JP2016072037A - Method for manufacturing single cell for solid oxide fuel battery, cathode for solid oxide fuel battery, and single cell for solid oxide fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single cell for a solid oxide fuel battery, which is high in performance and reliability and in which defects caused in a cathode in forming the cathode are decreased, in a further simple and convenient manner.SOLUTION: A method for manufacturing a single cell 1 for a solid oxide fuel battery comprises: (I) the step of preparing a cathode paste including cathode powder consisting of a cathode material, in which the difference between the cathode material and an electrolyte material of an electrolyte layer 13 in average linear thermal expansion coefficient at a temperature of 100-1000°C is 8.0×10/K or more; and (II) the step of forming a cathode 12 by applying the cathode paste to the electrolyte layer 13 and sintering the applied cathode paste. The cathode powder includes a mixture of cathode powder A and cathode powder B differing from each other in average particle diameter. The ratio (P/P) of the average particle diameter(P) of the cathode powder B to the average particle diameter(P) of the cathode powder A is 1.5-30. In the cathode powder, the content of the cathode powder A is 5-90 mass%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a single cell for a solid oxide fuel cell, a cathode for a solid oxide fuel cell, and a single cell for a solid oxide fuel cell.

  In recent years, fuel cells have attracted attention as clean energy sources. Among the fuel cells, solid oxide fuel cells (hereinafter referred to as “SOFC”) that use solid ceramics as the electrolyte can utilize exhaust heat because of their high operating temperature, and are more efficient and power efficient. It is expected to be used in a wide range of fields from household power sources to large-scale power generation.

  The SOFC has a structure in which an electrolyte layer made of ceramic is disposed between a cathode (air electrode) and an anode (fuel electrode) as a basic structure. For example, in a flat SOFC, a single cell is formed by stacking a cathode, an electrolyte layer, and an anode, and a high output is obtained by stacking a plurality of the single cells with an interconnector interposed therebetween.

  In general, a cathode is manufactured by forming a green layer using a paste for forming a cathode on an electrolyte layer or a barrier layer disposed between the electrolyte layer and the cathode, and firing the green layer. However, when such a method is used, there is a problem that the cathode is cracked due to a difference in thermal expansion coefficient between the cathode material and the electrolyte layer material, or the cathode is peeled off from an adjacent layer such as the electrolyte layer. Occurs. In order to realize a high-performance SOFC, the adhesion between the electrode and the layer adjacent to it is important. Therefore, when separation occurs between the cathode and the layer adjacent to the cathode, the performance of the SOFC is degraded. Therefore, conventionally, a material having a thermal expansion coefficient comparable to that of the material of the electrolyte layer needs to be used for the cathode, and the selection range of the material has been narrowed.

  Therefore, Patent Document 1 discloses a coarse powder mainly composed of a conductive oxide that has been pre-processed and has a reduced shrinkage ratio during firing in order to prevent the above-described defects that occur during cathode formation, A method of forming a cathode using a mixture containing a fine powder mainly composed of a conductive oxide having a shrinkage ratio larger than the coarse powder is proposed.

Japanese Patent No. 5398894

For the cathode, a material having electron conductivity is used. In recent years, perovskite oxides such as (La, Sr) CoO ₃ (LSC) having ion conductivity in addition to electron conductivity are also used as the cathode material. It is like that. According to the cathode material having both electron conductivity and ion conductivity, there is no need to separately add an electrolyte material or the like for imparting ion conductivity, so that the entire surface of the cathode material can be a reaction field. As a result, a high output SOFC can be realized.

  However, such a cathode material has a very large difference in thermal expansion coefficient from the material used for the SOFC electrolyte layer. On the other hand, in the conventional method proposed in Patent Document 1, no consideration is given to preventing defects generated in the cathode when the difference in thermal expansion coefficient between the cathode and the electrolyte layer is very large. . Moreover, in the method proposed in Patent Document 1, not only the particle diameter but also two kinds of conductive oxides having different shrinkage ratios during firing must be prepared, and the procedure for forming the cathode is complicated. .

  Therefore, the present invention can reduce defects such as cracks and delamination generated in the cathode when forming the cathode, taking into consideration the case where the difference in thermal expansion coefficient between the material of the cathode and the electrolyte layer is large. An object of the present invention is to provide a method for producing a single cell for SOFC, which can more easily provide a single cell for SOFC having power generation performance (for example, high cell voltage and low ASR (resistance value per unit area)). And Furthermore, the present invention reduces defects such as cracks and delamination that occur in the cathode even when the difference in thermal expansion coefficient between the cathode and the electrolyte layer is large, and further improves power generation performance (for example, high cell voltage and low Another object of the present invention is to provide a SOFC cathode and a single cell for SOFC that can realize ASR).

The present invention is a method of manufacturing a single cell for SOFC comprising a cathode, an anode, and an electrolyte layer disposed between the cathode and the anode,
(I) To form a cathode including a cathode powder made of a cathode material having a difference in average linear thermal expansion coefficient at 100 to 1000 ° C. from the electrolyte material of the electrolyte layer of 8.0 × 10 ⁻⁶ / K or more. Producing a cathode paste of
(II) applying the cathode paste onto the electrolyte layer and baking it to form a cathode;
Including
The cathode powder is a mixture containing cathode powder A and cathode powder B having different average particle sizes,
In the cathode powder, the ratio (P _B50 / P _A50 ) of the average particle diameter (P _B50 ) of the cathode powder B to the average particle diameter (P _A50 ) of the cathode powder A is 1.5 or more and 30 or less. The ratio of the cathode powder A is 5% by mass or more and 90% by mass or less.
A method of manufacturing a single cell for SOFC is provided.

The present invention also provides a cathode for SOFC,
10% particle diameter (D10) and 90% particle diameter (D90) in the cumulative particle size distribution based on the number of particles constituting the cathode satisfy the relationship of 2.45 ≦ D90 / D10 ≦ 10.00.
A cathode for SOFC is provided.

The present invention also provides:
A single cell for SOFC comprising an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode,
The unit length of the interface between the cathode and the adjacent layer adjacent to the cathode when the cross section at any five locations excluding 1 mm from the peripheral edge of the cathode is observed with an electron microscope over 200 μm. There are 7 or less exfoliation points existing in 1 mm, and the number of cracks in the cathode is 13 or less,
The resistance value per unit area (ASR) at 750 ° C. is 0.4 Ω · cm ² or less.
A single cell for SOFC is provided. However, ASR is a value calculated | required by the following formula | equation.
ASR = (open circuit voltage−cell voltage) / current density

  According to the method for manufacturing a single cell for SOFC of the present invention, even when the difference in thermal expansion coefficient between the material of the cathode and the electrolyte layer is large, defects such as cracks and delamination generated in the cathode during the formation of the cathode are reduced. In addition, a single cell for SOFC having further excellent power generation performance (for example, high cell voltage and low ASR) can be provided more easily. In addition, according to the SOFC cathode and the SOFC single cell of the present invention, defects such as cracks and delamination generated in the cathode are reduced even when the difference in thermal expansion coefficient between the cathode and the electrolyte layer is large. It is possible to provide a SOFC cathode and a SOFC single cell capable of realizing power generation performance (for example, high cell voltage and low ASR).

