JP2017147053A - Air electrode for solid oxide fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an air electrode which enables the formation of a solid oxide fuel battery superior in power generation performance; and a solid oxide fuel battery single cell having the air electrode.SOLUTION: An air electrode for a solid oxide fuel battery, of which the specific surface area is 0.1 or more and less than 1.0 m/g, comprises a perovskite composite oxide including at least one of La and Sr at an A site, and expressed by the general formula, ABO3, and has a thickness of 5-50 μm. A single cell for a solid oxide fuel battery comprises at least a fuel electrode layer, a solid electrolyte layer, and an air electrode for a solid oxide fuel battery which are laminated in this order. The single cell for a solid oxide fuel battery further comprises a reaction-preventing layer between the layers including the solid electrolyte layer and the air electrode.SELECTED DRAWING: None

Description

  The present invention relates to an air electrode that can constitute a solid oxide fuel cell excellent in power generation performance, and a solid oxide fuel cell single cell having the air electrode.

  Fuel cells are attracting attention as a clean energy source. Improvements and practical application studies are being rapidly promoted mainly for household power generation, commercial power generation, and automobile power generation. Among such fuel cells, a solid oxide fuel cell is expected as a power source for home use and business use because of its high power generation efficiency and excellent long-term stability.

In the air electrode of a solid oxide fuel cell, oxide ions (O ²⁻ ) are generated from oxygen molecules (O ₂ ) and electrons (e ⁻ ), and these oxide ions pass through the solid electrolyte layer to form the fuel electrode. It reacts with fuels such as hydrogen (H ₂ ), carbon monoxide (CO), methane (CH ₄ ), etc. to generate electrons in addition to water (H ₂ O) and carbon dioxide (CO ₂ ). Therefore, in the air electrode, it is important to devise so that the reaction between oxygen molecules contained in an oxygen-containing gas such as air and electrons proceeds smoothly.

  From this point of view, Patent Document 1 discloses an oxide ion conductive material in order to increase a three-phase interface of a solid electrolyte that carries oxide ions, an electrode that carries electrons, and a gas phase that supplies oxygen molecules or fuel. There is disclosed a solid oxide fuel cell electrode in which different particles are attached to a porous sintered body having a three-dimensional network structure composed of the above.

In addition, Patent Document 2 discloses that the specific surface area of the particles is 1.5 to 9.0 m ² / g and the air electrode in order to suppress deterioration of power generation performance due to the growth of particles constituting the air electrode layer. An invention in which the pore diameter of the layer is 30 to 100 nm is disclosed.

Japanese Patent Application Laid-Open No. 2000-200614 JP 2010-108876 A

  As described above, in order to sufficiently promote the electrode reaction, a technique for increasing the three-phase interface between the solid electrolyte, the electrode, and the gas phase has been known. However, the power generation performance of the solid oxide fuel cell may not be sufficiently improved only by increasing the three-phase interface in the electrode.

  Accordingly, an object of the present invention is to provide an air electrode capable of constituting a solid oxide fuel cell excellent in power generation performance, and a solid oxide fuel cell single cell having the air electrode.

  This inventor repeated earnest research in order to solve the said subject. As a result, it is insufficient to focus only on the three-phase interface of the electrode, and in addition, an oxide ion conduction path for delivering oxide ions generated by the electrode reaction at the air electrode to the solid electrolyte layer We also investigated an electron conduction path for delivering the received electrons to the electrode reaction field at the air electrode. As a result, by appropriately defining the specific surface area of the air electrode layer, the oxide ion conduction path and the electron conduction path are sufficient as well as the three-phase interface, and the solid oxide fuel cell with further excellent power generation performance The present invention was completed by finding that a single cell could be obtained.

  Hereinafter, the present invention will be described.

[1] A solid oxide fuel cell air electrode having a specific surface area of 0.1 m ² / g or more and less than 1.0 m ² / g.

[2] The air electrode for a solid oxide fuel cell according to [1], comprising a perovskite complex oxide represented by the general formula ABO ₃ containing at least one of La and Sr at the A site.

