Method for manufacturing an electric cell

Abstract

To provide a technique capable of densifying the end portion of a metal support layer by pressing without destroying an electrolyte layer. [Solution] A method for manufacturing an electric cell 1 that is an SOFC or SOEC, comprising the steps of: preparing a laminate having an electrolyte layer 2, a cathode electrode layer 3-1, an anode electrode layer 3-2, and a pair of metal support layers 4; and pressing the ends of the pair of metal support layers 4 to densify them, wherein the pressing step is carried out while the pair of metal support layers are heated.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electric cell. [Background technology]

[0002] Solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are devices that have roughly the same configuration. In this specification, SOFCs and SOECs are collectively referred to as "electric cells."

[0003] A double-sided metal-supported device is known as an electric cell. A double-sided metal-supported electric cell is an electric cell that uses a pair of metal support layers. Specifically, a double-sided metal-supported electric cell has an electrolyte layer, a cathode electrode layer, an anode electrode layer, and a pair of metal support layers. The cathode electrode layer and the anode electrode layer are arranged to sandwich the electrolyte layer. The pair of metal support layers are arranged on the outside of the cathode electrode layer and the anode electrode layer. The pair of metal support layers have a porous structure that allows the anode gas and the cathode gas to pass through, respectively.

[0004] During operation, gas is passed between the cathode electrode layer and the anode electrode layer and the outside through each metal support layer. Gas passing through each metal support layer may leak from the side. Densifying the ends of each metal support layer is one way to prevent gas leakage from the side.

[0005] In relation to the above, Patent Document 1 (JP 2010-534901 A) describes a fuel cell having a plate manufactured by powder metallurgy, the plate being manufactured into a single plate and having a porous substrate region, on top of which a layer of electrochemically active cells is attached, and further the plate having an airtight end region provided with a gas passage through which gas passes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2010-534901 Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors have considered pressing the edges of each metal support layer to densify them. However, during pressing, a molding load is also applied to the electrolyte layer. The molding load may destroy the electrolyte layer.

[0008] Therefore, an object of the present invention is to provide a technique that can densify the end portion of a metal support layer by pressing without destroying the electrolyte layer. [Means for solving the problem]

[0009] In one aspect, a method for manufacturing an electric cell according to the present invention is a method for manufacturing an electric cell that is an SOFC or SOEC. This manufacturing method includes the steps of: preparing a laminate having an electrolyte layer, a cathode electrode layer, an anode electrode layer, and a pair of metal support layers, the pair of metal support layers having a porous structure; and pressing ends of the pair of metal support layers to densify them. The pressing step is performed in a heated state. [Effects of the Invention]

[0010] According to the present invention, a technique is provided that can densify the edge of a metal support layer by pressing without destroying the electrolyte layer. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view that shows a schematic diagram of an electric cell. [Figure 2] FIG. 2 is a flow chart that schematically illustrates a method for manufacturing an electric cell according to an embodiment. [Figure 3]FIG. 3 is a flowchart illustrating a specific example of a method for manufacturing an electric cell according to an embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of the structure of the laminate in the pressing step. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a modified example of the pressing step. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a method for manufacturing an electric cell according to an embodiment of the present invention will be described with reference to the drawings. As described above, in this specification, the term "electric cell" collectively refers to SOFCs and SOECs. In this embodiment, a method for manufacturing an electric cell will be described using an SOFC as an example. However, the electric cell according to this embodiment may also be used as an SOEC.

[0013] (1) Electric cell configuration First, the configuration of an electric cell 1 manufactured by the manufacturing method according to this embodiment will be described. Fig. 1 is a cross-sectional view that schematically shows the electric cell 1. Fig. 1 shows the configuration of an end portion of the cell structure of the electric cell 1.

[0014] As shown in FIG. 1, the electric cell 1 has an electrolyte layer 2, a pair of electrode layers 3 (a cathode electrode layer 3-1 and an anode electrode layer 3-2), and a pair of metal support layers 4 (a cathode metal support layer 4-1 and an anode metal support layer 4-2). These are stacked in the stacking direction. Specifically, the cathode electrode layer 3-1 and the anode electrode layer 3-2 are arranged so as to sandwich the electrolyte layer 2. The cathode metal support layer 4-1 and the anode metal support layer 4-2 are arranged on the outer sides of the cathode electrode layer 3-1 and the anode electrode layer 3-2.

