JP2006092896A - Complex electrode for solid oxide fuel cell and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a complex electrode for a solid oxide fuel cell not requiring high-temperature treatment like sintering, without any restriction on quality of base plates or other supporting members, capable of preventing crack, deterioration or exfoliation of the material component due to coagulation or difference of thermal expansion rate thereof, and to provide a manufacturing method of the same and a solid oxide fuel cell equipped with the above complex electrode. <P>SOLUTION: The complex electrode, formed by dispersing powder 2 composed of a second electrode material in a gas-permeable continuous layer 1 made of a first electrode material driven from solution, is formed by forming multi-layers directly on the base plate by using liquid prepared by dispersing powder made of the second electrode material in raw-material solution of a first electrode material, and by applying a wet method, preferably, a chemical solution method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a manufacturing technique of a composite electrode used in a solid oxide fuel cell, and can be used as a fuel electrode as a cermet, or as an air electrode by combining a plurality of electrode materials, and agglomeration of material components. And a composite electrode for a solid oxide fuel cell capable of adjusting the coefficient of thermal expansion and conductivity, and a thin film without subjecting such a composite electrode to high temperature treatment such as sintering. The present invention relates to a method for producing a composite electrode for a solid oxide fuel cell that can be formed.

  A solid oxide fuel cell (SOFC) includes an electrolyte made of a solid oxide such as yttria-stabilized zirconia (YSZ), and a fuel electrode disposed so as to face each other with the solid oxide electrolyte interposed therebetween. And an air electrode, which operates at a high temperature exceeding 600 ° C., for example, and supplies a fuel gas such as hydrogen to the fuel electrode side, and an oxidizing gas such as air to the air electrode side Can be used to obtain DC power based on an electrochemical reaction.

As a fuel electrode material of a solid oxide fuel cell, in general, a metal material such as Ni, Ni—YSZ, Ni—SDC (Samarium Doped Ceria), Ni—CGO (Cerium-Gallium Composite Oxide), A cermet material such as Cu—CeO ₂ (ceria) is used.
On the other hand, the air electrode material, and metal material such as Pt or _{Pd, LSM (La 1-X} Sr X MnO 3), LCM (La 1-X Ca X MnO 3), LSC (La 1-X Sr X CoO ₃ ) and composite oxides such as SSC (Sm _1-X Sr _X CoO ₃ ) are used.

  Of the above electrode materials, the cermet used as the fuel electrode is a composite material of metal and ceramics, and the air electrode made of a composite oxide material also considers peeling and cracking due to differential expansion when subjected to a thermal cycle. Then, in order to make a thermal expansion coefficient equivalent to a board | substrate and electrolyte, it is desirable to use the electrode material which compounded 2 or more types of complex oxide materials.

As a method for producing such a composite material composed of two or more materials, for example, Patent Document 1 discloses that a Ni layer is obtained by applying composite plating on a substrate using a Ni plating solution in which water-repellent particles are dispersed. It is disclosed to form a water-repellent film supporting water-repellent particles.
Patent Document 2 discloses that a cathode powder and a gel made of an alkoxide having the same composition as the powder are mixed to prepare a cathode slurry, which is applied to form a cathode.
JP 07-166123 A JP 2000-243405 A

However, although Patent Document 1 is a method for producing a composite material, it is a water-repellent coating and is not related to a composite electrode, and the dispersant is particles of a water-repellent polymer such as PTFE, not an electrode material.
In addition, the cathode forming method described in Patent Document 2 relates to an electrode (air electrode) material, but since a powder obtained by gelling an alkoxide on the surface is used, as in the powder sintering step, Since it is necessary to produce a slurry using a binder such as PVB (polyvinyl butyral), there is a problem that the number of processes is increased and the process becomes complicated.

  The present invention has been made to solve the above-mentioned problems in a composite electrode used as a fuel electrode or an air electrode of a solid oxide fuel cell, and its object is not to require high-temperature treatment such as sintering. Therefore, it is not necessary to use expensive heat-resistant materials for substrates and other support members, etc., and solid oxide forms that can prevent performance degradation, peeling, and cracking due to differences in the aggregation of materials and thermal expansion coefficients A method for producing a composite electrode for a solid oxide fuel cell, in which a composite electrode for a fuel cell and a composite electrode in which electrode material powder is uniformly dispersed can be directly formed on a substrate in a thin film at a low temperature, and An object of the present invention is to provide a solid oxide fuel cell having such a composite electrode.

