JP3339998B2 - Cylindrical fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylindrical fuel cell, and more particularly to a solid electrolyte fuel cell having an intermediate layer formed between a solid electrolyte and a current collector.

[0002]

2. Description of the Related Art Conventionally, a solid oxide fuel cell has a high power generation efficiency because its operating temperature is as high as 1000 to 1050 ° C., and is expected as a third generation power generation system.

[0003] In general, a solid oxide fuel cell is known to be a cylindrical type or a flat type. 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 seals and non-uniformity of the temperature distribution in the cell in practical use. On the other hand, the cylindrical fuel cell has the features that the output density is low, but the mechanical strength of the cell is high and the temperature uniformity in the cell can be maintained. Both types of solid oxide fuel cells are being actively researched and developed utilizing their respective features.

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 a LaMnO ₃ -based material thereon. 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 (inter-connector) 5.

In such fuel cell power generation, each unit cell is maintained at a temperature of 1000 to 1050 ° C., and air (oxygen) 6 is supplied to the inside of the support tube 1 and fuel (hydrogen) 7 is supplied to the outside. It is performed by

In recent years, in order to simplify the process in the cell fabrication process, LaMnO, which is an air electrode material, has been used.
Attempts to use _3-based material as a direct porous support tube have been made. As a support tube material having the function as an air electrode, La is 20 at% by Ca or 10 to 10 at Sr.
A LaMnO ₃ solid solution material substituted with 15 atomic% is used.

Such a cylindrical fuel cell is formed by, for example, molding a solid electrolyte powder into a cylindrical shape by extrusion molding or the like.
It is manufactured by a method of forming a cylindrical sintered body by firing, forming an air electrode layer or a fuel electrode layer on the inner peripheral surface or outer peripheral surface of the sintered body by a slurry coating method or the like, or firing, or An air electrode layer, a solid electrolyte layer, and a fuel electrode layer are formed on the surface of a cylindrical sintered body obtained by firing a ceramic porous support tube by a slurry coating method, an electrochemical deposition method (EVD method), a plasma spraying method, or the like. It is manufactured by a method of sequentially forming.

On the other hand, the present inventors provide a method of manufacturing a cylindrical fuel cell comprising at least an air electrode and a solid electrolyte on the surface of an electrically insulating cylindrical substrate,
A step of preparing a molded body for a cylindrical substrate from an electrically insulating powder; a step of producing a molded sheet for each of a powder for forming an air electrode and a powder for forming a solid electrolyte; Manufacturing a cylindrical fuel cell, comprising: winding a sheet-like molded body for an air electrode and a solid electrolyte for lamination to form a cylindrical laminate; and simultaneously firing the cylindrical laminate. The method was previously filed (Japanese Patent Application No. 6-73025). According to this method, fuel cells can be manufactured with a very simple process and with a small number of steps with a high yield. The above-mentioned application also discloses a technique of sequentially winding and laminating green sheets of an electrolyte material and a current collector material on the surface of the air electrode molded body and simultaneously firing (hereinafter sometimes referred to as co-sintering). did.

[0009]

In the above-described cell production by co-sintering, there is a feature that the process is simple and the fuel cell can be produced with a small number of steps with a high yield. However, the solid electrolyte layer and the current collector Due to the low chemical reactivity between the layers, the bonding was poor, gas leaks were likely to occur, the output was reduced during long-term power generation, or the cylindrical fuel cell could be damaged during power generation.

[0010]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventors have found that a solid electrolyte layer and a current collector layer in a fuel cell are formed of Y, a rare earth element and an alkaline earth metal. By joining at least one of them through the intermediate layer of the composite oxide containing Zr, the solid electrolyte layer and the current collector layer can be firmly joined, preventing gas leakage and high output. Thus, the present inventors have found that a cylindrical fuel cell having long-term stability can be produced by using the method described above, and have reached the present invention.

