JP2012209013A - Electrolyte sheet for solid oxide fuel cell and method for manufacturing the same, and cell for solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a crack of an electrode in printing due to a burr, ununiformity and peeling of the electrode due to poor printing, and furthermore, breakage when single cells containing an electrolyte sheet and the electrode are laminated in series as a fuel cell, etc. by providing the electrolyte sheet which has certain specific surface roughness, suppresses burr height at the peripheral part of the electrolyte sheet and is excellent in acceptance rate by the burr height on the surface of the electrolyte sheet for the SOFC, and to establish a technology for efficiently manufacturing such a high performance electrolyte sheet.SOLUTION: There is provided a sheet which is an electrolyte sheet for a solid oxide fuel cell, and of which the relative ratio of flexural strength at three points measured by using one side (A side) and the other side (B side) of the electrolyte sheet as the upper surface, respectively, is 105-200%.

Description

  The present invention relates to an electrolyte sheet for a solid oxide fuel cell (hereinafter referred to as SOFC), a method for producing the same, and a cell for a solid oxide fuel cell using the same. In particular, the present invention relates to an oxygen ion conductive solid electrolyte sheet that has reduced burrs and has an excellent acceptance rate during mass production, a method for producing the same, and an electrolyte-supported cell (hereinafter referred to as ESC) using the electrolyte sheet.

In recent years, fuel cells have attracted attention as a clean energy source, and rapid improvement studies and practical application studies are being promoted for household power generation, commercial power generation, and automobile power generation. Among such fuel cells, a solid oxide fuel cell (SOFC) is expected as a power source for home use and business use because it has good efficiency and excellent long-term stability.

  In a solid oxide fuel cell (SOFC), a plurality of cells each having an electrode incorporated in an electrolyte sheet are stacked to form a stacked structure (stack). As a fuel cell, in order to maintain stable power generation performance over a long period of time, advanced quality control is required for each electrolyte sheet.

  One of the important factors as the quality control item of the electrolyte sheet is a so-called “burr” in which the height changes at the peripheral edge, for example. When such burrs are present, cracks occur during the printing of the electrodes, and the printing itself does not go well, making the electrodes non-uniform or easy to peel off. Further, since the fuel cell is formed by stacking single cells including an electrolyte sheet and an electrode in series, there is a risk that stress is concentrated on the burrs at the peripheral portion when the cells are stacked or during power generation.

  As an electrolyte sheet for a solid oxide fuel cell, a ceramic sheet mainly composed of zirconia or the like is used in terms of strength and power generation efficiency. As the solid oxide fuel cells are put into practical use, the demand for ceramic sheets is increasing and mass production has been started.

  A ceramic sheet is generally produced by forming a slurry containing ceramic powder into a ceramic green sheet and firing it. However, the quality problem becomes larger as mass production of ceramic sheets proceeds. ing. For example, if the incidence of defects such as defective burr height is close to 10%, the damage will be significant.

  Therefore, even in the mass production process, there is a need for a process in which the burr height is small and the occurrence rate of burr defects is small in the production unit (lot), that is, the shape of each piece is stable and flat. .

Various techniques for suppressing burrs at the peripheral edge of the sheet have been developed.
For example, Patent Document 1 describes a manufacturing method for reducing warpage by controlling a temperature increase rate in a firing process. Patent Document 2 describes a production method in which a protective sheet is inserted between ceramic green sheets and ceramic porous sheets which are alternately laminated and fired. Patent Document 3 discloses that a ceramic sheet with a small burr can be obtained by performing a punching process in which the angle of the Thomson blade is optimized.

However, these Patent Documents 1 to 3 do not describe the behavior of the three-point bending strength of the A-side and B-side of the sheet at all, and do not disclose pressing with a resin or metal having an appropriate roughness.
In addition, Patent Document 4 discloses a method for adjusting the amount of moisture absorption of the ceramic green sheet before firing, but it suppresses the occurrence of a defect rate of burrs and bends the A surface and B surface of the sheet at three points. There is no description about the behavior of strength, and there is no description about a specific pressing method.

JP 2001-247373 A JP 2007-302515 A Japanese Patent No. 4653135 JP-A-2005-212194

  The present inventors have found that there is a difference in the acceptance rate depending on the lot of the electrolyte sheet in the process of examining the acceptance rate according to the burr height of the electrolyte sheet for SOFC produced in large quantities.

