JP5114852B2 - Method for producing solid oxide fuel cell - Google Patents

Description

  The present invention relates to a method for producing a solid oxide fuel cell.

  Solid oxide fuel cells (SOFCs) are currently being developed as third-generation power generation fuel cells, and three types are proposed: cylindrical, monolith, and flat plate stack. Each of them has a laminate in which a solid electrolyte (electrolyte layer) made of an oxide ion conductor is sandwiched between an air electrode layer (cathode) and a fuel electrode layer (anode). Usually, the single cell which consists of this laminated body is laminated | stacked alternately with a separator, and the fuel cell stack is comprised (for example, refer patent document 1).

In the solid oxide fuel cell, oxygen (air) is supplied to the air electrode layer side, and fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side. Oxygen supplied to the air electrode layer passes through the pores in the air electrode layer and reaches the vicinity of the interface with the electrolyte layer, and receives electrons from the air electrode layer at this portion to form oxide ions (O ²⁻ ). Ionized. The oxide ions move (diffuse) in the electrolyte layer toward the fuel electrode layer. The oxide ions that reach the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to become reaction products (H ₂ O, CO _2, etc.), and simultaneously release electrons. The electrons reach the air electrode layer after performing electrical work through an external electric circuit.

The electrode reaction that occurs on the air electrode layer side, that is, the ionization reaction from oxygen molecules to oxide ions (1 / 2O ₂ + 2e ⁻ → O ²⁻ ), involves the three components of oxygen molecules, electrons, and oxide ions. It occurs at a three-phase interface between an electrolyte layer that carries oxide ions, an air electrode layer that carries electrons, and a gas phase (air) that supplies oxygen molecules. Similarly, on the fuel electrode layer side, an electrode reaction occurs at the three-phase interface of the electrolyte layer, the fuel electrode layer, and the gas phase (fuel gas). Therefore, it is considered that increasing the three-phase interface is advantageous for smooth progress of the electrode reaction.

  The electrolyte layer is a moving medium for oxide ions and also functions as a partition wall for preventing the fuel gas and air from coming into direct contact with each other. Therefore, the electrolyte layer has a dense structure that is impermeable to gas. This electrolyte layer is composed of a material that has high oxide ion conductivity, is chemically stable under conditions from the oxidizing atmosphere on the air electrode layer side to the reducing atmosphere on the fuel electrode layer side, and is resistant to thermal shock. As a material that satisfies this requirement, a metal oxide film made of stabilized zirconia (hereinafter abbreviated as “YSZ”) to which yttria is added is generally used.

On the other hand, both the air electrode layer and the fuel electrode layer need to be made of a material having high electron conductivity. Since the material of the air electrode layer must be chemically stable in an oxidizing atmosphere at around 1000 ° C., metals are inappropriate. For example, perovskite type oxide materials having electron conductivity, specifically LaMnO ₃ or LaCoO ₃ or a solid solution in which a part of La in these materials is substituted with Sr, Ca or the like is generally used. Further, as a material for the fuel electrode layer, a metal such as Ni or a cermet such as Ni—YSZ is generally used. It should be noted that the metal such as Ni is normally in an oxide state such as NiO when the fuel electrode layer is formed, but is reduced to metal (Ni or the like) during operation of the fuel cell (during power generation).

  As this type of solid oxide fuel cell, for example, on a porous support substrate that also serves as one electrode layer (fuel electrode layer or air electrode layer), a thin-film electrolyte layer and the other electrode layer (fuel electrode layer or And an air electrode layer) are formed sequentially (see, for example, Patent Document 2). In order for the electrolyte layer to function as a gas partition, it is desirable that the electrolyte layer be densely formed. In addition, in order for the electrolyte layer to function as an ion conductive film, it is desirable to make the film thickness thinner. .

  As a method for forming the electrolyte layer, for example, there is a method in which a slurry is applied on a porous support substrate by a screen printing method or the like, and this is baked to form an electrolyte layer. In this method, a dense electrolyte layer is generally formed by sintering at 1200 to 1700 ° C. At this time, it is important to prevent the substrate from being damaged and to form the electrolyte layer densely in consideration of the difference in thermal shrinkage between the substrate and the electrolyte layer. For example, Patent Document 3 proposes a method of forming an electrolyte layer by applying a slurry containing a plurality of types of powders having different specific surface areas (average particle diameters). According to this method, economic efficiency and mass productivity are improved, and it is easy to increase the area of the electrolyte layer. Patent Document 4 proposes a slurry capable of forming a homogeneous and dense electrolyte layer.

  Further, as a method different from the above, in Patent Document 5, a substrate is formed with zirconia stabilized by calcia, and the substrate is heated to 1000 to 1500 ° C. with an electrochemical deposition method (EVD method). The method of forming an electrolyte layer is proposed. Thereby, a dense electrolyte layer having a small thickness can be formed.

Further, as another method different from the above, there is a method of forming an electrolyte layer on a porous support substrate by a plasma spraying method. The plasma spraying method is characterized by a high deposition rate. However, a film formed by the plasma spraying method usually has several percent of pores, and the film is not dense enough. Therefore, Patent Document 6 proposes a method in which after an electrolyte layer is formed by a plasma spraying method, an organic metal solution containing a constituent element of the electrolyte layer is applied to perform a sealing treatment and densify. .
JP 2004-79332 A JP 2004-158313 A JP 2001-23653 A JP 2002-15757 A JP-A-61-91880 JP-A-9-50818

  However, in the above method, for example, a heat treatment step of 1000 ° C. or higher for improving the density and expensive equipment such as a plasma processing apparatus are required, and thus the electrolyte layer cannot be easily densified. There was sex. In particular, when the heat treatment is performed at a high temperature, the cell itself may be damaged due to cracks or peeling due to the difference in thermal shrinkage between the electrode layer and the electrolyte layer.

  The present invention has been made in view of such circumstances, and provides a method for manufacturing a solid oxide fuel cell capable of easily densifying a metal oxide film constituting an electrolyte layer.

A first manufacturing method of a solid oxide fuel cell according to the present invention includes a solid fuel electrode layer containing nickel oxide, and an electrolyte layer made of a metal oxide film formed on the dense fuel electrode layer. A method for manufacturing a physical fuel cell, comprising:
The metal oxide film is formed by immersing the dense fuel electrode layer in a metal oxide film forming solution containing a metal source ,
The dense fuel electrode layer has a relative density of 90% or more .

