Solid electrolyte layer, electrode assembly, and method for producing the same

Abstract

To provide a solid electrolyte layer and an electrode assembly in which bonding strength with an electrode is improved, interface resistance is reduced, and ohmic resistance caused by an electrolyte is reduced.SOLUTION: The solid electrolytic layer 15 has a first surface 15b and a second surface 15a located on the opposite side of the first surface LA. The first surface 15b has an uneven shape having a plurality of first protrusion portion 18a and a plurality of first recess portion 18b. The solid electrolyte layer 15 is made of an oxide solid electrolyte. The ratio T / D of the thickness T of the solid electrolytic layer 15 to the thickness D from the top of the side 18a of the first protrusion to the bottom of the side 18b of the first recess is 0.45 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte layer, an electrode assembly, and a method for producing the same. [Background technology]

[0002] A solid oxide fuel cell is constructed by disposing an anode and a cathode on either side of a solid electrolyte layer. In order to increase the effective area involved in the power generation reaction and enable the generation of high current density and power density, various techniques have been proposed for roughening the surface of the solid electrolyte layer to create an uneven structure at the bonding interfaces between the solid electrolyte layer and the anode and cathode.

[0003] For example, Patent Document 1 proposes a solid oxide fuel cell having a solid electrolyte layer that has a plurality of first depressions and / or first protrusions on at least one side, and that further has at least one or more second depressions and / or second protrusions within the first depressions and on the first protrusions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-067416 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology described in Patent Document 1, increasing the length of the interface between the electrolyte and the electrode increases the mechanical bond strength between the electrolyte and the electrode, and also increases the number of sites for electrode reaction, which may reduce the interface resistance. However, it is not possible to reduce the ohmic resistance caused by the electrolyte. Therefore, an object of the present invention is to provide a solid electrolyte layer and an electrode assembly in which the length of the interface between the electrolyte and the electrode is increased to improve the mechanical bonding strength between the electrolyte and the electrode, thereby reducing the interface resistance and reducing the ohmic resistance caused by the electrolyte. [Means for solving the problem]

[0006] The present invention has a first surface and a second surface located opposite thereto, the first surface has an uneven shape including a plurality of first protrusions and a plurality of first recesses, A solid electrolyte layer made of an oxide solid electrolyte, The present invention provides a solid electrolyte layer in which the value of T / D is 0.45 or less, where D is the distance from the top of the first convex portion to the bottom of the first concave portion and T is the thickness of the solid electrolyte layer.

[0007] The present invention also provides an electrode assembly including a solid electrolyte layer made of an oxide solid electrolyte, and a first electrode and a second electrode disposed on either side of the solid electrolyte layer, the solid electrolyte layer has a first surface and a second surface located on the opposite side thereof, the first surface having an uneven shape including a plurality of first protrusions and a plurality of first recesses, The present invention provides an electrode assembly in which the value of T / D is 0.45 or less, where D is the distance from the top of the first convex portion to the bottom of the first concave portion and T is the thickness of the solid electrolyte layer.

[0008] The present invention further provides a method for producing the electrode assembly, comprising: a stamper is pressed against a laminate of the first electrode green sheet and the solid electrolyte layer green sheet from the side of the solid electrolyte layer green sheet to form projections and recesses on the solid electrolyte layer green sheet; The method for producing an electrode assembly includes firing the layered body having the irregularities formed thereon to obtain a fired body. [Effects of the Invention]

[0009] According to the present invention, a solid electrolyte layer and an electrode assembly are provided which have improved bonding strength with an electrode, reduced interface resistance, and reduced ohmic resistance caused by the electrolyte. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing the structure in the thickness direction of one embodiment of an electrode assembly according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the solid electrolyte in the electrode assembly shown in FIG. [Figure 3] FIG. 3 is a perspective view showing one embodiment of a solid electrolyte layer in an electrode assembly according to the present invention. [Figure 4] FIG. 3 is a perspective view showing another embodiment of the solid electrolyte layer in the electrode assembly according to the present invention. [Figure 5] FIG. 5 is a schematic diagram showing the manufacturing process of the electrode assembly. [Figure 6] FIG. 6 is a schematic diagram showing the manufacturing process of the electrode assembly. [Figure 7] FIG. 7 is a schematic diagram showing an example of a stamper used in manufacturing an electrode assembly. [Figure 8] FIG. 8 is a schematic diagram showing another example of a stamper used in manufacturing an electrode assembly. [Figure 9] FIG. 9 is a schematic diagram showing yet another example of a stamper used in manufacturing an electrode assembly. [Figure 10] FIG. 10 is a schematic diagram showing the manufacturing process of the electrode assembly. [Figure 11] FIG. 11 is a schematic diagram showing the manufacturing process of the electrode assembly. [Figure 12] FIG. 12 is a schematic diagram showing the manufacturing process of the electrode assembly. [Figure 13] FIG. 13 is a schematic diagram showing the manufacturing process of the electrode assembly. [Figure 14] FIG. 14 is a cross-sectional view schematically showing the structure in the thickness direction of another embodiment of an electrode assembly according to the present invention. [Figure 15] FIG. 15 is a graph of the ohmic resistance measured for the electrode assemblies of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on preferred embodiments with reference to the drawings. Fig. 1 shows a schematic cross section in the thickness direction of one embodiment of an electrode assembly according to the present invention. It should be noted that since this figure shows one embodiment of an electrode assembly, the dimensions, including the thickness of each member, may differ from those of an actual electrode assembly. The electrode assembly 10 shown in the figure includes a solid electrolyte layer 15, a first electrode 11 disposed below the solid electrolyte layer 15, and a second electrode 12 disposed above the solid electrolyte layer 15. The solid electrolyte layer 15 is made of a material that has oxide ion conductivity or proton conductivity at or above a predetermined temperature. In the following description, for convenience, oxide ion conductivity and proton conductivity are also collectively referred to as "ion conductivity."