  As a result of diligently examining what causes the difference in acceptance rate, there is a difference in the behavior of the three-point bending strength of the electrolyte sheet for SOFC between the electrolyte sheet group excellent in the acceptance rate and the electrolyte sheet group in which the satisfactory acceptance rate cannot be obtained. As a result, the inventors have found a characteristic SOFC electrolyte sheet that is the present invention.

  The present invention provides an electrolyte sheet having a specific surface roughness on the surface of the electrolyte sheet for SOFC, suppressing the burr height at the periphery of the electrolyte sheet, and having an excellent pass rate due to the burr height. is there. As described above, by reducing defects in burr height, cracks in electrode printing due to burrs, non-uniformity and peeling of electrodes due to printing defects, and further, a single cell including an electrolyte sheet and electrodes as a fuel cell in series It is possible to suppress breakage and the like when laminated on.

  The electrolyte sheet for a solid oxide fuel cell according to the present invention that could solve the above problems was measured with one side (A side) and the other side (B side) of the electrolyte sheet as the upper surface. It is characterized in that the sheet has a relative ratio of point bending strength of 105 to 200%.

  In addition, the surface roughness Ra of both surfaces is 0.005 μm or more and 0.3 μm or less, and the surface roughness Ra of at least one surface is 0.005 μm or more and 0.1 μm or less. It is characterized in that the relative ratio of the surface roughness Ra between the surface and the B surface is 150 to 600%.

  In addition, as a method for obtaining an electrolyte sheet, a green sheet of an electrolyte sheet is obtained by molding and drying a slurry containing raw material powder, a binder, a plasticizer, a dispersion medium, and the like, and the green sheet is fired to obtain a solid oxide. A method of forming a solid electrolyte sheet for a solid fuel cell is common. However, in the electrolyte sheet of the present invention, in the manufacturing process, the Ra of the surface facing the surface of the green sheet is 0 in the manufacturing process. And a method including a step of pressing between a resin or a metal having a thickness of 0.001 μm or more and 0.3 μm or less.

  The cell for a solid oxide fuel cell according to the present invention includes an electrolyte sheet produced by the method of the present invention.

  According to the present invention, the generation of burrs at the peripheral edge of the ceramic sheet can be remarkably suppressed. Therefore, the present invention is very useful industrially as one capable of improving the production efficiency of ceramic sheets whose required amount is increasing with the practical application of fuel cells.

  Under the above-mentioned problems, the present inventors have described in detail the manufacturing conditions of the electrolyte sheet and the physical properties of the electrolyte sheet (particularly the strength and surface roughness of the electrolyte sheet) that vary depending on the factors of the manufacturing conditions. I have been researching. As a result, if the electrolyte sheet of the present invention, which will be described in detail later, is adopted, it is determined that the burr height defect can be reduced by defining the specific surface roughness, and further, the object having the physical properties. The production conditions that can be obtained stably can be specified.

  Moreover, if the production method of the present invention is adopted, the target product can be obtained more reliably. However, since the index for obtaining the target product has been clarified in the present invention, the production method can be used in addition to the production method defined in the present invention. If the conditions are variously devised, it is of course possible to obtain an electrolyte that meets the object of the present invention.

In addition, although the manufacturing method of the electrolyte sheet concerning this invention is explained in full detail behind, the slurry containing raw material powder, a binder, a solvent, etc. is prepared, The said slurry is apply | coated and shape | molded on a resin film. For this reason, the electrolyte sheet inevitably has two surfaces, the surface on which the resin film is peeled off in the green sheet forming step and the opposite surface.
Hereinafter, a specific configuration of the present invention will be described in detail.

  First, the present inventors measured an electrolyte sheet for a solid oxide fuel cell that can solve the above-mentioned problems, with one side (A side) and the other side (B side) of the electrolyte sheet as the upper side. The characteristic was found where the relative ratio of the three-point bending strength was 105 to 200%. More preferably, it is 110-180%, More preferably, it is 120-150%. When the relative ratio is less than 105%, the effect of reducing the burr height defect rate is reduced and is not recognized. On the other hand, when it exceeds 200%, the strength of the smaller one becomes too weak to be practically used.

