JP2009104990A - Method of manufacturing electrolyte sheet for solid oxide fuel cell and electrolyte sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrolyte sheet for a solid oxide fuel cell showing stable excellent oxygen ion conductivity, having sufficient mechanical strength in handling by suppressing generation of micro closed pores in an electrolyte matrix, having stable strength characteristics even under an operation condition, and having high performance when used as a solid electrolyte membrane for the fuel cell; and to provide the electrolyte sheet obtained by the manufacturing method. <P>SOLUTION: The electrolyte sheet for the solid oxide fuel cell is manufactured by using raw material ceramic powder comprising electrolyte powder having an average particle size of 0.2-1 μm and oxide nano particles (excepting alumina nano particles) having an average particle size of 10-100 nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an electrolyte sheet for a solid oxide fuel cell, and in particular, exhibits stable and excellent oxygen ion conductivity, mechanical strength sufficient for handling, and stable strength characteristics even under operating conditions. A method for producing an electrolyte sheet for a solid oxide fuel cell having excellent performance as a solid electrolyte membrane for a fuel cell, an electrolyte sheet obtained by the production method, and a solid oxide fuel comprising the electrolyte sheet The present invention relates to a battery cell.

  In recent years, fuel cells have attracted attention as a source of clean energy, and their practical use has been rapidly researched for practical use such as household power generation, commercial power generation, and automobile power generation. As a solid oxide fuel cell, an electrolyte-supported cell in which a sheet-like solid oxide having oxygen ion conductivity is used as an electrolyte membrane, an anode electrode on one side, and a cathode electrode on the other side is provided in the vertical direction. A stack having a large number of layers is used as a typical basic structure and is operated at 800 to 1000 ° C. In the case of this structure, the electrolyte sheet is required to be thin in order to suppress the loss of current as much as possible while satisfying its required strength, and each individual electrolyte sheet is subjected to a large lamination load at high temperature, The thermal history between 800 to 1000 ° C. during operation and room temperature during stoppage is repeatedly received. As a result, the electrolyte sheet may be damaged by a load more than it can withstand. Since the fuel cells are connected in series, if one electrolyte sheet is completely damaged, the power generation capability of the entire fuel cell is damaged. In particular, stabilized zirconia electrolytes and lanthanum gallate electrolytes having a cubic crystal structure with high oxygen ion conductivity are not strong enough as a free-standing film, and have poor toughness, so when used in an electrolyte free-standing film cell It has become a big problem.

Therefore, a technique for increasing strength by dispersing alumina in Y ₂ O ₃ -containing stabilized zirconia (Japanese Patent Laid-Open No. 2-177265), and dispersing alumina or mullite as a high-strength composite material in a scandia-stabilized zirconia electrolyte (Japanese Patent Laid-Open No. Hei 2). 7-69720). In addition, the present inventors have proposed several techniques (JP 2001-163666, JP 2003-22821, JP 2003-22822). In these technologies, an oxide of a specific element is added to a yttria-stabilized zirconia electrolyte as a dispersion-strengthened oxide, an oxide of a specific element is added to a scandia-stabilized zirconia electrolyte, or a composite oxide containing a specific element is added. Excellent strength and strength sustainability can be imparted and improved.

  However, the additive used in the above technology is an insulating material and has a certain effect on increasing the strength. However, even if it is added in a small amount, the oxygen ion conductivity of the zirconia electrolyte, particularly its aging stability, is adversely affected. It turned out to be an effect.

JP-A-2-177265 JP 7-69720 A JP 2001-163666 A JP 2003-22821 A JP 2003-22822 A

  As described above, in order for a solid oxide fuel cell to be widely put into practical use, it is necessary to further improve performance and reliability. As a result of research, the present inventors inevitably have minute closed pores of about 0.1 to 0.2 μm in the matrix of the electrolyte sheet even when an oxide or the like that functions as a dispersion stabilizer is added. In order to reduce the electrical conductivity of the solid electrolyte and reduce the conductivity of the solid electrolyte, even if a small amount of insulating oxide is added, the sheet strength stability is not sufficiently reliable. It was also found to have a great influence on the stability over time.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research on additive materials and their physical properties, particularly on stabilized zirconia electrolyte materials and lanthanum gallate electrolyte materials, and production conditions capable of mass production. By using oxide nanoparticles with an average particle size of 10 to 100 nm as an additive, generation of minute closed pores in the electrolyte matrix is suppressed, the electrolyte is densified, and mechanical strength and operation sufficient for handling It has been found that an electrolyte sheet of a solid oxide fuel cell having stable strength characteristics can be obtained even under conditions.

Furthermore, by using oxide nanoparticles that have conductivity of 10 ⁻⁴ S / cm or more at 800 ° C., stable and excellent oxygen ion conductivity as a solid electrolyte membrane for fuel cells. I also found out. The electrolyte sheet is preferably produced by the following method.

  That is, by defining a physical property of the electrolyte powder and the conductive oxide nanoparticles and including a milling process for defining the order of addition of the electrolyte powder and the oxide nanoparticles at the time of preparing the slurry, the oxide nanoparticles are converted into the electrolyte powder. The dispersibility of the electrolyte matrix can be made uniform, and even after the subsequent green sheet forming step and subsequent firing step, the minute closed pores in the electrolyte matrix can be reduced, and the quality of the electrolyte sheet can be reduced and the electrolyte sheet can be manufactured with high productivity. .

  The method for producing an electrolyte sheet for a solid oxide fuel cell according to the present invention includes a milling step for preparing a slurry containing raw ceramic powder, a binder, a solvent, and a dispersant, and forming the green sheet by forming the slurry into a sheet. In a method for producing a solid electrolyte sheet comprising a forming step and a firing step in which the green sheet is cut into a predetermined shape and fired, the raw material ceramic powder is an electrolyte powder having an average particle size of 0.2 to 1 μm and an average particle size of 10 to 10. It consists of 100 nm oxide nanoparticles (excluding alumina nanoparticles).

  The said raw material ceramic powder can use what is 80-99.99 mass% of said electrolyte powder, and 0.01-20 mass% of said oxide nanoparticles.