[0012] A first intermediate layer 13 is disposed between the first electrode 11 and the solid electrolyte layer 15. Meanwhile, a second intermediate layer 14 is disposed between the second electrode 12 and the solid electrolyte layer 15. Furthermore, a support layer 16 is disposed on the surface of the first electrode 11 opposite to the surface facing the first intermediate layer 13. 1, the first electrode 11 and the first intermediate layer 13 are shown as having the same size, but the size relationship between them is not limited to this. For example, the first electrode 11 and the first intermediate layer 13 may be different sizes. When the first electrode 11 and the first intermediate layer 13 are different sizes in a plan view, it is preferable that the first intermediate layer 13 is larger than the first electrode 11. In this case, it is preferable that the first intermediate layer 13 extends from the entire peripheral edge of the first electrode 11 in a plan view. This prevents the first electrode 11 and the solid electrolyte layer 15 from coming into direct contact with each other, thereby preventing the electrode assembly 10 from becoming high in resistance. The same applies to the second electrode 12 and the second intermediate layer 14; the second electrode 12 and the second intermediate layer 14 may be the same size in a plan view, or may be different sizes. When the second electrode 12 and the second intermediate layer 14 are different sizes, it is preferable that the second intermediate layer 14 is larger than the second electrode 12. In this case, it is preferable that the second intermediate layer 14 extends from the entire peripheral edge of the second electrode 12 in a plan view. This prevents the second electrode 12 and the solid electrolyte layer 15 from coming into direct contact with each other, thereby preventing the electrode assembly 10 from becoming high in resistance.

[0013] 1, the first intermediate layer 13 and the solid electrolyte layer 15 are shown as having the same size, but the size relationship between the two is not limited to this, and for example, the solid electrolyte layer 15 and the first intermediate layer 13 may have different sizes. The same applies to the second electrode 12 side. For example, in a plan view, the first intermediate layer 13 and / or the second intermediate layer 14 are preferably larger than the solid electrolyte layer 15. In this case, it is preferable that the first intermediate layer 13 and / or the second intermediate layer 14 extend from the entire peripheral area of ​​the solid electrolyte layer 15 in a plan view. Furthermore, with regard to the support layer 16, in Figure 1, the support layer 16 and the first electrode 11 are shown as being the same size, but the size relationship between the two is not limited to this, and for example, the support layer 16 and the first electrode 11 may be different sizes.

[0014] 1 , the first intermediate layer 13 is in direct contact with the first electrode 11 and the solid electrolyte layer 15. Therefore, no layer is interposed between the first intermediate layer 13 and the first electrode 11. The first intermediate layer 13 is also in direct contact with the solid electrolyte layer 15, with no layer being interposed between them. The same is true for the second electrode 12 side, where the second intermediate layer 14 is in direct contact with the solid electrolyte layer 15 and the second electrode 12.

[0015] The first intermediate layer 13 and the second intermediate layer 14 (hereinafter, for convenience, both intermediate layers may be collectively referred to simply as “intermediate layer 17”) are used for the purpose of improving ionic conductivity between the solid electrolyte layer 15 and the first electrode 11 and / or the second electrode 12 in the electrode assembly 10. Increasing the ionic conductivity of the solid electrolyte layer 15 is important to reduce the electrical resistance of the electrode assembly 10. However, even if the solid electrolyte layer 15 is formed using a material with high ionic conductivity, there is a limit to how much the resistance of the electrode assembly 10 as a whole can be reduced if the interfacial resistance between the solid electrolyte layer 15 and the first electrode 11 and / or the second electrode 12 is high. Therefore, in the electrode assembly 10 of the present embodiment, the first intermediate layer 13 is disposed between the first electrode 11 and the solid electrolyte layer 15 to reduce the interfacial resistance between the first electrode 11 and the solid electrolyte layer 15, and the second intermediate layer 14 is disposed between the second electrode 12 and the solid electrolyte layer 15 to reduce the interfacial resistance between the second electrode 12 and the solid electrolyte layer 15. If the interfacial resistance between solid electrolyte layer 15 and first electrode 11 and / or second electrode 12 is sufficiently low, intermediate layer 13 and / or intermediate layer 14 does not need to be provided.

[0016] The support layer 16 is a layer that functions to increase the mechanical strength of the electrode assembly 10. Because the support layer 16 increases the mechanical strength of the electrode assembly 10, it is possible to reduce the thicknesses of the first electrode 11, the second electrode 12, the solid electrolyte layer 15, and the intermediate layer 17 compared to when the support layer 16 is not present. Reducing the thicknesses of these layers is advantageous from the viewpoint of reducing the electrical resistance of the electrode assembly 10 as a whole.

[0017] The solid electrolyte layer 15 is a conductor in which oxide ions or protons serve as carriers. A single crystal or polycrystalline material is used as the solid electrolyte contained in the solid electrolyte layer 15. There are no particular restrictions on the material that constitutes the solid electrolyte layer 15, as long as it has ion conductivity. Details of the material will be described later.

[0018] One of the features of the electrode assembly 10 of this embodiment is the shape of the solid electrolyte layer 15. Specifically, as shown in FIG. 2 , the solid electrolyte layer 15 has a first surface 15b and a second surface 15a. The first surface 15b faces the first electrode 11. The second surface 15a faces the second electrode 12. At least the first surface 15b of the solid electrolyte layer 15, which faces the first electrode 11, has a sinusoidal uneven shape having a plurality of first electrode side protrusions 18a protruding toward the first electrode 11 and a plurality of first electrode side recesses 18b recessed in a direction away from the first electrode 11. In a vertical cross-sectional view, first electrode side protrusion 18a has a convex shape that forms a smooth curve protruding toward first electrode 11. On the other hand, first electrode side recess 18b has a concave shape that forms a smooth curve recessing in a direction away from first electrode 11. First electrode side protrusion 18a and first electrode side recess 18b are connected by a smooth curve.

[0019] Solid electrolyte layer 15 also has an uneven shape on second surface 15a, which is the surface facing second electrode 12. In detail, second surface 15a has a sinusoidal uneven shape that has multiple second electrode side convex portions 19a that protrude toward second electrode 12 and multiple second electrode side concave portions 19b that are recessed in a direction away from second electrode 12. In a vertical cross-sectional view, second electrode side protrusion 19a has a convex shape that forms a smooth curve protruding toward second electrode 12. On the other hand, second electrode side recess 19b has a concave shape that forms a smooth curve recessing in a direction away from second electrode 12. Second electrode side protrusion 19a and second electrode side recess 19b are connected by a smooth curve.

[0020] When the first surface 15b and the second surface 15a of the solid electrolyte layer 15 have the above-described shapes, the solid electrolyte layer 15 preferably has undulations on each surface in a longitudinal cross-sectional view, forming a waveform as a whole. In particular, the uneven shape of the first surface 15b and the uneven shape of the second surface 15a are complementary to each other. Specifically, the second electrode side recesses 19b are present on the second surface 15a at the positions of the first electrode side protrusions 18a on the first surface 15b. Additionally, the second electrode side protrusions 19a are present on the second surface 15a at the positions of the first electrode side recesses 18b on the first surface 15b. Inverting the shape of the first electrode side protrusions 18a results in the shape of the second electrode side recesses 19b, and inverting the shape of the first electrode side recesses 18b results in the shape of the second electrode side protrusions 19a.

