JP7006038B2 - Fuel cell cell stack - Google Patents

Description

The present invention relates to a fuel cell cell stack.

Conventionally, the outer peripheral edge of a fuel cell having an anode, a solid electrolyte layer, and a cathode is supported by a metal frame, and the outer peripheral edge of the fuel cell and the frame are sealed with a sealing material. Fuel cell cell stacks are known. As the sealing material, a metal brazing material, a glass material, or the like is generally used.

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

Japanese Unexamined Patent Publication No. 2004-146129

However, in the encapsulation with a metal brazing material, hydrogen contained in the fuel gas enters and diffuses in the metal brazing material during long-term operation of the fuel cell stack, and oxygen contained in the oxidant gas enters the metal brazing material. It gets in and spreads. As a result, the brazing filler metal component, hydrogen, and oxygen react to generate voids inside the metal brazing filler metal. Therefore, the airtightness of the sealing material is lowered, cross leakage occurs, and the cathode is reduced by the hydrogen leaked to the cathode side, so that the cathode is peeled off.

Further, the sealing with the glass material has a low bonding strength. Therefore, in the case of sealing with a glass material, it is difficult to ensure stable sealing performance over a long period of time against an emergency stop of the fuel cell stack, an abnormality in the differential pressure between the cathode and the anode, and vibration / impact. Therefore, in this case as well, the airtightness of the encapsulant is reduced, cross-leakage occurs, and the cathode is reduced by the hydrogen leaking to the cathode side, so that the cathode is peeled off.

In this way, only to improve the encapsulant itself against long-term operation of the fuel cell stack, emergency stop, abnormal pressure difference between cathode / anode, partial destruction of encapsulant due to vibration / impact, etc. There is a limit to ensuring airtightness.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell stack capable of suppressing the peeling of the cathode even when a part of the encapsulant is broken and a cross leak occurs. It is something to do.

One aspect 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) that supports the outer peripheral edge of the fuel cell and
A sealing material (4) that seals between the outer peripheral edge of the fuel cell and the frame, and
It has a peeling suppression layer (5) in contact with the outer peripheral end portion (240) of the cathode, and has.
The cathode is composed of an oxide containing at least a partially replaceable element with Cr, or an oxide containing an element at least partially replaceable with Cr, and a solid electrolyte .
The peeling suppression layer has a Cr-containing oxide containing Cr or a precursor that becomes the Cr-containing oxide by power generation .
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 By Cr _1-y O ₃ , _but 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. It is in the fuel cell stack (1).

The fuel cell stack has the above configuration. Therefore, in the above fuel cell stack, even if a part of the sealing material is destroyed due to long-term operation, emergency stop, abnormal pressure difference between cathode / anode, vibration / impact, etc., and cross leak occurs, the cathode is peeled off. Can be suppressed. This is due to the following reasons. In the fuel cell stack, the peeling suppression layer and the cathode are arranged 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 peeling suppression layer diffuses solidly from the interface between the peeling suppression layer and the cathode, and oxidation in the cathode is performed at the outer peripheral end portion of the cathode. Partially replaces the element of the object with Cr. As a result, the reduction resistance of the outer peripheral end of the cathode is increased. As a result, in the fuel cell stack, even if a part of the encapsulant is destroyed due to long-term operation, emergency stop, abnormal pressure difference between cathode / anode, vibration / impact, etc., and cross leak occurs, the cathode Peeling can be suppressed.

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

It is explanatory drawing which shows a part of the fuel cell stack of Embodiment 1 schematically. It is explanatory drawing which shows a part of the cross section in line II-II in FIG. 1 schematically. It is explanatory drawing which shows a part of the fuel cell stack of Embodiment 2 schematically corresponding to FIG. It is explanatory drawing which shows a part of the fuel cell stack of Embodiment 3 schematically corresponding to FIG. 1.