It is sectional drawing which shows the single cell for SOFC manufactured by one Embodiment of the manufacturing method of this invention. It is a figure which shows the example of the crack of a cathode, and peeling confirmed by the Example and the comparative example using the electron micrograph.

  The embodiment of the method for producing a single cell for SOFC of the present invention will be specifically described.

  The manufacturing method of the single cell for SOFC of this embodiment is a method of manufacturing the single cell for SOFC provided with the cathode, the anode, and the electrolyte layer arrange | positioned between the said cathode and the said anode. In addition, the manufacturing method of this embodiment is applicable to the single cell for various types of SOFC. For example, the manufacturing method of the present embodiment can be applied to manufacture of an electrolyte support cell (ESC) and an anode support cell (ASC).

The manufacturing method of this embodiment is
(I) To form a cathode including a cathode powder made of a cathode material having a difference in average linear thermal expansion coefficient at 100 to 1000 ° C. from the electrolyte material of the electrolyte layer of 8.0 × 10 ⁻⁶ / K or more. Producing a cathode paste of
(II) applying the cathode paste onto the electrolyte layer and baking it to form a cathode;
including. The cathode powder is a mixture including cathode powder A and cathode powder B having different average particle sizes, and the average particle size (P _B50 ) of the cathode powder B with respect to the average particle size (P _A50 ) of the cathode powder A. The ratio (P _B50 / P _A50 ) is 1.5 or more and 30 or less, and in the cathode powder, the ratio of the cathode powder A is 5 mass% or more and 90 mass% or less. In addition, the average particle diameter in this specification is a median diameter obtained from a volume-based cumulative particle size distribution, that is, a particle diameter (D50) corresponding to a volume accumulation of 50%. Here, the particle diameter of the powder specified in this specification is a particle diameter measured based on a laser diffraction scattering method.

  In the step (II), the cathode paste may be applied directly to the surface of the electrolyte layer, or may be applied to another layer laminated on the surface of the electrolyte layer, for example, the surface of the barrier layer. .

  In the present embodiment, a case where the SOFC single cell is an anode-supported cell will be described as an example. FIG. 1 shows a cross-sectional view of the anode-supported cell of this embodiment. The anode-supported cell 1 according to the present embodiment includes an anode 11, a cathode 12, and an electrolyte layer 13 disposed between the anode 11 and the cathode 12. A barrier layer 14 is further provided between the electrolyte layer 13 and the cathode 12. In addition, the barrier layer 14 should just be provided as needed, and the barrier layer 14 may not be provided. That is, in the anode supported cell 1 shown in FIG. 1, the barrier layer 14 is an adjacent layer adjacent to the cathode 12, and in the case where the barrier layer 14 is not provided in the anode supported cell 1, the electrolyte layer 13 is formed. It becomes an adjacent layer adjacent to the cathode 12.

  The anode 11 is formed by an anode support substrate 111 and an anode layer 112 disposed on the surface of the anode support substrate 111 on the electrolyte layer 13 side. In addition, when the anode support substrate 111 itself can sufficiently function as an anode electrode, the anode layer 112 may not be provided. The electrolyte layer 13, the barrier layer 14, and the cathode 12 are supported by the anode support substrate 111.

  An example of a method for manufacturing the anode-supported cell 1 includes a step of manufacturing a multilayer fired body including the anode 11, the electrolyte layer 13, and the barrier layer 14 and having a predetermined shape, and a multilayer fired body having a predetermined shape. And a step of producing the cathode 12 on the surface opposite to the anode 11.

The multilayer fired body
(1) On the green sheet for the anode support substrate 111, the green layer for the anode layer 112 (not required in the case where the anode layer 112 is not provided), the green layer for the electrolyte layer 13, and the barrier layer 14 A green layer (unnecessary in the case of a configuration not provided with the barrier layer 14) and a laminate in which the green layers are sequentially stacked, and then firing these all together,
Or
(2) A green sheet for the anode support substrate 111 is baked to produce the anode support substrate 111, and a green layer for the anode layer 112 (not necessary in the case of the configuration without the anode layer 112) thereon, and an electrolyte layer A green layer for 13 and a green layer for the barrier layer 14 (unnecessary in the case where the barrier layer 14 is not provided) are sequentially stacked and then fired.
Can be used. Here, the method for producing a multilayer fired body will be described by taking the method (1) as an example.

  First, a green sheet for the anode support substrate 111 is prepared. The green sheet for the anode support substrate 111 is a slurry obtained by mixing an anode material for SOFC, which is a raw material powder, a pore forming agent, a binder and a solvent, and further adding a dispersant, a plasticizer and the like as necessary. It is obtained by forming this slurry into a sheet having a predetermined thickness by any method such as a doctor blade method, a calender roll method, an extrusion method, etc., and drying this to evaporate and remove the solvent. .

The anode material for SOFC contains a conductive component for imparting conductivity and a ceramic material as a skeleton component. The conductive component is a metal such as nickel, cobalt, iron, platinum, palladium, ruthenium; a metal oxide that changes to a conductive metal in a reducing atmosphere during fuel cell operation, such as nickel oxide, cobalt oxide, or iron oxide; or Examples thereof include composite metal oxides such as nickel ferrite and cobalt ferrite containing two or more of these oxides. These may be used alone or in combination of two or more as necessary. Among these, metallic nickel, metallic cobalt, metallic iron, or oxides thereof are preferable. As the skeletal component, zirconia, alumina, magnesia, titania, aluminum nitride, mullite or the like is used alone or in combination. Among these, stabilized zirconia is the most versatile. Examples of the stabilized zirconia include zirconia, oxides of alkaline earth metals such as MgO, CaO, SrO, and BaO; Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ Oxides of rare earth elements such as 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 ; One in which at least one oxide selected from Sc ₂ O ₃ ; Bi ₂ O ₃ ; and In ₂ O ₃ is dissolved, or further, alumina, titania, Ta ₂ O as a dispersion strengthening agent. Dispersion strengthened zirconia to which ₅ and Nb ₂ O ₅ are added is exemplified as a preferable example. Further, as a skeleton component, CeO ₂ or Bi ₂ O ₃ is added to CaO, SrO, BaO, Y ₂ O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Nb ₂ O ₃ , Sm ₂ O _3. Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dr ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , PbO, WO ₃ , MoO ₃ , V ₂ O ₅ , Ta _A ceria-based or bismuth-based ceramic added with at least one selected from ₂ O ₅ and Nb ₂ O ₅ can also be used. A gallate ceramic such as LaGaO ₃ can also be used. These may be used alone or in combination of two or more. Among these, as the skeleton component, stabilized zirconia, ceria-based ceramics, and lanthanum gallate are preferable, stabilized zirconia is more preferable, and particularly preferable is zirconia stabilized with 2.5 to 12 mol% yttria, 2 Stabilized with 5-12 mol% ytterbia stabilized zirconia, 3-15 mol% scandia stabilized zirconia, 8-12 mol% scandia and 0.5-5 mol% ceria. Zirconia.

