JPH07296838A - Manufacture of fuel cell - Google Patents

Abstract

PURPOSE:To reduce the number of manufacturing processes of a fuel cell for enhanced productivity and to enhance the reliability of the fuel cell by interposing an intermediate layer between two layers which have different coefficients of contractions when baked simultaneously. CONSTITUTION:A cylindrical fuel cell comprises a stack consisting of a porous air electrode layer 2, a solid electrolyte layer 3, a porous fuel layer 4, and a collector layer 5 stacked on the surface of a cylindrical base 1 made of porous ceramic. A process for baking at least two adjacent layers in the stack simultaneously is carried out. In this case, it is most desirable that at least either one of the electrolyte layer 3 and the collector 5, both of which are solid, and at least either one of the cylindrical base 1, the air electrode layer 2, and the fuel electrode layer 4, be selected and combined for simultaneous baking. In this case, an intermediate layer is interposed between the two layers. It is important that the intermediate layer be made from a material whose coefficient of contraction has a value halfway between those of the air electrode and the solid electrolyte during baking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing a fuel cell having a laminate having an air electrode layer, an electrolyte layer, a fuel electrode layer and the like.

[0002]

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

Generally, there are two types of fuel cells, a cylindrical type and a flat type.
The type is known. The flat plate type fuel cell has a feature that the power density per unit volume of power generation is high, but when it is put into practical use, there are problems such as incomplete gas seal and uneven temperature distribution in the cell.

On the other hand, the cylindrical fuel cell has the characteristics that the mechanical density of the cell is high although the power density is low, and the temperature uniformity in the cell can be maintained. Both types of solid electrolyte fuel cells are being actively researched and developed by taking advantage of their respective characteristics.

As shown in FIG. 1, a unit cell of a cylindrical fuel cell is constructed by laminating a LaMnO ₃ -based material on the outer circumference of a cylindrical substrate 1 made of an insulating porous ceramic made of CaO-stabilized ZrO _2. A polar layer 2 is formed, and a stabilized ZrO ₂ solid electrolyte layer 3 containing, for example, Y ₂ O ₃ is formed on the surface of the electrode layer 2, and a porous Ni-zirconia (Y ₂ O ₃
The fuel electrode layer 4 composed of (containing) etc. is formed in a substantially concentric shape. Further, a current collector layer (interconnector) 5 made of a LaCrO ₃ system material or the like for connecting the cells is connected to the air electrode layer 2, penetrates the solid electrolyte layer 3, and is not in contact with the fuel electrode 4. It is exposed on the surface of the cell. In the fuel cell module, a plurality of single cells having the above-mentioned configuration are connected via a current collector layer 5.

On the other hand, in the flat plate type fuel battery cell, as shown in FIG. 2, a porous air electrode layer 7 is provided on one side of the solid electrolyte layer 6.
On the other hand, a porous fuel electrode layer 8 is provided. For connection between the single cells, a current collector layer (separator) 9 made of a LaCrO ₃ -based material in which MgO or CaO having a high density is dissolved
Is used.

When power generation is carried out using these fuel cells, air (oxygen) is flown to the air electrode layer side and fuel (hydrogen) is flown to the fuel electrode layer side to heat it to a temperature of 900 to 1050 ° C. Done by.

As a general method for manufacturing such a fuel cell, for example, in the case of a cylindrical type, insulating powder is molded into a cylindrical shape by a method such as extrusion molding, and then the insulating powder is fired to form a porous ceramic. A method of producing a cylindrical base body, and repeating the slurry coating on the inner peripheral surface or the outer peripheral surface of the base body to form an air electrode layer, a solid electrolyte layer or a fuel electrode layer and firing the same, or on the surface of the cylindrical substrate. A method of sequentially forming an air electrode layer, a solid electrolyte layer, and a fuel electrode layer by an electrochemical vapor deposition method (EVD method), a plasma spraying method, or the like is known.

