JP2019046708A - Fuel battery cell stack - Google Patents

Abstract

To provide a fuel battery cell stack which can suppress the delamination of a cathode, even if a sealant is partially broken and a cross leak is caused.SOLUTION: A fuel battery cell stack 1 comprises: a fuel battery cell 2 including an anode 21, a solid electrolyte layer 22 and a cathode 24; a metal frame 3 for supporting a peripheral edge of the fuel battery cell 2; a sealant 4 for sealing between the peripheral edge of the fuel battery cell 2 and the frame 3; and a delamination-suppressing layer 5 in contact with a peripheral end 240 of the cathode 24. The cathode 24 has an oxide including an element which can be at least partially substituted with Cr. The delamination-suppressing layer 5 includes a Cr-containing oxide including Cr, or a precursor which turns into a Cr-containing oxide owing to power generation.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell stack.

  Conventionally, the outer periphery of a fuel cell comprising an anode, a solid electrolyte layer, and a cathode is supported by a metal frame, and the space between the outer periphery of the fuel cell and the frame is sealed with a sealing material A fuel cell stack is known. As a sealing material, a metal brazing material, a glass material, etc. are generally used.

  For example, Patent Document 1 discloses a solid oxide fuel cell in which a space between a surface of a solid electrolyte layer on the cathode side of a fuel cell and a stainless steel separator is sealed with a metal brazing material.

JP 2004-146129 A

  However, in sealing with a metal brazing material, hydrogen contained in the fuel gas penetrates into the metal brazing material and diffuses during long-term operation of the fuel cell stack, and oxygen contained in the oxidant gas is also contained in the metal brazing material Get in and diffuse. As a result, the brazing filler metal component, hydrogen, and oxygen react to generate voids inside the metal brazing filler metal. Therefore, the air tightness by the sealing material is reduced to cause cross leak, and the cathode is peeled off by the reduction of the cathode by the hydrogen leaked to the cathode side.

  In addition, sealing with a glass material has low bonding strength. Therefore, in sealing with a glass material, it is difficult to ensure a stable sealing property for a long-term stability against emergency stop of the fuel cell stack, an abnormal pressure difference between the cathode and the anode, and vibration and impact. Therefore, also in this case, the airtightness by the sealing material is lowered to cause the cross leak, and the cathode is peeled off by the reduction of the cathode by the hydrogen leaked to the cathode side.

  As described above, it is only possible to improve the sealing material itself against partial failure of the sealing material due to long-term operation of the fuel cell stack, emergency stop, abnormal pressure difference between the cathode and the anode, and vibration / shock. There are limits to ensuring air tightness.

  The present invention has been made in view of such problems, and it is an object of the present invention to provide a fuel cell stack capable of suppressing the separation of the cathode even when a part of the sealing material is broken and a cross leak occurs. It is

One embodiment of the present invention is a fuel cell (2) comprising an anode (21), a solid electrolyte layer (22) and a cathode (24).
A metal frame (3) for supporting the outer peripheral edge of the fuel cell;
A sealing material (4) for sealing between the outer peripheral edge of the fuel cell and the frame;
And a peeling suppression layer (5) in contact with the outer peripheral end (240) of the cathode,
The cathode has an oxide containing Cr and an element capable of at least partial substitution,
The peeling suppression layer is in the fuel cell stack (1) including a Cr-containing oxide containing Cr or a precursor that becomes the Cr-containing oxide by power generation.

  The fuel cell stack has the above configuration. Therefore, in the fuel cell stack, even if a part of the sealing material is broken due to long-term operation, emergency stop, abnormal pressure difference between the cathode and the anode, vibration / impact, etc., and the cross leak occurs, the cathode peels off. Can be suppressed. This is due to the following reasons. In the fuel cell stack, the separation suppression layer and the cathode are disposed in contact with each other at the outer peripheral end of the cathode. Therefore, during power generation of the fuel cell stack, Cr in the Cr-containing oxide contained in the exfoliation suppression layer is solid diffused from the interface between the exfoliation suppression layer and the cathode, and oxidation in the cathode occurs at the outer peripheral end of the cathode. The elements of the object and Cr partially substitute. As a result, the reduction resistance of the outer peripheral end of the cathode is increased. As a result, even if the fuel cell stack has a part of the sealing material broken due to long-term operation, emergency stop, abnormal pressure difference between the cathode and the anode, vibration / impact, etc. and cross leak occurs, Peeling can be suppressed.

  The reference numerals in parentheses described in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described later, and the technical scope of the present invention is limited. It is not a thing.