  The pore-forming agent, binder, solvent, dispersant, plasticizer, and the like used for the production of the green sheet for the anode support substrate 111 are the pore-forming agent, binder, It can be suitably selected from solvents, dispersants, plasticizers and the like.

  The thickness of the anode support substrate 111 is not particularly limited, but is preferably, for example, 100 μm or more, more preferably 120 μm or more, and further preferably 150 μm or more. The thickness of the anode support substrate 111 is preferably 3 mm or less, more preferably 2 mm or less, still more preferably 1 mm or less, and particularly preferably 500 μm or less. When the thickness of the anode support substrate 111 is within the above range, the mechanical strength and gas permeability of the anode support substrate 111 are easily balanced and balanced. Therefore, the green sheet for the anode support substrate 111 is preferably formed so that the thickness of the anode support substrate 111 is within the above range after firing.

  A green layer for the anode layer 112 is formed on the green sheet for the anode support substrate 111 using the paste for the anode layer 112. The paste for the anode layer 112 is prepared by mixing the anode material for SOFC, which is a raw material powder, a pore forming agent, a binder and a solvent, and further adding a dispersant, a plasticizer and the like as necessary. Is done. This paste is applied onto a green sheet for the anode support substrate 111 by using a method such as screen printing, and dried to form a green layer for the anode layer 112. As the anode material for SOFC used for forming the green layer for the anode layer 112, the materials exemplified above as the anode material for SOFC that can be used for producing the green sheet of the anode support substrate 111 can be used. is there. Further, the pore-forming agent, binder, solvent, dispersant, plasticizer, etc. are from among the pore-forming agent, binder, solvent, dispersant, plasticizer, etc. known in the SOFC anode layer manufacturing method. It can be selected as appropriate.

  Although the thickness of the anode layer 112 is not specifically limited, For example, 5 micrometers or more are preferable, 7 micrometers or more are more preferable, and 10 micrometers or more are further more preferable. The thickness of the anode layer 112 is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. When the thickness of the anode layer 112 is within the above range, the electrode reaction is efficiently performed, and the power generation performance is better when the anode-supported cell is formed. Therefore, the green layer for the anode layer 112 is preferably formed so that the thickness of the anode layer 112 is within the above range after firing.

  A green layer for the electrolyte layer 13 is formed on the green layer for the anode layer 112 by using the paste for the electrolyte layer 13. The paste for the electrolyte layer 13 is prepared by mixing at least a ceramic powder as a ceramic material and a solvent.

  As the ceramic powder used for the paste for the electrolyte layer 13, those known as the material for the SOFC electrolyte layer can be used. For example, zirconia stabilized with yttria, ceria, scandia, ytterbia, etc .; ceria doped with yttria, samaria, gadolinia, etc .; A lanthanum gallate perovskite structure oxide substituted with aluminum, indium, cobalt, iron, nickel, copper, or the like can be used. These may be used alone or in combination of two or more. Among these, zirconia stabilized with yttria, scandia, ytterbia and the like is preferable.

  Particularly preferred as a ceramic material is zirconia stabilized with 2.5-12 mol% yttria, zirconia stabilized with 2.5-12 mol% ytterbia, stable with 3-15 mol% scandia. Zirconia stabilized with 8-12 mol% scandia and 0.5-5 mol% ceria. A material obtained by adding alumina, silica, titania or the like as a sintering aid or dispersion strengthening agent to these stabilized zirconia can also be suitably used.

  The solvent used in the paste for the electrolyte layer 13 is not particularly limited, and can be appropriately selected from solvents known in the method for producing an SOFC electrolyte layer.

  Although the thickness of the electrolyte layer 13 is not specifically limited, For example, 3 micrometers or more are preferable, 4 micrometers or more are more preferable, and 5 micrometers or more are further more preferable. Further, the thickness of the electrolyte layer 13 is preferably 50 μm or less, more preferably 30 μm or less, and further preferably 20 μm or less. When the thickness of the electrolyte layer 13 is within the above range, when an anode-supported cell is used, the internal resistance can be reduced while preventing gas cross-leakage, resulting in better power generation performance. Therefore, the green layer for the electrolyte layer 13 is preferably formed so that the thickness of the electrolyte layer 13 is within the above range.

  In addition to the ceramic powder and the solvent, a binder, a dispersant, a plasticizer, a surfactant, an antifoaming agent, and the like may be added to the paste for the electrolyte layer 13. The binder, the dispersant, and the plasticizer are known in the manufacturing method of the SOFC electrolyte layer according to the material of the electrolyte layer 13 to be formed, and the binder, dispersant, plasticizer, surfactant, antifoaming agent, etc. Can be selected as appropriate.

  A green layer for the barrier layer 14 is formed on the green layer for the electrolyte layer 13. Similarly to the anode layer 112 and the electrolyte layer 13, the green layer for the barrier layer 14 is prepared by preparing a paste containing the raw material powder constituting the barrier layer 14, and applying the paste onto the green layer for the electrolyte layer 13, followed by drying. Can be formed. The thickness of the barrier layer 14 is preferably 20 μm or less. If the thickness is 20 μm or less, defects such as cracks and delamination generated in the cathode 12 when the cathode is formed can be further reduced even when the difference in thermal expansion coefficient between the cathode 12 and the electrolyte layer 13 is large. The thickness of the barrier layer 14 is more preferably 10 μm or less, further preferably 7 μm or less, and particularly preferably 5 μm or less. Moreover, since the high effect which accelerates | stimulates electric power generation can be anticipated, suppressing the production | generation of the insulating material which arises between the electrolyte layer 13 and the cathode 12 in the high temperature atmosphere at the time of cell preparation or electric power generation, thickness of the barrier layer 14 is anticipated. Although not particularly limited, for example, 0.1 μm or more is preferable, 0.2 μm or more is more preferable, and 0.5 μm or more is more preferable. For the barrier layer 14, a material having oxide ion conductivity is generally used, and for example, ceria doped with an oxide of rare earth elements such as Gd, Sm, and Y is used.