(Embodiment 1)
The fuel cell stack of the first embodiment 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 has a fuel cell 2, a frame 3, a sealing material 4, and a peeling suppressing layer 5. .. This will be explained in detail below.

The fuel cell 2 is a solid electrolyte type fuel cell having a solid electrolyte layer 22. As the solid electrolyte constituting the solid electrolyte layer 22, solid oxide ceramics or the like exhibiting oxygen ion conductivity can be used. A fuel cell using solid oxide ceramics as a solid electrolyte is called 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 this embodiment, as illustrated in FIG. 2, an example is shown in which the fuel cell 2 further includes an intermediate layer 23 between the solid electrolyte layer 22 and the cathode 24. The intermediate layer 23 is mainly a layer for suppressing the reaction between the solid electrolyte layer material and the cathode material. Specifically, the fuel cell 2 has a flat plate-shaped battery structure, and has a rectangular shape when viewed from a direction perpendicular to the cell surface. The anode 21, the solid electrolyte layer 22, the intermediate layer 23, and the cathode 24 are laminated in this order and are bonded to each other. Note that FIG. 2 illustrates an anode-supported fuel cell 2 in which the anode 21 as an electrode functions as a support. In the present embodiment, the cathode 24 is formed to have a smaller outer shape 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 on 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 on the outer periphery of 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. When the anode 21 is composed of a plurality of layers, the anode 21 specifically includes, for example, an active layer arranged on the solid electrolyte layer 22 side and a diffusion layer arranged on the side opposite to the solid electrolyte layer 22 side. It can be configured to include. The active layer is mainly a layer for enhancing the electrochemical reaction at the anode 21. Further, the diffusion layer is a layer capable of diffusing the supplied fuel gas into the layer surface.

Examples of the material of the anode 21 include a mixture of a catalyst such as Ni and NiO and a solid electrolyte such as a zirconium oxide oxide. Examples of the zirconium oxide-based oxide include yttria-stabilized zirconia and scandia-stabilized zirconia. NiO becomes Ni in the reducing atmosphere at the time of power generation. In the present embodiment, as the material of the anode 21, specifically, a mixture of Ni or NiO and yttria-stabilized zirconia can be used.

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, electrical resistance, strength and the like.

As the material of the solid electrolyte layer 22, the above-mentioned zirconium oxide-based oxide or the like can be preferably used from the viewpoint of excellent strength and thermal stability. As the material of the solid electrolyte layer 22, yttria-stabilized zirconia is preferable from the viewpoints of oxygen ion conductivity, mechanical stability, compatibility with other materials, and chemical stability from an oxidizing atmosphere to a reducing atmosphere. be.

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

As the 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. Examples thereof include cerium oxide-based oxides such as the ceria-based solid solution. These can be used alone or in combination of two or more. In the present embodiment, as the material of the intermediate layer 23, specifically, a Gd-doped ceria-based solid solution or the like can be used.

The thickness of the intermediate layer 23 can be preferably 1 to 20 μm, more preferably 2 to 5 μm, from the viewpoint of reducing ohmic resistance and suppressing element diffusion of the cathode 24.

The cathode 24 contains an oxide containing an element that is at least partially substitutable with Cr. Examples of the oxide include conductive oxides such as transition metal perovskite-type oxides. Specific examples of the oxide include lanthanum-strontium-cobalt oxide. The lanthanum-strontium-cobalt oxide is an oxide containing at least La, Sr, and Co as constituent elements. According to this configuration, the effect of suppressing the peeling of the cathode 24 when a cross leak occurs can be ensured by the action of the peeling suppressing layer described later.

Specific examples of the lanthanum-strontium-cobalt oxide include La _x Sr _1-x CoO ₃ (however, 0 <x <1, preferably 0.1 ≦ x ≦ 0.9, more preferably. 0.2 ≦ x ≦ 0.8) and the like can be exemplified. As the lanthanum-strontium-cobalt oxide, two or more kinds having different x values can be used in combination. In the lanthanum-strontium-cobalt oxide, Co can be mentioned as an element that can be at least partially substituted with Cr.