  Although the three-point bending strength varies depending on the composition of the electrolyte sheet, as described later, in the case of zirconia mainly composed of cubic crystals stabilized with scandia or yttria, which is the most preferable composition as an electrolyte sheet for a fuel cell, The higher intensity average value in the direction is 0.3 to 0.5 GPa, preferably 0.4 to 0.5 GPa.

  The three-point bending strength is measured by a method according to JIS R1601: 1995. That is, a sample obtained by cutting an electrolyte sheet into a strip of 5 mm width and 30 mm length with a # 100 high-speed diamond cutter was placed on two lower struts with a predetermined surface up and a span of 30 mm, and at room temperature. The maximum stress leading to fracture when a load was applied from two upper struts with a span of 20 mm at a crosshead speed of 0.5 mm / min was measured according to JIS R1601: 1995. The three-point bending strength obtained according to the formula “Calculation”. The relative ratio of the three-point bending strength is the average value obtained by measuring the three-point bending strength of ten points with the resin film peeling surface facing up in the above method, and the three points of ten points with the opposite surface facing up. Of the average value of the bending strength measured, the larger value is expressed as a percentage with the larger value as the denominator and the smaller value as the numerator.

Furthermore, in the electrolyte sheet of the present invention, the surface roughness becomes an important control factor.
That is, the effect is effective in an electrolyte sheet having a surface roughness Ra of 0.005 μm or more and 0.3 μm or less on both surfaces, and a surface roughness Ra of at least one surface of 0.005 μm or more and 0.1 μm or less. It was confirmed that it was remarkable. Preferably, the electrolyte sheet has a relative ratio of surface roughness Ra between the A surface and the B surface of 150% to 600%. More preferably, the relative ratio of the surface roughness Ra between the A plane and the B plane is 200 to 400%.

  By controlling the surface roughness Ra within the above range, when an electrode is formed on the electrolyte sheet as a cell, the electrode bondability tends to be good and the strength of the electrolyte sheet tends to be appropriate, which is practically preferable.

  Also, by controlling the relative ratio of the surface roughness Ra between the A surface and the B surface to the above range, the effect of reducing the burr height defect rate and the strength balance of both surfaces tend to be good, which is preferable in practice. .

  In the present invention, the surface roughness Ra is a surface property parameter defined by JIS B0601: 2001, and is measured by a stylus roughness meter SJ-201 manufactured by Mitutoyo Corporation. The relative ratio of surface roughness is the percentage of the surface roughness of the resin film peeled surface and the surface roughness of the opposite surface measured in the above method, with the larger value being the denominator and the smaller value being the numerator. It is represented by.

  In the electrolyte sheet specified by the present invention, the burr height at the periphery of the electrolyte sheet is suppressed, and the electrolyte sheet has an excellent pass rate due to the burr height. It is unclear for what reason the relative strength ratio and the relative surface roughness ratio have an effect on the burr height, but it is assumed that the residual stress on the surface of the electrolyte sheet is involved. Is done. These stresses are generated in the process of manufacturing the electrolyte sheet, and are mainly caused by shrinkage when drying the slurry, shrinkage when firing the green sheet, pressure of the green sheet, and surface irregularities (roughness). The divergence seems to have a complicated effect.

  The burr height defined in the present application refers to an altitude difference between the highest point and the lowest point when the shape of a section of 3 mm is measured from the outer peripheral edge of the electrolyte sheet in the direction perpendicular to the side toward the center.

The type of ceramic constituting the electrolyte sheet of the present invention is preferably a solid ceramic that contains at least one selected from the group consisting of zirconia-based oxides, LaGaO ₃ -based oxides, and ceria-based oxides. The electrolyte is exemplified.

Preferred zirconia-based oxides include oxides of alkaline earth metals such as MgO, CaO, SrO and BaO as stabilizers, Y ₂ O ₃ , Sc ₂ O ₃ , La ₂ O ₃ , CeO ₂ and Pr ₂ O. ₃ , Rd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O _3, etc. Oxide, Bi ₂ O ₃ , In ₂ O ₃ or the like selected from one or more oxides, or Al ₂ O ₃ , TiO ₂ , Ta as a dispersion strengthener Examples thereof include dispersion strengthened zirconia to which ₂ O ₅ , Nb ₂ O _{5 and the} like are added. Particularly preferred is a zirconia-based oxide stabilized with an oxide of at least one element selected from the group consisting of scandium, yttrium, cerium and ytterbium.

