JPH0758616B2 - Method for producing solid oxide fuel cell tube cell - Google Patents

Description

The present invention relates to a method for manufacturing a tube cell of a solid oxide fuel cell.

(Prior Art) As a method for producing a tube cell of a solid oxide fuel cell in which a fuel electrode layer and an air electrode layer sandwich an electrolyte layer to form a three-layer cylindrical tube, either a fuel electrode or an air electrode is used. The electrode is formed into a cylindrical shape by pressing or extrusion molding,
Powder slurry of each material constituting the electrolyte layer and other electrode layers is sequentially applied to the surface of the cylindrical material and dried and then fired, or a resin or wax having a low melting point is used as a core material and an air electrode (or A method is known in which materials for the fuel electrode), the electrolyte, and the fuel electrode (or air electrode) are sequentially applied and dried, and then the core material is melted and withdrawn, followed by firing as described above (see Japanese Patent Laid-Open No. 1-93065). .

(Problems to be Solved by the Invention) In the above conventional technique, since the constituent materials of the layers provided in superposition are sintered at one time, cracks easily occur and it is difficult to form a dense electrolyte layer.

In addition, the electrode also serving as the support tube forming the innermost layer is formed by pressing or extrusion molding, or is formed by coating the material forming the electrode on the core material made of a low melting point material, so that the surface condition can be controlled. Difficult to do, almost uniform surface condition.
That is, the pores formed in the electrode penetrate the surface side in contact with gas or air and the surface side in contact with the electrolyte with substantially the same pore diameter.

Therefore, when this electrode is formed in a relatively dense state as a whole, not only the intake of gas or air deteriorates because the pore size of the pores is small, but also the water generated by the reaction is not discharged smoothly and the pores are It may be blocked by water. On the other hand, if this electrode is formed into a relatively coarse state as a whole with the same porosity as the former, gas or air will be taken in better and reaction water will be discharged smoothly. The problem of reduced contact points at the interface, that is, contact points that react, may occur.

The present invention has been made in view of the above problems of the prior art, the object of which is a thin and dense electrolyte layer and air or gas inflow passage, the discharge of reaction water is smooth, and the electrode, the electrolyte, An object of the present invention is to provide a method for producing a solid oxide fuel cell tube cell, which has many contacts at the three-phase interface of the gas phase, can form an electrode also serving as a support tube with good diffusion of air or gas, and has a low production cost.

(Means for Solving the Problems) In order to achieve the above object, in the method for producing a tube cell of a solid oxide fuel cell according to the present invention, a slurry composed of a material forming either one of a fuel electrode and an air electrode. The step of forming a support tube-cum-electrode also forming the innermost layer by forming a porous cylindrical shape by slip casting, drying and firing, and forming an electrolyte on the outer surface of the support-tube-cum-electrode. A step of integrally depositing an electrolyte layer on the outer surface of the electrode also serving as a support tube by repeating the step of depositing and drying the slurry of the constituent material and firing the slurry, the slurry of the material forming the other electrode on the electrolyte layer The step of depositing, drying, and firing is repeated several times to form an electrode serving as the outermost layer.

In the present invention, a cermet of nickel oxide (NiO) and yttria-stabilized zirconia (YSZ) is used as the material of the fuel electrode, and strontium-doped lanthanum manganite (La _x Sr) which is a perovskite type oxide is used as the material of the air electrode. _1-x MnO ₃ ) is used.

In addition, yttria-stabilized zirconia (YSZ) is used as the material for the electrolyte.

The fuel electrode or the air electrode is made of a material having a relatively large particle size because it is required to be porous, and the electrolyte is made into a slurry by using a material having a small particle size because it is a thin and dense layer.

As an example, when the fuel electrode is also used as the electrode also serving as the support tube, the particle diameter and the sludge concentration of the general material of each layer are shown below.

When forming each layer, the electrode layer that also serves as the support tube is formed by slip casting, which is a wet forming method, and the electrolyte layer and other electrode layers are also formed by wet coating such as slurry coating, slurry spraying, and dipping. Unify the wet.

The electrode also serving as the support tube, which is formed into a porous cylindrical shape, may be either a fuel electrode or an air electrode, but in any case, it is desirable in terms of strength to have a wall thickness of about 2 mm.

In the case of firing, when the electrode also serving as a supporting tube is a fuel electrode, the maximum temperature is maintained at 1300 ° C to 1400 ° C for 1 to 5 hours, and when the electrode is an air electrode, it is maintained at 1400 ° C for 0.5 to 10 hours.

