JPH10162847A - Solid electrolyte fuel cell, and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell, and a manufacturing method thereof in which gas seal to a cell main body can be easily and securely achieved, and in which recognition of the gas seal is easy. SOLUTION: An air electrode 2 is formed on one surface of a cylindrical solid electrolyte, a fuel electrode 4 is formed on the other surface, and a cap- shaped seal member 11 comprising ceramic is engaged with an outer circumferential surface at one end part of a cylindrical cell main body 8 having a collector 5 electrically connected to the air electrode 2 or the fuel electrode 4 and exposed to an outer surface through a gas seal layer 9 comprising ceramic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottomed tubular solid oxide fuel cell and a method for producing the same.

[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, solid oxide fuel cells include:
A cylindrical type and a flat type are known. The flat fuel cell has the feature that the power density per unit volume of power generation is high, but there are problems such as imperfect gas sealing and non-uniformity of the temperature distribution in the cell in practical use. In contrast, cylindrical fuel cells have a low power density,
It has the features that the mechanical strength of the cell is high and that the temperature inside the cell can be kept uniform.

In both types of solid oxide fuel cells,
R & D is being actively promoted by taking advantage of each feature.

As shown in FIG. 3, a single cell of a cylindrical fuel cell has a support tube 1 made of CaO-stabilized ZrO ₂ having an open porosity of about 40%, and a porous air made of LaMnO ₃ material on the support tube 1. A pole 2 is formed, and Y ₂ O ₃ stabilized Zr is formed on its surface.
A solid electrolyte 3 made of O ₂ is covered, and a porous Ni-zirconia fuel electrode 4 is provided on this surface. In the fuel cell module, each single cell is La
It is connected via a CrO ₃ -based current collector (interconnector) 5. For power generation, air (oxygen) 6 inside the support tube 1,
The fuel (hydrogen) 7 is allowed to flow to the outside, and the heating is performed at a temperature of 1000 to 1050C.

In recent years, a LaMnO ₃ -based material, which is an air electrode material, has been used directly as a porous support tube in order to simplify the process in the cell manufacturing process. As a support tube material having the function as an air electrode, La
The LaMnO ₃ solid solution material obtained by substituting 10-15 atomic% in 20 atomic% or Sr with Ca is used.

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

Recently, 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. In this co-sintering method, for example, a solid electrolyte molded body and a molded body for a current collector are wound around a molded body of a cylindrical air electrode support tube in a roll shape and simultaneously fired, and then the fuel electrode is formed on the surface of the solid electrolyte layer. This is a method of forming a layer. This co-sintering method is advantageous for improving the yield and manufacturing cost during the production of the cell since the number of production steps is reduced.

Conventionally, one end of the cell is sealed by setting a cylindrical cell body obtained by sintering to a mounting member in a furnace for actually generating power, and forming a glass layer formed on the mounting member. Was brought into contact with one end of the cell body, the glass layer was melted at the time of temperature rise during power generation, and one end of the cell body was sealed with the mounting member.

Further, a bottomed cylindrical molded body for a sealing member is made of the same material as the air electrode molded body and the air electrode molded body, and one end of the air electrode molded body and one end of the molded body for the sealing member are connected. After the contact and firing, as described above, a solid electrolyte, such as an electrochemical deposition method (EVD method) or a plasma spray method,
A fuel electrode and a current collector are sequentially formed, and a dense ceramic layer is formed on the surface of the sealing member by an electrochemical vapor deposition method (EVD method) or a plasma spraying method to prevent gas leakage from the sealing member. I was

[0011]

However, according to the conventional method of sealing one end of a fuel cell with a mounting member using a glass material, the fuel cell is completely sealed when power is actually generated. It is difficult to confirm whether or not it is stopped, and it is easy for the single cell output to decrease due to poor sealing,
In particular, in the case of stacking, there is a problem that sealing failure is likely to occur due to an increase in the number of sealing portions, and as a result, the output is reduced.

