JPH0456070A - Manufacture of solid electrolytic fuel battery tube cell - Google Patents

Abstract

PURPOSE:To form a thin and minute electrolyte layer, and make flowing and passing of the air or the gas and exhaust of the reaction water smooth, and make a manufacture cost low by forming an electrode, which also works as a supporting tube, with slip casting, and performing firing of each layer per each layer, and unifying all forming processes with wet process. CONSTITUTION:An electrode 1, which also works as a supporting tube, is formed by slip casting. Next, a process for adhering the slurry of the material, for forming the electrolyte, on the outside surface of the electrode 1 and for drying and for firing is repeated several times to form an electrolyte layer 3 integrally with the electrode 1. A process for adhering the slurry of the material, for forming the other electrode, on the electrolyte layer 3 and for drying and for firing is repeated several times to form an electrode 2. The fuel electrode 1, which also works as a supporting tube, has an outside part having the relatively minute system, and each pore 4 is divided into multiple number at the described part having the relatively minute system to contact to the electrolyte layer 3 respectibvely, and is opened in the outside surface. Sufficient minute property of the electolyte layer 3 can be obtained without hindering the minute property with cracks and pin holes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a tube cell for a solid oxide fuel cell.

(Prior Art) As a method for manufacturing a tube cell of a solid oxide fuel cell, which is formed into a three-layer cylindrical structure by sandwiching an electrolyte layer between a fuel electrode layer and an air electrode layer, it is possible to The electrode is formed into a cylindrical shape by pressing or extrusion,
Powder slurries of the respective materials constituting the electrolyte layer and other electrode layers are sequentially applied to the surface of the cylindrical object and baked after drying, or an air electrode (or A known method is to sequentially apply and dry a material that will become a fuel electrode), an electrolyte, and a fuel electrode (or air electrode), then melt and extract the core material, and then sinter it in the same manner as above (see Japanese Patent Application Laid-Open No. 1-93065). .

(Problems to be Solved by the Invention) In the above-mentioned conventional technology, since the constituent materials of each layer provided overlapping each other are sintered at once, cracks are likely to occur and it is difficult to form a dense electrolyte layer.

In addition, since the electrode that also serves as a support tube and constitutes the innermost layer is formed by pressing or extrusion molding, or by coating the electrode material on a core material made of a low melting point material, it is possible to control the surface condition. This is difficult to do and results in a fairly uniform surface.

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 approximately the same pore diameter.

Therefore, when this electrode is formed in a relatively dense state as a whole, the pores have a small diameter, which not only makes it difficult to take in gas or air, but also prevents smooth discharge of water generated by the reaction, making the pores too small. It may also be blocked by water. On the other hand, if this electrode is molded in a relatively coarse state as a whole with the same porosity as the former, gas or air can be taken in well and reaction water can be discharged smoothly. A problem may arise in that the number of interfacial contacts, ie, the number of reactive contacts, is reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and aims to provide a thin and dense electrolyte layer, smooth inflow and passage of air or gas, and smooth discharge of reaction water. It is an object of the present invention to provide a method for manufacturing a solid electrolyte fuel cell tube cell, which can form a supporting tube-cum-electrode that has many contact points at the three-phase interface of the gas phase, allows good diffusion of air or gas, and has a low manufacturing cost.

(Means for Solving the Problems) In order to achieve the above object, in the method for manufacturing a tube cell of a solid oxide fuel cell of the present invention, a slurry made of a material constituting either the fuel electrode or the air electrode is used. A process of preparing an electrode that also serves as a support tube and forming the innermost layer by forming it into a porous cylindrical shape by slip casting, drying it, and firing it to form an electrode that also serves as a support tube and forming the innermost layer. A step of repeating the process of depositing, drying and firing a slurry of the constituent material several times to integrally form an electrolyte layer on the outer surface of the electrode that also serves as a support tube, and a slurry of the material constituting the other electrode on the electrolyte layer. The process of depositing, drying, and firing the electrode is repeated several times to form an electrode that will become the outermost layer.

In the present invention, the material for the fuel electrode is nickel oxide (
Nip) and yttria-stabilized zirconia (YS4) cermet are used, and lanthanum manganite (Lat 5T1-r M++0+) doped with strontium, which is a perovskite type oxide, is used as the material for the air electrode.

Furthermore, itria-stabilized zirconia (YS2) is used as the material for the electrolyte.

