JP2006286607A - Solid oxide type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide type fuel cell capable of reducing grain boundaries disturbing movement of oxide ion in an electrolyte layer. <P>SOLUTION: The solid oxide type fuel cell (10) has an electrolyte layer (11) and a pair of porous electrode layers (12, 13), interposing at least one part of the electrolyte layer (11). The region of the electrolyte layer (11) interposed between the pair of porous electrode layers (12, 13) contains an aggregate of crystals (11a) of metal oxide, and the crystal (11a) has a columnar structure elongated, in a direction substantially normal to the surface (12a) of the porous electrode layer (12) on one side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell having an electrolyte layer and a pair of porous electrode layers that sandwich at least a part of the electrolyte layer.

  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. The air electrode layer and the fuel electrode layer are both porous layers so that the gas can reach the interface with the electrolyte layer. 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 electronic 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.

FIG. 7 is a schematic cross-sectional view of a conventional solid oxide fuel cell in which an electrolyte layer is formed using a screen printing method. As shown in FIG. 7, the solid oxide fuel cell 100 includes an electrolyte layer 101, and a fuel electrode layer 102 and an air electrode layer 103 that sandwich the electrolyte layer 101. Since the electrolyte layer 101 is formed by a screen printing method, it has a structure in which several crystals 101a are stacked in the thickness direction of the electrolyte layer 101.
JP 2004-79332 A JP 2002-323362 A JP 2001-23653 A JP 2002-15757 A

  Usually, a part of the metal component constituting the electrolyte layer 101 shown in FIG. 7 is dissolved as a metal ion in the crystal grain boundary 101b in the electrolyte layer 101. The metal ions dissolved in the crystal grain boundaries 101b hinder the movement (diffusion) of the oxide ions. Therefore, as in the electrolyte layer 101 shown in FIG. 7, when the crystal grain boundary 101b exists in a direction substantially perpendicular to the moving direction of the oxide ions (the thickness direction of the electrolyte layer 101), the movement of the oxide ions is prevented. Interfering grain boundaries increase and oxide ion conductivity decreases. As a result, the electrical resistance (internal resistance) in the solid oxide fuel cell 100 may increase.

  The present invention has been made in view of such circumstances, and provides a solid oxide fuel cell capable of reducing grain boundaries that hinder the movement of oxide ions in an electrolyte layer.

The solid oxide fuel cell of the present invention is a solid oxide fuel cell having an electrolyte layer and a pair of porous electrode layers sandwiching at least a part of the electrolyte layer,
The region sandwiched between the pair of porous electrode layers in the electrolyte layer includes an aggregate of crystals made of a metal oxide,
The crystal has a columnar structure extending along a substantially normal direction of the surface of one of the porous electrode layers.

  In the solid oxide fuel cell of the present invention, the region sandwiched between the pair of porous electrode layers in the electrolyte layer includes an aggregate of crystals, and the crystal is in a substantially normal direction of the surface of one of the porous electrode layers. Therefore, grain boundaries that hinder the movement of oxide ions in the electrolyte layer can be reduced. Thereby, since the oxide ion conductivity of the electrolyte layer can be improved, for example, a solid oxide fuel cell capable of reducing the internal resistance can be provided.

  The solid oxide fuel cell of the present invention has an electrolyte layer and a pair of porous electrode layers that sandwich at least a part of the electrolyte layer, and is sandwiched by the pair of porous electrode layers among the electrolyte layers. The formed region includes an aggregate of crystals made of a metal oxide, and the crystal has a columnar structure extending along a substantially normal direction of the surface of one of the porous electrode layers. Therefore, it is possible to reduce grain boundaries that hinder the movement of oxide ions in the electrolyte layer (for example, grain boundaries in a direction orthogonal to the moving direction of oxide ions). Thereby, since the oxide ion conductivity of the electrolyte layer can be improved, for example, a solid oxide fuel cell capable of reducing the internal resistance can be provided. Further, since the grain boundary in the electrolyte layer can be reduced as compared with the conventional case, gas leak in the electrolyte layer can be prevented.