A second method for producing a solid oxide fuel cell according to the present invention comprises a solid oxide layer comprising a dense fuel electrode layer containing nickel oxide and an electrolyte layer comprising a metal oxide film formed on the dense fuel electrode layer. A method for manufacturing a physical fuel cell, comprising:
By immersing the dense fuel electrode layer in a solution for forming a first metal oxide film containing a metal source, a first metal oxide film in contact with the dense fuel electrode layer is formed,
A second metal oxide film is formed by contacting a solution for forming a second metal oxide film containing a metal source on the first metal oxide film, and the first metal oxide film and the second metal are formed. The metal oxide film comprising an oxide film is obtained,
The dense fuel electrode layer has a relative density of 90% or more .

  According to the method for producing a solid oxide fuel cell of the present invention, a dense fuel electrode layer is immersed in a metal oxide film forming solution (or a first metal oxide film forming solution) containing a metal source. Since the metal oxide film (or the first metal oxide film) is formed, the metal oxide film can be easily densified without performing heat treatment at high temperature, for example. Thereby, for example, the manufacturing process of the solid oxide fuel cell can be simplified.

  First, a first manufacturing method of the solid oxide fuel cell of the present invention (hereinafter also referred to as “first manufacturing method”) will be described. In the first manufacturing method, a metal oxide film is formed by immersing a dense fuel electrode layer in a metal oxide film forming solution containing a metal source. Thereby, for example, a heat treatment step at a high temperature of 1000 ° C. or higher is not required, and the metal oxide film can be easily densified, so that the manufacturing process can be further simplified. Further, since the metal oxide film is formed on the dense fuel electrode layer, it can be densified more uniformly as compared with the case where it is formed on the porous electrode layer having irregularities on the surface.

  Any metal source may be used as long as it contains the metal constituting the metal oxide film and dissolves in a solvent described later. For example, a metal salt, a metal complex in which an inorganic substance or an organic substance is coordinated with a metal ion, an organometallic compound having a metal-carbon bond in the molecule, or the like can be used. The said metal source may be used individually by 1 type, and may mix and use 2 or more types.

  The metal element constituting the metal source is not particularly limited as long as a metal oxide film having a desired metal composition can be obtained, but Ca, Cr, Sr, Nb, Mo, Sb, Te, Ba, W, Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ag, In, Sn, Ce, Sm, Pb, La, Hf, Sc, Gd, Ga and It is preferably at least one metal element selected from Ta. In the Pourbaille diagram, the metal element is a region present as a metal oxide (hereinafter referred to as “metal oxide region”) or a region present as a metal hydroxide (hereinafter referred to as “metal hydroxide region”). Therefore, it is suitable as a main constituent element of the metal oxide film. More preferably, Zr, Ce, La widely known as electrolyte materials are suitable. The said metal source (1 type or multiple types) may contain 2 or more types of the said metal element. Usually, a plurality of types of metal elements are used in an electrolyte layer for a solid oxide fuel cell.

  Examples of the metal salt include chlorides, nitrates, sulfates, perchlorates, acetates, phosphates, bromates and the like containing the above metal elements. Among these, in the present invention, it is preferable to use chloride, nitrate, and acetate. This is because these compounds are easily available as general-purpose products.

  Specific examples of the metal complex and the organometallic compound include calcium acetylacetonate dihydrate, chromium (III) acetylacetonate, gallium (III) trifluoromethanesulfonate, strontium dipivaloylmethanate, Niobium pentachloride, molybdenyl acetylacetonate, palladium (II) acetylacetonate, antimony (III) chloride, sodium tellurate, barium chloride dihydrate, tungsten (IV) chloride, magnesium diethoxide, aluminum acetylacetonate , Calcium di (methoxyethoxide), calcium gluconate monohydrate, calcium citrate tetrahydrate, calcium salicylate dihydrate, titanium lactate, titanium acetylacetonate, tetraisopropyl titanate, tetranormal butyl titanate, Tra (2-ethylhexyl) titanate, butyl titanate dimer, titanium bis (ethylhexoxy) bis (2-ethyl-3-hydroxyhexoxide), diisopropoxytitanium bis (triethanolamate), dihydroxybis (ammonium lactate) titanium, Diisopropoxytitanium bis (ethyl acetoacetate), titanium peroxo ammonium citrate tetrahydrate, dicyclopentadienyl iron (II), iron (II) lactate trihydrate, iron (III) acetylacetonate, cobalt (II) acetylacetonate, nickel (II) acetylacetonate dihydrate, copper (II) acetylacetonate, copper (II) dipivaloylmethanate, copper (II) ethylacetoacetate, zinc acetylacetonate, Zinc lactate trihydrate, zinc salicylate trihydrate, zinc stearate Strontium dipivaloylmethanate, yttrium dipivaloylmethanate, zirconium tetra-n-butoxide, zirconium (IV) ethoxide, zirconium normal propyrate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate , Zirconium acetylacetonate bisethylacetoacetate, zirconium acetate, zirconium monostearate, penta-n-butoxyniobium, pentaethoxyniobium, pentaisopropoxyniobium, tris (acetylacetonato) indium (III), 2-ethylhexanoic acid Indium (III), tetraethyltin, dibutyltin oxide (IV), tricyclohexyltin (IV) hydroxide, lanthanum acetylacetona Dihydrate, tri (methoxyethoxy) lanthanum, pentaisopropoxytantalum, pentaethoxytantalum, tantalum (V) ethoxide, cerium (III) acetylacetonate, lead (II) citrate trihydrate, cyclohexanebutyric acid Lead etc. can be mentioned. Among these, magnesium diethoxide, aluminum acetylacetonate, calcium acetylacetonate dihydrate, titanium lactate, titanium acetylacetonate, tetraisopropyl titanate, tetranormal butyl titanate, tetra (2) are easily available and easy to handle. -Ethylhexyl) titanate, butyl titanate dimer, diisopropoxytitanium bis (ethyl acetoacetate), iron (II) lactate trihydrate, iron (III) acetylacetonate, zinc acetylacetonate, zinc lactate trihydrate, strontium Dipivaloylmethanate, pentaethoxyniobium, tris (acetylacetonato) indium (III), indium (III) 2-ethylhexanoate, tetraethyltin, dibutyltin oxide (IV), lanthanum acetylacetate Over preparative dihydrate, tri (methoxyethoxy) lanthanum, it is preferable to use a cerium (III) acetylacetonate.