The oxide nanoparticles having a conductivity at 800 ° C. of 10 ⁻⁴ S / cm or more can be used.

  The electrolyte powder is selected from stabilized zirconia and / or lanthanum gallate-based perovskite oxide in which 3 to 15 mol% of at least one oxide selected from scandium oxide, yttrium oxide and ytterbium oxide is dissolved. What is at least 1 sort (s) or more can be used.

  The oxide nanoparticles are at least selected from stabilized zirconia, ceria and yttrium oxide, gadolinium oxide, and samarium oxide in which at least one oxide selected from zirconia and scandium oxide, yttrium oxide, and ytterbium oxide is dissolved. A material which is a stabilized bismuth oxide in which at least one oxide selected from dope ceria, bismuth oxide, yttrium oxide, niobium oxide, and tungsten oxide, in which one oxide is dissolved, can be used.

  In the production method of the present invention, the milling step is a first step (milling I) in which 0.01 to 20 parts by mass of the oxide nanoparticles are milled with a dispersant and a solvent, and the slurry obtained in the first step. The second step (milling II) for further milling after adding 80 to 99.99 parts by mass of the above electrolyte powder, and then the third step for further milling after adding a binder and a plasticizer to the slurry obtained in the second step ( A process consisting of milling III) can be used.

  The dispersing agent is a nonionic surfactant, and the solvent containing an alkyl alcohol having 2 to 4 carbon atoms can be used.

  Furthermore, it can also be set as a solid oxide fuel cell using the electrolyte sheet concerning this invention.

  The solid oxide fuel cell electrolyte sheet containing a small amount of conductive oxide nanoparticles with specific composition and physical properties according to the present invention improves the long-term stabilization of oxygen ion conductivity of the solid electrolyte and also improves the strength sustainability. Thus, a solid electrolyte sheet excellent in conductivity and strength characteristics can be provided. Further, it has become possible to provide a production method capable of mass production that can efficiently produce a stabilized zirconia electrolyte sheet and a lanthanum gallate electrolyte sheet excellent in both characteristics with little quality fluctuation. Furthermore, the electrolyte sheet of the present invention stabilizes the conductivity and strength, and as a result of having a high Weibull coefficient and increasing the reliability as an electrolyte, the stabilized zirconia electrolyte sheet and lanthanum gallate electrolyte sheet of the present invention The electrolyte-supported fuel cell used also has excellent power generation performance and durability.

  Hereinafter, embodiments of the present invention will be specifically described.

  In the first invention according to the present invention, the raw material ceramic powder is composed of an electrolyte powder having an average particle size of 0.2 to 1 μm and oxide nanoparticles having an average particle size of 10 to 100 nm (excluding alumina nanoparticles). Is an electrolyte sheet for a solid oxide fuel cell.

  According to a second aspect of the present invention, there is provided a method for producing an electrolyte sheet for a solid oxide fuel cell according to the present invention, wherein a milling step of preparing a slurry containing a raw ceramic powder, a binder, a solvent, and a dispersant, When manufacturing a sheet-like solid electrolyte comprising a step of forming a slurry to form a green sheet, and a firing step of cutting the green sheet into a predetermined shape and firing, the raw ceramic powder has an average particle size of 0.2. It is a manufacturing method characterized by including oxide nanoparticles (excluding alumina nanoparticles) having an average particle diameter of 10 to 100 nm together with an electrolyte powder of ˜1 μm.

  The oxide nanoparticles used in the present invention are dispersed in an electrolyte matrix and act as a dispersion strengthening agent like conventional alumina as described above. It has the effect of improving the strength characteristics by reducing the minute closed pores that are inevitably generated.

  The raw material ceramic powder is an electrolyte powder having an average particle size of 0.2 to 1 μm and oxide nanoparticles having an average particle size of 10 to 100 nm (excluding alumina nanoparticles). By using the powder, the following effects are found.

  The reason for using oxide nanoparticles having an average particle diameter of 10 to 100 nm (excluding alumina nanoparticles) is as follows. In the zirconia electrolyte matrix as disclosed in the above Patent Documents 3 to 5, there are many small closed pores of 0.1 to 0.2 μm or less that cause the stability of strength properties to be impaired. Even if an electrolyte powder having an average particle size of 0.1 μm to 2 μm, which is equal to or larger than the closed pore diameter, is uniformly dispersed, it is difficult to greatly reduce the closed pores. However, it was found that the use of nanoparticles having an average particle diameter of 10 to 100 nm dramatically reduced the closed pores and improved the electrolyte strength characteristics.

  This is because the oxide nanoparticles of 10 nm or more and 100 nm or less exist between the stabilized zirconia powder or the lanthanum gallate powder as the electrolyte matrix, so that the electrolyte powder is sintered in the closest packing state. It is considered that the generation of pores in the later electrolyte matrix can be suppressed, the density can be increased, and the strength characteristics can be improved. The above-mentioned nanoparticle addition effect is considered to be more easily packed when the average particle diameter of the oxide nanoparticles is less than 10 nm, but the nanoparticles themselves are extremely aggregated and cannot be uniformly dispersed in the electrolyte matrix. In addition, since the specific surface area of the nanoparticles is remarkably increased, handling becomes extremely difficult. On the other hand, when the thickness exceeds 100 nm, the close-packed state is insufficient, the effect of suppressing the generation of vacancies is reduced, and it is difficult to increase the density. The average particle diameter of the oxide nanoparticles is preferably 10 to 90 nm, more preferably 12 to 80 nm. The electrolyte matrix is a sintered body obtained by sintering an unfired molded body after the electrolyte powder is molded into a predetermined shape, and indicates one in which oxide nanoparticles are dispersed. .