FIG. 2 is an explanatory view schematically showing a part of the fuel cell stack of Embodiment 1. It is explanatory drawing which showed typically a part of II-II arrow arrow cross section in FIG. FIG. 5 is an explanatory view schematically showing a part of a fuel cell stack of Embodiment 2 corresponding to FIG. 2; FIG. 10 is an explanatory view schematically showing a part of a fuel cell stack of Embodiment 3 corresponding to FIG. 1;

(Embodiment 1)
The fuel cell stack of Embodiment 1 will be described with reference to FIGS. 1 and 2. As illustrated in FIGS. 1 and 2, the fuel cell stack 1 of the present embodiment includes a fuel cell 2, a frame 3, a sealing material 4, and a peeling suppression layer 5. . This will be described in detail below.

  The fuel cell 2 is a solid electrolyte fuel cell having a solid electrolyte layer 22. A solid oxide ceramic or the like exhibiting oxygen ion conductivity can be used for the solid electrolyte constituting the solid electrolyte layer 22. A fuel cell using solid oxide ceramics as a solid electrolyte is referred to as a solid oxide fuel cell (SOFC).

  In the fuel cell stack 1, the fuel cell 2 includes an anode 21, a solid electrolyte layer 22 and a cathode 24. In the present embodiment, as illustrated in FIG. 2, an example in which the fuel cell 2 further includes an intermediate layer 23 between the solid electrolyte layer 22 and the cathode 24 is shown. The intermediate layer 23 is a layer mainly for suppressing the reaction between the solid electrolyte layer material and the cathode material. Specifically, the fuel cell 2 has a flat cell structure, and has a rectangular shape as viewed from the direction perpendicular to the cell surface. The anode 21, the solid electrolyte layer 22, the intermediate layer 23, and the cathode 24 are stacked in this order and bonded to one another. In addition, in FIG. 2, the fuel cell 2 of the anode support type | mold which makes the anode 21 which is an electrode function as a support body is illustrated. In the present embodiment, the cathode 24 is formed to have a smaller outer size than the solid electrolyte layer 22 and the intermediate layer 23. Therefore, in the fuel cell 2, the surface of the intermediate layer 23 on the cathode 24 side is exposed at the outer periphery of the cathode 24. When the fuel cell 2 does not have the intermediate layer 23, the surface of the solid electrolyte layer 22 is exposed around the cathode 24.

  In the fuel cell 2, the anode 21 may be composed of a single layer or may be composed of a plurality of layers. FIG. 2 shows an example in which the anode 21 is composed of a single layer. Specifically, when the anode 21 is formed of a plurality of layers, specifically, the anode 21 includes, for example, an active layer disposed on the solid electrolyte layer 22 side and a diffusion layer disposed on the opposite side to the solid electrolyte layer 22 side. And the like. The active layer is mainly a layer for enhancing the electrochemical reaction at the anode 21. The diffusion layer is a layer capable of diffusing the supplied fuel gas into the layer surface.

  As a material of the anode 21, for example, a mixture of a catalyst such as Ni, NiO and the like, and a solid electrolyte such as a zirconium oxide based oxide can be exemplified. As a zirconium oxide type oxide, yttria stabilized zirconia, scandia stabilized zirconia etc. can be illustrated, for example. Note that NiO is Ni in a reducing atmosphere at the time of power generation. In this embodiment, specifically, Ni or a mixture of NiO and yttria stabilized zirconia can be used as the material of the anode 21.

  The thickness of the anode 21 can be, for example, preferably 100 to 800 μm, more preferably 200 to 700 μm, from the viewpoint of gas diffusion, electric resistance, strength and the like.

  As a material of the solid electrolyte layer 22, the above-mentioned zirconium oxide-based oxides and the like can be suitably used from the viewpoint of being excellent in strength, thermal stability and the like. Yttria-stabilized zirconia is preferable as the material of the solid electrolyte layer 22 from the viewpoints of oxygen ion conductivity, mechanical stability, compatibility with other materials, and chemical stability from the oxidizing atmosphere to the reducing atmosphere, etc. is there.

  The thickness of the solid electrolyte layer 22 can be preferably 1 to 20 μm, more preferably 2 to 15 μm, and still more preferably 3 to 10 μm from the viewpoint of reduction of ohmic resistance and the like.

