JPH09277226A - Manufacture of solid electrolyte type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid electrolyte type fuel cell, with which the roughening of the surface of a solid electrolyte film can easily be performed at a low cost and the effective electrode area can be expanded and consequently the bonding power between poles can be enhanced. SOLUTION: In this manufacturing method of a solid electrolyte type fuel cell, a mixed slurry of a solid electrolyte material and a thermal decomposition substance is prepared so as to form the mixed slurry into a formed body in order to arrange the formed body as surface layers on the surface of a solid electrolyte ceramic formed body for lamination. By firing the resultant laminate in order to thermally decompose the thermal decomposition substance, a solid electrolyte ceramic with roughened surface 2 is produced. Further, after fuel poles or air poles are arranged and laminated to the surface of the solid electrolyte ceramic 2, the resultant laminate is further fired. The thickness of each of the surface layers 2a and 2b excluding the projecting part developed by the thermal decomposition substance are respectively 20-50μm. As the thermal decomposition substance, carbon can be employed under the condition that its particle diameter is two times or more as much as the thickness of each of the surface layers 2a and 2b of the solid electrolyte ceramic formed body and 100μm or less excluding the projecting part developed by the thermal decomposition substance.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a solid oxide fuel cell.

[0002]

2. Description of the Related Art In a solid oxide fuel cell, each layer of a fuel electrode, a solid electrolyte membrane, and an air electrode is arranged and laminated on each other to form three layers. Fuel gas is supplied and air is supplied to the air electrode to generate electricity. The air electrode may be referred to as an oxygen electrode and oxygen gas may be supplied thereto.

The solid electrolyte membrane can be obtained by using a material such as yttria-stabilized zirconia (YSZ) as a material to prepare a molded body by a tape casting method or the like, and firing the molded body. Then, for example, a mixture of nickel oxide and yttria-stabilized zirconia for the fuel electrode and a lanthanum manganite electrode material for the air electrode are applied and printed on the surface of the solid electrolyte membrane to form electrodes.

[0004]

The electrode reaction in this solid oxide fuel cell is considered to occur at the three-phase interface between the solid electrolyte, the electrode, and the gas phase, which improves the power generation performance of the solid oxide fuel cell. In order to do so, it is necessary to widen the area of the three-phase interface and to strengthen the bond between the solid electrolyte and the electrode.

However, since the surface of the conventional solid electrolyte membrane is flat, the bonding interface between this solid electrolyte membrane and the electrode formed on the surface becomes flat, and the solid interface between the electrode and the solid electrolyte membrane is strong. Joining was difficult.

Therefore, when such a solid oxide fuel cell is used for a long period of time, the bonding between the electrode and the solid electrolyte membrane deteriorates, the electrode is separated from the solid electrolyte membrane due to thermal shock, and the effective electrode area also decreases. However, there is a problem that the power generation characteristics are deteriorated.

Therefore, in order to solve the above-mentioned problems, various measures have been taken to increase the bonding force while increasing the effective electrode area by roughening the bonding interface between the electrode and the solid electrolyte membrane. .

That is, the surface of the solid electrolyte membrane is subjected to an etching treatment with an acid (Japanese Patent Laid-Open No. 3-147).
No. 268), sandblasting (Japanese Patent Application Laid-Open No. 3-95864), and plasma spraying (Japanese Patent Application Laid-Open No. 3-285266). It is intended to increase the effective electrode area by roughening the surface to increase the bonding force with the electrode.

However, in the case of etching treatment using an acid, not only the corrosion penetrates into the solid electrolyte membrane to reduce its strength, but also the treatment of waste liquid becomes a problem. In addition, sandblasting and plasma spraying require expensive equipment, which is a cost problem.

Therefore, an object of the present invention is to provide a method for manufacturing a solid oxide fuel cell, which can easily and inexpensively roughen the surface of a solid electrolyte membrane and widen the effective electrode area to enhance the bonding strength. It is in.