Further, in the case of the flat plate type, generally, an air electrode layer is printed on one surface of an electrolyte plate produced by sintering a green sheet of an electrolyte produced by a doctor blade method or extrusion molding. And then heat-treat and bake, then form the fuel electrode layer on the other surface by the same method and bake to make a single cell, or bake the air electrode layer and the fuel electrode layer at the same time to make a single cell. To do. In addition, the current collecting member is manufactured by sintering separately from the single cell, and is inserted between the above single cells and fired.

Recently, in order to simplify the manufacturing process,
It is also possible to simultaneously fire two or more layers constituting the fuel cell, as disclosed in JP-A-4-315769 and JP-A-4-3220.
No. 61, JP-A-5-67473 and the like.

[0011]

However, according to the above-mentioned conventional general manufacturing method, since the number of layers to be formed is large and the process itself is complicated, it takes a lot of time to manufacture, and There is a problem that various kinds of manufacturing equipment are required, the manufacturing cost is high, and mass production is difficult.

When two or more layers are fired at the same time, the two layers are firmly adhered by using an adhesive or the like before firing, but the heat shrinkage behavior and the coefficient of thermal expansion during firing are matched. However, it is difficult to control these, peeling occurs in the firing process, cracks, etc., adhesion between layers is insufficient even when it is not observed from the appearance, and power generation characteristics It turned out that problems such as a decrease occur.

[0013]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that, in a multilayer structure constituting a fuel cell for the purpose of simplifying the manufacturing process, a layer generated when at least two layers are simultaneously fired. As a result of various studies on the cause of phenomena such as peeling and cracking, it was found that the difference in shrinkage at the time of firing is the most significant contribution between two layers having different sintering behaviors. Then, the present inventors intervened a layer having a firing shrinkage ratio intermediate between the two layers between the two layers subjected to the co-firing,
The inventors have found that the above-mentioned peeling and cracking are eliminated, and that a good laminate having no trouble can be obtained, and the present invention has been accomplished.

That is, the method for producing a fuel cell according to the present invention comprises a step of simultaneously firing at least two layers adjacent to each other in the laminate consisting of the air electrode layer, the electrolyte layer, the fuel electrode layer and the current collector layer. In the method for producing a fuel cell according to claim 1, the intermediate layer having a shrinkage factor due to firing having an intermediate behavior of the shrinkage factor of the two layers is interposed between the selected two layers, and the simultaneous firing is performed. And
In particular, it is desirable that the intermediate layer contains a composition of either of the two layers or a composition of both of the two layers.

In describing the present invention in detail, the case of producing a cylindrical fuel cell will be described as an example.

In the cylindrical fuel cell, as shown in FIG. 1, a porous air electrode layer 2, a solid electrolyte layer 3 and a porous fuel electrode layer 4 are formed on the surface of a cylindrical substrate 1 made of a porous ceramic. Further, it is composed of a laminated body in which the current collector layer 5 is laminated. In some cases, the air electrode layer 2 also serves as the cylindrical substrate 1 due to its structure. Furthermore, various configurations are known, such as when the arrangement of the air electrode layer 2 and the fuel electrode layer 4 with respect to the solid electrolyte layer 3 is reversed.

The manufacturing method of the present invention includes a step of simultaneously firing at least two adjacent layers of the above-mentioned laminated body. In that case, as the two layers to be selected, at least one layer of the solid electrolyte layer 3 and the current collector layer 5 that are dense, and the porous cylindrical substrate 1, the air electrode layer 2, and the fuel electrode layer 4 are used. Is most suitable when a combination with at least one layer selected from the above is co-fired, and among them, at least the air electrode layer 2 and the solid electrolyte layer 3, or the air electrode layer 2
And a current collector layer 5 are combined, and a case of combining these two layers and simultaneously firing other layers is also included. Considering the mass productivity and the cost of the fuel cell, in the configuration of FIG. 1, at least the cylindrical substrate 1-air electrode layer 2-
When the air electrode layer 2 also serves as the cylindrical substrate 1, the solid electrolyte layer 3 is co-fired with the air electrode layer 2 and the solid electrolyte layer 3, and further, the cylindrical substrate 1, the air electrode layer 2, and the solid electrolyte layer. 3,
It is most economical to fire all of the fuel electrode layer 4 and the current collector layer 5 at the same time.

