JP2018181572A - Solid oxide fuel cell stack - Google Patents

Abstract

A solid oxide fuel cell stack capable of delaying a time until a cathode reaction field is poisoned with a poisoning substance for a long time and improving battery reliability is provided. A solid oxide fuel cell stack (1) includes a plurality of single cells (2), a stack-constituting metal material (3) used for stacking the plurality of single cells (2), and an oxidation supplied to a cathode (23). A trapping layer 4 that is formed on the surface of the stack-constituting metal material 3 facing the agent gas A and collects poisonous substances contained in the oxidant gas A and poisoning the cathode 23. Yes. The collection layer 4 has a stress relaxation structure that relieves stress generated at the interface between the collection layer 4 and the stack constituent metal material 3 due to a difference in thermal expansion between the collection layer 4 and the stack configuration metal material 3. . The stress relaxation structure can have an outer layer 402 including the groove 40 and an inner layer 401 including the crack 41. [Selection] Figure 5

Description

  The present invention relates to a solid oxide fuel cell stack.

  Conventionally, for example, in Patent Document 1, a trap layer is provided on the side of the oxidant gas supply port in the oxidant gas flow path, which is separated from the cathode of the single cell and adsorbs the cathode poisoning substance contained in the oxidant gas. A solid oxide fuel cell stack is disclosed. The same document describes that the cathode and the trap layer are arranged side by side on the same surface of the solid electrolyte layer.

JP, 2015-90788, A

  The prior art has the following problems. In the prior art, not all of the oxidant gas supplied to the cathode passes through the trap layer. Therefore, the poisoning substance contained in the oxidant gas which has not passed through the trap layer chemically reacts with the cathode material, and poisoning from the cathode surface proceeds from an early stage. In particular, in the prior art, the cathode reaction site contributing to power generation, which is on the side of the solid electrolyte layer inside the cathode, is poisoned at an early stage, so that the cell performance is greatly reduced and the durability is reduced. As a result, the prior art is likely to lower battery reliability.

  The present invention has been made in view of such problems, and it is possible to delay the time until the cathode reaction site is poisoned by the poisoning substance for a long time, and it is possible to improve the battery reliability. It is an object of the present invention to provide an oxide fuel cell stack.

One aspect of the present invention comprises a plurality of unit cells (2) comprising an anode (21), a solid electrolyte layer (22) and a cathode (23).
A stack metal material (3, 31, 32) used to stack a plurality of the above single cells;
A trap which is formed on the surface of the stack metal member facing the oxidant gas (A) supplied to the cathode, and collects poisonous substances contained in the oxidant gas and poisoning the cathode. It has a stratum (4),
The trapping layer has a stress relieving structure for relieving a stress generated at an interface between the trapping layer and the stack forming metal material due to a thermal expansion difference between the trapping layer and the stack forming metal material. It is in the solid oxide fuel cell stack (1).

  The solid oxide fuel cell stack has the above configuration. Therefore, in the solid oxide fuel cell stack, the poisoning substance is collected by the collection layer formed on the surface of the stack-constituting metal material exposed to the oxidant gas. In addition, since the trapping layer has the above-described stress relaxation structure, peeling of the trapping layer from the surface of the stack constituent metal material due to the thermal expansion difference between the trapping layer and the stack constituent metal member can also be suppressed. . Therefore, according to the solid oxide fuel cell stack, the time until the cathode reaction site is poisoned by the poisoning substance can be delayed for a long time, and the deterioration of the cell performance is suppressed for a long time, Battery reliability can be improved.

  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 a cross section of a solid oxide fuel cell stack according to Embodiment 1; FIG. 5 is an explanatory view schematically showing a cross section of a collection layer in Embodiment 1. (A) An explanatory view schematically showing the interconnector, which is one of the stack-constituting metal materials of the solid oxide fuel cell stack according to Embodiment 1, as viewed from the surface side facing the oxidant gas, b) It is explanatory drawing which showed typically the flame | frame which is one of the stack structure metal material which the solid oxide fuel cell stack of Embodiment 1 has, seeing from the surface side which faces oxidant gas. In the solid oxide fuel cell stack of Embodiment 2, it is an explanatory view schematically showing the trapping layer as viewed from the outer surface side thereof. It is explanatory drawing which showed the VV line | wire cross section of FIG. 5 typically. (A) An explanatory view schematically showing the interconnector which is one of the stack-constituting metal materials of the solid oxide fuel cell stack according to Embodiment 3 as viewed from the surface side facing the oxidant gas, b) It is explanatory drawing which showed typically the flame | frame which is one of the stack structure metal material which the solid oxide fuel cell stack of Embodiment 3 has from the surface side which faces oxidant gas. (A) An explanatory view schematically showing the interconnector which is one of the stack-constituting metal materials of the solid oxide fuel cell stack according to Embodiment 4 as viewed from the surface side facing the oxidant gas, b) It is explanatory drawing which showed typically the flame | frame which is one of the stack structure metal material which the solid oxide fuel cell stack of Embodiment 4 has from the surface side which faces oxidant gas. In the solid oxide fuel cell stack of Embodiment 5, it is an explanatory view schematically showing the trapping layer as viewed from the outer surface side thereof. In the solid oxide fuel cell stack of Embodiment 6, it is an explanatory view showing the collection layer typically seeing from the outer surface side. In the solid oxide fuel cell stack of Embodiment 7, it is an explanatory view showing the collection layer typically seeing from the outer surface side. In solid oxide fuel cell stack of Embodiment 8, it is an explanatory view showing the collection layer typically seeing from the outer surface side. In Experimental Examples 1-4, it is explanatory drawing for demonstrating the form of the groove part in a collection layer.