The fuel electrode and the air electrode are made of porous materials and are made of materials with relatively large particle diameters, and the electrolyte is made of materials with small particle diameters that are made into a thin, dense layer.

As an example, when the fuel electrode is used as an electrode that also serves as a support tube, the particle size and slurry concentration of general materials for each layer are shown below.

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

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

Further, during firing, when the support tube/electrode is a fuel electrode, the maximum temperature is maintained at 1300° C. to 1400° C. for 1 to 5 hours, and in the case of an air electrode, it is maintained at 1400° C. for 0.5 hours to 10 hours.

Repeating the deposition of electrolyte material slurry and firing process in forming the electrolyte layer can close cracks, pinholes, etc. that occur during firing by the slurry deposition in the next process, so the greater the number of repetitions, the more difficult it is to form the electrolyte layer. While it is advantageous for improving the density, too many times increases the thickness of the layer and increases the permeation resistance of oxygen ions, which is disadvantageous in improving battery performance. However, when applying the slurry by dipping, it is usually appropriate to apply the slurry several to ten times.

On the other hand, when forming the electrode on the outer surface of the electrolyte layer, the deposition of the electrode material slurry and the repetition of the firing process are intended to give the electrode a thickness, and when the slurry is deposited by dipping, the electrode layer This process should be repeated several times in order to obtain a thickness of approximately several hundred μm.

(Function) According to the method of the present invention configured as described above, when slurry is poured into a plaster mold when forming an electrode that also serves as a support tube, water in the slurry is diffused and absorbed into the mold. The fine particles in the slurry are liberated and adhere to the gypsum surface, forming a film on the outermost side, but this film already has a different structure from the inner substrate, and becomes even denser than the substrate. In other words, the electrode that also serves as a support tube has a continuous structure from a relatively coarse structure on the innermost side to a dense structure on the outside that is in contact with the electrolyte, and the dense structure on the outside has many pores that open inward and extend outward. Branched and open in a distributed manner on the outer surface.

Therefore, the fuel or air flowing inside the support tube-cum-electrode and flowing into the pores from the inner surface of the electrode flows out to the outer surface in a diffused state and comes into contact with the electrolyte layer over a wide range.

In addition, each layer is fired, and for the electrolyte layer, the process of applying material slurry and firing is repeated multiple times.
Even if cracks, pinholes, etc. occur due to the firing in the preceding step, they can be filled and closed by the slurry adhesion in the next step.

(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 which also serves as a support tube is a fuel electrode, and the other electrode 2 is an air electrode. Note that 3 in the figure is an electrolyte layer.

First, a slurry is prepared using a cermet of nickel oxide (NiO) and 8 molythria-stabilized zirconia (YS2) as electrode materials, and the slurry is poured into a mold made of plaster, and the predetermined thickness is achieved in 1 to 15 minutes. Thicken the wall, remove mud, and remove the mold after drying for over 1 hour to create a wall thickness of 2m+.
A porous cylindrical tube was molded. Then, the temperature of this porous cylindrical tube was increased at a rate of 120°C/h.

The support tube-cum-electrode 1 was produced by firing at a maximum temperature of 14° C. and a maximum temperature holding time of 1 hour.

Note that the above slurry is made of Ni0 crushed to an average particle size of 1.0μ.
30 parts, Y granulated to 45.0μ with a spray dryer
70 parts of SZ, 9 parts of water, and 0.5 parts of deflocculant were put into an MCN pot and kneaded for 20 hours, taken out into a beaker, added with 0.3 parts of binder and 0.1 part of antifoaming agent, and mixed with a magnetic stirrer. Adjustments were made by vacuum degassing for 30 minutes while stirring.

Next, a slurry prepared with submicron YSZ powder and 10 ml of ethanol per 1g of YSZ was applied to the outer surface of the electrode 1, which also served as a support tube, by dipping, and the temperature was increased at a rate of 200° C./h.

The baking operation was repeated several times at a maximum temperature of 1400° C. and a maximum temperature holding time of 1 hour to form an electrolyte layer 3 with a thickness of 20 μm.

Finally, strontium-doped lanthanum manganite (L!, 511-
.
℃/h, a maximum temperature of 1100℃, and a maximum temperature holding time of 3 hours were repeated several times to form an electrode 2 with a thickness of 200μ.
A tube cell was obtained by forming a film.