  [3] The air electrode for a solid oxide fuel cell according to [1] or [2], wherein the thickness is 5 μm or more and 50 μm or less.

  [4] At least a layer composed of a fuel electrode layer, a solid electrolyte layer, and an air electrode for a solid oxide fuel cell according to any one of the above [1] to [3] is laminated in this order. A single cell for a solid oxide fuel cell.

  [5] The unit cell for a solid oxide fuel cell according to the above [4], further comprising a reaction preventing layer between the solid electrolyte layer and the layer composed of the solid oxide fuel cell air electrode.

  In the air electrode for a solid oxide fuel cell according to the present invention, the electrode reaction proceeds favorably because the oxide ion conduction path and the electron conduction path are probably sufficient together with the three-phase interface. As a result, the solid oxide fuel cell single cell including the air electrode according to the present invention exhibits very excellent power generation performance. Therefore, the present invention is extremely useful industrially as a further enhancement of the performance of the solid oxide fuel cell.

1. Air electrode layer The air electrode for a solid oxide fuel cell according to the present invention has a specific surface area of 0.1 m ² / g or more and less than 1.0 m ² / g. Hereinafter, the solid oxide fuel cell is abbreviated as “SOFC”.

  As a material for the air electrode layer, a general SOFC air electrode layer material can be used without particular limitation. Although it does not specifically limit in detail, For example, a metal, a metal oxide, a metal complex oxide etc. can be used.

Examples of the metal that can be used as the air electrode layer material include metals such as Pt, Au, Ag, Pd, Ir, and Ru, or alloys containing two or more metals. Examples of the metal oxide include oxides such as La, Sr, Ce, Co, Mn, and Fe, for example, La ₂ O ₃ , SrO, Ce ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , and FeO. Etc. Examples of the metal complex oxide include various complex oxides containing at least one of La, Pr, Sm, Sr, Ba, Co, Fe, Mn, and the like. More specifically, examples of the composite oxide include La _1-x Sr _x CoO ₃ composite oxide, La _1-x Sr _x FeO ₃ composite oxide, and La _1-x Sr _x Co _1-y. Fe _y O ₃ -based composite oxide, La _{1 -x} Sr _x MnO ₃ -based composite oxide, Pr _{1 -x} Ba _x CoO ₃ -based composite oxide, Sm _{1 -x} Sr _x CoO ₃ -based composite oxide, and the like be able to. Here, 0 <x <1, 0 <y <1.

Among the examples, the air electrode materials include La _1-x Sr _x CoO ₃ composite oxide, La _1-x Sr _x Co _1-y Fe _y O ₃ composite oxide, and La _1-x Sr _x. It is desirable to use a perovskite complex oxide represented by the general formula ABO ₃ containing at least one of La and Sr at the A site, such as a MnO ₃ complex oxide. Here, “consisting of a perovskite type complex oxide” means that the components of the air electrode material are perovskite type complex oxides, other than inevitable impurities that are not intentionally added.

In addition, ceramics such as zirconia, alumina, magnesia, titania, ceria, aluminum magnesium spinel, aluminum nickel spinel, which are skeletal components of the fuel electrode, may be used alone or in addition to the metal, metal oxide, metal composite oxide, and the like. It is also possible to use a mixture of two or more. These ceramics may be doped with one or more metal oxides from the viewpoints of oxide ion conductivity and electronic conductivity. Such metal oxides include alkaline earth metal oxides such as MgO, CaO, SrO, BaO; Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₆ O ₁₁ , Nd ₂ O _3. Rare earth element oxides such as Sm ₂ O ₃ , Tb ₂ O ₃ , Eu ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ ; Group 4 elements such as TiO ₂ Oxides; Group 5 element oxides such as NbO and Ta ₂ O ₅ ; Group 6 element oxides such as WO ₂ ; Group 10 element oxides such as NiO; Al ₂ O ₃ , B ₂ O ₃ , Ga Group 13 element oxides such as ₂ O ₃ and In ₂ O ₃ ; Group 14 element oxides such as SiO ₂ , GeO ₂ and SnO; Group 15 element oxides such as Bi ₂ O ₃ and Sb ₂ O ₃ And so on. When the above metal oxide is doped into ceramics, the amount of doping may be adjusted as appropriate, and for example, it may be 1 mol% or more and 30 mol% or less.