As the material for the oxide nanoparticles used in the present invention, any oxide or composite oxide other than alumina can be used. Specific oxides include oxides of alkaline earth elements such as Mg, Ca, Sr, and Ba, oxides of rare earth elements of Sc, Y, La, Ce, Pr to Yb up to element numbers 57 to 71, Transition metal element oxides such as Ti, Zr, V, Ta, Cr, W, Mn, Fe, Co, Ni, Cu and Zn, and typical metal elements such as B, Ga, Si, Ge, Sn, Sb and Bi The oxide of is illustrated. In addition, examples of the composite oxide include perovskite-type composite oxides such as BaTiO ₃ , LaGaO ₃ , LaMnO ₃ , LaFeO ₃ , LaCoO ₃ , spinel-type composite oxides such as Al ₂ MgO ₄ , Al ₂ CoO ₄ , mullite, and rare earths. Examples include zirconia stabilized with an element or the like, ceria doped with a rare earth element, or the like, but zirconia stabilized with a rare earth element or the like, or ceria doped with a rare earth element or the like is preferable.

Among the oxide nanoparticles, a material having an electric conductivity at 800 ° C. of 10 ⁻⁴ S / cm or more is particularly preferable. Since the conductivity at 800 ° C. is 10 ⁻⁴ S / cm or more, the decrease in conductivity due to the addition of a conventional insulating oxide powder such as alumina as a dispersion stabilizer can be reduced. Without lowering the electrical properties of the sheet, it is also possible to suppress a decrease in electrical conductivity over time. The conductivity at 800 ° C. referred to here is an electric conductivity of 10 ⁻⁴ when the sintered body of the oxide or the composite oxide exposed to the 800 ° C. temperature atmosphere is measured by the DC four-terminal method. It means what is S / cm or more, and is electrical conductivity as an electronic conductivity, oxygen ion conductivity, and a mixed conductive material thereof. When the electrical conductivity is less than 10 ⁻⁴ S / cm, the electrical conductivity is too low as compared with the electrolyte to be used, and sufficient conductivity lowering prevention and the effect of suppressing deterioration with time are not exhibited. Preferably, it is 5 × 10 ⁻⁴ S / cm or more, more preferably 10 ⁻³ S / cm or more. Suitable materials having an oxygen ion conductivity of 10 ⁻⁴ S / cm or more include stabilized zirconia, yttrium oxide, gadolinium oxide in which at least one oxide selected from scandium oxide, yttrium oxide and ytterbium oxide is dissolved. Doped ceria in which at least one oxide selected from samarium oxide is dissolved, and stabilized bismuth oxide in which at least one oxide selected from yttrium oxide, niobium oxide and tungsten oxide is dissolved.

  In the case of the stabilized zirconia, stabilized zirconia in which 3 mol% to 15 mol% of at least one oxide selected from scandium oxide, yttrium oxide, and ytterbium oxide is dissolved is used.

In the case of the doped ceria, yttrium oxide, a solid solution of at least one oxide selected from gadolinium oxide and samarium oxide, the chemical formula _{Ce 1-x Ln x O 2} ± δ (Ln is Y, Gd, 1 is a kind of Sm, x is usually 0.05 ≦ x ≦ 0.4, and δ is oxygen excess or oxygen deficiency). x ≦ 3 yttria doped ceria (Ce _0.7 Y _0.3 O _{2 ± δ} ), samaria doped ceria (Ce _0.8 Sm _0.2 O _{2 ± δ} ), gadolinia doped ceria (Ce _0.8 Gd) _0.2 O _{2 ± δ} ) is particularly preferably used.

  In the case of the above-mentioned stabilized bismuth oxide, stabilized bismuth oxide in which 10 to 40 mol% of at least one oxide selected from yttrium oxide, niobium oxide and tungsten oxide is dissolved is used. In particular, bismuth oxide stabilized with 10 to 35 mol% in the case of yttrium oxide, 10 to 25 mol% in the case of niobium oxide, and 15 to 30 mol% in the case of tungsten oxide is preferably used.

  If the composition and composition ratio of the oxide nanoparticles are the same as the electrolyte powder, it is sintered in the electrolyte matrix and completely dissolved in the matrix, so the dispersion strengthening function does not work effectively and the strength characteristics are improved. Does not contribute, it is preferable to have a composition / composition ratio different from that of the electrolyte powder.

  In addition, the manufacturing method of these oxide nanoparticles is not specifically limited, The particle | grains manufactured by the well-known method and the commercially available nanoparticle can be used. Solid phase method using general media stirring mill or bead mill with bead media of less than 100μm, coprecipitation method, homogeneous precipitation method, compound precipitation method, metal alkoxide method, hydrothermal synthesis method, sol-gel method, spray pyrolysis method, etc. A liquid phase method, a flame method, a plasma method, a laser method, an electric furnace heating method, an electrostatic spray method, or the like is used as appropriate.

  Moreover, the average particle diameter of the electrolyte powder serving as the electrolyte matrix is preferably 0.2 to 1 μm for increasing the density of the electrolyte sheet itself and for closest packing with oxide nanoparticles. More preferably, it is 0.2-0.8 micrometer, More preferably, it is 0.25-0.7 micrometer. Furthermore, when the ratio (Df / Dn) of the electrolyte powder average particle diameter (Df) to the oxide nanoparticle average particle diameter (Dn) is 5 to 80, the closest packing can be achieved. It is preferable to select the particle diameter and the average particle diameter of the oxide nanoparticles so as to be within the above range. More preferably, Df / Dn is 8 to 60, and further preferably 10 to 50. Further, if the particle diameter exceeds 1 μm, closed pores are likely to be generated in the electrolyte sheet. Conversely, if the particle diameter is less than 0.2 μm, the specific surface area of the powder becomes large, so a large amount of binder is required for molding. There is a problem that the fired sheet is greatly warped and the flatness of the sheet is deteriorated.

  The average particle diameter of the electrolyte powder and the average particle diameter of the oxide nanoparticles defined in the present invention are values measured with a dynamic light scattering particle size distribution measuring apparatus (manufactured by Horiba, Ltd .: model LB550). This is because the average particle diameter measured from a photographic image of an electrolyte powder or oxide nanoparticles observed with a transmission electron microscope (TEM) or a field emission scanning electron microscope (FESEM) has a large fluctuation. Although it is insufficient to define the average particle diameter of the invention, in the dynamic light scattering particle size distribution measurement, the light irradiated from the semiconductor laser (650 nm / 5 mW) is condensed by a lens, and the focal position can be obtained. Only by approaching the inner wall of the cell container containing the measurement sample, the influence of multiple scattering is suppressed, the incident light angle to the cell container is optimized to eliminate the influence of stray light and reflected light, and the measurement particle diameter range is from 1 nm to 6000 nm This is because measurement can be performed with high reproducibility.

