JP5714738B1 - Fuel cell - Google Patents

Abstract

In a horizontally-striped fuel cell, the frequency of occurrence of “a situation where the gas sealability of an interconnector deteriorates due to the entry of NiO in a fuel electrode into the interconnector due to diffusion during firing” is reduced. thing. In this fuel cell, an interconnector 30 is a part of a “gas seal portion that prevents mixing of fuel gas and air”. The interconnector 30 has a rectangular parallelepiped shape including an outer surface, a bottom surface, and a side surface. The outer surface of the interconnector 30 is in contact with the air electrode current collector film 70 made of a porous material. The bottom surface of the interconnector 30 is connected to the fuel electrode current collector 21 made of a porous material via the intermediate layer 38. The intermediate layer 38 is made of “a material having lanthanum chromite as a main component and having a higher porosity than the interconnector 30”. [Selection] Figure 2

Description

  The present invention relates to a fuel cell.

  Conventionally, “a support substrate having a gas flow path formed therein” and “provided at a plurality of locations separated from each other on the main surface of the support substrate, each including at least a transition metal (typically nickel)” A plurality of power generation element portions in which a fuel electrode, a solid electrolyte membrane, and an air electrode are laminated ”and“ one fuel electrode and the other of the power generation element portions that are provided between adjacent power generation element portions, respectively ” One or a plurality of electrical connections for electrically connecting the air electrode of the gas, a fuel gas supplied from the gas flow path to the fuel electrode, and a gas containing oxygen supplied to the air electrode There is widely known a fuel cell including a gas seal portion made of a dense material that prevents mixing of (see, for example, Patent Document 1). Such a configuration is also called a “horizontal stripe type”.

  In the fuel cell described in the above document, each of the electrical connection portions includes a first portion (interconnector) made of a dense material mainly composed of lanthanum chromite and a porous material connected to the first portion. And a second portion (air electrode current collector film). Each interconnector is connected to one fuel electrode of the adjacent power generation element portion and the air electrode current collector film, and each air electrode current collector film is connected to the other air electrode of the adjacent power generation element portion. Connected to the interconnector. Each interconnector is a part of the gas seal portion.

  Each interconnector includes an outer surface, a bottom surface opposite to the outer surface, and a side surface. The outer surface of each interconnector is in contact with the corresponding air electrode current collector film, and the bottom surface of each interconnector is in contact with the corresponding fuel electrode. The side surface of each interconnector is in contact with a seal portion made of a dense material constituting a part of the gas seal portion.

  Each component of the fuel cell described above is usually formed by firing in an oxidizing atmosphere. For this reason, in the state after the firing, nickel (Ni) in the fuel electrode is nickel oxide (NiO), and the conductivity of the fuel electrode is lowered. Therefore, in order to obtain the conductivity of the fuel electrode, usually, after the firing, reducing fuel gas is allowed to flow from the support substrate side at 800 to 1000 ° C. for 1 to 10 hours to convert NiO in the fuel electrode to Ni. (Reduction process) is performed.

  By the way, during the firing, a phenomenon may occur in which NiO in the fuel electrode enters the interconnector via the bottom surface of the interconnector due to diffusion. When NiO enters the interconnector in this manner, the sinterability of the lanthanum chromite, which is the main component constituting the interconnector, is likely to be reduced (the densification is likely to be insufficient) (hereinafter referred to as “first” Called "cause"). As a result, due to the first cause, the gas sealability of the interconnector (= part of the gas seal portion) is likely to deteriorate after the firing.

  In addition, at the time of firing, when the reduction treatment is performed with NiO entering the interconnector as described above (and when the fuel cell is operated after the reduction treatment), NiO in the interconnector is reduced to Ni. With the change from NiO to Ni, a space corresponding to the volume of oxygen (O) removed is formed inside the interconnector made of a dense material.

  Therefore, if the degree of NiO entering the interconnector is large, the total volume of the space formed in the interconnector increases (hereinafter referred to as “second cause”). As a result, due to the second cause, the gas sealability of the interconnector (= a part of the gas seal portion) is likely to deteriorate after the firing and after the reduction treatment.

  In particular, when NiO that has entered the interconnector through the bottom surface of the interconnector reaches the outer surface of the interconnector in the interconnector, the NiO extends from the bottom surface to the outer surface in the interconnector. A space is formed. For this reason, the gas-sealing property of the interconnector is particularly likely to deteriorate. As described above, “the gas sealability of the interconnector is deteriorated due to the entry of NiO in the fuel electrode into the interconnector due to the diffusion during the firing (and thus the first and second causes)” It has been desired to reduce the frequency of occurrence of the above.

Japanese Patent No. 5417548

  An object of the present invention is a horizontally-striped fuel cell in which “the gas sealability of the interconnector is reduced due to the entry of NiO in the fuel electrode into the interconnector due to diffusion during firing”. An object of the present invention is to provide an apparatus that can reduce the occurrence frequency.

  The fuel cell according to the present invention includes a support substrate, a plurality of power generation element portions, and one or a plurality of electrical connection portions similar to those described in the above-mentioned document. In addition, in the fuel cell according to the present invention, the first part of each electrical connection part is a part of the gas seal part, and the first part of each electrical connection part is the same as that described in the above document. One portion includes an outer surface, a bottom surface opposite to the outer surface, and a side surface, and the outer surface (or the outer surface and the side surface) of the first portion of each electrical connection portion is It is in contact with the corresponding second part of the electrical connection.

  The fuel cell according to the present invention is characterized in that the bottom surface of the first portion of each electrical connection portion is made of a material having “lanthanum chromite as a main component and having a larger porosity than the first portion of the electrical connection portion. The intermediate layer is connected to the corresponding fuel electrode. In other words, only the bottom surface among the outer surface, the side surface, and the bottom surface of the first portion of each electrical connection portion is connected to the fuel electrode via the intermediate layer.

  According to the above configuration, unlike the configuration described in the above document (the configuration in which the bottom surface of the first portion of the electrical connection portion is in direct contact with the fuel electrode), the bottom surface of the first portion of the electrical connection portion is And connected to the fuel electrode via the intermediate layer. Here, in general, when a substance moves inside the object by diffusion, the substance tends to move along the inner wall of the pores in the object. Therefore, if the porosity of the object is large, the movement path of the substance tends to bend, and therefore the movement path becomes longer. In other words, the larger the porosity of the object, the more difficult the substance moves (the more difficult the substance diffuses).

  The above configuration is based on such knowledge. According to the above configuration, in order for NiO in the fuel electrode to enter the interconnector via the bottom surface of the first portion of the electrical connection portion, NiO has to pass through the inside of the intermediate layer having a high porosity. Need to pass. Therefore, compared to the configuration described in the above document, NiO in the fuel electrode is less likely to enter the interconnector. As a result, it is possible to reduce the occurrence frequency of the “situation where the gas sealing performance of the first portion of the electrical connection portion is deteriorated” due to the first and second causes.

In addition, according to the above configuration, the main component (= lanthanum chromite) of the material constituting the first portion of the electrical connection portion and the main component (= lanthanum chromite) of the material constituting the intermediate layer are common. doing. Therefore, an “undesired reaction” hardly occurs at the interface between the first portion of the electrical connection portion and the intermediate layer. As a result, problems such as a decrease in power generation efficiency of the fuel cell due to “undesired reactions” are unlikely to occur. Here, the “main component” refers to a component whose proportion (mass ratio) in the material constituting the object is 80% or more. As used herein, “lanthanum chromite” refers to a substance containing an element such as Ca, Mg, Sr and the like represented by the chemical formula LaCrO ₃ .

