JP6130445B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell.

  Conventionally, a fuel cell including a fuel electrode, an air electrode, and a solid electrolyte layer disposed between the fuel electrode and the air electrode is known. The air electrode is made of a porous material (see, for example, Patent Document 1).

JP2012-49115A

  When firing the air electrode or attaching the current collecting member to the air electrode, there is a problem that cracks are likely to occur on the outer surface of the air electrode.

  The present invention has been made in view of the above-described situation, and an object thereof is to provide a fuel cell capable of suppressing cracks on the outer surface of the air electrode.

The fuel cell includes a fuel electrode, an air electrode, and a solid electrolyte layer disposed between the fuel electrode and the air electrode. The air electrode has a surface layer exposed on the outer surface. The surface layer contains a perovskite complex oxide represented by the general formula ABO ₃ as a main component and an oxide containing one or more transition metals.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell which can suppress the crack in the outer surface of an air electrode can be provided.

Sectional drawing which shows the structure of the fuel cell which concerns on 1st Embodiment. Sectional drawing which shows the structure of the fuel cell which concerns on 2nd Embodiment.

Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.
1. First Embodiment (Configuration of Fuel Cell 10)
The configuration of the fuel cell 10 according to the first embodiment will be described with reference to the drawings. The fuel cell 10 is a so-called solid oxide fuel cell (SOFC). The fuel cell 10 may take the form of a vertical stripe type, a horizontal stripe type, a fuel electrode support type, an electrolyte flat plate type, or a cylindrical type.

  FIG. 1 is a cross-sectional view showing the configuration of the fuel cell 10. The fuel cell 10 includes a fuel electrode 20, a solid electrolyte layer 30, a barrier layer 40, and an air electrode 50.

  The fuel electrode 20 functions as an anode of the fuel cell 10. As illustrated in FIG. 1, the fuel electrode 20 includes a fuel electrode current collecting layer 21 and a fuel electrode active layer 22.

The anode current collecting layer 21 is a porous body excellent in gas permeability. As the material constituting the anode current collecting layer 21, materials conventionally used for the anode current collecting layer of SOFC can be used. For example, NiO (nickel oxide) -8YSZ (8 mol% yttria is stabilized). Zirconia) and NiO—Y ₂ O ₃ (yttria). When the anode current collecting layer 21 contains NiO, at least a part of NiO may be reduced to Ni during operation of the fuel cell 10. The thickness of the anode current collecting layer 21 can be set to 0.1 mm to 5.0 mm, for example.

  The anode active layer 22 is disposed on the anode current collecting layer 21. The anode active layer 22 is a denser porous body than the anode current collecting layer 21. As a material constituting the anode active layer 22, materials conventionally used for the anode active layer of SOFC can be used, for example, NiO-8YSZ. When the anode active layer 22 contains NiO, at least a part of NiO may be reduced to Ni during operation of the fuel cell 10. The thickness of the anode active layer 22 can be set to, for example, 5.0 μm to 30 μm.

  The solid electrolyte layer 30 is disposed between the fuel electrode 20 and the air electrode 50. In the present embodiment, the solid electrolyte layer 30 is sandwiched between the fuel electrode 20 and the barrier layer 40. The solid electrolyte layer 30 has a function of transmitting oxygen ions generated at the air electrode 50. The solid electrolyte layer 30 is denser than the fuel electrode 20 and the air electrode 50.

The solid electrolyte layer 30 may contain ZrO ₂ (zirconia) as a main component. The solid electrolyte layer 30 may contain additives such as Y ₂ O ₃ (yttria) and / or Sc ₂ O ₃ (scandium oxide) in addition to zirconia. These additives function as stabilizers. In the solid electrolyte layer 30, the molar composition ratio of the stabilizer to zirconia (stabilizer: zirconia) can be about 3:97 to 20:80. Therefore, examples of the material of the solid electrolyte layer 30 include 3YSZ, 8YSZ, 10YSZ, or ScSZ (scandia-stabilized zirconia). The thickness of the solid electrolyte layer 30 can be 3 micrometers-30 micrometers, for example.