  Furthermore, it is preferable that raw material ceramic powder consists of said electrolyte powder 80-99.99 mass% and said oxide nanoparticle 0.01-20 mass%. In general, oxide nanoparticles usually have a large specific surface area, so they are often aggregated, and the aggregated nanoparticles are efficiently crushed and warped by the addition of high specific surface area nanoparticles. From the problem of sheet formability such as cracking and cracking, the oxide nanoparticles are dispersed almost uniformly in the electrolyte matrix by making the oxide nanoparticles 0.01 to 20% by mass in the raw material ceramic powder. The effect of the amount of binder added due to the increase in the specific surface area of the powder can be reduced, and an improvement in sheet strength characteristics is observed. When the content of the oxide nanoparticles is less than 0.01% by mass, the dispersion effect of the nanoparticles is insufficient and no improvement in strength characteristics is observed. Conversely, if the content exceeds 20% by mass, it will be difficult to uniformly disperse the nanoparticle oxide, but it will be dispersed in a partially aggregated state, and a large amount of binder will be required for sheet molding. This causes problems of warping and cracking. On the other hand, there is a problem that the strength characteristics are lowered as compared with the case where no nanoparticle oxide is contained. A more preferable content ratio is 90 to 99.95% by mass of the electrolyte powder and 0.05 to 10% by mass of the oxide nanoparticles, and more preferably 95 to 99.9% by mass of the electrolyte powder.

  As the composition of the electrolyte powder that serves as the electrolyte matrix of the solid oxide fuel cell of the present invention, a stabilized zirconia or lanthanum gallate system is selected. The stabilized zirconia powder is preferably stabilized zirconia in which 3 to 15 mol% of at least one oxide selected from scandium oxide, yttrium oxide, and ytterbium oxide is dissolved. The crystal structure may be tetragonal in the main body, cubic in the main body, or a mixed crystal of tetragonal and cubic crystals, but especially in the case of stabilized zirconia having a crystal structure mainly including the cubic system. 9 to 12 mol% scandia-stabilized zirconia, 8 to 10 mol% yttria-stabilized zirconia, and 10 to 13 mol% ytterbia-stabilized zirconia are recommended as particularly preferable.

In addition to the above stabilizer, alkaline earth metal oxides of MgO, CaO, SrO, BaO, and other rare earth element oxides such as 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 , Ho ₂ O ₃ , Er ₂ O ₃ , and other oxides such as Al ₂ O ₃ , Ga ₂ O ₃ , Bi ₂ O ₃ Is suitably selected, but the amount is suitably not more than 15 mol% in total with at least one oxide selected from scandium oxide, yttrium oxide, and ytterbium oxide. As a lanthanum gallate electrolyte, LaGaO ₃ perovskite has a basic structure, and lanthanum or gallium is partially replaced with strontium, calcium, barium, magnesium, indium, cobalt, iron, nickel, copper, or the like. _{1-X Sr X Ga 1-} Y Mg Y O 3-δ, La 1-X Sr X Ga 1-Y Mg Y Co Z O 3-δ, La 1-X Sr X Ga 1-Y Fe Y O 3- _δ , La _1-X Sr _X Ga _1-Y Ni _Y O _3-δ , (0 <X ≦ 0.2, 0 <Y ≦ 0.2, 0 <Z ≦ 0.1, δ is the amount of oxygen deficiency Is). Among them, La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ and La _0.9 Sr _0.1 Ga _0.8 Mg _0.115 Co _0.085 O _3-δ are high oxygen ions. Since it has electroconductivity, it is especially preferable.

  The method for producing an electrolyte sheet according to the present invention includes a green sheet forming step in which a slurry obtained through the following three milling steps is used to form a sheet by a doctor blade method, and then the obtained green sheet is predetermined. It consists of a firing step of firing after cutting into a shape. The core technology of the manufacturing method is pulverization of aggregates of oxide nanoparticles added to the electrolyte powder serving as the electrolyte matrix and uniform dispersion of the electrolyte powder serving as the electrolyte matrix and the crushed oxide nanoparticles. is there.

  Specifically, 0.01 to 20 parts by mass of oxide nanoparticles for pulverizing aggregated oxide nanoparticles, a step of milling a dispersant and a solvent (Milling I), and then an electrolyte matrix In order to uniformly disperse the oxide powder and the pulverized oxide nanoparticles, 80 to 99.99 parts by mass of the electrolyte powder is added to the oxide nanoparticle slurry obtained in the milling step I, and then milled. (Milling II) After adding a binder and a plasticizer to the mixed slurry of the electrolyte powder and oxide nanoparticles obtained in the milling step II, the oxide nanoparticles and the electrolyte powder are subjected to a milling step (Milling III). A uniformly dispersed slurry is prepared, and then the slurry is formed into a sheet to form an electrolyte green sheet. The green sheet is cut into a predetermined shape. Through a baking step of post-baking to form an electrolyte sheet.

  In the milling steps I to III, a known milling method such as a ball mill or a bead mill can be used. However, the aggregated nanoparticles are pulverized, and the oxide powder serving as the electrolyte matrix and the pulverized nanoparticle oxide are uniformly dispersed. In order to perform the mixing efficiently, milling by a slurry circulation type bead mill is preferable. As media used for these milling, zirconia balls of 2 to 20 mmφ, preferably 3 to 10 mmφ, and beads of zirconia of 30 to 1000 μm, preferably 50 to 500 μm are suitable. In addition, 0.01 to 20 parts by mass of oxide nanoparticles and 80 to 99.99 parts by mass of the electrolyte powder form a slurry raw material. This mixing ratio is based on the above-described reason.