[0015] The electrolyte layer 2 is configured to be oxide ion conductive but gas impermeable. For example, the electrolyte layer 2 is formed of dense ceramics. Examples of ceramics include solid oxide ceramics. Examples of solid oxide ceramics include zirconia-containing materials. Examples of zirconia-containing materials include stabilized zirconia doped with yttria, neodymium oxide, samarium, gadolinium, scandium, etc. The thickness of the electrolyte layer 2 is, for example, 0.5 to 20 μm, preferably 1 to 10 μm.

[0016] The cathode electrode layer 3-1 is a portion that converts oxygen molecules contained in the cathode gas into oxide ions. For example, the cathode electrode layer 3-1 has porous conductive ceramics and a cathode catalyst supported on the conductive ceramics. The conductive ceramics are not particularly limited, but examples thereof include scandia-stabilized zirconia (SSZ). The thickness of the cathode electrode layer 3-1 is, for example, 0.3 to 50 μm, preferably 0.5 to 30 μm.

[0017] The anode electrode layer 3-2 is a part that reacts fuel such as hydrogen with oxide ions to generate electrons. The anode electrode layer 3-2 can also have a configuration similar to that of the cathode electrode layer 3-1. For example, the anode electrode layer 3-2 has porous conductive ceramics and an anode catalyst supported on the conductive ceramics. Examples of conductive ceramics include scandia-stabilized zirconia (SSZ). The thickness of the anode electrode layer 3-2 is, for example, 0.3 to 50 μm, preferably 0.5 to 30 μm.

[0018] A pair of metal support layers 4 are provided to support the electric cell 1. Each metal support layer 4 has a porous structure overall. For example, each metal support layer 4 is made of SUS.

[0019] Specifically, each metal support layer 4 has a central portion 5 and edge portions 6. The central portion 5 is a portion configured to be permeable to gas and has a porous structure. On the other hand, the edge portions 6 have a dense structure to prevent gas leakage. As will be described later, the edge portions 6 are densified by pressing. Therefore, the thickness of the edge portions 6 is smaller than the thickness of the central portion 5.

[0020] There is no particular limitation on the thickness of each metal support layer 4. For example, the thickness of each metal support layer 4 in the central portion 5 is 50 to 1000 μm, and preferably 100 to 500 μm.

[0021] The above is a schematic configuration of the electric cell 1 according to this embodiment. When this electric cell 1 is in operation, a cathode gas (oxygen-containing gas) is supplied to the cathode electrode layer 3-1 via the cathode metal support layer 4-1. An anode gas (fuel gas: for example, a hydrogen-containing gas) is supplied to the anode electrode layer 3-2 via the anode metal support layer 4-2. Then, in each electrode layer 3 (3-1 and 3-2), a reaction as a fuel cell proceeds, and power is generated. In each metal support layer 4, the end portion 6 has a dense structure, so gas does not leak from the side.

[0022] As mentioned above, the electric cell may be an SOEC. In this case, during operation, water vapor is supplied to the cathode electrode layer 3-1 via the cathode metal support layer 4-1, and hydrogen and oxygen ions are produced by an electrochemical reaction. Meanwhile, in the anode electrode layer 3-2, oxygen is produced from the oxygen ions via an electrochemical reaction, and the oxygen is extracted via the anode metal support layer 4-2. This causes water to be electrolyzed.

[0023] (2) Manufacturing method of electric cell Next, a method for manufacturing the electric cell having the above-described configuration will be described. In this embodiment, a method for forming the end portion 6 is devised.

[0024] 2 is a flowchart that schematically illustrates a method for manufacturing an electric cell according to this embodiment. In summary, the manufacturing method according to this embodiment includes a stack fabrication step (step S1) and a pressing step (step S2). In the stack fabrication step (S1), a stack is fabricated that includes an electrolyte layer, a cathode electrode layer, an anode electrode layer, and a pair of metal support layers. In the pressing step (S2), the ends of the pair of metal support layers are pressed to densify them.