Therefore, the case where the air electrode layer 2 and the solid electrolyte layer 3 are simultaneously fired will be specifically described. First, a sheet-shaped molded body (hereinafter referred to as an air electrode sheet) forming the air electrode layer and a solid electrolyte layer. A sheet-shaped molded body (hereinafter, referred to as a solid electrolyte sheet) that forms the is prepared. These sheet-shaped molded products are produced by known methods such as extrusion molding, hydrostatic molding (rubber press), and doctor blade method.

The powder for forming the air electrode layer is LaM
The nO ₃ -based composition may be mentioned, and specifically, La of 15 to 15 may be used.
40% is Ca, Sr, Ba and other alkaline earth elements and Y
And known LaMnO substituted with rare earth elements and the like
₃ type composition etc. can be used. In this case, the powder before forming has a suitable average particle diameter L after calcination of a mixture of the oxide powders of the above-mentioned constituent metals in a predetermined ratio and pulverization.
It is preferably an aMnO ₃ based solid solution powder. Also,
As the solid electrolyte forming powder, Y ₂ O ₃ , Yb ₂ O ₃ may be used.
Stabilized ZrO ₂ powder was a solid solution of stabilizing material in an amount of 5 to 20 mol% ZrO ₂ powder or the part of Zr was replaced with Ce, are used, such as.

The thickness of the air electrode sheet is 50 to 300.
The appropriate thickness is 0 μm and the thickness of the solid electrolyte sheet is 10 to 300 μm. Further, when forming a thick air electrode sheet, a plurality of sheets having a thickness of 100 to 300 μm may be stacked.

Next, when laminating the air electrode sheet and the solid electrolyte sheet obtained as described above, an intermediate layer is interposed between both sheets. In this case, it is important that the intermediate layer is made of a material having an intermediate value of contraction rate during firing of the air electrode and the solid electrolyte. As the intermediate layer having such a property, depending on the material forming the air electrode or the solid electrolyte, when the air electrode is a LaMnO ₃ system composition, the shrinkage factor when firing at 1500 ° C. for 5 hours is 8
10%, the solid electrolyte is Y ₂ O ₃ stabilized ZrO ₂
If the solid electrolyte is composed of 13 to 15%, the solid electrolyte has a larger shrinkage ratio. Therefore, the intermediate layer is larger than the air electrode and smaller than the solid electrolyte, and the shrinkage ratio is about 10 to 13%. Is.

The intermediate layer having such characteristics can be made of a material completely different from the air electrode and the solid electrolyte. In this case, the thermal expansion coefficient and the like should be taken into consideration in addition to the thermal contraction behavior. Since it is necessary to select and control the material, and it is difficult to control the material, it is preferable that one or both components of the two layers be used. When it is composed of either one of the components, the particle diameter of the powder used and the density of the molded body of the intermediate layer are controlled, and when the intermediate layer is formed of the LaMnO ₃ type material as described above, for example,
When crushing the LaMnO ₃ -based powder obtained by calcination, the shrinkage rate is larger than that of the air electrode by making it larger than that of the air electrode forming powder or by making the green density during molding smaller than that of the air electrode. A layer is obtained. When the intermediate layer is composed of Y ₂ O ₃ -stabilized ZrO ₂ , the particle size of this powder is made smaller than that of the solid electrolyte layer, or the density at the time of molding is made larger than that of the solid electrolyte layer, so that shrinkage occurs. The rate can be smaller than that of the solid electrolyte.

The easiest way is to use this intermediate layer
It may be composed of both components of one layer. That is, L
By using a powder in which aMnO ₃ based powder and Y ₂ O ₃ stabilized ZrO ₂ powder are appropriately mixed, it is possible to easily form an intermediate layer having an intermediate shrinkage ratio.