  The solid oxide fuel cell stack of each embodiment (hereinafter, may be simply referred to as "cell stack") will be described with reference to the drawings.

(Embodiment 1)
The cell stack of Embodiment 1 will be described with reference to FIGS. 1 to 3. As illustrated in FIGS. 1 to 3, the cell stack 1 of the present embodiment includes a plurality of unit cells 2, a stack-constituting metal material 3, and a collection layer 4. This will be described in detail below.

  In the cell stack 1, the unit cell 2 includes an anode 21, a solid electrolyte layer 22 and a cathode 23. In the present embodiment, as illustrated in FIG. 1, an example in which the single cell 2 further includes an intermediate layer 24 between the solid electrolyte layer 22 and the cathode 23 is shown. The intermediate layer 24 is a layer mainly for suppressing the reaction between the solid electrolyte layer material and the cathode material. The unit cell 2 may have either a flat plate or cylindrical battery structure. Specifically, in the present embodiment, the unit cell 2 has a flat battery structure, and the anode 21, the solid electrolyte layer 22, the intermediate layer 24, and the cathode 23 are stacked in this order to It is joined. In addition, in FIG. 1, the anode support single cell 2 which makes the anode 21 which is an electrode function as a support body is illustrated.

  The anode 21 may be composed of a single layer or multiple layers. FIG. 1 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, the anode 21 may be, 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 side. A configuration provided can be made. 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 F 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 24, 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 24.

  The thickness of the intermediate layer 24 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 from the cathode, and the like.

As a material of the cathode 23, for example, a conductive oxide such as a transition metal perovskite oxide, a mixture of a conductive oxide and a solid electrolyte, and the like can be exemplified. Specifically as the transition metal perovskite oxide, for example, La _x Sr _1-x CoO ₃ (where 0 ≦ x ≦ 1, preferably 0 <x <1, more preferably 0.2 ≦ x ≦ 0.8), Sm _x Sr _1−x CoO ₃ (where 0 ≦ x ≦ 1, preferably 0 <x <1, more preferably 0.1 ≦ x ≦ 0.7), La _x Sr _1-x Co _y Fe _1-y O ₃ (where 0 ≦ x ≦ 1, preferably 0 <x <1, more preferably 0.2 ≦ x ≦ 0.8, 0 ≦ y ≦ 1, Preferably, 0 <y <1, more preferably 0.01 ≦ y ≦ 0.5, etc. can be exemplified. Moreover, as the solid electrolyte, the above-mentioned cerium oxide-based oxide, zirconium oxide-based oxide, etc. can be exemplified. These can be used alone or in combination of two or more. In the present embodiment, as the material of the cathode 23, specifically, for example, La _x Sr _1-x CoO ₃ (0 ≦ x ≦ 1), Sm _x Sr _1-x CoO ₃ (0 ≦ x ≦ 1), A mixture of at least one of these and a ceria-based solid solution doped with at least one of Gd and Sm can be used.

  The thickness of the cathode 23 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 23 can be 50 μm.

  In the cell stack 1, the stack-forming metal material 3 is a metal member used to stack a plurality of single cells. In the present specification, metals include alloys. Specifically, for example, the frame 32 supporting the outer peripheral edge of the unit cell 2 and the unit cells 2 disposed between the unit cells 2 as the stack-constituting metal material 3 electrically connect the unit cells 2 and an oxidant An interconnector 31 for separating the gas A and the fuel gas F, a current collector disposed between the unit cell 2 and the interconnector 31, and the like can be exemplified.

  In the present embodiment, as shown in FIG. 1, a metal frame 32 and a metal interconnector 31 are illustrated as the stack-constituting metal material 3 exposed to the oxidant gas.

The stack constituent metal material 3 can be made of oxidation resistant metal. According to this configuration, the shape and the conductivity can be maintained even when the stack constituent metal material 3 is placed in a high temperature environment at the time of cell stack operation. Therefore, according to this configuration, it is possible to obtain a 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.

  More specifically, in the present embodiment, the cell stack 1 has a stacked structure in which a plurality of unit cells 2 whose outer peripheral edge is supported by the frame 32 are stacked via the interconnector 31. In the cell stack 1, the oxidant gas A can be supplied along the in-plane direction of the cathode 23. Also, the fuel gas F can be supplied along the in-plane direction of the anode 21. Specifically, in the cell stack 1 of the present embodiment, a gap is provided between the frame 32 and the interconnector 31 on the cathode 23 side, and the gap is an oxidant gas flow in which the oxidant gas A flows. It is considered to be a road. In addition, on the anode 21 side, a gap is also provided between the frame 32 and the interconnector 31, and the gap is a fuel gas flow path through which the fuel gas F flows. A cathode side current collector (not shown) as the stack constituting metal material 3 is disposed in the oxidant gas flow path, and the cathode side current collector is configured to be in contact with the cathode 23 and the interconnector 31. it can. Further, as shown in FIG. 1, the metal anode side current collector 9 is disposed in the fuel gas flow path, and the anode side current collector 9 is configured to be in contact with the anode 21 and the interconnector 31. it can. In addition, as oxidant gas A, air, oxygen gas, etc. can be illustrated, for example. As fuel gas F, hydrogen gas, hydrogen-containing gas, etc. can be illustrated, for example.

  In the cell stack 1, the collection layer 4 is formed on the surface of the stack constituent metal material 3 facing the oxidant gas A supplied to the cathode 23. The collection layer 4 may be formed on all the stack forming metal materials 3 having a surface facing the oxidant gas A, or may be formed on a part of the stack forming metal materials 3. In addition, the collection layer 4 may be formed on the entire surface of the stack constituting metal material 3 facing the oxidant gas A, or may be formed on a part of the surface. As the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A increases, the trapping effect can be increased, and the trapping layer 4 can be produced in the range having the trapping effect. As the area of (1) decreases, the material and processing cost reduction effects become larger.

