Manufacturing method for solid oxide fuel cell

Abstract

To provide a manufacturing method for a solid oxide fuel cell capable of suppressing cracking of an electrolyte layer and degradation of an air electrode layer.SOLUTION: The manufacturing method for a solid oxide fuel cell includes a stacking step and an air electrode forming step for forming an air electrode layer by firing an air electrode precursor layer. The air electrode formation step includes a closed space formation step for forming a fuel electrode closed space and an air electrode closed space, and a firing step for firing the air electrode precursor layer while supplying a reducing gas to the fuel electrode closed space and supplying an oxidizing gas containing oxygen to the air electrode closed space.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a solid oxide fuel cell. [Background technology]

[0002] Known solid oxide fuel cells (SOFCs) use a stainless steel metal support layer with a porous structure. The metal support layer is sometimes called a metal support or metal support. For example, Patent Document 1 (JP 2008-502113 A) discloses a specific SOFC cell having a metal support material, an active anode layer with a specific configuration, an electrolyte layer, an active cathode layer, and a cathode current collector plate.

[0003] During the manufacture of a solid oxide fuel cell having a metal support layer, an air electrode layer may be formed by firing. For example, an air electrode precursor layer, which serves as a precursor of the air electrode layer, is formed on a laminate having a metal support layer, a fuel electrode layer, and an electrolyte layer. After the air electrode precursor layer is formed, the laminate is fired to form the air electrode layer. The aforementioned Patent Document 1 also describes that the cathode (air electrode) is sintered in situ within the stack. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2008-502113 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the air cathode layer is fired in an oxygen atmosphere, the stainless steel metal support layer may expand due to oxidation, which may stretch the electrolyte layer and cause it to crack.

[0006] On the other hand, if the firing process is performed in an environment with a low oxygen partial pressure (e.g., in an N2 atmosphere), the air electrode layer is prone to deterioration. Air electrode layers are often formed from oxides with a perovskite structure. When such an air electrode layer is fired under a low oxygen partial pressure, phase separation of the metal oxide may occur. This phase separation can cause deterioration of the air electrode layer. Specifically, it can cause a decrease in the activity and durability of the air electrode layer as an electrode.

[0007] Therefore, an object of the present invention is to provide a method for manufacturing a solid oxide fuel cell that can suppress cracking of the electrolyte layer and deterioration of the air electrode layer. [Means for solving the problem]

[0008] In one aspect, a method for producing a solid oxide fuel cell according to the present invention includes a laminate fabrication step of fabricating a laminate having a configuration in which a metal support layer, an anode layer, an electrolyte layer, and a cathode precursor layer are laminated in this order, and a cathode formation step of firing the cathode precursor layer to form an cathode layer. The metal support layer is porous and formed from a material containing stainless steel. The cathode formation step includes a closed space formation step of forming an anode closed space including the anode layer and the metal support layer, and an cathode closed space including the cathode precursor layer, and a firing step of firing the cathode precursor layer while supplying a reducing gas to the anode closed space and an oxidizing gas containing oxygen to the cathode closed space. [Effects of the Invention]

[0009] According to the present invention, a method for producing a solid oxide fuel cell is provided that can suppress cracking of the electrolyte layer and deterioration of the air electrode layer. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a solid oxide fuel cell according to an embodiment. [Figure 2] FIG. 2 is a flowchart showing a method for manufacturing a solid oxide fuel cell according to an embodiment. [Figure 3] FIG. 3 is a schematic diagram showing an example of a method for forming the anode closed space and the cathode closed space. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of the laminate in the first modification. [Figure 5] FIG. 5 is a schematic diagram showing the configuration of a laminated body in Modification 2. As shown in FIG. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of a laminated body in Modification 3. In FIG. [Figure 7] FIG. 7 is a schematic diagram showing the configuration of a firing jig and a laminate in the fourth modification. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] (1) Solid oxide fuel cell Fig. 1 is a schematic cross-sectional view showing a solid oxide fuel cell 1 according to this embodiment. Fig. 1 shows the configuration corresponding to one cell in the solid oxide fuel cell 1.

[0013] 1, a solid oxide fuel cell 1 includes a metal support layer 2, a fuel electrode layer 3, an electrolyte layer 4, a cathode layer 5, a current collecting bonding layer 6, and an interconnector 7. These are stacked in this order along the stacking direction. A dense portion 8 is provided on the outer periphery of the metal support layer 2 and the fuel electrode layer 3.