The cathode 24 may contain a solid electrolyte in addition to the above oxides. Examples of the solid electrolyte include 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. Examples thereof include cerium oxide-based oxides such as system solid solutions. These can be used alone or in combination of two or more.

In the fuel cell stack 1, when the cathode 24 is composed of, for example, a lanthanum-strontium-cobalt oxide, the lanthanum-strontium-cobalt oxide is formed on the outer peripheral end portion 240 of the cathode 24. It can contain an oxide in which a part of the element is substituted with Cr. That is, in the fuel cell stack 1, the oxide in which a part of the elements constituting the lanthanum-strontium-cobalt oxide is replaced with Cr is unevenly distributed at the outer peripheral end portion 240 of the cathode 24. Can be done. 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 collection, and the like. In the present embodiment, the thickness of the cathode 24 can be specifically 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 cell 2 whose outer peripheral edge is supported by a frame 3 are laminated via a metal separator (not shown). is doing. In this embodiment, as illustrated in FIG. 2, the outer peripheral edge of the fuel cell 2 on the side opposite to the support side of the frame 3 is provided so that the fuel cell 2 supported by the frame 3 does not come off. An example of being fixed by a metal retainer 6 is shown. In FIG. 1, the retainer 6 is omitted for convenience. Further, in the present embodiment, the frame 3 is formed in a frame shape. Although not shown, the frame 3 has a cell support surface having a plurality of through holes, and the cell support surface may be configured to support the surface of the anode 21 in the fuel cell 2. With this configuration as well, the frame 3 can support the outer peripheral edge of the fuel cell 2.

The fuel cell stack 1 can be configured such that the oxidant gas O is supplied along the in-plane direction of the cathode 24 and the 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, a cathode-side current collector (not shown) can be arranged in the oxidant gas flow path so that the cathode-side current collector is in contact with the cathode 24 and the separator. Further, an anode-side current collector (not shown) can be arranged in the fuel gas flow path so that the anode-side current collector comes into contact with the anode 21 and the separator. As the oxidant gas O, for example, air, oxygen gas, or the like can be exemplified. Examples of the fuel gas include hydrogen gas and hydrogen-containing gas.

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, the shape of the fuel cell stack 1 can be maintained even when the frame 3 is placed in a high temperature environment at the time of power generation. Therefore, according to this configuration, a fuel cell stack 1 capable of improving battery reliability in a high temperature environment can be obtained. The oxidation-resistant metal refers to a metal having a contact resistance of 50 mΩ · cm ² or less in an oxidizing atmosphere at 800 ° C. for up to 10,000 hours. The contact resistance is a value measured by the four-terminal measuring method. Specific examples of the oxidation-resistant metal include ferritic stainless steel, heat-resistant Cr alloy, heat-resistant NiCr alloy, and austenitic stainless steel.

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

The 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 from the viewpoint of ensuring the above effect. It can be ^x10-6 / K or less. The coefficient of linear thermal expansion is a value in the range of 0 ° C to 800 ° C. Further, the coefficient of linear thermal expansion is basically measured in accordance with JIS Z 2285: 2003 "Method for measuring the coefficient of linear thermal expansion 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 coefficient of linear thermal expansion of each metal is 16 × 10 ^-6 / K or less. 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. When the fuel cell stack 1 has 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. .. According to this configuration, since the sealing distance by the sealing material 4 becomes long, it is advantageous to suppress the cross leak by the sealing material 4 itself. As the material of the sealing material 4, for example, a metal brazing material, a glass material, or the like can be exemplified.