  In order to solve the above-mentioned problems, the present inventors have intensively studied the material, film forming method, conditions, etc. of the composite electrode. As a result, the raw material solution of the electrode material obtained by dispersing fine powder made of the electrode material is used. In a gas permeable continuous layer made of a solution-derived electrode material, a powder is formed by a wet method such as plating or electrophoresis, especially by chemical solution method (CSD method) without performing high temperature treatment such as sintering. The inventors have found that a composite electrode in which the derived electrode material powder is uniformly dispersed can be formed into a thin film shape, and the present invention has been completed.

  The present invention is based on the above findings, and the composite electrode for a solid oxide fuel cell of the present invention is a powder made of a second electrode material in a gas permeable continuous layer made of the first electrode material. The electrode manufacturing method of the present invention is preferably applied to the manufacture of the composite electrode for a solid oxide fuel cell, wherein the first electrode material Using a dispersion obtained by dispersing the powder made of the second electrode material in the raw material solution, a multilayer film can be directly formed on the substrate by a wet method such as a plating method, an electrophoresis method, or a chemical solution method. It is a feature.

  According to the present invention, by using a dispersion in which a powder made of the second electrode material is dispersed in a raw material solution of the first electrode material, a multilayer film is formed directly on the substrate by a wet method. Sintering the composite electrode for a solid oxide fuel cell in which the powder composed of the second electrode material derived from the powder is dispersed in the gas permeable continuous layer composed of the first electrode material derived from Thus, it becomes possible to form a thin film by a simplified process without adopting the high-temperature treatment method, and the device manufacturing temperature can be lowered, so that an inexpensive member such as a metal can be used. In addition, it is possible to reduce the amount of the second electrode material used and to coat the pores, and to disperse the electrode material of two or more components in a uniform and desired structure, and the base material and the electrolyte It is possible to adjust to a desired thermal expansion coefficient in consideration of the thermal expansion coefficient of the material.

  Hereinafter, the composite electrode for a solid oxide fuel cell according to the present invention will be described in more detail together with its production method.

  As schematically shown in FIG. 1, the composite electrode for a solid oxide fuel cell according to the present invention includes a powder made of a second electrode material in a gas permeable continuous layer 1 made of a first electrode material. 2 is in a dispersed state, and such a composite electrode uses a dispersion liquid in which the powder made of the second electrode material is dispersed in the raw material solution of the first electrode material as described above. It can be obtained by directly forming a multilayer film on a substrate by a wet method. That is, the gas permeable continuous layer 1 made of the first electrode material is derived from a solution, and the powder 2 made of the second electrode material is a powder made of the second electrode material dispersed in the solution. Will come from.

Specifically, the wet method means a plating method, an electrophoresis method, a chemical solution method, a metal such as Ni, Cu, Pt, 8YSZ (8 mol% yttrium-added stabilized zirconia), LSGM (lanthanum gallate). ion conductive oxide _{etc., LSM (La 1-X Sr} X MnO 3), is used as the _{SSC (Sm 1-X Sr X} CoO 3) thin film forming method such as mixed conducting oxides such.
In the wet method, a powder composed of a second electrode material, which is the second component of the composite electrode, is dispersed in a raw material solution of the wet method containing the first component, that is, the constituent component of the first electrode material. By firing at a low temperature at a temperature of about 250 to 400 ° C., for example, at a room temperature in the case of a plating method or an electrophoresis method, for example, at a temperature of about 250 to 400 ° C. The second component powder can be fixed in the electrode film and can be formed at low temperature and low cost.

At this time, the second component may be the same component as the first component or a different component, and one or more kinds of powders may be used in combination. In addition, since the gas permeability is calculated | required for the electrode for fuel cells, pore forming materials, such as carbon and a polymer, can be used as needed, and can be disperse | distributed with a powder in a raw material solution.
In addition, in the chemical solution method, as shown in FIG. 2, thin films of about 0.05 to 0.2 μm are formed in multiple stages by spraying, spin coating, etc., thereby reducing film stress and dispersing. The particles can be bound to form an electrode layer.

  In the case of the chemical solution method, the film formation of the composite electrode itself can be performed by low-temperature baking as described above. However, in order to improve the durability, 500 to 600 ° C. close to the actual use temperature of the fuel cell. More preferably, it is desirable to apply a finishing treatment to be adapted by annealing at a temperature of about 700 ° C.