  In the present embodiment, the composition X “contains the substance Y as a main component” means that the substance Y occupies 70% by weight or more, more preferably 90% by weight or more in the entire composition X. Means.

  The barrier layer 40 is disposed between the solid electrolyte layer 30 and the air electrode 50. The barrier layer 40 suppresses the formation of a high resistance layer between the solid electrolyte layer 30 and the air electrode 50. The barrier layer 40 is denser than the fuel electrode 20 and the air electrode 50. The barrier layer 40 can contain a ceria-based material such as GDC (gadolinium doped ceria) or SDC (samarium doped ceria) as a main component. The thickness of the barrier layer 40 can be set to 3 μm to 20 μm, for example.

  The air electrode 50 is disposed on the barrier layer 40. The air electrode 50 functions as a cathode of the fuel cell 10. The air electrode 50 has an inner surface 50S and an outer surface 50T. The inner surface 50S is a surface on the solid electrolyte layer 30 side. The outer surface 50T is a surface opposite to the solid electrolyte layer 30, that is, a surface opposite to the inner surface 50S. In the present embodiment, the entire outer surface 50T is exposed to the outside, but a current collecting member (for example, an interconnector, a conductive mesh, a separator, etc.) may be connected to the outer surface 50T. As shown in FIG. 1, the air electrode 50 includes a base layer 51 and a surface layer 52.

  The base layer 51 is disposed between the solid electrolyte layer 30 and the surface layer 52. In the present embodiment, the base layer 51 is sandwiched between the barrier layer 40 and the surface layer 52. Base layer 51 is in contact with barrier layer 40 at inner surface 50S. The thickness of the base layer 51 in the thickness direction perpendicular to the inner surface 50S can be, for example, 10 μm to 500 μm.

The base layer 51 is a porous body. The base layer 51 contains a perovskite complex oxide represented by the general formula ABO ₃ as a main component. Examples of such perovskite complex oxides include LSCF ((La, Sr) (Co, Fe) O ₃ : lanthanum strontium cobalt ferrite), LSF ((La, Sr) FeO ₃ : lanthanum strontium ferrite), LSC (( La, Sr) CoO ₃ : lanthanum strontium cobaltite), LNF (La (Ni, Fe) O ₃ : lanthanum nickel ferrite), LSM ((La, Sr) MnO ₃ : lanthanum strontium manganate), etc. It is not limited to this.

The base layer 51 may contain (Co, Fe) ₃ O ₄ , SrSO _4, or the like in addition to the main component perovskite complex oxide. These function as structural reinforcements for the air electrode. The average concentration of the perovskite complex oxide in the base layer 51 can be 85 mol% or more, and preferably 90 mol% or more.

  The surface layer 52 is disposed on the base layer 51. The surface layer 52 is exposed on the outer surface 50T. In the present embodiment, the surface layer 52 is formed in a uniform film shape. The surface layer 52 covers the base layer 51 as a whole.

The surface layer 52 is a porous body. The surface layer 52 contains a perovskite type complex oxide represented by the general formula ABO ₃ as a main component and an oxidation containing one or more transition metals (excluding the transition metal contained in the perovskite type complex oxide). (Hereinafter abbreviated as “transition metal oxide”). By adding the transition metal oxide to the surface layer 52, it is possible to promote the sintering of the perovskite complex oxide which is the main component of the surface layer 52. As a result, the skeleton strength of the microstructure of the surface layer 52 is improved, and the occurrence of cracks on the outer surface 50T can be suppressed.

  As the perovskite complex oxide which is the main component of the surface layer 52, the same material as that of the base layer 51 described above can be used. The perovskite complex oxide that is the main component of the surface layer 52 may be the same component as the perovskite complex oxide that is the main component of the base layer 51 or may be a different component.