In the fuel cell stack 1, the peeling suppression layer 5 is in contact with the outer peripheral end portion 240 of the cathode 24. In the present embodiment, the peeling suppressing layer 5 is specifically formed on the surface of the intermediate layer 23 exposed to the cathode 24 side in the outer periphery of the cathode 24, as exemplified in FIG. When the fuel cell 2 does not have the intermediate layer 23, the peeling suppression layer 5 can be formed on the surface of the solid electrolyte layer 22 exposed on the cathode 24 side in the outer periphery of 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, as the Cr-containing oxide, a lanthanum-chromium-based oxide can be preferably used. The lanthanum-chromium-based oxide is an oxide containing at least La and Cr as constituent elements. Since the lanthanum-chromium-based oxide is difficult to be oxidized in an oxidizing atmosphere and also difficult to be reduced in a reducing atmosphere, electron conductivity can be exhibited in any atmosphere. Therefore, according to this configuration, it is possible to obtain the effect of suppressing the peeling of the cathode 24 by improving the reduction resistance of the cathode 24 while making the peeling suppressing layer 5 function as a part of the electrode (cathode 24). Therefore, according to the above configuration, the fuel cell stack 1 which is advantageous for securing the power generation capacity for a long period of time can be obtained.

Specific examples of the lanthanum-chromium _- based oxide include La _x A _1-x By Cr _{1-y O3} . 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, 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 both the reduction resistance of the cathode 24 and the electron conductivity of the peeling suppressing layer 5 can be ensured at the same time. It will be easier to make it. Therefore, according to the above configuration, the above-mentioned effect can be ensured.

In La _x A _1-x By Cr _{1-y O3 ,} preferably 0.1 ≦ x ≦ 1, 0 ≦ y ≦ 0.9, more preferably 0.2 ≦ x ≦ 1, 0 ≦ y. ≤0.8 can be set. According to this configuration, it becomes easy to suppress the generation of by-products after power generation of the fuel cell stack 1, which is advantageous for ensuring the electronic conductivity of the peeling suppressing layer 5.

The precursor that becomes a Cr-containing oxide by power generation is specifically a substance that is converted into a Cr-containing oxide by the temperature (heat) at the time of power generation. Such precursors include not only a single substance but also a mixture of a plurality of substances and the like. The precursor 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 destroyed due to long-term operation, emergency stop, abnormal pressure difference between the cathode 24 / anode 21, vibration / impact, etc., and a cross leak occurs, the cathode is used. The peeling of 24 can be suppressed. This is due to the following reasons. In the fuel cell stack 1, the peeling suppressing layer 5 and the cathode 24 are arranged in contact with each other at the outer peripheral end portion 240 of the cathode 24. Therefore, during power generation of the fuel cell stack 1, Cr in the Cr-containing oxide contained in the peeling suppressing layer 5 is solid-diffused from the interface between the peeling suppressing layer 5 and the cathode 24, and at the outer peripheral end portion 240 of the cathode 24. , Cr partially replaces the oxide element in the cathode 24. As a result, the reduction resistance of the outer peripheral end portion 240 of the cathode 24 is increased. As a result, even if a part of the sealing material 4 of the fuel cell stack 1 is destroyed due to long-term operation, emergency stop, abnormal pressure difference between the cathode 24 / anode 21, vibration / impact, etc., and a cross leak occurs. , The peeling of the cathode 24 can be suppressed.

In the fuel cell stack 1, the peeling suppression layer 5 can be specifically configured to be in contact with the outer peripheral end surface 241 of the cathode 24, as illustrated in FIG. When a cross leak occurs in the absence of the peeling suppression layer 5, the hydrogen that has entered the cathode 24 side first touches the outer peripheral end surface 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 likely to be peeled off from this portion. Therefore, according to the above configuration, the reduction resistance at the outer peripheral end portion 240 of the cathode 24 is surely improved by partially substituting the Cr solid-diffused from the peeling suppression layer 5 with the element contained in the oxide in the cathode 24. Can be. Therefore, according to the above configuration, even if a cross leak occurs, it becomes easy to suppress the peeling of the cathode 24.