  Furthermore, lanthanum chromite is a material that is stable in both oxidizing and reducing atmospheres. The first portion of the electrical connection portion and the intermediate layer can be exposed to either an oxidizing atmosphere or a reducing atmosphere. Therefore, according to the said structure, the 1st part of the said electrical connection part and the said intermediate | middle layer can exist stably in any of oxidizing atmosphere and reducing atmosphere.

  The present inventor, when the porosity of the intermediate layer is 15 to 50% and the thickness of the intermediate layer is 3 to 50 μm, compared with the case where it is not so, after the firing and the reduction treatment Later, it was found that the gas sealability of the first portion of the electrical connection can be maintained well.

  Furthermore, the present inventor has found that the element concentration of the transition metal (typically Ni) in the region whose distance from the outer surface in the first portion of each electrical connection portion is 3 μm or less is 3% or less. It has also been found that the gas sealability of the first portion of the electrical connection portion is less likely to deteriorate after the endurance test as compared with the case where it is not.

1 is a perspective view showing a fuel cell according to the present invention. FIG. 2 is a cross-sectional view corresponding to line 2-2 of the fuel cell shown in FIG. It is the top view which showed the state of the fuel electrode, the interconnector, and the seal | sticker which were embed | buried under the recessed part formed on the main surface of the support substrate shown in FIG. It is a figure corresponding to FIG. 3 in the state in which the solid electrolyte membrane was formed on the main surface of a support substrate. It is a figure for demonstrating the operation state of the fuel cell shown in FIG. It is a figure for demonstrating the flow of the electric current in the operating state of the fuel cell shown in FIG. It is a perspective view which shows the support substrate shown in FIG. FIG. 3 is a cross-sectional view corresponding to FIG. 2 in a first stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 3 is a cross-sectional view corresponding to FIG. 2 in a second stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 3 is a cross-sectional view corresponding to FIG. 2 in a third stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 4 is a cross-sectional view corresponding to FIG. 2 in a fourth stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 6 is a cross-sectional view corresponding to FIG. 2 in a fifth stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 7 is a cross-sectional view corresponding to FIG. 2 in a sixth stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 8 is a cross-sectional view corresponding to FIG. 2 in a seventh stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 7 is a cross-sectional view corresponding to FIG. 2 in an eighth stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 10 is a cross-sectional view corresponding to FIG. 2 in a ninth stage in the manufacturing process of the fuel cell shown in FIG. 1. FIG. 10 is a cross-sectional view corresponding to FIG. 2 in a tenth stage in the manufacturing process of the fuel cell shown in FIG. 1. It is an enlarged view around the interconnector in the fuel cell according to the comparative example. In the comparative example shown in FIG. 18, it is a figure for demonstrating a mode that NiO in a fuel electrode current collection part approachs into an interconnector by diffusion. It is an enlarged view around the interconnector in this embodiment shown in FIG. In this embodiment shown in FIG. 20, it is a figure for demonstrating a mode that NiO in a fuel-electrode current collection part approachs into an interconnector by diffusion. FIG. 21 is a graph showing a comparison of the Ni concentration distribution in the thickness direction in the interconnector between the comparative example shown in FIG. 18 and the present embodiment shown in FIG. 20. It is a figure for demonstrating "the area | region where the distance from the outer surface of the interconnector in an interconnector is 3 micrometers or less" in this embodiment shown in FIG. FIG. 2 is a schematic diagram showing a “structure around a recess formed in an outer surface of a fuel electrode” in the fuel cell shown in FIG. 1. It is sectional drawing corresponding to FIG. 24 of the 1st modification of the fuel cell which concerns on this invention. It is sectional drawing corresponding to FIG. 24 of the 2nd modification of the fuel cell which concerns on this invention. FIG. 25 is a cross-sectional view corresponding to FIG. 24 of a third modification of the fuel cell according to the present invention. FIG. 25 is a cross-sectional view corresponding to FIG. 24 of a fourth modification of the fuel cell according to the present invention. FIG. 10 is a cross-sectional view corresponding to FIG. 2 of a fifth modification of the fuel cell according to the present invention.

(Constitution)
FIG. 1 shows an embodiment of a solid oxide fuel cell (SOFC) according to the present invention (hereinafter also referred to as “this embodiment”). In the present embodiment, a plurality of (books) electrically connected in series to the upper and lower surfaces (main surfaces (planes) on both sides parallel to each other) of the flat support substrate 10 having a longitudinal direction (x-axis direction). In the example, there are four so-called power generation element portions A that are arranged at predetermined intervals in the longitudinal direction and have a so-called “horizontal stripe type” configuration.

  The overall shape of the present embodiment as viewed from above is, for example, a rectangle whose length in the longitudinal direction is 50 to 500 mm and whose length in the width direction (y-axis direction) perpendicular to the longitudinal direction is 10 to 100 mm. The total thickness of the SOFC structure is 1 to 5 mm. The entirety of this embodiment has a vertically symmetrical shape with respect to a plane that passes through the center in the thickness direction and is parallel to the main surface of the support substrate 10. Hereinafter, in addition to FIG. 1, details of the present embodiment will be described with reference to FIG. 2, which is a partial cross-sectional view corresponding to line 2-2 shown in FIG. 1 of the present embodiment. FIG. 2 is a partial cross-sectional view showing a configuration (part of) each of a typical pair of adjacent power generation element portions A and A and a configuration between the power generation element portions A and A. The configuration between the other power generation element portions A and A in other sets is the same as the configuration shown in FIG.

  The support substrate 10 is a flat plate-like fired body made of a porous material having no electronic conductivity. As shown in FIG. 7 to be described later, a plurality of (six in this example) fuel gas passages 11 (through holes) extending in the longitudinal direction are provided in the support substrate 10 at predetermined intervals in the width direction. Is formed. In this example, each recess 12 includes a bottom wall made of the material of the support substrate 10 and side walls closed in the circumferential direction made of the material of the support substrate 10 over the entire circumference (two side walls along the longitudinal direction and the width direction). A rectangular parallelepiped depression defined by two side walls).

The support substrate 10 can be made of, for example, CSZ (calcia stabilized zirconia). Alternatively, it may be composed of NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia), NiO (nickel oxide) and Y ₂ O ₃ (yttria), or MgO. (Magnesium oxide) and MgAl ₂ O ₄ (magnesia alumina spinel) may be used.

  The support substrate 10 may be configured to include “transition metal oxide or transition metal” and insulating ceramics. As the “transition metal oxide or transition metal”, NiO (nickel oxide) or Ni (nickel) is suitable. The transition metal can function as a catalyst for promoting a reforming reaction of the fuel gas (hydrocarbon-based gas reforming catalyst).

Further, as the insulating ceramic, MgO (magnesium oxide) or “mixture of MgAl ₂ O ₄ (magnesia alumina spinel) and MgO (magnesium oxide)” is preferable. Further, CSZ (calcia stabilized zirconia), YSZ (8YSZ) (yttria stabilized zirconia), Y ₂ O ₃ (yttria) may be used as the insulating ceramic.