[0021] In the electrode assembly 10 of this embodiment, the first intermediate layer 13, which is a layer facing the first surface 15b of the solid electrolyte layer 15, has an uneven surface facing the first surface 15b. Specifically, the surface of the first intermediate layer 13 facing the first surface 15b has an uneven surface that includes a plurality of convex portions that protrude toward the solid electrolyte layer 15 and a plurality of concave portions that recess in a direction away from the solid electrolyte layer 15. The uneven surface of the first intermediate layer 13 is complementary to the uneven surface of the first surface 15b of the solid electrolyte layer 15. As a result, the surfaces of the first intermediate layer 13 and the solid electrolyte layer 15 that face each other have uneven surfaces, and the two layers 13 and 15 are in close contact with each other without any gaps.

[0022] The surface of first intermediate layer 13 facing first electrode 11 also has an uneven shape. In detail, the surface of first intermediate layer 13 facing first electrode 11 has an uneven shape that has a plurality of convex portions that protrude toward first electrode 11 and a plurality of concave portions that are recessed in a direction away from first electrode 11. The uneven shape of first intermediate layer 13 is complementary to the uneven shape of the surface of first electrode 11 facing first intermediate layer 13. As a result, the surfaces of first intermediate layer 13 and first electrode 11 facing each other have uneven shapes, and first intermediate layer 13 and first electrode 11 are in close contact with each other without any gaps. Since the surface of first intermediate layer 13 facing solid electrolyte layer 15 and the surface facing first electrode 11 have the above-described shapes, each surface of first intermediate layer 13 preferably has undulations in a longitudinal cross-sectional view, giving first intermediate layer 13 a waveform shape as a whole. In particular, in first intermediate layer 13, the uneven shape of the surface facing solid electrolyte layer 15 and the uneven shape of the surface facing first electrode 11 are complementary in shape.

[0023] In contrast to the uneven surface of first electrode 11 facing first intermediate layer 13, the surface of first electrode 11 facing support layer 16 is substantially flat. However, this does not prevent the surface of first electrode 11 facing support layer 16 from having an uneven surface (see FIG. 14 described later).

[0024] In the electrode assembly 10 of this embodiment, the second intermediate layer 14, which is a layer facing the second surface 15a of the solid electrolyte layer 15, has an uneven surface facing the second surface 15a. Specifically, the surface of the second intermediate layer 14 facing the second surface 15a has an uneven surface that includes a plurality of convex portions that protrude toward the solid electrolyte layer 15 and a plurality of concave portions that recess in a direction away from the solid electrolyte layer 15. The uneven surface of the second intermediate layer 14 is complementary to the uneven surface of the second surface 15a of the solid electrolyte layer 15. As a result, the opposing surfaces of the second intermediate layer 14 and the solid electrolyte layer 15 have uneven surfaces, and the two layers 14, 15 are in close contact with each other without any gaps.

[0025] The surface of the second intermediate layer 14 facing the second electrode 12 also has an uneven shape. In detail, the surface of the second intermediate layer 14 facing the second electrode 12 has an uneven shape that has a plurality of convex portions that protrude toward the second electrode 12 and a plurality of concave portions that are recessed in a direction away from the second electrode 12. The uneven shape of the second intermediate layer 14 is complementary to the uneven shape of the surface of the second electrode 12 facing the second intermediate layer 14. As a result, the surfaces of the second intermediate layer 14 and the second electrode 12 facing each other have uneven shapes, and the second intermediate layer 14 and the second electrode 12 are in close contact with each other without any gaps. Since the surface of second intermediate layer 14 facing solid electrolyte layer 15 and the surface facing second electrode 12 have the above-described shapes, each surface of second intermediate layer 14 preferably has undulations in a longitudinal cross-sectional view, giving second intermediate layer 14 a waveform shape as a whole. In particular, in second intermediate layer 14, the uneven shape of the surface facing solid electrolyte layer 15 and the uneven shape of the surface facing second electrode 12 are complementary in shape.

[0026] The exposed surface of the second electrode 12, i.e., the outer surface of the electrode assembly 10, also has an uneven shape. In detail, the exposed surface of the second electrode 12 has an uneven shape that has a plurality of convex portions that protrude toward the second intermediate layer 14 and a plurality of concave portions that are recessed in a direction away from the second intermediate layer 14. The uneven shape of the exposed surface of the second electrode 12 is complementary to the uneven shape of the surface of the second electrode 12 that faces the second intermediate layer 14. Since the exposed surface of the second electrode 12 and the surface facing the second intermediate layer 14 have the above-mentioned shape, it is preferable that the second electrode 12 has undulations on each surface when viewed in vertical cross section, and has a wavy shape overall.

[0027] Because each layer in the electrode assembly 10 of this embodiment has the above-described shape, the electrode assembly 10 has a larger contact area between the solid electrolyte layer 15 and each intermediate layer 17, and a larger contact area between each intermediate layer 17 and each electrode layer 11, 12, and also has an increased effective area of ​​the solid electrolyte layer, compared to a flat state without texture. This is expected to result in improved bonding strength, reduced interfacial resistance, and reduced ohmic resistance due to the electrolyte. Furthermore, the reduced interfacial resistance and reduced ohmic resistance due to the electrolyte enable the generation of high current density and high power density. From the viewpoint of making these advantages more pronounced, on at least one of first surface 15b and second surface 15a of solid electrolyte layer 15, when the distance from the highest point of a convex portion to the lowest point of a concave portion is D (hereinafter also referred to as "inter-concave / convex distance D") and the thickness of solid electrolyte layer 15 is T (hereinafter also simply referred to as "thickness T"), the value of T / D is preferably set to 0.45 or less, more preferably set to 0.40 or less, and even more preferably set to 0.30 or less. There is no particular limit to the lower limit of the value of T / D, and the closer this value is to zero, the more desirable it is from the viewpoints of improving the bonding strength of the electrode assembly 10, reducing the interfacial resistance, and reducing the ohmic resistance caused by the electrolyte. However, if the value of T / D is small, around 0.1, the effects of the present invention are sufficiently achieved. Note that, when the T / D values ​​differ between the first surface 15b and the second surface 15a of the solid electrolyte layer 15, it is sufficient that the T / D value on at least one surface satisfies the above-mentioned value. In particular, it is preferable that the T / D value on the surface of the two surfaces of the solid electrolyte layer 15 that is located on the first electrode 11 side satisfies the above-mentioned value from the viewpoint of improving the performance of the electrode assembly 10. From the same viewpoint, it is preferable that the T / D value on the surface of the two surfaces of the solid electrolyte layer 15 that faces the electrode that will become the anode when the electrode assembly 10 is used as an electrochemical cell satisfies the above-mentioned value. From the viewpoints of improving the bonding strength of the electrode assembly 10, reducing the interface resistance, and reducing the ohmic resistance caused by the electrolyte, it is advantageous that the T / D values ​​on both the first surface 15b and the second surface a satisfy the above-mentioned value.