As described above, the first component is formed by a wet method such as a plating method, an electrophoresis method, or a chemical solution method. Among these, it is desirable to employ a chemical solution method (CSD method).
Chemical solution method means metal alkoxide, metal acetylacetonate, metal acetate, carboxylate such as oxalate, naphthenate, octylate, metal nitrate, chloride, oxychloride, etc. The starting material is used as a starting material, and this is applied by spin coating, dipping, spraying, electrostatic spraying, thermal spray decomposition (SPD method), etc. Alternatively, it is a method of forming a metal oxide layer, and by using such a CSD solution, a thin film of electrode materials (LSGM, 8YSZ, SDC, LSM, SSC, etc.) composed of various metals can be easily formed on the substrate. Depending on conditions, nano-sized fine particles can be produced on the electrode surface.

  By using the CSD solution, the second component powder dispersed in the solution can be fixed in the thin film composed of the first component, and the powder 2 in the thin film is a continuous layer 1 of the first component. Although it is covered (see FIG. 1), since it is a thin film, gas permeation easily occurs, and the first component can sufficiently function as an electrode material.

The thickness of the composite electrode of the present invention is preferably 10 μm or less, more preferably 2 μm or less.
That is, when the thickness of the electrode exceeds 10 μm, peeling or cracking due to film stress is likely to occur, and gas supply to the electrolyte is insufficient, and the battery function tends to deteriorate. Since the electrode layer formed by the wet method is a thin film, even if the powder as the second component is coated, the thin film can pass the gas as long as it is a thin film. Can function.

The particle size of the second component powder is desirably in the range of 0.1 to 3 μm, more preferably 0.2 to 1 μm.
That is, when the particle size of the powder is less than 0.1 μm, poor dispersion due to aggregation is likely to occur, and conversely, when it exceeds 3 μm, it is difficult to sufficiently diffuse into the thin film electrode layer. Due to the tendency.

As the first component, that is, the first electrode material, an oxide having ionic conductivity and / or mixed conductivity can be selected. Examples of such oxide materials include conventionally known electrolyte materials having oxygen ion conductivity, such as neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), yttria (Y ₂ O ₃ ), and oxidation. Preferably, stabilized zirconia in which scandium (Sc ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ), or the like is dissolved, ceria (CeO ₂ ) solid solution, bismuth oxide solid solution, LaGa solid solution perovskite, or the like is preferably used. The film can be formed by a chemical solution method such as a sol-gel method.
Moreover, air electrode materials, such as a lanthanum cobalt type oxide (LSC), a lanthanum manganese type oxide (LSM, LCM), and a samarium cobalt type oxide (SSC), can be used conveniently.

That is, an electrolyte material (ion conductive oxide) as described above is used as the first electrode material, and a powder made of metal and / or metal oxide, such as Ni, NiO, By selecting Cu, CuO or the like, it is possible to obtain a cermet in which metal powder is dispersed in a continuous layer made of an electrode material, and to function as a fuel electrode.
In this case, since the ion conductive oxide covers the periphery of the metal powder, the fuel electrode has excellent adhesion to the electrolyte layer and can easily pass ions.

  In addition, when the above-described air electrode materials (mixed conductive oxides) are selected as the first and second electrode materials, they can function as an air electrode, and the coefficient of thermal expansion depends on the combination of materials. Such adjustments can be made, the difference in thermal expansion from the substrate and the electrolyte can be eliminated, and cracking and peeling can be prevented. When the same type of air electrode material is combined, the powder can be bound at a low temperature, and since it is the same type, the familiarity is good and the electrode can be formed at a low temperature with reduced grain boundary resistance.

  On the other hand, metals and / or metal oxides such as Ni, NiO, Pt, Pd, Ru, Cu, CuO, Fe, Au, Ag, Co, Mo, W, Cr, etc. may be selected as the first electrode material. it can. These can be formed by plating or a chemical solution method such as a sol-gel method. When such a material is a precious metal, the chemical solution method can be used to form a thin film only in the vicinity of the surface layer that requires a function. The amount of expensive raw materials used can be reduced.

Specifically, the metal and / or metal oxide (for example, Ni, NiO, Cu, CuO, etc.) as described above is used as the first electrode material, and the electrolyte material (as described above) is used as the second electrode material. By selecting the ion conductive oxide), it is possible to obtain a cermet in which the powder of the electrolyte material is dispersed in the continuous layer made of metal, and to function as a fuel electrode. Further, in this case, the second electrode material has a structure in which the metal is covered around the ion conductive oxide, so that the fuel electrode can easily pass an electron.
A metal and / or metal oxide (for example, Ag, Pt, Fe, Co, Ce, Ni and their oxides) as described above is used as the first electrode material, and the above as the second electrode material. By selecting a suitable air electrode material (electron-conducting composite oxide), a composite electrode in which powder of the air electrode material is dispersed in a continuous layer of metal can be made to function as an air electrode. Can do. In this case, since the structure is such that the metal is covered around the electron conductive oxide, the air electrode is easy to pass electrons.