When the intermediate layer contains an air electrode component, the thickness of the intermediate layer is preferably 100 to 300 μm. If the crystal grain size is less than 2 μm, the gas permeability will be poor, and if it exceeds 13 μm, the sinterability will be poor and the electrical conductivity will be reduced, which may adversely affect the power generation characteristics. .

The intermediate layer may be applied as a slurry between the air electrode sheet and the solid electrolyte sheet, or may be interposed as a sheet-like molded body for intermediate layer (hereinafter referred to as intermediate layer sheet).

Then, a laminate in which the above intermediate layer is formed between the air electrode sheet and the solid electrolyte sheet is 1300 to 16
By firing at 00 ° C. for about 3 to 15 hours, it is possible to produce a laminate that constitutes a part of the fuel cell unit.

Also, when the air electrode layer and the current collector layer are co-fired, the intermediate layer may be constructed in the same manner as when the air electrode layer and the solid electrolyte layer are co-fired. For the current collector layer, a known LaCrO ₃ type composition is used, and in addition to the perovskite type composition proposed in Japanese Patent Application Nos. 5-2718484 and 6-27806, the periodicity is excessive. Table LaCrO ₃ containing Group 2a or Group 3a elements
A system composition. Also in this case, similarly to the above, the intermediate layer is composed of the constituent components of the air electrode layer or the constituent components of the current collector layer, or a mixed component thereof, and the shrinkage ratio is between the air cathode layer and the current collector layer. The component composition, the particle size of the powder, the density of the intermediate layer, and the like may be appropriately adjusted so that the target values are obtained. Since the shrinkage rate of the current collector made of the LaCrO ₃ system composition due to firing is 13 to 14%, the shrinkage rate of the intermediate layer in this case should be adjusted to approximately 10 to 12%.

According to the invention, the intermediate layer, which has an intermediate value of the shrinkage of the two layers which are co-fired, may be a single layer, but in the case where the shrinkage of the two layers is significantly different. Of course, it is also possible to form a plurality of layers so that the shrinkage rate gradually changes.

A method for producing a cylindrical fuel cell will be described based on the co-firing method of the air electrode layer and the solid electrolyte layer or the co-firing method of the air electrode layer and the current collector layer as described above.

When the cylindrical base 1 as shown in FIG. 1 is present in the cylindrical fuel cell, first, the powder forming the cylindrical base is extruded or hydrostatically pressed (rubber press). By a method or the like, a molded body for a cylindrical substrate having a wall thickness of about 1 to 3 mm (hereinafter sometimes referred to as a cylindrical molded body) is produced. As the insulating ceramic powder forming this cylindrical substrate, ZrO ₂ containing 10 to 20 mol% of CaO or 5 to 20 mol% of Y ₂ O ₃ is added to ZrO _2.
In addition to system materials, the coefficient of thermal expansion from room temperature to 1000 ° C is 9
A porous ceramic material of up to 11 × 10 ⁻⁶ / ° C. is most suitable, but this cylindrical molded body can be fired separately to prepare a cylindrical substrate, but it is almost the same as the air electrode material and the solid electrolyte material. If it is a ceramic material that can be fired at various temperatures,
It can be fired at the same time as the air electrode and the solid electrolyte.

That is, after the air electrode sheet, the slurry or sheet for the intermediate layer and the solid electrolyte sheet as described above are sequentially wound around the surface of the produced cylindrical molded body or sintered body, a laminated body is produced. , 1300 in the atmosphere
By firing at 1600 ° C. for about 3 to 15 hours, the solid electrolyte has a relative density of 96% or more, and the cylindrical substrate and the air electrode have a relative specific gravity of about 60 to 75%.
An integrated sintered product of the air electrode and the solid electrolyte can be obtained.

In another embodiment, when the air electrode layer also serves as a cylindrical substrate, the air electrode forming powder is used to form a cylindrical shape by extrusion molding or a rubber pressing method, and then this cylindrical molded body is formed. Apply the slurry for the intermediate layer on the surface,
Alternatively, the intermediate layer sheet and the solid electrolyte sheet may be wrapped around this and simultaneously fired under the same firing conditions.