[0014] The metal support layer 2 has a porous structure. The metal support layer 2 is made of stainless steel. Because of its porous structure, the metal support layer 2 is gas permeable.

[0015] The fuel electrode layer 3 is also porous. This allows gas to enter the fuel electrode layer 3. There are no particular limitations on the material of the fuel electrode layer 3. For example, the fuel electrode layer 3 can be made of SUS, stabilized zirconia (SSZ), or the like.

[0016] The electrolyte layer 4 has a dense structure. Because of the dense structure, the electrolyte layer 4 blocks gas. The material of the electrolyte layer 4 is not particularly limited. The electrolyte layer 4 can be formed from, for example, stabilized zirconia (SSZ) and gadolinia-doped ceria (GDC).

[0017] The air electrode layer 5 is formed of a material containing an oxide, such as lanthanum strontium cobalt composite oxide (LSC) and lanthanum strontium cobalt iron oxide (LSCF).

[0018] Preferably, the air electrode layer 5 has a crystalline structure having a perovskite structure. More preferably, 80 mass % or more of the air electrode layer 5 has a crystalline structure having a perovskite structure. Adoption of such a configuration improves the durability of the air electrode layer 5. An air electrode layer 5 having a crystalline structure in which 80 mass % or more has a perovskite structure can be obtained, for example, by adopting the manufacturing method described below.

[0019] As described above, the dense portion 8 is provided on the outer periphery of the metal support layer 2 and the fuel electrode layer 3. The dense portion 8 is provided over the entire outer periphery of the metal support layer 2 and the fuel electrode layer 3 in the thickness direction. Because the dense portion 8 is dense, it has the function of blocking gas. The provision of the dense portion 8 prevents gas present in the metal support layer 2 and the fuel electrode layer 3 from leaking from the side surfaces.

[0020] The dense portion 8 contacts the outer periphery of the electrolyte layer 4. Specifically, the outer periphery of the electrolyte layer 4 is located on the dense portion 8. As a result, part of the upper surface (the surface on the air electrode layer 5 side) of the dense portion 8 contacts the outer periphery of the electrolyte layer 4. In other words, no gap exists between the electrolyte layer 4 and the dense portion 8. This configuration also prevents gas present in the metal support layer 2 and the fuel electrode layer 3 from leaking from the gap between the dense portion 8 and the electrolyte layer 4.

[0021] In the following description, the part of the dense portion 8 that is provided on the outer periphery of the metal support layer 2 is referred to as a metal support layer dense portion 8-1. Also, the part of the dense portion 8 that is provided on the outer periphery of the fuel electrode layer 3 is referred to as a fuel electrode layer dense portion 8-2.

[0022] The metal support layer dense portion 8-1 and the anode layer dense portion 8-2 may each have a structure dense enough to block gas, and their specific structures are not particularly limited. For example, the metal support layer dense portion 8-1 can be formed of dense stainless steel. Alternatively, the dense portion 8 may be a portion densified by filling with a filler. Examples of fillers include those containing at least one element selected from the group consisting of K, Na, Ca, Mg, Al, B, Si, Zr, Ce, and Y. More specifically, examples of fillers include glass materials to which an additive containing at least one element selected from the group consisting of K, Na, Ca, Mg, Al, B, Si, Zr, Ce, and Y has been added. The filler may be disposed so as to cover the side surfaces of the metal support layer 2 and the anode layer 3, thereby forming the dense portions 8 on the side surfaces of the metal support layer 2 and the anode layer 3.

[0023] When viewed along the stacking direction, the outer peripheral edge of the dense portion 8 is located outside the outer peripheral edge of the electrolyte layer 4. Therefore, part of the upper surface of the dense portion 8 is not covered by the electrolyte layer 4 and is exposed. As will be described in detail later, this exposed portion can be used to restrain (fix) the stack in the dense portion 8 during manufacturing. By providing the exposed portion, the stack can be restrained without applying force to the electrolyte layer 4, which is prone to cracking.

[0024] The current collecting bonding layer 6 is provided to bond the interconnector 7 to the air electrode layer 5. The current collecting bonding layer 6 is made of a conductive material.