The cylindrical fuel cell of the present invention is formed on the outer surface of a fuel cell body in which a fuel electrode is formed on one surface of a cylindrical solid electrolyte and the air electrode is formed on the other surface, and on the inner surface of the solid electrolyte. A current collector electrically connected to the fuel electrode or the air electrode is provided, at least the solid electrolyte,
In the cylindrical fuel cell unit obtained by co-firing the current collector, a part of the solid electrolyte is provided with a cutout part, and a part of the fuel electrode or the air electrode is formed on the inner surface of the solid electrolyte. And the exposed surface and the end face of the solid electrolyte in the vicinity of the cutout are covered with the current collector. Further, between the solid electrolyte and the current collector, Y, a rare earth element and an alkaline earth are provided. An intermediate layer having a thickness of 0.05 to 100 [mu] m is formed of a composite oxide containing at least one selected from a class of metals and Zr.

[0012]

According to the present invention, in the fuel cell unit, the solid electrolyte layer and the current collector layer are connected via an intermediate layer of a composite oxide containing Zr and at least one of Y, rare earth element and alkaline earth metal. By joining, the fuel cell can be firmly joined. As a result, gas leakage is prevented, and a fuel cell having high output and long-term stability can be manufactured.

The intermediate layer is made of a composite oxide comprising at least one of Y, a rare earth element and an alkaline earth metal and Zr, or a composite oxide comprising at least one of Y, a rare earth element and an alkaline earth metal and Zr. May be a solid solution of the composite oxide.

Another major feature of the present invention is that a green sheet of an air electrode material, a solid electrolyte material, and a current collector material is sequentially wound and laminated on a calcined body formed of a ceramic porous support tube. Alternatively, in a step of sequentially winding and laminating a green sheet of a solid electrolyte material and a current collector material on an air electrode molded body functioning as a support tube, an intermediate is formed on the surface of the solid electrolyte by a slurry dipping method or a printing method. An intermediate layer can be formed by applying the above-mentioned material for forming a layer and co-sintering, and does not require a large process change. This is a great feature from an industrial point of view.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. As shown in FIGS. 1 and 2, the cylindrical fuel cell of the present invention has an air electrode 32 formed on an inner surface of a cylindrical solid electrolyte 31 and a fuel electrode 33 formed on an outer surface thereof to form a fuel cell main body 34. A current collector 35 electrically connected to the air electrode 32 is provided on the outer surface of the fuel cell main body 34. That is, the notch 36 is formed in a part of the solid electrolyte 31, and the air electrode 3 formed on the inner surface of the solid electrolyte 31 is formed.
2 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. An intermediate layer 38 is formed between the end surface of the solid electrolyte 31 and the current collector 35.
The cylindrical fuel cell of the present invention may be formed by forming a porous support tube, and sequentially stacking the air electrode 32, the solid electrolyte 31, and the fuel electrode 33 on the outer surface of the porous support tube.

Current collector 35 electrically connected to air electrode 32
Are formed on the outer surface of the fuel cell main body 34 so as to cover the continuous same surface 39 with no step, and the fuel electrode 3
3 is not electrically continuous. The continuous same plane 39 is
A part of the air electrode 32 formed on the inner surface of the solid electrolyte 31 is exposed, and the end surface 41 of the solid electrolyte 31 and the exposed surface 37 of the air electrode 32 are continuously connected to the same surface (the end surface 41 of the solid electrolyte 31 and the air surface). The exposed surface 37 of the pole 32 is a flat state without any step. The continuous same surface 39 is formed by polishing the outer peripheral surface of the cell body until a part of the solid electrolyte molded body and a part of the air electrode molded body become the same continuous surface.

The intermediate layer 38 of the present invention is made of a composite oxide containing at least one selected from Y, rare earth elements and alkaline earth metals and Zr. As rare earth elements, Sc, La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, and Lu. Among them, from an economic point of view,
La, Y, Yb and Nd are particularly preferred.

As the alkaline earth metal, Be, Mg,
There are Ca, Sr, Ba, Ra and the like.

Examples of the composite oxide containing Zr and at least one selected from the group consisting of Y, a rare earth element and an alkaline earth metal include La ₂ Zr ₂ O ₇ and Y ₂ Zr _2.
O ₇ , Yb ₂ Zr ₂ O ₇ , Nd ₂ Zr ₂ O ₇ , CaZr
O ₃ , SrZrO _{3 and the} like.

A solid solution of a composite oxide comprising Zr and at least one of Y, a rare earth element and an alkaline earth metal may be used. Such solid solutions include (Y, L
a) Zr ₂ O _{7 and the} like.