Examples of the transition metal oxide added to the surface layer 52 include CaO, Sc ₂ O ₃ , TiO ₂ , V ₂ O ₅ , CrO, Cr ₂ O ₃ , MnO, Mn ₃ O ₄ , FeO, Fe ₃ O ₄ , CoO. , Co ₃ O ₄ , NiO, CuO, ZnO _{2 and the} like, but are not limited thereto. The transition metal oxide may be a composite oxide containing two or more transition metals. Considering suppression of the decrease in air electrode activity, Mn ₃ O ₄ , Co ₃ O ₄ and (Mn, Co) ₃ O ₄ are suitable as the transition metal oxide. The transition metal oxide may exist as a heterogeneous phase at the grain boundary of the perovskite complex oxide, which is the main component.

  The average concentration of the perovskite complex oxide that is the main component of the surface layer 52 can be 85 mol% or more and 99.8 mol% or less, and preferably 90 mol% or more and 99.5 mol% or less.

  The average concentration of the transition metal oxide in the surface layer 52 is preferably 0.5 mol% or more and 10 mol% or less. By setting the average concentration of the transition metal oxide to 0.5 mol% or more, generation of cracks in the surface layer 52 can be further suppressed. Moreover, the crack of a porous electrode can be suppressed, improving the joining property of the surface layer 52 by making the average density | concentration of a transition metal oxide or less into 10 mol% or less.

  It is preferable that the concentration of the transition metal oxide in the surface layer 52 decreases as the distance from the outer surface 50T increases. As a result, a local thermal expansion coefficient difference in the air electrode 50 can be suppressed, and stress concentration can be suppressed. The concentration of the transition metal oxide in the surface layer 52 only needs to gradually decrease as the distance from the outer surface 50T increases, and may vary steplessly or stepwise.

  The concentration distribution of the transition metal oxide in the surface layer 52 can be obtained, for example, by line analysis based on an atomic concentration profile, that is, comparison of characteristic X-ray intensities using EPMA (Electron Probe Micro Analyzer). Specifically, in a cross section parallel to the thickness direction of the surface layer 52 (that is, perpendicular to the surface direction perpendicular to the thickness direction), line analysis is performed by EPMA along the thickness direction from the outer surface 50T side to obtain a desired The concentration distribution data of the transition metal oxide can be acquired. In the present embodiment, EPMA is a concept including EDS (Energy Dispersive x-ray Spectroscopy).

  The concentration distribution of the perovskite complex oxide that is the main component of the surface layer 52 can also be obtained by line analysis using an atomic concentration profile. Specifically, in a cross section parallel to the thickness direction of the surface layer 52, the concentration distribution data of each constituent element of the perovskite complex oxide is obtained by performing line analysis with EPMA from the outer surface 50T side along the thickness direction. By doing so, the concentration distribution data of the perovskite complex oxide can be acquired.

  The average depth (that is, average film thickness) of the surface layer 52 in the thickness direction can be set to 1 μm to 5 μm, for example. The average depth of the surface layer 52 is an average distance in the thickness direction between the boundary line between the base layer 51 and the surface layer 52 and the outer surface 50T. The average depth of the surface layer 52 is obtained by arithmetically averaging the depths measured at arbitrary five locations. The boundary line between the base layer 51 and the surface layer 52 is defined by a line indicating a concentration of 50% of the maximum concentration of the transition metal oxide in the vicinity of the outer surface 50T (within 3 μm from the outer surface 50T). The boundary line between the base layer 51 and the surface layer 52 may cross over the constituent particles of the air electrode 50.

(Manufacturing method of fuel cell 10)
Next, an example of a method for manufacturing the fuel cell 10 will be described.

  First, a molded body of the anode current collecting layer 21 is formed by molding the anode current collecting layer material powder by a die press molding method.