In the tube cell manufactured as described above, the fuel electrode which also serves as a support tube has an inner part with a relatively coarse structure and an outer part with a relatively dense structure, as shown in FIG. The pores (4) were branched into many parts in the relatively dense structure, each of which opened to the outer surface in contact with the electrolyte layer (3).

In addition, the electrolyte layer did not have its density impaired by cracks or pinholes, and sufficient density was obtained.

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

First, lanthanum manganite (La.

St, -1Mn0. ) as an electrode material is poured into a mold made of plaster, and it is deposited to the specified thickness in 1 to 15 minutes, the slurry is removed, and after drying for several hours, the mold is removed. A porous cylindrical tube with a thickness of 2 mm was formed. Then, this porous cylindrical tube was fired at a heating rate of 120° C./h at a maximum temperature of 1,400° C. and a maximum temperature holding time of 3 hours to produce a support tube-cum-electrode 1.

Next, a slurry prepared with YSZ powder with a particle size of submicron and 1 loml of ethanol per 1g of YSZ was applied to the outer surface of the electrode 1 which also served as a support tube by dipping, and the temperature was increased at a rate of 200° C./h.

The baking operation was repeated several times at a maximum temperature of 1100° C. and a maximum temperature holding time of 1 hour to form an electrolyte layer 3 with a thickness of 20 μm.

Finally, a slurry is prepared using nickel oxide (NIP) and cermet of 8 molythria-stabilized zirconia (YS2) as electrode materials, and this slurry is dipped onto the electrolyte layer 3 formed on the outer surface of the support tube-cum-electrode 1. After drying, the process of baking at a heating rate of 120°C/h, a maximum temperature of 1100°C, and a maximum temperature holding time of 1 hour was repeated several times to form an electrode 2 with a thickness of 200μ to obtain a tube cell. Ta.

In the tube cell produced as described above, the air electrode which also serves as a support tube has an inner part with a relatively coarse structure and an outer part with a relatively dense structure, as shown in FIG. The pores (4) were branched into many parts in the relatively dense structure, each of which opened to the outer surface in contact with the electrolyte layer (3).

In addition, the electrolyte layer did not have its density impaired by cracks or pinholes, and sufficient density was obtained.

(Effects) Since the present invention is constructed as described above, it produces the following effects.

(1) Since the electrode that also serves as a support tube is molded by slip casting, the inner part of the electrode has a relatively coarse structure, while the outermost part in contact with the electrolyte layer has a relatively dense structure, and each pore has a relatively dense structure. The outermost part of the structure has a large number of branches and opens in contact with the electrolyte layer, which improves the diffusion of fuel or air, allowing the electrode, electrolyte,
The number of contacts in the gas phase increases. That is, battery performance is improved by increasing the number of reacting contacts.

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

(2) Firing is performed for each layer, and for the electrolyte layer, which requires particularly denseness, the process of applying slurry and subsequent firing is repeated multiple times, so cracks and pinholes caused by firing are removed. It can be filled and sealed by applying slurry to improve the density. Therefore, it is advantageous in making the layer thinner.

(3) Since all molding processes are unified to wet molding, equipment costs are lower and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a tube cell of a solid electrolyte fuel cell produced by the method of the present invention, FIG. 2 is a cross-sectional view taken along line nn of FIG. 1, and FIG. 3 is an enlarged cross-sectional view of the main parts. 1: Electrode that also serves as a support tube 2: Other electrode 3: Solid electrolyte layer

Claims (1)

[Claims] A method for manufacturing a tube cell of a solid oxide fuel cell formed in a three-layer cylindrical shape by sandwiching an electrolyte layer between a fuel electrode layer and an air electrode layer, comprising the steps of: A step of preparing a slurry of materials constituting one of the electrodes, molding it into a porous cylindrical shape by slip casting, drying, and firing it to form an electrode that also serves as a support tube constituting the innermost layer; A step of integrally forming an electrolyte layer on the outer surface of the electrode that also serves as a support tube by repeating the process of depositing and drying a slurry of a material constituting an electrolyte on the outer surface of the electrode that also serves as a support tube and baking it several times as appropriate; The process of attaching a slurry of the material constituting the other electrode to the layer, drying it, and firing it is repeated several times as appropriate.
1. A method for manufacturing a tube cell for a solid oxide fuel cell, comprising sequentially performing the following steps: forming an electrode as the outermost layer.