[0025] Here, the pressing step (S2) is performed while the pair of metal support layers are heated. By pressing the ends of the pair of metal support layers in a heated state, the ends can be densified while preventing destruction of the electrolyte layer. If the ends of the metal support layers were pressed at room temperature, a large forming load would be required for densification. As a result, a large forming load would also be applied to the electrolyte layer. The electrolyte layer is made of, for example, ceramics, and is hard and brittle. Therefore, the electrolyte layer may be destroyed during pressing. In contrast, according to this embodiment, each metal support layer can be softened by heating. Therefore, the forming load required for densification can be reduced, and destruction of the electrolyte layer can be prevented.

[0026] The above is an outline of the manufacturing method according to this embodiment. Next, the manufacturing method according to this embodiment will be specifically described.

[0027] FIG. 3 is a flowchart showing a specific example of a method for manufacturing an electric cell according to this embodiment. The method for manufacturing an electric cell shown in FIG. 3 includes a laminate-forming step (S1), a pressing step S2 (S2-1 to S2-3), a firing step (S3), and a catalyst impregnation step (S4). The pressing step (S2) is performed at any timing after the laminate-forming step (S1). For example, the pressing step (S2) can be performed during the firing step (S2) (press A in FIG. 3). Alternatively, the pressing step (S2) can be performed between the firing step (S3) and the catalyst impregnation step (S4) (press B in FIG. 3). Alternatively, the pressing step (S2) can be performed after the catalyst impregnation step (S4) (press C in FIG. 3). The pressing step (S2) may be performed at multiple timings or only once.

[0028] Each step will be described in more detail below.

[0029] Step S1: Creating a laminate First, a laminate is produced. The method for producing the laminate is not particularly limited. For example, green sheets, which are precursors of each layer included in the electric cell, are produced. The green sheets can be obtained, for example, by preparing a slurry containing the constituent materials of each layer and applying it to a substrate. Next, the green sheets of each layer are stacked and integrated. For example, multiple green sheets can be integrated using a warm isostatic press (WIP) or the like. This produces a laminate. After the laminate is produced, a degreasing treatment or the like may be performed as necessary.

[0030] Step S3: Firing The laminate is then fired at a firing temperature of, for example, 900 to 1400°C, and preferably 1100 to 1300°C.

[0031] During firing, each metal support layer is in a heated state, and therefore, a pressing step (S2-1) may be carried out during the firing step.

[0032] After the calcination step (S3) is completed, a pressing step (S2-2) may be carried out before the catalyst impregnation step (S4).

[0033] Step S4: Catalyst impregnation After the firing step (S3), each electrode layer is impregnated with a slurry containing a catalyst. Specifically, the anode electrode layer is impregnated with a slurry containing an anode catalyst, and the cathode electrode layer is impregnated with a slurry containing a cathode catalyst. After impregnation, each electrode layer is subjected to a heat treatment.

[0034] After the catalyst impregnation step (S4), a pressing step (S2-3) may be carried out.

[0035] An electric cell can be obtained by the method described above. As described above, the pressing step (S2) can be carried out at any step after the laminate preparation (S1).

[0036] The heating temperature of the metal support layer in the pressing step (S2) may be any temperature that sufficiently softens the metal support layer. If the heating temperature is high, the metal support layer is more likely to soften and the deformation resistance is more likely to decrease. Therefore, the molding load required for densification can be further reduced, and destruction of the electrolyte layer can be more reliably prevented. Therefore, from the viewpoint of preventing destruction of the electrolyte layer, it is preferable that the heating temperature of the metal support layer is high.

[0037] For example, the heating temperature of the metal support layer in the pressing step is a temperature at which the deformation resistance of the metal support layer is 50% or less of that at room temperature (25°C). If the metal support layer is heated at such a temperature, destruction of the electrolyte layer can be more reliably prevented. The "temperature at which the deformation resistance of the metal support layer is 50% or less of that at room temperature" can be determined by measuring the relationship between strain and deformation resistance for each temperature.

[0038] More specifically, from the viewpoint of reducing the forming load, the heating temperature of the metal support layer is preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 750°C or higher.