The material constituting the barrier layer 14 preferably has a difference in average linear thermal expansion coefficient at 100 to 1000 ° C. from the electrolyte material of the electrolyte layer 13 of 4.0 × 10 ⁻⁶ / K or less. More preferably, it is 0 × 10 ⁻⁶ / K or less. Further, as a material constituting the barrier layer 14, the difference in average linear thermal expansion coefficient at 100 to 1000 ° C. with respect to the cathode material is preferably 9.0 × 10 ⁻⁶ / K or less, and 8.0 × 10 ⁻ More preferably, it is ⁶ / K or less.

  A laminate formed by sequentially stacking a green layer for the anode layer 112, a green layer for the electrolyte layer 13, and a green layer for the barrier layer 14 on the green sheet for the anode support substrate 111. , Fired together. The firing temperature of the laminate is not particularly limited, but is preferably 1100 ° C. or higher, more preferably 1200 ° C. or higher, and further preferably 1250 ° C. or higher. The firing temperature is preferably 1500 ° C. or lower, more preferably 1400 ° C. or lower, and further preferably 1350 ° C. or lower. The firing time during firing is not particularly limited, but is preferably 0.1 hours or longer, more preferably 0.5 hours or longer, and even more preferably 1 hour or longer. The firing time is preferably 10 hours or less, more preferably 7 hours or less, and even more preferably 5 hours or less.

  A multilayer fired body is obtained by the method as described above. A method for obtaining a multilayer fired body having a predetermined shape is not particularly limited, but in consideration of shrinkage after firing, the anode layer 112 is formed on the green sheet for the anode support substrate 111 so as to have a desired shape after firing. The laminate formed by sequentially stacking the green layer for the electrolyte, the green layer for the electrolyte layer 13, and the green layer for the barrier layer 14 may be cut and / or punched and then fired. The multilayer fired body obtained by firing the laminate may be cut using a laser or a ceramic cutter.

  Next, in the multilayer fired body having a predetermined shape, the cathode 12 is formed on the surface opposite to the anode 11. The cathode 12 is produced by forming a green layer for the cathode 12 using the paste for the cathode 12 and firing the green layer.

First, a cathode 12 paste for forming the cathode 12 is prepared. The cathode 12 paste includes a cathode powder made of a cathode material. As the cathode material, the difference in average linear thermal expansion coefficient at 100 to 1000 ° C. with respect to the electrolyte material of the electrolyte layer 13, that is, the material of the ceramic powder used for the paste for the electrolyte layer 13 is 8.0 × 10 ⁻⁶ / K or more. Some material is used. As the cathode material, a perovskite oxide that is excellent in electron conductivity, ion conductivity, and stable even in an oxidizing atmosphere is preferably used. Specifically, La _0.8 Sr _0.2 MnO ₃ , La _0.6 Sr _0.4 CoO ₃ , La _0.6 Sr _0.4 FeO ₃ , La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O ₃ and La _0.6 Sr _0.4 Co _0.8 Mn _0.2 O _3, etc. Lanthanum strontium manganite, lanthanum strontium cobaltite, lanthanum strontium ferrite, and lanthanum strontium cobalt ferrite and lanthanum strontium cobalt in which part of cobalt in lanthanum strontium cobaltite is replaced with iron, manganese, etc. Manganite or the like is preferably used. Among these, (La, Sr) CoO ₃ (LSC), (La, Sr) Co, FeO ₃ (LSF), (La, Sr) (Co, Fe) O having both high electronic conductivity and ionic conductivity. A material such as ₃ is a more preferable material. Further, in order to alleviate the difference in average linear expansion coefficient between the electrolyte and the cathode material while imparting ion conductivity to the cathode 12, oxides of rare earth metals such as Sc, Y and Ce and alkaline earth metal oxides Stabilized zirconia containing 2.5 to 15 mol% as a stabilizer and ceria doped with a rare earth element oxide or the like can be appropriately mixed.

The cathode powder is a mixture containing cathode powder A and cathode powder B having different average particle sizes. The ratio (P _B50 / P _A50 ) of the average particle size (P _B50 ) of the cathode powder B to the average particle size (P _A50 ) of the cathode powder A is 1.5 or more and 30 or less. By using a mixture of cathode powder A and cathode powder B satisfying P _B50 / P _A50 within this range, the difference in thermal expansion coefficient (average linear thermal expansion coefficient) between the cathode material and the electrolyte material of the electrolyte layer 13 is 8 Even when it is as large as 0.0 × 10 ⁻⁶ / K or more, shrinkage during sintering of the green layer of the cathode 12 is suppressed, so cracks generated in the cathode 12 and peeling from the adjacent layer (here, the barrier layer 14). Can be reduced. Further, according to the mixture of the cathode powder A and the cathode powder B, the surface area of the formed cathode can be increased as compared with the cathode material composed only of coarse particles, so that more excellent power generation performance can be obtained. realizable. Preferably, P _B50 / P _A50 is 2 or more and 25 or less, more preferably 3 or more and 20 or less.

  Cathode powder A and cathode powder B are preferably pre-fired fired powders. Since the fired powder has been fired once, the progress of the sintering becomes slow, and as a result, there is an effect that it is easy to obtain a porous structure after the sintering. Thereby, the cathode 12 with a larger surface area can be obtained. Furthermore, when using a baked powder, the crystal structure (for example, it is a single phase consisting of perovskite) can be confirmed by X-ray diffraction measurement, and the confirmed powder can be used. Therefore, since there is no deviation in composition ratio and no impurities are contained, the original ionic conductivity and electronic conductivity of the material can be easily exhibited. As a result, a higher output SOFC single cell can be realized. It becomes.

  In the cathode powder, the ratio of the cathode powder A is 5% by mass or more and 90% by mass or less. By setting the cathode powder A to 5% by mass or more, high power generation performance can be realized by increasing the reaction field due to the increase in the surface area of the cathode powder. Preferably, the cathode powder A is 7% by mass or more, more preferably 10% by mass or more. Moreover, since the shrinkage | contraction at the time of sintering is suppressed by making cathode powder A into 90 mass% or less, the defect which generate | occur | produces in the cathode 12 can be reduced. Preferably, the cathode powder A is 70% by mass or less, and more preferably 50% by mass or less.

The average particle size of the cathode powder A and the cathode powder B is not particularly limited as long as the above relationship is satisfied. However, in consideration of high power generation performance and more reliable reduction of defects generated in the cathode 12, the average particle diameter (P _A50 ) of the cathode powder A is preferably 0.05 to 0.75 μm. More preferably, it is .10 to 0.70 μm, and particularly preferably 0.15 to 0.60 μm. The average particle size (P _B50 ) of the cathode powder B is preferably 0.80 to 5.0 μm, more preferably 0.85 to 4.0 μm, and 0.90 to 3.0 μm. It is particularly preferred.