[0028] The thickness T is measured at the top position of the convex portion or the bottom position of the concave portion. The measurement is performed using an SEM secondary electron image of the vertical cross section of the solid electrolyte layer 15 or the measurement function of a laser microscope. In particular, when measuring with a laser microscope, the thickness is measured by selecting multiple top positions of the convex portions and multiple bottom positions of the concave portions. Regardless of which device is used, the thickness is measured at five or more locations, and the arithmetic mean value of the measurements is taken as the thickness T. For measuring the SEM secondary electron image, a device manufactured by JEOL, for example, can be used. For measuring with a laser microscope, a device manufactured by Zygo, for example, can be used.

[0029] The inter-protrusion distance D is measured using an SEM secondary electron image of a vertical cross section of the solid electrolyte layer 15 or the measurement function of a laser microscope. In particular, when measuring with a laser microscope, the positions of the highest peaks of the convex portions and the lowest peaks of the concave portions are selected and measured. Whichever device is used, measurements are taken at five or more locations, and the arithmetic mean value of the measurements is taken as the inter-protrusion distance D. For measuring the SEM secondary electron image, a device manufactured by JEOL, for example, can be used. For measuring with a laser microscope, a device manufactured by Zygo, for example, can be used.

[0030] The value of T / D is as described above, and from the viewpoint of suppressing a decrease in ion conductivity, the thickness T of the solid electrolyte layer 15 is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. Furthermore, from the viewpoint of maintaining the strength of the solid electrolyte layer 15, the thickness T of the solid electrolyte layer 15 is preferably 0.5 μm or more, more preferably 3 μm or more, and even more preferably 4 μm or more.

[0031] The thickness T of the solid electrolyte layer 15 preferably has a small variation in value, since current concentration can be suppressed. From this viewpoint, the coefficient of variation, defined as [standard deviation of thickness T / average value of thickness T], is preferably 0.50 or less, more preferably 0.20 or less, and even more preferably 0.10 or less. To calculate the coefficient of variation, 100 or more measured values ​​are used.

[0032] On the other hand, the inter-concave distance D is preferably 1 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more, from the viewpoints of improving the bonding strength of the electrode assembly 10, reducing the interfacial resistance, and reducing the ohmic resistance caused by the electrolyte. Moreover, from the viewpoint of easily imparting an irregular shape to the solid electrolyte layer 15, the inter-concave distance D is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less.

[0033] In the solid electrolyte layer 15, on at least one of the first surface 15b and the second surface 15a, the inter-protrusion distance d from the top of one arbitrarily selected protrusion to the top of another protrusion adjacent to the selected protrusion is preferably 2000 μm or less, from the viewpoints of improving the bonding strength of the electrode assembly 10, reducing interfacial resistance, and reducing ohmic resistance caused by the electrolyte. To further enhance this advantage, the inter-protrusion distance d is more preferably 1500 μm or less, and even more preferably 1000 μm or less. The inter-protrusion distance d is preferably 1 μm or more, more preferably 50 μm or more, and even more preferably 500 μm or more, which is advantageous in terms of ease of forming a concave-convex shape. The distance d between the convex portions is the arithmetic mean value of the measurement results at five or more locations.

[0034] From the viewpoints of improving the bonding strength of the electrode assembly 10, reducing the interfacial resistance, and reducing the ohmic resistance caused by the electrolyte, it is preferable that the value of D / d, which is the ratio of the distance D between the projections and recesses to the distance d between the projections, be 1 / 100 or more. To make this advantage even more pronounced, the value of D / d is more preferably 1 / 20 or more, and even more preferably 1 / 10 or more. From the viewpoint of ease of forming the projection-recess shape, it is advantageous that the value of D / d is preferably 10 or less, more preferably 1 or less, and even more preferably 1 / 4 μm or less.

[0035] In the electrode assembly 10, the ohmic resistance of the solid electrolyte layer 15 is R, and the ohmic resistance of a flat control solid electrolyte layer that is made of the same material and composition as the solid electrolyte layer 15, has the same thickness, and does not have an uneven shape is R. ref Then, R / R ref From the viewpoint of reducing the ohmic resistance caused by the electrolyte, it is preferable that R / R is 3 / 4 or less. ref is more preferably 3 / 5 or less, and even more preferably 1 / 2 or less. The ohmic resistance of each of the solid electrolyte layer 15 and the control solid electrolyte layer is measured by the following method. At 700°C, a temperature range in which a fuel cell made of the electrode assembly having a solid electrolyte layer 15 or a control solid electrolyte layer can operate satisfactorily, 100 ccm of hydrogen is flowed as fuel gas to the fuel electrode (first electrode 11), and 80 ccm of nitrogen and 20 ccm of oxygen are flowed to the air electrode (second electrode 12). Under these conditions, a break-in operation is performed by measuring the voltage for about half a day until the OCV between the electrodes stabilizes. Then, AC impedance measurements are performed at 100 mHz to 100 kHz. The vertical axis [-ImZ (Ω cm 2 )) is closest to 0, and the horizontal axis [ReZ (Ω cm 2 ) is taken as the ohmic resistance. This Nyquist plot is drawn not in terms of the actual electrode area that follows the unevenness, but in terms of the apparent electrode area.

[0036] The uneven shape of the solid electrolyte layer 15 in the electrode assembly 10 of this embodiment is not particularly limited. For example, as shown in FIG. 3, an uneven shape can be adopted in which the first electrode side protrusions 18a have ridge shapes extending along a first direction (the direction indicated by symbol X in the figure) in the first surface 15b, the first electrode side recesses 18b have groove shapes extending along the first direction in the first surface 15b, and the first electrode side protrusions 18a and the first electrode side recesses 18b are alternately arranged in a second direction (the direction indicated by symbol Y in the figure) perpendicular to the first direction. Although not shown in FIG. 3, the uneven shape of the second surface 15a of the electrode assembly 10 can be a shape complementary to the uneven shape of the first surface 15b.

