JP2007258166A - Manufacturing method of solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid oxide fuel cell in which a metal oxide membrane comprising an electrolyte layer can be easily compacted. <P>SOLUTION: The manufacturing method of a solid oxide fuel cell (10) having an elaborate fuel electrode layer (11) containing a nickel oxide and an electrolyte layer composed of a metal oxide membrane (12) formed on the elaborate fuel electrode layer (11) includes a process in which a metal oxide membrane forming solvent (1) containing a metal source is made to contact with the heated elaborate fuel electrode layer (11) to form the metal oxide membrane (12). <P>COPYRIGHT: (C)2008,JPO&INPIT

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 Japanese Patent Laid-Open No. 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 bringing a metal oxide film-forming solution containing a metal source into contact with the heated dense fuel electrode layer.

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:
The metal oxide film is formed by bringing a sol for forming a metal oxide film containing a metal source into contact with the heated dense fuel electrode layer.

  According to the method for producing a solid oxide fuel cell of the present invention, a metal oxide film-forming solution containing a metal source or a metal oxide film-forming sol is brought into contact with a heated dense fuel electrode layer to form a metal. Since the oxide film is formed, for example, the metal oxide film can be easily densified without performing heat treatment at a high temperature. Thereby, for example, the manufacturing process of the solid oxide fuel cell can be simplified.

  In the method for producing a solid oxide fuel cell according to the present invention, a metal oxide film-forming solution containing a metal source or a metal oxide film-forming sol is brought into contact with a heated dense fuel electrode layer to thereby form a metal oxide. A film is formed. 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. 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. 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”) in the Pourbaille diagram. 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, lower alcohols having a total carbon number of 5 or less, such as methanol, ethanol, isopropanol, n-propanol, and butanol, water, toluene, a mixed solvent thereof and 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, when a reducing agent is contained in the metal oxide film forming solution, it is considered that this reducing agent decomposes and emits electrons, thereby inducing an electrolysis reaction of water (solvent). When water electrolysis occurs, hydroxide ions are generated, which raises the pH of the metal oxide film forming solution and shifts to the metal oxide region or metal hydroxide region in the Pourbaix diagram. 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.

Specific examples of such auxiliary ion sources include chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromate ions, nitrate ions, nitrite ions, etc. Can be mentioned. 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.

  As a solvent for the metal oxide film forming sol, a solvent capable of hydrolyzing a metal source is preferable. For example, a solvent containing an alcohol such as ethanol is preferable. Other conditions (for example, additives) of the metal oxide film forming sol are the same as those of the metal oxide film forming solution. In addition, as a metal source hydrolyzed, the metal alkoxide containing the metal which comprises the said metal oxide film is preferable.

  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.

  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.

  Next, a method for contacting the metal oxide film forming solution or the metal oxide film forming sol (hereinafter referred to as “metal oxide film forming liquid”) on the dense fuel electrode layer in the present invention will be described. The contact method in the present invention is not particularly limited, but is preferably a method that does not lower the temperature of the dense fuel electrode layer when the metal oxide film forming liquid and the dense fuel electrode layer are in contact with each other. . This is because when the temperature of the dense fuel electrode layer is lowered, the film formation reaction is difficult to occur, and a desired metal oxide film may not be obtained. Examples of a method that does not lower the temperature of the dense fuel electrode layer include a method of bringing a metal oxide film forming liquid into contact with the dense fuel electrode layer 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 metal oxide film forming solution can be instantly evaporated, and the temperature drop of the dense fuel electrode layer can be suppressed, and the droplet diameter is small. This is because a uniform metal oxide film can be obtained.

  The method of bringing the metal oxide film forming liquid droplets into contact with the dense fuel electrode layer is not particularly limited. Specifically, the metal oxide film forming liquid is sprayed to form the dense fuel electrode layer. A method of bringing the metal oxide film forming liquid into contact therewith, or passing the dense fuel electrode layer through a space in which the metal oxide film forming liquid is made into a mist, thereby allowing the metal oxide film to be formed on the dense fuel electrode layer. The method etc. which make a forming liquid contact are mentioned. In the present invention, the method for contacting the metal oxide film forming liquid onto the dense fuel electrode layer may be a method other than the method for bringing the metal oxide film forming liquid into contact with the dense fuel electrode layer as droplets. . For example, the dense fuel electrode layer surface may be brought into direct contact with the surface of the metal oxide film forming liquid.