  As a dispersant used in the milling step I, a nonionic surfactant is used in order to more efficiently disintegrate the aggregated nanoparticles, and ethanol having 2 to 4 carbon atoms, isopropanol, An alkyl alcohol such as n-butanol is used. This has the problem that the wettability of the oxide nanoparticles to the solvent becomes poor due to the surface tension of the solvent, making it difficult to form a slurry. However, the nonionic surfactant having an effect of reducing the surface tension and the number of carbon atoms are 2 This is because the use of ˜4 alkyl alcohol improves wettability and makes the aggregated nanoparticles more easily crushed. Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and polyoxyethylene higher alcohol ether; polyoxyalkylene alkyl ethers; polyoxyethylene distyrenated phenyl Polyoxyethylene derivatives such as ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate; polyoxyethylene sorbitan monolaurate, polyoxyethylene Sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene Sorbitan monooleate, polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan trioleate; glycerin fatty acid esters such as glycerol monooleate is preferably used.

  Moreover, the addition amount of a dispersing agent is 1-5 mass parts with respect to raw material ceramic powder, Preferably it is 1.5-3 mass parts in order to peptize and disperse | distribute oxide nanoparticles uniformly. If the amount is less than 1 part by mass, the effect of uniform peptization / dispersion of the oxide nanoparticles is not sufficient, and if the amount exceeds 5 parts by mass, the addition effect is the same as in the case of 5 parts by mass or less.

  Moreover, as a solvent used in the milling step I, in addition to the alkyl alcohol having 2 to 4 carbon atoms, alcohols such as 1-hexanol; ketones such as acetone and 2-butanone; pentane, hexane Aliphatic hydrocarbons such as heptane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and acetates such as methyl acetate, ethyl acetate, and butyl acetate are appropriately selected and used. These solvents can be used alone or in combination with an alkyl alcohol having 2 to 4 carbon atoms, and two or more kinds can be used by appropriately mixing them. These dispersants and solvents can be further added in the subsequent milling steps II and III, but the amount of these solvents used can be adjusted appropriately by taking into account the viscosity of the slurry at the time of forming the green sheet. In the case of molding into a sheet by the doctor blade method, the slurry viscosity is preferably adjusted to 1 to 10 Pa · s, more preferably 1 to 5 Pa · s.

Further, the specific surface area of the oxide nanoparticles used in the milling step I is preferably 10 m ² / g or more and 120 m ² / g or less. When the specific surface area is less than 10 m ² / g, the aggregation of the nanoparticles becomes excessively strong, so that the aggregation of the nanoparticle aggregates becomes difficult, the effect of suppressing the generation of closed pores is reduced, and the density is hardly increased. Moreover, since handling will become difficult when it exceeds 120 m < ² > / g, a large amount of binders will be needed, and as a result, sheet moldability will worsen. A more preferable specific surface area is 12 m ² / g or more and 100 m ² / g or less, and further preferably 15 m ² / g or more and 80 m ² / g or less. The specific surface area of the electrolyte powder used as the electrolyte matrix used in the milling step II is preferably 5 to ²⁰ m ² / g, more preferably 6 to 16 m ² / g.

  Furthermore, there is no particular limitation on the type of binder used in the milling step III, and conventionally known ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers. Examples thereof include celluloses such as maleic acid copolymers, vinyl butyral resins, vinyl acetal resins, vinyl formal resins, vinyl alcohol resins, waxes, and ethyl cellulose. Among these, methyl acrylate, ethyl acrylate, propyl are preferable from the viewpoints of uniform dispersion of the stabilized zirconia powder and nano-particle oxide, wettability to high specific surface area nanoparticles, sheet moldability, and thermal decomposability. Alkyl acrylates having an alkyl group of 10 or less carbon atoms such as acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, Alkyl methacrylate having an alkyl group having 20 or less carbon atoms, such as decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, etc. Rate; hydroxyalkyl acrylate or hydroxyalkyl methacrylate having a hydroxyalkyl group such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; aminoalkyl acrylate or amino such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate The number average molecular weight obtained by polymerizing or copolymerizing at least one of alkyl methacrylates; carboxyl group-containing monomers such as maleic acid half esters such as (meth) acrylic acid, maleic acid, and monoisopropylmalate; 20,000 to 200,000 (meth) acrylate, more preferably 50,000 to 100,000 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. Moreover, the preferable compounding quantity of this binder is 10 mass parts or more and 30 mass parts or less in conversion of solid content of a binder with respect to the total 100 mass parts of the electrolyte powder used as an electrolyte matrix, and the said oxide nanoparticle, More preferably, 13 The range of not less than 20 parts by mass and not more than 20 parts by mass is suitable, and when the amount of binder used is insufficient, the strength and flexibility of the molded product are insufficient, and conversely, if too much, it is difficult to adjust the viscosity of the slurry. In addition to this, the decomposition and release of the binder component during firing is large and intense, and it becomes difficult to obtain a homogeneous sintered body.

  Furthermore, in milling step III, phthalates such as dibutyl phthalate and dioctyl phthalate, and glycols such as propylene glycol and glycol ethers for imparting flexibility to the electrolyte green sheet produced in the subsequent sheet forming step A plasticizer such as a slag may be added, and an antifoaming agent or the like can be added as necessary. Next, in the step of forming a green sheet using the slurry prepared as described above, a doctor blade method, an extrusion molding method, a slurry coating method on an electrode support substrate, a screen printing method using a slurry adjusted to a high viscosity, etc. Although it can be adopted, the doctor blade method is preferable from the viewpoint of productivity. In the doctor blade method, the slurry obtained as described above is spread on a carrier film while adjusting the thickness with a doctor blade, formed into a sheet shape, dried, and the solvent is evaporated to dry the electrolyte green sheet. obtain. Subsequently, in the step of firing the green sheet, the green sheet may be cut and punched or the like so as to have a predetermined shape in consideration of the firing shrinkage rate, and then fired. For firing, plate-like or block-like porous ceramics are placed as a weight to place a green sheet of a predetermined shape on a shelf board or porous setter, and to prevent warpage and swell from occurring on the uppermost stage. The electrolyte sheet for the solid oxide fuel cell of the present invention is heated at 1200 to 1500 ° C., preferably about 1300 to 1450 ° C., more preferably 1350 to 1430 ° C. for about 1 to 5 hours. Get.