As a material of the intermediate layer 23, for example, CeO ₂ or CeO ₂ is doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho, etc. Examples of such a cerium oxide-based oxide such as a ceria-based solid solution can be given. These can be used alone or in combination of two or more. In the present embodiment, specifically, a ceria-based solid solution or the like doped with Gd can be used as the material of the intermediate layer 23

  The thickness of the intermediate layer 23 can be preferably 1 to 20 μm, more preferably 2 to 5 μm, from the viewpoints of reduction of ohmic resistance, suppression of element diffusion of the cathode 24 and the like.

  The cathode 24 contains an oxide containing Cr and an element which can be at least partially substituted. As the said oxide, electroconductive oxides, such as transition metal perovskite type oxide, etc. can be illustrated, for example. Specifically as said oxide, a lanthanum-strontium- cobalt-type oxide can be illustrated. Note that the lanthanum-strontium-cobalt-based oxide is an oxide containing at least La, Sr, and Co as constituent elements. According to this configuration, the effect of suppressing peeling of the cathode 24 at the time of occurrence of cross leak can be made reliable by the action of the peeling suppression layer described later.

As the lanthanum-strontium-cobalt-based oxide, specifically, La _x Sr _1-x CoO ₃ (wherein 0 <x <1, preferably 0.1 ≦ x ≦ 0.9, more preferably 0.2 <= x <= 0.8) etc. can be illustrated. As the lanthanum-strontium-cobalt-based oxide, two or more kinds of compounds different in the value of x can be used in combination. In the lanthanum-strontium-cobalt-based oxide, Co can be given as an element which can be at least partially substituted for Cr.

The cathode 24 can contain a solid electrolyte in addition to the above oxides. As the solid electrolyte, for example, CeO ₂ or ceria in which CeO ₂ is doped with one or more elements selected from Gd, Sm, Y, La, Nd, Yb, Ca, and Ho, etc. A cerium oxide-based oxide such as a solid solution can be exemplified. These can be used alone or in combination of two or more.

  The cathode 24 can also include an oxide in which a part of the element capable of at least partially substituting Cr is substituted by Cr. According to this configuration, the improvement of the reduction resistance at the outer peripheral end portion 240 of the cathode 24 becomes reliable, and the peeling suppression of the cathode 24 can be made reliable.

  In the fuel cell stack 1, when the cathode 24 includes, for example, a lanthanum-strontium-cobalt-based oxide, the lanthanum-strontium-cobalt-based oxide is formed at the outer peripheral end 240 of the cathode 24. It is possible to include an oxide in which part of the element is substituted by Cr. That is, in the fuel cell stack 1, the oxide in which a part of the elements constituting the lanthanum-strontium-cobalt-based oxide is substituted with Cr is unevenly distributed in the outer peripheral end 240 of the cathode 24. Can. According to this configuration, the improvement of the reduction resistance at the outer peripheral end portion 240 of the cathode 24 becomes more reliable, and the peeling suppression of the cathode 24 can be made more reliable.

  The thickness of the cathode 24 can be preferably 20 to 100 μm, more preferably 30 to 80 μm, from the viewpoint of gas diffusivity, electrode reaction resistance, current collecting property, and the like. Specifically, in the present embodiment, the thickness of the cathode 24 can be 50 μm.

  In the fuel cell stack 1, the frame 3 is made of metal and supports at least the outer peripheral edge of the fuel cell 2. In the present embodiment, the fuel cell stack 1 has a laminated structure (not shown) in which a plurality of fuel cells 2 whose outer peripheral edge is supported by the frame 3 are stacked via a metallic separator (not shown). doing. In the present embodiment, as illustrated in FIG. 2, the outer peripheral edge of the fuel cell 2 on the side opposite to the side supported by the frame 3 is provided so that the fuel cell 2 supported by the frame 3 is not detached. The example fixed by the metal retainer 6 is shown. In FIG. 1, the retainer 6 is omitted for the sake of convenience. Further, in the present embodiment, the frame 3 is formed in a frame shape. Although not shown, the frame 3 may have a cell support surface having a plurality of through holes, and may support the surface of the anode 21 of the fuel cell 2 at the cell support surface. Also by this configuration, the frame 3 can support the outer peripheral edge of the fuel cell 2.

  The fuel cell stack 1 can be configured such that oxidant gas O is supplied along the in-plane direction of the cathode 24 and fuel gas (not shown) is supplied along the in-plane direction of the anode 21. . Specifically, on the cathode 24 side, the gap provided between the frame 3 and the separator can be an oxidant gas flow path (not shown) through which the oxidant gas O flows. Further, on the anode 21 side, the gap provided between the frame 3 and the separator can be a fuel gas flow path (not shown) through which the fuel gas flows. Further, in the fuel cell stack 1, the cathode side current collector (not shown) may be disposed in the oxidant gas flow channel, and the cathode side current collector may be configured to be in contact with the cathode 24 and the separator. In addition, an anode side current collector (not shown) may be disposed in the fuel gas flow channel, and the anode side current collector may be configured to be in contact with the anode 21 and the separator. In addition, as oxidant gas O, air, oxygen gas, etc. can be illustrated, for example. As fuel gas, hydrogen gas, hydrogen-containing gas, etc. can be illustrated, for example.