  Next, a fuel electrode active layer slurry is prepared by adding PVA (polyvinyl butyral) as a binder to a mixture of the fuel electrode active layer material powder and a pore-forming agent (for example, PMMA). And the molded object of the fuel electrode active layer 22 is formed by printing the slurry for fuel electrode active layers on the molded object of the fuel electrode current collecting layer 21 by a printing method or the like. Thus, a molded body of the fuel electrode 20 is formed.

  Next, terpineol and a binder are mixed with the solid electrolyte layer material powder to prepare a solid electrolyte layer slurry. Then, the solid electrolyte layer 30 molded body is formed by applying the solid electrolyte layer slurry on the molded body of the fuel electrode active layer 22 by a printing method or the like.

  Next, a barrier layer slurry is prepared by mixing terpineol and a binder with the barrier layer material powder. And the molded object of the barrier layer 40 is formed by apply | coating the slurry for barrier layers on the molded object of the intermediate | middle layer 40 by the printing method etc.

  Next, the fuel electrode 20, the solid electrolyte layer 30, and the barrier layer 40 are fired (1350 ° C. to 1450 ° C., 1 hour to 20 hours) to thereby form the fuel electrode 20, the solid electrolyte layer 30, and the barrier layer 40. Form.

  Next, terpineol and a binder are mixed with the material powder of the perovskite complex oxide that is the main component of the base layer 51 to prepare a base layer slurry. And the molded object of the base layer 51 is formed by apply | coating the slurry for base layers on the barrier layer 40 by the printing method etc. FIG. The thickness of the base layer 51 can be adjusted by the number of times of application of the base layer slurry.

  Next, a desired transition metal oxide is added to the material powder of the perovskite type complex oxide which is the main component of the surface layer 52, and further, terpineol and a binder are mixed to prepare a surface layer slurry. Then, the surface layer 52 formed body is formed by applying the surface layer slurry onto the base layer 51 formed body by a printing method or the like. The thickness of the surface layer 52 can be adjusted by the number of application times of the surface layer slurry. The average concentration of the transition metal oxide in the surface layer 52 can be adjusted by the amount of transition metal oxide added. Thus, a molded body of the air electrode 50 is formed.

  In addition, when making the density | concentration of a transition metal oxide so low that it leaves | separates from the outer surface 50T, several types of surface layer slurries which changed the addition amount of the transition metal oxide were prepared, and the slurry for surface layers with little addition amount It may be applied in order.

Next, the air electrode 50 is formed by firing (1000 to 1100 ° C., 1 to 10 hours).
2. Second Embodiment A configuration of a fuel cell 10a according to a second embodiment will be described. The difference between the fuel cell 10a according to the second embodiment and the fuel cell 10 according to the first embodiment is the structure of the surface layer. Therefore, the difference will be mainly described below.

  FIG. 2 is a cross-sectional view showing the configuration of the fuel cell 10a. The fuel cell 10a includes a fuel electrode 20, a solid electrolyte layer 30, a barrier layer 40, an air electrode 50a, and a current collecting member 60. The configurations of the fuel electrode 20, the solid electrolyte layer 30, and the barrier layer 40 are as described in the first embodiment.

  The air electrode 50a has an inner surface 50S and an outer surface 50T. The inner surface 50S is a surface on the solid electrolyte layer 30 side. The outer surface 50T is a surface opposite to the solid electrolyte layer 30. A current collecting member 60 is electrically connected to the outer surface 50T.

  As shown in FIG. 2, the air electrode 50a includes a base layer 51a and a plurality of surface layers 52a.

  The base layer 51 a is disposed on the solid electrolyte layer 30. Base layer 51a is in contact with barrier layer 40 at inner surface 50S. Base layer 51a is partially exposed at outer surface 50T. The base layer 51a is made of the same material as that of the base layer 51 of the first embodiment.