  The collection layer 4 is at least from the inlet-side end of the oxidant gas A among the surfaces of the stack-constituting metal material 3 facing the oxidant gas A, from the viewpoint of ensuring the collection effect, etc. It is preferable to form so that the area | region to the single cell 2 edge part of the inlet side of oxidizing agent gas A may be included. More preferably, from the viewpoint of making the collection effect more reliable, the collection layer 4 is an inlet-side end of the oxidizing gas A among the surfaces of the stack forming metal members 3 facing the oxidizing gas A. It is good to form so that the area | region from the part to the single cell 2 edge part or more of the exit side of the oxidizing agent gas A may be included.

  In the present embodiment, specifically, as shown in FIG. 3, the stack-constituting metal material 3 having a surface facing the oxidant gas A is specifically made into an interconnector 31 and a frame 32. There is. Then, as shown in FIG. 3A, of the surface of the interconnector 31 facing the oxidant gas A, the unit cell 2 at the outlet side of the oxidant gas A from the inlet side end of the oxidant gas A. The trapping layer 4 is formed so as to include the region up to the end. In the present embodiment, as shown in the range of arrow Y in FIG. 3A, the trapping layer 4 is formed on the entire surface of the interconnector 31 facing the oxidant gas A. Similarly, as shown in FIG. 3B, of the surface of the frame 32 facing the oxidant gas A, the unit cell 2 on the outlet side of the oxidant gas A from the inlet end of the oxidant gas A The trapping layer 4 is formed so as to include the region up to the end. In the present embodiment, the trapping layer 4 is formed on the entire surface of the frame 32 facing the oxidant gas A, as indicated by the range Y of the arrow in FIG. In FIG. 3, the holes formed on the outer peripheral edge of the frame 32 and the interconnector 31 are an oxidant gas supply manifold, an oxidant gas discharge manifold, a fuel gas supply manifold, and a fuel gas discharge manifold (all not shown). To form part of the

  The collection layer 4 collects poisonous substances contained in the oxidant gas A and poisoning the cathode 23. The collection of the poisoning substance by the collection layer 4 includes a chemical reaction with the poisoning substance. As a poisoning substance, elements, such as S, Cl, Cr, B, Si, and P, the compound containing these elements, etc. can be illustrated, for example. The poisoning substance can be contained in the oxidant gas A singly or in combination. The collection layer 4 is configured to be able to collect at least one poisoning substance. In addition, S and Cl mentioned above may be contained, when using air as oxidant gas. Further, Cr and P may be mixed from the stack forming metal material 3 or the like. Also, B, Si, P may be mixed from a gas seal material (not shown) or the like used in the cell stack 1.

The collection layer 4 can be configured to have conductivity. Specifically, in the present embodiment, the collection layer 4 can be configured to include a conductive oxide. In this case, the conductive oxide can include ACoO ₃ . However, in ACoO ₃ , A is at least two elements selected from the group consisting of La, Sm, and Sr, preferably, A is an element containing at least La and Sr, or Sm and Sr. The chemical composition ratio of the selected two kinds of elements can be 1 in total. According to this configuration, the reactivity with the poisoning substance becomes high, and the collection efficiency of the poisoning substance by the collection layer 4 can be improved. Therefore, according to this configuration, it is possible to obtain the cell stack 1 in which the above-described effects can be ensured. In the present embodiment, an example in which the current is collected by bringing the conductive collection layer 4 formed on the surface of the interconnector 31 into contact with the cathode 23 is shown.

As ACoO ₃ , specifically, La _x Sr _1-x CoO ₃ (where 0 <x <1, preferably 0.2 ≦ x ≦ 0.8), Sm _x Sr _1-x CoO ₃ ( However, transition metal perovskite oxides such as 0 <x <1, preferably 0.1 ≦ x ≦ 0.7) can be exemplified. These can be used alone or in combination of two or more. When the transition metal perovskite oxide is used as ACoO ₃ , the conductivity is high and the activity is high. Therefore, the poisoning substance can be sufficiently collected by a chemical reaction. Therefore, according to this configuration, it is possible to obtain the cell stack 1 that can easily exert the above-described effects.

  The conductive oxide of the collection layer 4 can be composed of the same kind of material as the conductive oxide of the cathode 23. According to this configuration, even if the trapping layer 4 is separated and scattered from the surface of the stack constituting metal material 3 due to the thermal expansion difference between the trapping layer 4 and the stack constituting metal material 3, the cathode performance is prevented from being reduced. can do. Therefore, according to this configuration, the battery reliability of the cell stack 1 can be improved. Further, according to this configuration, when the conductive collection layer 4 and the cathode 23 are brought into contact with each other to collect current, there is an advantage that reduction of the current collection resistance can be easily achieved. The same kind of conductive oxide of the trapping layer 4 and the conductive oxide of the cathode 23 means that the elements of the material are the same, and the coincidence to the element composition ratio is not required.

  The trapping layer 4 has a stress relaxation structure. The stress relaxation structure has a structure capable of relieving the stress generated at the interface between the trapping layer 4 and the stack forming metal member 3 due to the thermal expansion difference between the trapping layer 4 and the stack forming metal member 3 .