[0011]

According to a first aspect of the present invention, in a method for producing a solid oxide fuel cell, a mixed slurry of a solid electrolyte material and a pyrolysis substance is prepared, and the mixed slurry is molded, This molded body is disposed as a surface layer on the surface of a solid electrolyte ceramic molded body and laminated, and this is fired to thermally decompose the pyrolyzed substance to obtain a solid electrolyte ceramic having a roughened surface. To do.

According to a second aspect of the present invention, in the method for producing a solid oxide fuel cell, a mixed slurry of a solid electrolyte material and a pyrolyzed substance is prepared, the mixed slurry is molded, and the molded body is used as a surface layer to form a solid. The electrolyte ceramic molded body is disposed on the surface of the molded body and laminated, and the pyrolyzed substance is pyrolyzed by firing to form a solid electrolyte ceramic having a roughened surface, and a fuel is applied to the surface of the roughened solid electrolyte ceramic. It is characterized in that an electrode or an air electrode is arranged and laminated, and this laminated body is further fired.

Further, in claim 3, the surface layer has a thickness of 20 μm or more and 50 μm or more excluding the protrusions formed by the pyrolyzed substance.
It is characterized by the following.

Further, in claim 4, the thermally decomposing substance is carbon.

Further, in claim 5, the particle size of the pyrolyzed substance is at least twice as large as the thickness of the surface layer of the solid electrolyte ceramic molded body excluding protrusions by the pyrolyzed substance and 100 μm.
m or less.

By doing so, the surface of the solid electrolyte membrane can be roughened easily and inexpensively, and the effective electrode area can be widened. Therefore, the bonding force between the electrode and the solid electrolyte membrane can be increased to prevent the electrode from peeling off from the solid electrolyte membrane. In addition, by selecting the material of the pyrolyzed substance, by controlling the thickness of the surface layer to a certain range, and controlling the particle size of the pyrolyzed substance, the effective electrode area can be further expanded and the bonding force between the electrode and the solid electrolyte membrane It can be further enhanced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for manufacturing a solid oxide fuel cell according to the present invention will be described below.

Example 1 In this example, an ordinary solid electrolyte slurry and a mixed slurry of a solid electrolyte material and a spherical pyrolyzed substance were prepared, and a solid electrolyte having a surface layer containing the pyrolyzed substance was prepared. This is an example of producing a ceramic molded body and firing it to produce a solid electrolyte ceramic having a roughened surface.

First, a method for producing a solid electrolyte ceramic green sheet, which is a solid electrolyte ceramic molded body, will be described.

A predetermined amount of a binder (for example, polyvinyl butyral binder) and a solvent (ethanol and toluene) are added to and mixed with powdery yttria-stabilized zirconia, and the mixture is made into a slurry, which is then subjected to a doctor blade method. A solid electrolyte ceramic green sheet having a thickness of 50 to 60 μm was produced as a ceramic molded body.

On the other hand, a slurry of a solid electrolyte having the same composition as the above is prepared separately, and this slurry is used as a pyrolyzed substance.
A predetermined amount of spherical carbon having an average particle diameter of 100 μm is mixed and dispersed, and from this slurry, a doctor blade method is used.
As shown in the cross-sectional view of FIG. 1, a solid electrolyte ceramic green sheet 1b having a thickness of 40 μm excluding the convex portion t of the spherical carbon 1a protruding on the surface was produced.

Then, the thickness of 50 to 60 μm prepared above is prepared.
A solid electrolyte ceramic green sheet having a thickness of 40 μm excluding the convex portion of the spherical carbon as a surface layer on the solid electrolytic ceramic green sheet of (1) is superposed with the convex portion of the spherical carbon as an outer layer to form a pair. Two sets of solid electrolyte ceramic green sheet layers having a structure were prepared.

The two sets of solid electrolyte ceramic green sheet layers are arranged so that the surface layers containing spherical carbon are on the outside, and the thickness of the solid electrolyte between the two surface layers is about 400 μm. So that
Several additional solid electrolyte ceramic green sheets having a thickness of 50 to 60 μm and containing no spherical carbon were inserted and superposed.

