubber pressing) using a powder having the same composition as the slurry composition, and was cut. Thereafter, one end of the co-sintered body coated with the slurry was inserted into a molding for a sealing member, and baked at a temperature of 1300 ° C. for 1 hour in the atmosphere.

For power generation, air was flowed inside the cell and hydrogen was flown outside at 1000 ° C., and the performance was measured and evaluated based on the initial value when the output value was stabilized and the value after holding for 1000 hours.

[0061]

[Table 2]

A sample No. having an extremely large difference in firing shrinkage at the interface between the fuel electrode and the solid electrolyte was out of the scope of the present invention. 1
From the initial stage, it can be seen that the output density is lower than the other samples, and the actual resistance value and the fuel electrode polarization value are higher than those of the other samples. 1
Even after the lapse of 000 hours, the actual resistance value and fuel electrode polarization value were further increased, and it was confirmed that the propagation of cracks into the solid electrolyte and the accompanying decrease in the number of reaction sites at the interface led to deterioration. .

In any of the samples of the present invention having a difference in firing shrinkage of 0.13 mm or less, the output density of each of the samples at the initial stage was 0.1 mm.
The output density exceeded 34 W / cm ² , and even after 1000 hours, the output density was almost stable or tended to increase. Also, in the actual resistance value and the anode polarization value,
Even after the lapse of 1000 hours, no significant change was observed and a stable value was shown.

Example 3 As the first fuel electrode molded body, the weight ratio of Ni / YSZ was 7
0/30, Ni particle size 0.4 μm, YSZ particle size 0.3.
6 μm and a sheet thickness of 11 μm. A slurry having a composition as shown in Table 3 was applied to the upper surface of the first fuel electrode molded body, and dried to form a second fuel electrode molded body. A solid oxide fuel cell was produced in the same manner as in Example 1.

The difference in shrinkage at the interface between the solid electrolyte and the fuel electrode after co-sintering and the presence or absence of film peeling were confirmed. Table 3 shows the results.

[0066]

[Table 3]

From Table 3, it can be seen that in the samples Nos. 14 to 17 in which the average particle diameter of the YSZ particles of the second fuel electrode compact was larger than that of the first fuel electrode compact, only the first anode compact was formed. It can be seen that the difference in firing shrinkage is smaller than that of sample No. 2. When the average particle size of the YSZ particles of the first fuel electrode compact is 0.8 μm or less and the average particle size of the YSZ particles of the second fuel electrode compact is 1 μm or more, the difference in firing shrinkage further decreases. You can see that

[0068]

According to the solid oxide fuel cell of the present invention, even when the air electrode molded body, the solid electrolyte molded body, and the fuel electrode molded body are sequentially laminated and fired simultaneously, the difference in firing shrinkage between members and thermal expansion. Since the stress caused by the difference can be reduced, separation of the fuel electrode from the solid electrolyte can be prevented, and the difference in firing shrinkage between the fuel electrode and the solid electrolyte can be reduced.

As described above, since the difference in firing shrinkage between the fuel electrode and the solid electrolyte can be reduced, a crack (crack) generated inside the solid electrolyte from the interface between the solid electrolyte and the fuel electrode can be prevented, and the fuel electrode and the solid electrolyte can be prevented. An increase in the polarization value between the solid electrolytes and an increase in the actual resistance value of the solid electrolyte components can be prevented,
Accordingly, the initial high power density can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a cylindrical solid oxide fuel cell according to the present invention.

FIG. 2 is a perspective view showing a cylindrical solid oxide fuel cell according to the present invention.

FIG. 3 is an enlarged front view showing the vicinity of a boundary between a fuel electrode and a solid electrolyte.

FIG. 4 is an explanatory view showing a state in which a second solid electrolyte molded body on which a fuel electrode molded body is laminated is wound around a surface of a first solid electrolyte molded body and laminated.

FIG. 5 is a cross-sectional view showing a cylindrical solid oxide fuel cell of the present invention in which the fuel electrode has a two-layer structure.

FIG. 6 is a perspective view showing a conventional cylindrical solid oxide fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 ... Solid electrolyte 32 ... Air electrode 33 ... Fuel electrode 33a ... 1st fuel electrode layer 33b ... 2nd fuel electrode layer 51 ... Air electrode molded object 53 ... 1st Solid electrolyte molded body 54: Fuel electrode molded body 55: Second solid electrolyte molded body

Claims (5)

[Claims] 1. A solid electrolyte fuel cell obtained by sequentially laminating an air electrode molded body, a solid electrolyte molded body, and a fuel electrode molded body and firing them simultaneously, wherein the fuel electrode has a thickness of 5 to 20 μm. Solid electrolyte fuel cell. 2. A first solid electrolyte molded body is laminated on an air electrode molded body, and a second solid electrolyte molded body on which a fuel electrode molded body is laminated is formed on the first solid electrolyte molded body. The solid electrolyte molded body and the second solid electrolyte molded body are laminated so as to be in contact with each other, and are fired.
The solid oxide fuel cell according to any one of the preceding claims. 3. The solid oxide fuel cell according to claim 1, wherein the distance between the end face of the solid electrolyte and the end face of the fuel electrode is 0.15 mm or less. 4. The fuel electrode contains metal particles and ZrO ₂ particles, and the fuel electrode has a first fuel electrode layer on the solid electrolyte side and a second fuel electrode formed on the surface of the first fuel electrode layer. An electrode layer, wherein the average particle diameter of ZrO ₂ particles in the first fuel electrode layer is smaller than the average particle diameter of ZrO ₂ particles in the second fuel electrode layer. The solid oxide fuel cell according to any one of the above. 5. The ZrO ₂ particle of the first fuel electrode layer has an average particle size of 0.8 μm or less, and the ZrO ₂ particle of the second fuel electrode layer has an average particle size of 1 μm or more. Item 4
The solid oxide fuel cell according to any one of the preceding claims.