[0025] The interconnector 7 is a member that separates the cells from each other. Although not shown, other cells of the solid oxide fuel cell 1 are stacked on the interconnector 7.

[0026] The above is the configuration of the solid oxide fuel cell 1 according to this embodiment. In the above-described solid oxide fuel cell 1, the metal support layer 2 is provided only on one side (the fuel electrode layer 3 side) of the electrolyte layer 4. Therefore, the solid oxide fuel cell 1 can be said to be a so-called one-sided metal support type solid oxide fuel cell 1.

[0027] (2) Manufacturing method for solid oxide fuel cells Next, a method for manufacturing a solid oxide fuel cell will be described. Fig. 2 is a flowchart showing the method for manufacturing a solid oxide fuel cell according to this embodiment. Schematically, this manufacturing method includes a step of fabricating a stack (step S1), a step of forming an air electrode (step S2), and a current collector bonding step (step S3). Each step will be described below.

[0028] (Step S1) Fabrication of a laminate First, a laminate including a metal support layer 2, a fuel electrode layer 3, an electrolyte layer 4, and a dense portion 8 is formed. Then, an air electrode precursor layer is formed on this laminate to obtain a laminate. The air electrode precursor layer is a layer that serves as a precursor to the air electrode layer 5. The air electrode precursor layer is fired in step S2, which will be described later, to become the air electrode layer 5. In other words, the air electrode precursor layer can be considered a layer formed from a green sheet.

[0029] The methods for forming the metal support layer 2, the fuel electrode layer 3, and the electrolyte layer 4 are not particularly limited. Each layer can be obtained, for example, by preparing a green sheet and firing it in a reducing gas atmosphere. For example, a green sheet for the metal support layer 2, a green sheet for the fuel electrode layer 3, and a green sheet for the electrolyte layer 4 are prepared and stacked. The resulting structure is then fired all at once. This allows for a structure in which the metal support layer 2, the fuel electrode layer 3, and the electrolyte layer 4 are stacked. Alternatively, firing does not necessarily have to be performed all at once, and may be performed each time each layer is stacked. For example, first, a green sheet for the metal support layer 2 is prepared and fired to form the metal support layer 2. Next, a green sheet for the fuel electrode layer 3 is stacked on the metal support layer 2 and fired. This forms the fuel electrode layer 3 on the metal support layer 2. Furthermore, a green sheet for the electrolyte layer 4 is stacked on the fuel electrode layer 3 and fired. This forms the electrolyte layer 4 on the fuel electrode layer 3. This method also makes it possible to obtain a structure in which the metal support layer 2, the fuel electrode layer 3, and the electrolyte layer 4 are laminated.

[0030] There is also no particular limitation on the method for forming the dense portion 8. For example, when green sheets for the metal support layer 2 and the fuel electrode layer 3 are produced, the dense portion 8 can be formed by producing the green sheets under conditions that prevent voids from being formed only in the outer periphery. Alternatively, the dense portion 8 can be formed by first producing the metal support layer 2 and the fuel electrode layer 3 and then filling the outer periphery with a filler or the like.

[0031] (Step S2) Formation of the air electrode The air electrode precursor layer is then fired to form the air electrode layer 5. This process includes a closed space formation step (step S2-1) and a firing step (step S2-2). In the closed space formation step (step S2-1), an anode closed space containing the anode layer 3 and the metal support layer 2, and an air electrode closed space containing the air electrode precursor layer are formed. In the firing step (step S2-2), a reducing gas (e.g., a hydrogen-containing gas) is supplied to the anode closed space, and the air electrode precursor layer is fired in a state where an oxidizing gas containing oxygen is supplied to the air electrode closed space.

[0032] According to this method, the metal support layer 2 is in a reducing gas atmosphere and is therefore less likely to be oxidized. This suppresses expansion of the metal support layer 2 due to oxidation. The expanded metal support layer 2 is less likely to pull on the electrolyte layer 4. As a result, cracks in the electrolyte layer 4 are prevented.

[0033] On the other hand, the air electrode precursor layer is fired in an oxidizing gas atmosphere. Unlike firing in an environment with a low oxygen partial pressure (a reducing gas atmosphere), phase separation of the metal oxide is unlikely to occur. Because phase separation is suppressed, deterioration of the resulting air electrode layer 5 is suppressed.