  As described above, since the support substrate 10 contains “transition metal oxide or transition metal”, the gas containing the residual gas component before the reforming is supplied to the fuel through the numerous pores inside the porous support substrate 10. In the process of being supplied from the gas flow path 11 to the fuel electrode, the catalytic action can promote the reforming of the residual gas component before the reforming. In addition, the insulating property of the support substrate 10 can be ensured by the support substrate 10 containing insulating ceramics. As a result, insulation between adjacent fuel electrodes can be ensured.

  The thickness of the support substrate 10 is 1 to 5 mm. The porosity of the support substrate 10 is 20 to 60% after “reduction treatment” described later. Hereinafter, the porosity values of the other members are also values after the reduction treatment. The porosity was measured by polishing the cross section of the resin-embedded sample (after the reduction treatment) and analyzing the image (secondary electron image) of the cross section by SEM (scanning electron microscope). . The acceleration voltage of SEM was set to 5 kV, and the magnification of SEM was set to 5000 times or 7500 times. The measurement of the porosity was performed on arbitrary 10 cross-sections of the sample, and the average value thereof was adopted as the porosity value.

  Hereinafter, only the configuration on the upper surface side of the support substrate 10 will be described in consideration of the fact that the shape of the structure is vertically symmetrical. The same applies to the configuration of the lower surface side of the support substrate 10.

  As shown in FIGS. 2 and 3, the entire fuel electrode current collector 21 is embedded (filled) in each recess 12 formed in the upper surface (upper main surface) of the support substrate 10. Therefore, each fuel electrode current collector 21 has a rectangular parallelepiped shape. A recess 21 a is formed on the upper surface (outer surface) of each fuel electrode current collector 21. Each recess 21a includes a bottom wall made of the material of the fuel electrode current collector 21 and a side wall (two side walls along the longitudinal direction) closed in the circumferential direction made of the material of the fuel electrode current collector 21 over the entire circumference. And two side walls along the width direction).

  The entire anode active portion 22 is embedded (filled) in each recess 21a. Accordingly, each fuel electrode active portion 22 has a rectangular parallelepiped shape. A fuel electrode 20 is configured by the fuel electrode current collector 21 and the fuel electrode active unit 22. The fuel electrode 20 (the fuel electrode current collector 21 + the fuel electrode active part 22) is a fired body made of a porous material having electron conductivity. The four side surfaces and the bottom surface of each anode active portion 22 are in contact with the anode current collecting portion 21 in the recess 21a.

The fuel electrode active part 22 can be composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). Or you may comprise from NiO (nickel oxide) and GDC (gadolinium dope ceria). The fuel electrode current collector 21 can be composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). Alternatively, it may be composed of NiO (nickel oxide) and Y ₂ O ₃ (yttria), or may be composed of NiO (nickel oxide) and CSZ (calcia stabilized zirconia). The thickness of the anode active portion 22 is 5 to 30 μm, and the thickness of the anode current collecting portion 21 (that is, the depth of the recess 12) is 50 to 500 μm. The porosity of the fuel electrode current collector 21 is 25 to 50%, and the porosity of the fuel electrode active part 22 is also 25 to 50%.

  As described above, the fuel electrode current collector 21 includes a substance having electronic conductivity. The fuel electrode active part 22 includes a substance having electron conductivity and a substance having oxygen ion conductivity. The “volume ratio of the substance having oxygen ion conductivity with respect to the entire volume excluding the pore portion” in the anode active portion 22 is “having oxygen ion conductivity with respect to the entire volume excluding the pore portion” in the anode current collecting portion 21. It is larger than the “volume ratio of the substance”.

  A recess 21b is formed in a portion of the upper surface (outer surface) of each fuel electrode current collector 21 excluding the recess 21a. Each recess 21b includes a bottom wall made of a material of the fuel electrode current collector 21 and a circumferentially closed side wall made of the material of the fuel electrode current collector 21 (two side walls along the longitudinal direction). And two side walls along the width direction).

  In each recess 21 b, an interconnector 30, a seal portion 35 (corresponding to the “second seal portion”), and an intermediate layer 38 are embedded (filled). Specifically, as shown in FIG. 3, in each recess 21b, “a laminated body in which the interconnector 30 is stacked on the intermediate layer 38” is embedded (arranged) in the central portion of the recess 21b. . Each interconnector 30 and each intermediate layer 38 have a (thin) rectangular parallelepiped shape having two side walls (side surfaces) along the longitudinal direction and two side walls (side surfaces) along the width direction.

  Each of the seal portions 35 includes a peripheral portion located around the “laminated body including the interconnector 30 and the intermediate layer 38” in the concave portion 21b, and the entire circumference of the side wall (inner wall) of the concave portion 21b and the side wall of the laminated body. It is buried (filled) in contact with the entire circumference of the (outer wall). That is, each seal portion 35 has a square frame shape.

  Thus, the bottom surface of each interconnector 30 is in contact with the intermediate layer 38. In other words, the bottom surface of each interconnector 30 is connected to the anode current collector 21 via the intermediate layer 38. The side surface of each interconnector 30 is in contact with the seal portion 35. In addition, the outer side surface (upper surface) of each interconnector 35 is in contact with an air electrode current collector film 70 described later.

The interconnector 30 is a fired body made of a dense material having electronic conductivity. The interconnector 30 is made of a material whose main component is lanthanum chromite. The chemical formula of lanthanum _{chromite, La 1-x A x Cr} 1-y-z B y O 3 ( provided that, A: Ca, at least one element Sr, is selected from Ba, B: Co, Ni, Mg, At least one element selected from Al, 0.05 ≦ x ≦ 0.2, 0.02 ≦ y ≦ 0.22, 0 ≦ z ≦ 0.05). “Lantan chromite is the main component” means that the proportion (mass ratio) of lanthanum chromite in the material constituting the interconnector 30 is 80% or more (the same applies to the intermediate layer 38 described later). The porosity of the interconnector 30 is 10% or less. The thickness of the interconnector 30 is 10 to 100 μm.

The seal part 35 is a fired body made of a dense material having electrical insulation. The seal part 35 contains, for example, a metal oxide, and preferably contains a metal oxide as a main component. Specifically, the metal oxide contains at least one oxide selected from the group consisting of (AE) ZrO ₃ , MgO, MgAl ₂ O ₄ , and Ce _x Ln _1-x O _2. Also good. Here, AE is an alkaline earth metal, Ln is at least one element selected from the group consisting of Y and a lanthanoid, and x satisfies 0 <x ≦ 0.3. Examples of elements corresponding to AE include Mg, Ca, Sr, and Ba. Moreover, transition metal oxides (for example, NiO, Mn ₃ O ₄ , Fe ₂ O ₃ , Cr ₂ O ₃ , CoO) may be included as a trace component. These components may exist as an oxide, or at least one selected from the group consisting of “(AE) ZrO ₃ , MgO, MgAl ₂ O ₄ , and Ce _x Ln _1-x O _2. It may be present in the form of a solid solution in the oxide. The average particle size of the metal oxide is preferably from 0.1 to 5.0 μm, more preferably from 0.3 to 4.0 μm. The thickness of the seal part 35 is 10 to 100 μm. The porosity of the seal part 35 is 10% or less.