In the fuel cell stack 1, the metal constituting the frame 3 can be made of an oxidation resistant metal material. According to this configuration, even when the frame 3 is placed under the high temperature environment at the time of power generation of the fuel cell stack 1, the shape can be maintained. Therefore, according to this configuration, it is possible to obtain the fuel cell stack 1 capable of improving the battery reliability in a high temperature environment. Note that the oxidation resistant metal is a metal whose contact resistance in an oxidizing atmosphere at 800 ° C. changes to 50 mΩ · cm ² or less for up to 10,000 hours. Also, the contact resistance is a value measured by a four-terminal measurement method. Specific examples of the oxidation resistant metal include ferritic stainless steel, heat resistant Cr alloy, heat resistant NiCr alloy, austenitic stainless steel, and the like.

In the fuel cell stack 1, the linear thermal expansion coefficient of the metal constituting the frame 3 can be 16 × 10 ⁻⁶ / K or less. According to this configuration, even when the frame 3 is placed under the high temperature environment at the time of power generation of the fuel cell stack 1, the shape can be maintained. Therefore, according to this configuration, it is possible to obtain the fuel cell stack 1 capable of improving the battery reliability in a high temperature environment.

The above-mentioned coefficient of linear thermal expansion is preferably less than 16 × 10 ⁻⁶ / K, more preferably 14 × 10 ⁻⁶ / K or less, still more preferably 13 or less, from the viewpoint of securing the above-mentioned effects, etc. It can be less than or equal to 10 ^-6 / K. In addition, the said linear thermal expansion coefficient is a value in the range of 0 degreeC-800 degreeC. Moreover, the said linear thermal expansion coefficient is fundamentally measured based on JISZ 2285: 2003 "the measuring method of the linear thermal expansion coefficient of a metal material." Similarly, the metal constituting the separator and the retainer 6 described above can be made of an oxidation resistant metal material, and the linear thermal expansion coefficient of each metal is 16 × 10 ^-6 / K or less, respectively. can do.

  In the fuel cell stack 1, the sealing material 4 seals between the outer peripheral edge of the fuel cell 2 and the frame 3. In the case where the fuel cell stack 1 includes the retainer 6, the sealing material 4 may seal between the outer peripheral edge of the fuel cell 2 and the retainer 6 as illustrated in FIG. 2. . According to this configuration, since the sealing distance by the sealing material 4 becomes long, it is advantageous for suppressing the cross leak by the sealing material 4 itself. As a material of the sealing material 4, a metal brazing material, a glass material, etc. can be illustrated, for example.

  In the fuel cell stack 1, the separation suppressing layer 5 is in contact with the outer peripheral end 240 of the cathode 24. Specifically, in the present embodiment, the exfoliation suppression layer 5 is formed on the surface of the intermediate layer 23 exposed to the cathode 24 side at the outer periphery of the cathode 24 as illustrated in FIG. 2. In the case where the fuel cell 2 does not have the intermediate layer 23, the separation suppressing layer 5 can be formed on the surface of the solid electrolyte layer 22 exposed on the cathode 24 side around the cathode 24.

  Here, the peeling suppression layer 5 has a Cr-containing oxide containing Cr or a precursor that becomes a Cr-containing oxide by power generation.

  Specifically, a lanthanum-chromium-based oxide can be suitably used as the Cr-containing oxide. Note that the lanthanum-chromium-based oxide is an oxide having at least La and Cr as constituent elements. A lanthanum-chromium-based oxide is not easily oxidized in an oxidizing atmosphere and is not easily reduced in a reducing atmosphere, and therefore, can exhibit electron conductivity in any atmosphere. Therefore, according to this configuration, it is possible to obtain the peeling suppression effect of the cathode 24 due to the improvement of the reduction resistance of the cathode 24 while making the peeling suppression layer 5 function as a part of the electrode (cathode 24). Therefore, according to the above configuration, the fuel cell stack 1 is obtained which is advantageous for securing the power generation capacity for a long time.