The laminate of the solid electrolyte ceramic green sheets thus obtained was put in a plastic bag, the inside of the bag was evacuated, and the mixture was pressure-bonded using a warm isostatic press to obtain a solid. A laminated molded body of electrolyte ceramic was obtained.

Next, the solid electrolyte ceramic laminate was fired at 1400 ° C. (including the degreasing step) to obtain a solid electrolyte ceramic.

The cross section of the obtained solid electrolyte ceramic was observed with a scanning electron microscope (hereinafter referred to as SEM). As a result, as shown in FIG.
It is composed of surface layers 2a and 2b and a solid electrolyte layer 2c between them, and the surface thereof is roughened by forming concave portions 1c and 1d along the shape of spherical carbon thermally decomposed from the surface layers 2a and 2b during firing. It was However, no closed pores were found inside the solid electrolyte ceramic 2.

On the other hand, as a comparative example, a solid electrolyte ceramic was prepared in the same manner as in Example 1 except that spherical carbon having an average particle size of 30 μm was used as the pyrolyzed substance, and SE was prepared.
The cross section observed at M is shown in FIG.

In this case, the solid electrolyte ceramic 3 is composed of surface layers 3a and 3b and a solid electrolyte layer 3c between them, and the surface thereof has concave portions 4a and 4b due to spherical carbon thermally decomposed from the surface layers 3a and 3b during firing. Although formed and roughened, closed pores 4c were formed inside the surface layers 3a and 3b. Although not a closed pore, when the electrode paste was applied and printed on the surface of the solid electrolyte ceramic 3, a recess 4d in which the electrode paste was difficult to enter was generated.

(Example 2) In this example, a fuel electrode and an air electrode were arranged and laminated on both sides of a solid electrolyte ceramic having a roughened surface obtained in the same manner as in Example 1, respectively. It is an example of producing a solid oxide fuel cell by firing the laminate.

First, in the same manner as in Example 1, a solid electrolyte slurry in which spherical carbon is not mixed and a slurry in which a solid electrolyte material and spherical carbon having an average particle size of 100 μm are mixed are prepared, and these are molded respectively. A solid electrolyte ceramic compact having a surface layer containing the spherical carbon was obtained and fired to obtain a solid electrolyte ceramic having a roughened surface.

Next, in order to prepare a fuel electrode, a binder (for example, polyvinyl butyral binder) and a solvent (ethanol and toluene) are added in a predetermined amount to a mixture of powdered nickel oxide and yttria-stabilized zirconia. It was made into a slurry. Then, on one surface of the solid electrolyte ceramic, the nickel-prepared as a fuel electrode
A zirconia cermet-based slurry was applied by screen printing and then fired at 1400 ° C. to form a fuel electrode.

Subsequently, in order to produce an air electrode, a binder (for example, polyvinyl butyral binder) and a predetermined amount of solvent (ethanol and toluene) were added to powdered lanthanum manganite to form a slurry. Then, the lanthanum manganite-based slurry prepared as an air electrode was similarly applied by screen printing to the other surface of the solid electrolyte ceramic having the fuel electrode formed on its one surface in advance, and this was baked at 1200 ° C. To form an air electrode to obtain a solid electrolyte fuel cell comprising a three-layer film including a fuel electrode, a solid electrolyte membrane and an air electrode.

FIG. 4 shows this solid oxide fuel cell SE
The cross section observed by M is shown.

As can be seen from the above, in the solid oxide fuel cell 5, the solid electrolyte ceramic 6 is the surface layer 6a,
6b and a solid electrolyte layer 6c in between, and a fuel electrode 8 was formed on one surface along a recess 7a formed by spherical carbon pyrolyzed from the surface layer 6a. Further, on the other surface of the solid electrolyte ceramic 6,
The air electrode 9 was formed along the concave portion 7b formed by the spherical carbon thermally decomposed from the surface layer 6b. The recesses 7a and 7b on the surface of the roughened solid electrolyte ceramic 6 have little variation in shape and size, and the electrodes of the fuel electrode 8 and the air electrode 9 and the solid electrolyte ceramic 6 are
It was bonded with a stable rough surface as an interface.

