JP3105052B2 - Method of forming fuel electrode for solid oxide fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of forming a fuel electrode for a solid oxide fuel cell, and more particularly, to a method of easily and efficiently incorporating a fuel cell having excellent electrochemical reaction and conductivity. In this case, the present invention relates to a method of forming a fuel electrode for a solid oxide fuel cell, which does not cause damage or destruction due to thermal stress between other members.

[0002]

2. Description of the Related Art In a solid oxide fuel cell, when a conductive metal such as nickel is used for a member such as an electrode in order to enhance an electrochemical reaction or conductivity, the material is used in combination with a solid electrolyte or a current collector such as a separator. The battery is likely to be damaged or broken due to distortion due to thermal stress due to incompatibility of the thermal expansion characteristics with the member. In addition, when a metal is used for the fuel electrode, it tends to shrink in a reducing atmosphere at a high temperature, and the battery performance is lowered due to a decrease in air permeability and an increase in contact resistance.

A porous sintered body of metal and ceramics, particularly nickel zirconia cermet, is often studied as a material for a fuel electrode because its coefficient of thermal expansion can be approximated to that of a solid electrolyte. There is a limit to the mixing ratio of ceramics, and a decrease in conductivity is inevitable.

In order to solve these problems, there has recently been proposed a fuel electrode for a solid electrolyte fuel cell which is formed into a plate shape using ceramic particles coated with nickel particles on the surface and then fired (see Japanese Patent Application Laid-Open No. HEI 9-163568). 3-49156).

[0005]

However, this electrode is obtained by forming the particles into a molded plate, and then firing the obtained molded plate to obtain a porous sintered plate. In order to use it as a solid electrolyte fuel cell, a step of forming a dense solid electrolyte membrane on a porous electrode plate is required, and the manufacturing process is inevitably complicated.

[0006] Under such circumstances, the present invention has excellent electrochemical reaction and conductivity, and can be easily and efficiently incorporated into a fuel cell. An object of the present invention is to provide a method for forming a fuel electrode for a solid oxide fuel cell that does not cause destruction.

[0007]

The present inventors have made various studies to develop a method for forming a fuel electrode for a solid electrolyte fuel cell having the above-mentioned preferable characteristics, and as a result, have found that one surface of a solid electrolyte plate has been developed. By applying ceramic particles coated with nickel on the surface to form a porous uniform film, the solid electrolyte and the electrode can be combined and integrated, instead of forming the electrode alone. It has been found that the above-mentioned desirable properties can be imparted to itself, and the object can be achieved, and based on this finding, the present invention has been completed.

That is, according to the present invention, a coating solution in which ceramic particles whose surfaces are coated with nickel is dispersed in an organic binder is applied to one surface of a solid electrolyte plate, dried, and then sintered. Another object of the present invention is to provide a method for forming a fuel electrode for a solid electrolyte fuel cell, which comprises applying, on one surface of a solid electrolyte plate, particles having ceramic particles coated with nickel by plasma spraying. .

In the method of the present invention, the fuel electrode is adhered by using particles whose surface is coated with nickel (hereinafter referred to as nickel-coated ceramic particles), dispersing the particles in a binder containing a solvent, and applying a coating solution. After preparing and applying this coating solution to one side of the solid electrolyte plate,
The solvent is removed by drying, the binder is burned off by subsequent heating, and finally, sintering is performed at a high temperature of about 1300 to 1400 ° C., or plasma spraying of nickel-coated ceramic particles on one surface of the solid electrolyte plate. .

The fuel electrode thus formed is excellent in conductivity, exhibits a coefficient of thermal expansion close to that of the electrolyte, and is porous and excellent in gas permeability.

Although the ceramic particles used in the present invention are not particularly limited, it is preferable to use ordinary solid electrolyte materials such as zirconia, ceria, yttria-stabilized zirconia, and partially stabilized zirconia. Ceramic particles such as alumina and silicon carbide having a small ratio may be used.

The particle size of the ceramic particles is usually 5
It is selected in a range of from 70 to 70 µm, preferably from 10 to 50 µm. If the particle size is less than 5 μm, the porosity of the formed electrode layer will be reduced, and if it exceeds 70 μm, the surface area of nickel involved in the electrochemical reaction will be insufficient.

The use ratio of the ceramic particles to nickel is selected in a range of usually 95: 5 to 10:90, preferably 70:30 to 30:70 by weight. If this ratio is less than 10:90, the matching of the thermal expansion characteristics between the electrode and other fuel cell members becomes insufficient, and if it exceeds 95: 5, the coating with nickel is not complete or the coating is not complete. Since it is very thin, peeling off from the ceramic particles is apt to occur, and the conductivity is undesirably reduced.

As the above-mentioned coating method, a method of applying a brush coating method, a screen printing method, or the like to a predetermined surface of the solid electrolyte plate, for example, is used. As the binder, polyvinyl butyral, polyvinyl alcohol, methylcellulose, or the like is used. As the solvent, alcohol, ketone, aromatic organic solvent, or the like is used, and other dispersing aids are also added as needed. The use ratio of the binder is usually 2 to 20% by weight based on the nickel-coated ceramic particles,
Preferably, the range is 5 to 10% by weight.