  In addition, the shape of the electrolyte sheet for a solid oxide fuel cell of the present invention is not particularly limited, and for an electrolyte support membrane cell, a disk-shaped sheet, or a donut-shaped sheet with a hole formed in the center, or other In addition to any polygonal shape, perforated polygonal shape or sheet shape such as a polygonal shape with a rounded corner, a cylindrical shape or a cylindrical / flat cylindrical shape with one side sealed, honeycomb shape, corrugated shape or dimple Even a three-dimensional shape such as a shape can be used effectively. In addition, it can be effectively used as a thin film electrolyte of an electrode support membrane type cell in a shape along the shape of the electrode support. As for the thickness of the electrolyte support membrane type cell in which the effect of the present invention is remarkably recognized, the thickness of the electrolyte sheet is preferably set to 0. 0 mm in order to suppress current loss as much as possible while satisfying the required strength as an electrolyte. It is good to be 05 mm or more, more preferably 0.08 mm or more, further preferably 0.1 mm or more, 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.25 mm or less. Moreover, as an electrolyte membrane for electrode support membrane type cells, the film thickness is 0.005 mm or more, more preferably 0.008 mm or more, still more preferably 0.01 mm or more, and 0.03 mm or less, more preferably 0.00. It is good to set it to 02 mm or less, more preferably 0.15 mm or less.

The size of the electrolyte of the present invention is not particularly limited, but in the case of an electrolyte supporting membrane type cell sheet, the perforated portion is also included due to the design of the fuel cell power generation system such as cost, uniform gas flow distribution, and uniform temperature distribution. The area is 50 cm ² or more, preferably 80 cm ² or more, 900 cm ² or less, preferably 600 cm ² or less.

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

(Example 1)
One part by weight of commercially available 20 mol% gadolinia doped ceria nanoparticles (Aldrich, average particle size: 37 nm, specific surface area: 42 m ² / g, hereinafter referred to as GDC20) was added to a nonionic surfactant (Kao: sorbitan). The mixture was stirred and uniformly mixed in isopropanol to which (fatty acid ester) was added. Subsequently, the mixed solution was put into a bead mill apparatus (trade name “SC mill”, model SC100, manufactured by Mitsui Mining Co., Ltd.) charged with 0.3 mmφ zirconia beads, and milled at an agitator rotational speed of 2400 rpm for 10 minutes ( Milling I). When the particle size distribution of the particles in the obtained milling liquid was measured using a dynamic light scattering type particle size distribution measuring device (manufactured by Horiba: model LB550), the average particle size was 31 nm, and the 90% by volume diameter was 190 nm. It was.

This milling solution was charged into a 100 L nylon pot ball mill apparatus charged with 5 mmφ zirconia balls, and further commercially available 10 mol% scandia 1 mol% ceria stabilized zirconia powder (Daiichi Rare Element Chemical Co., Ltd .: 99 parts by mass of a trade name “10Sc1CeSZ”, average particle size: 0.5 μm, specific surface area: 11 m ² / g, hereinafter referred to as 10Sc1CeSZ) was added and kneaded at 40 rpm for 16 hours (Milling II).

Next, methacrylic acid ester copolymer (2-ethylhexyl methacrylate; 95%, dimethylaminoethyl methacrylate; 4%, hydroxypropyl acrylate; 1% copolymer, average molecular weight with respect to 100 parts by mass of these raw ceramic powders : 80,000, glass transition temperature: −8 ° C.) Nylon pot with 18 parts by mass in terms of solid content and a mixed solvent of dibutyl phthalate and toluene / isopropyl alcohol (mass ratio: 3/2) as a plasticizer And kneaded at 60 rpm for 16 hours (Milling III) to prepare a nanoparticle-containing raw material slurry.
This slurry was transferred to a jacketed round bottom cylindrical vacuum degassing vessel equipped with a bowl-shaped stirrer and having a volume of 50 L. While rotating the stirrer at a speed of 30 rpm, the jacket temperature was reduced at 40 ° C. (30 to 160 Torr). ) The solution was concentrated and degassed to obtain a coating slurry having a viscosity of 2.5 Pa · s.

The obtained slurry for coating is transferred to a slurry dam of a coating apparatus, coated on a PET film by a doctor blade method, and a dryer (3 zones of 50 ° C., 80 ° C., 110 ° C.) following the coating part is placed. A green sheet having a thickness of 280 μm was obtained by passing the solvent at a speed of 0.2 m / min to evaporate and dry the solvent.
The obtained green sheet was cut into a strip of about 60 mm × 10 mm and a square of about 120 mm, degreased by sandwiching the upper and lower sides with a porous plate having a flat alumina content of 99.5%, and then fired at 1450 ° C. for 5 hours. As a result, a strip-shaped 10Sc1CeSZ sheet having a thickness of 250 μm and a thickness of 50 mm × 8 mm and a 10Sc1CeSZ sheet having a thickness of 250 μm and a square of 100 mm were obtained.

(Example 2)
Commercially available 3 mol% yttria stabilized zirconia powder (manufactured by Sumitomo Osaka Cement Chemical Co., Ltd .: trade name “OZC-3YC”, average particle size: 0.3 μm, specific surface area: 11 m ² / g, hereinafter referred to as 3YSZ) 10 parts by mass Was stirred in isopropanol to which a nonionic surfactant (manufactured by Kao: sorbitan fatty acid ester) was added, and mixed uniformly. Next, the mixed solution was milled at 2400 rpm for 10 minutes using a bead mill apparatus charged with 0.3 mmφ zirconia beads (Milling I). The obtained mixture was dried by spray drying, and the particle size distribution of the dried particles was measured using a dynamic light scattering particle size distribution measuring device (manufactured by Horiba: model LB550). The average particle size was 78 nm, The 90% by volume diameter was 350 nm. The specific surface area was 16 m ² / g.

This milling solution was charged into a 100 L nylon pot ball mill apparatus charged with 5 mmφ zirconia balls in the same manner as in Example 1, and further 8 mol% yttria stabilized zirconia powder (manufactured by Daiichi Rare Element Chemical Co., Ltd .: 90 parts by mass of a trade name “HSY-8.0”, average particle size: 0.3 μm, specific surface area: 8 m ² / g, hereinafter referred to as 8YSZ) was added and kneaded at 40 rpm for 16 hours (Milling II).