  By appropriately selecting the metal source, for example, a composite metal oxide containing at least one selected from zirconium oxide, cerium oxide, and lanthanum oxide, which is widely known as an electrolyte material for a solid oxide fuel cell. The formed metal oxide film can be formed. Specific examples of such a metal oxide film include YSZ, scandia-stabilized zirconia (hereinafter abbreviated as “ScSZ”), Samaria doped ceria (hereinafter abbreviated as “SDC”), gadolinium doped ceria ( In the following, abbreviated as “GDC”), a metal oxide film made of lanthanum garade or the like can be given. The composite metal oxide preferably has a fluorite-type or perovskite-type crystal structure from the viewpoint of oxide ion conductivity. In order for ions to move in the solid, the solid needs to have lattice defects. That is, ions move (diffuse) while exchanging positions with lattice defects in an ion conductive solid. A metal oxide having a fluorite-type or perovskite-type crystal structure can maintain a stable structure even if it has lattice defects.

  The solvent used in the metal oxide film forming solution is not particularly limited as long as it can dissolve the metal source described above. For example, when the metal source is a metal salt, a lower alcohol having a total carbon number of 5 or less such as methanol, ethanol, isopropanol, n-propanol, butanol, water, toluene, a mixed solvent thereof or the like can be used. When the metal source is a metal complex or an organometallic compound, water, the above-described lower alcohol, toluene, a mixed solvent thereof or the like can be used. In the present invention, the above solvents may be used in combination. For example, a metal complex having low solubility in water but high solubility in an organic solvent and a material having low solubility in an organic solvent but high solubility in water (for example, a reducing agent described later) are used. In the case, a mixed solvent of water and an organic solvent is used to dissolve both of them, and a uniform metal oxide film forming solution can be obtained.

  The concentration of the metal source in the metal oxide film forming solution is usually 0.001 to 10 mol / liter, and preferably 0.01 to 1 mol / liter. If the concentration is less than 0.001 mol / liter, the metal oxide film formation reaction hardly occurs and the desired metal oxide film may not be obtained. If the concentration exceeds 10 mol / liter, precipitation occurs. This is because things may be generated.

  In the present invention, the metal oxide film forming solution may further contain at least one selected from an oxidizing agent and a reducing agent. This is because the deposition reaction of the metal oxide film can be promoted. For example, if the metal oxide film forming solution contains an oxidizing agent, the metal ions dissolved by the metal source are rapidly oxidized, which accelerates the metal oxide film formation reaction. To do. Further, for example, if a reducing agent is contained in the metal oxide film forming solution, it is considered that the reducing agent decomposes and emits electrons, thereby inducing an electrolysis reaction of water (solvent). When water electrolysis occurs, hydroxide ions are generated, which increases the pH of the metal oxide film forming solution and shifts to the metal oxide region or metal hydroxide region in the Pourbaix diagram. Therefore, the film formation reaction of the metal oxide film is promoted.

  The oxidizing agent is not particularly limited as long as it can be dissolved in the above-described solvent and can oxidize a metal ion or the like formed by dissolving the metal source. For example, hydrogen peroxide, sodium nitrite, Examples thereof include potassium nitrite, sodium bromate, potassium bromate, silver oxide, dichromic acid, and potassium permanganate. Among them, hydrogen peroxide and potassium nitrite are preferably used.

  The concentration of the oxidizing agent in the metal oxide film forming solution varies depending on the type of the oxidizing agent, but is usually 0.001 to 1 mol / liter, particularly 0.01 to 0.1 mol / liter. Is preferred. If the concentration is less than 0.001 mol / liter, there is a possibility that the effect of promoting the film formation reaction of the metal oxide film may not be sufficiently exhibited. If the concentration exceeds 1 mol / liter, the concentration increases. This is because a suitable effect cannot be obtained and this is not preferable in terms of cost.

  The reducing agent is not particularly limited as long as it is soluble in the above-described solvent and can release electrons by a decomposition reaction. For example, borane-tert-butylamine complex, borane-N, N diethylaniline. Examples include complexes, borane complexes such as borane-dimethylamine complex and borane-trimethylamine complex, sodium cyanoborohydride, sodium borohydride, etc. Among them, it is preferable to use borane complex.

  The concentration of the reducing agent in the metal oxide film forming solution varies depending on the type of the reducing agent, but is usually 0.001 to 1 mol / liter, particularly 0.01 to 0.1 mol / liter. Is preferred. If the concentration is less than 0.001 mol / liter, there is a possibility that the effect of promoting the film formation reaction of the metal oxide film may not be sufficiently exhibited. If the concentration exceeds 1 mol / liter, the concentration increases. This is because a suitable effect cannot be obtained and this is not preferable in terms of cost.

  Further, the metal oxide film forming solution used in the present invention may contain additives such as an auxiliary ion source and a surfactant.

  The auxiliary ion source reacts with electrons to generate hydroxide ions, and can raise the pH of the metal oxide film forming solution and promote the film forming reaction of the metal oxide film. This is a function of guiding to a metal oxide region or a metal hydroxide region in the Pourbaix diagram. Therefore, the auxiliary ion source is effective when combined with a reducing agent that decomposes by heat and emits electrons. Even if the reducing agent is not contained in the metal oxide film forming solution, oxygen is generated by heating. Can be used alone as an oxidizing agent. In addition, what is necessary is just to set the usage-amount of the said auxiliary ion source suitably according to the metal source etc. to be used.