The LaGaO ₃ -based oxide is a composite oxide having a perovskite crystal structure, in which a part of La and Ga is substituted and dissolved by Sr, Y, Mg, etc. having a lower valence than each atom. , or for example for _{La 0.9 Sr 0.1 Ga 0.8 Mg 0.2} La 1-x , such as _{O 3 Sr x Ga 1-y} Mg y O 3, La 1-x Sr x Ga 1-y Examples include Mg _y Co ₂ O ₃ , La _1-x Sr _x Ga _1-y Fe _y O ₃ , La _1-x Sr _x Ga _1-y Ni _y O _{3, and the} like.

Preferred ceria-based oxides include CaO, SrO, BaO, Ti ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , _{gd 2 O 3, Tb 2 O} 3, Dy 2 O 3, Er 2 O 3, Tm 2 O 3, Yb 2 O 3, PbO, WO 3, MoO 3, V 2 O 5, Ta 2 O 5, Nb 2 Examples thereof include ceria-based oxides doped with one or more of O ₅ .

  These oxides can be used alone or in combination of two or more as required. Among those exemplified above, in order to obtain an electrolyte sheet having higher thermal, mechanical, chemical properties, and oxygen ion conductive properties, 3 to 10 mol% yttrium oxide or 4 to 12 mol% Tetragonal and / or cubic zirconia stabilized with scandium oxide or stabilized with 4-15 mol% ytterbium oxide is particularly preferred. Among these, zirconia stabilized with 8 to 12 mol% yttrium oxide and zirconia stabilized with 8 to 12 mol% scandium oxide are optimal. Further, since the crystal system may be rhombohedral when the amount of scandia is increased, ceria, alumina, or the like may be added as a third component in order to stabilize the crystal system mainly in a cubic system.

As the electrolyte sheet for a solid oxide fuel cell, a dense sintered body sheet having a thickness of 50 μm to 400 μm, more preferably 100 μm to 300 μm and a planar area of 50 cm ^{2 to} 900 cm ² is suitable.

The shape of the electrolyte sheet may be any of a circle, an ellipse, a square with a round shape, and the like, and one or two or more holes of the same circle, an ellipse, a square with an R, etc. are formed in these sheets. You may have. The sheet area is preferably 80 cm ² or more, more preferably 100 cm ² or more. In addition, this area means the area enclosed by the outer periphery including the area of the said hole, when there exists a hole in a sheet | seat. As a matter of course, the peripheral portion of the hole is also included in the peripheral region of the electrolyte referred to in the present invention.

  As a method for obtaining an electrolyte sheet, a green sheet of an electrolyte sheet is obtained by molding and drying a slurry containing raw material powder, a binder, a plasticizer, a dispersion medium, and the like, and the green sheet is fired to obtain a solid oxide form. A method of forming a solid electrolyte sheet for a fuel cell is generally used. However, in the electrolyte sheet of the present invention, in the manufacturing process, the Ra of the surface facing the surface of the green sheet of the electrolyte is 0.001 μm. As mentioned above, the method including the process of pressing between resin or metal which is 0.3 micrometer or less can be mentioned.

  The roughness of the surface facing the green sheet is more preferably 0.01 μm or more and 0.1 μm or less.

  The material of the resin or metal is not particularly limited. For example, an acrylic resin, a polycarbonate resin, a polyethylene resin, a polyester resin, a vinyl chloride resin, a vinylidene chloride resin, a paper subjected to a smooth treatment, a cemented carbide tungsten whose surface is polished, Examples include stainless steel, die steel, stellite, special steel, and cemented carbide. The resin or metal is used in the form of a plate or a film. The thickness of the plate or film is preferably 0.05 to 50 mm. A method of pressing between these resins or metals is not particularly limited, but a method using a single-screw press, a roll press, or the like can be adopted.

  Examples of the roll press machine include a roll press machine (manufactured by Toyo System Co., “TOSMAC-2000”), a sheeting roll machine (manufactured by Kansai Roll Co., “MC-P500J”), a roller press machine (manufactured by Ono Roll Co., Ltd.), and the like. However, it is not limited to these. In the case of a metal, instead of using it in the form of a plate or film, the surface roughness of the metal pressure surface of the pressure device may be adjusted and used.

