JP2004055193A - Method for producing electrode material for solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode material for a solid oxide type fuel cell, where highly active composite particle powder is acquired in which the powder material constituting an electrode is evenly dispersed. <P>SOLUTION: The composite powder which is the material for constituting an electrode and synthesized in a water solution is dried by a spray dry method to provide the composite particle powder. By this manufacturing method, the electrode powder which is fine and active and in which the electrode constituting material powder is evenly dispersed is produced. The composite particle powder can be used for the electrode material of the solid oxide type fuel cell to improve power generation performance. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an electrode material for a solid oxide fuel cell.
[0002]
[Prior art]
A solid electrolyte fuel cell with a laminated structure in which a solid electrolyte layer composed of an oxide ion conductor is sandwiched between an air electrode layer (oxidant electrode layer) and a fuel electrode layer is a third-generation fuel cell for power generation. Development is in progress. In a solid oxide fuel cell, oxygen (air) is supplied to the air electrode side, and fuel gas (H ₂ , CO, etc.) is supplied to the fuel electrode side. Both the air electrode and the fuel electrode are porous so that the gas can reach the interface with the solid electrolyte.
[0003]
Oxygen supplied to the air electrode side passes through pores in the air electrode layer and reaches near the interface with the solid electrolyte layer, where electrons are received from the air electrode and converted into oxide ions (O ²⁻ ). Ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode. The oxide ions that have reached the vicinity of the interface with the fuel electrode react with the fuel gas at this portion to generate a reaction product (H ₂ O, CO _2, etc.), and emit electrons to the fuel electrode.
[0004]
The electrode reaction when hydrogen is used as the fuel is as follows.
Air electrode: 1/2 O ₂ + 2e ⁻ → O ²⁻
The fuel ^{_{electrode: H 2 + O 2- → H}} 2 O + 2e -
Whole: H ₂ + 1 / 2O ₂ → H ₂ O
[0005]
The above-mentioned electrode reaction, for example, an ionization reaction (1 / 2O ₂ + 2e ⁻ → O ^2- ) from an oxygen molecule to an oxide ion that occurs on the air electrode side involves the involvement of oxygen molecules, electrons, and oxide ions. It is said that this occurs only at the three-phase interface of a solid electrolyte that carries oxide ions, an air electrode that carries electrons, and a gas phase (air) that supplies oxygen molecules. Similarly, on the fuel electrode side, an electrode reaction occurs at a three-phase interface between the solid electrolyte, the fuel electrode, and the gaseous fuel gas. Therefore, it is considered that increasing this three-phase interface is advantageous for the smooth progress of the electrode reaction.
[0006]
Here, the solid electrolyte layer serves as a moving medium for oxide ions and also functions as a partition wall for preventing direct contact between the fuel gas and air, and thus has a gas impermeable dense structure. This solid electrolyte layer must be composed of a material that has high oxide ion conductivity, is chemically stable under the conditions from the oxidizing atmosphere on the air electrode side to the reducing atmosphere on the fuel electrode side, and is resistant to thermal shock. As a material satisfying such requirements, stabilized zirconia (YSZ) to which yttria is added is generally used.
[0007]
On the other hand, both the air electrode (cathode) layer and the fuel electrode (anode) layer, which are electrodes, need to be made of a material having high electron conductivity. Since the air electrode material must be chemically stable in a high-temperature oxidizing atmosphere of about 700 ° C., a metal is inappropriate, and a perovskite-type oxide material having electron conductivity, specifically LaMnO ₃ Alternatively, LaCoO ₃ or a solid solution in which part of La is replaced with Sr, Ca, or the like is generally used. The fuel electrode material is generally a metal such as Ni or Co, or a cermet such as Ni-YSZ or Co-YSZ.
[0008]
FIG. 1 shows an internal structure of a power generation cell 1 in a solid oxide fuel cell. In the figure, reference numeral 2 denotes an air electrode layer, reference numeral 3 denotes a solid electrolyte layer, and reference numeral 4 denotes a fuel electrode layer.
[0009]
[Problems to be solved by the invention]
Conventionally, in order to produce the above-described electrode material for a fuel cell, the powder of the constituent material of each electrode is mixed using a stirring and mixing device having a pulverizing effect such as a ball mill, a planetary ball mill, and a sand mill to obtain a composite particle powder. Had gained body. Each electrode is prepared by mixing an organic binder into the composite particle powder and stirring to form a paste. The paste is applied to the surface of the solid electrolyte layer by a blade method, screen printing, or the like, followed by drying, press molding, and firing. Formed through
[0010]
By the way, in the stirring and mixing device such as the ball mill and the planetary ball mill described above, the ball is crushed by collision and contact between the balls, and the ball is moved all over the container, so that the entire stirring motion is also performed. Although such a granulation method is widely used in various fields, in the case of the stirring and mixing using mechanical motion, (1) uniform dispersion is caused by a difference in specific gravity of the mixed powder. It is difficult to obtain a mixture. (2) It is difficult to obtain a uniformly dispersed mixture due to the difference in particle size. (3) A lot of time is required for stirring and mixing.
And the like.
[0011]