Such auxiliary ion source, specifically, chlorate ion, perchlorate ion, chlorite ion, hypochlorite ion, bromate ion, hypobromous acid ion, nitrate ion, nitrite ion Ionic species such as These auxiliary ion sources are believed to cause the following reactions in solution.
(Chemical formula 1) ClO ₄ ⁻ + H ₂ O + 2e ⁻ ⇔ ClO ₃ ⁻ + 2OH ⁻
(Chemical Formula 2) ClO ₃ ⁻ + H ₂ O + 2e ⁻ ⇔ ClO ₂ ⁻ + 2OH ⁻
(Chemical Formula 3) ClO ₂ ⁻ + H ₂ O + 2e ⁻ ⇔ ClO ⁻ + 2OH ⁻
(Formula _{^{4) 2ClO - + 2H 2 O}} + 2e - ⇔ Cl 2 + 4OH -
(Formula ^{_{5) BrO 3 - + 2H 2}} O + 4e - ⇔ BrO - + 4OH -
(Of _{^{6) 2BrO - + 2H 2 O}} + 2e - ⇔ Br 2 + 4OH -
(Chemical Formula 7) NO ₃ ⁻ + H ₂ O + 2e ⁻ ＮＯ NO ₂ ⁻ + 2OH ⁻
(Chemical Formula 8) NO ₂ ⁻ + 3H ₂ O + 3e ⁻ ＮＨ NH ₃ + 3OH ⁻

  The surfactant can improve the wettability of the metal oxide film forming solution with respect to the surface of the dense fuel electrode layer and promote the film formation reaction of the metal oxide film. Specific examples of such surfactants include Surfinol 485, Surfinol SE, Surfinol SE-F, Surfinol 504, Surfinol GA, Surfinol 104A, Surfinol 104BC, Surfinol 104PPM, Surfinol 104E. Surfynol series such as Surfinol 104PA (all are trade names manufactured by Nissin Chemical Industry Co., Ltd.), NIKKOL AM301, NIKKOL AM313ON (all are trade names manufactured by Nikko Chemical Co., Ltd.), and the like. In addition, what is necessary is just to set the usage-amount of the said surfactant suitably according to the metal source etc. to be used.

  The dense fuel electrode layer includes nickel oxide and an oxide ion conductor such as a ceramic powder material. Other metal oxides such as iron oxide may be included as necessary. As the oxide ion conductor, one having a fluorite-type or perovskite-type crystal structure can be preferably used. Examples of those having a fluorite-type crystal structure include ceria-based oxides doped with samarium and gadolinium, zirconia-based oxides containing scandium and yttrium, and the like. In addition, examples of those having a perovskite-type crystal structure include lanthanum galide oxides doped with strontium and magnesium. Note that the mixture of the ceramic powder material made of oxide ion conductor and nickel oxide may be a mixture of both, or a ceramic powder modified with nickel oxide. Good. Moreover, the ceramic powder material mentioned above may be used individually by 1 type, and may mix and use 2 or more types. The thickness of the dense fuel electrode layer is usually 5 to 50 μm.

  The method for forming the dense fuel electrode layer is not particularly limited. For example, the dense fuel electrode layer can be formed by mixing nickel oxide powder and oxide ion conductor powder, forming a plate shape by press molding, and sintering this. The dense fuel electrode layer thus formed usually has a relative density of 90% or more. This relative density can be measured by a measuring method such as a gas adsorption method.

  The dense fuel electrode layer preferably has a surface roughness Ra of 0.2 μm or less, and more preferably 0.1 μm or less. This is because a metal oxide film can be formed on a flat surface, so that a more uniform metal oxide film (electrolyte layer) can be obtained. The surface roughness Ra can be measured, for example, by a measuring method based on JIS B0601. The surface roughness Ra of the dense fuel electrode layer is usually 0.01 μm or more.

  In the dense fuel electrode layer, voids are generated in the region occupied by oxygen by reduction of nickel oxide during power generation, and the fuel electrode layer has a porosity of about 10 to 50%. That is, the dense fuel electrode layer serves as a fuel gas diffusion layer during power generation.

  In the present invention, when the dense fuel electrode layer is immersed in the metal oxide film forming solution, at least one (preferably both) of the metal oxide film forming solution and the dense fuel electrode layer is 10 ° C. You may hold | maintain at the above temperature. This is because the deposition reaction of the metal oxide film can be promoted. In order to further promote the film formation reaction of the metal oxide film, it is preferable to heat to a temperature of 50 ° C. or higher, and more preferably to a temperature of 60 ° C. or higher. In this case, the heating temperature is preferably set to a temperature not higher than the boiling point of the metal oxide film forming solution from the viewpoint of workability. For example, when the metal oxide film forming solution contains the oxidizing agent or reducing agent described above, at least one (preferably both) of the metal oxide film forming solution and the dense fuel electrode layer is usually 10 to 10. What is necessary is just to hold | maintain in the range of 100 degreeC, and it is preferable to heat to the range of 50-90 degreeC from a viewpoint of productivity.

  In the present invention, when forming the metal oxide film by immersing the dense fuel electrode layer in the metal oxide film forming solution, the dense fuel electrode layer and the metal oxide film forming solution are in contact with each other. A bubble-like oxidizing gas may be brought into contact with the portion. This is because oxidation of metal ions or the like formed by dissolving the metal source is rapidly performed, so that the film formation reaction of the metal oxide film is promoted. Such an oxidizing gas is not particularly limited as long as it can oxidize metal ions and the like obtained by dissolving the metal source. For example, oxygen, ozone, nitrous acid gas, nitrogen dioxide, chlorine dioxide In particular, oxygen and ozone are preferably used, and ozone is particularly preferably used. This is because it is easy to obtain industrially and can realize cost reduction. Moreover, the method for introducing the bubble-like oxidizing gas described above is not particularly limited, and examples thereof include a method using a bubbler. By using a bubbler, the contact area between the portion where the dense fuel electrode layer and the metal oxide film forming solution are in contact with the oxidizing gas can be increased, and the metal oxide film can be formed. This is because the film speed can be improved efficiently. As such a bubbler, a general bubbler can be used, and examples thereof include a Naflon bubbler (manufactured by ASONE). In addition, the oxidizing gas can be normally supplied from a gas cylinder to the metal oxide film forming solution, and ozone can be supplied from the ozone generator to the metal oxide film forming solution.

  In the present invention, when forming the metal oxide film by immersing the dense fuel electrode layer in the metal oxide film forming solution, the dense fuel electrode layer and the metal oxide film forming solution include: The contacted portion may be irradiated with ultraviolet rays. By irradiating with ultraviolet rays, it is considered that the electrolysis reaction of water can be promoted or the decomposition of the reducing agent described above can be promoted. This is because the film formation reaction of the film can be promoted. Further, by irradiating with ultraviolet rays, hydroxide ions can be generated from the auxiliary ion source described above, and the crystallinity of the obtained metal oxide film can be improved. The ultraviolet light includes near ultraviolet light having a wavelength of 470 nm or less.