  Each of the plurality of surface layers 52a is exposed to the outer surface 50T. In the plan view of the outer surface 50T, each of the plurality of surface layers 52a is formed in an island shape. In a plan view of the outer surface 50T, the outer circumferences of the plurality of surface layers 52a are surrounded by the base layer 51a. The base layer 51a and the plurality of surface layers 52a integrally form an outer surface 50T. The number, position, and size of the plurality of surface layers 52a can be arbitrarily changed.

Similar to the surface layer 52 of the first embodiment, the surface layer 52a includes a perovskite complex oxide represented by the general formula ABO ₃ as a main component and an oxide including one or more transition metals (hereinafter referred to as “transition”). Abbreviated to “metal oxide”). The perovskite complex oxide and the transition metal oxide are as described in the first embodiment. It is preferable that the concentration of the transition metal oxide in the surface layer 52a decreases as the distance from the outer surface 50T increases. The concentration of the transition metal oxide in the surface layer 52a may gradually decrease as the distance from the center of the surface layer 52a in a plane direction perpendicular to the thickness direction increases.

  The planar shape of the surface layer 52a is not particularly limited, and can be a strip, rectangle, polygon, circle, ellipse, or the like. The average depth of the surface layer 52a in the thickness direction can be set to 1 μm to 5 μm, for example. The average depth of the surface layer 52a is obtained by arithmetically averaging the depths measured at any five locations. The boundary line between the base layer 51a and the surface layer 52a is defined by a line indicating a concentration of 50% of the maximum concentration of the transition metal oxide in the vicinity of the outer surface 50T (within 3 μm from the outer surface 50T).

  The current collecting member 60 is made of a conductive metal material (for example, stainless steel). The current collecting member 60 has a plurality of connecting portions 61. Each of the plurality of connecting portions 61 is formed so as to protrude toward the air electrode 50a. Each of the plurality of connecting portions 61 is electrically connected to the outer surface 50T of the air electrode 50a via a conductive bonding agent (not shown). As the conductive bonding agent, a metal-based material (for example, silver-based material) or a conductive ceramic material (for example, LSCF) can be used. The conductive ceramic material may contain a transition metal oxide.

  In the present embodiment, as shown in FIG. 2, some of the connection portions 61 are arranged on the surface layer 52a. Therefore, since at least a part of the connection portions 61 can be supported by the surface layer 52a having an improved microstructure skeleton strength, it is possible to suppress the occurrence of cracks in the region of the outer surface 50T where the connection portions 61 are connected. it can.

  In this embodiment, as shown in FIG. 2, the connection part 61 is not arrange | positioned on some surface layers 52a among the some surface layers 52a. Therefore, it is possible to suppress the occurrence of cracks in the region of the outer surface 50T where the connecting portion 61 is not connected.

(Manufacturing method of fuel cell 10)
Next, an example of a method for manufacturing the fuel cell 10a will be described.

  First, as described in the first embodiment, the fuel electrode 20, the solid electrolyte layer 30, and the barrier layer 40 are formed.

  Next, a base layer slurry is prepared by mixing terpineol and a binder with a material powder of a perovskite complex oxide which is a main component of the base layer 51a. Then, a base layer slurry is applied on the barrier layer 40 by a dipping method, a printing method, or the like, thereby forming a molded body on the barrier layer 40 side of the base layer 51a.

  Next, a surface layer slurry is prepared by adding a desired transition metal oxide to the material powder of the perovskite complex oxide that is the main component of the surface layer 52a, and further mixing terpineol and a binder. Then, the surface layer slurry is applied to the barrier layer 40 side of the base layer 51a by a dipping method or a printing method, thereby forming a plurality of surface layer 52a formed bodies. The thickness of the surface layer 52a can be adjusted by the number of application times of the surface layer slurry. The average concentration of the transition metal oxide in the surface layer 52a can be adjusted by the amount of transition metal oxide added.

  In addition, when making the density | concentration of a transition metal oxide so low that it leaves | separates from the outer surface 50T, several types of surface layer slurries which changed the addition amount of the transition metal oxide were prepared, and the slurry for surface layers with little addition amount It may be applied in order.