  As the pair of porous electrode layers, a fuel electrode layer and an air electrode layer can be used. In this case, the crystal has a columnar structure extending along the substantially normal direction of the surface of one of the fuel electrode layer and the air electrode layer. The pair of porous electrode layers only need to sandwich at least part of the electrolyte layer. Therefore, as described later, for example, a part of the electrolyte layer may be formed inside one of the pair of porous electrode layers.

  As the metal oxide constituting the crystal, 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, is used. Can be used. Specific examples of such metal oxides include YSZ, scandia-stabilized zirconia (hereinafter abbreviated as “ScSZ”), Samaria doped ceria (hereinafter abbreviated as “SDC”), gadolinium doped ceria (hereinafter abbreviated as “ScSZ”). , Abbreviated as “GDC”), lanthanum garade and the like. The composite metal oxide preferably has a fluorite-type or perovskite-type crystal structure from the viewpoint of oxide ion conductivity.

  As the material for the fuel electrode layer, for example, a mixture of an oxide ion conductor such as a ceramic powder material and a metal catalyst can be used. 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. Further, examples of those having a perovskite crystal structure include lanthanum galide oxides doped with strontium and magnesium. As a metal constituting the metal catalyst, a material that is stable in a reducing atmosphere and has a hydrogen oxidation activity can be used. For example, nickel, iron, cobalt, or the like, or a noble metal (platinum, ruthenium, palladium, or the like) ) Etc. can be used. Among the above materials, nickel having high hydrogen oxidation activity is preferable. Therefore, it is preferable to form the fuel electrode layer with a mixture of the oxide ion conductor and nickel. Note that the mixture of the ceramic powder material made of an oxide ion conductor and nickel may be a mixture of both, or a modification of the ceramic powder to nickel. Moreover, the ceramic powder material mentioned above may be used individually by 1 type, and may mix and use 2 or more types. Further, the fuel electrode layer can be composed of only a metal catalyst. The porosity of the fuel electrode layer is usually 20 to 50% by volume, and preferably 30 to 40% by volume. The thickness of the fuel electrode layer is usually 5 to 50 μm. Moreover, the average diameter of the pores in the fuel electrode layer is preferably 1 μm or more and 100 μm or less, and more preferably 1 μm or more and 10 μm or less. When the average diameter of the pores is less than 1 μm, the gas permeability of the fuel electrode layer may be lowered. On the other hand, when the average diameter of the pores exceeds 100 μm, the strength of the fuel electrode layer may decrease.

As the material of 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. In addition, the porosity of an air electrode layer is 20-50 volume% normally, Preferably it is 30-40 volume%. The thickness of the air electrode layer is usually 5 to 50 μm. Moreover, the average diameter of the pores in the air electrode layer is preferably 1 μm or more and 100 μm or less, and more preferably 1 μm or more and 10 μm or less. When the average diameter of the pores is less than 1 μm, the gas permeability of the air electrode layer may be lowered. On the other hand, when the average diameter of the pores exceeds 100 μm, the strength of the air electrode layer may decrease.

  In the present invention, the aspect ratio of the crystal is preferably 2 or more in order to further improve the oxide ion conductivity of the electrolyte layer. Here, the “aspect ratio” is obtained by dividing the crystal length in the substantially normal direction of the surface of the one porous electrode layer in the crystal by the crystal diameter in the direction orthogonal to the approximately normal direction in the crystal. Value. The crystal length in the substantially normal direction of the crystal is, for example, about 10 nm to 50 μm, and the crystal diameter of the crystal in the direction orthogonal to the substantially normal direction is, for example, about 5 nm to 25 nm.

  In the present invention, in order to further improve the oxide ion conductivity of the electrolyte layer, the crystal is preferably a single crystal. In particular, it is preferable that both ends of the single crystal are in contact with the respective surfaces of the pair of porous electrode layers because the oxide ion conductivity can be further improved.

  The aggregate may be an aggregate in which the crystals are arranged along the surface of the one porous electrode layer. According to this configuration, since the crystals are in close contact with each other, the denseness of the electrolyte layer is improved. Thereby, the gas impermeability of the electrolyte layer can be improved.