The air electrode for a solid oxide fuel cell according to the present invention has a specific surface area of 0.1 m ² / g or more and less than 1.0 m ² / g. When the specific surface area is 1.0 m ² / g or more, voids between particles constituting the air electrode are excessively large, and oxide ion conduction paths and electron conduction paths are reduced. As a result, the power generation performance of SOFC is reduced. Can be reduced. On the other hand, if the specific surface area is too small, the voids become too narrow and the oxygen-containing gas does not reach the entire air electrode, and the electrode reaction may not proceed sufficiently. As the specific surface area, preferably at least 0.2 m ² / g, more preferably at least 0.4 m ² / g, particularly preferably not less than 0.5 m ² / g, also is preferably not more than 0.99 m ² / g, 0.9 m ² / g or less is more preferable.

  Although the thickness of an air electrode layer is not specifically limited, For example, it is 5 micrometers or more and 50 micrometers or less. If the thickness of the air electrode layer is less than 5 μm, a sufficient reaction field cannot be secured, and power generation performance may be reduced. On the other hand, if the thickness of the air electrode layer is too thick, the distance that oxide ions are transmitted to the reaction field is particularly long, and the power generation performance may be lowered. Therefore, the thickness is preferably 50 μm or less.

  In a single cell of a solid oxide fuel cell, at least a fuel electrode layer, a solid electrolyte layer, and an air electrode layer are laminated in this order, and an interlayer reaction is prevented between the solid electrolyte layer and the air electrode layer. It may have a reaction preventing layer. Hereinafter, the fuel electrode layer, the solid electrolyte layer, and the reaction preventing layer will be described.

2. Fuel Electrode Layer As a material for the fuel electrode layer, a general SOFC fuel electrode layer material can be used without particular limitation. Specifically, a solid electrolyte material and a conductive component material are used.

  Examples of the solid electrolyte material include zirconia doped with the metal oxides mentioned as those to be doped into the ceramic as the air electrode material. In particular, there can be mentioned ScSZ doped with scandia, ScCeSZ doped with scandia and ceria, YSZ doped with yttria, and YbSZ doped with ytterbium.

  As the conductive component, nickel oxide, cobalt oxide, iron oxide, etc., metal oxides that change into a conductive metal in a reducing atmosphere during SOFC operation; or two or more of these metal oxides, such as nickel ferrite and cobalt ferrite Examples thereof include composite metal oxides contained therein. These may be used alone or in combination of two or more as necessary.

  The thickness of the fuel electrode layer is not particularly limited, but can be, for example, 5 μm or more and 50 μm or less.

  However, the fuel electrode layer may be a fuel electrode support. In this case, the thickness can be 100 μm or more and 1000 μm or less. If the said thickness is 100 micrometers or more, it can be said that a fuel electrode support body has sufficient mechanical strength. On the other hand, if the thickness is 1000 μm or less, it can be said that the fuel gas permeability is sufficient. The thickness is more preferably 150 μm or more, further preferably 200 μm or more, more preferably 750 μm or less, and further preferably 500 μm or less.

  Further, the fuel electrode may be composed of a fuel electrode support and a fuel electrode active layer. The thickness of the anode active layer is not particularly limited, but can be, for example, 5 μm or more and 30 μm.

3. Solid Electrolyte Layer As a material for the solid electrolyte layer, a general SOFC solid electrolyte layer material can be used without particular limitation. For example, the same material as the solid electrolyte material mentioned as the fuel electrode layer material can be used.