The intermediate layer 38 is a fired body made of a porous material having electron conductivity. The intermediate layer 38 is made of a material containing lanthanum chromite as a main component, like the interconnector 30. The chemical formula of lanthanum _{chromite, La 1-x A x Cr} 1-y-z B y O 3 ( provided that, A: Ca, at least one element Sr, is selected from Ba, B: Co, Ni, Mg, At least one element selected from Al, 0.05 ≦ x ≦ 0.2, 0.02 ≦ y ≦ 0.22, 0 ≦ z ≦ 0.05). The porosity of the intermediate layer 38 is larger than the porosity of the interconnector 30 and is 15 to 50%. The thickness of the intermediate layer 38 is 3 to 50 μm.

  The upper surface (outer surface) of the fuel electrode 20 (the fuel electrode current collector 21 and the fuel electrode active unit 22), the upper surface (outer surface) of the interconnector 30, the upper surface (outer surface) of the seal portion 35, and the support substrate 10 With this main surface, one flat surface (the same flat surface as the main surface of the support substrate 10 when the recessed part 12 is not formed) is comprised. That is, no step is formed between the upper surface of the fuel electrode 20, the upper surface of the interconnector 30, the upper surface of the seal portion 35, and the main surface of the support substrate 10.

  A plurality of seal portions 35 and a plurality of seal portions 35 on the outer peripheral surface (including the main surface) extending in the longitudinal direction of the support substrate 10 in a state where the fuel electrode 20, the interconnector 30, the seal portion 35, and the intermediate layer 38 are embedded in the respective recesses 12. The entire surface excluding the portion corresponding to the interconnector 30 is covered with a solid electrolyte membrane 40. More specifically, as shown in FIG. 4, the solid electrolyte membrane 40 is formed on the main surface of the support substrate 10 so as to cover the entire periphery of the outer peripheral surface of the seal portion 35. As a result, the seal portion 35 and the interconnector 30 are in contact with each other, and the seal portion 35 and the solid electrolyte membrane 40 are in contact with each other, while the interconnector 30 and the solid electrolyte membrane 40 are not in contact with each other.

  The solid electrolyte membrane 40 is a fired body made of a dense material having ion conductivity. The solid electrolyte membrane 40 can be made of, for example, YSZ (8YSZ) (yttria stabilized zirconia). Or you may comprise from LSGM (lantern gallate). The thickness of the solid electrolyte membrane 40 is 3 to 50 μm. The porosity of the solid electrolyte membrane 40 is 10% or less.

  That is, the entire outer peripheral surface extending in the longitudinal direction of the support substrate 10 in a state where the fuel electrode 20 is embedded in each recess 12 is covered with a dense layer composed of the interconnector 30, the seal portion 35, and the solid electrolyte membrane 40. ing. This dense layer exhibits a gas sealing function that prevents mixing of the fuel gas flowing in the space inside the dense layer and the air flowing in the space outside the dense layer.

  As shown in FIG. 2, in this example, the solid electrolyte membrane 40 is flattened. As a result, compared with the case where a step is formed in the solid electrolyte membrane 40, the generation of cracks in the solid electrolyte membrane 40 due to stress concentration can be suppressed, and the gas sealing function of the solid electrolyte membrane 40 is reduced. Can be suppressed.

  An air electrode 60 is formed on the upper surface of a portion in contact with each fuel electrode active part 22 in the solid electrolyte membrane 40 via a reaction preventing film 50. The reaction preventing film 50 is a fired body made of a dense material, and the air electrode 60 is a fired body made of a porous material having electron conductivity. The shape of the reaction preventing film 50 and the air electrode 60 viewed from above is substantially the same rectangle as the fuel electrode active part 22.

The reaction preventing film 50 can be made of, for example, GDC = (Ce, Gd) O ₂ (gadolinium-doped ceria). The thickness of the reaction preventing film 50 is 3 to 50 μm. The air electrode 60 can be made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Alternatively, from LSF = (La, Sr) FeO ₃ (lanthanum strontium ferrite), LNF = La (Ni, Fe) O ₃ (lanthanum nickel ferrite), LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite), etc. It may be configured. Further, the air electrode 60 may be configured by two layers of a first layer (inner layer) made of LSCF and a second layer (outer layer) made of LSC. The thickness of the air electrode 60 is 10 to 100 μm.

  The reaction preventing film 50 is interposed because the YSZ in the solid electrolyte film 40 and the Sr in the air electrode 60 react with each other in the SOFC during the production or operation of the SOFC, and the solid electrolyte film 40 and the air electrode. This is to suppress the occurrence of a phenomenon in which a reaction layer having a large electric resistance is formed at the interface with the substrate 60.

  Here, the laminated body formed by laminating the fuel electrode 20, the solid electrolyte membrane 40, the reaction preventing membrane 50, and the air electrode 60 corresponds to the “power generation element portion A” (see FIG. 2). In other words, a plurality (four in this example) of power generating element portions A are arranged on the upper surface of the support substrate 10 at a predetermined interval in the longitudinal direction.

  For each pair of adjacent power generation element portions A and A, the air electrode 60 of one power generation element portion A (on the left side in FIG. 2) and the interconnector of the other power generation element portion A (on the right side in FIG. 2). The air electrode current collecting film 70 is formed on the air electrode 60, the solid electrolyte film 40, and the upper surface of the interconnector 30. The air electrode current collector film 70 is a fired body made of a porous material having electron conductivity. The shape of the air electrode current collector film 70 as viewed from above is a rectangle.

The air electrode current collector film 70 can be made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Alternatively, LSC = (La, Sr) CoO ₃ (lanthanum strontium cobaltite) may be used. Or you may comprise from Ag (silver) and Ag-Pd (silver palladium alloy). The thickness of the air electrode current collector film 70 is 50 to 500 μm. The porosity of the air electrode current collector film 70 is 20 to 60%.

  By forming each air electrode current collecting film 70 in this way, for each pair of adjacent power generation element portions A and A, the air electrode 60 of one power generation element portion A (on the left side in FIG. 2), The other fuel electrode 20 (particularly, the fuel electrode current collector 21) of the power generating element part A (on the right side in FIG. 2) passes through the “air electrode current collector film 70 and interconnector 30” having electronic conductivity. Are electrically connected. As a result, a plurality (four in this example) of power generation element portions A arranged on the upper surface of the support substrate 10 are electrically connected in series. Here, the “air electrode current collector film 70 and the interconnector 30” having electron conductivity correspond to the “electrical connection part”, and the interconnector 30 made of a dense material is the “first electrical connection part”. Corresponding to the “part”, the air electrode current collector film 70 made of a porous material corresponds to the “second part of the electrical connection part”.

  Further, the “interconnector 30, the seal portion 35, and the solid electrolyte membrane 40” made of a dense material correspond to the “gas seal portion”. Here, “the portion sandwiched between the fuel electrode active portion 22 and the air electrode 60” in the solid electrolyte membrane 40 corresponds to the “solid electrolyte membrane as a part of the power generation element portion”, and in the solid electrolyte membrane 40. The “other part” corresponds to the “first seal part”. Further, the seal portion 35 corresponds to the “second seal portion”. In the present application, the “dense material” refers to a material having a porosity that is small enough to have a gas sealing function, and typically has a porosity of 10% or less.