The intermediate layer 38 is an electrically insulating material or a material having a considerably small electric conductivity. If the intermediate layer 38 has a large electric conductivity, a leakage current from the solid electrolyte 31 to the current collector 35 occurs, causing a decrease in output.
For this reason, the intermediate layer is an electrically insulating material or a material that is close to the insulating material, and has a solid electrolyte 31 and a current collector 35.
Must be joined firmly to prevent gas leakage.

In the fuel cell of the present invention, for example, 3 to 20 mol% of Y ₂ O ₃ or Y
Partially stabilized or stabilized ZrO ₂ containing b ₂ O ₃
Is used. The air electrode 32 is mainly L
LaMnO in which a is substituted with 10 to 30 atomic% of Ca and Sr
_As the fuel electrode 33, a ZrO ₂ (Y ₂ O ₃ ) cermet containing 50 to 80% by weight of Ni is used. Also,
As the current collector 35, La is mainly composed of 10 to 20 atomic% of Ca or Sr, or Cr is composed of 10 to 30 atomic% of Mg.
LaCrO ₃ substituted in is used.

In the method for manufacturing a cylindrical fuel cell according to the present invention, a sheet formed body of a solid electrolyte is wound around an outer surface of an air electrode formed body and laminated, and the resulting structure is oxidized in an oxidizing atmosphere.
Calcined at a temperature of 0 to 1300 ° C. for about 1 to 3 hours,
The surface of the solid electrolyte calcined body to be the lamination point 5 is polished so that a part of the solid electrolyte calcined body and a part of the air electrode calcined body are substantially continuous on the same plane.

An intermediate layer of a composite oxide containing Zr and at least one selected from the group consisting of Y, a rare earth element and an alkaline earth metal is provided on an end face 41 of the calcined solid electrolyte body on which the current collector 35 is laminated. A molded body is formed, and a sheet-like molded body of a current collector is laminated on the exposed surface of the air electrode molded body and the surface of the intermediate layer molded body. It is desirable to increase the amount of polishing of the end face 41 of the calcined solid electrolyte body in advance so that the surface of the intermediate layer compact and the exposed surface of the cathode compact are continuous and the same plane (plane).

The method of forming the intermediate layer 38 is as follows.
For example, a slurry containing La ₂ Zr ₂ O ₇ , Y ₂ Zr ₂ O ₇ or the like may be applied and formed by direct firing, or a slurry containing Y ₂ O ₃ or Yb ₂ O ₃ may be applied. Then, this is reacted with LaCrO _{3 as} a current collector at a high temperature to deposit La, and then this La is reacted with Zr in the electrolyte to form a desired intermediate layer. From the viewpoint of suppressing gas leakage, the latter method is excellent because a denser intermediate layer is formed.

That is, in order to form the intermediate layer, La ₂ Zr ₂ O ₇ , Y is previously provided between the solid electrolyte and the green sheet of the current collector.
₂ Zr ₂ O ₇ , Yb ₂ Zr ₂ O ₇ , Nd ₂ Zr ₂ O ₇ ,
And the like, or a slurry containing a solid solution thereof is applied, and then treated at a high temperature to form an intermediate layer made of each composite oxide.

As a specific coating method, a slurry dipping method and a printing method are used.

As another method, La, Y, Y
oxides of b, Nd, Dy, Sc, for example, La ₂ O ₃ , Y
₂ O ₃ , Yb ₂ O ₃ , Nd ₂ O ₃ , Dy ₂ O ₃ , Sc ₂
A slurry containing O ₃ may be applied. Alternatively, a compound such as a carbonate, a bromate, or an acetate containing the above-described element which forms an oxide in a high-temperature oxidizing atmosphere may be applied. As described above, these elements such as Y and Yb replace La in the LaCrO ₃ crystal as a current collector and precipitate La at high temperatures, except for La, and this La reacts with Zr in the solid electrolyte. La ₂ Z between the solid electrolyte and the current collector
Form r ₂ O ₇ . On the other hand, La is directly
Reacts directly with La ₂ Zr ₂ O between the solid electrolyte and the current collector.
Form ₇ . In the latter method, the added La,
An oxide composed of Y and Yb may remain, but this does not pose any particular problem if the intermediate layer of the present invention is formed in a layered form. In some cases, a solid solution layer containing Y, Yb or the like is formed in La ₂ Zr ₂ O ₇ , but this is not a problem.