  Examples of the method of spraying the metal oxide film forming liquid onto the dense fuel electrode layer 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 dense fuel electrode layer can be suppressed and a uniform metal oxide film can be obtained.

  The spray gas of the spray device is not particularly limited as long as it does not inhibit the formation of the metal oxide film, and examples thereof include air, nitrogen, argon, helium, oxygen and the like. Active gases such as nitrogen, argon and helium are preferred. Further, the injection amount of the metal oxide film forming liquid is usually 0.001 to 1 liter / min, and 0.001 to 0.05 liter / min in order to further improve the denseness of the metal oxide film. It is preferably min. At this time, the thickness of the formed metal oxide film 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, when the thickness exceeds 100 μm, the oxide ion conductivity may be lowered. 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 metal oxide film is formed by using the above-described method of spraying the metal oxide film forming liquid onto the dense fuel electrode layer, the obtained metal oxide film has a columnar shape in which crystals are grown in the stacking direction. It includes a collection of crystals having a structure. In such a metal oxide film, the crystal is filled with high density, so that the 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 metal oxide film can be improved. In order to exert the above-mentioned effect reliably, a value obtained by dividing the crystal length in the stacking direction of the metal oxide film in the crystal by the crystal diameter in a direction perpendicular to the stacking direction of the metal oxide film in the crystal. However, it is preferable to select a material and a solvent so that it becomes 2 or more.

  When using a method in which a dense fuel electrode layer is passed through a mist-like space in which the metal oxide film forming liquid is formed, the diameter of the droplets is usually 0.001 to 1000 μm, particularly 0.01 to 100 μm. It is preferable. This is because if the diameter of the droplet is within the above range, the temperature drop of the dense fuel electrode layer can be suppressed and a uniform metal oxide film can be obtained. At this time, the thickness of the formed metal oxide film can be arbitrarily adjusted by allowing the dense fuel electrode layer to pass through or repeatedly passing, for example, controlling the thickness of the obtained metal oxide film within the above-mentioned range. can do.

  In the present invention, in order to promote the film formation reaction of the metal oxide film, the dense fuel electrode layer is heated when the metal oxide film forming liquid is brought into contact with the dense fuel electrode layer. For example, the dense fuel electrode layer may be heated to the metal oxide film formation temperature or higher. Here, the “metal oxide film forming temperature” is the lowest temperature at which the metal element constituting the metal source is combined with oxygen to form a metal oxide film on the dense fuel electrode layer. . The metal oxide film forming temperature varies greatly depending on the type of metal source and the composition of the metal oxide film forming liquid 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 metal oxide film forming liquid contains an oxidizing agent or a reducing agent, the metal oxide film forming temperature is usually in the range of 150 to 800 ° C., and particularly from the viewpoint of productivity, 300 to 500. It is preferable to select the type of metal source, the solvent, and the like so as to be within the range of ° C.

  The metal oxide film formation temperature can be measured by the following method. First, a metal oxide film forming liquid containing a desired metal source is prepared. Next, the metal oxide film is formed by bringing the metal oxide film forming liquid into contact with the dense fuel electrode layer while changing the surface temperature of the dense fuel electrode layer by heating the dense fuel electrode layer. Among the surface temperatures of the dense fuel electrode layer that can be measured, the lowest surface temperature is measured. This minimum surface temperature can be referred to as a “metal oxide film forming temperature” in the present specification. At this time, whether or not the metal oxide film is formed is determined from the result obtained by, for example, an X-ray diffraction apparatus (Rigaku, RINT-1500) when the obtained metal oxide film has crystallinity, When the obtained metal oxide film is an amorphous film, it can be determined from, for example, a result obtained by a photoelectron spectroscopic analyzer (manufactured by V. G. Scientific, ESCALAB 200i-XL).