  Next, a base layer slurry is applied by dipping or printing so as to fill the periphery of each of the plurality of surface layers 52a, thereby forming a portion of the base layer 51a that surrounds the surface layer 52a. To do. Thus, a molded body of the air electrode 50a is formed.

  Next, the air electrode 50a is formed by baking (1000-1100 degreeC, 1 to 10 hours) the molded object of the air electrode 50a.

  Next, a conductive bonding agent is applied to a position where the connection portion 61 of the current collecting member 60 is disposed on the outer surface 50T of the air electrode 50a. And the current collection member 60 is set | placed so that the connection part 61 may be arrange | positioned on a conductive adhesive. Subsequently, the conductive bonding agent is solidified by heat treatment (750 to 1000 ° C., 1 to 20 hours).

(Other embodiments)
The present invention is not limited to the first and second embodiments as described above, and various modifications or changes can be made without departing from the scope of the present invention.

  In the first and second embodiments, the fuel cell 10 includes the barrier layer 40. However, the fuel cell 10 may not include the barrier layer 40.

  In the first and second embodiments, the barrier layer 40 has a single layer structure, but may have a multilayer structure in which a dense barrier layer and a porous barrier layer are laminated (in no particular order). .

  In the second embodiment, some of the connection portions 61 among the plurality of connection portions 61 are arranged on the surface layer 52a. However, all the connection portions 61 may be arranged on the surface layer 52a.

  In the second embodiment, the connection portions 61 are not arranged on some of the surface layers 52a among the plurality of surface layers 52a. However, the connection portions 61 may be arranged on all the surface layers 52a.

(Production of sample No. 1 to No. 7)
Sample no. 1-No. A fuel cell according to 7 was produced.

First, a NiO powder and Y ₂ O ₃ powder and the pore former (PMMA) slurry prepared by mixing blended powder and of IPA to prepare a mixed powder by drying under a nitrogen atmosphere.

  Next, the mixed powder is uniaxially pressed (forming pressure 50 MPa) to form a plate 30 mm long × 30 mm wide and 3 mm thick, and the plate is further consolidated by CIP (molding pressure: 100 MPa) to collect the fuel electrode current. A layered compact was prepared.

  Next, a slurry obtained by mixing NiO-8YSZ and PMMA mixed powder and IPA was applied onto the molded body of the anode current collecting layer.

  Next, 8YSZ was mixed with terpineol and a binder to prepare a solid electrolyte layer slurry. Next, the solid electrolyte layer molded body was formed by applying the slurry for the solid electrolyte layer onto the molded body of the fuel electrode.

  Next, a GDC slurry was prepared, and the molded body of the barrier layer was prepared by applying the GDC slurry onto the molded body of the solid electrolyte layer.

  Next, the molded body of the fuel electrode, the solid electrolyte layer, and the barrier layer was fired (1450 ° C., 5 hours) to form the fuel electrode, the solid electrolyte layer, and the barrier layer.

  Next, terpineol and a binder were mixed with the base layer material powder shown in Table 1 to prepare a base layer slurry. Then, a base layer molded body of the air electrode was produced by applying the base layer slurry onto the barrier layer.

  Next, transition metal oxide powder was added to the surface layer material powder shown in Table 1, and terpineol and a binder were further mixed to prepare a surface layer slurry. And the surface layer molded object was produced among the air electrodes by apply | coating the slurry for surface layers on the molded object of a base layer.

  Subsequently, the molded body of each of the base layer and the surface layer of the air electrode was fired (1100 ° C., 1 hour) to form an air electrode.

(Production of sample Nos. 8 and 9)
Except that the surface layer was not formed on the air electrode, the above sample no. 1-No. Sample No. 7 in the same process as in FIG. 8 and 9 were produced. Sample No. In 8, 9, the air electrode is composed only of the base layer.