La ₂ Zr ₂ O ₇ , Y ₂ Zr ₂ O ₇ , Yb
_{2 Zr 2 O 7, Nd 2} Zr 2 if you previously applied a slurry of O ₇ or the like, the average particle diameter of the raw material powder is 0.1~10μ
m, and particularly preferably a size of 0.5 to 2 μm. If the average particle diameter of the powder is smaller than 0.1 μm, it is difficult to apply the powder uniformly due to a large agglomeration between the powders. On the other hand, if the average particle diameter of the powder exceeds 10 μm, the sinterability deteriorates, and
Cracks are likely to occur.

When an oxide such as La, Y, Yb or a compound thereof is applied, the average particle diameter of the powder is 0.1 to 2
A size of 0 μm, especially 0.5 to 5 μm is good. If the average particle diameter of the powder is smaller than 0.1 μm, it is difficult to apply the powder uniformly due to large agglomeration of the powder. Conversely, if the thickness exceeds 20 μm, the substitution reaction between the applied element and La becomes small and the formation of the intermediate layer becomes insufficient, and gas leakage easily occurs.

The thickness of the intermediate layer, such as La ₂ Zr ₂ O _7, is about 0.3.
It is most preferably from 0.5 to 100 μm, particularly preferably from 1 to 50 μm. If the thickness of the intermediate layer is less than 0.05 μm, the effect of suppressing gas leakage is small, and if it exceeds 100 μm, cracks tend to occur in the intermediate layer due to differences in the thermal expansion coefficients of the electrolyte, the current collector and the intermediate layer. And gas leaks are likely to occur.

The air electrode / solid electrolyte / current collector laminate thus manufactured is placed in an oxidizing atmosphere such as the air at 130.degree.
By sintering by simultaneous firing at a temperature of 0 to 1700 ° C. for about 1 to 15 hours, a cylindrical fuel cell of the present invention is obtained.

The surface on which the current collector is formed preferably has no step between the end surface 41 of the solid electrolyte and the exposed surface 37 of the air electrode 32. For example, the continuous same surface 39 is a curved surface. Is also good. Further, without polishing, the end face 41 of the solid electrolyte
The present invention is effective even when a step is generated between the current collector and the exposed surface 37 of the air electrode 32, but it is desirable that there be no step from the viewpoint of improving the joining strength of the current collector.

Further, the cylindrical fuel cell of the present invention may be any one that joins a portion where a solid electrolyte and a current collector are conventionally contacted and joined via an intermediate layer of the present invention. It may be manufactured by any method.

[0035]

【Example】

Example 1 La ₂ O ₃ , MnO ₂ , C
The aCO ₃ powder was weighed and mixed to obtain La _0.85 Ca _0.15 MnO ₃ and then calcined at 1500 ° C. (La, C
a) MnO ₃ powder was obtained. Thereafter, this was pulverized to produce a powder having an average particle diameter of 6 μm. In addition, a coprecipitated ZrO ₂ powder containing 10 mol% of Y ₂ O ₃ having an average particle diameter of 0.5 μm was prepared as a powder for forming a solid electrolyte. Further, NiO powder and ZrO ₂ (containing Y ₂ O ₃ ) powder as the powder for forming the fuel electrode are in a weight ratio of 80:20.
The compound powder composed of La _0.8 Ca _0.21 CrO ₃ having an average particle diameter of 1 μm was prepared as a powder for forming a current collector by mixing the powders in the ratio described above.

First, the 6 μm (La, Ca) Mn
A slurry was prepared from O ₃ powder using water as a solvent, and the slurry was used to form an inner diameter of 13 mm and an outer diameter of 1 using an extrusion molding apparatus.
A 6 mm cylindrical air electrode molding was obtained. On the other hand, as for the solid electrolyte, a slurry was prepared from the above Y ₂ O ₃ stabilized ZrO ₂ powder using water as a solvent, and a slurry was formed into a 150 μm thick sheet by a doctor blade method.
For the fuel electrode, the above NiO powder and ZrO ₂ (Y ₂ O ₃
Similarly, a slurry is prepared from the powder using water as a solvent,
This was formed into a sheet-like molded body having a thickness of 100 μm by a doctor blade method.