  The ultraviolet irradiation method is not particularly limited as long as it is a method of irradiating the contact portion between the dense fuel electrode layer surface and the metal oxide film forming solution. For example, as shown in FIG. A method of immersing the dense fuel electrode layer 21 in the metal oxide film forming solution 22 and irradiating ultraviolet rays UV from the liquid surface side of the metal oxide film forming solution 22 is exemplified. In this case, from the viewpoint of accurately irradiating ultraviolet rays UV to the contact portion between the surface 21a of the dense fuel electrode layer 21 and the metal oxide film forming solution 22, the surface 21a irradiated with the ultraviolet rays UV is subjected to metal oxidation. It is preferable that the distance to the liquid surface of the substance film forming solution 22 is short. Moreover, according to this method, the thickness of the metal oxide film formed in contact with the surface 21a can be increased. In this case, if the air electrode layer is formed on the metal oxide film formed in contact with the surface 21a, the gap between the electrode layers can be sufficiently maintained, so that the contact between the fuel gas and the air is ensured. Can be prevented.

The wavelength of the ultraviolet light is usually 185 to 470 nm, and preferably 185 to 260 nm in order to further promote the film forming reaction. The intensity of the ultraviolet light is usually 1 to 20 mW / cm ² , and preferably 5 to 15 mW / cm ² in order to further promote the film forming reaction. As an ultraviolet irradiation apparatus for performing such ultraviolet irradiation, for example, a commercially available ultraviolet irradiation apparatus can be used, and specifically, HB400X-21 manufactured by SEN Special Light Source Co., Ltd. can be used.

  In the present invention, the obtained metal oxide film may be washed and dried. The cleaning of the metal oxide film is performed to remove impurities present on the surface of the metal oxide film. Examples of the cleaning method include a method of cleaning using a solvent used in the metal oxide film forming solution. In addition, when the metal oxide film is dried, it may be dried by leaving it at room temperature, or may be dried in a heating apparatus such as an oven.

  When producing a solid oxide fuel cell, after forming a metal oxide film in contact with the dense fuel electrode layer by the above-described method, the air electrode layer is formed on the metal oxide film (electrolyte layer). Form. The air electrode layer can be formed by, for example, a known method. Specifically, after forming a paste using an electrode material, a binder, and a solvent, the paste is applied on an electrolyte layer by a coating method such as a screen printing method or a doctor blade method, and these are sintered to form. be able to.

As an electrode material constituting the air electrode layer, for example, a metal oxide having a perovskite crystal structure can be used. Specifically, (Sm, Sr) CoO ₃ , (La, Sr) MnO ₃ , (La, Sr) CoO ₃ , (La, Sr) (Fe, Co) O ₃ , (La, Sr) (Fe, Co , Ni) O _{3 and the} like, and (La, Sr) MnO ₃ is preferably used from the viewpoint of stability in an oxidizing atmosphere. One kind of the metal oxides described above may be used alone, or two or more kinds may be mixed and used. Moreover, noble metals, such as platinum, ruthenium, and palladium, can also be used as a material for forming the air electrode layer. The porosity of the air electrode layer is usually 20 to 50%, preferably 30 to 40%. The thickness of the air electrode layer is usually 5 to 50 μm.

  Next, a second manufacturing method of the solid oxide fuel cell of the present invention (hereinafter also referred to as “second manufacturing method”) will be described. In the second production method, first, (1) a first metal oxide that comes into contact with a dense fuel electrode layer by immersing the dense fuel electrode layer in a solution for forming a first metal oxide film containing a metal source. A film is formed. Next, (2) a second metal oxide film is formed by bringing a second metal oxide film forming solution containing a metal source into contact with the first metal oxide film, thereby forming the first metal oxide film. A metal oxide film composed of the material film and the second metal oxide film is obtained. As a result, the same effects as the first manufacturing method described above can be exhibited, and the second metal oxide film can be formed according to the crystal nucleus and crystal structure of the first metal oxide film. In addition, a sufficiently dense metal oxide film can be obtained. Thereby, contact with fuel gas and air can be prevented reliably. Even when the obtained second metal oxide film is made of a material that is difficult to form directly on the dense fuel electrode layer, the second metal oxide film is interposed on the dense fuel electrode layer via the first metal oxide film. An oxide film can be formed. Or it becomes possible to improve adhesiveness.

  As the first metal oxide film forming solution and the second metal oxide film forming solution, the same metal oxide film forming solution used in the first manufacturing method described above can be used. Further, the second metal oxide film forming solution may not contain an oxidizing agent or a reducing agent, and may be a solution obtained by dissolving the above metal source in a solvent. Moreover, the said 1st metal oxide film formation solution and the said 2nd metal oxide film formation solution may use the same thing, and may each use a different thing. The first metal oxide film obtained from the first metal oxide film forming solution when the first metal oxide film forming solution is different from the second metal oxide film forming solution. It is preferable to select each solution composition so that the crystal system of the second metal oxide film and the crystal system of the second metal oxide film obtained by the second metal oxide film forming solution are approximated (or matched). . Note that, in the second manufacturing method, the step (1) is the same as the first manufacturing method described above, and therefore, only the step (2) will be described below, and redundant description will be omitted.

  The method for contacting the second metal oxide film forming solution onto the first metal oxide film in the step (2) is not particularly limited, but the second metal oxide film forming solution and the first metal oxide film forming solution It is preferable that the method does not decrease the temperature of the first metal oxide film when it comes into contact with the metal oxide film. This is because if the temperature of the first metal oxide film is lowered, the film formation reaction is difficult to occur, and a desired second metal oxide film may not be obtained. Examples of the method of not lowering the temperature of the first metal oxide film include a method of bringing the second metal oxide film forming solution into contact with the first metal oxide film as droplets. At this time, the droplets preferably have a small diameter of, for example, about 0.001 to 1000 μm. If the diameter of the droplet is within the above range, the solvent of the second metal oxide film forming solution can be instantly evaporated, and the temperature drop of the first metal oxide film can be suppressed. This is because a uniform second metal oxide film can be obtained because of the small diameter.

  The method of bringing the droplet of the second metal oxide film forming solution into contact with the first metal oxide film is not particularly limited, but specifically, the second metal oxide film forming solution is used. A method of bringing the second metal oxide film forming solution into contact with the first metal oxide film by spraying, or a first metal oxide film in a space in which the second metal oxide film forming solution is mist-shaped. Examples include a method of bringing the second metal oxide film-forming solution into contact with the first metal oxide film by passing the material film.