Further, in the method of firing in a state in which one end of the cathode forming body and one end of the sealing member forming body are in contact with each other, it is difficult to join the cathode forming body and the sealing member, and furthermore, the gas leakage Electrochemical deposition method (EVD method)
It is necessary to form a dense ceramic layer on the surface of the sealing member by a plasma spraying method or the like, and there is a problem that the sealing step is troublesome and costly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid oxide fuel cell capable of easily and reliably performing gas sealing of a cell main body and easily confirming the gas seal, and a method of manufacturing the same.

[0014]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventors have applied a ceramic slurry to the outer peripheral surface of one end of a cell body, and formed a ceramic molding for a sealing member thereon. The body is externally fitted and fired, and fitted to one end of the cell body by firing shrinkage of the sealing member, whereby one end of the cell body can be easily and reliably sealed, and the sealed state can be improved. They have found that they can be easily confirmed, and have reached the present invention.

That is, in the solid oxide fuel cell of the present invention, an air electrode is formed on one surface and a fuel electrode is formed on the other surface of a cylindrical solid electrolyte, and the solid electrolyte is electrically connected to the air electrode or the fuel electrode. A cap-shaped sealing member made of ceramics is externally fitted to the outer peripheral surface of one end of a cylindrical cell body having a current collector exposed on the outer surface via a gas seal layer made of ceramics. Things.

Further, the method of manufacturing a solid oxide fuel cell according to the present invention comprises a step of manufacturing a cell body having at least a solid electrolyte, an air electrode and a current collector; A step of applying a rally, a step of inserting one end of the cell body to which the ceramic slurry has been applied into a cap-shaped ceramic molding for a sealing member, and baking to remove the sealing member to one end of the cell body. Fitting step.

Here, a step of producing a cylindrical air electrode calcined body having a cell body, a step of laminating a solid electrolyte molded body on the surface of the air electrode calcined body and calcining the same, Polishing the surface of the calcined body to expose a part of the air electrode calcined body, and laminating a current collector compact on the surface of the solid electrolyte calcined body and the air electrode calcined body; And baking the laminated molded body.

[0018]

In the solid oxide fuel cell according to the present invention, one end of the cell body is not sealed with the mounting member when the cell body for power generation is set in the furnace and the power is generated as in the prior art. At the manufacturing stage, one end of the cell body is sealed with dense ceramics, so that one end of the cell body can be easily and reliably sealed, and the sealed state before setting the power generation cell body in the furnace. Can be confirmed,
Gas sealing performance during power generation is sufficiently ensured.

That is, in the solid oxide fuel cell of the present invention, a ceramic slurry is applied to the outer peripheral surface of one end portion of the cell body, and a ceramic molded body for a sealing member is fitted on the upper surface and fired. The ceramic molded body for the sealing member is fired and shrunk and fitted to one end of the cell body, and at the same time, the outer surface of the cell body and the inner surface of the sealing member are joined at the time of firing, so that one end of the cell body can be easily and easily sealed. It can be done reliably.

In particular, in the solid oxide fuel cell according to the present invention, a ceramic slurry is applied to the outer peripheral surface of one end of the cell body to form a gas seal layer made of ceramic.
Since the sealing member is fitted on the outer peripheral surface, the sealing member is fitted by the gas seal layer even when the outer peripheral surface of the cell main body has irregularities due to the current collector protruding from the cell main body. Part of the outer peripheral surface of the cell body is smoothed, and the sealing member and the cell body can be more closely adhered to each other without gaps, so that the gas sealing property can be improved.