  In the present invention, the electrolyte layer further includes a first film made of the metal oxide formed along the surface of the one porous electrode layer, and the assembly includes the first film. It may be an aggregate of the crystals arranged along the surface. According to this configuration, since the crystal contained in the first film is a crystal nucleus and an aggregate of the crystal grown from the crystal nucleus into a columnar structure can be obtained, the aggregate in which the crystals are closer to each other can be obtained. It can be a body. Thereby, the gas impermeability of the electrolyte layer can be further improved. In addition, in order to exhibit the said effect reliably, it is preferable that the thickness of the said 1st coating film is 10 nm or more and 50 micrometers or less, and it is more preferable that they are 10 nm or more and 1 micrometer or less.

  The electrolyte layer may further include a second coating that covers at least a part of a wall surface that forms pores in the one porous electrode layer. For example, when the second coating is present on the surface layer of the porous electrode layer located near the interface between the porous electrode layer and the electrolyte layer, the adhesion between the porous electrode layer and the electrolyte layer is improved. Therefore, it is preferable. In addition, when the second coating is present, the above-described three-phase interface increases, so that the electrode reaction can be facilitated. In order to exhibit the effect more reliably, at least 10 nm (more preferably at least 100 nm, particularly preferably at least 1 μm) in the depth direction of the porous electrode layer from the interface between the porous electrode layer and the electrolyte layer. It is preferable that the second coating is present in the pores existing in the range up to. The thickness of the second coating is preferably 10 nm or more and 50 μm or less, and more preferably 10 nm or more and 1 μm or less. Within this range, the above-described three-phase interface can be increased while maintaining good gas permeability of the porous electrode layer. In addition, the material of the said 2nd film should just be the same as that of the said 1st film, for example.

  The thickness of the region sandwiched between the pair of porous electrode layers in the electrolyte layer is usually 10 nm to 50 μm, preferably 10 nm to 10 μm, more preferably 100 nm to 5 μm, and most preferably. Is 100 nm or more and 1 μm or less. When the thickness is less than 10 nm, the pair of porous electrode layers may come into contact with each other. On the other hand, if the thickness exceeds 50 μm, the oxide ion conductivity of the electrolyte layer may be reduced. The ratio of the aggregate of crystals having the columnar structure in the region of the electrolyte layer is, for example, 95% by volume or more, and 98% by volume or more in order to further improve the oxide ion conductivity. Preferably, it is 100% by volume.

  Next, an example of a preferred method for producing the above-described solid oxide fuel cell of the present invention (hereinafter also referred to as “first production method”) will be described.

  First, a method for forming an electrolyte layer in contact with the porous electrode layer will be described. In the first production method, the porous electrode layer (fuel electrode layer or air electrode layer) is heated to a temperature higher than or equal to the metal oxide film formation temperature, and is used for forming a metal oxide film containing a metal source on the porous electrode layer. An electrolyte layer made of a metal oxide film is formed by spraying the solution. The electrolyte layer obtained by this method includes an aggregate of crystals having a columnar structure extending along a substantially normal direction of the surface of the porous electrode layer. In addition, according to this method, for example, a heat treatment step at a high temperature of 1000 ° C. or higher is not required, and the electrolyte layer can be easily densified, so that the manufacturing process can be further simplified. The “metal oxide film formation temperature” is the lowest temperature at which a metal element constituting the metal source is combined with oxygen to form a metal oxide film on the porous electrode layer. The metal oxide film formation temperature varies greatly depending on the composition of the metal oxide film formation solution such as the type of metal source and 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 solution contains an oxidizing agent or a reducing agent, which will be described later, 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 that the temperature is in the range of 300 to 500 ° C.

  The metal oxide film formation temperature can be measured by the following method. First, a metal oxide film forming solution containing a desired metal source is prepared. Next, by changing the heating temperature of the porous electrode layer and bringing the metal oxide film forming solution into contact with the porous electrode layer, a porous electrode layer capable of forming a metal oxide film Of these heating temperatures, 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 metal oxide film is formed can be determined from a result obtained by, for example, an X-ray diffractometer (RINT-1500, manufactured by Rigaku).

  The heating method for the porous 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 porous electrode layer can be reliably maintained at a desired temperature.

  As the porous electrode layer used as a support substrate when forming the electrolyte layer, the above-described fuel electrode layer or air electrode layer can be used. The constituent materials and the like are the same as described above, and will be omitted. The porous electrode layer itself may be used as a support substrate for forming the electrolyte layer, or a porous support layer coated with a material for the electrode layer is used as the porous electrode layer. This may be used as a support substrate for forming the electrolyte layer. As a material for the porous support substrate, heat-resistant ceramics, heat-resistant metals, or the like can be used.