[0037] As another example of the uneven shape, the uneven shape shown in Fig. 4 can be adopted. The electrode assembly 10 shown in Fig. 4 has an uneven shape in which first electrode side convex portions 18a and first electrode side concave portions 18b are alternately arranged along a first direction (direction indicated by symbol X in Fig. 4) in the first surface 15b, and are alternately arranged along a second direction (direction indicated by symbol Y in Fig. 4) perpendicular to the first direction. Although not shown in Fig. 4, the uneven shape of the second surface 15a of the electrode assembly 10 can be a shape complementary to the uneven shape of the first surface 15b.

[0038] As another example of the uneven shape, although not shown, it is also possible to adopt an uneven shape in which the first electrode side convex portion has a ridge-like shape extending along a first direction in the first surface and the first electrode side convex portion has a ridge-like shape extending along a second direction perpendicular to the first direction, so that the first electrode side convex portion as a whole forms a lattice-like convex portion and the area surrounded by the four sides of the lattice becomes the first electrode side concave portion. In this case, the uneven shape of the second surface of the electrode assembly can be a shape complementary to the uneven shape of the first surface.

[0039] Next, a process for producing the electrode assembly 10 of the present invention will be described with reference to FIGS. First, a laminate 20 is prepared as shown in FIG. 5. The laminate 20 is formed by laminating a support layer green sheet 21, a first electrode green sheet 22, a first intermediate layer green sheet 23, a solid electrolyte layer green sheet 24, and a second intermediate layer green sheet 25 in this order. Each green sheet contains powder of the respective material and a dispersion medium. Water or an organic solvent such as alcohol can be used as the dispersion medium. If necessary, a dispersant, an antifoaming agent, a binder, etc. may also be added. The green sheets can be prepared using, for example, an automatic film applicator.

[0040] The thickness of each green sheet is determined in consideration of the thickness of each layer in the intended electrode assembly 10 . The thickness of the support layer green sheet 21 is preferably 1000 μm or more and 4000 μm or less. The thickness of the first electrode green sheet 22 is preferably 10 μm or more and 100 μm or less. The thickness of the first intermediate layer green sheet 23 is preferably 5 μm or more and 50 μm or less. The thickness of the solid electrolyte layer green sheet 24 is preferably 5 μm or more and 50 μm or less. The second intermediate layer green sheet 25 preferably has a thickness of 5 μm or more and 50 μm or less.

[0041] Next, a stamper 30 is prepared as shown in Fig. 6. The stamper 30 is substantially plate-shaped, and one surface 30a thereof has an uneven shape. The stamper 30 is arranged so that the uneven surface 30a faces the second intermediate layer green sheet 25 of the laminate 20.

[0042] 7, the stamper 30 may have an uneven shape in which ridges 40 extending in one direction and grooves 41 extending in the same direction as the ridges 40 are alternately arranged. When the stamper 30 shown in the figure is used, the solid electrolyte layer 15 can be shaped into the uneven shape shown in FIG.

[0043] 8, another stamper 30 has an uneven shape in which convex portions and concave portions are alternately arranged along a first direction in the plane of the stamper 30 and also alternately arranged along a second direction perpendicular to the first direction. When the stamper 30 shown in the figure is used, the solid electrolyte layer 15 can be shaped into the uneven shape shown in FIG.

[0044] As another stamper 30, as shown in FIG. 9 , the protruding ridges 40 have a ridge-like shape extending along a first direction X within the plane of the stamper 30, and the protruding ridges 40 also have a ridge-like shape extending along a second direction Y perpendicular to the first direction X, thereby forming a lattice-like convex shape as a whole, and the area surrounded by the four sides of the lattice has an uneven shape that becomes a recess 41.

[0045] 7 to 9, the height of the convex portions, i.e., the distance from the bottom of the concave portion to the top of the convex portion, is preferably 1 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more, from the viewpoint of satisfying the above-mentioned T / D value. From the same viewpoint, the height of the convex portions is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. Furthermore, the distance between adjacent convex portions is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 100 μm or more, from the viewpoints of stably forming the uneven shape, increasing the surface area of ​​solid electrolyte layer 15, and ensuring the strength of solid electrolyte layer 15. From the same viewpoints, the distance between adjacent convex portions is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less.

[0046] There are no particular limitations on the material of the stamper, as long as it can provide the desired concave-convex shape. For example, the stamper can be made of metal or plastic. Examples of manufacturing methods include injection molding, press molding, modeling using a three-dimensional printer, and casting.

[0047] 10 , stamper 30 is pressed against second intermediate layer green sheet 25. In this case, as described above, surface 30a of stamper 30 having the concave-convex shape is brought into contact with second intermediate layer green sheet 25. As a result, the concave-convex shape of surface 30a is transferred to second intermediate layer green sheet 25, solid electrolyte layer green sheet 24, first intermediate layer green sheet 23, and first electrode green sheet 22, forming the concave-convex shape. The concave-convex shapes formed on these green sheets 22, 23, 24, and 25 are complementary to the concave-convex shape of stamper 30.

[0048] The formation of the irregularities using the stamper 30 can be performed, for example, by cold isostatic pressing (CIP) processing, but is not limited to this method. When performing CIP processing, the pressure is preferably 1 MPa to 20 MPa from the viewpoint of reliably forming the irregularities and sufficiently increasing the adhesion between adjacent green sheets, more preferably 3 MPa to 15 MPa, and even more preferably 5 MPa to 10 MPa. Furthermore, when performing CIP processing, it is preferable to hold the pressure for 10 seconds or more and 180 seconds or less in order to ensure that the unevenness is formed and to sufficiently increase the adhesion between adjacent green sheets, and more preferably 30 seconds or more and 120 seconds or less, and even more preferably 60 seconds or more and 100 seconds or less.

[0049] When performing CIP processing, support plates (not shown) may be placed below the laminate 20 and above the stamper 30 in the state shown in Fig. 10, and the CIP processing may be performed in a state in which the laminate 20 and the stamper 30 are sandwiched between the pair of support plates. Examples of support plates include cardboard, plastic plates, and metal plates.