  Next, 17 parts by mass of the same binder as in Example 1 was charged into a nylon pot together with a mixed solvent of dibutyl phthalate and toluene / isopropyl alcohol (mass ratio: 3/2) as a plasticizer, and 16 parts at 60 rpm. It knead | mixed for a time (Milling III), and prepared the nanoparticle containing raw material slurry. This slurry was concentrated and defoamed in the same manner as in Example 1 to obtain a coating slurry having a viscosity of 2.0 Pa · s, and then a green sheet having a thickness of 280 μm was obtained in the same manner as in Example 1. . The obtained green sheet was cut, degreased and fired in the same manner as in Example 1 to obtain a strip-shaped 8YSZ sheet having a thickness of 250 μm and 50 mm × 8 mm and an 8YSZ sheet having a thickness of 250 μm and 100 mm square.

(Example 3)
20 mol% yttria-stabilized bismuth oxide was obtained by a known citric acid method. Specifically, ammonia water was added to a mixed solution of bismuth chloride and yttrium chloride blended so as to be 80 mol% bismuth oxide and 20 mol% yttrium oxide to form a coprecipitate. The coprecipitate is washed with water, dispersed in water, and citric acid is added while heating to 80 ° C. to produce a uniform and fine bismuth-yttrium complex oxide precursor citrate, which is then dried and citrated. After decomposition firing and decarbonation firing, firing was performed at 1000 ° C. to obtain 20 mol% yttria-stabilized bismuth oxide powder (average particle size: 2.3 μm, specific surface area: 19 m ² / g, hereinafter referred to as 20YSBi). After bead milling as in Example 1, isopropanol was evaporated by a rotary evaporator to obtain 20YSBi nanoparticles having an average particle size of 64 nm and a specific surface area of 24 m ² / g.

Moreover, 11 mol% ytterbia stabilized zirconia powder (average particle diameter: 0.8 μm, specific surface area: 7 m ² / g, hereinafter referred to as 11YbSZ) was obtained by a known citric acid method in the same manner as described above.

Isopropanol in isopropanol to which 5 parts by mass of 20 YSBi nanoparticles obtained above and a nonionic surfactant (manufactured by Kao: sorbitan fatty acid ester) were added to a 100 L nylon pot ball mill apparatus charged with 5 mmφ zirconia balls And after kneading at 60 rpm for 5 hours (Milling I),
Furthermore, 95 parts by mass of the 11YbSZ powder obtained above was added and kneaded at 40 rpm for 16 hours (Milling II).

Next, 17 parts by mass of the same binder as in Example 1 was charged into a nylon pot together with a mixed solvent of dibutyl phthalate and toluene / isopropyl alcohol (mass ratio: 3/2) as a plasticizer, and 16 parts at 60 rpm. It knead | mixed for time (Milling III), and prepared the nanoparticle containing raw material slurry.
This slurry was concentrated and defoamed in the same manner as in Example 1 to obtain a slurry for coating having a viscosity of 1.8 Pa · s, and then a green sheet having a thickness of 280 μm was obtained in the same manner as in Example 1. .

  The obtained green sheet was cut, degreased and fired in the same manner as in Example 1 to obtain a strip-shaped 11YbSZ sheet having a thickness of 250 μm and 50 mm × 8 mm, and a 11YbSZ sheet having a thickness of 250 μm and 100 mm square.

Example 4
0.5 parts by mass of 8 mol% yttria-stabilized zirconia nanoparticles (made by Aldrich, average particle size: 12 nm, specific surface area: 105 m ² / g, hereinafter referred to as 8YSZ) as oxide nanoparticles are used as the electrolyte powder. Except for using 99.5 parts by mass of commercially available 6 mol% scandia-stabilized zirconia powder (Daiichi Rare Element Co., Ltd., average particle size: 0.6 μm, specific surface area: 9 m ² / g, hereinafter referred to as 6ScSZ) In the same manner as in Example 1, a 6ScSZ sheet having a thickness of 150 μm was obtained.

(Example 5)
2 parts by mass of ceria nanoparticles commercially available as oxide nanoparticles (manufactured by C-I Kasei Co., Ltd., trade name “Nanotech”, average particle diameter: 15 nm, specific surface area: 55 m ² / g, hereinafter referred to as CeO ₂ ) as electrolyte powder 98 parts by mass of La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ powder (average particle size: 0.7 μm, specific surface area: 10 m ² / g, hereinafter referred to as LSGM) was used. Except for this, an LSGM sheet was obtained in the same manner as in Example 1. The LSGM powder was prepared by weighing a predetermined amount of each raw material (La ₂ O ₃ , SrCO ₃ , Ga ₂ O ₃ , MgO) and mixing in alcohol using a ball mill for 16 hours. The obtained slurry was dried and then calcined in the atmosphere at 1180 ° C. for 5 hours. Next, the powder was pulverized in alcohol again with a ball mill so that the average particle size became 0.7 μm, and then dried.

(Comparative Example 1)
A 10Sc1CeSZ sheet was obtained in exactly the same manner as in Example 1 except that GDC20 nanoparticles were not used.

(Evaluation Test Example 1)
The nanoparticle-added 10Sc1CeSZ sheet obtained in Example 1 and the nanoparticle-free 10Sc1CeSZ sheet obtained in Comparative Example 1 were measured for their electrical conductivity and three-point bending strength, and the effect of adding nanoparticles was observed. The electrical conductivity and the three-point bending strength were measured after exposure to 1000 hours, 3000 hours, and 5000 hours in an electric furnace maintained at 800 ° C. using a 10 Sc1CeSZ strip sheet as a test piece.

  The electrical conductivity is measured by winding the test piece exposed to the above high temperature at four intervals at 1 cm intervals with a 0.2 mm diameter platinum wire, applying a platinum paste, drying and fixing at 100 ° C., and a current / voltage terminal. With both ends of the test piece wound with platinum wire sandwiched between alumina plates so that the platinum wire is in close contact with the test piece, a constant load of 0.1 mA is applied to the outer two terminals with a load of about 500 g applied from above. A current was passed, and the voltage at the inner two terminals was measured by a DC multi-terminal method using a digital multimeter (manufactured by Advantest Corporation: trade name “TR6845 type”).