  Furthermore, the composite electrode of the present invention can be used as a fuel electrode or an air electrode of a solid oxide fuel cell as described above, and the composite electrode described above can be formed on a gas permeable substrate or an electrolyte substrate. A solid oxide fuel cell unit cell is formed by laminating an electrolyte on an electrode substrate and then this composite electrode on the electrode substrate, and the solid oxide fuel of the present invention is stacked by stacking a plurality of these single cells. A battery can be obtained.

  In the solid oxide fuel cell, since the thin composite electrode is provided, the stack is thinned and lightened, and high temperature treatment such as sintering is not required when forming the electrode. An inexpensive metal material such as stainless steel can be used as the support member, and the material and the manufacturing cost can be reduced. Furthermore, since the electrode has a composite structure in which two or more electrode materials are uniformly dispersed, the electrode performance can be improved and the coefficient of thermal expansion can be adjusted. can do.

  The electrolyte material of the solid oxide fuel cell of the present invention is not particularly limited, and known electrolyte materials such as YSZ, SSZ (scandium stabilized zirconia), SDC (samarium doped ceria), LSGM (lanthanum gallate). ) Etc. can be used.

  Hereinafter, the present invention will be specifically described based on examples. Needless to say, the present invention is not limited to these examples. Further, in this example, “%” indicates mass percentage unless otherwise specified.

Example 1
(1) Formation of a porous substrate A fine hole was formed by performing chemical etching on a metal foil made of ferritic stainless steel SUS430 having a thickness of 0.1 mm to obtain a porous substrate 11 having a porosity of 70%.

(2) Formation of fuel electrode layer By applying a Ni-SSZ paste on the porous surface of the porous substrate 11 by screen printing, filling it into the opening, and firing it at 1000 ° C. in a reducing atmosphere. A fuel electrode 12 made of Ni-SSZ cermet having a porosity of 30% was formed.

(3) Formation of electrolyte layer 8 YSZ raw material solution (0.2 M ethanol + butyl carbitol solution of yttrium chloride and acetylacetonatozirconium compounded to 8 mol% Y ₂ O ₃ was sprayed at 500 ° C. by spray pyrolysis. The porous substrate heated to 1 mm was sprayed to form an electrolyte layer 13 made of 8YSZ to a thickness of 2 μm and annealed at 700 ° C. in an inert atmosphere.

(4) Formation of air electrode Subsequently, SSC powder having an average particle size of 0.3 μm was mixed with SSC raw material solution (Sm _0.5 Sr _0.5 CoO ₃ , samarium nitrate, strontium chloride and cobalt nitrate 0 A dispersion obtained by dispersing 5% in a 0.05M ethanol + butyl carbitol solution was sprayed 20 times on the porous substrate heated to 500 ° C. by a spray pyrolysis method, and a gas permeability of 30% porosity consisting of SSC. In the continuous layer, an air electrode layer 14 having a composite structure in which powders of SSC were also uniformly dispersed was formed to a thickness of 1 μm to obtain a single cell of a solid oxide fuel cell as shown in FIG. .

(5) Evaluation As a result of measuring the power generation performance of the single cell thus obtained at 600 ° C., it was confirmed that the power generation output was 0.1 W / cm ² .

Example 2
(1) Formation of porous substrate Frame 16 made of ferritic stainless steel SUS430 around nickel foam 15 having a porosity of 90% and a thickness of 0.2 mm obtained by sintering Ni powder at 800 ° C. Were diffusion bonded and used as a porous substrate.

(2) Formation of fuel electrode layer Electrolytic plating is performed using a dispersion liquid in which 10% of an SDC powder having an average particle size of 0.3 μm is dispersed in a 10% aqueous solution of nickel nitrate as a plating solution. And a fuel electrode having a structure (Ni-SDC cermet) in which SDC powder is uniformly dispersed in a gas permeable continuous layer made of Ni and having a porosity of 10% on the exposed portion of the nickel foam 15 from the frame 16 on the substrate. 12 was formed to a thickness of 5 μm.

(3) Formation of Electrolyte Layer On the fuel electrode 12, YSZ was formed to a thickness of 3 μm by sputtering at 700 ° C. to form an electrolyte layer 13 made of YSZ.

(4) Formation of air electrode Subsequently, the LSC is formed at room temperature and the air electrode layer 14 having a porosity of 20% made of LSC is formed by sputtering to a thickness of 0.5 μm, and solid oxidation as shown in FIG. A single cell of a physical fuel cell was obtained.