  When pressurizing, the green sheet may be pressed after both sides or one side of the green sheet is overlaid on the above resin or metal, or the above resin or metal may be joined to the press surface of a press. The pressurization temperature may be room temperature, but may be heated and controlled to 100 ° C. or lower. The pressure is preferably 10 to 40 MPa, more preferably 15 to 30 MPa. When the pressure is less than 10 MPa, the effect of pressurization is difficult to obtain, and the effect of reducing the burr height defect rate is reduced and is not recognized. On the other hand, if it exceeds 40 PMa, the green sheet may be deformed and the size after firing may be greatly affected.

  Here, in order to effectively pressurize, it is preferable that the tensile fracture elongation in the tensile test of the green sheet is 5% to 50% and the tensile yield strength is 2.0 MPa to 20 MPa. More preferably, the tensile elongation at break is 8% to 30% and the tensile yield strength is 3.0 MPa to 15 MPa.

  By the way, when the tensile elongation at break is less than 5% and the tensile yield strength exceeds 20 MPa, the effect of pressurization cannot be obtained sufficiently, and the effect of reducing the defect rate of burr height is reduced and is not recognized. When the fracture elongation exceeds 50% and the tensile yield strength is less than 2.0 MPa, the green sheet may be deformed by pressurization and the size after firing may be greatly touched.

  The tensile fracture elongation and the tensile yield strength are measured according to the plastic tensile test method of JIS K7113. Specifically, using a universal material testing machine (model 4301 manufactured by Instron Japan Co., Ltd.), a green sheet cut into a No. 2 type test piece shape, while holding both ends of the test piece with a jig The test piece was pulled at a tensile rate of 10 mm / min, and the tensile elongation at break and the tensile yield strength were measured.

  The type of binder used in the slurry for forming the electrolyte green sheet is not particularly limited, and conventionally known organic binders can be appropriately selected and used. Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetal resins. And vinyl formal resins, vinyl alcohol resins, waxes, celluloses such as ethyl cellulose, and the like.

  Among these, from the point of moldability and strength of the green sheet, thermal decomposability at the time of firing, etc., carbon number 10 such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc. Alkyl acrylates having the following alkyl groups; and alkyls having 20 or less carbon atoms such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate and the like. Alkyl methacrylates having a group; hydroxyethyl acrylate, hydroxypropyl Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having a hydroxyalkyl group such as acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; aminoalkyl acrylates or aminoalkyl methacrylates such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate; acrylic acid and methacrylic acid And a number average molecular weight of 20,000 to 250,000 obtained by polymerizing or copolymerizing at least one selected from carboxyl group-containing monomers such as maleic acid and maleic acid half esters such as monoisopropylmalate More preferably, 50,000 to 200,000 (meth) acrylate copolymers are recommended as preferred.

  These organic binders can be used alone or in combination of two or more as necessary. Particularly preferred is a monomer polymer containing 60% by mass or more of isobutyl methacrylate and / or 2-ethylhexyl methacrylate.

  The use ratio of the raw material powder and the binder is preferably in the range of 5 to 30 parts by weight, more preferably 10 to 20 parts by weight with respect to the former 100 parts by weight. Insufficient strength and flexibility make it impossible to sufficiently roughen to the desired surface roughness. On the other hand, if the amount is too large, it is difficult not only to adjust the viscosity of the slurry, but also to decompose the binder component during firing. The release becomes large and intense, making it difficult to obtain a flat ceramic sheet.

  The solvent used for the production of the green sheet includes alcohols such as water, methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol; ketones such as acetone and 2-butanone; pentane, hexane and butane. Aliphatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and the like; and acetates such as methyl acetate, ethyl acetate, and butyl acetate are appropriately selected and used. These solvents can also be used alone, or two or more of them can be used in combination as appropriate. The amount of these solvents used should be appropriately adjusted in consideration of the viscosity of the slurry at the time of forming the green sheet, and preferably the slurry viscosity is in the range of 1 to 50 Pa · s, more preferably 2 to 20 Pa · s. It is better to make adjustments.

  In the preparation of the slurry, in order to promote peptization and dispersion of the raw material powder, polymer electrolytes such as polyacrylic acid and ammonium polyacrylate; organic acids such as citric acid and tartaric acid; isobutylene or styrene and maleic anhydride Copolymers, ammonium salts and amine salts thereof; dispersants such as copolymers of butadiene and maleic anhydride and ammonium salts thereof; and dibutyl phthalate and phthalic acid for imparting flexibility to green sheets Phthalic acid esters such as dioctyl; glycols such as propylene glycol and glycol ethers; polyester plasticizers such as phthalic polyester, adipic acid polyester, and sebacic acid polyester; and surfactants and antifoams An agent or the like can be added as necessary.