[0034] That is, in this step, the air electrode precursor layer is fired in a state where the air electrode precursor layer and the metal support layer 2 are present in different atmospheres. As a result, it is possible to prevent cracking of the electrolyte layer 4 and suppress deterioration of the air electrode layer 5.

[0035] The above is an outline of this process. Next, this process will be described in more detail with reference to an example.

[0036] (Step S2-1: Formation of a closed space) 3 is a schematic diagram showing an example of a method for forming the anode closed space 11 and the cathode closed space 10. An example of a method for forming the anode closed space 11 and the cathode closed space 10 will be described with reference to FIG.

[0037] 3, a firing jig 9 and a gasket 12 are used to form an anode closed space 11 and an air electrode closed space 10. By placing the gasket 12 and a laminate 16 in the firing jig 9, the anode closed space 11 and the air electrode closed space 10 are formed.

[0038] Specifically, the firing jig 9 has a first member 9-1 and a second member 9-2. The first member 9-1 and the second member 9-2 are configured to be fastened together with fastening members such as screws. The gasket 12 and the laminate 16 are sandwiched and fixed between the first member 9-1 and the second member 9-2.

[0039] More specifically, a gasket 12 is disposed on the second member 9-2. The gasket 12 is frame-shaped. A laminate 16 is disposed on the gasket 12. The laminate 16 is placed on the gasket 12 so that the metal support layer 2 faces the gasket 12. The laminate 16 is also disposed on the gasket 12 so that the dense portion 8 is positioned on the frame of the gasket 12. The center of the metal support layer 2 is positioned above the opening of the gasket 12. This forms a space surrounded by the electrolyte layer 4, the dense portion 8, the gasket 12, and the second member 9-2. This space functions as the anode closed space 11. The second member 9-2 is provided with a flow path 14 having a valve. A reducing gas can be supplied to the anode closed space 11 via the flow path 14.

[0040] The first member 9-1 is placed on the second member 9-2 so as to sandwich the gasket 12 and the laminate 16. The first member 9-1 has a shape that forms an enclosed space as the air electrode closed space 10 on the air electrode precursor layer 5' side of the electrolyte layer 4. The first member 9-1 is provided with a flow path 13 for supplying an oxidizing gas to the air electrode closed space 10. A valve is provided in the flow path 13. The oxidizing gas can be supplied to the air electrode closed space 10 via the flow path 13.

[0041] By using the firing jig 9 and gasket 12 having the above-described configuration, the air electrode closed space 10 and the anode closed space 11 can be formed. A reducing gas can be supplied to the anode closed space 11, and an oxidizing gas can be supplied to the air electrode closed space 10. In the laminate 16, the electrolyte layer 4 and the dense portion 8 are in contact with each other. Therefore, the reducing gas supplied to the anode closed space 11 does not leak to the air electrode closed space 10 through a gap between the electrolyte layer 4 and the dense portion 8. Furthermore, the oxidizing gas supplied to the air electrode closed space 10 does not leak to the anode closed space 11. Therefore, the air electrode precursor layer 5′ can be fired in a state where the metal support layer 2 is in a reducing gas atmosphere and the air electrode precursor layer 5′ is in an oxidizing gas atmosphere.

[0042] 3, the first member 9-1 has a portion that covers the outer surface of the dense portion 8. This more reliably prevents gas from leaking from the side of the dense portion 8.

[0043] In the example shown in FIG. 3 , the first member 9-1 has a portion that contacts the exposed portion (portion protruding from the electrolyte layer 4) on the upper surface of the dense portion 8. As a result, at least a portion of the dense portion 8 is sandwiched and fixed between the gasket 12 and the first member 9-1 in the stacking direction. With this configuration, the stack 16 can be constrained by applying a constraining pressure to the dense portion 8. There is no need to apply a constraining pressure to the electrolyte layer 4 to fix the stack 16. The electrolyte layer 4 is often made of a material that cracks easily. Therefore, when a constraining pressure is applied to the electrolyte layer 4, the electrolyte layer 4 may crack. However, by constraining the stack 16 at the dense portion 8, there is no need to apply a constraining pressure to the electrolyte layer 4, and therefore cracking of the electrolyte layer 4 during constraining can be prevented.