According to the method of the present invention, for example, when a ZrO ₂ or LaCrO ₃ based porcelain is used as the sealing member, the firing temperature (1300 ° C. or higher) of the porcelain is changed to the actual power generation temperature (1300 ° C.). (1000 ° C.), there is no risk of gas leak during power generation, and as a result, the reliability of the cell output and the long life can be achieved. Furthermore, when assembling a stack using a plurality of cells, the number of sealing portions at the stage of generating power can be reduced as much as possible, thereby facilitating system design.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid oxide fuel cell according to the present invention has a cylindrical air electrode 2 as shown in FIGS.
A solid electrolyte 3 is formed on the surface of the solid electrolyte 3, a fuel electrode 4 is formed on the surface of the solid electrolyte 3, and a current collector 5 electrically connected to the air electrode 2 is provided to form a cell body 8. .

A gas seal layer 9 made of ceramic is formed on the outer peripheral surface of one end of the cell body 8.
A sealing member 11 made of a cap-shaped dense ceramic is externally fitted on the surface of the gas seal layer 9.
The cell body 8, the gas seal layer 9, and the sealing member 11 are integrated by firing. That is, by applying a ceramic slurry to the outer peripheral surface of one end of the cell main body 8 to eliminate and flatten the outer peripheral surface of the cell main body 8, the ceramic molded body for a sealing member is externally fitted and fired. At the same time, the ceramic molded body for the sealing member shrinks by firing, and is fitted to one end of the cell body 8, and at the same time, the outer peripheral surface of the cell body 8 and the inner surface of the sealing member 11 are interposed via the gas seal layer 9 during firing. Are joined.

The gas seal layer 9 is made of, for example, a partially stabilized Z
Various materials such as rO ₂ , stabilized ZrO ₂ , and LaCrO ₃ can be used, but it is particularly preferable to use the same material as the solid electrolyte material from the viewpoint of the coefficient of thermal expansion. The thickness of the gas seal layer 9 may be such as to eliminate irregularities on the outer surface of the cell body 8, but is preferably 50 to 300 mm.

The sealing member 11 is made of dense ceramics in order to prevent gas leakage. For the dense ceramics, for example, the same material as the gas seal layer 9 can be used. Further, similarly to the gas seal layer 9, it is desirable to form the same material as the solid electrolyte material from the viewpoint of the coefficient of thermal expansion. The thickness t of the outer fitting portion 13 of the sealing member 11 abutting on the outer surface of the cell body 8 is set at 0.3 to suppress the increase in the diameter of the cell and to prevent the cell from being damaged by shrinkage stress during sintering. ~ 1.2 mm is desirable.

A method for manufacturing such a solid oxide fuel cell will be described in detail. First, in order to produce a cell main body, a cylindrical air electrode molded body having a function as a self-supporting tube is produced by extrusion molding, and thereafter, 1200 to 13
The binder is decalcified and calcined at a temperature of 00 ° C. for about 5 to 20 hours to produce a calcined cathode. This calcined cathode is
A LaMnO ₃ -based material having a perovskite-type crystal phase as a main phase, and having an average crystal grain size of 3 to 20 μm, particularly 5 to 1 μm.
Desirably, it is 5 μm. This is because if the particle diameter of the main crystal phase is smaller than 3 μm, the gas permeability is low although the strength is high, and if it exceeds 20 μm, the gas permeability is high but the strength is insufficient. The open porosity of the air electrode is suitably from 20 to 45%, particularly from 30 to 40%. An average pore diameter in the range of 1.0 to 5.0 μm is excellent in gas permeability.

Next, a molded layer of the material constituting the solid electrolyte is formed on the surface of the calcined cathode. This solid electrolyte molded body layer is prepared by using a powder of ZrO ₂ stabilized with a known stabilizer such as Y ₂ O ₃ having an average particle diameter of 0.5 to 3 μm to prepare a slurry, and then a doctor is prepared. It is formed by winding a green sheet produced by a blade method or the like.

Then, the air electrode / solid electrolyte molded body is
The calcined body is calcined at a temperature of 0 to 1300 ° C. for about 1 to 3 hours, and thereafter, the surface of the calcined solid electrolyte, which is a laminated portion of the current collector, is smoothly polished to expose the calcined cathode. A molded body for a current collector is laminated on the surface of the calcined body and the calcined cathode. The molded body for the current collector uses a LaCrO ₃ material,
It is formed by laminating green sheets in the same manner as the solid electrolyte molded body.