  The stress relaxation structure can be configured to include a crack 41 extending in the thickness direction of the trapping layer 4. According to this configuration, the thermal expansion difference between the trapping layer 4 and the stack-constituting metal material 3 can be obtained by positively introducing into the trapping layer 4 the cracks 41 which are usually not to be inserted from the viewpoint of material destruction. The stress generated at the interface between the collection layer 4 and the stack-forming metal material 3 can be relieved by this. At this time, the adhesion between the trapping layer 4 and the stack-constituting metal material 3 is also secured by setting the direction of the crack 41 introduced in advance to the trapping layer 4 as the thickness direction of the trapping layer 4. Therefore, according to the above configuration, peeling of the trapping layer 4 from the surface of the stack constituting metal material 3 due to the thermal expansion difference between the trapping layer 4 and the stack constituting metal material 3 can be easily suppressed. In addition, according to the crack 41, it is possible to form a very narrow gap extending in the thickness direction, as compared to an artificially formed groove. Therefore, according to the above configuration, it becomes difficult to expose the surface of the stack forming metal material 3, and it becomes easy to suppress the scattering of the poisoning substance generated from the stack forming metal material 3. In addition, since the specific surface area of the trapping layer 4 is increased by the cracks 41, it is also advantageous in trapping poisoning substances.

  The maximum value of the width of the crack 41 in the trapping layer 4 is preferably 2 mm or less, more preferably 1 mm or less, and still more preferably, from the viewpoint of suppression of exposure of the surface of the stack constituting metal material 3 and crack formability. It can be 0.5 mm or less, still more preferably 0.1 mm or less.

  Further, specifically, the tip of the crack 41 in the collection layer 4 can be configured to reach the surface of the stack forming metal material 3. According to this configuration, since the tip of the crack 41 has reached the surface of the stack-forming metal material 3 in advance before the operation of the cell stack 1, the stress relaxation effect by the stress relaxation structure can be easily obtained sufficiently. Further, since the progress of the crack 41 in the trapping layer 4 can be suppressed at the time of operation of the cell stack 1, there is an advantage such as easy suppression of peeling of the trapping layer 4 and the like.

  Further, in the present embodiment, the conductive oxide constituting the trapping layer 4 can be specifically composed of particles. And the crack 41 mentioned above can be set as the structure currently formed along the grain boundary (not shown) in the collection layer 4. As shown in FIG. According to this configuration, the effect by the above-described crack 41 can be made reliable.

  In the present embodiment, specifically, as shown in FIG. 2, a plurality of cracks 41 are formed in the collection layer 4, and each crack 41 is formed of a stack-forming metal material from the surface of the collection layer 4. An example is shown extending in the thickness direction of the collection layer 4 up to the surface 3.

  The thickness of the collection layer 4 can be preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more from the viewpoint of improving the collection performance of poisoning substances. The thickness of the collection layer 4 is preferably 250 μm or less, more preferably 200 μm or less, from the viewpoint of ease of formation of the crack 41 extending in the thickness direction of the collection layer 4, saturation of collection effect, material cost reduction, etc. More preferably, it can be 175 μm or less, still more preferably 150 μm or less. The thickness of the trapping layer 4 is an average value of the thickness measurement values of the trapping layer 4 measured at arbitrary ten locations when a cross section perpendicular to the layer surface of the trapping layer 4 is observed by SEM.

Specifically, the linear thermal expansion coefficient of the trapping layer 4 can be 16 × 10 ⁻⁶ / K or more. According to this configuration, there is an advantage that the width of the crack generated at the time of the heat treatment can be easily maintained without being expanded during the thermal cycle operation during the continuous operation of the battery. Moreover, the linear thermal expansion coefficient of the stack configuration metal material 3 described above can be less than 16 × 10 ⁻⁶ / K. According to this configuration, the crack 41 is easily generated by the heat treatment when forming the collection layer 4, and the cell stack 1 having the collection layer 4 having the stress relaxation structure including the crack 41 can be easily realized. From the viewpoint of securing the above effects, it is preferable that the linear thermal expansion coefficient of the trapping layer 4 and the linear thermal expansion coefficient of the stack-constituting metal material 3 be in the above ranges. The linear thermal expansion coefficients of the materials exemplified above as the materials constituting the trapping layer 4 and the stack-constituting metal material 3 are all within the range of the linear thermal expansion coefficient.

The linear thermal expansion coefficient of the trapping layer 4 at 700 ° C. or more is preferably 16 × 10 ⁻⁶ / K or more, more preferably 17 × 10 ⁻⁶ /, from the viewpoint of ensuring the above effects and the like. It can be made K or more, more preferably 18 × 10 ⁻⁶ / K or more. The linear thermal expansion coefficient of the trapping layer 4 at 700 ° C. or higher is preferably 25 × 10 ⁻⁶ / K or less, more preferably 23 × 10 ⁻ or less, from the viewpoint of ensuring the above effects and the like. ⁶ / K or less, more preferably 22 × 10 ⁻⁶ / K or less. The linear thermal expansion coefficient of the stack-constituting metal material 3 at 500 ° C. or higher is preferably 7 × 10 ⁻⁶ / K or more, more preferably 9 × 10 ⁻⁶ from the viewpoint of ensuring the above effects and the like. / K or more, more preferably 10 × 10 ⁻⁶ / K or more. Further, the linear thermal expansion coefficient of the stack-constituting metal material 3 at 500 ° C. or higher is preferably 16 × 10 ⁻⁶ / K or less, more preferably 14 × 10 ⁶ from the viewpoint of ensuring the above effects and the like. ^-6 / K or less, more preferably 13 × 10 ^-6 / K or less.