As shown in FIG. 5, the fuel gas (hydrogen gas or the like) flows through the fuel gas flow path 11 of the support substrate 10 as shown in FIG. By exposing the upper and lower surfaces (particularly, each air electrode current collecting film 70) to “gas containing oxygen” (air or the like) (or flowing a gas containing oxygen along the upper and lower surfaces of the support substrate 10), the solid electrolyte An electromotive force is generated by an oxygen partial pressure difference generated between both side surfaces of the film 40. Furthermore, when this structure is connected to an external load, chemical reactions shown in the following formulas (1) and (2) occur, and current flows (power generation state).
(1/2) · O ₂ + 2e ⁻ → O ²⁻ (where: air electrode 60) (1)
H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (in the fuel electrode 20) (2)

  In the power generation state, as shown in FIG. 6, current flows as indicated by an arrow in each pair of adjacent power generation element portions A and A. As a result, as shown in FIG. 5, from the entire SOFC structure (specifically, in FIG. 5, the interconnector 30 of the power generating element portion A on the foremost side and the air electrode of the power generating element portion A on the farthest side in FIG. The power is extracted (via 60).

(Production method)
Next, an example of the manufacturing method of this embodiment will be briefly described with reference to FIGS. 7 to 17, “g” at the end of the symbol of each member represents that the member is “before firing”.

  First, a support substrate molded body 10g having the shape shown in FIG. 7 is produced. The molded body 10g of the support substrate is manufactured by using a method such as extrusion molding or cutting using a slurry obtained by adding a binder or the like to the material of the support substrate 10 (for example, CSZ). obtain. Hereinafter, the description will be continued with reference to FIGS. 8 to 17 showing partial cross sections corresponding to line 8-8 shown in FIG.

  As shown in FIG. 8, when the support substrate molded body 10g is manufactured, as shown in FIG. 9, the fuel electrode current collector is then placed in each recess formed on the upper and lower surfaces of the support substrate molded body 10g. Each of the molded parts 21g is embedded and formed. Next, as shown in FIG. 10, a molded body 22g of the fuel electrode active portion is embedded and formed in each recess formed in the outer surface of the molded body 21g of each fuel electrode current collector. The molded body 21g of each fuel electrode current collector and each of the fuel electrode active parts 22g use, for example, a slurry obtained by adding a binder or the like to the powder of the material of the fuel electrode 20 (for example, Ni and YSZ), It is embedded and formed using printing methods.

Subsequently, as shown in FIG. 11, each concave portion formed in “the portion excluding the portion where the molded body 22 g of the fuel electrode active portion is embedded” on the outer surface of the molded body 21 g of each fuel electrode current collector. In the center portion of the bottom surface, a rectangular parallelepiped intermediate film molded body 38g is embedded and formed. The molded body 38g of each intermediate film is embedded and formed using a slurry obtained by adding a binder or the like to the powder of the material (LaCrO ₃ ) of the intermediate film 38, using a printing method or the like.

Next, as shown in FIG. 12, a rectangular parallelepiped shaped interconnector 30g is embedded and formed on the upper surface of each recess 38g. The molded body 30g of each interconnector is embedded and formed using a slurry obtained by adding a binder or the like to the powder of the material of the interconnector 30 (LaCrO ₃ ) using a printing method or the like.

Next, as shown in FIG. 13, a sealing material molded body 35 g is embedded and formed in the peripheral edge portion of each of the concave portions positioned around the “laminated body including the molded body 30 g and the molded body 38 g”. The molded body 35g of each sealing material is, for example, a printing method using a slurry obtained by adding a binder or the like to the powder of the material of the sealing portion 35 (for example, MgO or a composite material of MgO and CaZrO ₃ ). It is buried and formed using

  Next, as shown in FIG. 14, a plurality of fuel electrode molded bodies (21 g + 22 g) and a plurality of molded bodies 30 g, 35 g, and 38 g are embedded in and formed in the longitudinal direction of the molded body 10 g of the support substrate. A solid electrolyte membrane molded film 40g is formed on the entire surface excluding the respective portions where the plurality of molded bodies 30g and 35g are formed on the outer peripheral surface. The molded membrane 40g of the solid electrolyte membrane is formed using, for example, a printing method, a dipping method, etc., using a slurry obtained by adding a binder or the like to the powder of the material of the solid electrolyte membrane 40 (for example, YSZ). The

  Next, as shown in FIG. 15, a molded membrane 50g of the reaction preventing membrane is formed on the outer surface of the solid electrolyte membrane molded body 40g in contact with the molded body 22g of each fuel electrode. The molded film 50g of each reaction preventing film is formed using a slurry obtained by adding a binder or the like to the powder of the material (for example, GDC) of the reaction preventing film 50, using a printing method or the like.

  Then, 10 g of the support substrate molded body in which various molded films are thus formed is fired in air at 1500 ° C. for 3 hours. Thereby, in this embodiment, the structure of the state in which the air electrode 60 and the air electrode current collection film | membrane 70 are not formed is obtained.

  Next, as shown in FIG. 16, an air electrode forming film 60 g is formed on the outer surface of each reaction preventing film 50. The molded film 60g of each air electrode is formed using a slurry obtained by adding a binder or the like to the powder of the material of the air electrode 60 (for example, LSCF), using a printing method or the like.

  Next, as shown in FIG. 17, for each pair of adjacent power generation element portions, air is formed so as to connect the air electrode forming film 60 g of one power generation element portion and the interconnector 30 of the other power generation element portion. On the outer surface of the electrode forming film 60g, the solid electrolyte film 40, the interconnector 30, and the seal portion 35, an air electrode current collecting film forming film 70g is formed. The forming film 70g of each air electrode current collector film is obtained by using a slurry obtained by adding a binder or the like to the powder of the material of the air electrode current collector film 70 (for example, LSCF), using a printing method or the like. It is formed.

  Then, the support substrate 10 in which the molded films 60g and 70g are thus formed is baked in air at 1050 ° C. for 3 hours. As a result, the SOFC structure shown in FIG. 1 is obtained. At this time, the Ni component in the support substrate 10 and the fuel electrode 20 (the current collector 21 and the active part 22) is NiO by firing in an oxidizing atmosphere (oxygen-containing atmosphere). Therefore, in order to acquire the conductivity of the fuel electrode 20, thereafter, a reducing fuel gas is flowed from the support substrate 10 side, and NiO is reduced at 700 to 1000 ° C. for 1 to 100 hours. This reduction process may be performed during power generation. In the above, an example of the manufacturing method of this embodiment was demonstrated.

(Action / Effect)
Hereinafter, a comparative example shown in FIG. 18 will be described as preparation for explaining the operation and effect of the present embodiment. In this comparative example, the “bottom surface of the interconnector 30 is connected to the fuel electrode current collector 21 via the intermediate layer 38 only in the point that the bottom surface of the interconnector 30 is in direct contact with the fuel electrode current collector 21”. Different from this embodiment.

  As described above, in the SOFC manufacturing process, firing is performed in an oxidizing atmosphere. In this comparative example, since the bottom surface of the interconnector 30 is in direct contact with the fuel electrode current collector 21, as shown in FIG. 19, when the fuel electrode 20 and the interconnector 30 are co-fired, the fuel electrode current collector 21. The NiO inside easily enters the interconnector 30 through the bottom surface of the interconnector 30 by diffusion. When NiO enters the interconnector 30, the sinterability of lanthanum chromite, which is the main component constituting the interconnector 30, is likely to be reduced (the densification is likely to be insufficient) (the above “first cause”). As a result, due to the “first cause”, the gas sealability of the interconnector 30 (= a part of the “gas seal part”) is likely to deteriorate after the firing.