  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.

  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, 2-propanol, 1-propanol, butanol, water, toluene, a mixed solvent thereof or the like may be used. In the case where 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.

  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.

  The metal oxide film forming solution may contain additives such as an auxiliary ion source and a surfactant.

  The auxiliary ion source generates hydroxide ions by reacting with electrons, and can increase 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 porous 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.

  Examples of the method of spraying the metal oxide film forming solution onto the porous 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, and 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, a decrease in the temperature of the porous electrode layer due to spraying 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 solution for forming a metal oxide film is usually 0.001 to 1 liter / min. In order to further improve the denseness of the resulting metal oxide film, 0.001 to 0.001. It is preferably 05 liter / min. At this time, the thickness of the formed metal oxide film can be arbitrarily adjusted by spraying repeatedly. 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.

  Further, after forming a metal oxide film, that is, an electrolyte layer by the above method, the electrolyte layer may be washed and dried. The washing of the electrolyte layer is performed to remove impurities present on the surface of the electrolyte layer. Examples of the cleaning method include a method of cleaning using a solvent used in the metal oxide film forming solution. When the electrolyte layer is dried, the electrolyte layer may be left at room temperature to dry, or may be dried in a heating apparatus such as an oven.

  Next, on the electrolyte layer obtained by the above method, a porous electrode layer (fuel electrode layer or air electrode layer) paired with the porous electrode layer used as a support substrate when forming the electrolyte layer is formed. A method of forming will be described. First, a paste is prepared by adding the electrode layer material and a binder to a solvent, and this paste is applied onto the electrolyte layer by an application method such as a screen printing method or a doctor blade method. And these are sintered for several hours, for example at the temperature of 1000 degreeC or more, and a fuel electrode layer or an air electrode layer is formed on the said electrolyte layer. With the above method, the solid oxide fuel cell of the present invention is obtained.

  Next, a preferred production method of the solid oxide fuel cell of the present invention, which is a production method different from the first production method (hereinafter also referred to as “second production method”) will be described. This second manufacturing method differs from the first manufacturing method only in the method for forming the electrolyte layer. The electrolyte layer forming method in the second production method is as follows. First, (1) a porous electrode layer (fuel electrode layer or air) is added to a first metal oxide film forming solution containing a metal source and an oxidizing agent or a reducing agent. A first metal oxide film in contact with the porous electrode layer is formed by immersing the electrode layer). Next, (2) in a state where the first metal oxide film is heated to the metal oxide film formation temperature or higher, a second metal oxide film forming solution containing a metal source is sprayed on the first metal oxide film. By doing so, a second metal oxide film is formed, and an electrolyte layer composed of the first metal oxide film and the second metal oxide film is obtained. As a result, the same effects as those of the first manufacturing method described above can be exhibited, and when the second metal oxide film is formed, a columnar structure with crystals contained in the first metal oxide film as crystal nuclei. Therefore, a second metal oxide film including an aggregate in which the crystals having the columnar structure are in close contact with each other can be obtained. Therefore, the gas impermeability of the obtained electrolyte layer can be further improved. Note that a region of the first metal oxide film formed on the porous electrode layer corresponds to the “first coating”.

  Further, according to the above-described method, the first metal oxide film can be formed not only on the surface of the porous electrode layer but also on the wall surface forming the pores in the porous electrode layer. Usually, a part of the first metal oxide film obtained by the above-described method is formed along at least a part of the wall surface of the porous electrode layer. A part of the first metal oxide film formed along the wall surface forming pores in the porous electrode layer corresponds to the “second coating”.

  Hereinafter, although the detail of a 2nd manufacturing method is demonstrated, since it is the same as that of the 1st manufacturing method mentioned above except the said (1) process, hereafter, only the said (1) process is demonstrated and the overlapping description is abbreviate | omitted. .