Repeating the steps of depositing and baking the electrolyte material slurry in forming the electrolyte layer allows the cracks, pinholes, etc., generated by baking to be blocked by the slurry adhesion in the next step. On the other hand, it is advantageous to improve the compactness, but excessive number of times increases the wall thickness of the layer, which increases the permeation resistance of oxygen ions and is disadvantageous in improving battery performance. However, when the slurry coating is performed by dipping, it is usually appropriate to perform the coating several times to a dozen times.

On the other hand, the deposition of the electrode material slurry in the formation of the electrode formed on the outer surface of the electrolyte layer and the repeating of the firing process are for giving the electrode a thickness. This step should be repeated several times in order to make the thickness about several hundreds of μm.

(Operation) According to the method of the present invention configured as described above, when the electrode also serving as the support tube is formed, when the slurry is injected into the gypsum mold, the water in the slurry is diffused and absorbed by the mold. The fine particles inside are released and adhere to the surface of the gypsum to form a film on the outermost side, but this film already has a different structure from the base material inside it and becomes a more dense structure to the base material. That is, in the electrode that also serves as the support tube, the relatively coarse tissue on the innermost side is formed continuously with the dense tissue on the outside in contact with the electrolyte, and the pores that open to the inside and extend to the outside are formed in a large number in the dense tissue portion on the outside. It diverges and opens dispersedly on the outer surface.

Therefore, the fuel or air flowing inside the electrode also serving as the support tube and flowing into the pores from the inner surface of the electrode flows out to the outer surface in a diffused state and contacts the electrolyte layer in a wide range.

Further, since the steps of firing each layer and applying the material slurry to the electrolyte layer and firing are repeated a plurality of times,
Even if cracks, pinholes, etc. occur due to firing in the preceding process, they can be filled and closed by the slurry adhesion in the next process.

Example 1 An example of the present invention will be described below with reference to FIGS. 1 to 3.

In this embodiment, the electrode 1 also serving as the support tube is a fuel electrode, and the other electrodes 2 are air electrodes. In the figure, 3 is an electrolyte layer.

First, a cermet of nickel oxide (NiO) and 8 mol yttria-stabilized zirconia (YSZ) was used as an electrode material to prepare a slurry, which was poured into a molding die made of gypsum, and a predetermined time for inking for 1 to 15 minutes. It was made to have a thickness of thickness, drained, discharged for 1 hour or more, and then demolded to form a porous cylindrical tube having a thickness of 2 mm. And the temperature rising rate of this porous cylindrical tube
The electrode 1 also serving as a supporting tube was prepared by firing under conditions of 120 ° C./h, maximum temperature of 1400 ° C., and maximum temperature holding time of 1 hour.

Incidentally, the slurry is 30 parts of NiO crushed to an average particle size of 1.0μ,
70 parts of YSZ granulated to 45.0μ with a spray dryer, water 9
Part, peptizer 0.5 part, put in MCN pot and knead for 20 hours, take out this into a beaker, add 0.3 part binder and 0.1 part antifoaming agent and evacuate for 30 minutes while stirring with a magnetic stirrer to adjust did.

Next, a slurry prepared with YSZ powder having a particle size of submicron and 10 ml of ethanol per 1 g of YSZ was applied to the outer surface of the electrode 1 also serving as the supporting tube by dipping, and the heating rate was 200 ° C./h and the maximum temperature was The operation of baking at 1400 ° C. and a maximum temperature holding time of 1 hour was repeated several times to form an electrolyte layer 3 having a thickness of 20 μ.

Finally, a slurry prepared by using lanthanum manganite (La _x Sr _1-x MnO ₃ ) doped with strontium, which is a perovskite type oxide, as an electrode material is formed on the outer surface of the electrode 1 also serving as the supporting tube to form an electrolyte layer 3 It is attached by dipping on top, and after drying the temperature rise rate is 120 ° C / h, maximum temperature is 1100.
The firing operation was carried out several times at a temperature of 3 ° C. and a maximum temperature retention time of 3 hours to form an electrode 2 having a thickness of 200 μ and form a tube cell.

In the tube cell manufactured as described above, the fuel electrode also serving as the support tube has an outer portion having a relatively dense structure with respect to an inner portion of a relatively coarse structure as shown in FIG. The structure is such that the pores (4) are branched into a large number in the above-mentioned relatively dense structure portion and are in contact with the electrolyte layer (3) and open to the outer surface.