For comparison, the solid electrolyte fuel cell thus produced was subjected to the same electrode material and method as in Example 2 on a solid electrolyte membrane whose surface was not roughened as in the conventional case. A fuel cell and an air electrode were formed to prepare a three-layer membrane solid oxide fuel cell, which was connected together with the solid oxide fuel cell obtained in Example 2 as shown in FIG. It was measured.

In FIG. 5, 5 is a solid oxide fuel cell, 6d is a solid electrolyte membrane, 8 is a fuel electrode, and 9 is an air electrode. 11 is a fuel gas supply pipe, 12 is an air supply pipe,
13 is a platinum wire, 14 is a variable resistor, 15 is an oscilloscope, 16 is an ammeter, and 17 is a mercury switch.

Then, the solid oxide fuel cell 5 is set to 100
Fuel gas and air are supplied to the fuel electrode 8 and the air electrode 9 respectively through the fuel gas supply pipe 11 and the air supply pipe 12 while maintaining the temperature at 0 ° C., and the electrode reaction is caused to occur through the solid electrolyte membrane 6d. It was Then, while observing with the ammeter 16, the voltage drop due to the polarization of the fuel electrode 8 and the air electrode 9 in the state where the current of 300 mA / cm ² flows was measured with the oscilloscope 15 by the current interrupt method.
Table 1 shows the measurement results.

[0038]

[Table 1]

Next, the measurement results will be considered. The smaller the value of the voltage drop due to the polarization, the wider the effective area of the electrode and the better the performance as a fuel cell. Table 1 shows that the example product has a smaller value of voltage drop due to polarization than the comparative example product. Therefore, it is understood that the example product has a larger effective electrode area than the comparative example product.

Then, regarding the comparative example product and the example product,
When the interface between the fuel electrode and the solid electrolyte membrane was observed by SEM, the comparative example product showed considerable shrinkage of the fuel electrode, and peeling occurred partially at the interface with the solid electrolyte membrane.

On the other hand, in the products of Examples of the present invention, neither shrinkage of the fuel electrode nor peeling at the interface with the solid electrolyte membrane was observed. It is considered that this is because the unevenness due to the roughening of the surface of the solid electrolyte membrane acts to suppress the contraction in the interface direction between the solid electrolyte membrane and the fuel electrode due to the operation in the high temperature reducing atmosphere.

Further, the air electrode had better bondability than that of the comparative example.

The surface layer of the solid electrolyte ceramic molded body of the present invention has a thickness of 20 excluding the protrusions due to the pyrolyzed substance.
If it is less than μm, it becomes too thin and difficult to handle.
On the other hand, the thickness of the surface layer excluding the protrusions due to the pyrolyzed substance is 50
When the thickness exceeds μm, when the unevenness is formed by combining with the pyrolyzed substance, the effect of increasing the bonding force by roughening the surface of the solid electrolyte membrane to widen the effective electrode area becomes small. Therefore, the surface layer has a thickness of 20μ excluding the protrusions due to pyrolyzed substances.
It is preferably at least m and at most 50 μm.

Further, it is preferable to use carbon as the pyrolytic substance, and most preferable to use spherical carbon, but other than that, for example, cellulose, polystyrene, polyethylene may be used, and the solid electrolyte may be used in accordance with the sintering of the solid electrolyte. Any material can be used as long as it is a material that can be thermally decomposed from the membrane surface to form irregularities on the surface of the solid electrolyte membrane to roughen the surface.