Specifically, La _x A _1-x B _y Cr _1-y O ₃ can be exemplified as the lanthanum-chromium-based oxide. However, at least one selected from the group consisting of 0 <x ≦ 1, 0 ≦ y <1, A = Sr, Ca, and Ba, B = Mg, Al, Mn, Fe, Ti, Zn, Co, It is at least one selected from the group consisting of Ni, Cu, V, Nb, Ta, W, and Mo. According to this configuration, a perovskite-type crystal structure can be formed by arbitrarily combining the elements A and B, and the reduction resistance of the cathode 24 can be improved and the electron conductivity of the separation suppressing layer 5 can be ensured. It becomes easy to do. Therefore, according to the above configuration, the above-described effect can be made reliable.

In La _x A _1-x B _y Cr _1-y O ₃ , preferably 0.1 ≦ x ≦ 1, 0 ≦ y ≦ 0.9, more preferably 0.2 ≦ x ≦ 1, 0 ≦ y It can be set to ≦ 0.8. According to this configuration, generation of a by-product and the like after power generation of the fuel cell stack 1 can be easily suppressed, which is advantageous for securing the electron conductivity of the separation suppressing layer 5.

  Specifically, the precursor that becomes a Cr-containing oxide by power generation is a substance that is converted to a Cr-containing oxide by the temperature (heat) at the time of power generation. Such precursors include not only single substances but also mixtures of multiple substances. The precursors can be used alone or in combination of two or more.

  The fuel cell stack 1 has the above configuration. Therefore, in the fuel cell stack 1, even if a part of the sealing material is broken due to long-term operation, emergency stop, differential pressure abnormality between the cathode 24 / anode 21, vibration, impact, etc., and the cross leak occurs, the cathode Peeling of 24 can be suppressed. This is due to the following reasons. In the fuel cell stack 1, the exfoliation suppression layer 5 and the cathode 24 are disposed in contact with each other at the outer peripheral end 240 of the cathode 24. Therefore, during power generation of the fuel cell stack 1, Cr in the Cr-containing oxide contained in the exfoliation suppression layer 5 solid diffuses from the interface between the exfoliation suppression layer 5 and the cathode 24, and the outer peripheral end 240 of the cathode 24 , And the element of the oxide in the cathode 24 are partially substituted with Cr. As a result, the reduction resistance of the outer peripheral end 240 of the cathode 24 is increased. Thereby, in the fuel cell stack 1, even if a part of the sealing material 4 is broken due to long-term operation, emergency stop, abnormal pressure difference between the cathode 24 / anode 21, vibration / impact, etc. and cross leak occurs. And peeling of the cathode 24 can be suppressed.

  In the fuel cell stack 1, specifically, the exfoliation suppression layer 5 can be configured to be in contact with the outer peripheral end face 241 of the cathode 24 as illustrated in FIG. 2. When the cross leak occurs in the case where the peeling suppression layer 5 is not present, the hydrogen which has entered the cathode 24 first touches the outer peripheral end face 241 of the cathode 24. Then, when the outer peripheral end portion 240 of the cathode 24 is reduced by hydrogen, the cathode 24 is easily peeled off from this portion. Therefore, according to the above-described configuration, the reduction resistance at the outer peripheral end portion 240 of the cathode 24 is surely improved by partial replacement of Cr diffused in the solid state from the peeling suppression layer 5 and the element included in the oxide in the cathode 24. It can be Therefore, according to the above configuration, even when cross leak occurs, peeling of the cathode 24 can be easily suppressed.

  Further, in the fuel cell stack 1, specifically, the exfoliation suppression layer 5 can be in contact with the entire periphery of the outer peripheral end portion 240 of the cathode 24 as illustrated in FIG. 1. According to this configuration, the reduction resistance of the outer peripheral end portion 240 of the cathode 24 is increased over the entire circumference. Therefore, according to this configuration, even when cross leak occurs, peeling of the cathode 24 can be easily suppressed along the entire periphery of the outer peripheral end portion 240 of the cathode 24.

  Specifically, the thickness of the peeling suppression layer 5 can be equal to or greater than the thickness of the cathode 24. According to this configuration, securing of the interface between the peeling suppression layer 5 and the cathode 24 is ensured, and the above-described effects can be ensured.

  The thickness of the peeling suppression layer 5 can be preferably 20 to 120 μm, more preferably 30 to 100 μm, from the viewpoint of improving the reduction resistance of the cathode 24 and the like. Specifically, in the present embodiment, the thickness of the peeling suppression layer 5 can be 70 μm.