  The first metal oxide film forming solution used in the step (1) includes a metal source and an oxidizing agent or a reducing agent. Specific examples of the metal source, the oxidizing agent, and the reducing agent are the same as in the case of the first manufacturing method described above, and thus the description thereof is omitted. Further, the other components (solvent, additive, etc.) of the first metal oxide film forming solution are the same as in the case of the first manufacturing method described above, and thus the description thereof is omitted. The first metal oxide film forming solution and the second metal oxide film forming solution may be the same or different from each other. When the first metal oxide film forming solution is different from the second metal oxide film forming solution, the crystal of the first metal oxide film obtained by the first metal oxide film forming solution It is preferable to select each solution composition so that the system and the crystal system of the second metal oxide film obtained by the second metal oxide film forming solution are approximated (or matched).

  When immersing the porous electrode layer in the first metal oxide film forming solution, at least one (preferably both) of the first metal oxide film forming solution and the porous electrode layer is 10 ° C. You may hold | maintain at the above temperature. This is because the film formation reaction of the first metal oxide film can be promoted. In order to further promote the film formation reaction of the first 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 first metal oxide film forming solution from the viewpoint of workability. For example, at least one (preferably both) of the first metal oxide film forming solution and the porous electrode layer may be normally maintained in the range of 10 to 100 ° C., and 50 to 90 ° C. from the viewpoint of productivity. It is preferable to heat to this range.

  When the porous electrode layer is immersed in the first metal oxide film forming solution, a bubble-like oxidation is formed in a portion where the porous electrode layer and the first metal oxide film forming solution are in contact with each other. A sex gas may be contacted. This is because the metal ions and the like formed by dissolving the metal source are rapidly oxidized, so that the film formation reaction of the first 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 porous electrode layer and the first metal oxide film forming solution are in contact with the oxidizing gas can be increased. This is because the deposition rate of the physical film can be improved efficiently. As such a bubbler, a general bubbler can be used, and examples thereof include a Naflon bubbler (manufactured by ASONE). Further, the oxidizing gas can be normally supplied from the gas cylinder to the first metal oxide film forming solution, and ozone can be supplied from the ozone generator to the first metal oxide film forming solution. .

  In addition, when the porous electrode layer is immersed in the first metal oxide film forming solution, ultraviolet light is applied to a portion where the porous electrode layer and the first metal oxide film forming solution are in contact with each other. It may be irradiated. 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. As described above, the first metal is generated by the generated hydroxide ions. This is because the film formation reaction of the oxide 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 first 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.

  The manufacturing method of the solid oxide fuel cell of the present invention has been described above. However, the first and second manufacturing methods are examples of the preferable manufacturing method of the solid oxide fuel cell of the present invention. The solid oxide fuel cell may be manufactured by a method other than the first and second manufacturing methods.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings as appropriate.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 to be referred to is a schematic cross-sectional view showing a solid oxide fuel cell according to a first embodiment of the present invention.

  As shown in FIG. 1, the solid oxide fuel cell 10 according to the first embodiment includes an electrolyte layer 11, a fuel electrode layer 12 and an air electrode layer 13 that sandwich a part of the electrolyte layer 11. And the area | region pinched | interposed by the fuel electrode layer 12 and the air electrode layer 13 among the electrolyte layers 11 contains the aggregate | assembly of the crystal | crystallization 11a which consists of metal oxides.

  The crystal 11 a has a columnar structure extending along the direction of the normal line of the surface 12 a of the fuel electrode layer 12, and these crystals 11 a are aggregates arranged along the surface 12 a of the fuel electrode layer 12. Is forming. Thereby, since the grain boundary (for example, the grain boundary of the direction orthogonal to the moving direction of an oxide ion) which prevents the movement of the oxide ion in the electrolyte layer 11 can be reduced, the oxide ion of the electrolyte layer 11 is reduced. Conductivity can be improved. Furthermore, since the crystals 11a are in close contact with each other, the denseness of the electrolyte layer 11 is improved. Thereby, the gas impermeability of the electrolyte layer 11 can be improved.

  Further, a part 11 b of the electrolyte layer 11 covers a part of the wall surface 12 b that forms pores in the fuel electrode layer 12. As a result, the above-described three-phase interface increases, and the electrode reaction in the fuel electrode layer 12 can be facilitated. The part 11b of the electrolyte layer 11 corresponds to the “second coating” described above.