  In the case of an electrolyte support cell (ESC), the thickness of the solid electrolyte layer can be 50 μm or more and 300 μm or less. The thinner the thickness, the higher the power generation performance of the solid oxide fuel cell. If the thickness is 300 μm or less, sufficiently high power generation characteristics can be obtained. On the other hand, if the thickness is too thin, there may be a problem in strength, so the thickness is preferably 50 μm or more. The thickness is more preferably 60 μm or more, further preferably 80 μm or more, more preferably 200 μm or less, further preferably 180 μm or less, and particularly preferably 160 μm or less.

  In the case of an anode support cell (ASC), it is preferable to make the thickness of the solid electrolyte layer thinner from the viewpoint of power generation performance, for example, preferably 1 μm or more, more preferably 2 μm or more, and preferably 30 μm or less, 20 μm. The following is more preferable.

4). Reaction Prevention Layer As a material for the reaction prevention layer, a general SOFC reaction prevention layer material can be used without particular limitation. For example, ceria doped with the metal oxide mentioned as a material to be doped into ceramics as an air electrode material can be mentioned.

  The thickness of the reaction preventing layer is preferably as thin as possible from the viewpoint of power generation performance as long as the reaction between the air electrode layer and the solid electrolyte layer can be suppressed. For example, it can be about 0.5 μm or more and 5 μm or less.

5. Manufacturing Method Next, a manufacturing method of the air electrode and the solid oxide fuel cell according to the present invention will be described.

(1) Slurry preparation process At this process, the slurry for forming each layer is prepared by mixing the raw material powder of each layer, a solvent, and a binder at least. In addition, for example, a plasticizer, a dispersant, an antifoaming agent, and the like may be added to the slurry. A pore forming material such as carbon black may be further added to the electrode forming slurry.

  Of the raw material powders in each layer, the composite metal oxide, which is a solid electrolyte material, can be produced by a conventional method such as a coprecipitation method, a sol-gel method, a powder mixing method, or a spray pyrolysis method. For example, in the coprecipitation method, a compound containing each metal constituting the composite metal oxide is used as a raw material compound, weighed so that the relative mole number of each metal is a desired ratio, dissolved in nitric acid, etc. In addition, neutralization coprecipitation is performed. The obtained precipitate may be filtered off, washed with water, and then calcined. Alternatively, for example, each raw material compound may be mixed in an aqueous citric acid solution to form a composite citrate, which may be pre-baked.

  In the present invention, the specific surface area of the air electrode is specified. In order to obtain the desired specific surface area, in addition to the particle size of the raw material powder of the air electrode, the type of pore forming material, particle size, amount, use / non-use, printing plate mesh when forming the air electrode by screen printing What is necessary is just to select suitably the firing temperature at the time of air electrode formation, and a temperature increase rate.

  For example, in order to form the air electrode according to the present invention, the average particle diameter of the raw material powder is preferably about 0.01 μm or more and 5 μm or less. The average particle diameter is more preferably 0.05 μm or more or 0.1 μm or more, still more preferably 0.2 μm or more, more preferably 4 μm or less or 3 μm or less, and even more preferably 2 μm or less.

  In the baking step described later, the firing temperature of the air electrode is preferably 1000 ° C. or higher and 1300 ° C. or lower. If the firing temperature is less than 1000 ° C., the specific surface area of the air electrode may become too large. If the firing temperature exceeds 1300 ° C., the specific surface area of the air electrode may become too small. As a calcination temperature, 1005 degreeC or more is more preferable, 1010 degreeC or more is further more preferable, 1200 degreeC or less is more preferable, and 1150 degreeC or less is more preferable.

  Furthermore, it is preferable that the number of plate meshes during air electrode screen printing is 150 or more and 250 or less in the green body manufacturing process described later. If the number of printing plate meshes is less than 150, the specific surface area of the air electrode may be too small, and if the number of printing plate meshes exceeds 250, the specific surface area of the air electrode may be too large. . The number of plate meshes is more preferably 160 or more, still more preferably 170 or more, more preferably 240 or less, and even more preferably 230 or less.

  As a method of adjusting the specific surface area of the air electrode, it is preferable to adjust and combine the average particle diameter of the raw material particles, the firing temperature, and the number of printing plate meshes during air electrode screen printing.