Thereafter, a slurry of components for forming a current collector layer and a fuel electrode layer is applied to the surface of the integrally sintered product of the cylindrical substrate, the air electrode and the solid electrolyte by a screen printing method or a doctor blade method. After applying the sheet-shaped molded body produced by the above method to the surface of the integrally sintered product, or winding and adhering it, 1300 in an oxidizing atmosphere such as air
A fuel cell can be produced by firing at ˜1600 ° C. for 3 to 15 hours.

Desirably, the composition and the like of the current collector layer and / or the fuel electrode layer are adjusted, and it is preferable that the current collector layer and / or the fuel electrode layer are simultaneously fired together with the cylindrical substrate, the air electrode layer and the solid electrolyte layer.
In that case, as described above, on the surface of the cylindrical laminate composed of the cylindrical molded body-air electrode sheet-solid electrolyte sheet, or the cylindrical laminated body composed of the air electrode cylindrical molded body-solid electrolyte sheet, A cylindrical substrate is obtained by applying a slurry for forming an electric body layer and / or a fuel electrode layer, or winding and adhering a sheet-like molded body, and then firing this in an oxidizing atmosphere at 1300 to 1600 ° C. , The air electrode, the solid electrolyte, the fuel electrode and / or the current collector layer can be simultaneously sintered. Also at this time, as described above, between the current collector layer and the solid electrolyte layer, between the fuel electrode layer and the solid electrolyte layer, or between the air electrode layer and the current collector layer, the intermediate layer as described above. It is desirable to interpose. The current collector layer has a relative specific gravity of 95% or more, and the fuel electrode layer has a relative density of 80 to 100.
It is necessary to adjust so that it becomes%.

The constituents of the fuel electrode layer are
Ni powder or NiO powder containing 10 to 40% by weight of ZrO ₂ powder containing Y ₂ O ₃ is suitable.

The present invention has been described by taking the cylindrical fuel cell as an example, but the present invention is not limited to this, and the flat sheet fuel cell also has an air electrode sheet and a solid electrolyte sheet. In the case of laminating and co-firing, the co-firing is performed by interposing an intermediate layer having an intermediate value of firing shrinkage behavior between two layers by a method similar to that of the cylindrical type.

According to the present invention, it is preferable to reduce the number of firing steps in the above method as much as possible. In particular, firing the cylindrical substrate, the air electrode, the solid electrolyte, the fuel electrode and the current collector layer at the same time is a manufacturing process. Is particularly desirable because it can be significantly reduced.

[0038]

[Function] The air electrode and the fuel electrode forming the fuel cell are composed of a porous ceramic layer for supplying oxygen gas or fuel gas to the solid electrolyte layer, whereas the solid electrolyte or interconnector layer is It is composed of a dense ceramic layer.

FIG. 3 shows the relationship between the firing time and the shrinkage ratio with respect to the dimension before firing when firing the porous ceramic layer and the dense ceramic layer at the same time. According to FIG. 3, the dense ceramic layer, as indicated by the line segment A in FIG. 3, gradually shrinks after reaching the firing start temperature, shrinks to some extent, and shrinks when approaching the theoretical density. The speed tends to decrease. On the other hand, the porous ceramic layer gradually shrinks after the sintering start temperature as shown by the line B in FIG. 3, but is burned at the time t when the dense ceramic layer is completely sintered. Since it is necessary to be in the middle of bonding, it is necessary that the shrinking speed is slower than that of the dense ceramic layer. When two ceramic layers exhibiting such a sintering behavior are co-fired in a state of being adjacent to each other, peeling or cracking is likely to occur due to the difference in the behavior.

Therefore, according to the present invention, a ceramic layer having an intermediate property of the sintering behavior of these two ceramic layers is interposed as an intermediate layer. The ceramic layer as the intermediate layer has a thickness of 2 as shown by a line segment C in FIG.
This shows an intermediate behavior between the two sintering curves A and B.