If the particle size of the pyrolyzed substance is less than twice the thickness of the surface layer of the solid electrolyte ceramic molded body excluding the protrusions by the pyrolyzed substance, the opening of the recess formed by the pyrolyzed substance is opened. The part becomes narrower than the inside, the opening part of the recess collapses, and the unevenness becomes uneven. Therefore, when the electrode slurry is applied and printed,
It becomes impossible to sufficiently form electrodes along the uneven surface. In addition, closed pores may occur, affecting the power generation characteristics. On the other hand, when the particle size of the pyrolyzed substance exceeds 100 μm, the effect of increasing the effective electrode area and increasing the bonding force with the electrode due to the condition of limiting the thickness of the surface layer of the solid electrolyte membrane excluding the protrusion due to the pyrolyzed substance Does not work to form a rough surface. Therefore, the particle size of the pyrolyzed substance is preferably not less than twice the thickness of the surface layer of the solid electrolyte ceramic molded body excluding the protrusions due to the pyrolyzed substance and 100 μm or less.

[0046]

EFFECTS OF THE INVENTION According to the present invention, in a solid oxide fuel cell, it is possible to easily and inexpensively roughen the interface at which the solid electrolyte membrane and the electrode contact each other, and the interface between the solid electrolyte membrane and the electrode is easily formed. The effective electrode area can be increased to enhance the bonding force.

Therefore, by roughening the interface in this way, it is possible to prevent the fuel electrode made of nickel-zirconia cermet from shrinking toward the interface due to the operation in the high temperature reducing atmosphere. The improvement of the power generation characteristics of the electrolyte fuel cell is achieved.

[Brief description of drawings]

FIG. 1 shows an example of the present invention in which the average particle size is 10
FIG. 3 is a cross-sectional view of a solid electrolyte ceramic green sheet with 0 μm spherical carbon protruding on the surface.

FIG. 2 shows an example of the present invention in which the average particle size is 10
FIG. 3 is a cross-sectional view of a solid electrolyte ceramic whose surface is roughened by using 0 μm spherical carbon.

FIG. 3 is a cross-sectional view of a solid electrolyte ceramic of Comparative Example whose surface is roughened using spherical carbon having an average particle diameter of 30 μm.

FIG. 4 shows an embodiment of the present invention and is a cross-sectional view of a three-layer membrane of a solid oxide fuel cell having a laminated interface in which an electrode and a solid electrolyte membrane are roughened.

FIG. 5 is a connection diagram for measuring power generation characteristics of a solid oxide fuel cell.

[Explanation of symbols]

2,3,6 Solid electrolyte ceramics 2a, 2b, 3a, 3b, 6a, 6b Surface layer 5 Solid electrolyte fuel cell 8 Fuel electrode 9 Air electrode t Convex part

Claims (5)

[Claims] 1. A mixed slurry of a solid electrolyte material and a pyrolyzed substance is prepared, the mixed slurry is molded, and the molded body is placed as a surface layer on the surface of the solid electrolyte ceramic molded body and laminated. A method for producing a solid oxide fuel cell, which comprises firing to thermally decompose the pyrolyzed substance to obtain a solid electrolyte ceramic having a roughened surface. 2. A mixed slurry of a solid electrolyte material and a pyrolyzed substance is prepared, the mixed slurry is molded, and the molded body is placed as a surface layer on the surface of the solid electrolyte ceramic molded body and laminated. The pyrolyzed material is pyrolyzed by pyrolysis to obtain a solid electrolyte ceramic having a roughened surface, and a fuel electrode or an air electrode is disposed on the surface of the roughened solid electrolyte ceramic and laminated, and this laminated body is formed. A method for producing a solid oxide fuel cell, which is characterized by further firing. 3. The method for producing a solid oxide fuel cell according to claim 1, wherein the surface layer has a thickness of 20 μm or more and 50 μm or less excluding protrusions due to a pyrolyzed substance. 4. The method for producing a solid oxide fuel cell according to claim 1, wherein the pyrolytic substance is carbon. 5. The particle size of the pyrolyzed material is not less than twice the thickness of the surface layer of the solid electrolyte ceramic molded body excluding the projections of the pyrolyzed material and not more than 100 μm. 1. A method for manufacturing a solid oxide fuel cell.