The method of the present invention also includes the case where a mixed system of nickel-coated ceramic particles and a small amount of nickel particles is applied.

The material forming the solid electrolyte plate is not particularly limited as long as it has oxygen ion conductivity. For example, stabilized zirconia such as yttria-stabilized zirconia (YSZ) and calcia-stabilized zirconia (CSZ) And a known solid electrolyte material obtained by adding a metal oxide such as alumina to these stabilized zirconia.

Since the solid electrolyte plate provided with the fuel electrode obtained by the method of the present invention and the cathode (air electrode) provided on the other surface constitute a unit cell, the solid electrolyte plate is alternately integrated with the current collector. Thus, a solid electrolyte fuel cell can be manufactured more easily.

The current collector used at this time usually comprises a separator and a terminal plate.

The separator is one less than the number of cells,
It is a dense conductive plate having no gas permeability, and has grooves formed on one side and the other side so as to be generally in the direction crossing each other, thereby forming gas flow paths for the fuel gas and the oxidizing gas. Further, the terminal plate is a dense two conductive plate having no gas permeability, and a plurality of parallel grooves are usually formed on one side to form a gas flow path for the oxidizing gas and a gas flow path for the fuel gas. Have been.

As described above, the separator electrically connects the electrodes of the adjacent single cells, and has grooves formed on both surfaces thereof as flow paths for the fuel gas and the oxidizing gas. Each gas passage on the anode side and the anode side is constituted. A plurality of grooves serving as gas passages are arranged in parallel, and the grooves on one side and the grooves on the other side are arranged in a direction crossing each other, preferably in a direction perpendicular to each other. With this arrangement,
After accumulating the cells, the inlet and outlet of the fuel gas and the inlet and outlet of the oxidizing gas can be arranged on the same side end face, respectively, and the configuration of the gas supply / discharge system as an integrated cell can be made simple and easy. it can.

As the conductive plate used for the separator and the terminal plate, metals such as nickel and cobalt, heat-resistant alloys containing nickel, chromium, cobalt, iron and the like, and various sintered bodies are generally used. Examples of the sintered body include lanthanum chromite-based composite oxides doped with alkaline earth metals and Co, Ni, Fe, Zn, and other metals, conductive ceramics such as silicon carbide, molybdenum silicide, and chromium silicide. Examples include a sintered body obtained by firing a metal material and a heat-resistant inorganic compound in a non-oxidizing atmosphere, for example, in a reducing atmosphere or in a vacuum. As the conductive metal material, for example, nickel metal, nickel-based alloy,
Cobalt metal, cobalt-based alloy, iron metal, iron-based alloy, and the like. As the nickel-based alloy, Ni-Cr
Alloy, Ni-Cr-Fe alloy, Ni-Cr-Mo alloy, Ni-Cr-Mo-Co alloy, Ni-Cr-M
o-Fe alloys and the like, and cobalt based alloys,
Co-Cr alloy, Co-Cr-Fe alloy, Co-C
r-W alloys, Co-Cr-Ni-W alloys and the like, and iron-based alloys include Fe-Ni-Cr alloys, Fe-
Cr-Ni-based alloys, Fe-Cr-Ni-Co-based alloys, and the like can be given. Examples of the heat-resistant inorganic compound include alumina, silica, titania, indium oxide, stannic oxide, silicon carbide, silicon nitride, lanthanum chromite-based composite oxide, and yttrium chromite-based composite oxide.

Next, a preferred embodiment of the method for producing the solid electrolyte fuel cell will be described. A solid electrolyte plate with electrodes, that is, a three-layer structure plate having an anode and a cathode formed on one surface and the other surface of the solid electrolyte plate, respectively, is laminated via a separator to form a single-cell multi-stage series structure, and a single-cell lamination By appropriately adjusting the number and providing terminal plates at both ends, a battery body composed of a series of stacked multi-stage cells composed of many single cells is assembled. At this time, sealing is performed so as not to cause gas leakage by interposing a sealing material between the electrodes, that is, the anode, the cathode and the separator, or one or the other electrode and the terminal plate disposed on one surface and the other surface of the solid electrolyte plate. Is good. The sealing material is provided on the edge of the separator or the terminal plate along the groove direction.

A manifold provided with a supply and exhaust pipe for supplying an oxidizing gas such as fuel gas or air is attached to the battery body thus assembled, that is, a stacked multi-stage cell. For example,
In the cylindrical manifold, four chambers partitioned by the inner surface and the peripheral surface of the cell inscribed therein serve as supply and discharge spaces for the fuel gas and the oxidizing gas, forming the gas passage forming member, and also forming the outer wall. Having a structure of

[0024]

According to the method of the present invention, not only the electrochemical reaction and the conductivity are excellent, but also the fuel cell can be easily and efficiently incorporated into the fuel cell. A fuel electrode for a solid oxide fuel cell that does not occur can be manufactured. In particular, when the plasma spraying method is used, the problem that zirconia is not easily melted and hardly adhered as in the case of spraying a conventional nickel / zirconia mixture can be easily solved, and the resulting nickel-coated ceramic particles are There is an advantage that it can be firmly adhered by fusion of easily meltable nickel on the surfaces that are in contact with each other.