Second Embodiment
The fuel cell stack according to Embodiment 2 will be described with reference to FIG. In addition, the code | symbol same as the code | symbol used in already-appeared embodiment among the code | symbols used after Embodiment 2 represents the component similar to the thing in already-appeared embodiment etc., unless shown otherwise.

  As illustrated in FIG. 3, in the fuel cell stack 1 of the present embodiment, the separation suppressing layer 5 has a stacked unit 50 stacked on the cathode 24.

  According to this configuration, the peeling suppression layer 5 can not only be in contact with the outer peripheral end face 241 of the cathode 24, but can also be in contact with the surface 242 of the outer peripheral end 240 of the cathode 24 in the laminated portion 50. Therefore, according to this configuration, it is possible to cause solid diffusion of Cr also from the stacked portion 50 with respect to the outer peripheral end portion 240 of the cathode 24, and partial substitution of Cr with the oxide element in the cathode 24 can be achieved. It can be promoted. Therefore, according to this configuration, it is possible to obtain the fuel cell stack 1 in which the reduction resistance of the cathode 24 can be easily improved. The other configurations and effects are the same as in the first embodiment.

(Embodiment 3)
The fuel cell stack according to Embodiment 3 will be described with reference to FIG. As illustrated in FIG. 4, in the fuel cell stack 1 of the present embodiment, the exfoliation suppression layer 5 excludes the end portion region on the outlet side of the oxidant gas O in the outer peripheral end portion 240 of the cathode 24. It touches the remaining end area.

  Specifically, in the present embodiment, the cathode 24 has a square shape. Therefore, the outer peripheral end 240 of the cathode 24 can be divided into four end areas 240a, 240b, 240c and 240d corresponding to the four sides of the square. In the present embodiment, an oxidant gas inlet (not shown) is disposed on one of the four end regions 240 a, 240 b, 240 c, and 240 d at the outer peripheral end 240 of the cathode 24. . On the other hand, out of the four end areas 240a, 240b, 240c, and 240d at the outer peripheral end 240 of the 24, the outlet (not shown) of the oxidant gas O on the end area 240d side facing the one end area 240a. Is placed. Therefore, in the present embodiment, the exfoliation suppression layer 5 is one end region 240 d of the outlet side of the oxidant gas O among the four end regions 240 a, 240 b, 240 c and 240 d in the outer peripheral end 240 of the cathode 24. Are in contact with the remaining three end regions 240a, 240b, 240c except for.

  The end region 240 d on the outlet side of the oxidant gas O at the outer peripheral end 240 of the cathode 24 is less susceptible to hydrogen due to cross leak than the end region 240 a on the inlet side of the oxidant gas O. Therefore, when the exfoliation suppression layer 5 is not in contact with the end region 240d on the outlet side of the oxidant gas O at the outer circumferential end 240 of the cathode 24 (a part of the exfoliation suppression layer 5 is on the outer circumferential end 240 of the cathode 24). Even in the case where they are not in contact with each other, peeling of the cathode 24 can be sufficiently suppressed compared to the case where the peeling suppression layer 5 is not present at all. Therefore, according to the above configuration, the amount of use of the exfoliation suppression layer 5 can be reduced as compared to the first embodiment, so that the fuel cell stack is advantageous in reducing material cost while suppressing exfoliation of the cathode 24. 1 is obtained. The other configurations and effects are the same as in the first embodiment.

(Experimental example)
-Sample 1-
NiO powder (average particle size: 0.5 μm), yttria stabilized zirconia (hereinafter, 8YSZ) powder containing 8 mol% Y ₂ O ₃ (average particle size: 0.2 μm), carbon (pore forming agent), A slurry was prepared by mixing polyvinyl butyral, isoamyl acetate and 1-butanol in a ball mill. The mass ratio of NiO powder to 8YSZ powder is 65:35. The above-described slurry was applied in a layer form on a resin sheet using a doctor blade method, and dried, and then the resin sheet was peeled off to prepare a 100-μm-thick sheet for anode formation. The above average particle diameter is the particle diameter (diameter) d50 when the volume-based cumulative frequency distribution measured by the laser diffraction / scattering method indicates 50% (the same applies hereinafter).

  A slurry was prepared by mixing 8YSZ powder (average particle size: 0.2 μm), polyvinyl butyral, isoamyl acetate and 1-butanol in a ball mill. Thereafter, in the same manner as the preparation of the sheet for forming an anode, a sheet for forming a solid electrolyte layer having a thickness of 5.0 μm was prepared.