The linear thermal expansion coefficient of the trapping layer 4 and the linear thermal expansion coefficient of the stack-constituting metal material 3 are basically in accordance with JIS R 1618: 2002 “Method of measuring thermal expansion by thermal mechanical analysis of fine ceramics”. Measured. Specifically, a sample formed of each material is set in a full expansion thermal mechanical analyzer, and the temperature is increased at a temperature rising rate of 10 ° C./min. The sample expands from length L ₀ to L ₁ until the temperature T rises from T ₀ (= 100 ° C.) to T ₁ (= 700 ° C.). The linear thermal expansion coefficient at this time (/ K), calculated from calculation formula _{(dL / dT) T = T1} / L 0. _{However, (dL / dT) T =} T1 , the temperature T is the slope of the long curve at the time of _{T 1.} Moreover, the linear thermal expansion coefficient of the stack-constituting metal material 3 is basically measured in accordance with JIS Z 2285: 2003 “Method of measuring linear thermal expansion coefficient of metal material”.

  In manufacturing the cell stack 1, the single cell 2 and the stack constituent metal material 3 can be prepared by a known method. The collection layer 4 can be formed on the surface of the stack-forming metal material 3 as follows, for example.

  Prepare a collection layer forming paste. The collection layer forming paste can contain the collection layer material described above, a binder made of an organic material, and the like. Next, a paste for forming a collection layer is applied to the surface of the stack-constituting metal material 3 on the side of the oxidant gas A by screen printing or the like, and dried. Thereafter, the stack-constituting metal material 3 having the coating film of the collection layer forming paste is heat-treated to bake the coating film. The thickness of the coating can be, for example, 5 to 250 μm. The heat treatment temperature can be adjusted, for example, in the range of 700 ° C to 900 ° C. Further, the heat treatment time can be appropriately adjusted depending on the thickness of the coating film, the amount of binder and the like. In addition, the crack 41 mentioned above can be generated in the collection layer 4 at the time of heat processing.

  Thereafter, the cell stack 1 may be manufactured by, for example, attaching the single cell 2 to the frame 32 and stacking a plurality of the single cells 2 with the frame 32 via the interconnector 31 using a known method. it can.

  The cell stack 1 has the above configuration. Therefore, in the cell stack 1, the poisoning substance is collected by the collection layer 4 formed on the surface of the stack constituent metal material 3 exposed to the oxidant gas A. In addition, since the trapping layer 4 has a stress relaxation structure, peeling of the trapping layer 4 from the surface of the stack forming metal member 3 due to the thermal expansion difference between the trapping layer 4 and the stack constituting metal member 3 is also suppressed can do. Therefore, according to the cell stack 1, the time until the cathode reaction site is poisoned by the poisoning substance can be delayed for a long time, the deterioration of the battery performance is suppressed over a long period, and the battery reliability is improved. be able to.

Second Embodiment
The cell stack of Embodiment 2 will be described with reference to FIGS. 4 and 5. 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. 4 and FIG. 5, the cell stack 1 of the present embodiment has a stress relaxation structure including grooves 40 formed in the thickness direction of the collection layer 4 from the surface of the collection layer 4. doing. According to this configuration, when the trapping layer 4 is formed on the surface of the stack-constituting metal material 3, the crack 41 is easily generated from the groove 40.

  Specifically, in the present embodiment, the bottom of the groove 40 is disposed in the trapping layer 4. That is, the bottom of the groove 40 does not reach the surface of the stack-forming metal material 3. According to this configuration, the introduction of the groove portion 40 does not positively expose the surface of the stack-constituting metal material 4, and scattering of poisoning substances generated from the stack-constituting metal 3 can be easily suppressed. Further, according to this configuration, when the trapping layer 4 is formed on the surface of the stack-constituting metal material 3, the crack 41 is easily generated from the bottom end of the groove 40.

  Specifically, in the present embodiment, as shown in FIG. 5, the crack 41 extends from the bottom end of the groove 40 toward the surface of the stack metal 4. FIG. 5 shows an example in which the tip of the crack 41 has reached the surface of the stack constituent metal material 3. The end on the bottom side of the groove 40 includes the bottom of the groove 40 and the side surface near the bottom of the groove 40. That is, in the above configuration, the occurrence position of the crack 41 is not limited to only the bottom of the groove 40. The collection layer 4 can also include a crack 41 extending in the thickness direction of the collection layer 4 at a location other than the groove 40.

  Specifically, the stress relaxation structure can be configured to have an outer layer 402 including the groove portion 40 and an inner layer 401 including the crack 401. According to this configuration, it is possible to ensure a stress relaxation structure having a crack 41 extending from the end on the bottom side of the groove 40 toward the surface of the stack constituent metal material 3. The outer layer 402 is a region from the surface of the collection layer 4 to the bottom of the groove 40. The inner layer 401 is a region from the bottom of the groove 40 to the interface with the stack-forming metal material 3.

  In this case, specifically, the thickness of the outer layer 402 can be larger than the thickness of the inner layer 401. According to this configuration, peeling of the trapping layer 4 from the surface of the stack constituting metal material 3 due to the thermal expansion difference between the trapping layer 4 and the stack constituting metal material 3 can be easily suppressed. In addition, when the trapping layer 4 is formed on the surface of the stack-constituting metal material 3, there is also an advantage that the crack 41 is easily generated in the thickness direction of the trapping layer 4. More specifically, the thickness of the outer layer 402 is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 50 μm or more, from the viewpoint of improving the ability to collect poisoning substances, etc. it can. More specifically, the thickness of the outer layer 402 can be preferably 250 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less from the viewpoint of suppression of performance decrease due to increase in material resistance. . More specifically, the thickness of the inner layer 401 can be preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more, from the viewpoint of suppressing the reaction with the metal material and the like. More specifically, the thickness of the inner layer 401 can be preferably 150 μm or less, more preferably 100 μm or less, and still more preferably 50 μm or less from the viewpoint of suppression of interfacial peeling with a metal, and the like. As for the thickness of the outer layer 402 and the thickness of the inner layer 401, the cross section perpendicular to the layer surface of the trapping layer 4 is observed by SEM, and the thickness measurement value of the outer layer 402 and the thickness measurement value of the inner layer 401 are measured at any ten locations. It is the average value of each.