The laminate thus manufactured is placed in an oxidizing atmosphere such as the air at a temperature of 1300 to 1600 ° C. for 3 to 3 hours.
Co-sintering is performed by simultaneous firing for about 15 hours to produce a cylindrical cell body.

The fuel electrode uses a porous cermet material containing 30 to 80% by weight of Ni and the balance of stabilized ZrO ₂ (including a stabilizer such as Y ₂ O ₃ ). After forming a molded body layer at a predetermined portion of the sintered body and sintering, or after forming the air electrode / solid electrolyte / current collector molded body, a fuel electrode molded body is further laminated and fired simultaneously. Alternatively, a cylindrical cell body can be manufactured.

Next, for example, the same slurry as that of the solid electrolyte molded body is used, and for example, one end of the cell body is immersed (dipped) in the slurry, so that the ceramic slurry is applied to the outer surface of one end of the cell body. Apply, 100
Dry at ~ 150 ° C for 1-3 hours. Other methods of applying the ceramic slurry include spraying, brushing, and the like. It is desirable that the ceramic slurry be applied in an area slightly larger than a portion where the sealing member is externally fitted. The coating thickness is not particularly limited as long as the unevenness on the outer peripheral surface of the cell body is eliminated.

Since the sealing member is required to have gas sealing properties during power generation, for example, ZrO ₂ -based or LaCrO ₃ -based oxide powder having an average crystal grain size of about 0.5 to 3 μm is extruded or subjected to hydrostatic pressure. It is formed by molding (rubber press) or the like, and cut into a cap shape to produce a ceramic molded body for a sealing member.

At this time, the ceramic molding for a sealing member is
It is desirable that the thickness of the molded body of the outer fitting portion which abuts on the outer peripheral surface of the cell body and is tightened is 0.7 to 2.0 mm. This is because if the sealing member is thinner than 0.7 mm, the sealing member may be broken at the time of firing, and if it is thicker than 2.0 mm, a cell when a stack is formed by a plurality of solid oxide fuel cells. This is because electrical connection between them becomes difficult.

The inner diameter of the ceramic molding for a sealing member into which one end of the cell main body is inserted is 1.10 times the outer diameter of the cell main body.
It is desirable that the ratio be 15 to 1.4 times. This is because the inner diameter of the ceramic molded body for the sealing member is 1.times. The outer diameter of the cell body.
If it is smaller than 15 times, cracks due to distortion are likely to occur in the sealing member, and if it is larger than 1.4 times, a gap is generated between the sealing member and the cell body, and sealing cannot be performed. This is because there are cases.

Thereafter, one end of the cell body is inserted into the ceramic molding for a sealing member, and the cell body is placed in an oxidizing atmosphere such as air.
It is fired at a temperature of 300 to 1600 ° C. for about 1 to 5 hours, and a sealing member is fitted to one end of the cell body via a gas seal layer to obtain a solid oxide fuel cell of the present invention. The sealing member and the gas seal layer are integrated at the time of firing, and the gas seal layer and the outer peripheral surface of one end of the cell body are also integrated at the time of firing, whereby the sealing member is connected to the one end of the cell body via the gas seal layer. It will be joined to the outer peripheral surface.

The gas seal layer and the sealing member made of the dense ceramic only need to be able to prevent gas leakage, and preferably have a porosity of 5% or less.

The present invention is characterized in that one end of the cell body is sealed with a sealing member via a gas seal layer.
The method for manufacturing the cell body is not particularly limited, and the cell body may be manufactured by a known method other than the method described above.

Further, in the present invention, after the fuel electrode slurry is applied to a cell body having an air electrode, a solid electrolyte and a current collector, the cell body is inserted into a ceramic molding for a sealing member.
At the same time as the fuel electrode coating film, the ceramic molded body for a sealing member may be baked to bake the fuel electrode on the surface of the solid electrolyte. In this case, a heat treatment step for burning only the fuel electrode can be omitted.