  The slurry comprising the above raw material blend is formed by the method as described above and dried to obtain an electrolyte green sheet. The forming method is not particularly limited, and a sheet having an appropriate thickness is obtained using a conventional method such as a doctor blade method or an extrusion method. Then, it is set as the unprocessed green sheet for electrolytes by drying. Drying conditions are not particularly limited, and for example, drying may be performed at a constant temperature of room temperature to 150 ° C., or heating may be performed by successively raising the temperature in the order of 50 ° C., 80 ° C., and 120 ° C. In the case of a doctor blade method or the like, the slurry is dried on a carrier film such as a polyester film.

  Next, if necessary, the green sheet is processed into a green sheet of an appropriate size, and as described above, pressure treatment is performed with a resin or metal having a specified surface roughness.

  To process green sheets of appropriate size, punching with double or single blade so-called Thomson blade, cutting with metal mold, slitting with slitter, laser processing, water processing, plotter processing, rotary cutter, etc. However, in order to efficiently mass-produce, cutting with a double-edged or single-edged blade, cutting with a mold, etc. is preferable. To process a ceramic green sheet, From the viewpoint of durability, it is more preferable to use a mold. In these processes, the dried green sheet is generally peeled off from the carrier film and only the green sheet is processed. However, the green sheet may be peeled off after the entire carrier film is processed. In addition to the above order, the processing can also be performed after the pressure treatment.

  The electrolyte green sheet that has undergone the pressure treatment step is fired to obtain the electrolyte sheet of the present invention. Specific firing conditions are not particularly limited, and may be based on a conventional method. For example, in order to remove organic components such as a binder and a plasticizer from the surface roughened electrolyte green sheet, the treatment is performed at 150 to 600 ° C., preferably 250 to 500 ° C. for about 5 to 80 hours. Subsequently, the surface roughening electrolyte of this invention is obtained by carrying out holding | maintenance baking at 1000-1600 degreeC, Preferably 1200-1500 degreeC for 2 to 10 hours.

  The surface roughness electrolyte sheet surface roughness of the present invention obtained above is approximately 70 to 90% with respect to the surface roughness of the electrolyte green sheet.

  The solid oxide fuel cell of the present invention is characterized by using the above electrolyte sheet. Therefore, efficient power generation is possible and stable power generation over a long period is possible.

  The solid oxide fuel cell has a fuel electrode formed on one surface of the electrolyte sheet of the present invention and an air electrode formed on the other surface by screen printing or the like. Here, the order of formation of the fuel electrode and the air electrode is not particularly limited, but an electrode having a low necessary firing temperature is first formed on the electrolyte sheet and then fired, or the fuel electrode and the air electrode may be fired simultaneously. Good. The surface of the electrolyte sheet on which the fuel electrode and air electrode are formed depends on the direction of the strength of the electrolyte sheet, the direction of the strength of the cell when the electrode is formed, and the surface roughness Ra of the electrode and the electrolyte sheet. It is necessary to make a judgment with consideration.

  Further, an intermediate layer as a barrier layer may be formed between the electrolyte sheet and the air electrode layer in order to prevent generation of a high resistance component due to a solid phase reaction between the electrolyte and the air electrode. In this case, the fuel electrode is formed on the surface on which the intermediate layer is formed or the surface opposite to the surface to be formed, and the air electrode is formed on the intermediate layer. Here, the order of formation of the intermediate layer and the fuel electrode is not particularly limited, and the intermediate layer and the fuel electrode are formed by applying and drying the intermediate layer paste and the fuel electrode paste on each surface of the electrolyte sheet, respectively, and then firing the respective layers. May be formed by firing at the same time.

  The material for the fuel electrode and the air electrode, further the intermediate layer material, and the paste application method, drying conditions, and firing conditions for forming them can be implemented in accordance with conventionally known methods.

  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. It is also possible to implement, and they are all included in the technical scope of the present invention.