[0044] Furthermore, by using a firing jig 9 having a configuration as shown in Fig. 3, the dense portion 8 is pressurized. Specifically, the firing jig 9 and the gasket 12 pressurize the dense portion 8 in the stacking direction. When the dense portion 8 is pressurized, the gas barrier performance of the dense portion 8 is further improved. As a result, gas leakage between the anode closed space 11 and the cathode closed space 10 can be more reliably prevented.

[0045] (Step S2-2: Regarding the baking process) Next, step S2-2 (firing step) will be described. The firing temperature in step S2-2 is higher than the operating temperature of the solid oxide fuel cell 1 (for example, 500 to 700°C). The firing temperature is, for example, 750°C or higher, preferably 800 to 900°C. Firing at such a temperature allows the air electrode precursor layer 5' to be sufficiently sintered. Note that firing at such a high temperature usually tends to cause oxidation and expansion of the metal support layer 2. It also tends to cause oxide phase separation in the air electrode layer 5. However, according to this embodiment, as described above, the metal support layer 2 and the air electrode precursor layer 5' are fired in different atmospheres, and therefore, even at a high firing temperature, oxidation and expansion of the metal support layer 2 and oxide phase separation in the air electrode layer 5 can be suppressed.

[0046] In this step, the air electrode precursor layer 5' is fired in an oxidizing gas atmosphere. As a result, phase separation of the metal oxide phase is suppressed. As a result, the air electrode layer 5 has a structure in which 80 mass % or more of the crystal structure has a perovskite structure. In other words, the amount of impurity components having structures other than the perovskite structure is reduced. The reduced amount of impurity components can improve the durability of the air electrode layer 5.

[0047] (Step S3) Current collector joining process Next, the current collecting bonding step will be described. After the firing step (step S2-2), the interconnector 7 is connected to the air electrode layer 5 via the current collecting bonding layer 6. For example, a conductive material is laminated on the air electrode layer 5 as the current collecting bonding layer 6, and the interconnector 7 is further placed on the current collecting bonding layer 6. Then, a heat treatment is performed. This allows the interconnector 7 to be connected to the air electrode layer 5.

[0048] The heat treatment in this step can be carried out in a normal atmosphere (air). However, when heat treatment is carried out in this step, the heating temperature is preferably lower than the firing temperature in step S2-2. For example, the heating temperature is 700 to 1000°C. At such a heating temperature, the metal support layer 2 is unlikely to oxidize even in an oxygen-containing atmosphere. Therefore, cracks in the electrolyte layer 4 due to oxidative expansion of the metal support layer 2 are unlikely to occur.

[0049] The method for manufacturing a solid oxide fuel cell according to this embodiment has been described above. As described above, according to this embodiment, the air electrode precursor layer 5' is fired under conditions in which the metal support layer 2 is placed in a reducing gas atmosphere and the air electrode precursor layer 5' is placed in an oxidizing gas atmosphere. This prevents oxidation of the metal support layer 2 and also suppresses oxide phase separation in the air electrode layer 5. As a result, cracking of the electrolyte layer 4 due to oxidative expansion of the metal support layer 2 is prevented, and deterioration of the air electrode layer 5 due to oxide phase separation is also suppressed.

[0050] (Variation 1) Next, Modification 1 of this embodiment will be described. Fig. 4 is a schematic diagram showing the configuration of stack 16 in this modification, and is a schematic diagram showing the configuration in step S2-1 (forming the air electrode). Note that detailed description will be omitted regarding the fact that the same configuration as the example shown in Fig. 3 can be adopted.

[0051] As shown in FIG. 4 , in this modification, the dense portion 8 is provided only in the outer periphery of the metal support layer 2. That is, the dense portion 8 is not provided in the outer periphery of the fuel electrode layer 3. As the dense portion 8, only the metal support layer dense portion 8-1 is provided. The electrolyte layer 4 is provided so as to cover the side surface of the fuel electrode layer 3. When viewed along the stacking direction, the outer periphery edges of the metal support layer dense portion 8-1 and the electrolyte layer 4 are located outside the outer periphery edge of the fuel electrode layer 3. The outer periphery of the electrolyte layer 4 and the metal support layer dense portion 8-1 are in contact with each other so that the reducing gas in the fuel electrode closed space 11 does not leak into the air electrode closed space 10.