  In addition, at the time of firing, as described above, when the reduction treatment is performed with NiO entering the interconnector 30 (and when the SOFC is operated after the reduction treatment), the interconnect NiO in the connector 30 is reduced to Ni. With the change from NiO to Ni, a space corresponding to the volume of oxygen (O) removed is formed inside the interconnector 30 made of a dense material.

  Therefore, in the comparative example, the degree to which NiO enters the interconnector 30 is likely to increase, and accordingly, the total volume of the space formed in the interconnector 30 is likely to increase (the “second cause”). As a result, due to the “second cause”, the gas sealability of the interconnector 30 (= a part of the “gas seal portion”) is likely to deteriorate after the firing and after the reduction treatment.

  In particular, when NiO that has entered the interconnector 30 through the bottom surface of the interconnector 30 reaches the outer surface (upper surface) of the interconnector 30 in the interconnector 30, it extends from the bottom surface to the outer surface in the interconnector 30. The space is formed across. For this reason, the gas-seal property of the interconnector 30 is particularly likely to deteriorate.

  On the other hand, in this embodiment, as shown in FIG. 20, the bottom surface of the interconnector 30 is connected to the anode current collector 21 via the intermediate layer 38. As described above, the porosity of the intermediate layer 38 is larger than the porosity of the interconnector 30. Here, in general, when a substance moves inside the object by diffusion, the substance tends to move along the inner wall of the pores in the object. Accordingly, as shown in FIG. 21, when NiO moves due to diffusion inside the intermediate layer 38 having a high porosity, the moving path of NiO tends to bend and therefore the moving path becomes long. In other words, NiO is difficult to pass through the inside of the intermediate layer 38 due to diffusion.

  In this embodiment, in order for NiO in the fuel electrode current collector 21 to enter the interconnector 30 via the bottom surface of the interconnector 30, it is necessary for NiO to pass through the intermediate layer 38 having a high porosity. There is. Therefore, compared with the comparative example, NiO in the fuel electrode current collector 21 is less likely to enter the interconnector 30. Hereinafter, this effect is referred to as “NiO ingress suppression effect by the intermediate layer 38”.

  FIG. 22 shows an example of the result of measuring the Ni element concentration distribution in the thickness direction in the interconnector 30 for this embodiment. The Ni element concentration was measured by using the EPMA (Electron Probe Micro Analyzer) to sequentially change the Ni content in the sample cross section from the outer surface side to the bottom surface side of the interconnector 30 (see FIGS. 20 and 22). This was done by measuring and quantifying (see arrows).

  In the present embodiment, the “inhibition effect of NiO entering by the intermediate layer 38” is exhibited, so that the degree of NiO entering into the interconnector 30 is reduced as compared with the comparative example. As a result, in the present embodiment, the occurrence frequency of “the situation where the gas sealability of the interconnector 30 is degraded” due to the “first and second causes” is lower than in the comparative example.

  In addition, according to the present embodiment, the main component of the material constituting the interconnector 30 (= lanthanum chromite) and the main component of the material constituting the intermediate layer 38 (= lanthanum chromite) are common. Therefore, an “undesired reaction” hardly occurs at the interface between the interconnector 30 and the intermediate layer 38. As a result, problems such as a decrease in SOFC power generation efficiency due to “undesired reactions” hardly occur.

  Furthermore, lanthanum chromite is a material that is stable in both oxidizing and reducing atmospheres. The interconnector 30 and the intermediate layer 38 can be exposed to either an oxidizing atmosphere or a reducing atmosphere. Therefore, according to the present embodiment, the interconnector 30 and the intermediate layer 38 can exist stably in both the oxidizing atmosphere and the reducing atmosphere.

(Proper range of porosity and thickness of the intermediate layer)
The present inventor has found that in the SOFC according to the above-described embodiment, the degree of decrease in the gas sealability of the interconnector 30 has a strong correlation with the porosity and thickness of the intermediate layer 38. Hereinafter, test A in which this has been confirmed will be described.

<Test A>
In this test A, a plurality of samples having different combinations of the porosity of the interconnector 30, the porosity of the intermediate layer 38, and the thickness of the intermediate layer 38 were produced for this embodiment. Specifically, as shown in Table 1, eight levels (combinations) were prepared. Ten samples (N = 10) were made for each level. For each sample, “the interface between the interconnector 30 (dense material) and the intermediate layer 38 (porous material)” is obtained in the thickness direction in the cross section obtained based on the analysis result of the cross section of the sample. It was defined as “the position where the porosity changes greatly”. As the thickness of the intermediate layer 38, “the interface between the interconnector 30 and the intermediate layer 38” and “the interface between the intermediate layer 38 and the fuel electrode current collector 21”, which were measured at any 10 points in the cross section, respectively. The average value of the distance was adopted.

In each sample (SOFC shown in FIG. 1), the intermediate layer 38 was interposed between the interconnector 30 and the fuel electrode current collector 21 over the entire bottom surface of the interconnector 30. Each sample was produced using the same method as the above-described “example of manufacturing method of this embodiment”. For each sample, NiO / Ni—YSZ, NiO / Ni—CSZ, NiO / Ni—Y ₂ O ₃ or the like was used as the material of the fuel electrode current collector 21. Interconnector 30 and, as the material of the intermediate layer 38, lanthanum chromite _{(La 1-x A x Cr} 1-y-z B y O 3 ( provided that, A: Ca at least one of, Sr, is selected from Ba Element: B: at least one element selected from Co, Ni, Mg, Al, 0.05 ≦ x ≦ 0.2, 0.02 ≦ y ≦ 0.22, 0 ≦ z ≦ 0.05) ) Was used. The thickness of the interconnector 30 was constant at 30 μm. Regarding the co-firing of the fuel electrode 20 and the interconnector 30, the firing time was 1 to 20 hours, and the firing temperature was 1350 to 1500 ° C. The porosity of each of the interconnector 30 and the intermediate layer 38 was adjusted by adjusting the amount and diameter of the pore former contained in the slurry used for producing the corresponding molded body.

  In this test A, the actual open circuit voltage of the SOFC was measured under the condition where the temperature was 750 ° C. for each sample (SOFC according to the present embodiment) in the stage after the reduction treatment. Then, “the difference between the actual open circuit voltage and the theoretical open circuit voltage” was adopted as an evaluation index of the gas sealability of the interconnector 30. In general, the theoretical open circuit voltage is uniquely determined based on “the temperature of the SOFC” and “the difference in oxygen partial pressure between the fuel electrode side and the air electrode side of the SOFC”. On the other hand, the lower the gas sealability of the interconnector 30, the smaller the oxygen partial pressure difference between the fuel electrode side and the air electrode side of the SOFC from the ideal value (value when the gas seal property is perfect). The open circuit voltage decreases from the theoretical open circuit voltage. That is, the fact that the “difference from the actual open circuit voltage from the theoretical open circuit voltage” is small (large) means that the gas sealability of the interconnector 30 is good (bad). The results of SOFC “Difference from actual open circuit voltage to theoretical open circuit voltage” for each sample are shown in Table 1.

  As can be understood from Table 1, when the intermediate layer 38 is provided (see levels 2 to 8), compared with the case where the intermediate layer 38 is not provided (level 1), “theoretical open circuit of the actual open circuit voltage” “Difference from voltage” is small. That is, the gas sealability of the interconnector 30 is improved. This is considered to be based on the fact that the above-mentioned “inhibition effect of NiO intrusion by the intermediate layer 38” was exhibited.