By interposing such an intermediate layer, the extreme difference in the behavior between the two layers during sintering is relaxed, so that the peeling or cracking of one layer is suppressed even in the co-firing. can do.

As a result, it is possible to manufacture the fuel cell by co-firing, improve the yield at the time of co-firing, and provide a low cost fuel cell.

[0043]

EXAMPLE Next, the following experiment was conducted on the effect of interposing a specific intermediate layer upon simultaneous firing of at least two layers of the fuel cell.

Example 1 First, in an experiment, an air electrode sheet, a solid electrolyte sheet and a current collector sheet were prepared as follows among the layers constituting a fuel cell.

(Air electrode sheet) As powders forming the air electrode, powders of La ₂ O ₃ , MnO ₂ and CaCO ₃ are La.
After weighing and mixing so that _0.85 Ca _0.15 MnO ₃ was obtained, 1
It was calcined at 500 ° C. for 3 hours and pulverized to obtain a solid solution powder having an average particle size of about 8 μm and about 10 μm. Next, the above La _0.8 C
A binder was added to a _0.2 MnO ₃ powder, and an air electrode sheet having a thickness of 2 mm was prepared by an extrusion molding method.

[0046] (solid electrolyte sheet) Moreover, the average particle size of the Y ₂ O ₃ as a powder to form a solid electrolyte was produced by a commercial coprecipitation a proportion of 10 mol% of about 1μm and about 2 [mu] m Y ₂ An O ₃ stabilized ZrO ₂ powder was prepared. A slurry was prepared from these Y ₂ O ₃ -stabilized ZrO ₂ powders using water as a solvent, and solid electrolyte sheets each having a thickness of 100 μm were prepared by the doctor blade method.

The average particle diameter as a powder for forming the (current collector sheet) current collector is about 1μm and about 3μm La _0.80 Ca _{0. 21}
A compound powder made of CrO ₃ was prepared. Using these powders, a slurry was prepared using water as a solvent, and collector sheets each having a thickness of 100 μm were prepared by the doctor blade method.

Experiment 1 Next, when the air electrode sheet and the solid electrolyte sheet were co-fired, various intermediate layer-forming powders to be interposed between the sheets were prepared. As shown in Table 1, one of which, La ₂ O _3, MnO _2, a powder of CaCO ₃ La _0.85 Ca _{0. 15} after 3 hours and calcined at 1500 ° C. After weighing mixed so that MnO ₃ , Crushed and average particle size is 2
A solid solution powder of ˜12 μm was obtained. The other is Y
Y ₂ O ₃ -stabilized Zr having an average particle size of 1 to 4 μm prepared by a commercial coprecipitation method containing ₂ O ₃ in a proportion of 10 mol%.
O ₂ (YSZ) powder was prepared. Water and a binder were added to this powder, and an intermediate layer sheet having a thickness of 100 μm was produced by the doctor blade method. Also, La _0.85 Ca _0.15
An intermediate layer sheet in which MnO ₃ and YSZ powder were mixed was also prepared by the same method.

With respect to the above-mentioned cylindrical molded body, sheet-shaped molded body and powder for the intermediate layer, the shrinkage rate under the simultaneous firing conditions was measured separately. The shrinkage ratio was calculated by {(volume before firing-volume after firing) / volume before firing} × 100 (%).

Next, the intermediate layer sheet shown in Table 1 was placed on the surface of the air electrode sheet, and the solid electrolyte sheet was overlaid thereon to form about 1 layer.
It pressure-bonded at a pressure of 0 kg / cm ² . And each laminated body was co-fired in the atmosphere at 1450 to 1550 ° C. for 5 hours.

Adhesion was evaluated for the obtained laminated sintered body. The adhesiveness was evaluated by performing a visual inspection for the presence or absence of peeling or cracks in the laminated sintered body.