  The grooves 40 may be patterned. According to this configuration, when the trapping layer 4 is formed on the surface of the stack-constituting metal material 3, the crack 41 can be easily generated in the thickness direction of the trapping layer 4 stably from the groove 40. Moreover, according to this configuration, the introduction of the crack 41 can be easily controlled. Moreover, according to this configuration, it becomes easy to suppress the peeling of the trapping layer 4 due to the progress of the crack 41 in the trapping layer 4 during the operation of the cell stack 1. Moreover, according to this structure, it becomes easy to suppress the variation in the collection capability by the collection layer 4.

  Specifically, for example, when viewed from the outer surface side of the collection layer 4, the groove portion 40 is most preferably a pattern portion 42 formed of a triangular shape, a square shape, a hexagonal shape, an octagon shape, or a combination thereof. It may be patterned to form a close-filled shape. According to this configuration, the crack 41 can be more easily generated in the thickness direction of the trapping layer 4 more stably from the groove 40. In the present embodiment, as shown in FIG. 4, the groove 40 is formed such that a hexagonal-shaped pattern portion 42 is closely packed as viewed from the outer surface side of the collection layer 4. 40 are patterned.

  In the present embodiment, specifically, the width of the pattern portion 42 can be configured to be larger than the width of the groove portion 40. According to this configuration, when the trapping layer 4 is formed on the surface of the stack-constituting metal material 3, it is easy to suppress the occurrence of the crack 41 from a place other than the groove 40. Specifically, the width of the groove 40 can be preferably 0.05 mm or more, more preferably 0.1 mm or more, and still more preferably 0.2 mm or more. The width of the groove 40 can be preferably 1 mm or less, more preferably 0.8 mm or less, and even more preferably 0.6 mm or less. The width of the pattern portion 42 is a maximum value of the cross-sectional width of the pattern portion 42 in the layer surface direction, which is measured by SEM observation of a cross section along the thickness direction of the collection layer 4. The width of the groove 40 is the maximum value of the cross-sectional width of the groove 40 in the layer surface direction, which is measured by SEM observation of a cross section along the thickness direction of the trapping layer 4.

  The formation of the grooves 20 in the collection layer 4 can be performed, for example, by the following method. The paste for forming a collection layer is applied to the surface of the stack-constituting metal material 3 on the side of the oxidant gas A by a screen printing method or the like, and dried. Next, the top of the dried coating is masked with a mask that can form a predetermined groove 40. Next, in the same manner as described above, the paste for forming a collection layer is applied and dried. The mask is then peeled off. Next, the stack-constituting metal material 3 having a laminated coating film of the collection layer forming paste is heat-treated to bake the laminated coating film. In addition, the crack 41 from the groove part mentioned above can be generated in the inner layer 401 of the collection layer 4 at the time of heat processing.

(Embodiment 3)
The cell stack of the third embodiment will be described with reference to FIG.

  As illustrated in FIG. 6, in the cell stack 1 of the present embodiment, the collection layer 4 is formed on a part of the surface of the stack constituent metal material 3 facing the oxidant gas A. In this embodiment, specifically, as shown in FIG. 6, the stack-constituting metal material 3 having a surface facing the oxidant gas A is an interconnector 31 and a frame 32.

  Then, in the present embodiment, as shown in FIG. 6A, of the surface of the interconnector 31 facing the oxidant gas A, the outlet of the oxidant gas A from the inlet-side end of the oxidant gas A The trapping layer 4 is formed in the region up to the end of the unit cell 2 on the side (the range of the arrow in the drawing). Similarly, as shown in FIG. 6B, of the surface of the frame 32 facing the oxidant gas A, the unit cell 2 on the outlet side of the oxidant gas A from the inlet end of the oxidant gas A The trapping layer 4 is formed in the region up to the end (in the figure, the range of the arrow). The other configuration is the same as that of the second embodiment.

  Also in the present embodiment, the same function and effect as in the second embodiment can be obtained. However, the second embodiment is more advantageous than the third embodiment in that the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A is larger than that of the third embodiment. It is. Further, in the third embodiment, as compared with the second embodiment, the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A is smaller, so that the material and processing cost reduction effect It is advantageous in point.

(Embodiment 4)
The cell stack of Embodiment 4 will be described with reference to FIG.

  As illustrated in FIG. 7, in the cell stack 1 of the present embodiment, the collection layer 4 is formed on part of the surface of the stack constituent metal material 3 facing the oxidant gas A. In the present embodiment, specifically, as shown in FIG. 7, the stack-constituting metal material 3 having a surface facing the oxidant gas A is made into an interconnector 31 and a frame 32.

  And in this embodiment, as shown in FIG. 7A, of the surface of the interconnector 31 facing the oxidant gas A, the inlet of the oxidant gas A from the inlet side end of the oxidant gas A The trapping layer 4 is formed in the region up to the end of the unit cell 2 on the side (the range of the arrow Y in the drawing). Similarly, as shown in FIG. 7B, of the surface of the frame 32 facing the oxidant gas A, the unit cell 2 on the inlet side of the oxidant gas A from the inlet end of the oxidant gas A The trapping layer 4 is formed in a region up to the end (in the range of the arrow Y in the drawing). The other configuration is the same as that of the second embodiment.