  The paste for the cathode 12 is prepared by uniformly mixing together the raw material powder (the cathode powder) constituting the cathode 12, the binder and the solvent, and if necessary, the dispersant and the plasticizer. The binder, the solvent, the dispersant, the plasticizer, and the like can be appropriately selected from binders, solvents, dispersants, plasticizers, and the like known in the SOFC cathode manufacturing method. The prepared paste is applied onto the multilayer fired body by screen printing or the like and dried to form a green layer for the cathode 12. By baking this, the cathode 12 is produced. Although a calcination temperature is not specifically limited, 800 degreeC or more is preferable, 850 degreeC or more is more preferable, and 950 degreeC or more is further more preferable. The firing temperature is preferably 1300 ° C. or lower, more preferably 1250 ° C. or lower, and further preferably 1200 ° C. or lower. The firing time during firing is not particularly limited, but is preferably 0.1 hours or longer, more preferably 0.5 hours or longer, and even more preferably 1 hour or longer. The firing time is preferably 10 hours or less, more preferably 7 hours or less, and even more preferably 5 hours or less.

  The 10% particle size (d10) and 90% particle size (d90) in the volume-based cumulative particle size distribution of the cathode powder (mixed powder of cathode powder A and cathode powder B) in the cathode 12 paste are d90 / d10 ≧ 2. .3 and preferably d90 / d10 ≧ 2.5. By satisfying such a particle size distribution of the cathode powder in the paste, it is possible to more reliably produce a cathode capable of reducing cracks and peeling and realizing high power generation performance. As a result, the cathode powder has high performance and high reliability. Realization of SOFC becomes possible.

  Although the thickness of the cathode 12 is not specifically limited, For example, 5.0 micrometers or more are preferable, 6.0 micrometers or more are more preferable, and 7.0 micrometers or more are further more preferable. Further, the thickness of the cathode 12 is preferably 75 μm or less, more preferably 60 μm or less, and further preferably 50 μm or less. If the thickness of the cathode 12 is within the above range, the electrode reaction and the vicinity of the interface between the cathode 12 and the electrolyte layer 13 (where the barrier layer 14 is provided, the cathode 12 and the barrier layer 14), which is the place of the electrode reaction It is easy to balance the gas permeability to the well.

  The anode-supported cell 1 can be manufactured by the method as described above.

  Next, structural features of an example of the cathode 12 of the present embodiment will be described. The cathode of this embodiment can be preferably obtained by the manufacturing method described above.

  In the cathode 12, the 10% particle diameter (D10) and the 90% particle diameter (D90) in the cumulative particle size distribution based on the number of particles constituting the cathode 12 satisfy the relationship of 2.45 ≦ D90 / D10 ≦ 10.00. It is possible. Here, the cumulative particle size distribution based on the number of particles constituting the cathode 12 is an arbitrary image constituting the cathode 12 in a cross-sectional image obtained by an electron microscope of a section excluding 1 mm from the peripheral edge of the cathode 12. For 100 particles, the projected area (cross-sectional area) of each particle is measured using image processing software, the area equivalent diameter is obtained using the measured value, and the area equivalent diameter of the obtained 100 particles is obtained. Particle size distribution.

  When the particles constituting the cathode 12 satisfy 2.45 ≦ D90 / D10 ≦ 10.00, cracks and separation are reduced, and the cathode can realize high power generation performance. As a result, high performance and high reliability are achieved. It is possible to realize an SOFC having In order to obtain these effects more reliably, D90 / D10 is preferably 2.5 or more, and D90 / D10 is more preferably 2.6 or more.

Next, the structural features of an example of the single cell for SOFC of this embodiment (in the case of this embodiment, the anode-supported cell 1) will be described. The cathode of this embodiment can be preferably obtained by the manufacturing method described above. An example of the anode-supported cell 1 obtained in the present embodiment is that the cathode 12 is observed when cross sections of any five locations at positions excluding 1 mm from the peripheral end of the cathode 12 are observed with an electron microscope over 200 μm. / Barrier layer 14 (in the case of a configuration in which no barrier layer is provided), the number of peeled portions present in a unit length of 1 mm of the interface of the cathode 12 / electrolyte layer 13 is 7 or less, and the number of cracks in the cathode is It can be identified as a single cell for SOFC having an ASR at 750 ° C. of 0.4 Ω · cm ² or less. However, ASR is a value calculated | required by the following formula | equation.
ASR = (open circuit voltage−cell voltage) / current density

ASR at 750 ° C. of the SOFC single cell, is preferably 0.3 [Omega · cm ² or less, and more preferably 0.28Ω · cm ² or less.

  In the single cell for SOFC of this embodiment, the adjacent layer includes a form that is the electrolyte layer 13 and a form that is the barrier layer 14 disposed between the electrolyte layer 13 and the cathode 12. Preferred embodiments such as the cathode material, the thickness of the cathode 12, the material of the electrolyte layer 13, the thickness of the electrolyte layer 13, the material constituting the barrier layer 14, the thickness of the barrier layer 14 and the like are as described above. The anode layer 112 and the anode material constituting the anode support substrate 111 in the single cell for SOFC of the present embodiment, and the preferred modes of the respective thicknesses are also as described above.

  As described above, the single cell for SOFC obtained in the present embodiment is reduced in cracks and peeling generated in the cathode, and has excellent power generation performance (for example, high cell voltage and low ASR).

  Next, the present invention will be specifically described using examples. In addition, this invention is not limited at all by the Example shown below.

<Example 1>
(Preparation of anode support substrate green sheet)
60 parts by mass of nickel oxide as a conductive component (manufactured by Shodo Chemical Co., Ltd., GREEN), 3 mol% yttria-stabilized zirconia powder as a skeleton component (3YSZ: manufactured by Daiichi Rare Chemicals, HSY-3.0) 40 masses Part, 3 parts by mass of commercially available carbon black as a pore-forming agent, 15 parts by mass of a binder made of a commercially available acrylic resin, 2 parts by mass of an α-olefin / maleic anhydride copolymer as a plasticizer, and a carboxyl group-containing polymer as a dispersant 2 parts by mass of the modified product, 30 parts by mass of commercially available toluene as a solvent, and 24 parts by mass of commercially available ethyl acetate were mixed by a ball mill to prepare a slurry. The obtained slurry was used, formed into a sheet by a doctor blade method, and dried at 80 ° C. for 2 hours to produce an anode supporting substrate green sheet. In addition, about the thickness of the produced green sheet, it adjusted so that the thickness after baking might be set to 300 micrometers.