[0052] Furthermore, when viewed along the stacking direction, the outer peripheral edge of the metal support layer dense portion 8-1 is located outside the outer peripheral edge of the electrolyte layer 4. As a result, a portion exposed from the electrolyte layer 4 is provided on the upper surface of the metal support layer dense portion 8-1. The first member 9-1 contacts this exposed portion. As a result, the stack 16 is sandwiched and restrained between the first member 9-1 and the gasket 12 at the metal support layer dense portion 8-1.

[0053] Even with the configuration of this modified example, the same effects as those of the example shown in Figure 3 can be achieved. That is, by placing the laminate 16 in the firing jig 9, the air electrode closed space 10 and the anode closed space 11 can be formed. Therefore, the air electrode precursor layer 5' can be fired in a state where the metal support layer 2 and the air electrode precursor layer 5' are placed in different atmospheres. Furthermore, the laminate 16 can be constrained in the dense portion 8 without applying a constraining pressure to the electrolyte layer 4. As a result, cracking of the electrolyte layer 4 due to the constraining pressure can be prevented.

[0054] (Variation 2) Next, a second modification of the present embodiment will be described. Fig. 5 is a schematic diagram showing the configuration of the laminate 16 in this modification, and is a schematic diagram showing the configuration in step S2-1 (forming the air electrode). Note that detailed description will be omitted regarding the fact that the same configuration as the examples shown in Figs. 3 and 4 can be adopted.

[0055] In this modification, too, in step S2-1, the laminate 16 is placed in the firing jig 9. At this time, a sealing material 15 is filled between the outer peripheral surface of the dense portion 8 and the firing jig 9. By filling the sealing material 15, gas leakage through the dense portion 8 is more reliably prevented. As a result, the air electrode closed space 10 is more likely to be maintained in an oxidizing gas atmosphere, and the anode closed space 11 is more likely to be maintained in a reducing gas atmosphere. This more reliably prevents cracking of the electrolyte layer 4 due to oxidative expansion of the metal support layer 2 and deterioration of the air electrode layer 5 due to phase separation of the oxide phase.

[0056] Note that, for example, a glass material is used as the sealing material 15. For example, the glass material to which an additive containing at least one element selected from the group consisting of K, Na, Ca, Mg, Al, B, Si, Zr, Ce, and Y is added is used.

[0057] (Variation 3) Next, Modification 3 will be described. Fig. 6 is a schematic diagram showing the configuration of the laminate 16 in this modification, and is a schematic diagram showing the configuration in step S2 (forming the air electrode). In this modification, the sealing material 15 is arranged so as to cover not only the outer peripheral surface of the dense portion 8 but also the top and bottom surfaces in the stacking direction. In other respects, the same configuration as Modification 2 can be adopted.

[0058] According to this modification, since the sealing material is also disposed on the upper and lower surfaces of the dense portion 8, leakage of gas through the dense portion 8 is more reliably prevented.

[0059] (Variation 4) Next, Modification 4 will be described. In this modification, the configuration of the firing jig 9 is improved. FIG. 7 is a schematic diagram showing the configuration of the firing jig 9 and the laminate 16 in this modification. In this modification, a space for arranging a plurality of laminates 16 is provided in one firing jig 9. That is, in this modification, in the closed space forming step (step S2-1), a plurality of laminates 16 are arranged in one firing jig 9. Then, in the firing step (step S2-2), the plurality of laminates 16 are fired all at once.

[0060] According to this modification, a plurality of laminates 16 are fired at once, thereby improving production efficiency.

[0061] The present invention has been described above with reference to the embodiments and modifications. The main configurations and effects of the present invention are summarized below as supplementary notes.

[0062] (Appendix 1) The method for producing a solid oxide fuel cell includes: a laminate fabrication step (S1) of fabricating a laminate 16 having a configuration in which a metal support layer 2, an anode layer 3, an electrolyte layer 4, and an air electrode precursor layer 5' are laminated in this order; and a cathode formation step (S2) of forming an air electrode layer by firing the air electrode precursor layer, wherein the metal support layer 2 has a porous structure and is formed from a material containing stainless steel. The cathode formation step includes a closed space formation step (S2-1) of forming an anode closed space 11 including the anode layer and the metal support layer, and an air electrode closed space 10 including the air electrode precursor layer; and a firing step (S2-2) of firing the air electrode precursor layer in a state in which a reducing gas is supplied to the anode closed space and an oxidizing gas containing oxygen is supplied to the air electrode closed space.