(2) Green body production process In this process, green bodies of each layer are produced from the slurry.

  When a support green sheet is first prepared, the slurry is applied to a substrate such as a PET film and then dried to obtain a green sheet. In this step, a solid electrolyte support green sheet is produced in the case of ESC, and a fuel electrode support green sheet is produced in the case of ASC. Similarly, in the case of an air electrode support cell (CSC), an air electrode support green sheet may be prepared. However, in the case of a metal support cell (MSC), it is only necessary to form each layer on a metal support such as porous ferritic stainless steel, so that the support green sheet is not particularly required.

  When the green body of each layer is formed on the green sheet of the support or the support after firing, the slurry may be printed and then dried.

  The method for applying the slurry onto the substrate is not particularly limited, and a conventional method such as a doctor blade method or a calender roll method can be used. Specifically, the slurry is transported to a coating dam, cast on a substrate so as to have a uniform thickness by a doctor blade, and dried. When a green body is formed on a support or the like, screen printing or the like may be performed.

  The drying conditions may be appropriately adjusted according to the type of solvent used, but are usually 40 ° C. or higher, more preferably 80 ° C. or higher and about 150 ° C. or lower. Drying may be performed at a constant temperature, or may be performed by heating by successively raising the temperature sequentially such as 50 ° C., 80 ° C., and 120 ° C.

  What is necessary is just to adjust coating thickness suitably according to the thickness after baking of each layer made into the objective.

  The shape and size of the support green sheet may be determined according to the shape and size of the target solid oxide fuel cell. Alternatively, for example, a long support green tape may be produced and then cut into a desired shape and size.

  Preferably, after producing a long support green tape, it is cut into a desired shape. The shape of the sheet is not particularly limited, and may be matched to the shape of the target SOFC. For example, the shape may be a circle, an ellipse, a square with R (R), It may have a hole such as an ellipse or a square with R.

  The size of the support green sheet may be matched to the target SOFC, but may be, for example, a square having a side of 25 mm or more and 250 mm or less, or a circle having a diameter of 25 mm or more and 250 mm or less. The length or diameter is preferably 40 mm or more, more preferably 50 mm or more, and preferably 220 mm or less, more preferably 200 mm or less.

  When a green body is formed on a support or the like, the shape or size of the green body may be appropriately selected according to the shape or size of the support or the like.

(3) Firing step Next, the green body is fired. The timing of firing is not particularly limited, and may be fired each time a green body of each layer is formed. However, from the viewpoint of manufacturing efficiency and the like, it is preferable to fire a laminate of green bodies. For example, an anode active layer green body, an essentially solid electrolyte layer, and optionally a reaction-preventing layer green body are optionally formed on the anode support green sheet to form a green laminate, which is then baked and further reacted An air electrode green body may be formed on the prevention layer and fired again.

  The firing conditions may be adjusted as appropriate. For example, sintering is performed at 1000 ° C. or more and 1500 ° C. or less. If sintered at 1000 ° C. or higher, a sufficient firing effect can be obtained and high toughness can be obtained. On the other hand, if the sintering temperature is too high, the crystal grain size of the sheet becomes excessive and the toughness may be reduced, so the upper limit is set to 1500 ° C. However, the preferable firing temperature for obtaining the air electrode according to the present invention is as described above.

  The heating rate up to the firing temperature may be adjusted as appropriate, but can usually be about 0.05 ° C./min to 4 ° C./min.

  The shape and size of the support according to the present invention may be appropriately determined according to the shape and size of the target SOFC. For example, the shape is not particularly limited, such as a square such as a square or a rectangle, or a circle. The length of one side of the square or the diameter of the circle can be, for example, 20 mm or more and 200 mm or less. The length and diameter are more preferably 30 mm or more, further preferably 40 mm or more, more preferably 180 mm or less, and further preferably 150 mm or less.

  The shape and size of each layer on the support may be appropriately selected according to the shape and size of the support.