  Examples of the method of spraying the second metal oxide film forming solution onto the first metal oxide film include a method of spraying using a spray device or the like. When spraying using the said spray apparatus etc., the diameter of a droplet is 0.001-1000 micrometers normally, It is preferable that it is 0.01-100 micrometers especially. This is because if the diameter of the droplet is within the above range, the temperature drop of the first metal oxide film can be suppressed, and a uniform second metal oxide film can be obtained.

  Further, the spray gas of the spray device is not particularly limited as long as it does not inhibit the formation of the second metal oxide film, and examples thereof include air, nitrogen, argon, helium, oxygen, and the like. Of these, nitrogen, argon, and helium, which are inert gases, are preferable. In addition, the spray amount of the second metal oxide film forming solution is usually 0.001 to 1 liter / min. In order to further improve the denseness of the second metal oxide film, 0.001 to It is preferably 0.05 liter / min. Under the present circumstances, the thickness of the 2nd metal oxide film formed can be arbitrarily adjusted by spraying repeatedly. The thickness of the metal oxide film formed by the present invention is usually 10 nm to 100 μm, preferably 10 nm to 10 μm, more preferably 100 nm to 5 μm, and most preferably 100 nm to 1 μm. is there. When the said thickness is less than 10 nm, there exists a possibility that a fuel electrode layer and an air electrode layer may contact. On the other hand, if the thickness exceeds 100 μm, the oxide ion conductivity of the metal oxide film may be reduced. The spray device may be a fixed device, a movable device, a device that ejects the solution by rotation, a device that ejects the solution by pressure, or the like. As such a spray device, a commonly used spray device can be used. For example, a hand spray (manufactured by ASONE), an ultrasonic nepriser (manufactured by OMRON), or the like can be used.

  In the present invention, for example, when the second metal oxide film is formed by using the above-described method of spraying the second metal oxide film forming solution onto the first metal oxide film, the resulting second metal oxide film is obtained. And an aggregate of crystals having a columnar structure in which crystals grow in the stacking direction. In such a second metal oxide film, the crystal is filled with high density, so that the second metal oxide film can be further densified. Furthermore, since the grain boundaries that hinder the diffusion of oxide ions are reduced, the oxide ion conductivity of the second metal oxide film can be improved. In order to ensure the effect, the crystal length in the stacking direction of the second metal oxide film in the crystal is set to a crystal diameter in a direction perpendicular to the stacking direction of the second metal oxide film in the crystal. It is preferable to select the material and the solvent so that the value divided by 2 is 2 or more.

  When using a method in which the first metal oxide film is passed through a space in which the second metal oxide film forming solution is made into a mist, the diameter of the droplet is usually 0.001 to 1000 μm. It is preferable that it is 01-100 micrometers. This is because if the diameter of the droplet is within the above range, the temperature drop of the first metal oxide film can be suppressed, and a uniform second metal oxide film can be obtained. At this time, the thickness of the second metal oxide film to be formed can be arbitrarily adjusted by allowing the dense fuel electrode layer to pass through or repeatedly passing, for example, the thickness of the obtained metal oxide film is within the above-mentioned range. Can be controlled.

  In the present invention, in order to promote the film formation reaction of the second metal oxide film, when the second metal oxide film forming solution is brought into contact with the first metal oxide film, the temperature is higher than the metal oxide film forming temperature. The first metal oxide film may be heated. Here, the “metal oxide film formation temperature” is the lowest temperature at which the metal element constituting the metal source is combined with oxygen to form the second metal oxide film on the first metal oxide film. That is. The metal oxide film formation temperature varies greatly depending on the type of the metal source and the composition of the second metal oxide film formation solution such as a solvent, and is usually in the range of 300 to 1000 ° C. In particular, from the viewpoint of productivity, it is preferable to select the type of metal source, the solvent, and the like so as to be within a range of 400 to 700 ° C. On the other hand, when the second metal oxide film forming solution contains an oxidizing agent or a reducing agent, the metal oxide film forming temperature is usually in the range of 150 to 800 ° C., particularly from the viewpoint of productivity. It is preferable to select the type of metal source, the solvent, and the like so as to be within the range of 300 to 500 ° C.

  The metal oxide film formation temperature can be measured by the following method. First, a second metal oxide film forming solution containing a desired metal source is prepared. Next, the heating temperature of the first metal oxide film is changed, and the second metal oxide film forming solution is brought into contact with the first metal oxide film to form a second metal oxide film. Among the heating temperatures of the first metal oxide film that can be measured, the lowest heating temperature is measured. This minimum heating temperature can be referred to as a “metal oxide film forming temperature” in this specification. At this time, whether or not the second metal oxide film is formed is determined when the obtained second metal oxide film has crystallinity, for example, a result obtained by an X-ray diffraction apparatus (RINT-1500, manufactured by Rigaku). In the case where the obtained second metal oxide film is an amorphous film, it can be judged from the result obtained by, for example, a photoelectron spectroscopic analyzer (manufactured by VG Scientific, ESCALAB 200i-XL).

  Further, the heating method of the first metal oxide film is not particularly limited, and examples thereof include a heating method using a hot plate, an oven, a firing furnace, an infrared lamp, a hot air blower, etc. Use of a hot plate is preferable because the temperature of the first metal oxide film can be reliably maintained at a desired temperature. In addition, when heating a 1st metal oxide film, you may heat with the said dense fuel electrode layer, and you may heat only a 1st metal oxide film.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate. 1A and 1B and FIGS. 2A to 2C to be referred to are schematic process diagrams showing a method for manufacturing a solid oxide fuel cell according to an embodiment of the present invention.

  First, a metal source and a reducing agent, for example, are dissolved in a solvent such as water to prepare a first metal oxide film forming solution 1a (see FIG. 1A). Then, as shown in FIG. 1A, the dense fuel electrode layer 11 containing nickel oxide is immersed in the first metal oxide film forming solution 1a. Thereby, as shown in FIG. 1B, the first metal oxide film 12 a is formed along the surface 11 a of the dense fuel electrode layer 11. Thereafter, the dense fuel electrode layer 11 covered with the first metal oxide film 12a is taken out from the first metal oxide film forming solution 1a.

  Next, as shown in FIG. 2A, in a state where the first metal oxide film 12a and the dense fuel electrode layer 11 are heated to a temperature higher than the metal oxide film formation temperature by a hot plate (not shown), for example, 2, the second metal oxide film forming solution 1b (for example, the same composition as the first metal oxide film forming solution 1a) is sprayed onto the first metal oxide film 12a. As a result, as shown in FIG. 2B, a second metal oxide film 12b is formed on the first metal oxide film 12a, and a metal oxide film composed of the first metal oxide film 12a and the second metal oxide film 12b is formed. A material film 12 is obtained.