Further, in the fuel cell stack 1, the peeling suppression layer 5 can be specifically configured to be in contact with the entire circumference of the outer peripheral end portion 240 of the cathode 24, as illustrated in FIG. According to this configuration, the reduction resistance of the outer peripheral end portion 240 at the cathode 24 is increased over the entire circumference. Therefore, according to this configuration, even if a cross leak occurs, it becomes easy to suppress the peeling of the cathode 24 at the entire circumference of the outer peripheral end portion 240 of the cathode 24.

Specifically, the thickness of the peeling suppressing layer 5 can be equal to or larger than the thickness of the cathode 24. According to this configuration, the interface between the peeling suppressing layer 5 and the cathode 24 is ensured, and the above-mentioned action and effect can be ensured.

The thickness of the peeling suppressing 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. In the present embodiment, the thickness of the peeling suppressing layer 5 can be specifically 70 μm.

(Embodiment 2)
The fuel cell stack of the second embodiment will be described with reference to FIG. In addition, among the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-mentioned embodiments represent the same components and the like as those in the above-mentioned embodiments, unless otherwise specified.

As illustrated in FIG. 3, in the fuel cell stack 1 of the present embodiment, the peeling suppression layer 5 has a laminated portion 50 laminated on the cathode 24.

According to this configuration, the peeling suppressing layer 5 can not only be in contact with the outer peripheral end surface 241 of the cathode 24, but also be in contact with the surface 242 of the outer peripheral end portion 240 of the cathode 24 at the laminated portion 50. Therefore, according to this configuration, Cr can be solid-diffused from the laminated portion 50 with respect to the outer peripheral end portion 240 of the cathode 24, and the oxide element in the cathode 24 and Cr are partially replaced. Can be promoted. Therefore, according to this configuration, the fuel cell stack 1 that can easily improve the reduction resistance of the cathode 24 can be obtained. Other configurations and effects are the same as in the first embodiment.

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

Specifically, in the present embodiment, the cathode 24 has a quadrangular shape. Therefore, the outer peripheral end 240 of the cathode 24 can be divided into four end regions 240a, 240b, 240c, and 240d corresponding to the four sides of the quadrangle. In the present embodiment, the oxidant gas inlet (not shown) is arranged on the one end region 240a side of the four end regions 240a, 240b, 240c, 240d in the outer peripheral end portion 240 of the cathode 24. .. On the other hand, of the four end regions 240a, 240b, 240c, 240d in the outer peripheral end portion 240 of 24, the outlet of the oxidant gas O is discharged to the end region 240d side facing one end region 240a (not shown). Is placed. Therefore, in the present embodiment, the peeling suppressing layer 5 is one end region 240d on the outlet side of the oxidant gas O among the four end regions 240a, 240b, 240c, 240d in the outer peripheral end portion 240 of the cathode 24. It is in contact with the remaining three end regions 240a, 240b, 240c excluding.

The end region 240d on the outlet side of the oxidant gas O in the outer peripheral end portion 240 of the cathode 24 is less susceptible to the influence of hydrogen due to cross leakage than the end region 240a on the inlet side of the oxidant gas O. Therefore, when the peeling suppressing layer 5 is not in contact with the end region 240d on the outlet side of the oxidant gas O in the outer peripheral end portion 240 of the cathode 24 (the peeling suppressing layer 5 is partially attached to the outer peripheral end portion 240 of the cathode 24). Even if they are not in contact with each other), the peeling of the cathode 24 can be sufficiently suppressed as compared with the case where the peeling suppressing layer 5 is not present at all. Therefore, according to the above configuration, since the amount of the peeling suppressing layer 5 used can be reduced as compared with the first embodiment, the fuel cell stack which is advantageous in reducing the material cost while suppressing the peeling of the cathode 24. 1 is obtained. 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% Y2O3 (hereinafter, _8YSZ ) powder (average particle size: 0.2 μm), and carbon (pore-forming agent). , Polyvinyl butyral, isoamyl acetate and 1-butanol were mixed in a ball mill to prepare a slurry. The mass ratio of NiO powder to 8YSZ powder is 65:35. Using the doctor blade method, the slurry was applied in layers on the resin sheet, dried, and then the resin sheet was peeled off to prepare a sheet for forming an anode having a thickness of 100 μm. The average particle diameter is the particle diameter (diameter) d50 when the volume-based cumulative frequency distribution measured by the laser diffraction / scattering method shows 50% (hereinafter, the same applies).