A slurry was prepared by mixing 10 mol% Gd-doped CeO ₂ (hereinafter, 10 GDC) powder (average particle size: 0.3 μm), polyvinyl butyral, isoamyl acetate, 2-butanol and ethanol in a ball mill. Prepared. Thereafter, in the same manner as the preparation of the sheet for forming an anode, a sheet for forming an intermediate layer having a thickness of 4.0 μm was prepared.

  The sheet for forming an anode, the sheet for forming a solid electrolyte layer, and the sheet for forming an intermediate layer were laminated in this order and pressure-bonded. In addition, the WIP molding method was used for pressure bonding. At this time, the WIP molding conditions were a temperature of 85 ° C., a pressure of 50 MPa, and a pressure time of 10 minutes. The resulting crimped body was degreased.

  A sintered body in which an anode, a solid electrolyte layer, and an intermediate layer were laminated in this order was obtained by collectively firing the pressure-bonded body in an air atmosphere at 1350 ° C. for 2 hours.

La _0.6 Sr _0.4 CoO ₃ powder (average particle size: 0.6 .mu.m) and, ethylcellulose, by kneading the terpineol by a three-roll mill to prepare a cathode-forming paste.

  A cathode-forming paste was applied by screen printing on the surface of the intermediate layer in the above sintered body, dried, and then baked (baked) in an air atmosphere at 900 ° C. for 2 hours to form a layered cathode (50 μm) . At this time, the outer shape of the cathode was smaller than the outer shape of the anode. The thickness of the cathode can be selected preferably in the range of 20 to 100 μm, more preferably 30 to 80 μm. Moreover, the calcination temperature at the time of cathode formation can be adjusted within the range of 700 degreeC-900 degreeC. Further, the baking time at the time of forming the cathode can be appropriately adjusted according to the thickness of the cathode, the amount of the binder in the paste for forming the cathode, and the like.

A paste for formation of a peeling suppression layer was prepared by kneading La _0.8 Sr _0.2 CrO ₃ powder (average particle diameter: 0.5 μm), ethyl cellulose and terpineol with a three-roll.

  As shown in FIG. 1, the paste for forming a peeling suppression layer is printed by pattern printing so as to be in contact with all of the outer peripheral end face of the cathode, dried, and then baked (baked) at 850 ° C. for 2 hours in the air atmosphere. A suppression layer (60 μm) was formed. In addition, the thickness of a peeling suppression layer can be preferably selected from the range of 20-120 micrometers, more preferably 30-100 micrometers. Moreover, the calcination temperature at the time of peeling suppression layer formation can be adjusted within the range of 700 degreeC-900 degreeC. Moreover, the baking time at the time of formation of a peeling suppression layer can be suitably adjusted according to the thickness of a peeling suppression layer, the quantity of the binder component in the paste for peeling suppression layer formation, etc. Thus, a flat fuel cell having a separation suppressing layer was obtained.

  As shown in FIGS. 1 and 2, the fuel cell was assembled to a frame made of ferritic stainless steel. Under the present circumstances, the metal brazing material was used for the sealing material which seals between the outer periphery of a fuel cell and flame | frame. Further, a retainer made of a ferritic stainless steel was attached to the outer peripheral edge of the fuel cell assembled to the frame. At this time, the same metal brazing material as described above was used as a sealing material for sealing between the outer peripheral edge of the fuel cell and the retainer. Thus, a framed fuel cell was obtained. Hereinafter, this is referred to as sample 1. A fuel cell stack can be configured by stacking a plurality of framed fuel cells with a separator interposed therebetween.

-Sample 2-
In the preparation of Sample 1, the La _0.8 Sr _0.2 CrO ₃ powder in the peeling suppression layer forming paste was changed to a La _0.9 Sr _0.1 CrO ₃ powder, and the peeling suppression layer forming paste was used as a cathode. The pattern printing is performed so as to partially overlap the surface of the outer peripheral edge portion, as shown in FIG. 3, in the same manner except that the peeling suppression layer is configured to have a laminated portion laminated on the cathode, A framed fuel cell of sample 2 was produced. In the sample 2, the peeling suppression layer is in contact with both the outer peripheral end face of the cathode and the outer peripheral end surface.

-Samples 3 to 14-
In the preparation of sample 1, the La _0.8 Sr _0.2 CrO ₃ powder in the paste for forming a peeling suppression layer was changed to a La _x A _1-x B _y Cr _1-y O ₃ powder shown in Table 1 described later A framed fuel cell of Samples 3 to 14 was produced in the same manner as in Example 1 except for the above.