  Subsequently, as shown in FIG. 2C, an air electrode layer 13 is formed on the metal oxide film (electrolyte layer) 12 using means such as a screen printing method, and a solid oxide fuel cell (single cell) 10 is formed. Is obtained.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, after forming the first metal oxide film 12a, the air electrode layer 13 may be formed on the first metal oxide film 12a without forming the second metal oxide film 12b. Alternatively, after forming the first metal oxide film 12a, a slurry may be applied by a known method, and this may be fired to form a second metal oxide film. Alternatively, the dense fuel electrode layer 11 may be immersed in the first metal oxide film forming solution 1a in a state where the surface other than the surface facing the air electrode layer 13 is masked. As a result, the first metal oxide film 12 a can be formed only on the surface facing the air electrode layer 13.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

(Example)
In this example, a single cell having the structure shown in FIG. 2C was manufactured. First, NiO powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm), and SDC (Ce: Sm: O = 0.8: 0.2: 1.9) powder (particle size range: 1 10 μm, average particle size: 0.1 μm) was added to ethanol so that the mass ratio (NiO: SDC) was 70:30, and these were mixed while being pulverized in ethanol. Next, these were dried and the ethanol was sufficiently volatilized, then formed by a uniaxial press and cut (trimmed) to a predetermined size by a ceramic cutter. And this was sintered at 1400 degreeC for 5 hours, and the dense fuel electrode board | substrate (thickness: 0.5 mm) used as a dense fuel electrode layer was produced.

  Subsequently, cerium (III) nitrate (manufactured by Kanto Chemical Co., Inc.), gadolinium nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) and borane-dimethylamine complex (manufactured by Kanto Chemical Co., Ltd.) as a reducing agent were each added at a concentration of 0.03 mol / A first metal oxide film-forming solution was prepared by dissolving in a mixed solvent consisting of ethanol and water so as to be 1 liter, 0.0045 mol / liter, and 0.05 mol / liter. The mixed solvent used had a volume ratio (ethanol: water) of 50:50. Then, the dense fuel electrode substrate is dipped in the first metal oxide film forming solution (70 ° C.) for 5 hours to cover the surface of the dense fuel electrode substrate, and the first metal made of GDC is formed. An oxide film was obtained.

  Next, cerium (III) acetylacetonate (manufactured by Kanto Chemical Co., Inc.) and gadolinium acetate (manufactured by Wako Pure Chemical Industries, Ltd.) were adjusted so that the respective concentrations were 0.1 mol / liter and 0.03 mol / liter. A second metal oxide film forming solution was prepared by dissolving in a mixed solvent consisting of toluene, isopropanol, ethanol, and methyl ethyl ketone. The mixed solvent used had a volume ratio (toluene: isopropanol: ethanol: methyl ethyl ketone) of 50: 20: 20: 10. Then, the second metal oxide film-forming solution (100 ml) is sprayed onto the first metal oxide film heated to 400 ° C. by hand spray (manufactured by ASONE Co., Ltd.), and the first metal oxide film A second metal oxide film made of GDC was formed thereon, and an electrolyte layer (thickness: 5 μm) made of the first metal oxide film and the second metal oxide film was obtained. The spray amount of the second metal oxide film forming solution was 0.005 liter / min.

Subsequently, (Sm, Sr) CoO ₃ (Sm: Sr: Co: O = 0.5: 0.5: 1: 3) powder (particle size range: 0.1 to 10 μm, average particle size: 3 μm) and A paste is prepared by adding a cellulose binder resin to diethylene glycol monobutyl ether acetate so that the mass ratio ((Sm, Sr) CoO ₃ : binder resin) is 80:20, and this paste is screen-printed on the electrolyte layer. Then, these were sintered at 1200 ° C. for 5 hours to form an air electrode layer (thickness: 30 μm), thereby producing a single cell of a solid oxide fuel cell.

(Comparative example)
As a comparative example, a single cell was produced by the method described below.

  First, NiO powder (particle size range: 0.01 to 10 μm, average particle size: 1 μm), SDC (Ce: Sm: O = 0.8: 0.2: 1.9) powder (particle size range: 1 to 1) 10 μm, average particle diameter: 0.1 μm) and acetylene black were added to ethanol so that the mass ratio (NiO: SDC: acetylene black) was 45: 50: 5, and these were mixed while being pulverized in ethanol. Next, these were dried and the ethanol was sufficiently volatilized, then formed by a uniaxial press and cut (trimmed) to a predetermined size by a ceramic cutter. And this was sintered at 1400 degreeC for 5 hours, and the porous fuel electrode board | substrate (thickness: 0.5 mm) used as a porous electrode layer was produced.

Next, the mass ratio (YSZ) of YSZ (Y: Zr: O = 0.08: 1: 2) powder (particle size range: 0.1 to 1 μm, average particle size: 0.5 μm) and cellulose binder resin are used. : Cellulose-based binder resin) was added to diethylene glycol monobutyl ether acetate so as to be 95: 5 to prepare a paste. The viscosity of the paste at this time was 5 × 10 ⁵ mPa · s. Next, the paste is applied to the porous fuel electrode substrate by a screen printing method, dried at 130 ° C. for 5 minutes, sintered at 1200 ° C. for 1 hour, and an electrolyte layer made of YSZ (the porous layer) Thickness on the fuel electrode substrate: 5 μm).

Subsequently, (Sm, Sr) CoO ₃ (Sm: Sr: Co: O = 0.5: 0.5: 1: 3) powder (particle size range: 0.1 to 10 μm, average particle size: 3 μm) and Cellulose binder resin is added to diethylene glycol monobutyl ether acetate so that the mass ratio ((Sm, Sr) CoO ₃ : binder resin) is 80:20, and a paste is prepared. After coating on the layer, these were sintered at 1200 ° C. for 5 hours to form an air electrode layer (thickness: 30 μm) to obtain a single cell of a solid oxide fuel cell.

(Evaluation of battery performance)
The battery performance of each single cell described above was evaluated by the following method.