[0039]

EXAMPLES In order to produce a cylindrical solid oxide fuel cell by co-sintering, first, a cylindrical air electrode molded body was produced as follows. La with commercial purity of 99.9% or more
Starting materials such as ₂ O ₃ , Y ₂ O ₃ , CaCO ₃ , and Mn ₂ O ₃ were weighed and mixed so as to have a composition of La _0.56 Y _0.14 Ca _0.3 MnO ₃ , and then calcined at 1500 ° C. for 3 hours. By pulverization, a solid solution powder having an average particle size of 5 μm was obtained. Further, a binder was added to the solid solution powder, and a cylindrical air electrode molded body was produced by an extrusion molding method. After drying, the air electrode molded body was subjected to binder removal and calcination at 1250 ° C. for 10 hours to produce a cylindrical air electrode calcined body.

Next, the Y ₂ O ₃ obtained by the coprecipitation method was added to 8
mol% ZrO ₂ having an average particle size of 1 μm
Toluene and a binder were added to the powder to prepare a slurry, and a 130 μm-thick solid electrolyte sheet was prepared by a doctor blade method.

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 at 1500 ° C. for 3 hours and pulverized to obtain a solid solution powder having an average particle diameter of 2 μm. Next, toluene and a binder were added to the solid solution powder to prepare a slurry, and a current collector sheet having a thickness of 130 μm was prepared by a doctor blade method.

The solid electrolyte sheet was wound around the cylindrical air electrode calcined body in a roll shape and calcined at 1100 ° C. for 3 hours. After calcination, the surface of the solid electrolyte calcined body which is to be a laminated portion of the current collector sheet is polished flat, and the surface is polished up to the exposed air electrode calcined body. Wrapped around. Then, at 1500 ° C in air
For 6 hours.

After co-sintering, ZrO ₂ (10 m
ol% Y ₂ O ₃ ) powder was mixed at a weight ratio of 80:20, water was added as a solvent to prepare a fuel electrode slurry, and a 50 μm thick fuel electrode slurry was applied to the surface of the laminated sintered body. The coating was dried.

Next, ₃ , 8 and 10 mol% of Y ₂ O ₃ were added.
Of ZrO ₂ having an average particle size of 1 μm, respectively.
Powder, La _0.8 Ca _0.22 CrO ₃ , La _0.7 C
a _{0. 32} CrO ₃ and _{La (Mg 0.1 Cr 0.9) 0.99} O 3
A slurry is prepared by adding water as a solvent to each of the LaCrO ₃ -based powders, and one end of the cell body is immersed in the slurry, and a 100 μm-thick ceramic slurry is applied to the outer peripheral surface of one end of the cell by dipping. And dried at 120 ° C. for 1 hour.

Next, a cap-shaped molded body as a sealing member is prepared. First, a ZrO ₂ -based powder having the same composition as the slurry and containing Y ₂ O ₃ at a ratio of ₃ , 8, and 10 mol% and an average particle size of 1 μm, La _0.8 Ca _0.22 CrO ₃ , La _0.7 Ca _0.32 CrO
₃ and _{La (Mg 0.1 Cr 0.9) 0.99} O 3 LaCrO
Hydrostatic pressing (rubber pressing) was performed using each of the _three types of powder, and the powder was cut into a cap shape. Thereafter, one end of the cell coated with the slurry was inserted into a molded body for a sealing member.

The thickness t of the outer fitting portion of the molded body for a sealing member which comes into contact with the outer peripheral surface of the cell body and tightens the cell body is set to 1 mm, and the inner diameter of the cap-shaped molded body is set to the outside of the cell body. The diameter was set to 1.2 times. The outer diameter of the cell body is 14m.
m.

Thereafter, the fuel electrode layer is formed by baking at 1400 ° C. for 2 hours in the atmosphere, and a cap-shaped sealing member is provided on the outer peripheral surface of one end of the cell body via a gas seal layer. Mated.