[0050] After the pressing is performed under a predetermined pressure for a predetermined time, the pressure is released and the stamper 30 is removed from the laminate 20, as shown in Fig. 11. Each surface of the solid electrolyte layer green sheet 24 in the laminate 20 is deformed into an uneven shape. The uneven shape on one surface of the solid electrolyte layer green sheet 24 is complementary to the uneven shape on the other surface.

[0051] Furthermore, by applying pressure using the stamper 30, each surface of the first intermediate layer green sheet 23 in the laminate 20 is formed into an uneven shape, although this depends on the thickness of the sheet.

[0052] Once the laminate 20 has been shaped to have projections and recesses, the laminate 20 is then subjected to a firing process. Prior to firing the laminate 20, the fired body 20 can be processed into a shape having a desired outline, for example, a circle, as needed. This processing is performed, for example, by punching the fired body 20 using a mold.

[0053] The laminate 20 can be fired in an oxygen-containing atmosphere such as air, an inert atmosphere such as nitrogen, or a reducing atmosphere such as hydrogen. The maximum firing temperature is preferably 1000°C or higher and 1700°C or lower, more preferably 1200°C or higher and 1670°C or lower, and even more preferably 1400°C or higher and 1650°C or lower. The time for which the maximum temperature is maintained is preferably from 1 hour to 50 hours, more preferably from 1 hour to 5 hours, and even more preferably from 1 hour to 3 hours. The temperature rise conditions are preferably 100° C. / h or more and 300° C. / h or less, more preferably 150° C. / h or more and 250° C. / h or less, and even more preferably 180° C. / h or more and 220° C. / h or less. The temperature drop condition is preferably 100° C. / h or more and 400° C. / h or less, more preferably 150° C. / h or more and 350° C. / h or less, and even more preferably 200° C. / h or more and 300° C. / h or less.

[0054] Firing the laminate 20 produces a precursor 32 (see FIG. 12) of an electrode assembly in which the support layer 16, the first electrode 11, the first intermediate layer 13, the solid electrolyte layer 15, and the second intermediate layer 14 are laminated in this order. Forming the second electrode 12 on the precursor 32 produces the desired electrode assembly 10. The formation of the second electrode 12 will be described below.

[0055] 13 , a coating material for forming the second electrode, i.e., a slurry containing a powder of the material constituting the second electrode 12 and a dispersion medium, is applied to the exposed surface of the second intermediate layer 14 of the precursor 32 to form a coating film 35. The thickness of the coating film 35 is determined in consideration of the desired thickness of the second electrode 12. The area to be coated can be determined appropriately depending on the specific application of the electrode assembly 10.

[0056] Once the coating film 35 is formed, the coating film 35 is fired together with the precursor 32, and the second electrode 12 is formed from the coating film 35. The coating 35 can be baked in an oxygen-containing atmosphere such as air or an inert atmosphere such as nitrogen. The maximum firing temperature is preferably 850°C or higher and 950°C or lower, more preferably 870°C or higher and 930°C or lower, and even more preferably 890°C or higher and 910°C or lower. The time for which the maximum temperature is maintained is preferably from 1 hour to 10 hours, more preferably from 1 hour to 5 hours, and even more preferably from 1 hour to 3 hours.

[0057] In this way, the desired electrode assembly 10 (see FIG. 1) is obtained. The electrode assembly 10 thus obtained can be suitably used as a cell of a solid oxide fuel cell, or can be suitably used as a steam electrolysis cell.

[0058] Next, suitable materials for use in each layer constituting the electrode assembly 10 of this embodiment will be described.

[0059] Examples of materials that can be used to form the solid electrolyte layer 15 include materials that have oxide ion conductivity and materials that have proton conductivity. As a material having oxide ion conductivity, for example, yttria-stabilized zirconia (Zr 1-x Y x O2), scandium-stabilized zirconia (Zr 1-x Sc x O2), lanthanum silicate (La 9.33+x SiO 26+1.5x ) Gadolinium-doped cerium oxide (Ce 1-x Gd x O2), samarium-doped cerium oxide (Ce 1-x Sm x O2), lanthanum gallate (La 1-x Sr x )(Ga 1-y Mg y )O3 and yttrium-doped bismuth oxide (Bi 1-x Y x O 1.5 ) etc. Examples of proton-conducting materials include Ba a Zr 1-x M x O3, Ba a Ce 1-x M x O3 and Ba a Zr 1-x-y Ce x M yO3 (where M represents at least one element selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Y, Sc, Mn, Fe, Co, Ni, Al, Ga, In, and Lu, 0 < x < 1, 0 < y < 1, and 0.95 ≤ a ≤ 1.05). etc. may be mentioned.

[0060] The first electrode 11 and the second electrode 12 can be composed of, for example, a metal material or a mixed conducting oxide having both ionic conductivity and electronic conductivity. When the first electrode 11 and the second electrode 12 are composed of a metal material, since such a metal material has advantages such as high catalytic activity, it is preferably composed of a platinum group element, gold, or silver. Examples of platinum group elements include platinum, palladium, iridium, ruthenium, rhodium, and osmium. These elements can be used alone or in combination of two or more. Also, as the first electrode 11 and the second electrode 12, a cermet containing a platinum group element and an oxide having oxygen ion conductivity can be used independently for each.

[0061] On the other hand, when either the first electrode 11 or the second electrode 12 is composed of a mixed conducting oxide having both oxygen ion conductivity and electronic conductivity, as the mixed conducting oxide, those having a perovskite structure represented by ABO 3-δ are preferably used. In the formula, A represents an alkaline earth metal element. B represents a transition metal element, for example, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Ta, and W. δ is a fractional number caused by the valences and amounts of A, B, and O. Oxides having a perovskite structure represented by ABO 3-δ are variously known, and it is known that such oxides have various crystal systems, for example, cubic, tetragonal, rhombohedral, and orthorhombic. Among these crystal systems, it is preferable to use an ABO 3-δ type oxide having a cubic perovskite structure as the first electrode 11 and / or the second electrode 12.

[0062] If the first electrode 11 and the second electrode 12 have a predetermined thickness, the ionic conductivity of the entire electrode assembly 10 can be more effectively increased. Specifically, the thickness of each of the first electrode 11 and the second electrode 12 is preferably 100 nm or more, more preferably 500 nm or more, and even more preferably 1000 nm or more and 30000 nm or less. The thickness of the first electrode 11 and the second electrode 12 can be measured using a stylus profilometer or an electron microscope.