  Next, an example of a method for manufacturing the solid oxide fuel cell 10 according to the first embodiment will be described with reference to the drawings. 2A to 2C to be referred to are schematic process diagrams showing an example of a method for manufacturing the solid oxide fuel cell 10 according to the first embodiment of the present invention. 2A to 2C, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  First, a metal source is dissolved in a solvent such as water to prepare a metal oxide film forming solution 1 (see FIG. 2A). Next, as shown in FIG. 2A, the fuel electrode layer 12 is heated to a metal oxide film formation temperature or higher by, for example, a hot plate (not shown) or the like, and the metal oxide film forming solution is sprayed by the spray device 2. 1 is sprayed on the fuel electrode layer 12. As a result, as shown in FIG. 2B, the electrolyte layer 11 including the aggregate of the crystals 11 a is formed on the fuel electrode layer 12. At this time, the part 11 b of the electrolyte layer 11 covers a part of the wall surface 12 b that forms pores in the fuel electrode layer 12.

  Subsequently, as shown in FIG. 2C, the air electrode layer 13 is formed on the electrolyte layer 11 by means of a screen printing method or the like, and the solid oxide fuel cell 10 according to the first embodiment is obtained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 to be referred to is a schematic cross-sectional view showing a solid oxide fuel cell according to a second embodiment of the present invention. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 3, the solid oxide fuel cell 20 according to the second embodiment includes an electrolyte layer 21, and a fuel electrode layer 12 and an air electrode layer 13 that sandwich a part of the electrolyte layer 21. And the area | region pinched | interposed by the fuel electrode layer 12 and the air electrode layer 13 among the electrolyte layers 21 contains the aggregate | assembly of the crystal | crystallization 21a which consists of metal oxides. The electrolyte layer 21 further includes a coating 21b made of the metal oxide. The coating 21 b includes a region 211 b formed along the surface 12 a of the fuel electrode layer 12 and a region 212 b formed along a part of the wall surface 12 b that forms pores in the fuel electrode layer 12. The region 211b corresponds to the “first coating”, and the region 212b corresponds to the “second coating”.

  The crystals 21a have a columnar structure extending along a substantially normal direction of the surface 12a of the fuel electrode layer 12, and these crystals 21a form an aggregate arranged along the region 211b of the coating 21b. is doing. As a result, the solid oxide fuel cell 20 according to the second embodiment has the same effect as the solid oxide fuel cell 10 according to the first embodiment described above, and crystals contained in the region 211b of the coating 21b. As a crystal nucleus, an aggregate of the crystals 21a grown from the crystal nucleus into a columnar structure can be obtained, so that the crystals 21a can be aggregated closer to each other. Thereby, the gas impermeability of the electrolyte layer 21 can be further improved.

  Next, an example of a method for manufacturing the solid oxide fuel cell 20 according to the second embodiment will be described with reference to the drawings. 4A and 4B and FIGS. 5A to 5C to be referred to are schematic process diagrams showing an example of a method for manufacturing the solid oxide fuel cell 20 according to the second embodiment of the present invention. 4A and 4B and FIGS. 5A to 5C, the same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted.

  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. 4A). Then, as shown in FIG. 4A, the fuel electrode layer 12 is immersed in the first metal oxide film forming solution 1a. As a result, as shown in FIG. 4B, a coating 21b in contact with the fuel electrode layer 12 is formed. Thereafter, the fuel electrode layer 12 covered with the coating 21b is taken out from the first metal oxide film forming solution 1a.

  Next, as shown in FIG. 5A, the coating 21b and the fuel electrode layer 12 are heated to a temperature higher than the metal oxide film formation temperature by, for example, a hot plate (not shown) or the like, and then the second metal oxidation is performed by the spray device 2. The material film forming solution 1b (for example, the same composition as the first metal oxide film forming solution 1a) is sprayed onto the region 211b of the coating 21b. Thereby, as shown in FIG. 5B, an aggregate of the crystals 21a is formed on the region 211b of the film 21b, and the electrolyte layer 21 including the film 21b and the aggregate of the crystals 21a is obtained.