  Also in the present embodiment, the same function and effect as in the second embodiment can be obtained. However, the second embodiment is more advantageous than the fourth embodiment in that the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A is larger, in terms of the trapping effect. It is. Further, in the fourth embodiment, since the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A is smaller than that of the second embodiment, the material and the processing cost reduction effect It is advantageous in point.

  Similarly, in the third embodiment, the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A is larger than that of the fourth embodiment in terms of the trapping effect. It is advantageous. Further, in the fourth embodiment, since the area of the trapping layer 4 formed on the surface of the stack-constituting metal material 3 facing the oxidant gas A is smaller than that of the third embodiment, the material and the processing cost are reduced. It is advantageous in point.

Embodiment 5
The cell stack of the fifth embodiment will be described with reference to FIG.

  As illustrated in FIG. 8, in the cell stack 1 of the present embodiment, when viewed from the outer surface side of the collection layer 4, the groove 40 has a shape in which a triangular pattern portion 42 is closely packed. It is patterned to The other configuration is the same as that of the second embodiment. Also in the present embodiment, the same function and effect as in the second embodiment can be obtained.

Embodiment 6
The cell stack of the sixth embodiment will be described with reference to FIG.

  As illustrated in FIG. 9, in the cell stack 1 of the present embodiment, when viewed from the outer surface side of the collection layer 4, the groove 40 has a shape in which the rectangular pattern portion 42 is closely packed. It is patterned to The other configuration is the same as that of the second embodiment. Also in the present embodiment, the same function and effect as in the second embodiment can be obtained.

Seventh Embodiment
The cell stack of the seventh embodiment will be described with reference to FIG.

  As illustrated in FIG. 10, in the cell stack 1 of the present embodiment, as viewed from the outer surface side of the collection layer 4, the groove 40 has a combination of a hexagonal pattern portion 421 and a triangular pattern portion 422. It is patterned so that the close-packed shape is formed. The other configuration is the same as that of the second embodiment. Also in the present embodiment, the same function and effect as in the second embodiment can be obtained.

Seventh Embodiment
The cell stack of the seventh embodiment will be described with reference to FIG.

  As illustrated in FIG. 11, in the cell stack 1 of the present embodiment, as viewed from the outer surface side of the collection layer 4, the groove 40 has a combination of an octagonal pattern portion 423 and a square pattern portion 424. It is patterned so that the close-packed shape is formed. The other configuration is the same as that of the second embodiment. Also in the present embodiment, the same function and effect as in the second embodiment can be obtained.

(Experimental example 1)
La _0.6 Sr _0.4 CoO ₃ (hereinafter, LSC) powder (average particle size: 0.6 μm), ethyl cellulose and terpineol are kneaded with a three-roll mill to form a paste for forming a collection layer Prepared. Further, an interconnector made of ferrite stainless steel and a frame made of ferrite stainless steel were prepared.

  The coating layer-forming paste was applied to a surface on the oxidant gas side of the interconnector and the frame at 100 μm by screen printing, and a coating was formed by drying. Thereafter, each of the coated films was baked by heat treating the interconnector and the frame having the coated film at 800 ° C. for 2 hours to form each collection layer. When the cross section of each collection layer was observed by SEM, in each collection layer, many cracks extended in the thickness direction of the collection layer and the tip reached the interface of the interconnector and the frame were confirmed . In addition, the maximum value of the width | variety of the formed crack was 0.5 mm or less.

Next, a single cell was assembled to the frame, and a plurality of single cells with the frame were stacked via an interconnector to obtain a cell stack of sample 1. Incidentally, in the cell stack of the sample 1, the cathode of the unit cell _is configured to include La _{0.6 Sr} 0.4 CoO _3.

  Also, separately from the above, the paste for forming a trapping layer is applied to the surface on the oxidant gas side of the interconnector and the frame at 40 μm by screen printing, and then dried, to thereby form each coating of the first layer. A film was formed. Next, each coating film of the first layer was masked with a mask capable of forming a shape (honeycomb pattern) in which hexagonal pattern portions are closely packed by the groove portions. Subsequently, the paste for collection layer formation was each apply | coated by 80 micrometers by screen printing method, and each coating film of 2nd layer was formed by making it dry. After that, the laminated film was baked by heat treating the interconnector and the frame having the laminated film at 800 ° C. for 2 hours to form each collection layer. When the cross section of each collection layer was observed by SEM, each collection layer was composed of an outer layer containing a groove and an inner layer containing a large number of cracks. In each collecting layer, many cracks extending from the end on the bottom side of the groove to the thickness direction of the collecting layer and having the tip reaching the interface of the interconnector and the frame were confirmed. In addition, the maximum value of the width | variety of the formed crack was 0.5 mm or less. Further, the thickness of the inner layer in the collection layer was 30 μm, the thickness of the outer layer was 70 μm, the width of the groove was 0.5 mm, and the width of the pattern was 2 mm.

  Thereafter, the cell stack of sample 2 was obtained in the same manner as the preparation of the cell stack of sample 1.

(Experimental example 2)
According to the preparation of the cell stack of sample 2, as shown in FIG. 12, the thickness (depth of groove) H2 of the outer layer in the trapping layer = 70 μm, width W1 of pattern 2 mm = 2, width of groove W2 = 0 Each cell stack was prepared to have a thickness of 5 mm and an inner layer thickness H3 of 5 μm to 250 μm. In each cell stack, a crack is generated from the bottom end of the groove, and the tip of the crack reaches the surface of the frame and the interconnector. The crack is omitted in FIG. In addition, a cell stack for comparison was prepared in which the bottom of the groove reached the surface of the frame and the interconnector (that is, H3 = 0 μm) and there was no crack.