  Since the air electrode according to the present invention obtained as described above has a predetermined specific surface area, the electrode reaction proceeds favorably. Therefore, the SOFC having the air electrode exhibits extremely excellent power generation performance.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
(1) Production of fuel electrode support substrate green sheet 60 parts by mass of nickel oxide powder (manufactured by Shodo Chemical Co., Ltd., average particle size: 1.2 μm), 40 parts by mass of zirconia powder (“TZ-3Y20A” manufactured by Tosoh Corporation), empty 3 parts by mass of commercially available carbon black as the pore-forming material, 15 parts by mass of commercially available (meth) acrylic resin (number average molecular weight: 20,000) as the binder, and 2 parts by mass of commercially available α-olefin / maleic anhydride copolymer as the dispersant 2 parts by mass of a commercially available modified carboxyl group-containing polymer as a plasticizer, and 30 parts by mass of toluene and 24 parts by mass of ethyl acetate as a dispersion medium were mixed by a ball mill to prepare a slurry. Using the obtained slurry, a sheet was formed by the doctor blade method and dried at 80 ° C. for 2 hours to prepare a fuel electrode supporting substrate green sheet. In addition, about the thickness of the produced green sheet, it adjusted so that the thickness after baking might be set to 300 micrometers.

(2) Formation of green layer for fuel electrode active layer 60 parts by mass of nickel oxide powder (manufactured by Shodo Chemical Co., Ltd., average particle size: 1.2 μm), zirconia powder (“HSY-8.0” manufactured by Daiichi Rare Element Co., Ltd.) , Average particle size: 0.5 μm) 40 parts by weight, 12 parts by weight of a commercially available methacrylic resin as a binder, 5 parts by weight of commercially available dibutyl phthalate as a plasticizer, and 8 parts by weight of a commercially available sorbitan fatty acid ester surfactant as a dispersant The parts were premixed and then crushed using a three-roll mill (model “M-80S” manufactured by EXAK technologies, roll material: alumina) to prepare a fuel electrode layer paste.

  On the fuel electrode support substrate green sheet obtained in (1) above, a paste for the fuel electrode layer is screen-printed so that the thickness after firing is 15 μm, and dried at 80 ° C. for 30 minutes, for the fuel electrode active layer A green layer was formed.

(3) Formation of Green Layer for Electrolyte Layer 8 parts by weight of yttria stabilized zirconia powder (“HSY-8.0” manufactured by Daiichi Rare Element Co., Ltd., average particle size: 0.5 μm) as ceramics, 100 parts by mass as binder 7.5 parts by weight of commercially available ethyl cellulose, 67.5 parts by weight of commercially available α-terpineol as a solvent, 6 parts by weight of commercially available dibutyl phthalate as a plasticizer, and 10 parts by weight of a commercially available sorbitan acid ester surfactant as a dispersant After the preliminary mixing, the mixture was crushed using a three-roll mill (model “M-80S” manufactured by EXKT technologies, roll material: alumina) to prepare an electrolyte layer paste.

  The electrolyte layer paste is screen-printed on the fuel electrode active layer green layer obtained in the above (2) so that the thickness after firing is 10 μm, and dried at 80 ° C. for 30 minutes. A layer was formed.

(4) Formation of green layer for reaction prevention layer 100 parts by mass of ceria powder (manufactured by AGC Seimi Chemical Co., Ltd.) in which 20 mol% gadolinia is dissolved as a ceramic material, 7.5 parts by mass of ethyl cellulose commercially available as a binder, and commercially available as a solvent Α-terpineol 67.5 parts by weight, 8 parts by weight of commercially available dibutyl phthalate as a plasticizer, and 20 parts by weight of a commercially available sorbitan acid-based surfactant as a dispersant were premixed, and then a three-roll mill (model “M” -80S "manufactured by EXAK technologies, roll material: alumina) was crushed to prepare a reaction preventing layer paste.

  On the green layer for electrolyte layer obtained above, the paste for reaction-preventing layer is screen-printed so that the thickness after firing is 2 μm or less, and dried at 80 ° C. for 30 minutes. Formed.