[0025]

Next, the present invention will be described in more detail by way of examples.

Example 1 A three-stage series cell solid electrolyte fuel cell was manufactured as follows.

The solid electrolyte plate contains 3 mol% of yttria.
A 50 x 50 x 0.2 mm calcined plate made of the added partially stabilized zirconia (hereinafter referred to as stabilized zirconia) was used. Then, La ₀ . ₉ S
r ₀ . ₁ A coating liquid in which MnO ₃ particles (average particle size: 5 μm) were dispersed in a terpineol solution of polyvinyl butyral was applied to a thickness of 0.3 mm to form a cathode, and stabilized zirconia particles (average particle size: 50 μm) were provided on the hydrogen passage side. N on the surface
A coating liquid in which particles coated with i (stabilized zirconia: Ni = 1/1 weight ratio) were dispersed in a terpineol solution of polyvinyl butyral was applied to a thickness of 0.3 mm to obtain a fuel electrode. The current collector of the separator and the terminal plate is a 50 × 50 × 5 mm flat plate made of a Ni-based alloy and has a depth of 1.times.
The one provided with a groove of 0 mm was used.

A solid electrolyte plate provided with the electrodes and a current collector are laminated so as to form three single cells, and a glass paste having a softening point of about 800 ° C. is provided between the solid electrolyte plate with the electrodes and the current collector. Was applied for gas sealing. This glass paste softens at the operating temperature of the battery and seals the gas.

A cylindrical alumina manifold was attached to the battery body thus integrated. A glass paste was applied to a contact portion between the manifold and the battery body for gas sealing. A platinum lead wire was welded and electrically connected to a terminal serving as an electrical outlet.

The fuel cell thus manufactured was heated. That is, heating was performed at a rate of 1 ° C./minute from room temperature to 150 ° C., and the temperature was increased at a rate of 5 ° C./minute from 150 ° C. to 300 ° C. to remove the solvent for the glass paste and the binder for the coated electrode. At a temperature of 300 ° C. or higher, a nitrogen gas is flown at a rate of 5 ° C./min.
Temperature. Thereafter, while maintaining the temperature at 1000 ° C., hydrogen was supplied to the anode side and oxygen was supplied to the cathode side to start power generation.
The open voltage was 1.28 V, the ohmic resistance was 40 mΩ, and the gas cross leak was 0.1% or less of hydrogen.

Table 1 shows the current-voltage characteristics (discharge characteristics) of this battery.

[0032]

[Table 1]

Comparative Example In place of the anode material of Example 1, Ni having an average particle size of 5 μm was used.
A fuel cell was produced in the same manner as in Example 1, except that a mixture of powder and stabilized zirconia powder having an average particle size of 50 μm in a weight ratio of 6: 4 was used. This battery was heated and generated power in the same manner as in Example 1. The open circuit voltage is 1.
28 V, ohmic resistance was 60 mΩ, and gas cross leak was 0.1% or less of hydrogen.

Table 2 shows the current-voltage characteristics (discharge characteristics) of this battery.

[0035]

[Table 2]

Example 2 Nickel-coated zirconia particles (average particle size of 40 μm, on one surface of the same solid electrolyte plate as used in Example 1)
(Zirconia / Ni weight ratio = 1/1) with plasma current 40
The fuel was sprayed under the conditions of 0 ampere and a spray pressure of 300 Torr to form a fuel electrode having a thickness of 180 μm. Next, in the same manner as in Example 1, a cathode electrode material was applied to the other surface,
A fuel cell was manufactured.

This battery was heated and then generated power in the same manner as in Example 1. As a result, the open voltage was 1.28 V, the ohmic resistance was 35 mΩ, and the gas cross leak was 0.1% or less of hydrogen.

Table 3 shows the current-voltage characteristics (discharge characteristics) of this battery.

[0039]

[Table 3]

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Toshihiko Yoshida 1-3-1, Nishitsurugaoka, Oi-machi, Iruma-gun, Saitama Prefecture Tonen Co., Ltd. (56) References JP-A-3-95860 (JP, A) JP-A-3-49156 (JP, A) JP-A-5-174833 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/86-8/98

Claims (2)

(57) [Claims] The present invention is characterized in that a coating liquid in which particles of ceramic particles whose surfaces are coated with nickel is dispersed in an organic binder is applied to one surface of a solid electrolyte plate, dried, and then sintered. A method for forming a fuel electrode for a solid oxide fuel cell. 2. A method for forming a fuel electrode for a solid electrolyte fuel cell, comprising applying, on one surface of a solid electrolyte plate, particles of ceramic particles whose surfaces are coated with nickel by plasma spraying.