  Further, the heating method of the dense fuel electrode layer is not particularly limited, and examples thereof include a heating method using a hot plate, oven, firing furnace, infrared lamp, hot air blower, etc. Is preferable because the temperature of the dense fuel electrode layer can be reliably maintained at a desired temperature.

  In the present invention, the metal oxide film forming liquid may be brought into contact with the dense fuel electrode layer in an oxidizing gas atmosphere. 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, in this invention, when contacting a metal oxide film forming liquid on a dense fuel electrode layer, you may irradiate a ultraviolet-ray to the location where a dense fuel electrode layer and a metal oxide film forming liquid contact. 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 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, ultraviolet rays may be irradiated to the portion where the dense fuel electrode layer and the metal oxide film forming liquid are in contact with each other in the above-described oxidizing gas atmosphere.

  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 liquid. 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.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate. 1A to 1C 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 is dissolved in a solvent such as water to prepare a metal oxide film forming solution 1. 1A, the dense fuel electrode layer 11 containing nickel oxide is heated to a temperature higher than the metal oxide film formation temperature by, for example, a hot plate (not shown), and the metal oxide is sprayed by the spray device 2. The film forming solution 1 is sprayed onto the dense fuel electrode layer 11. Thereby, as shown in FIG. 1B, a metal oxide film 12 in contact with the dense fuel electrode layer 11 is formed.

  Subsequently, as shown in FIG. 1C, 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. In this embodiment, the metal oxide film forming solution is used, but a metal oxide film forming sol may be used instead of the metal oxide film forming solution.

  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. 1C 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 to sufficiently volatilize ethanol, and then molded by a uniaxial press. And this was sintered at 1400 degreeC for 5 hours, and it cut | disconnected (trimmed) with the ceramic cutter, and produced the dense fuel electrode board | substrate (thickness: 0.5 mm) used as a dense fuel electrode layer.

  Next, zirconium acetylacetonate (manufactured by Kanto Chemical Co., Inc.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) were added in toluene: ethanol = 85: A metal oxide film forming solution was prepared by dissolving in a mixed solvent of 15. Then, the metal oxide film forming solution (100 ml) is sprayed onto the dense fuel electrode substrate heated to 500 ° C. with an airless spray (manufactured by Nordson: nozzle model number 01/12, spray pressure 2 MPa), and An electrolyte layer made of YSZ (thickness on the dense fuel electrode substrate: 200 nm) was formed on the dense fuel electrode substrate. The injection amount at this time was 0.025 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 to sufficiently evaporate ethanol, and then molded by a uniaxial press. And this was sintered at 1400 degreeC for 5 hours, and it cut | disconnected (trimmed) with the ceramic cutter, and produced the porous fuel electrode board | substrate (thickness: 0.5 mm) used as a porous electrode layer.

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. 2, 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 200 ml / min, and air is supplied from the air electrode side at 500 ml / min. The open circuit voltage (OCV) was then measured. As a result, the OCV of the example was stabilized at 857 mV, but the OCV of the comparative example was 320 ± 100 mV, which was not stable. In the comparative example, since the denseness of the electrolyte layer is insufficient, it is considered that the OCV decreased due to gas leak and became unstable. On the other hand, in the examples, a large decrease in OCV was not observed, and the electromotive force was stable.

  Moreover, as shown in the cross-sectional photograph (FIG. 3A) by scanning electron microscope (SEM) observation before evaluation of battery performance and the cross-sectional photograph (FIG. 3B) by SEM observation after evaluation of battery performance, the obtained Example The electrolyte layer was confirmed to be a dense layer before and after evaluation. The thickness of the electrolyte layer was about 0.2 μm.

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 a schematic diagram which shows the evaluation method of battery performance. A and B are cross-sectional SEM photographs of the electrolyte layer formed in the example of the present invention, among which A is a cross-sectional SEM photograph before evaluation of battery performance, and B is a cross-sectional SEM photograph after evaluation of battery performance. is there.