As an electrode material of a solid oxide fuel cell, it is important to use a composite particle powder in which an electrode constituent material powder is uniformly dispersed, and it is considered that each particle forming a mixture is uneven. In addition, the gas diffusivity and electron conductivity of the electrode at the three-phase interface deteriorate, and the power generation performance decreases.
[0012]
The present invention has been made in view of the above problems, and provides a method for producing an electrode material for a solid oxide fuel cell, which can provide highly active composite particle powder in which electrode constituent material powders are uniformly dispersed. It is aimed at.
[0013]
[Means for Solving the Problems]
That is, the present invention is a method for producing an electrode material for a solid oxide fuel cell in which a composite powder of an electrode constituent material synthesized with an aqueous solution is dried by a spray drying method to obtain a composite particle powder.
[0014]
The spray drying method is a method in which a liquid is made into a fine mist, and this is ejected into hot air in a container to instantaneously obtain a powdery dried product.
In the present invention, two or more kinds of electrode constituent material powders are dissolved and dispersed in a liquid, and dried by this spray drying method, whereby fine and highly active composite particle powders in which the electrode constituent material powders are uniformly dispersed are obtained. It can be used as an electrode material of a solid oxide fuel cell to improve power generation performance.
In addition, since the residence time of the particles during drying is only a few seconds, a large amount of time is not required for producing (granulating) the electrode material, so that the spray drying method is excellent in continuous productivity and mass productivity. It can be said that the production cost is reduced.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described. The present invention relates to a method for producing an electrode material for a solid oxide fuel cell, in which a composite powder of an electrode constituent material synthesized with an aqueous solution is dried by a spray drying method to obtain a composite particle powder in which the electrode constituent powder is uniformly dispersed. is there.
[0016]
In the present embodiment, a method for producing an anode material by a spray drying method will be described.
First, _{Ce (NO 3)} nitrates of the fuel electrode material dissolved _{3 · 6H 2 O, Sm (} NO 3) 3 · 6H 2 O, Ni (NO 3) was added to 2 · 6H ₂ O to a predetermined amount of distilled water Let it.
Next, NaOH is gradually added dropwise to this solution so as to have a pH of 13, and hydroxides Ce (OH) ₃ , Sm (OH) ₃ , and Ni (OH) _{2 serving} as electrode constituent materials are precipitated.
Next, the supernatant is separated from the concentrated precipitate by centrifugation of the precipitate, distilled water is added and the mixture is stirred, and centrifugation is repeated 5 to 6 times to wash the precipitate.
Finally, the hydroxide composite uniformly dispersed in distilled water is dried using the above-mentioned spray drying method, and fine and highly active spherical composite powder in which CeO ₂ , Sm ₂ O ₃ , and NiO are uniformly dispersed. Get.
[0017]
The spray drying method is excellent in continuous productivity and mass productivity because the residence time of particles during drying is only a few seconds and a lot of time is not required for producing (granulating) the electrode material. Therefore, the cost of the electrode material can be reduced.
[0018]
When an electrode is formed on the surface of the solid electrolyte layer using the composite particle powder, an organic binder is mixed with the composite particle powder, stirred to form a paste, and applied by a blade method, screen printing, or the like. Then, conventionally known electrode forming methods such as drying, press molding, and firing can be employed. As described above, the power generation performance of the solid oxide fuel cell is improved by using the fine and highly active composite particle powder in which the electrode constituent material powder is uniformly dispersed as the fuel electrode.
[0019]
As described above, in a solid oxide fuel cell, each electrode (air electrode layer and fuel electrode layer) is required to be porous and have a large three-phase interface length (a large electrode reaction field). ing. In the spray drying method used in the present invention, the particle diameter to be granulated can be controlled by changing conditions such as a vaporization temperature, a gas flow rate, and a liquid supply amount. The length of the three-phase interface is increased by changing the spray-drying conditions and adjusting the particle size to be granulated so that fine particles are present at the part in contact with the layer and coarse particles are present away from the electrolyte layer. It is also possible to improve battery performance.
[0020]
【The invention's effect】
As described above, according to the present invention, since the composite powder synthesized from the aqueous solution is dried by the spray drying method, the fine and highly active electrode powder in which the electrode constituent material powder is uniformly dispersed is granulated. be able to. By using this composite particle powder as an electrode material for a solid oxide fuel cell, the power generation performance of the solid oxide fuel cell can be improved.
Further, the spray drying method is excellent in continuous productivity and mass productivity, so that the cost of the electrode material can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing the internal structure of a power generation cell in a solid oxide fuel cell.
[Explanation of symbols]
Reference Signs List 1 Power generation cell 2 Air electrode layer 3 Solid electrolyte layer 4 Fuel electrode layer

Claims (1)

A method for producing an electrode material for a solid oxide fuel cell, wherein a composite powder of an electrode constituent material synthesized with an aqueous solution is dried by a spray drying method to obtain a composite particle powder.

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