The durability stability of the conductivity was determined by the following formula from the initial conductivity and the change over time in the conductivity after a predetermined time.
Degradation rate of conductivity = [(initial conductivity−conductivity after holding for a predetermined time) / (initial conductivity)] × 100 (%)
The bending strength was measured in accordance with JIS R1601, each of 20 test pieces exposed at high temperature was measured at room temperature, and determined from the ratio of the initial bending strength and the bending strength after a predetermined time by the following formula.
Strength deterioration rate = [(initial strength−strength after holding for a predetermined time) / (initial strength)] × 100 (%)
Further, the Weibull coefficient was calculated from the results of 20 bending strengths.
Further, with respect to the 100 mm square electrolyte sheets of Example 1 and Comparative Example 1, after 10 different cross sections were polished with SiC sandpaper (# 1500), polishing scratches were not visible with a laser microscope, and 0.05 μm alumina was observed. A slurry dispersed in a nylon fiber buff is polished. Thereafter, an acceleration voltage IkW was applied to the sample surface-treated with an argon etching apparatus (JOEL, cross-section polisher, model: SM09010) using a field emission scanning electron microscope (FESEM, Hitachi, model: S-4800). Take a photo of the secondary electron image. The cross-sectional photograph shows a region of 4.6 μm in length and 6.3 μm in width magnified 20000 times, and the number of closed pores of 2 μm or less in this region was examined.
The results are shown in Table 1. Moreover, it measured similarly about the sheet | seat of Examples 2-5 which added the nanoparticle, and shows each result according to Table 1. FIG. It can be seen that even when the electrolyte powder is the same, by adding oxide nanoparticles, it is possible to suppress a decrease in three-point bending strength and a decrease in conductivity (see Example 1 and Comparative Example 1).

  The present invention is a method for producing a solid oxide electrolyte sheet, and the sheet obtained according to the present invention is a solid electrolyte that has excellent high-temperature strength sustainability and can be used for a long time at a high temperature. It can be used, and is particularly suitable for use as an electrolyte for fuel cells.

Claims (13)

A solid oxide fuel cell, characterized in that the raw material ceramic powder comprises an electrolyte powder having an average particle size of 0.2 to 1 μm and oxide nanoparticles (except alumina nanoparticles) having an average particle size of 10 to 100 nm. Electrolyte sheet for use. 2. The electrolyte sheet for a solid oxide fuel cell according to claim 1, wherein the raw material ceramic powder is 80 to 99.99% by mass of the electrolyte powder and 0.01 to 20% by mass of the oxide nanoparticles. . 3. The electrolyte sheet for a solid oxide fuel cell according to claim 1, wherein the conductivity of the oxide nanoparticles at 800 ° C. is 10 ⁻⁴ S / cm or more. The electrolyte powder is selected from stabilized zirconia and / or lanthanum gallate-based perovskite oxide in which 3 to 15 mol% of at least one oxide selected from scandium oxide, yttrium oxide and ytterbium oxide is dissolved. The electrolyte sheet for a solid oxide fuel cell according to claim 1, wherein the electrolyte sheet is at least one kind. The oxide nanoparticles are at least selected from stabilized zirconia, ceria and yttrium oxide, gadolinium oxide, and samarium oxide in which at least one oxide selected from zirconia and scandium oxide, yttrium oxide, and ytterbium oxide is dissolved. 2. A stabilized bismuth oxide in which at least one oxide selected from dope ceria, bismuth oxide, yttrium oxide, niobium oxide, and tungsten oxide, in which one oxide is dissolved, is dissolved. -4 Electrolyte sheet for solid oxide fuel cell. Milling step for preparing slurry containing raw material ceramic powder, binder, solvent and dispersant, step for forming green sheet by forming the slurry into a sheet, and firing step for firing the green sheet after cutting into a predetermined shape In the method for producing a solid electrolyte sheet, the raw material ceramic powder comprises an electrolyte powder having an average particle size of 0.2 to 1 μm and oxide nanoparticles having an average particle size of 10 to 100 nm (excluding alumina nanoparticles). A method for producing an electrolyte sheet for a solid oxide fuel cell. The manufacturing method according to claim 6, wherein the raw ceramic powder is composed of 80 to 99.99 mass% of the electrolyte powder and 0.01 to 20 mass% of the oxide nanoparticles. The manufacturing method according to claim 7, wherein the oxide nanoparticles have a conductivity at 800 ° C. of 10 ⁻⁴ S / cm or more. The electrolyte powder is selected from stabilized zirconia and / or lanthanum gallate-based perovskite oxide in which 3 to 15 mol% of at least one oxide selected from scandium oxide, yttrium oxide and ytterbium oxide is dissolved. The production method according to claim 7 or 8, wherein at least one kind is used. The oxide nanoparticles are at least selected from stabilized zirconia, ceria and yttrium oxide, gadolinium oxide, and samarium oxide in which at least one oxide selected from zirconia and scandium oxide, yttrium oxide, and ytterbium oxide is dissolved. 10. A stabilized bismuth oxide in which at least one oxide selected from dope ceria, bismuth oxide, yttrium oxide, niobium oxide, and tungsten oxide, in which one oxide is dissolved, is a solid solution. Production method. In the milling step, 0.01 to 20 parts by mass of the oxide nanoparticles are dispersed in a first step (milling I) for milling the solvent, and the electrolyte powder is added to the slurry obtained in the first step in an amount of 80 to 99. It is characterized by comprising a second step (Milling II) for further milling after adding 99 parts by mass, and then a third step (Milling III) for further milling after adding a binder and a plasticizer to the slurry obtained in the second step. The manufacturing method according to claim 6. The manufacturing method according to claim 6, wherein the dispersant is a nonionic surfactant, and the solvent contains an alkyl alcohol having 2 to 4 carbon atoms. A solid oxide fuel cell comprising the electrolyte sheet according to claim 1.