Explanation of symbols

1 Solution for forming metal oxide film 2 Spray device 10 Solid oxide fuel cell (single cell)
11 Dense fuel electrode layer 12 Metal oxide film (electrolyte layer)
13 Air electrode layer 91 Alumina pipe 91a Air supply path 91b Exhaust path 92 Single cell 93 Glass seal

Claims (19)

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,
A method for producing a solid oxide fuel cell, wherein the metal oxide film is formed by bringing a metal oxide film-forming solution containing a metal source into contact with the heated dense fuel electrode layer.   When the metal oxide film forming solution is brought into contact with the dense fuel electrode layer, the metal element constituting the metal source is combined with oxygen to form the metal oxide film on the dense fuel electrode layer. The method for producing a solid oxide fuel cell according to claim 1, wherein the dense fuel electrode layer is heated to a minimum temperature or higher.   The metal oxide film is formed by spraying the metal oxide film forming solution onto the dense fuel electrode layer, thereby bringing the metal oxide film forming solution into contact with the dense fuel electrode layer. A method for producing a solid oxide fuel cell according to claim 1 or 2.   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 one selected from chlorate ions, perchlorate ions, chlorite ions, hypochlorite ions, bromate ions, hypobromate ions, nitrate ions and nitrite ions. The method for producing a solid oxide fuel cell according to any one of claims 1 to 4, further comprising one ionic species. 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,
A method for producing a solid oxide fuel cell, wherein the metal oxide film is formed by contacting a sol for forming a metal oxide film containing a metal source on the heated dense fuel electrode layer.   When the metal oxide film forming sol is brought into contact with the dense fuel electrode layer, the metal element constituting the metal source combines with oxygen to form the metal oxide film on the dense fuel electrode layer. The method for producing a solid oxide fuel cell according to claim 6, wherein the dense fuel electrode layer is heated to a minimum temperature or higher.   The metal oxide film is formed by spraying the metal oxide film forming sol onto the dense fuel electrode layer to bring the metal oxide film forming sol into contact with the dense fuel electrode layer. A method for producing a solid oxide fuel cell according to claim 6 or 7.   9. The method for producing a solid oxide fuel cell according to claim 6, wherein the sol for forming a metal oxide film further contains at least one selected from an oxidizing agent and a reducing agent.   The sol for forming a metal oxide film is at least one selected from chlorate ion, perchlorate ion, chlorite ion, hypochlorite ion, bromate ion, hypobromate ion, nitrate ion and nitrite ion. The method for producing a solid oxide fuel cell according to any one of claims 6 to 9, further comprising one ionic species.   8. The method for producing a solid oxide fuel cell according to claim 1, wherein the metal source is at least one selected from a metal salt, a metal complex, and an organometallic compound.   The metal sources are Ca, Cr, Sr, Nb, Mo, Sb, Te, Ba, W, Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ag 12. The structure according to claim 1, comprising at least one metal element selected from In, Sn, Ce, Sm, Pb, La, Hf, Sc, Gd, Ga, and Ta. Of manufacturing a solid oxide fuel cell.   9. The solid according to claim 1, 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. Manufacturing method of oxide fuel cell.   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.   9. The solid oxide fuel cell according to claim 1, wherein the dense fuel electrode layer further includes an oxide ion conductor having a fluorite-type or perovskite-type crystal structure. Production method.   9. The solid oxide form according to claim 1, wherein the metal oxide film includes an aggregate of crystals having a columnar structure in which crystals grow in the stacking direction of the metal oxide film. Manufacturing method of fuel cell.   The value obtained by dividing the crystal length in the stacking direction of the metal oxide film in the crystal by the crystal diameter in a direction orthogonal to the stacking direction of the metal oxide film in the crystal is 2 or more. Of manufacturing a solid oxide fuel cell.   9. 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 producing a solid oxide fuel cell according to any one of claims 1 to 3, 6 to 8, and 15, wherein the dense fuel electrode layer has a relative density of 90% or more.

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