  First, as shown in FIG. 4, the single cell 92 was sandwiched between a pair of alumina pipes 91 and 91 each having an air supply path 91a and an exhaust path 91b. At this time, a glass seal 93 was interposed between the single cell 92 and the alumina tube 91 in order to prevent leakage of the supplied gas. Next, after raising the temperature in the alumina tube 91 to 800 ° C. in the atmosphere, hydrogen is supplied from the fuel electrode side of the single cell 92 at 100 ml / min, and air is supplied from the air electrode side at 200 ml / min. The open circuit voltage (OCV) was then measured. As a result, the OCV of the example was 1140 mV, and the OCV of the comparative example was 320 mV. In the comparative example, since the electrolyte layer is insufficiently dense, it is considered that the open circuit voltage is reduced by the gas leak. On the other hand, in the examples, a large drop in the open circuit voltage was not recognized, and the denseness was ensured.

A and B are schematic process diagrams showing a method for manufacturing a solid oxide fuel cell according to an embodiment of the present invention. A to C are schematic process diagrams illustrating a method for producing a solid oxide fuel cell according to an embodiment of the present invention. It is explanatory drawing which shows the process of forming a metal oxide film in the manufacturing method of the solid oxide fuel cell which concerns on other embodiment of this invention. It is a schematic diagram which shows the evaluation method of battery performance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Solution for forming first metal oxide film 1b Solution for forming second metal oxide film 2 Spray device 10 Solid oxide fuel cell (single cell)
DESCRIPTION OF SYMBOLS 11 Dense fuel electrode layer 11a Surface 12 Metal oxide film 12a 1st metal oxide film 12b 2nd metal oxide film 13 Air electrode layer 21 Dense fuel electrode layer 22 Metal oxide film formation solution UV UV 91 Alumina tube 91a Supply Air path 91b Exhaust path 92 Single cell 93 Glass seal

Claims (17)

A method for producing a solid oxide fuel cell comprising a dense fuel electrode layer containing nickel oxide and an electrolyte layer made of a metal oxide film formed on the dense fuel electrode layer,
The metal oxide film is formed by immersing the dense fuel electrode layer in a metal oxide film forming solution containing a metal source,
The method for producing a solid oxide fuel cell, wherein the dense fuel electrode layer has a relative density of 90% or more.   The method for producing a solid oxide fuel cell according to claim 1, wherein the metal oxide film forming solution further includes at least one selected from an oxidizing agent and a reducing agent.   The metal oxide film forming solution is at least selected from chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromite ions, nitrate ions and nitrite ions. The method for producing a solid oxide fuel cell according to claim 1 or 2, further comprising one ionic species.   2. When immersing the dense fuel electrode layer in the metal oxide film forming solution, at least one of the metal oxide film forming solution and the dense fuel electrode layer is maintained at a temperature of 10 ° C. or higher. A method for producing a solid oxide fuel cell as described in 1).   When immersing the dense fuel electrode layer in the metal oxide film forming solution, at least one of the metal oxide film forming solution and the dense fuel electrode layer is less than the boiling point of the metal oxide film forming solution. The method for producing a solid oxide fuel cell according to claim 4, wherein the solid oxide fuel cell is heated to a temperature of 5 μm. A method for producing a solid oxide fuel cell comprising a dense fuel electrode layer containing nickel oxide and an electrolyte layer made of a metal oxide film formed on the dense fuel electrode layer,
By immersing the dense fuel electrode layer in a solution for forming a first metal oxide film containing a metal source, a first metal oxide film in contact with the dense fuel electrode layer is formed,
A second metal oxide film is formed by contacting a solution for forming a second metal oxide film containing a metal source on the first metal oxide film, and the first metal oxide film and the second metal are formed. The metal oxide film comprising an oxide film is obtained,
The method for producing a solid oxide fuel cell, wherein the dense fuel electrode layer has a relative density of 90% or more.   The solid oxide according to claim 6, wherein at least one of the first metal oxide film forming solution and the second metal oxide film forming solution further includes at least one selected from an oxidizing agent and a reducing agent. Of manufacturing a fuel cell.   At least one of the first metal oxide film forming solution and the second metal oxide film forming solution is a chlorate ion, a perchlorate ion, a chlorite ion, a hypochlorite ion, or a bromate ion. The method for producing a solid oxide fuel cell according to claim 6 or 7, further comprising at least one ion species selected from hypobromite ions, nitrate ions and nitrite ions.   When immersing the dense fuel electrode layer in the first metal oxide film forming solution, at least one of the first metal oxide film forming solution and the dense fuel electrode layer is maintained at a temperature of 10 ° C. or higher. A method for producing a solid oxide fuel cell according to claim 6.   When immersing the dense fuel electrode layer in the first metal oxide film forming solution, at least one of the first metal oxide film forming solution and the dense fuel electrode layer is used as the first metal oxide film. The method for producing a solid oxide fuel cell according to claim 9, wherein the solid oxide fuel cell is heated to a temperature not higher than the boiling point of the forming solution.   When the second metal oxide film forming solution is brought into contact with the first metal oxide film, the metal element constituting the metal source is combined with oxygen to form the second metal oxide film on the first metal oxide film. The method for producing a solid oxide fuel cell according to claim 6, wherein the first metal oxide film is heated to a temperature equal to or higher than a minimum temperature at which the metal oxide film is formed.   By spraying the second metal oxide film forming solution onto the first metal oxide film, the second metal oxide film forming solution is brought into contact with the first metal oxide film to form the first metal oxide film. The method for producing a solid oxide fuel cell according to claim 6 or 11, wherein a two-metal oxide film is formed. The solid oxide fuel cell according to claim 1 or 6 , wherein the metal oxide film is composed of a composite metal oxide containing at least one selected from zirconium oxide, cerium oxide, and lanthanum oxide. Method. The method of manufacturing a solid oxide fuel cell according to claim 13 , wherein the composite metal oxide has a fluorite-type or perovskite-type crystal structure . The solid oxide according to any one of claims 1, 4, 5, 6, 9, and 10, wherein the dense fuel electrode layer further includes an oxide ion conductor having a fluorite-type or perovskite-type crystal structure . Of manufacturing a fuel cell. The method for producing a solid oxide fuel cell according to claim 1, wherein the metal oxide film has a thickness of 10 nm to 100 μm . The method for manufacturing a solid oxide fuel cell according to any one of claims 1, 4 , 5 , 6 , 9 , 10 , and 15, wherein the dense fuel electrode layer has a surface roughness Ra of 0.2 µm or less. .

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