Then, an electrolyte sheet is wound around the surface of the cylindrical air electrode molded body via an adhesive made of acrylic resin to form an intermediate layer on the exposed surface of the air electrode and the surface of the electrolyte sheet. Then, a current collector sheet and a fuel electrode sheet were sequentially wound to form a cylindrical laminate as shown in FIG. In the intermediate layer between the electrolyte sheet and the current collector sheet, a composite oxide powder having an average particle diameter of 0.6 to 2.5 μm, which becomes the composite oxide shown in Table 1, having a thickness of 1 to 95 μm. It was applied by screen printing. Thereafter, the cylindrical laminate was fired in the air at 1500 ° C. for 5 hours to produce a cylindrical cell as shown in FIG.

The permeation rate of He at 25 ° C. was measured using a commercially available He leak tester for the produced cell. In addition, oxygen was supplied to the inside of the cylindrical cell and hydrogen was supplied to the outside, and power was generated at 1000 ° C. every 1000 hours for 4000 hours to measure the output density.

The type of the intermediate layer was identified by X-ray diffraction, and the thickness of the intermediate layer was measured by a scanning electron microscope.
Table 1 shows the results.

[0040]

[Table 1]

From Table 1, it can be seen that Sample No. having no intermediate layer was formed. On the other hand, the samples of the present invention in which the intermediate layer was formed had a high output.

Example 2 According to Example 1, an electrolyte sheet, a current collector sheet, and a fuel electrode sheet were sequentially wound around the surface of a cylindrical molded body made of an air electrode material to produce a cylindrical laminated body. Thereafter, the resultant was fired at 1550 ° C. for 3 hours to produce a battery cell as shown in FIG.
At this time, an oxide or carbonate powder having an average particle diameter of 0.6 to 1.3 [mu] m shown in Table 2 having a thickness of 0.1 to 90 [mu] m is provided between the electrolyte sheet and the current collector sheet. Was applied. For the fabricated cell, the transmission rate of He was measured in the same manner as in Example 1. In addition, oxygen was supplied to the inside of the cylindrical cell, and hydrogen was supplied to the outside thereof, and power was generated at 1000 ° C. for 1000 hours to measure the output density. The type of the intermediate layer was identified by X-ray diffraction. Table 2 shows the results.

[0043]

[Table 2]

From Table 2, it can be seen that Table 1 having no intermediate layer was formed.
Sample No. On the other hand, the samples in which the intermediate layer was formed had a high output with respect to 1.

[0045]

According to the cylindrical fuel cell of the present invention, the solid electrolyte layer and the current collector layer are formed between a composite oxide containing Y, at least one of rare earth elements and alkaline earth metals and Zr. By joining through the layers, the fuel cell can be firmly joined. As a result, gas leakage is prevented, and a fuel cell having high output and long-term stability can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cylindrical fuel cell according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a perspective view of a conventional cylindrical fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 ... Solid electrolyte 32 ... Air electrode 33 ... Fuel electrode 34 ... Fuel cell main body 35 ... Current collector 36 ... Notch 37 ... Exposed surface 38 ... Middle Layer 39: continuous same plane 41: end face

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-309565 (JP, A) JP-A-7-130379 (JP, A) JP-A-7-111157 (JP, A) JP-A-7-130 282825 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/02 H01M 8/12

Claims (1)

(57) [Claims] 1. A fuel cell having a fuel electrode formed on one surface of a cylindrical solid electrolyte and an air electrode formed on the other surface, and a fuel electrode or an air electrode formed on an inner surface of the solid electrolyte. A current collector for electrical connection is provided, and at least the solid electrolyte and the cylindrical fuel cell obtained by simultaneously firing the current collector are provided with cutouts in a part of the solid electrolyte. A part of the fuel electrode or the air electrode formed on the inner surface of the solid electrolyte is exposed, and the exposed surface and the end face of the solid electrolyte near the notch are covered with the current collector, and Between a solid electrolyte and the current collector, a thickness of a composite oxide containing at least one selected from the group consisting of Y, a rare earth element and an alkaline earth metal and Zr and a thickness of 0.05 to 100 μm
Wherein the intermediate layer is formed.