(5) Evaluation As a result of measuring the power generation performance of the single cell thus obtained at 600 ° C., it was confirmed that the power generation output was 0.08 W / cm ² .

Example 3
(1) Formation of porous substrate A fine hole was formed by applying chemical etching to the central part of a 0.2 mm thick nickel foil to obtain a porous substrate 17 having a porosity of 50%.

(2) Formation of fuel electrode layer A 10% aqueous solution of nickel nitrate in which 20% of 8YSZ powder having an average particle size of 0.3 μm is dispersed is applied to the porous surface at the center of the porous substrate 17 by a spin coating method. After drying, it was fired at 500 ° C. Then, by repeating such a coating-drying-firing cycle until a film thickness of 2 μm is obtained, a structure (Ni-8YSZ cermet) in which 8YSZ powder is uniformly dispersed in a gas-permeable continuous layer made of Ni. A fuel electrode 12 was formed.

(3) Formation of Electrolyte Layer YSZ was formed to a thickness of 10 μm at a temperature of 700 ° C. by EB vapor deposition, and an electrolyte layer 13 made of YSZ was formed on the fuel electrode 12.

(4) Formation of air electrode Then, 5% of SSC powder having an average particle diameter of 0.5 μm is dispersed in an SDC raw material solution (Ce nitrate, nitric acid blended to become Ce _0.8 Sm _0.2 O _1.9) By spraying the samarium aqueous solution 20 times on the porous substrate heated to 500 ° C. by spray pyrolysis, the air electrode layer 14 is formed to a thickness of 0.5 μm, and the solid oxidation as shown in FIG. A single cell of a physical fuel cell was obtained.

(5) Evaluation As a result of measuring the power generation performance of the single cell thus obtained at 600 ° C., it was confirmed that the power generation output was 0.1 W / cm ² .

1 is a schematic cross-sectional view conceptually showing the structure of a composite electrode for a solid oxide fuel cell of the present invention. It is a schematic cross section which shows the lamination | stacking method of the composite electrode for solid oxide fuel cells of this invention. It is sectional drawing which shows the laminated structure of the solid oxide fuel cell concerning the 1st Example of this invention. It is sectional drawing which shows the laminated structure of the solid oxide fuel cell concerning the 2nd Example of this invention. It is sectional drawing which shows the laminated structure of the solid oxide fuel cell concerning the 3rd Example of this invention.

Explanation of symbols

1 Gas-permeable continuous layer (first electrode material)
2 Powder (second electrode material)

Claims (14)

  A composite electrode for a solid oxide fuel cell, wherein a powder made of a second electrode material is dispersed in a gas permeable continuous layer made of a first electrode material.   The gas permeable continuous layer made of a first electrode material is derived from a solution, and the powder is derived from a powder made of a second electrode material dispersed in the solution. A composite electrode for a solid oxide fuel cell as described.   The composite electrode for a solid oxide fuel cell according to claim 1 or 2, wherein the powder comprises two or more components.   The composite electrode for a solid oxide fuel cell according to any one of claims 1 to 3, wherein the thickness is 10 µm or less.   5. The composite electrode for a solid oxide fuel cell according to claim 1, wherein the powder has a particle size of 0.1 to 3 μm.   The composite electrode for a solid oxide fuel cell according to any one of claims 1 to 5, wherein the first electrode material is an oxide having ion conductivity and / or mixed conductivity. .   The composite electrode for a solid oxide fuel cell according to claim 6, wherein the second electrode material is an oxide having ion conductivity and / or mixed conductivity and functions as an air electrode.   The composite electrode for a solid oxide fuel cell according to claim 6, wherein the second electrode material is a metal and / or a metal oxide and functions as a fuel electrode.   The composite electrode for a solid oxide fuel cell according to any one of claims 1 to 5, wherein the first electrode material is a metal and / or a metal oxide.   The composite electrode for a solid oxide fuel cell according to claim 9, wherein the second electrode material is a metal and / or a metal oxide.   The composite electrode for a solid oxide fuel cell according to claim 9, wherein the second electrode material is an oxide having ion conductivity and / or mixed conductivity, and functions as a fuel electrode.   A solid oxide form characterized in that a multilayer film is formed directly on a substrate by a wet method using a dispersion obtained by dispersing a powder of the second electrode material in a raw material solution of the first electrode material A method for producing a composite electrode for a fuel cell.   13. The method for producing a composite electrode for a solid oxide fuel cell according to claim 12, wherein the wet method is a chemical solution method.   A solid oxide fuel cell comprising the composite electrode according to any one of claims 1 to 11.

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