[0052]

[Table 1]

As is clear from Table 1, in No. 1 in which no intermediate layer is formed between the air electrode layer and the solid electrolyte layer,
Peeling occurred in the electrolyte layer, and the adhesion after co-firing was insufficient. In the samples co-fired with the intermediate layer interposed therebetween, peeling and cracking of the electrolyte also occurred in Samples No. 2, 5, and 6 in which the contraction rate of the intermediate layer was not an intermediate value between the air electrode layer and the solid electrolyte layer. It was

On the other hand, in the product of the present invention in which the intermediate layer having a contraction rate of the intermediate layer having an intermediate value between the air electrode layer and the solid electrolyte layer is interposed, no peeling or cracking of the electrolyte is observed. , Showed excellent adhesion.

Experiment 2 Next, when the air electrode sheet and the current collector sheet were simultaneously fired, various intermediate layer-forming powders to be interposed between the sheets were prepared. The composition of the intermediate layer is shown in Table 2. La _0.85 Ca _0.15 MnO forming the intermediate layer
_{The 3} type powder is 1500 ° C after the powders of La ₂ O ₃ , MnO ₂ and CaCO ₃ are weighed and mixed so as to have the above composition.
After calcination for 3 hours, it was pulverized to obtain a solid solution powder having an average particle size of 3 to 6 μm. The La _0.8 Ca _90.21 CrO ₃ based powder was _{prepared by mixing} the La ₂ O ₃ , Cr ₂ O ₃ and CaCO ₃ powders so as to be La _0.80 Ca _0.21 CrO ₃ and calcining at 1400 ° C. for 3 hours. Crushed to an average particle size of 2
This is a powder of about 12 μm. Using these powders, an intermediate layer sheet was produced by the doctor blade method according to Example 1.

Next, the intermediate layer sheet shown in Table 2 was placed on the surface of the air electrode sheet and the solid electrolyte sheet was overlaid thereon.
It was pressure-bonded at a pressure of kg / cm ² . And each laminated body was co-fired in the atmosphere at 1450 to 1550 ° C. for 5 hours. With respect to the obtained laminated sintered body, the adhesion was evaluated by the same method as in Experiment 1.

[0057]

[Table 2]

As is apparent from Table 2, when no intermediate layer was formed between the air electrode layer and the current collector layer, Sample N
In o.14, peeling of the current collector layer occurred and adhesion after co-firing was insufficient.

In the samples co-fired with an intermediate layer interposed therebetween, the samples of which the shrinkage factor of the intermediate layer is not an intermediate value between the air electrode layer and the current collector layer, Nos. 15, 18, and 21 have satisfactory adhesion. The sex was not obtained.

On the other hand, in the product of the present invention in which the intermediate layer having the intermediate layer having a contraction rate intermediate between the air electrode layer and the current collector layer is interposed, neither peeling of the electrolyte nor cracking is observed. ,
It showed excellent adhesion.

Example 2 A fuel cell was prepared based on the results of Experiments 1 and 2 above. First, as a molded body for a cylindrical substrate, a binder was added to CaO-stabilized ZrO ₂ powder having an average particle size of 10 μm in which a commercially available 15 mol% CaO was added as a powder for forming a cylindrical substrate, and the mixture was extruded by an extrusion molding method. A cylindrical molded body having a diameter of 18 mm and an inner diameter of 13 mm was obtained.

On the other hand, on one side of the air electrode sheet used in Experiment 1, an intermediate layer sheet having the same composition as Sample Nos. 3, 8, and 11 in Experiment 1 was placed at the position where the current collector layer was laminated. An intermediate layer sheet having the same composition as Sample Nos. 16, 20, and 24 in Experiment 2 was laminated and wound around the surface of the cylindrical molded body so that the intermediate layer sheet was on the outside. And
The solid electrolyte sheet in Experiment 1 and the current collector sheet in Experiment 2 were wound around predetermined places.

Further, as powder for forming the fuel electrode, Ni was used.
Water was added as a solvent to a mixed powder in which O powder and ZrO ₂ (containing 10 mol% Y ₂ O ₃ ) powder were mixed at a weight ratio of 70:30 to prepare a slurry, and the thickness was measured by a doctor blade method. A sheet of NiO / ZrO ₂ having a thickness of 50 μm was produced and wound around a solid electrolyte sheet at a predetermined position with an acrylic resin adhesive interposed to produce a cylindrical laminate.