[0063] According to this method, the air electrode precursor layer 5' is fired in a state where the metal support layer 2 is in a reducing gas atmosphere and the air electrode precursor layer 5' is in an oxidizing gas atmosphere. This prevents oxidation of the metal support layer 2 and cracking of the electrolyte layer 4. In addition, phase separation of oxides in the air electrode layer 5 is prevented, preventing deterioration of the air electrode layer 5.

[0064] (Appendix 2) The manufacturing method according to Appendix 1, wherein a dense portion 8 having a dense structure is provided on the outer periphery of the metal support layer and the fuel electrode layer, and the dense portion is in contact with the outer periphery of the electrolyte layer so as to prevent the reducing gas in the closed fuel electrode space from leaking to the closed air electrode space.

[0065] According to this method, since the dense portion 8 is provided, the movement of gas between the air electrode closed space and the fuel electrode closed space can be more reliably prevented.

[0066] (Appendix 3) The manufacturing method according to Appendix 2, wherein the firing step includes a step of pressurizing the dense portion.

[0067] According to this method, the dense portion is pressurized, so that the gas can be more reliably blocked in the dense portion.

[0068] (Appendix 4) A manufacturing method as described in Appendix 3, wherein the closed space forming step includes a step of arranging a gasket 12 and a laminate 16 so that the anode closed space and the cathode closed space are formed in a firing jig 9, the laminate is arranged so that a portion of the dense portion is sandwiched between the firing jig and the gasket in the stacking direction, and the step of pressurizing the dense portion includes a step of pressurizing the dense portion in the stacking direction using the firing jig and the gasket.

[0069] According to this method, the dense portion can be pressurized, and the gas can be more reliably blocked in the dense portion.

[0070] (Appendix 5) A manufacturing method according to any one of Appendices 2 to 4, wherein a portion of the dense portion provided on the outer periphery of the metal support layer is referred to as the metal support layer dense portion 8-1, and the metal support layer dense portion 8-1 is formed from dense stainless steel.

[0071] According to this method, the dense portion of the metal support layer can be formed from dense stainless steel.

[0072] (Appendix 6) A manufacturing method according to any one of Appendices 2 to 4, wherein a portion of the dense portion provided on the outer periphery of the metal support layer is referred to as the metal support layer dense portion, and the metal support layer dense portion is filled with a filler, and the filler contains at least one element selected from the group consisting of K, Na, Ca, Mg, Al, B, Si, Zr, Ce, and Y.

[0073] According to this method, the dense portion of the metal support layer can be formed by the filler.

[0074] (Appendix 7) 7. The manufacturing method according to any one of Appendices 2 to 6, wherein the closed space forming step includes a step of arranging the laminate in a firing jig so that an anode closed space and an air cathode closed space are formed, and the arranging step includes a step of filling a sealant between the outer peripheral surface of the dense portion and the firing jig.

[0075] This method can prevent gas from leaking through the gap between the dense portion and the combustion jig.

[0076] (Appendix 8) A manufacturing method according to Appendix 1, wherein a metal support layer dense portion having a dense structure is provided at the outer periphery of the metal support layer, and when viewed along the stacking direction, the outer periphery of the metal support layer dense portion and the electrolyte layer are located outside the outer periphery of the fuel electrode layer, and the outer periphery of the electrolyte layer and the metal support layer dense portion are in contact with each other so that reducing gas in the closed space of the fuel electrode does not leak toward the closed space of the air electrode.

[0077] According to this method, no gaps are formed between the electrolyte layer and the dense portion, so that gas movement between the anode closed space and the cathode closed space can be more reliably prevented.

[0078] (Appendix 9) A manufacturing method according to any one of Appendices 1 to 8, wherein the closed space forming step includes a step of placing a plurality of laminates in one firing jig, and in the firing step, the plurality of laminates are fired all at once.

[0079] According to this method, a plurality of laminates can be fired at once, thereby improving productivity.

[0080] (Appendix 10) 10. The manufacturing method according to any one of Appendices 1 to 9, wherein the firing step includes a step of firing so that the content of a crystal structure having a perovskite structure in the air electrode layer is 80 mass % or more.

[0081] This method can improve the durability of the air electrode layer.