[0063] When first electrode 11 and / or second electrode 12 has a wavy shape as a whole, the thickness of the layer is synonymous with the thickness T of solid electrolyte layer 15 shown in FIG.

[0064] It is preferable to use a material having a fluorite crystal structure as the material forming the first intermediate layer 13 and the second intermediate layer 14. Furthermore, it is also preferable that the material forming the first intermediate layer 13 and the second intermediate layer 14 contains a rare earth element in addition to having the above-mentioned crystal structure. In particular, it is preferable that the material forming the first intermediate layer 13 and the second intermediate layer 14 is composed of cerium oxide (hereinafter also referred to as "LnDC") containing a rare earth element (excluding cerium, hereinafter also referred to as "Ln").

[0065] The first intermediate layer 13 and the second intermediate layer 14 are preferably made of the same material and have the same composition, which alleviates stress caused by heat shrinkage when the precursor 32 shown in Fig. 13 is fired, effectively preventing peeling between the layers.

[0066] In LnDC, examples of rare earth elements doped into cerium oxide include lanthanum, samarium, gadolinium, yttrium, erbium, ytterbium, and dysprosium. These rare earth elements may be used singly or in combination of two or more. In particular, the first intermediate layer 13 and the second intermediate layer 14 are preferably composed of cerium oxide containing lanthanum, since this can further enhance the ionic conductivity of the entire electrode assembly 10.

[0067] In LnDC, the atomic ratio of Ln to Ce, Ln / Ce, is preferably 0.001 or more and 1.2 or less, because this increases the ionic conductivity of the entire electrode assembly 10. To further enhance this effect, the Ln / Ce value in LnDC is more preferably 0.01 or more and 1.18 or less, even more preferably 0.10 or more and 1.15 or less, even more preferably 0.25 or more and 1.13 or less, and particularly preferably 0.40 or more and 1.10 or less. The Ln / Ce value is measured by energy dispersive X-ray spectroscopy (EDS), electron probe microanalyzer (EPMA), or the like.

[0068] As long as the first intermediate layer 13 and the second intermediate layer 14 have a certain thickness or greater, they can effectively improve the ionic conductivity between the solid electrolyte layer 15 and the second electrode 12. Specifically, the thickness of the first intermediate layer 13 and the second intermediate layer 14 is preferably 1 nm or more and 50 μm or less, more preferably 10 nm or more and 20 μm or less, and even more preferably 100 nm or more and 10 μm or less. The thickness of the first intermediate layer 13 and the second intermediate layer 14 can be measured using a stylus profilometer or an electron microscope.

[0069] When first intermediate layer 13 and / or second intermediate layer 14 has a wavy shape as a whole, the thickness of the layer is synonymous with thickness T of solid electrolyte layer 15 shown in FIG.

[0070] The material constituting the support layer 16 may contain an oxide of a rare earth element. Examples of the oxide of a rare earth element that can be used include the various oxides listed above as examples of the solid electrolyte. Additionally, a metal material may be used as the material constituting the support layer 16. From the viewpoint of high catalytic activity and electronic conductivity, the metal material is preferably nickel or a platinum group element, and nickel is more preferred. Alternatively, the material constituting the support layer 16 may contain heat-resistant stainless steel such as ferritic stainless steel or austenitic stainless steel, or a nickel-chromium alloy or an iron-chromium alloy. Alternatively, a cermet containing the oxide listed above as an example of the solid electrolyte and the metal material can be used as the support layer 16.

[0071] Although the present invention has been described above based on the preferred embodiments, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the uneven shape is formed by a pressure method using a stamper, but the uneven shape may be formed by other methods. In addition, in the above embodiment, the first intermediate layer 13 is arranged between the solid electrolyte layer 15 and the first electrode 11, and the second intermediate layer 14 is arranged between the solid electrolyte layer 15 and the second electrode 12, but alternatively, at least one of the first intermediate layer 13 and the second intermediate layer 14 may not be arranged. Furthermore, in the above embodiment, a support layer 16 is arranged on the outer surface of the first electrode 11, but if the thickness of the first electrode 11 is large and the strength of the electrode assembly 10 can be maintained by the first electrode 11, the support layer 16 does not need to be arranged.

[0072] Furthermore, the uneven shape formed on the solid electrolyte layer 15 may be a combination of a first uneven shape and a second uneven shape formed on the first uneven shape.

[0073] Furthermore, in the above embodiment, the front and back surfaces of the solid electrolyte layer 15, the first intermediate layer 13, the second intermediate layer 14, and the second electrode 12 all have uneven shapes, and the uneven shapes are complementary shapes, but although the front and back surfaces of these layers have uneven shapes, they do not need to have complementary shapes. Furthermore, in the above embodiment, the concave-convex shapes formed on the solid electrolyte layer 15, the first intermediate layer 13, the second intermediate layer 14, and the second electrode 12 are sinusoidal, but the concave-convex shapes are not limited to this and may be, for example, triangular, sawtooth, or rectangular. Alternatively, the concave-convex shapes may be a combination of two or more types of concave-convex shapes selected from the sinusoidal, triangular, sawtooth, and rectangular shapes. Alternatively, the tops of the convex portions and / or the bottoms of the concave portions in the sinusoidal concave-convex shapes may be flat.

[0074] Furthermore, in the above embodiment, the stamper 30 was used to form the irregularities on the laminate 20, which is formed by stacking the support layer green sheet 21, the first electrode green sheet 22, the first intermediate layer green sheet 23, the solid electrolyte layer green sheet 24, and the second intermediate layer green sheet 25 in this order. However, instead, the stamper may be pressed against the second electrode green sheet side of a laminate, which is formed by stacking at least the first electrode green sheet, the solid electrolyte layer green sheet, and the second electrode green sheet in this order, to form the irregularities on the solid electrolyte layer green sheet. However, using the first intermediate layer green sheet 23 and the second intermediate layer green sheet 25 has the advantage of mitigating the impact of the stamper 30 on the solid electrolyte layer green sheet 24. In particular, when the first intermediate layer green sheet 23 and the second intermediate layer green sheet 25 have the same composition, there is also the advantage that stress caused by shrinkage during firing is mitigated, effectively preventing delamination between the layers.