(Preparation of anode layer paste)
60 parts by mass of nickel oxide as a conductive component, 40 parts by mass of 8 mol% yttria-stabilized zirconia powder (8YSZ: manufactured by Daiichi Rare Element Co., Ltd., HSY-8.0) as a skeleton component, commercially available as a pore forming agent 3 parts by weight of carbon black, 55 parts by weight of commercially available α-terpineol as a solvent, 12 parts by weight of commercially available methacrylic resin as a binder, 5 parts by weight of commercially available dibutyl phthalate as a plasticizer, and a commercially available sorbitan fatty acid ester as a dispersant After preliminarily mixing 8 parts by mass of a system surfactant, the mixture was pulverized using a three-roll mill (manufactured by EXKT technologies, model “M-80S”, roll material: alumina) to prepare an anode layer paste.

(Preparation of electrolyte layer paste)
100 parts by mass of 8 mol% yttria stabilized zirconia powder (8YSZ: manufactured by Daiichi Rare Element Co., Ltd., HSY-8.0) as a ceramic material, 7.5 parts by mass of ethyl cellulose commercially available as a binder, and α-terpineol commercially available as a solvent After premixing 67.5 parts by mass, 6 parts by mass of commercially available dibutyl phthalate as a plasticizer and 10 parts by mass of a commercially available sorbitan acid surfactant as a dispersant, a three-roll mill (manufactured by EXAK Technologies, model “M” An -80S "roll material: alumina) was crushed to prepare an electrolyte layer paste.

(Preparation of barrier layer paste)
100 parts by mass of ceria powder (AGC Seimi Chemical, catalog value: specific surface area 10 m ² / g) in which 20 mol% gadolinia as a ceramic material is dissolved, 7.5 parts by mass of ethyl cellulose commercially available as a binder, α -After premixing 67.5 parts by mass of terpineol, 8 parts by mass of commercially available dibutyl phthalate as a plasticizer and 20 parts by mass of a commercially available sorbitan acid ester surfactant as a dispersant, a three-roll mill (manufactured by EXKT technologies, model number) Crushing using “M-80S” roll material: alumina), a barrier layer paste was prepared.

(Formation of green layer for anode layer)
The anode layer paste was printed on the anode support substrate green sheet obtained above by screen printing so that the thickness after firing was 15 μm and dried at 80 ° C. for 30 minutes to form the anode layer green layer. .

(Formation of green layer for electrolyte layer)
The electrolyte layer paste is printed on the anode layer green layer obtained above by screen printing so that the thickness after firing is 10 μm and dried at 80 ° C. for 30 minutes. Formed.

(Formation of green layer for barrier layer)
The barrier layer paste is printed on the green layer for the electrolyte layer obtained above by screen printing so that the thickness after firing is 2 μm or less, and is dried at 80 ° C. for 30 minutes. Formed.

(Baking)
After drying the barrier layer paste, the green layer for the barrier layer, the green layer for the electrolyte layer, and the green layer for the anode layer obtained above are coated and laminated on the anode supporting substrate green sheet, and one side after firing is 6 cm in length. Punched out to be square. After punching, firing was performed at 1350 ° C. in an air atmosphere for 3 hours to obtain an anode-supported half cell.

(Preparation of LSC powder (cathode powder))
LSC powder was prepared as follows. Commercially available 99.9% pure lanthanum acetate hemihydrate (Kishida Chemical, 99.5%), strontium acetate hemihydrate (Wako Pure Chemicals, Wako Special Grade) and cobalt (II) acetate tetrahydrate A Japanese product (Wako Pure Chemicals, Wako Special Grade) was dissolved in pure water so that the element ratio was La _0.6 Sr _0.4 Co _1.0 O _x, and it was visually confirmed that it was dissolved, and then stirred for 30 minutes. The obtained aqueous solution was dropped into an excess of an aqueous solution of ammonium oxalate monohydrate (Wako Pure Chemicals, reagent grade), 1.5 times the stoichiometric ratio, and coprecipitated as oxalate. Thereafter, this solution was evaporated and dried using a rotary evaporator and a dryer. Ethanol is added to the dried oxalate and wet pulverized and mixed in a mortar, followed by thermal decomposition (330 ° C.), first calcination (750 ° C.), second calcination (950 ° C.), and calcination (1100 ℃) for 3 hours each to produce a fired powder. During each step, wet pulverization was performed in a mortar using ethanol as a solvent for the purpose of preventing excessive aggregation of particles.
Next, the fired powder was pulverized and then dried to prepare LSC powder (A) having an average particle size of 0.23 μm and LSC powder (B) having an average particle size of 1.19 μm. Specifically, for both LSC powders (A) and (B), ball mill crushing was performed in a state where a fired powder, ethanol as a solvent and zirconia balls (YTZ ball made by Nikkato) were charged in a plastic container. The pulverization time was 20 hours for both LSC powders (A) and (B), but powders having different average particle diameters were prepared by changing the number of revolutions during the pulverization process and the YTZ balls used. Further, it was confirmed by X-ray diffraction measurement that both LSC powders (A) and (B) were a single phase composed of perovskite.
The average particle diameter of the LSC powders (A) and (B) is a median diameter obtained from a volume-based cumulative particle size distribution, that is, a particle diameter (D50) corresponding to a volume accumulation of 50%. It is the value calculated | required using the type | formula particle size distribution measuring apparatus (Horiba Seisakusho make, product name: LA-920).

(Preparation of LSC cathode layer paste)
50 parts by mass of the above LSC powder (A), 50 parts by mass of LSC powder (B), 3 parts by mass of commercially available ethyl cellulose as a binder and 30 parts by mass of commercially available α-terpineol as a solvent were premixed. Then, it knead | mixed using the 3 roll mill (EXAKT technologies company make, model "M-80S", roll material: Alumina), and obtained the paste for cathode layers. The average particle size (d50) of the LSC powder in the volume-based cumulative particle size distribution of the cathode powder in the LSC cathode layer paste was 0.67 μm. The 10% particle diameter (d10) was 0.41, the 90% particle diameter (d90) was 1.22 μm, and the ratio of the 90% particle diameter to the 10% particle diameter (d90 / d10) was 3.0. It was. The volume-based cumulative particle size distribution was determined using a laser diffraction particle size distribution measuring device (manufactured by Horiba, product name: LA-920).

(Formation of LSC cathode layer)
A cathode layer paste was applied to a 1 cm × 1 cm square by screen printing on the surface of the barrier layer of the half cell, and dried at 100 ° C. for 30 minutes to form a green layer for the cathode layer. Thereafter, the half cell on which the green layer for the cathode layer was laminated was fired at 1000 ° C. for 2 hours. Thereby, the single cell for SOFC which concerns on Example 1 was obtained.

<Examples 2 and 3>
In the preparation of the LSC cathode layer paste of Example 1, the same procedure as in Example 1 was conducted, except that the mixing ratio of the LSC powder (A) and the LSC powder (B) was as shown in Table 2. A single cell for SOFC of Examples 2 and 3 was prepared by preparing an LSC cathode layer paste and forming an LSC cathode layer in the same manner as in Example 1. The average particle size (d50), 10% particle size (d10), 90% particle size (d90) of the LSC cathode layer paste obtained in Examples 2 and 3 was 90% with respect to the 10% particle size. The ratio (d90 / d10) was as shown in Table 2.