(5) Firing The laminate obtained by laminating the fuel electrode supporting substrate green sheet, the fuel electrode active layer green layer, the electrolyte layer green layer, and the reaction preventing layer green layer obtained in the above order on one side after firing. Was punched out into a 6 cm square. After punching, firing was performed at 1350 ° C. in an air atmosphere for 3 hours to obtain a fuel electrode-supported half cell.

(6) Formation of air electrode layer La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (manufactured by AGC Seimi Chemical Co., average particle size: 0.6 μm) 80 parts by mass and 20 mol% gadolinia doped ceria (manufactured by AGC Seimi Chemical Co., Ltd.) (Average particle size: 0.5 μm) 20 parts by mass, 2 parts by mass of ethyl cellulose as a binder and 30 parts by mass of α-terpineol as a solvent are added and kneaded using a three-roll mill, and the air electrode layer A paste was prepared.

  On the reaction preventing layer of the fuel electrode supporting half cell obtained in (5) above, the air electrode layer paste is applied to a 1 cm × 1 cm square by screen printing so that the thickness after firing is 20 μm. And dried at 100 ° C. for 30 minutes to form a green layer for the air electrode layer. In the screen printing at the time of forming the air electrode layer, a screen mesh having 150 printing plate meshes was used. This air electrode green layer was baked at 1100 ° C. for 2 hours while applying a load of 2.3 kPa to obtain SOFC.

Example 2
In Example 1 above, a mixed powder of 80 parts by mass of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ and 20 parts by mass of 20 mol% gadolinia-doped ceria for forming an air electrode was prepared using La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ ( SOFC was obtained in the same manner except that the amount was changed to 100 parts by mass (manufactured by AGC Seimi Chemical Co., average particle size: 0.6 μm).

Example 3
In Example 1 above, a mixed powder of 80 parts by mass of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ for forming an air electrode and 20 parts by mass of 20 mol% gadolinia-doped ceria was mixed with La _0.6 Sr _0.4 CoO ₃ (AGC Seimi Chemical Co., Ltd.). SOFC was obtained in the same manner except that the mass was changed to 100 parts by mass.

Comparative Example 1
In Example 1 above, in order to increase the specific surface area of the air electrode, 3.5 parts by mass of commercially available carbon black was added as a pore forming agent during the preparation of the air electrode layer paste, and further the sintering of the air electrode was suppressed. The firing temperature was changed to 1000 ° C., and in addition, in the screen printing at the time of forming the air electrode green layer, SOFC was obtained in the same manner except that a screen mesh having 500 printing plate meshes was used.

Comparative Example 2
In Example 2 above, in order to increase the specific surface area of the air electrode, 3.5 parts by mass of commercially available carbon black was added as a pore-forming agent during the preparation of the air electrode layer paste, and further the sintering of the air electrode was suppressed. The firing temperature was changed to 1000 ° C., and in addition, in the screen printing at the time of forming the air electrode green layer, SOFC was obtained in the same manner except that a screen mesh having 500 printing plate meshes was used.

Comparative Example 3
In Example 3 above, in order to increase the specific surface area of the air electrode, 3.5 parts by mass of commercially available carbon black was added as a pore-forming agent during the preparation of the air electrode layer paste, and further the sintering of the air electrode was suppressed. The firing temperature was changed to 1000 ° C., and in addition, in the screen printing at the time of forming the air electrode green layer, SOFC was obtained in the same manner except that a screen mesh having 500 printing plate meshes was used.

Test Example 1: Measurement of specific surface area of air electrode It is difficult to measure the specific surface area of only the air electrode in SOFC, and it is also difficult to separate only a thin (20 μm in the above production example) air electrode from the cell. Therefore, an air electrode pellet for specific surface area measurement was separately prepared.