Example 1
(1) As a raw material powder for producing a solid electrolyte green sheet, stabilized zirconia powder in which 10 mol% scandium oxide 1 mol% cerium oxide is dissolved (trade name “10Sc1CeSZ”, d ₅₀ ; .6 μm) 100 parts by mass of a methacrylic copolymer binder (number average molecular weight; 100,000, glass transition temperature: 0 ° C.) in terms of solid content, 18 parts by mass, and sorbitan acid trioleate 2 as a dispersant Part by weight, 3 parts by weight of dibutyl phthalate as a plasticizer, and 50 parts by weight of a mixed solvent of toluene / ethyl acetate (mass ratio = 1/1) as a solvent are placed in a nylon mill charged with zirconia balls and milled for 40 hours. A slurry was prepared. The obtained slurry was transferred to a jacketed round bottom cylindrical vacuum degassing vessel equipped with a bowl-shaped stirrer, and under reduced pressure (about 4 to 21 kPa) at a jacket temperature of 40 ° C. while rotating the stirrer at a speed of 30 rpm. Concentrated and defoamed, adjusted to a viscosity of 3 Pa · s at 25 ° C., and continuously applied onto a polyethylene terephthalate (PET) film by the doctor blade method as a slurry for coating. Dry at ℃ and 110 ℃ to obtain a long green sheet for solid electrolyte, peel off from the PET film, and then cut with a mold to obtain a green sheet of about 160mm □ (□ represents a substantially square) It was.

(2) Pressurization of green sheet Fabricated in (1) above between two polyethylene terephthalate (PET) films (polyester resin) having a size of 170 mm □, a thickness of 188 μm, and a surface roughness Ra of 0.04 μm. 160 mm □ was sandwiched and pressed with a roll press. When the pressure applied using pressure sensitive paper was estimated, it was about 20 MPa.

(3) Firing of green sheet Subsequently, the roughened green sheet obtained in (2) above was degreased by sandwiching the top and bottom of the roughened green sheet with a 99.5% alumina porous plate (porosity: 30%), and then at 1420 ° C. for 3 hours. The mixture was heated and fired to obtain a 10Sc1CeSZ electrolyte sheet having a thickness of about 120 mm □ and a thickness of 0.18 mm.

(4) Evaluation of electrolyte sheet The surface roughness Ra of the center part of the front and back two surfaces of the electrolyte sheet obtained in (3) was measured with a stylus type roughness meter SJ-201 manufactured by Mitutoyo Corporation. Table 1 shows the surface roughness Ra and the larger value / smaller value of each surface.

  Next, using a laser optical contacted three-dimensional shape measuring device (trade name “UBC-14 type”, Microfocus Expert, manufactured by UBM), at the center of the four sides of each electrolyte sheet, Laser light was irradiated in a range of 3 mm in the perpendicular direction toward the center. The light source is a semiconductor laser (780 nm), a spot diameter of 1 μm, and a vertical resolution of 0.01 μm. By analyzing the reflected light in a three-dimensional shape, the difference in height between the highest point and the lowest point at the peripheral edge was obtained. In 1000 ceramic sheets, the ratio of those having a measured height difference of 100 μm or more was calculated as the burr height rejection rate. The results are shown in Table 1.

  Further, 20 strip-shaped test pieces having a width of 5 mm and a length of 30 mm were cut out from the electrolyte sheet with a # 100 high-speed diamond cutter (Calactron Co., Ltd.). The 20 sheets were placed on two lower struts with a span of 30 mm for each test piece, 10 sheets with the resin film peeling surface facing up and 10 sheets with the opposite surface facing up, and the span was measured at room temperature. The maximum stress that led to the fracture when a load was applied from two 20 mm upper struts at a crosshead speed of 0.5 mm / min was determined to obtain a three-point bending strength. Of the average value of the 10-point three-point bending strength measurement value with the resin film peeling surface up and the average value of the 10-point three-point bending strength measurement value with the opposite surface up, the larger value is the denominator, The relative ratio was determined as a percentage using the smaller value as the numerator and is shown in Table 1.

(5) Production of Solid Oxide Fuel Cell Cell A solid oxide fuel cell was produced by forming a fuel electrode and an air electrode on both sides of the 10Sc1CeSZ electrolyte sheet. Specifically, 70 parts by mass of nickel oxide powder (d ₅₀ : 0.9 μm) obtained by thermally decomposing basic nickel carbonate in a region of about 110 mmφ excluding a region having a width of 5 mm on one side of the 10Sc1CeSZ electrolyte sheet, ceria particles A fuel electrode paste made of zirconia particles is formed by screen printing, and the opposite surface is similarly screen-printed with an intermediate layer paste made of 20 mol% samarium-doped ceria in a region of about 110 mmφ excluding a region having a width of 5 mm. Formed and baked at 1300 ° C. to form a fuel electrode and an intermediate layer on the electrolyte.