  In addition, as can be understood from Table 1, when the intermediate layer 38 is provided, particularly when the porosity of the intermediate layer 38 is 15 to 50% and the thickness of the intermediate layer 38 is 3 to 50 μm. Compared with the case where it is not, "the difference from the theoretical open circuit voltage of a real open circuit voltage" becomes still smaller. That is, the gas sealability of the interconnector 30 is further improved. Thus, regarding the gas sealability of the interconnector 30, it is considered that the porosity and thickness of the intermediate layer 38 have an appropriate range based on the following reason. That is, if the thickness of the intermediate layer 38 is too small or the porosity of the intermediate layer 38 is too small, the above-described “inhibition effect of NiO intrusion by the intermediate layer 38” itself is hardly exhibited. As a result, NiO in the fuel electrode current collector 21 can easily enter the interconnector 30, and the “first and second causes” cause a “situation in which the gas sealability of the interconnector 30 decreases”. It becomes easy. On the other hand, if the thickness of the intermediate layer 38 is too large or the porosity of the intermediate layer 38 is too large, the sinterability of the lanthanum chromite that is the main component constituting the interconnector 30 is likely to be hindered. As a result, a “situation in which the gas sealability of the interconnector 30 is degraded” easily occurs.

  From the above, when the porosity of the intermediate layer 38 is 15 to 50% and the thickness of the intermediate layer 38 is 3 to 50 μm, compared to the case where the porosity is not so, after the firing and after the reduction treatment It can be said that the gas sealability of the interconnector 30 is further improved.

(Proper range of Ni element concentration in the interconnector)
The inventor performs the durability test on the present embodiment even when the porosity of the intermediate layer 38 is 15 to 50% and the thickness of the intermediate layer 38 is 3 to 50 μm. Further, the gas sealability of the interconnector 30 can still decrease, and the decrease in the gas sealability of the interconnector 30 can be attributed to the “region where the distance from the outer surface (upper surface) is 3 μm or less” ( It was found that there is a strong correlation with the Ni element concentration in (referred to as “outer surface vicinity region” hereinafter). Hereinafter, test B in which this has been confirmed will be described.

<Test B>
In this test B, a plurality of samples having different combinations of the porosity of the intermediate layer 38, the thickness of the intermediate layer 38, and the Ni element concentration in the region near the outer surface of the interconnector 30 were produced for this embodiment. . Specifically, as shown in Table 2, six kinds of levels (combinations) were prepared. Ten samples (N = 10) were made for each level.

  Each sample (SOFC shown in FIG. 1) was produced using the same method as the above-described “example of production method of this embodiment”, as in Test A. About each sample, it was set as the same as that of the test B about the item, the material, etc. of each structural member other than the porosity and thickness of the intermediate | middle layer 38. FIG. The porosity of the intermediate layer 38 is greater than the porosity of the interconnector 30. The Ni element concentration in the region near the outer surface of the interconnector 30 is measured using the EPMA (Electron Probe Micro Analyzer) to measure the Ni content in the “region near the outer surface of the interconnector 30” in the cross section of the sample. • Made by quantification. The Ni element concentration in the region near the outer surface of the interconnector 30 was adjusted by adjusting the firing time and the firing temperature when the fuel electrode 20 and the interconnector 30 were cofired. As the firing time becomes longer and the firing temperature becomes higher, the degree of diffusion of NiO from the fuel electrode current collector 21 increases, so that the Ni element in the region near the outer surface of the interconnector 30 is increased. The concentration becomes high. As shown in Table 2, in the test B, the porosity of the intermediate layer 38 was adjusted in the range of 15 to 50%, and the thickness of the intermediate layer 38 was adjusted in the range of 3 to 50 μm.

  In this test B, the SOFC was continuously operated for 3,000C for 3000 hours as the durability test for each sample after the reduction treatment. Then, at the stage after this endurance test, the actual open circuit voltage of the SOFC was measured. The results of SOFC “Difference from actual open circuit voltage to theoretical open circuit voltage” for each sample are shown in Table 2.

  As can be understood from Table 2, the Ni element concentration in the region near the outer surface of the interconnector 30 is 3 atm. When the value is larger than%, the “difference from the actual open circuit voltage from the theoretical open circuit voltage” becomes larger after the endurance test than when not. That is, the gas sealability of the interconnector 30 is reduced. This is considered based on the following reasons.

  That is, with respect to the “second cause”, the progress of “a phenomenon in which NiO in the interconnector 30 is reduced to Ni during the reduction process or during operation of the SOFC after the reduction process”. The speed is actually very slow. Therefore, even during the endurance test performed after the reduction treatment, a phenomenon in which NiO is reduced to Ni in the interconnector 30 gradually proceeds. As a result, during the endurance test, the total volume of the space corresponding to the volume of oxygen (O) removed along with the change from NiO to Ni inside the interconnector 30 gradually increases. (The space will grow). Therefore, when NiO has entered from the bottom surface of the interconnector 30 to the outer surface vicinity region during the firing (that is, when the Ni element concentration in the outer surface vicinity region is large), the durability test is performed. In the inside, the space that grows in the interconnector 30 with the progress of reduction of NiO is easily connected from the bottom surface to the outer surface of the interconnector 30. For this reason, it is considered that when the Ni element concentration in the region near the outer surface is large, the gas sealability of the interconnector 30 is likely to deteriorate after the durability test.

  As described above, when the porosity of the intermediate layer 38 is 15 to 50% and the thickness of the intermediate layer 38 is 3 to 50 μm, the Ni element concentration in the region near the outer surface of the interconnector 30 is 3 atm. % Or less, it can be said that the gas sealability of the interconnector 30 is hardly lowered even after the durability test.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, as shown in FIG. 24, the interconnector 30, the seal portion 35, and the intermediate layer 38 are embedded in the recess 21 b formed on the outer surface of the anode current collector 21. Although the entire bottom surface of the connector 30 is in contact with the intermediate layer 38, as shown in FIG. 25, the central portion of the bottom surface of the interconnector 30 is in contact with the intermediate layer 38, and the central portion of the bottom surface of the interconnector 30 is The peripheral edge located around may be configured to contact the seal part 35.

In the configuration shown in FIG. 25, the “part covering the entire periphery of the peripheral edge of the outer surface of the seal portion 35 (corresponding to the“ second seal portion ”)” in the solid electrolyte membrane 40 is replaced with the solid electrolyte membrane 40. In addition, the solid electrolyte membrane 40 may be formed of a dense membrane 37 (corresponding to the “first seal portion”) having a different constituent material. The dense film 37 can be made of, for example, GDC = (Ce, Gd) O ₂ (gadolinium-doped ceria).

  In this case, in the portion covering the outer surface of the fuel electrode current collector 21 in the “gas seal portion”, the “gas seal portion” includes a solid electrolyte membrane 40 as a part of the power generation element portion, and a solid electrolyte membrane. A dense film 37 (corresponding to the “first seal portion”) made of a material different from that of the solid electrolyte film 40 while being connected to the solid electrolyte film 40, and a dense structure connected to the dense film 37 and different from the dense film 37 A seal part 35 made of a material (corresponding to the “second seal part”) and an interconnector 30 connected to the seal part 35 are configured. In this case, the dense membrane 37 and the interconnector 30 do not contact each other, and the solid electrolyte membrane 40 and the seal portion 35 do not contact each other.