[0039] On the other hand, if the heating temperature of the metal support layer in the pressing step is too high, oxidation of the metal support layer may proceed more than necessary. As a result, the metal support layer may deteriorate. Therefore, in order to prevent excessive oxidation, when the heating temperature of the metal support layer is high, it is preferable to perform the pressing step in a non-oxidizing atmosphere (for example, in a non-oxidizing furnace: an environment not containing oxygen). Specifically, when the heating temperature is 750°C or higher, it is preferable to perform the pressing step in a non-oxidizing atmosphere. Conversely, when the pressing step is performed in an oxygen-containing atmosphere (typically in air), it is preferable that the heating temperature be less than 750°C from the viewpoint of preventing excessive oxidation.

[0040] Furthermore, when the pressing step (S2) is performed after the catalyst impregnation step (S4) (see press C in FIG. 3), if the heating temperature is too high, the catalyst may deteriorate. Therefore, when the pressing step is performed after impregnation with the cathode catalyst and / or anode catalyst slurry, the heating temperature is preferably a temperature at which the catalyst does not deteriorate (for example, 600°C or lower).

[0041] In addition, when a heat treatment is performed in a step prior to the pressing step (S2), the pressing step (S2) may be performed using residual heat from the previous step. By using residual heat from the previous step, an additional heat treatment for the pressing step is not required. For example, when the pressing step (S2) is performed between the calcination step (S3) and the catalyst impregnation step (S4), it is preferable to perform the pressing step when the temperature of the metal support layer has dropped to the desired temperature after calcination.

[0042] Next, a specific pressing method in the pressing step (S2) will be described. Fig. 4 is a schematic cross-sectional view showing an example of the configuration of the laminate in the pressing step (S2). In the example shown in Fig. 4, a press die 7 is used to press so that the end 6 of the metal support layer 4 is compressed. The press die 7 is arranged so as to sandwich the end 6 of the metal support layer 4 in the stacking direction.

[0043] In the example shown in Fig. 4, the press die 7 has a shape such that the corners (see corner A in Fig. 4(b)) formed between the end portion 6 and the central portion 5 of each metal support layer 4 are curved. By adopting such a configuration, it is possible to prevent stress from concentrating on the metal support layer at the boundary portion between the central portion 5 and the end portion 6. This makes it possible to prevent the metal support layer 4 from cracking at the boundary portion.

[0044] 5 is a schematic cross-sectional view showing a modified example of the pressing step (S2). In this modified example, the press die 7 has a shape such that the side surface of the central portion 5 of each metal support layer 4 is an inclined surface. In addition, in FIG. 5, similar to the example shown in FIG. 4, the corner portion A has a shape such that it is a curved surface. By using such a press die 7, it is possible to more reliably prevent stress from concentrating at the boundary portion between the central portion 5 and the edge portion 6, and it is possible to more reliably prevent cracking of the metal support layer 4.

[0045] When the press molds shown in FIGS. 4 and 5 are used, a large press machine is not required, and the production line can be made compact.

[0046] [Note] Representative configurations and their effects included in the present invention will be summarized below as appendices.

[0047] (Appendix 1) A method for manufacturing an electric cell 1 that is an SOFC or SOEC, the method comprising the steps of: preparing a laminate having an electrolyte layer 2, a cathode electrode layer 3-1, an anode electrode layer 3-2, and a pair of metal support layers (4-1 and 4-2), the pair of metal support layers (4-1 and 4-2) having a porous structure; and pressing ends 6 of the pair of metal support layers (4-1 and 4-2) to densify them, the pressing being performed in a state where the pair of metal support layers are heated.

[0048] According to this method, the metal support layer can be softened by heating, which reduces the molding load required to densify the edge of the metal support layer and prevents the electrolyte layer from being destroyed.

[0049] (Appendix 2) The manufacturing method according to Appendix 1, wherein the heating temperature of the pair of metal support layers (4-1 and 4-2) in the pressing step is a temperature or higher at which the deformation resistance of the pair of metal support layers is 50% or less of that at room temperature.

[0050] According to this method, the molding load during pressing can be sufficiently reduced, and destruction of the electrolyte layer can be more reliably prevented.

[0051] (Appendix 3) 3. The manufacturing method according to claim 1, wherein the pressing step includes a step of pressing the ends in an atmospheric atmosphere, and the heating temperature of the pair of metal support layers in the step of pressing the ends in an atmospheric atmosphere is less than 750°C.