  Subsequently, as shown in FIG. 5C, the air electrode layer 13 is formed on the electrolyte layer 21 using means such as a screen printing method, and the solid oxide fuel cell 20 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, in the above embodiment, the case where the crystals constituting the assembly have a columnar structure extending along the substantially normal direction of the surface of the fuel electrode layer is exemplified, but the crystals constituting the assembly are the air electrode layer. It may be a crystal having a columnar structure extending along a substantially normal direction of the surface.

  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 1
In this example, a single cell having the structure shown in FIG. 1 was manufactured. 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 size: 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, zirconium tetraacetylacetonate (manufactured by Kanto Chemical Co., Inc.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) were added to toluene: ethanol so that the respective concentrations would be 0.1 mol / liter and 0.008 mol / liter. A solution for forming a metal oxide film was prepared by dissolving in a mixed solvent of = 85: 15. Then, the metal oxide film forming solution (100 ml) is sprayed onto the porous fuel electrode substrate heated to 450 ° C. with an ultrasonic neplyzer (manufactured by OMRON), and YSZ is applied onto the porous fuel electrode substrate. An electrolyte layer (thickness on the porous fuel electrode substrate: 10 μm) was formed. The injection amount at this time was 0.001 liter / min. 6, which is a cross-sectional SEM photograph of the obtained electrolyte layer, the electrolyte layer 30 includes an aggregate of crystals 30 a, and this crystal 30 a extends along a substantially normal direction of the surface of the porous fuel electrode substrate 31. It was found to have a columnar structure.

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 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 by screen printing on the above 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.

(Example 2)
Since Example 2 differs from Example 1 described above only in the formation method of the electrolyte layer, only the formation method of the electrolyte layer will be described.

  Zirconium tetraacetylacetonate and scandium acetate (manufactured by Kanto Chemical Co., Inc.) were dissolved in a mixed solvent consisting of toluene and ethanol so that the respective concentrations would be 0.1 mol / liter and 0.01 mol / liter. An oxide film forming solution was prepared. The mixed solvent used had a volume ratio (toluene: ethanol) of 70:30. Then, the metal oxide film forming solution (80 ml) is sprayed onto the porous fuel electrode substrate heated to 400 ° C. with an ultrasonic nebulizer (manufactured by OMRON Corporation), and ScSZ is applied onto the porous fuel electrode substrate. An electrolyte layer (thickness on the porous fuel electrode substrate: 1 μm) was formed. The injection amount at this time was 0.005 liter / min.

(Example 3)
Since Example 3 differs from Example 1 described above only in the formation method of the electrolyte layer, only the formation method of the electrolyte layer will be described.

  Zirconium normal propylate (manufactured by Kanto Chemical Co., Inc.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) were added in toluene: ethanol = 85: 15 so that the respective concentrations would be 0.1 mol / liter and 0.008 mol / liter. A sol for forming a metal oxide film was prepared by dissolving in a mixed solvent. Then, the metal oxide film-forming sol (100 milliliters) is sprayed onto the porous fuel electrode substrate heated to 450 ° C. by hand spray (manufactured by ASONE), and the YSZ is applied onto the porous fuel electrode substrate. An electrolyte layer (thickness on the porous fuel electrode substrate: 10 μm) was formed. The injection amount at this time was 0.001 liter / min.

Example 4
Since Example 4 differs from Example 1 described above only in the formation method of the electrolyte layer, only the formation method of the electrolyte layer will be described.

  Zirconium normal butyrate (manufactured by Kanto Chemical Co., Inc.) and yttrium nitrate (manufactured by Kanto Chemical Co., Ltd.) were added in toluene: ethanol = 85: 15 so that the respective concentrations would be 0.1 mol / liter and 0.008 mol / liter. A sol for forming a metal oxide film was prepared by dissolving in a mixed solvent. Then, the metal oxide film-forming sol (100 ml) is sprayed onto the porous fuel electrode substrate heated to 450 ° C. with an ultrasonic nebulizer (manufactured by OMRON), and YSZ is applied onto the porous fuel electrode substrate. An electrolyte layer (thickness on the porous fuel electrode substrate: 10 μm) was formed. The injection amount at this time was 0.001 liter / min.

(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. 8, 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. The results are shown in Table 1.