Further, the electrolyte layer was not impaired in its denseness due to cracks and pinholes, and sufficient denseness was obtained.

(Example 2) In this example, the electrode 1 also serving as a support tube is an air electrode,
The other electrode 2 is a fuel electrode.

First, strontium-doped lanthanum manganite (La _x Sr _1-x MnO ₃ ) which is a perovskite type oxide was poured into a mold made of gypsum and the slurry prepared as an electrode material was poured into the mold for 1 to 15 minutes. Then, it was made to have a predetermined thickness and drained, and after being dried for several hours, it was demolded to form a porous cylindrical tube having a thickness of 2 mm. Then, this porous cylindrical tube was fired at a temperature rising rate of 120 ° C./h, a maximum temperature of 1400 ° C., and a maximum temperature holding time of 3 hours, to manufacture an electrode 1 also serving as a supporting tube.

Next, a slurry prepared with YSZ powder having a particle size of submicron and 10 ml of ethanol per 1 g of YSZ was attached by dipping to the outer surface of the electrode 1 which also serves as a supporting tube, and the temperature rising rate was 200 ° C./h and the maximum temperature was reached. 1100 ℃, maximum temperature holding time 1
The operation of baking for several hours was repeated several times to form an electrolyte layer 3 having a thickness of 20 μm.

Finally, a cermet of nickel oxide (NiO) and 8 mol yttria-stabilized zirconia (YSZ) was used as an electrode material to prepare a slurry, and this slurry was used as the above-mentioned support tube / electrode 1.
It is attached to the electrolyte layer 3 formed on the outer surface of the by dipping, and after drying, the heating rate is 120 ° C / h, the maximum temperature is 1100 ° C,
The operation of firing at the maximum temperature holding time of 1 hour was repeated several times to form the electrode 2 having a thickness of 200 μm and form a tube cell.

In the tube cell manufactured as described above, the air electrode which also serves as a support tube has an outer portion having a relatively dense tissue with respect to an inner portion of a relatively coarse tissue as shown in FIG. The structure is such that the pores (4) are branched into a large number in the above-mentioned relatively dense structure portion and are in contact with the electrolyte layer (3) and open to the outer surface.

Further, the electrolyte layer was not impaired in its denseness due to cracks and pinholes, and sufficient denseness was obtained.

(Effect) Since the present invention is configured as described above, the following effects can be obtained.

(1) Since the electrode that also serves as the support tube is formed by slip casting, the electrode has a relatively dense structure in the outermost portion in contact with the electrolyte layer with respect to the inner portion of the relatively coarse structure, and each pore has this relatively dense structure. In the outermost part having a different structure, by branching into a large number and opening in contact with the electrolyte layer, diffusion of fuel or air is improved, and electrodes, electrolytes,
Gas phase contacts increase. That is, the battery performance is improved by increasing the number of contacts that react.

Further, even though the surface in contact with the electrolyte layer is dense, the inner part has a rough structure, so that the fuel and air flowing in the tube cell can flow into the electrode well, and the reaction water can be discharged well.

(2) The firing of each layer is performed for each layer, and for the electrolyte layer that requires particularly high density, the work of depositing the slurry and the subsequent firing are repeated multiple times. It can be filled and closed by the slurry attachment work of (1) and the denseness can be improved. Therefore, it is also advantageous in thinning the layer.

(3) Since all the molding processes are unified in a wet process, the equipment cost is reduced and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a tube cell of a solid oxide fuel cell produced by the method of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is an enlarged sectional view of an essential part. 1: Electrode also used as support tube 2: Other electrode 3: Solid electrolyte layer

Claims (1)

[Claims] 1. A method for producing a tube cell of a solid oxide fuel cell, comprising a fuel electrode layer and an air electrode layer sandwiching an electrolyte layer to form a three-layered cylindrical shape, which comprises either a fuel electrode or an air electrode. A step of adjusting the slurry of the material that constitutes one of the electrodes, forming it into a porous cylindrical shape by slip casting, drying and firing to form an electrode that also serves as a support tube that forms the innermost layer, A step of integrally depositing an electrolyte layer on the outer surface of the electrode also serving as a support tube by repeating a step of adhering and drying a slurry of a material forming an electrolyte on the outer surface of the electrode also serving as a tube and firing the slurry a plurality of times. The step of depositing and drying the slurry of the material forming the other electrode on the top and repeating the firing as appropriate a plurality of times,
A method of manufacturing a tube cell of a solid oxide fuel cell, which comprises sequentially performing a step of forming an electrode to be an outermost layer.