-Sample 15-
In preparation of sample 1, as shown in FIG. 4, the exfoliation suppression layer forming paste is in contact with the remaining end face region excluding the end face region on the outlet side of the oxidant gas in the outer peripheral end of the cathode. A framed fuel cell of Sample 15 was produced in the same manner except that the pattern was printed.

-Sample 1C-
A framed fuel cell of Sample 1C was produced in the same manner as in the production of Sample 1 except that the exfoliation suppression layer was not formed.

-Sample 2C-
The same as in the preparation of Sample 1, except that the La _0.6 Sr _0.4 CoO ₃ powder in the paste for forming a cathode was changed to the La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder. A framed fuel cell of sample 2C was produced.

-Sample 3C-
A framed fuel of sample 3C was prepared in the same manner as in sample 1 except that the La _0.6 Sr _0.4 CoO ₃ powder in the paste for forming a cathode was changed to a Sm _0.5 Sr _0.5 CoO ₃ powder. A battery cell was produced.

-Evaluation test-
Assemble each sample into a single-layer stack shape, and supply 0.5 L / min of hydrogen gas from the outside to the anode side and 0.2 L / min of air to the cathode side at 500 ° C. While holding for 15 minutes. In addition, the said environment simulates the environment where differential pressure becomes anode> cathode at low temperature which sealing of cell outer periphery is not completed. After the above holding, the temperature was lowered and peeling of the cathode in each sample was visually confirmed.

  Table 1 summarizes the detailed configuration of each sample and the results of the evaluation test.

  According to Table 1, the reduction resistance at the outer peripheral end of the cathode is improved by arranging the peeling suppression layer having a Cr-containing oxide so as to be in contact with the cathode at the outer peripheral end of the cathode, and the cathode is peeled off. It has been confirmed that it can be suppressed.

  The present invention is not limited to the above embodiments and experimental examples, and various modifications can be made without departing from the scope of the invention. Moreover, each structure shown by each embodiment and each experiment example can each be combined arbitrarily. For example, the configuration of the second embodiment and the configuration of the third embodiment can be combined.

DESCRIPTION OF SYMBOLS 1 fuel cell cell stack 2 fuel cell 21 anode 22 solid electrolyte layer 24 cathode 240 outer peripheral end 3 frame 4 sealing material 5 peeling suppression layer

Claims (11)

A fuel cell (2) comprising an anode (21), a solid electrolyte layer (22) and a cathode (24);
A metal frame (3) for supporting the outer peripheral edge of the fuel cell;
A sealing material (4) for sealing between the outer peripheral edge of the fuel cell and the frame;
And a peeling suppression layer (5) in contact with the outer peripheral end (240) of the cathode,
The cathode has an oxide containing Cr and an element capable of at least partial substitution,
The fuel cell stack (1), wherein the peeling suppression layer has a Cr-containing oxide containing Cr or a precursor that becomes the Cr-containing oxide by power generation.   The fuel cell stack according to claim 1, wherein the Cr-containing oxide is a lanthanum-chromium-based oxide. The lanthanum-chromium-based oxide is a group consisting of La _x A _1-x B _y Cr _1-y O ₃ , provided that 0 <x ≦ 1, 0 ≦ y <1, A = Sr, Ca, and Ba. At least one selected from the group consisting of B = Mg, Al, Mn, Fe, Ti, Zn, Co, Ni, Cu, V, Nb, Ta, W, and Mo The fuel cell stack according to claim 1 or 2.   The fuel cell stack according to any one of claims 1 to 3, wherein the cathode has an oxide in which a part of the element is substituted by Cr.   The fuel cell stack according to any one of claims 1 to 4, wherein the oxide containing Cr and an element capable of at least partial substitution in the cathode is a lanthanum-strontium-cobalt-based oxide.   The fuel cell stack according to any one of claims 1 to 5, wherein the separation suppressing layer is in contact with an outer peripheral end face (241) of the cathode.   The fuel cell stack according to claim 6, wherein the separation suppressing layer has a stacked portion (50) stacked on the cathode.   The fuel cell stack according to any one of claims 1 to 7, wherein the separation suppressing layer is in contact with the entire periphery of the outer peripheral end of the cathode.   The peeling suppression layer is in contact with the remaining end area (240a, 240b, 240c) of the outer peripheral end of the cathode except the end area (240d) on the outlet side of the oxidant gas. The fuel cell stack according to any one of Items 1 to 7.   The fuel cell stack according to any one of claims 1 to 9, wherein the metal is made of an oxidation resistant metal material. The fuel cell stack according to any one of claims 1 to 10, wherein the linear thermal expansion coefficient of the metal is 16 × 10 ^-6 / K or less.

Images