  Next, air was supplied to the cathode of each cell stack at 1 L / min from the outside along the in-plane direction of the cathode under an environment of 700 ° C., and held for 10000 hours. At this time, air passes through a pipe made of SUS310 maintained at 700 ° C., and then reaches the cathode. Thus, the Cr component was mixed in the air reaching the cathode. After holding for 10000 hours, the temperature was lowered and a single cell was taken out from the cell stack. The cell cross section of the unit cell taken out was polished to make it possible to observe the cross section of the cathode. The composition of the cross section of the cathode was analyzed by SEM-EDS to measure the Cr concentration. The above results are summarized in Table 1 together with the details of the collection layer of each cell stack.

  According to Table 1, it was confirmed that the thickness of the inner layer including the crack in the trapping layer is preferably 5 μm or more and 250 μm or less from the viewpoint of securing the trapping effect of the trapping layer.

(Experimental example 3)
In the same manner as in Experimental Example 2, the width W1 of the pattern portion is 2 mm, the width W2 of the groove portion is 0.5 mm, and the total thickness H1 of the collection layer, the thickness of the outer layer in the collection layer (depth of groove) H2, the inner layer Each cell stack was manufactured by changing the thickness H3 of. And the presence or absence of generation | occurrence | production of the crack by heat processing at the time of formation of a collection layer and the presence or absence of peeling of a collection layer was investigated. The results are summarized in Table 2.

  According to Table 2, when satisfying the relation of the thickness H3 of the inner layer <the thickness H2 of the outer layer, it was confirmed that the heat treatment tends to generate a crack extending in the thickness direction of the trapping layer from the bottom end of the groove by heat treatment . Moreover, it was confirmed that peeling of a collection layer is not seen, either, when the above-mentioned relation is fulfilled. In addition, when it investigated about the case where H1 = 100 micrometers, H2 = 20 micrometers, and H3 = 80 micrometers, peeling of the collection layer was seen in part. Similarly, when investigation was made on the case of H1 = 100 μm, H2 = 5 μm, H3 = 95 μm, there is a tendency that it is difficult to generate a crack from the end on the bottom side of the groove and also peeling of the trapping layer Some were seen.

(Experimental example 4)
In the same manner as in Experimental Example 2, the thickness of the outer layer (the depth of the groove) H2 = 70 μm, the thickness H3 of the inner layer in the collection layer H3 = 30 μm, the width W1 of the pattern portion and the width W2 of the groove are changed to make each cell stack Was produced. Then, during heat treatment at the time of formation of the trapping layer, the presence or absence of a crack generated from a portion other than the groove portion was investigated. The results are shown in Table 3.

  According to Table 3, the generation of cracks from the groove is promoted during heat treatment by satisfying the relationship of width W2 of the groove W <width W1 of the pattern W, 0.05 ≦ width W2 of the groove W1, and parts other than the groove It was confirmed from the above that the crack was less likely to occur.

  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.

1 Solid Oxide Fuel Cell Stack 2 Single Cell 21 Anode 22 Solid Electrolyte Layer 23 Cathode 3 Stacked Metal Material 4 Collection Layer A Oxidizer Gas

Claims (14)

A plurality of unit cells (2) comprising an anode (21), a solid electrolyte layer (22) and a cathode (23);
A stack metal material (3, 31, 32) used to stack a plurality of the above single cells;
A trap which is formed on the surface of the stack metal member facing the oxidant gas (A) supplied to the cathode, and collects poisonous substances contained in the oxidant gas and poisoning the cathode. It has a stratum (4),
The trapping layer has a stress relieving structure for relieving a stress generated at an interface between the trapping layer and the stack forming metal material due to a thermal expansion difference between the trapping layer and the stack forming metal material. Solid oxide fuel cell stack (1). The collection layer contains a conductive oxide,
The conductive oxide is
ACoO ₃ , wherein A is at least two elements selected from the group consisting of La, Sm and Sr, and the chemical composition ratio of the two selected elements is a total of 1; The solid oxide fuel cell stack according to claim 1, comprising: The solid oxide fuel cell stack according to claim 1, wherein a linear thermal expansion coefficient of the collection layer is 16 × 10 ⁻⁶ / K or more.   The solid oxide fuel cell stack according to any one of claims 1 to 3, wherein the stress relaxation structure includes a crack (41) extending in the thickness direction of the trapping layer.   The solid oxide fuel cell stack according to claim 4, wherein the stress relaxation structure includes a groove (40) formed in the thickness direction of the collection layer from the surface of the collection layer.   The solid oxide fuel cell stack according to claim 5, wherein a bottom of the groove is disposed in the collection layer.   The solid oxide fuel cell stack according to claim 6, wherein the stress relaxation structure comprises an outer layer (402) including the groove and an inner layer (401) including the crack.   The solid oxide fuel cell stack according to claim 6 or 7, wherein the crack extends from the bottom end of the groove toward the surface of the metal stack.   The solid oxide fuel cell stack according to any one of claims 5 to 8, wherein the groove is patterned.   The solid oxide fuel cell stack according to any one of claims 4 to 9, wherein the tip of the crack reaches the surface of the stack constituent metal material.   The solid oxide fuel cell stack according to any one of claims 4 to 10, wherein the crack is formed along a grain boundary in the trapping layer. The cathode contains a conductive oxide,
The solid oxide fuel cell stack according to claim 2, wherein the conductive oxide of the collection layer is made of the same material as the conductive oxide of the cathode.   The solid oxide fuel cell stack according to any one of claims 1 to 12, wherein the metal material of the stack is made of oxidation resistant metal. The solid oxide fuel cell stack according to any one of claims 1 to 13, wherein a linear thermal expansion coefficient of the stack-constituting metal material is less than 16 ^10-6 / K.

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