  In the configuration shown in FIG. 25, the seal portion 35, the intermediate layer 38, and the interconnector 30 are embedded in the recess 21 b formed on the outer surface of the anode current collector 21, but as shown in FIG. 26. Only the seal portion 35 and the intermediate layer 38 may be embedded in the recess 21b. Alternatively, as shown in FIG. 27, the recess 21 b is not formed on the outer surface of the fuel electrode current collector 21, and the interconnector 30, the seal portion 35, and the intermediate layer 38 are formed on the main surface of the support substrate 10. May be.

  Similarly to the configuration shown in FIG. 25, in the configuration shown in FIGS. 26 and 27, the “gas seal portion” is the portion that covers the outer surface of the fuel electrode 20 (current collector 21) in the “gas seal portion”. , “A solid electrolyte membrane 40 as a part of the power generation element portion” and “a dense membrane 40 connected to the solid electrolyte membrane 40 and made of the same constituent material as the solid electrolyte membrane 40 or a dense membrane 37 made of a different constituent material. (Corresponding to the “first seal portion”) and “the seal portion 35 connected to the dense film 40 or 37 and made of a dense constituent material different from the dense film 40 or 37” (the “second seal portion”). And "interconnector 30 connected to seal portion 35".

  Similarly to the configuration shown in FIG. 25, in the configuration shown in FIGS. 26 and 27, when the “first seal portion” is the dense membrane 40 (= solid electrolyte membrane 40), the dense membrane 40 (= solid electrolyte membrane 40). ) And the interconnector 30 do not contact each other. When the “first seal portion” is the dense membrane 37 (≠ solid electrolyte membrane 40), the dense membrane 37 (≠ solid electrolyte membrane 40) and the interconnector 30 are not in contact with each other, and the solid electrolyte membrane 40 and the seal are sealed. The part 35 does not contact.

  In the above embodiment, only the intermediate layer 38 (only one layer) is interposed between the bottom surface of the recess 21 b formed on the outer surface of the anode current collector 21 and the bottom surface of the interconnector 30. However, as shown in FIG. 28, “second lanthanum chromite and Ni as main components are different from the intermediate layer 38 between the bottom surface of the recess 21 b and the bottom surface of the intermediate layer 38. Intermediate layer 39 ”may be interposed.

  In the present embodiment and the modifications shown in FIGS. 25 to 28, “the outer electrode is connected to the anode current collector 21 via the intermediate layer 38 among the outer surface, the bottom surface, and the side surface of the interconnector 30. Is common to the point that “only the bottom surface is in contact with the air electrode current collector film 70 among the outer surface, bottom surface, and side surfaces of the interconnector 30”. Yes.

  In the above embodiment, a plurality of recesses 12 are formed on each of the upper and lower surfaces of the flat support substrate 10 and a plurality of power generating element portions A are provided. As shown in FIG. A plurality of recesses 12 may be formed only on one side of the ten and a plurality of power generation element portions A may be provided. Moreover, in the said embodiment, although the support substrate 10 is exhibiting flat form, the support substrate may be exhibiting cylindrical shape.

  Further, in the above embodiment, the fuel electrode 20 is composed of two layers of the fuel electrode current collector 21 and the fuel electrode active portion 22, but the fuel electrode 20 is a single layer corresponding to the fuel electrode active portion 22. It may be configured.

  DESCRIPTION OF SYMBOLS 10 ... Support substrate, 11 ... Fuel gas flow path, 12 ... Recessed part, 20 ... Fuel electrode, 21 ... Fuel electrode current collecting part, 21a, 21b ... Recessed part, 22 ... Fuel electrode active part, 30 ... Interconnector, 35 ... Seal , 37 ... dense membrane, 38 ... intermediate layer, 40 ... solid electrolyte membrane, 50 ... reaction preventing membrane, 60 ... air electrode, 70 ... air electrode current collector membrane, A ... power generation element portion

Claims (4)

A support substrate having a gas flow path formed therein;
A plurality of power generating element portions each provided at a plurality of locations separated from each other on the surface of the support substrate, and a stack of a fuel electrode including at least a transition metal, a solid electrolyte membrane, and an air electrode;
One or a plurality of electrical connection portions that are respectively provided between the adjacent power generation element portions and electrically connect one fuel electrode and the other air electrode of the adjacent power generation element portions;
A gas seal portion made of a dense material for preventing mixing of the fuel gas supplied from the gas flow path to the fuel electrode and the gas containing oxygen supplied to the air electrode;
A fuel cell comprising:
Each of the electrical connection parts is composed of a first part made of a dense material mainly composed of lanthanum chromite and a second part made of a porous material and connected to the first part. , the power generated element one of the fuel electrode and connecting the second portion and electrically the portion adjacent the second portion, electrical and other air electrode and the first portion of the power generating element in which the adjacent It is connected to,
The first part of each electrical connection part is a part of the gas seal part,
The first portion of each electrical connection portion includes an outer surface, a bottom surface opposite to the outer surface, and a side surface,
The outer surface of the first portion of each electrical connection is in contact with the corresponding second portion of the electrical connection;
An intermediate layer comprising lanthanum chromite as a main component and having a higher porosity than the first portion of the electrical connection portion between the bottom surface of the first portion of each electrical connection portion and the corresponding fuel electrode. Is intervened ,
The element concentration of the transition metal in the region whose distance from the outer surface in the first portion of each electrical connection portion is 3 μm or less is 3 atm. % Fuel cell. The fuel cell according to claim 1, wherein
A fuel cell in which the porosity of the intermediate layer is 15 to 50% and the thickness of the intermediate layer is 3 to 50 μm. The fuel cell according to claim 1 or 2 ,
The gas seal portion includes a solid electrolyte membrane made of a dense material as a part of the power generation element portion, and a first dense material connected to the solid electrolyte membrane and made of the same or different dense material from the solid electrolyte membrane. A first seal portion, a second seal portion connected to the first seal portion and made of a dense material different from the first seal portion, and a first electrical connection portion connected to the second seal portion. A fuel cell configured to prevent contact between the first seal portion and the first portion of the electrical connection portion. The fuel cell according to claim 3 , wherein
First recesses having a bottom wall made of the material of the support substrate and a side wall made of the material of the support substrate are formed in the plurality of locations on the main surface of the support substrate, respectively.
In each of the first recesses, the corresponding fuel electrode of the power generation element unit is embedded,
Second recesses having a bottom wall made of the material of the fuel electrode and a side wall made of the material of the fuel electrode are formed on the outer surface of each buried fuel electrode,
In each of the second recesses, the corresponding first portion of the electrical connection portion and the corresponding second seal portion are embedded, respectively.
In each of the second recesses,
A first portion of the electrical connection portion is embedded in a central portion of the second recess,
The second seal portion is a peripheral portion located around the central portion of the second recess, and the entire periphery of the side wall of the second recess and the side surface of the first portion of the electrical connection portion. Buried in contact with the entire circumference of the
A central portion of the first portion of the electrical connection portion at the bottom surface is connected to the fuel electrode via the intermediate layer, and is positioned around the central portion of the bottom surface of the first portion of the electrical connection portion. The peripheral edge part is in contact with the second seal part,
A fuel cell, wherein the entire periphery of the outer peripheral surface of the second seal portion is covered with the first seal portion.

Images