Specifically, in Examples 1 to 3, the number of plate meshes is 150 so that the air electrode pastes used in Examples 1 to 3 and Comparative Examples 1 to 3 have a thickness of 20 μm after firing. In Comparative Examples 1 to 3, screen printing was performed on a PET substrate using a screen mesh with 500 printing plate meshes and dried at 100 ° C. for 30 minutes to form a green layer for the air electrode layer. Next, the air electrode layer formed on the PET substrate was cut out so as to enter a hole having a volume of 1.0 to 6.0 mm ³ or less and 2.0 to 4.0 mmΦ, and transferred to a crucible. Note that the specific surface area measurement sample is a sheet-shaped air electrode layer cut out small, so that the specific surface area is generally larger, but it should be about the specific surface area of the air electrode according to the present invention. For example, it can be said that the specific surface area of the sample of the above size and the sheet state are the same. Then, it baked at 1100 degreeC for 2 hours similarly to the baking conditions of the air electrode, and produced the air electrode layer pellet for a specific surface area measurement. However, in Comparative Examples 1 to 3, the firing temperature was set to 1000 ° C. in order to suppress the sintering of the air electrode material and increase the specific surface area.

  About the obtained air electrode layer pellet for specific surface area measurement, the specific surface area was measured using the fully automatic specific surface area measuring apparatus ("Macsorb Model-1201" product made by Mounttech). The results are shown in Table 1.

Test Example 2: Battery Performance Evaluation Test For each SOFC produced in Examples 1 to 3 and Comparative Examples 1 to 3, the battery performance was evaluated by the following method. Specifically, the temperature was raised to 750 ° C. as the measurement temperature at a rate of 100 ° C./hour while supplying 100 mL / min of nitrogen to the fuel electrode and 100 mL / min of air to the air electrode. After raising the temperature, the flow rate of the gas on the outlet side of the fuel electrode and the air electrode was measured with a flow meter, and it was confirmed that there was no leakage. Next, a humidified mixed gas containing 6 mL / min of hydrogen and 194 mL / min of nitrogen was supplied to the fuel electrode, and 200 mL / min of air was supplied to the air electrode. After confirming that electromotive force is generated after 1 hour or more has passed and there is no leakage, adjust the fuel and gas to flow in a humidifier so that the total flow rate of hydrogen and water vapor is 200 mL / min. Battery performance evaluation test based on current-voltage characteristics after confirming that the electromotive force is in the range of 95 to 100% of the theoretical electromotive force after 10 minutes have passed since the electromotive force has been stabilized after being supplied to the fuel electrode Carried out. From the obtained current-voltage characteristics, the output densities of the SOFCs of Examples 1 to 3 and Comparative Examples 1 to 3 were determined. Table 1 shows the output density per unit area at a voltage of 0.70V.

  As shown in Table 1, when comparing the power density between SOFCs having the same composition, the SOFC of Example 1 is 7.5% compared with the SOFC of Comparative Example 1, and the SOFC of Example 2 is compared. It was confirmed that the output density was improved by 27.4% compared with the SOFC of Example 2 and the SOFC of Example 3 by 3.8% compared with the SOFC of Comparative Example 3.

  From the above results, it was confirmed that the power generation performance of the SOFC can be improved when the air electrode layer satisfies the specific surface area specified in the present invention.

Claims (5)

An air electrode for a solid oxide fuel cell, having a specific surface area of 0.1 m ² / g or more and less than 1.0 m ² / g. 2. The air electrode for a solid oxide fuel cell according to claim 1, comprising a perovskite complex oxide represented by the general formula ABO ₃ containing at least one of La and Sr at the A site.   The air electrode for a solid oxide fuel cell according to claim 1 or 2, wherein the thickness is 5 µm or more and 50 µm or less.   Solid oxide characterized in that at least a layer comprising a fuel electrode layer, a solid electrolyte layer, and an air electrode for a solid oxide fuel cell according to any one of claims 1 to 3 is laminated in this order. Single cell for physical fuel cell.   Furthermore, the single cell for solid oxide fuel cells of Claim 4 which has a reaction prevention layer between a solid electrolyte layer and the layer which consists of air electrodes for solid oxide fuel cells.