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

A slurry is 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 with a ball mill. Prepared. After that, a sheet for forming an intermediate layer having a thickness of 4.0 μm was prepared in the same manner as in the preparation of the sheet for forming the anode.

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

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

A cathode-forming paste was prepared by kneading La _0.6 Sr _0.4 CoO ₃ powder (average particle size: 0.6 μm), ethyl cellulose, and terpineol with three rolls.

A cathode forming paste was applied to the surface of the intermediate layer in the sintered body by a screen printing method, dried, and then fired (baked) at 900 ° C. for 2 hours in an air atmosphere to form a layered cathode (50 μm). .. At this time, the outer shape of the cathode was formed smaller than the outer shape of the anode. The thickness of the cathode can be preferably selected from the range of 20 to 100 μm, more preferably 30 to 80 μm. Further, the firing temperature at the time of forming the cathode can be adjusted within the range of 700 ° C. to 900 ° C. Further, the firing 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 forming a peeling inhibitory layer was prepared by kneading La _0.8 Sr _0.2 CrO ₃ powder (average particle size: 0.5 μm), ethyl cellulose, and terpineol with three rolls.

As shown in FIG. 1, the peeling inhibitory layer forming paste is pattern-printed so as to be in contact with all of the outer peripheral end faces of the cathode, dried, and then peeled by firing (baking) at 850 ° C. for 2 hours in an air atmosphere. An inhibitory layer (60 μm) was formed. The thickness of the peeling inhibitory layer can be selected from the range of preferably 20 to 120 μm, more preferably 30 to 100 μm. Further, the firing temperature at the time of forming the peeling suppressing layer can be adjusted within the range of 700 ° C. to 900 ° C. Further, the firing time at the time of forming the peeling suppressing layer can be appropriately adjusted according to the thickness of the peeling suppressing layer, the amount of the binder component in the paste for forming the peeling suppressing layer, and the like. As a result, a flat plate-shaped fuel cell having a peeling suppression layer was obtained.

As shown in FIGS. 1 and 2, the fuel cell was assembled to a ferritic stainless steel frame. At this time, a metal brazing material was used as a sealing material for sealing between the outer peripheral edge of the fuel cell and the frame. In addition, a ferritic stainless steel retainer was attached to the outer peripheral edge of the fuel cell attached to the frame. At this time, the same metal brazing material as described above was used as the sealing material for sealing between the outer peripheral edge of the fuel cell and the retainer. From the above, a fuel cell with a frame was obtained. Hereinafter, this will be referred to as sample 1. A fuel cell stack can be configured by stacking a plurality of fuel cell cells with a frame via a separator.

-Sample 2-
In the preparation of sample 1, the La _0.8 Sr _0.2 CrO ₃ powder in the peeling inhibitory layer forming paste was changed to the La _0.9 Sr _0.1 CrO ₃ powder, and the peeling inhibitory layer forming paste was used as the cathode. By printing a pattern so as to partially overlap the surface of the outer peripheral end portion of the above, as shown in FIG. 3, the peeling suppression layer is similarly configured to have a laminated portion laminated on the cathode. A fuel cell with a frame of Sample 2 was prepared. In Sample 2, the peeling suppression layer is in contact with both the outer peripheral end surface and the outer peripheral end surface of the cathode.

-Samples 3-14-
In the preparation of sample 1, the La _0.8 Sr _0.2 CrO ₃ powder in the paste for forming the peeling inhibitory layer was used as the La _x A _1-x By Cr _{1-y O 3} powder shown in Table 1 below. Except for the above, the fuel cell with the frame of Samples 3 to 14 was produced in the same manner.