Next, on the intermediate layer, 80 parts by mass of commercially available strontium-doped lanthanum iron cobaltate (La _0.6 Sr _0.4 Fe _0.8 Co _0.2 O ₃ ) powder and a commercially available 20 mol% gadolinia-doped ceria powder An air electrode paste composed of 20 parts by mass was formed by screen printing and baked at 950 ° C. to obtain a cell having a four-layer structure.

(Example 2)
An electrolyte sheet was prepared in the same manner as in Example 1 except that pressing was performed at 18 MPa for 1 second with a uniaxial press. The evaluation results are also shown in Table 1.

(Example 3)
An electrolyte sheet was prepared in the same manner as in Example 1 except that a PET film (Ra = 0.04 μm) was attached to the pressure surface of the uniaxial press and the green sheet of Example 1 was pressed at 10 MPa for 1 second. The evaluation results are also shown in Table 1.

Example 4
An electrolyte sheet was prepared in the same manner as in Example 1 except that a polished metal plate (Ra = 0.06 μm) was attached to the pressing surface of the uniaxial press and the green sheet of Example 1 was pressed at 15 MPa for 1 second. The evaluation results are also shown in Table 1.

(Example 5)
A polishing metal plate (Ra = 0.06 μm) was attached to the pressure surface of a uniaxial press, heated to 40 ° C., and the green sheet of Example 1 was pressed at 28 MPa for 1 second, as in Example 1. An electrolyte sheet was produced. The evaluation results are also shown in Table 1.

(Comparative Example 1)
A green sheet was prepared by a method (without pressure) corresponding to the example and comparative example of Patent Document 3, and the three-point bending strength of the sheet was evaluated. That is, an electrolyte sheet was prepared in the same manner as in Example 1 except that the green sheet was not pressurized. The evaluation results are also shown in Table 1.

(Comparative Example 2)
An electrolyte sheet was prepared in the same manner as in Example 1 except that commercially available cardboard (Ra = 3.2 μm) was attached to the pressure surface of the uniaxial press and the green sheet of Example 1 was pressed at 32 MPa for 1 second. The evaluation results are also shown in Table 1.

  As shown in the Examples, it can be seen that the electrolyte sheet in which the relative ratio of the three-point bending strength satisfies a specific range has a very low incidence of burr height defects. For this reason, the relative ratio of the three-point bending strength measured using one side (A surface) and the other side (B surface) of the electrolyte sheet as the upper surface is important for reducing burr height defects. Recognize.

  [Technical Field] The present invention relates to an electrolyte sheet for a solid oxide fuel cell and a cell using the electrolyte sheet. Since burr of the electrolyte sheet is reduced, the reliability and cost of the solid oxide fuel cell are reduced. It can contribute.

Claims (6)

An electrolyte sheet for a solid oxide fuel cell,
A solid oxide battery characterized in that the relative ratio of the three-point bending strength measured with one side (A side) and the other side (B side) of the electrolyte sheet as an upper surface is 105 to 200%. Electrolyte sheet. 2. The electrolyte sheet according to claim 1, wherein the surface roughness Ra is 0.005 μm or more and 0.3 μm or less on both surfaces. The electrolyte sheet according to claim 2, wherein the surface roughness Ra of at least one surface is 0.005 μm or more and 0.1 μm or less. The electrolyte sheet according to any one of claims 1 to 3, wherein a relative ratio of surface roughness Ra between the A surface and the B surface is 150% to 600%. A green sheet of an electrolyte sheet is obtained by molding and drying a slurry containing raw material powder, a binder, a plasticizer and a dispersion medium, and the green sheet is fired to obtain a solid electrolyte sheet for a solid oxide fuel cell. A method of manufacturing comprising:
5. The method according to claim 1, further comprising a step of pressing the electrolyte green sheet sandwiched between a resin or a metal having Ra of 0.001 μm or more and 0.3 μm or less on a surface facing the surface of the green sheet. The manufacturing method of the electrolyte sheet. The cell for fuel cells using the electrolyte sheet in any one of Claims 1-4.