In the above-mentioned cylindrical cell of one end sealing type, the amount of surface leakage and cell output density, and the amount of surface leakage and cell output after passing through 20 thermal cycles from room temperature to 1000 ° C. Table 2 shows the density results.
It was shown to. The surface leak was measured by reading the value of the degree of vacuum inside the cell 10 minutes after suctioning the inside of the cell to a vacuum state. The results of the surface leak and the cell output density are shown in Table 2. Note that a cell in which a cap-shaped molded body is directly fitted to one end of the cell is described (Sample No. 1,
3). In Table 2, in Sample No. 9, a glass layer (commercial name: made of Pyrex glass) formed on the mounting member was brought into contact with one end of the cell body and heated to 1000 ° C. to melt the glass layer. 4 shows characteristics of a conventional solid oxide fuel cell in which one end of a cell body is sealed with the attachment member.

[0049]

[Table 1]

[0050]

[Table 2]

As is clear from the results in Tables 1 and 2, the sample No. Nos. 2, 4 to 8 each had a surface leak amount of 100 mmTorr or less and were superior in gas sealing properties as compared with the conventional product (No. 9), and each had a power density of 0.3 W / cm ² or more. This suggests an improvement in the power generation performance of the cell.

In addition, the sample No. of the product of the present invention. 2, 4 to 8 have a surface leak amount of 1 even after passing through 20 thermal cycles.
Conventional products (No. 9) and N
o. The gas sealing properties were superior to those of the cells in which the cap-shaped molded body was directly fitted to one end of one or three cells. In addition, the sample of the present invention did not show any deterioration in performance even at the output density.
The value of 3 W / cm ² or more was maintained. From these results,
It is possible to suppress performance degradation even in long-term cell durability.

[0053]

As described in detail above, according to the present invention,
At the cell manufacturing stage, one end of the cell body is sealed with a dense ceramic sealing member via a gas seal layer,
One end of the cell body can be easily and reliably sealed, and the sealed state can be checked before the power generation cell body is set in the furnace. Guaranteed and long-term stable cell performance can be maintained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the structure of a cylindrical fuel cell according to the present invention.

FIG. 2 is a sectional view of an outer fitting portion of the sealing member of FIG.

FIG. 3 is a perspective view showing a cell body of the solid oxide fuel cell.

[Explanation of symbols]

 2 ... air electrode 3 ... solid electrolyte 4 ... fuel electrode 5 ... current collector 8 ... cell body 9 ... gas seal layer 11 ... sealing member 13 ... outside Fitting part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masahide Akiyama 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Inside the Kyocera Research Institute

Claims (3)

[Claims] An air electrode is formed on one surface of a cylindrical solid electrolyte, and a fuel electrode is formed on the other surface, and a current collector electrically connected to the air electrode or the fuel electrode and exposed on the outer surface is provided. A solid oxide fuel cell comprising a cap-shaped sealing member made of ceramics externally fitted to an outer peripheral surface of one end of a cylindrical cell body provided through a gas seal layer made of ceramics. . 2. A step of producing a cell body having at least a solid electrolyte, an air electrode and a current collector, and a step of applying a ceramic slurry to an outer peripheral surface of one end of the cell body.
A step of inserting one end of the cell body coated with the ceramic slurry into a cap-shaped ceramic molding for a sealing member, and a step of firing and externally fitting the sealing member to one end of the cell body. A method for producing a solid oxide fuel cell unit, comprising: 3. A process in which a cell body forms a cylindrical air electrode calcined body, a step in which a solid electrolyte molded body is laminated on the surface of the air electrode calcined body and calcined, Polishing the surface of the fired body to expose a part of the air electrode calcined body, and laminating a current collector compact on the surface of the solid electrolyte calcined body and the air electrode calcined body; 3. The method for producing a solid oxide fuel cell according to claim 2, comprising a step of firing the laminated molded body.