<Comparative Example 1>
In the preparation of the paste for the LSC cathode layer of Example 1, except that 50 parts by mass of LSC powder (A) and 50 parts by mass of LSC powder (B) were used as the powder to be used, except that 100 parts by mass of LSC powder (A) was used. An LSC cathode layer paste was prepared in the same manner as in Example 1, and an LSC cathode layer was formed in the same manner as in Example 1 to produce a single cell for SOFC of Comparative Example 1. The average particle diameter (d50), 10% particle diameter (d10), 90% particle diameter (d90), and 90% particle diameter with respect to the 10% particle diameter of the LSC cathode layer paste obtained in Comparative Example 1 The ratio (d90./d10) was as shown in Table 2.

<Comparative Example 2>
In the preparation of the paste for the LSC cathode layer of Example 1, except that 50 parts by mass of LSC powder (A) and 50 parts by mass of LSC particles (B) were used as powders, 100 parts by mass of LSC powder (B) were used. An LSC cathode layer paste was prepared in the same manner as in Example 1, and an LSC cathode layer was formed in the same manner as in Example 1 to produce a single cell for SOFC of Comparative Example 2. In addition, the average particle diameter (d50), 10% particle diameter (d10), 90% particle diameter (d90) of the LSC powder in the LSC cathode layer paste obtained in Comparative Example 2 was 90% particle diameter relative to the 10% particle diameter. The ratio (d90 / d10) was as shown in Table 2.

<Comparative Example 3>
(Preparation of LSCF powder)
LSCF powder was prepared as follows. Commercially available 99.9% pure lanthanum acetate hemihydrate (Kishida Chemical, 99.5%), strontium acetate hemihydrate (Wako Pure Chemicals, Wako Special Grade) and cobalt (II) acetate tetrahydrate Japanese products (Wako Pure Chemicals, Wako Special Grade), iron (II) sulfate heptahydrate (Wako Pure Chemicals, reagent special grade) are dissolved in pure water so that the element ratio is La _0.6 Sr _0.4 Co _0.2 Fe _0.8 The mixture was stirred for 30 minutes after visually confirming that it was dissolved. The obtained aqueous solution was dropped into an excess of an aqueous solution of ammonium oxalate monohydrate (Wako Pure Chemicals, reagent grade), 1.5 times the stoichiometric ratio, and coprecipitated as oxalate. Thereafter, this solution was evaporated and dried using a rotary evaporator and a dryer. Ethanol is added to the dried oxalate and wet pulverized and mixed in a mortar, followed by pyrolysis (330 ° C), first calcining (750 ° C), second calcining (950 ° C), and calcining (1200) ℃) for 3 hours each to produce a fired powder. In addition, between each process, in order to prevent the excessive aggregation of particle | grains, the wet pulverization is performed in a mortar by using ethanol as a solvent.
Next, the pulverized powder was subjected to ball mill crushing treatment for 20 hours in a state where it was charged into a plastic container together with ethanol and zirconia balls (YKKato YTZ balls) as a solvent, and then dried to obtain LSCF powder. The obtained LSCF powder had an average particle size of 0.24 μm and was confirmed to be a single phase composed of perovskite by X-ray diffraction measurement.

(Preparation of LSCF cathode layer paste)
These were added to the LSCF powder prepared by the above method so that the commercially available ethylcellulose as the binder was 3% by mass and the commercially available α-terpineol as the solvent was 30% by mass. Used and mixed. Then, it knead | mixed using the 3 roll mill (EXAKT technologies company make, model "M-80S", roll material: Alumina), and obtained the paste for cathode layers. In addition, the average particle diameter (d50), 10% particle diameter (d10), 90% particle diameter (d90) of the LSCF powder in the LSCF cathode paste obtained in Comparative Example 3 was 90% particle diameter relative to the 10% particle diameter. The ratio (d90 / d10) was as shown in Table 2.

(Formation of LSCF cathode layer)
Instead of (LSC cathode layer formation) in the SOFC production of Example 1, a single layer cell for SOFC was produced by forming a cathode layer using the paste for LSCF cathode layer obtained by the above method. That is, the cathode layer paste was applied to a 1 cm × 1 cm square by screen printing on the barrier layer surface of an anode-supported half cell having a barrier layer produced in the same manner as in Example 1, and dried at 100 ° C. for 30 minutes. Thus, a green layer for the cathode layer was formed. This green layer for cathode layer was fired at 1000 ° C. for 2 hours to obtain a single cell for SOFC according to Comparative Example 3.

<Measurement of average linear thermal expansion coefficient>
The average linear thermal expansion coefficient of the cathode powder (LSC powder, LSCF powder) used for forming the cathode layer and the powder (8YSZ) used for forming the electrolyte layer in Examples and Comparative Examples was measured as follows.

(Preparation of measurement sample)
The LSC powder and the LSCF powder were each formed into a cylindrical shape having a height of about 3 mm using a dia. After molding, it was fired in an electric furnace at 1200 ° C. for 5 hours. Similarly, the powder (8YSZ powder) used to form the electrolyte layer was formed into a cylindrical shape having a height of about 3 mm using a dia. After molding, it was fired in an electric furnace at 1400 ° C. for 5 hours. About the obtained cylindrical sample, the unnecessary protrusion was removed using sandpaper (# 1500), and the sample for a thermal expansion coefficient measurement was obtained. In addition, about these samples for a measurement, an apparent density was calculated | required from the obtained shape and weight, the filling factor (apparent density / true density) was calculated | required, and it confirmed that it was 90% or more.

(Measurement of average linear thermal expansion coefficient)
About the sample for a measurement produced by said method, TMA-4000S made from a Mac Science company was used, and the expansion coefficient between room temperature-1000 degreeC was measured with the temperature increase rate of 2 degree-C / min. In calculating the average linear thermal expansion coefficient, measured values of 100 to 1000 ° C. were used. The obtained results are shown in Table 1.