[0082] (Appendix 11) The manufacturing method according to any one of Appendices 1 to 10, further comprising, after the air electrode-forming step, a current collecting bonding step of bonding an interconnector onto the air electrode layer by heating via a current collecting bonding layer, wherein the heating temperature in the current collecting bonding step is lower than the firing temperature in the firing step.

[0083] According to this method, the interconnector can be bonded to the air cathode layer without oxidizing the metal support layer 2. [Explanation of symbols]

[0084] 1 Solid oxide fuel cell, 2 Metal support layer, 3 Fuel electrode layer, 4 Electrolyte layer, 5 Air electrode layer, 6 Current collecting bonding layer, 7 Interconnector, 8 Dense portion, 9 Firing jig, 10 Air electrode closed space, 11 Fuel electrode closed space, 12 Gasket, 13 Flow path, 14 Flow path, 15 Sealing material, 16 Laminate

Claims

1. a laminate fabrication step of fabricating a laminate having a configuration in which a metal support layer, an anode layer, an electrolyte layer, and an air cathode precursor layer are laminated in this order; a cathode forming step of forming an air electrode layer by firing the air electrode precursor layer; Including, the metal support layer has a porous structure and is formed from a material containing stainless steel; The air electrode forming step includes: a closed space forming step of forming an anode closed space including the anode layer and the metal support layer, and an air electrode closed space including the air electrode precursor layer; a firing step of firing the air electrode precursor layer in a state in which a reducing gas is supplied to the anode closed space and an oxidizing gas containing oxygen is supplied to the air electrode closed space; Contains, A method for manufacturing a solid oxide fuel cell.

2. The method of claim 1, a dense portion having a dense structure is provided in an outer periphery of the metal support layer and the fuel electrode layer, the dense portion is in contact with the outer periphery of the electrolyte layer so as to prevent the reducing gas in the anode closed space from leaking to the cathode closed space. Manufacturing method.

3. The manufacturing method according to claim 2, The firing step includes a step of pressurizing the dense portion. Manufacturing method.

4. The manufacturing method according to claim 3, the closed space forming step includes a step of arranging a gasket and the laminate in a firing jig so that the anode closed space and the cathode closed space are formed; the laminate is arranged so that a part of the dense portion is sandwiched between the firing jig and the gasket in the stacking direction, The step of pressurizing the dense portion includes a step of pressurizing the dense portion in the stacking direction by the firing jig and the gasket. Manufacturing method.

5. The manufacturing method according to claim 2, a portion of the dense portion provided on the outer periphery of the metal support layer is referred to as a metal support layer dense portion, the dense portion of the metal support layer is formed of dense stainless steel, Manufacturing method.

6. The manufacturing method according to claim 2, a portion of the dense portion provided on the outer periphery of the metal support layer is referred to as a metal support layer dense portion, a filler is filled in the dense portion of the metal support layer, The filler contains at least one element selected from the group consisting of K, Na, Ca, Mg, Al, B, Si, Zr, Ce, and Y. Manufacturing method.

7. The manufacturing method according to claim 2, the closed space forming step includes a step of arranging the laminate in a firing jig so that the anode closed space and the cathode closed space are formed; The placing step includes a step of filling a sealant between the outer peripheral surface of the dense portion and the firing jig. Manufacturing method.

8. The method of claim 1, a metal support layer dense portion having a dense structure is provided in an outer peripheral portion of the metal support layer, When viewed along the stacking direction, the dense portion of the metal support layer and the outer peripheral edge of the electrolyte layer are located outside the outer peripheral edge of the fuel electrode layer, the outer periphery of the electrolyte layer and the dense portion of the metal support layer are in contact with each other so as to prevent the reducing gas in the anode closed space from leaking to the cathode closed space. Manufacturing method.

9. The method of claim 1, the closed space forming step includes a step of arranging a plurality of the laminates in one firing jig, In the firing step, the plurality of laminates are fired at once. Manufacturing method.

10. The method of claim 1, the firing step includes a step of performing firing so that the content of a crystal structure having a perovskite structure in the air electrode layer becomes 80 mass % or more. Manufacturing method.

11. The method of claim 1, Furthermore, a current collecting bonding step of bonding an interconnector to the air electrode layer via a current collecting bonding layer by heating after the air electrode forming step; The heating temperature in the current collecting bonding step is lower than the firing temperature in the firing step. Manufacturing method.

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