-Sample 15-
In the preparation of the sample 1, as shown in FIG. 4, the paste for forming the peeling inhibitory layer is brought into contact with the remaining end face region of the outer peripheral end portion of the cathode excluding the end face region on the outlet side of the oxidant gas. A fuel cell with a frame of sample 15 was produced in the same manner except for the points where the pattern was printed.

-Sample 1C-
In the preparation of the sample 1, the fuel cell with the frame of the sample 1C was prepared in the same manner except that the peeling suppression layer was not formed.

-Sample 2C-
In the preparation of sample 1, the same applies except that the La _0.6 Sr _0.4 CoO ₃ powder in the cathode forming paste was changed to the La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ powder. A fuel cell with a frame of sample 2C was prepared.

-Sample 3C-
In the preparation of the sample 1, the fuel with the frame of the sample 3C is similarly obtained except that the La _0.6 Sr _0.4 CoO ₃ powder in the cathode forming paste is changed to the Sm _0.5 Sr _0.5 CoO ₃ powder. A battery cell was produced.

-Evaluation test-
Each sample is assembled into a single-layer stack shape, and hydrogen gas is supplied from the outside at 0.5 L / min to the anode side and air is supplied to the cathode side at 0.2 L / min in an environment of 500 ° C. However, it was held for 15 minutes. The environment is a simulation of an environment in which the differential pressure is anode> cathode at a low temperature where the sealing of the outer periphery of the cell is not completed. After holding the above, the temperature was lowered, and the peeling of the cathode in each sample was visually confirmed.

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

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

The present invention is not limited to each of the above embodiments and experimental examples, and various modifications can be made without departing from the gist thereof. In addition, each configuration shown in each embodiment and each experimental example can be arbitrarily combined. For example, the configuration of the second embodiment and the configuration of the third embodiment can be combined.

1 Fuel cell stack 2 Fuel cell cell 21 Anode 22 Solid electrolyte layer 24 Cathode 240 Outer peripheral end 3 Frame 4 Encapsulant 5 Peeling suppression layer

Claims (8)

A fuel cell (2) comprising an anode (21), a solid electrolyte layer (22) and a cathode (24).
A metal frame (3) that supports the outer peripheral edge of the fuel cell and
A sealing material (4) that seals between the outer peripheral edge of the fuel cell and the frame, and
It has a peeling suppression layer (5) in contact with the outer peripheral end portion (240) of the cathode, and has.
The cathode is composed of an oxide containing at least a partially replaceable element with Cr, or an oxide containing an element at least partially replaceable with Cr, and a solid electrolyte .
The peeling suppression layer has a Cr-containing oxide containing Cr or a precursor that becomes the Cr-containing oxide by power generation .
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 By Cr _1-y O ₃ , _but 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. There is a fuel cell cell stack (1). The fuel cell stack according to claim 1 , wherein the oxide containing at least a partially replaceable element with Cr at the cathode is a lanthanum-strontium-cobalt oxide. The fuel cell stack according to claim 1 or 2 , wherein the peeling suppressing layer is in contact with the outer peripheral end surface (241) of the cathode. The fuel cell stack according to claim 3 , wherein the peeling suppression layer has a laminated portion (50) laminated on the cathode. The fuel cell stack according to any one of claims 1 to 4 , wherein the peeling suppressing layer is in contact with the entire circumference of the outer peripheral end portion of the cathode. The peeling suppressing layer is in contact with the remaining end region (240a, 240b, 240c) of the outer peripheral end portion of the cathode excluding the end region (240d) on the outlet side of the oxidant gas. The fuel cell stack according to any one of items 1 to 4 . The fuel cell stack according to any one of claims 1 to 6 , wherein the metal is made of an oxidation-resistant metal material. The fuel cell stack according to any one of claims 1 to 7 , wherein the linear thermal expansion coefficient of the metal is 16 × 10 ^-6 / K or less.

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