  As shown in Table 1, in the comparative example, it was confirmed that the open circuit voltage was lowered due to the gas leak. On the other hand, for Examples 1 to 4, no significant decrease in open circuit voltage was observed. From this result, in Examples 1-4, since the grain boundary in an electrolyte layer can be reduced compared with a comparative example, it turns out that the gas leak in an electrolyte layer can be prevented.

1 is a schematic cross-sectional view showing a solid oxide fuel cell according to a first embodiment of the present invention. A to C are schematic process diagrams illustrating an example of a method for manufacturing a solid oxide fuel cell according to the first embodiment of the present invention. It is a schematic cross section which shows the solid oxide fuel cell which concerns on 2nd Embodiment of this invention. A and B are schematic process diagrams showing an example of a method for producing a solid oxide fuel cell according to a second embodiment of the present invention. A to C are schematic process diagrams illustrating an example of a method for producing a solid oxide fuel cell according to a second embodiment of the present invention. It is a cross-sectional SEM photograph of the electrolyte layer formed in Example 1 of this invention. It is a schematic cross section showing a conventional solid oxide fuel cell. It is a schematic diagram which shows the evaluation method of battery performance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 Solid oxide fuel cell 11, 21, 30 Electrolyte layer 11a, 21a, 30a Crystal 12 Fuel electrode layer 12a Surface 12b Wall surface 13 Air electrode layer 21b Coating 31 Porous fuel electrode substrate (fuel electrode layer)
91 Alumina pipe 91a Air supply path 91b Exhaust path 92 Single cell 93 Glass seal

Claims (15)

A solid oxide fuel cell having an electrolyte layer and a pair of porous electrode layers sandwiching at least a part of the electrolyte layer,
The region sandwiched between the pair of porous electrode layers in the electrolyte layer includes an aggregate of crystals made of a metal oxide,
The solid oxide fuel cell, wherein the crystal has a columnar structure extending along a substantially normal direction of a surface of one of the porous electrode layers.   2. The solid oxide fuel according to claim 1, wherein a value obtained by dividing a crystal length of the crystal in the substantially normal direction by a crystal diameter of the crystal in a direction orthogonal to the substantially normal direction is 2 or more. battery.   The solid oxide fuel cell according to claim 1, wherein the crystal is a single crystal. The crystal is a single crystal,
2. The solid oxide fuel cell according to claim 1, wherein both ends of the single crystal are in contact with respective surfaces of the pair of porous electrode layers.   2. The solid oxide fuel cell according to claim 1, wherein the aggregate is an aggregate in which the crystals are arranged along a surface of the one porous electrode layer. The electrolyte layer further includes a first film made of the metal oxide formed along the surface of the one porous electrode layer,
2. The solid oxide fuel cell according to claim 1, wherein the aggregate is an aggregate in which the crystals are arranged along the surface of the first coating.   The solid oxide fuel cell according to claim 6, wherein the first coating has a thickness of 10 nm to 50 μm.   7. The solid oxide fuel cell according to claim 1, wherein the electrolyte layer further includes a second coating film covering at least a part of a wall surface forming pores in the one porous electrode layer.   The solid oxide fuel cell according to claim 8, wherein the second coating has a thickness of 10 nm or more and 1 μm or less.   The solid oxide fuel cell according to claim 1, wherein the metal oxide is a composite metal oxide containing at least one selected from zirconium oxide, cerium oxide, and lanthanum oxide.   The solid oxide fuel cell according to claim 10, wherein the composite metal oxide has a fluorite-type or perovskite-type crystal structure. The pair of porous electrode layers are a fuel electrode layer and an air electrode layer,
5. The solid oxide fuel cell according to claim 1, wherein the fuel electrode layer includes an oxide ion conductor having a fluorite-type or perovskite-type crystal structure and a metal catalyst. The pair of porous electrode layers are a fuel electrode layer and an air electrode layer,
13. The solid oxide fuel cell according to claim 1, wherein the air electrode layer includes at least one selected from a metal oxide having a perovskite crystal structure and a noble metal.   2. The solid oxide fuel cell according to claim 1, wherein a region of the electrolyte layer sandwiched between the pair of porous electrode layers has a thickness of 10 nm to 10 μm.   The solid oxide fuel cell according to claim 14, wherein a region of the electrolyte layer sandwiched between the pair of porous electrode layers has a thickness of 100 nm to 1 μm.

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