(Measurement of average transition metal oxide concentration)
Transition metal in the surface layer by cutting each sample parallel to the thickness direction and performing line analysis of the cross section in the thickness direction using FE-EPMA (field emission electron probe microanalyzer, JEOL type JXA-8500F) Oxide concentration distribution data was obtained.

(Crack of outer surface of air electrode after firing)
After the production of the cell, the presence or absence of cracks on the outer surface was confirmed by observing the outer surface of the air electrode of each sample with a microscope. The observation field of cracks by a microscope was 3 mm × 3 mm. In Table 1, a sample having 5 or less cracks was evaluated as “◯ (good)”, a sample having 6 to 9 cracks was evaluated as “△ (good)”, and a sample having 10 or more cracks. Was evaluated as “× (no)”. However, sample no. None of the samples evaluated as “Δ (possible)” in 1-9.

(Crack of outer surface of air electrode after thermal cycle test)
Sample No. in which no peeling was confirmed after firing. For Nos. 1 to 7, the Ar gas and hydrogen gas (4% of Ar) were supplied to the fuel electrode while maintaining the reducing atmosphere, and the temperature was raised from room temperature to 800 ° C. in 2 hours and then to room temperature in 4 hours. The cycle of dropping was repeated 10 times.

  Then, the presence or absence of the crack in an outer surface was confirmed by observing the outer surface of the air electrode of each sample with a microscope. The observation field of cracks by a microscope was 3 mm × 3 mm. In Table 1, a sample having 5 or less cracks was evaluated as “◯ (good)”, a sample having 6 to 9 cracks was evaluated as “△ (good)”, and a sample having 10 or more cracks. Was evaluated as “× (no)”. However, sample no. None of the samples evaluated as “x (no)” in 1-7.

  As shown in Table 1, in the sample in which the transition metal oxide was included in the surface layer of the air electrode, generation of cracks after firing could be suppressed. This is because the skeletal strength of the microstructure in the surface layer could be improved by promoting the sintering of the perovskite complex oxide, which is the main component of the surface layer, with the transition metal oxide.

  Further, as shown in Table 1, it was confirmed that in the sample in which the average concentration of the transition metal oxide in the surface layer was 0.5 mol% or more and 10 mol% or less, the occurrence of cracks could be sufficiently suppressed even after the thermal cycle test. .

10, 10a Fuel cell 20 Fuel electrode 30 Solid electrolyte layer 40 Barrier layer 50, 50a Air electrode 51, 51a Base layer 52, 52a Surface layer 60 Current collecting member

Claims (7)

An anode,
The air electrode,
A solid electrolyte layer disposed between the fuel electrode and the air electrode;
With
The air electrode has a surface layer exposed on an outer surface,
The surface layer, the perovskite-type composite oxide represented by the general formula ABO ₃ with as main components, seen containing an oxide containing one or more transition metals other than the transition metal contained in the perovskite-type composite oxide ,
The average concentration of the oxide containing the one or more transition metals in the surface layer is 0.3 mol% or more,
The concentration of the oxide containing the one or more transition metals in the surface layer is so low that it is away from the outer surface,
Fuel cell. The average concentration of the oxide containing the one or more transition metals in the surface layer is 0.5 mol% or more.
The fuel cell according to claim 1. A current collecting member having a plurality of connecting portions electrically connected to the outer surface of the air electrode;
At least one connection portion among the plurality of connection portions is disposed on the surface layer.
The fuel cell according to claim 1 or 2. The surface layer is formed in an island shape,
The fuel cell according to any one of claims 1 to 3. The surface layer is formed in a uniform film shape,
The fuel cell according to any one of claims 1 to 3. The average concentration of the oxide containing the one or more transition metals in the surface layer is 10 mol% or less.
The fuel cell according to any one of claims 1 to 5 . The average depth of the surface layer in the thickness direction perpendicular to the outer surface is within 3 μm.
The fuel cell according to any one of claims 1 to 6 .

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