[0052] According to this method, it is possible to prevent excessive oxidation of the metal support layer and also to prevent destruction of the electrolyte layer.

[0053] (Appendix 4) The production method according to any one of Appendices 1 to 3, further comprising the step of impregnating the cathode electrode layer and / or the anode electrode layer with a slurry containing a catalyst, wherein the pressing step comprises the step of pressing the end portions after the step of impregnating with the slurry, and the heating temperature of the pair of metal support layers in the step of pressing the end portions after the step of impregnating with the slurry is 600°C or less.

[0054] According to this method, the heating temperature of the metal support layer is 600° C. or less, so that the deterioration of the catalyst can be prevented and the destruction of the electrolyte layer can be prevented.

[0055] (Appendix 5) 5. The manufacturing method according to any one of Appendices 1 to 4, wherein the pressing step includes a step of pressing the end portions in a non-oxidizing atmosphere, and the heating temperature of the pair of metal support layers in the step of pressing the end portions in a non-oxidizing atmosphere is 750°C or higher.

[0056] According to this method, the forming load during pressing can be more effectively reduced by heating to 750° C. or higher. In addition, by performing pressing in a non-oxidizing atmosphere, excessive oxidation of the metal support layer during pressing can be prevented.

[0057] (Appendix 6) A manufacturing method according to any one of Appendices 1 to 5, wherein the pressing step includes a step of pressing using a press mold so that ends of the pair of metal support layers are compressed, and the press mold has a shape such that corners formed between the ends of the pair of metal support layers and central portions of the pair of metal support layers are formed by curved surfaces, or a shape such that side surfaces of the central portions of the pair of metal support layers are inclined surfaces.

[0058] According to this method, it is possible to avoid the occurrence of stress collection portions in the metal support layer at the boundary portions between the end portions and the central portion inside the end portions, and to prevent damage to the metal support layer. [Explanation of symbols]

[0059] 1 Electric cell, 2 Electrolyte layer, 3 Electrode layer, 3-1 Cathode electrode layer, 3-2 Anode electrode layer, 4 Metal support layer, 4-1 Cathode metal support layer, 4-2 Anode metal support layer, 5 Center, 6 Edge, 7 Press mold

Claims

1. 1. A method for manufacturing an electric cell, which is a SOFC or SOEC, comprising: a step of preparing a laminate having an electrolyte layer, a cathode electrode layer, an anode electrode layer, and a pair of metal support layers, the pair of metal support layers having a porous structure; pressing the ends of the pair of metal support layers to densify them; Equipped with The pressing step is performed in a state in which the pair of metal support layers are heated. Method for manufacturing an electric cell.

2. The method of claim 1, the heating temperature of the pair of metal support layers in the pressing step is a temperature or higher at which the deformation resistance of the pair of metal support layers is 50% or less of that at room temperature. Manufacturing method.

3. The manufacturing method according to claim 1 or 2, the pressing step includes pressing the end portion in an atmospheric environment; The heating temperature of the pair of metal support layers in the step of pressing the ends in the air atmosphere is less than 750°C. Manufacturing method.

4. The manufacturing method according to claim 1 or 2, Furthermore, impregnating the cathode electrode layer and / or the anode electrode layer with a slurry containing a catalyst; the pressing step includes pressing the end portion after the impregnation step; the heating temperature of the pair of metal support layers in the step of pressing the ends after the step of impregnating the slurry is 600°C or less; Manufacturing method.

5. The manufacturing method according to claim 1 or 2, the pressing step includes pressing the end portion in a non-oxidizing atmosphere; The heating temperature of the pair of metal support layers in the step of pressing the ends in a non-oxidizing atmosphere is 750°C or higher. Manufacturing method.

6. The manufacturing method according to claim 1 or 2, the pressing step includes a step of pressing using a press mold so that the ends of the pair of metal support layers are compressed, The press mold is The corners formed between the ends of the pair of metal support layers and the central portions of the pair of metal support layers have a shape formed by curved surfaces, or The pair of metal support layers have a shape in which the side surfaces of the central portions thereof are inclined surfaces. Manufacturing method.

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