The laminated body produced in this manner is set to 1500
A fuel cell was produced by co-firing at 5 ° C. for 5 hours. The power density was measured by conducting an electric power generation test at 1000 ° C. by flowing oxygen gas inside and hydrogen gas outside on the fuel cell thus obtained. The results are shown as cells Nos. 1 to 3 in Table 3.

Example 3 Using the powder for forming an air electrode used in Experiment 1, a cylindrical air electrode formed body having an inner diameter of 18 mm and an outer diameter of 13 mm was produced by an extrusion molding method. On the surface of this cylindrical molded body, in the positions where the solid electrolyte sheet is arranged, the samples No. 3, 9 in Experiment 1 and the intermediate layer sheets of the samples No. 16, 9 in Experiment 2 are arranged in the positions where the current collector sheet is arranged. The interlayer sheets were laminated. Then, the solid electrolyte sheet used in Experiment 1 and the current collector sheet used in Experiment 2 were laminated at the coating positions of the respective intermediate layer slurries using acrylic resin as an adhesive. After that, the fuel electrode sheet used in Example 2 was laminated on the surface of the solid electrolyte sheet with an acrylic resin as an adhesive so as not to come into contact with the current collector sheet, to produce a cylindrical laminate.

Then, this cylindrical laminate was fired at 1550 ° C. for 2 hours. The power density was measured by conducting an electric power generation test at 1000 ° C. by flowing oxygen gas inside and hydrogen gas outside on the fuel cell thus obtained. The results are shown in cells Nos. 4 to 6 of Table 3.

[0067]

[Table 3]

Other cells produced according to the present invention are:
There was no peeling or cracking of the electrolyte layer or the current collector layer, and all showed high power density.

[0069]

As described in detail above, according to the present invention,
By interposing an intermediate layer between two layers that have different shrinkage rates when performing co-firing, it is possible to prevent layer peeling and cracks during co-firing, and to significantly reduce the number of fuel cell manufacturing processes. By being able to reduce the amount, it is possible to improve mass productivity and to manufacture a highly reliable fuel battery cell.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a cylindrical fuel cell unit.

FIG. 2 is a view showing a structure of a flat plate type fuel cell unit.

FIG. 3 is a diagram showing a relationship between a firing time and a shrinkage ratio with respect to a dimension before firing when firing a porous ceramic layer and a dense ceramic layer at the same time.

[Explanation of symbols]

 1 Cylindrical substrate 2 Air electrode layer 3 Solid electrolyte layer 4 Fuel electrode layer 5 Current collector layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Kimura 1-4 Yamashita-cho, Kokubun-shi, Kagoshima Kyocera Corporation General Research Institute

Claims (5)

[Claims] 1. A method for producing a fuel cell, comprising the step of simultaneously firing at least two adjacent layers of a laminate having an air electrode layer, an electrolyte layer, a fuel electrode layer, and a current collector layer. A method for producing a fuel cell, comprising performing co-firing with an intermediate layer interposed between two layers, the intermediate layer having a contraction rate of the intermediate value of the two layers. 2. The method for producing a fuel cell according to claim 1, wherein the intermediate layer contains a component of either one of the two layers or a component of both of the two layers. 3. The method for producing a fuel cell according to claim 1, wherein the two layers are a combination of a dense layer and a porous layer. 4. The method for producing a fuel cell according to claim 3, wherein the two layers are a combination of at least one of a solid electrolyte layer and an air electrode layer, and a current collector layer and an air electrode layer. 5. A method for producing a fuel cell, comprising the step of simultaneously firing at least two layers adjacent to each other in a laminate having an air electrode layer, an electrolyte layer, a fuel electrode layer and a current collector layer. A method for producing a fuel cell, comprising: performing co-firing with an intermediate layer made of a mixture of the constituents of the two layers interposed between the two layers.