<Battery performance evaluation test>
About the single cell for SOFC of Examples 1-3 and Comparative Examples 1-3, battery performance was evaluated with the following method. While supplying 100 mL / min of nitrogen to the anode of the SOFC single cell and 100 mL / min of air to the cathode, the temperature was raised to the measurement temperature (750 ° C.) at a rate of 100 ° C./hour. After raising the temperature, the flow rate of the gas on the outlet side of the anode and cathode was measured with a flow meter, and it was confirmed that there was no leakage. Then, a humidified mixed gas of 6 mL / min of hydrogen and 194 mL / min of nitrogen was supplied to the anode, and 200 mL / min of air was supplied to the cathode. After confirming again that electromotive force is generated and gas is not leaked after 1 hour or more has passed, the flow rate of hydrogen and water vapor is 200 mL / min in total for the gas on the anode side (50% hydrogen, 50% water vapor). After 10 minutes or more have passed since the electromotive force has stabilized, confirm that the electromotive force is in the range of 95% to 100% of the theoretical electromotive force, and set the value to the open circuit voltage. It was. Then, the battery performance evaluation test by the current-voltage characteristic was implemented. From the obtained current-voltage characteristics, a voltage (cell voltage) at 0.4 A / cm ² was obtained. Table 2 shows the results of the battery performance evaluation tests of Examples 1 to 3 and Comparative Examples 1 to 3. The single cell for SOFC of Examples 1 to 3 has a cell voltage of 0.800 V or more, an output density of 0.320 W / cm ² or more, and an ASR (= (open circuit voltage−cell voltage) / current density) of 0.4Ω. / Cm < ² > or less, showing power generation performance superior to the single cells of Comparative Examples 1 to 3. Table 2 also shows the results of the open circuit voltage measured for obtaining the ASR.

<Cathode observation>
About the single cell for SOFC of Examples 1-3 and Comparative Examples 1-3 after said battery performance evaluation test, the sample for cross-sectional observation 5 samples was produced, respectively. Using a field emission scanning electron microscope (manufactured by JEOL Ltd .: JSM-7600F), in the cross-sectional observation sample, the cross-section observation is performed on the portion where 1 mm is removed from the peripheral end portion of the portion coated with the cathode. Went.

(Particle size distribution in the cathode)
In the sample of Example 1, the projected area (cross-sectional area) of each particle was measured with respect to 100 particles constituting the cathode from the obtained cross-sectional image, using Image Cyber Pro 4.0 made by Media Cybernetics. Using the value, the equivalent area diameter was determined. The 10% particle size (D10), 50% particle size (D50) and 90% particle size (D90) determined using the number-based cumulative particle size distribution obtained using the area equivalent diameter of 100 particles are: They were 0.32 μm, 0.60 μm and 0.94 μm, respectively. Similarly for the samples of Examples 2 and 3 and Comparative Examples 1 to 3, the 10% particle diameter (D10), 50% particle diameter (D50) and 90% particle diameter (D90) of the particles constituting the cathode were determined. It was. The results are shown in Table 2. In determining the particle size of 100 particles, one field of view sometimes did not satisfy 100 particles. In this case, measurement was performed over a plurality of fields of view, and the particle size of 100 particles in total was obtained.

(Defect observation)
Cracks and delamination were defined as follows.
crack:
The pore area in the cathode cross section was measured using Image-Pro Plus ver 4.0 manufactured by Media Cybernetics, and the portion having the pore area of 5.0 μm ² or more was defined as a crack (see FIG. 2).
Peeling:
At the interface between the cathode and the layer adjacent to the cathode (the barrier layer in this example and the comparative example) and the cathode, a portion not contacting 5 μm or more was defined as peeling (see FIG. 2).
The five cross-sectional observation samples of Example 1 were observed over 200 μm, and the number of occurrences of cracks and peeling per 1 mm of the sample was determined. In Example 1, it was a crack location: 5 pieces / 1 mm, and a peeling location: 0 pieces / 1 mm. Similarly, for the samples of Examples 2 and 3 and Comparative Examples 1 to 3, five cross-sectional observation samples were observed over 200 μm, and the number of cracks and peelings per 1 mm of the sample was determined. The results are shown in Table 3.
The single cells for SOFC of Examples 1 to 3 have a D90 / D10 value in the range of 2.45 to 10.00, and in each case, the cell voltage is 0.800 V or more and the output density is 0.320 W / cm. ^The power generation performance was ² or more, ASR was 0.4 Ω / cm ² or less, and the number of defects was small, with 13 cracks / 1 mm or less and 7 peels / 1 mm or less peeled portions. On the other hand, the SOFC single cells of Comparative Examples 1 to 3 had a D90 / D10 value of less than 2.45, and each cell had lower power generation performance than the cells of the Examples. Further, the SOFC single cell of Comparative Example 1 had a large number of defects.

  According to the manufacturing method of the present invention, it is possible to suppress the occurrence of defects (peeling, cracks) generated in the cathode during the formation of the cathode, so that a high-power SOFC cell can be provided with high reliability. Therefore, the present invention can contribute to high performance and high reliability of SOFC.

DESCRIPTION OF SYMBOLS 1 Anode support type cell 11 Anode 12 Cathode 13 Electrolyte layer 14 Barrier layer 111 Anode support substrate 112 Anode layer

Claims (4)

A method for producing a unit cell for a solid oxide fuel cell comprising a cathode, an anode, and an electrolyte layer disposed between the cathode and the anode,
(I) To form a cathode including a cathode powder made of a cathode material having a difference in average linear thermal expansion coefficient at 100 to 1000 ° C. from the electrolyte material of the electrolyte layer of 8.0 × 10 ⁻⁶ / K or more. Producing a cathode paste of
(II) applying the cathode paste onto the electrolyte layer and baking it to form a cathode;
Including
The cathode powder is a mixture containing cathode powder A and cathode powder B having different average particle sizes,
In the cathode powder, the ratio (P _B50 / P _A50 ) of the average particle diameter (P _B50 ) of the cathode powder B to the average particle diameter (P _A50 ) of the cathode powder A is 1.5 or more and 30 or less. The ratio of the cathode powder A is 5% by mass or more and 90% by mass or less.
A method for producing a single cell for a solid oxide fuel cell. 10% particle diameter (d10) and 90% particle diameter (d90) in the volume-based cumulative particle size distribution of the cathode powder in the cathode paste satisfy the relationship d90 / d10 ≧ 2.3.
The manufacturing method of the single cell for solid oxide fuel cells of Claim 1. A cathode for a solid oxide fuel cell,
10% particle diameter (D10) and 90% particle diameter (D90) in the cumulative particle size distribution based on the number of particles constituting the cathode satisfy the relationship of 2.45 ≦ D90 / D10 ≦ 10.00.
Cathode for solid oxide fuel cells. A solid oxide fuel cell single cell comprising an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode,
The unit length of the interface between the cathode and the adjacent layer adjacent to the cathode when the cross section at any five locations excluding 1 mm from the peripheral edge of the cathode is observed with an electron microscope over 200 μm. There are 7 or less exfoliation points existing in 1 mm, and the number of cracks in the cathode is 13 or less,
The resistance value per unit area (ASR) at 750 ° C. is 0.4 Ω · cm ² or less.
Single cell for solid oxide fuel cells.
However, the ASR is a value obtained by the following equation.
ASR = (open circuit voltage−cell voltage) / current density