[0075] Furthermore, when forming the unevenness using the stamper 30 shown in Fig. 6, by increasing the pressure applied by the stamper 30, it is possible to impart an uneven shape to the interface between the first electrode 11 and the support layer 16, as shown in Fig. 14. In the embodiment shown in Fig. 14, both the front and back surfaces of the first electrode 11 have uneven shapes, and the uneven shapes are complementary shapes. The electrode assembly 10 shown in Fig. 14 has the advantage of further improving the bonding strength between the first electrode 11 and the support layer 16 compared to the electrode assembly 10 shown in Fig. 1.

[0076] In relation to the above-described embodiments, the present invention further discloses the following solid electrolyte layer, electrode assembly, and method for manufacturing the electrode assembly. <1> It has a first surface and a second surface located opposite thereto, the first surface has an uneven shape including a plurality of first protrusions and a plurality of first recesses, A solid electrolyte layer made of an oxide solid electrolyte, A solid electrolyte layer in which, when the distance from the top of the first convex portion to the bottom of the first concave portion is D and the thickness of the solid electrolyte layer is T, the value of T / D is 0.45 or less. <2> the first protrusion has a ridge shape extending along a first direction in the first surface, the first recess has a groove shape extending along a first direction in the first surface, The first convex portions and the first concave portions are alternately arranged. <1> The solid electrolyte layer according to claim 1. <3> The first convex portions and the first concave portions are alternately arranged along a first direction in the first surface and a second direction perpendicular to the first direction. <1> The solid electrolyte layer according to claim 1. <4> The distance D is 1 μm or more and 2000 μm or less. <1> Or <3> 10. The solid electrolyte layer according to claim 9, wherein <5> The thickness T is 0.5 μm or more and 50 μm or less. <1> Or <4> 10. The solid electrolyte layer according to claim 9, wherein

[0077] <6> the distance d from the top of a first protrusion to the top of another first protrusion adjacent to the first protrusion is 2000 μm or less; <1> Or <5> 10. The solid electrolyte layer according to claim 9, wherein <7> The ohmic resistance of the solid electrolyte layer is R, The ohmic resistance of a flat control solid electrolyte layer made of the same material and composition as the solid electrolyte layer, having the same thickness, and having no irregularities is defined as R ref When R / R ref is less than 3 / 4, <1> Or <6> 10. The solid electrolyte layer according to claim 9, wherein <8> The coefficient of variation defined as [standard deviation of the thickness T / average value of the thickness T] is 0.50 or less, <1> Or <7> 10. The solid electrolyte layer according to claim 9, wherein <9> a value of D / d, which is a ratio of the distance D to the distance d from the apex of a first convex portion to the apex of another first convex portion adjacent to the first convex portion, is 1 / 100 or more; <1> Or <8> 10. The solid electrolyte layer according to claim 9, wherein <10> The second surface has an uneven shape having a plurality of second convex portions and a plurality of second concave portions. <1> Or <9> 10. The solid electrolyte layer according to claim 9, wherein <11> 10. The solid electrolyte layer according to claim 1, wherein the uneven shape of the first surface and the uneven shape of the second surface are complementary shapes.

[0078] <12> An electrode assembly including a solid electrolyte layer made of an oxide solid electrolyte, and a first electrode and a second electrode respectively disposed on either side of the solid electrolyte layer, the solid electrolyte layer has a first surface and a second surface located on the opposite side thereof, the first surface having an uneven shape including a plurality of first protrusions and a plurality of first recesses, An electrode assembly, wherein when the distance from the top of the first convex portion to the bottom of the first concave portion is D and the thickness of the solid electrolyte layer is T, the value of T / D is 0.45 or less. <13> <12> A fuel cell comprising the electrode assembly according to claim 1. <14> <12> A steam electrolysis cell comprising the electrode assembly according to claim 1. <15> <12> A method for producing the electrode assembly according to claim 1, a stamper is pressed against a laminate of the first electrode green sheet and the solid electrolyte layer green sheet from the side of the solid electrolyte layer green sheet to form projections and recesses on the solid electrolyte layer green sheet; The method for producing an electrode assembly includes firing the unevenly shaped laminate to obtain a fired body. <16> Applying a coating material for forming a second electrode to the uneven surface of the fired body; baking the paint for forming the second electrode; <15> The manufacturing method described in <17> a stamper is pressed against the laminate of the first electrode green sheet, the solid electrolyte layer green sheet, and the second electrode green sheet from the side of the second electrode green sheet to form projections and recesses on the solid electrolyte layer green sheet; <15> The manufacturing method described in [Example]

[0079] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "% by mass."

[0080] Example 1 In this example, an electrode assembly 10 having the structure shown in FIG. 1 was manufactured. (1) Manufacturing of laminates As the raw material composition used to manufacture the solid electrolyte layer green sheet, 9.005 g of La2Si2O7 powder and 4.933 g of ethanol were used and mixed to obtain a slurry. The raw material composition used to manufacture the first intermediate layer green sheet and the second intermediate layer green sheet contains La 0.5 Ce 0.510.104 g of O2 powder and 9.242 g of ethanol were mixed to obtain a slurry. The raw material composition used to manufacture the first electrode green sheet was 7.291 g of nickel oxide powder, La 0.5 Ce 0.5 9.008 g of O2 powder and 15.75 g of ethanol were mixed to obtain a slurry. The raw material composition used to manufacture the support layer green sheet was 20.724 g of NiO powder, 20.724 g of La 9.33 SiO 26 19.657 g of the powder and 30.340 g of ethanol were mixed to obtain a slurry.

[0081] Using an automatic film applicator, green sheets were prepared from each slurry. The thickness of the solid electrolyte layer green sheet was 20 μm. The thickness of the first intermediate layer green sheet and the second intermediate layer green sheet was 19 μm. The thickness of the first electrode green sheet was 33 μm. The thickness of the support layer green sheet was 220 μm.

[0082] A support layer green sheet, a first electrode green sheet, a first intermediate layer green sheet, a solid electrolyte layer green sheet, and a second intermediate layer green sheet are laminated in this order. Six support layer green sheets were stacked to increase the thickness. The laminate was thermocompression bonded in the thickness direction at 70°C and 0.3 MPa.

[0083] (2) Uneven shaping Using a stamper having a sinusoidal concave-convex shape as shown in Figure 9, the concave-convex surface of the stamper was brought into contact with the exposed surface of the second intermediate layer green sheet in the laminate. At this time, a sheet having a basis weight of 1500 g / m was applied to the outer surface of the laminate and the outer surface of the stamper. 2 In the stamper shown in the figure, the distance between adjacent convex portions (the distance between the tops of the convex portions) was 1 mm, and the height of the convex portions (the distance between the tops of the convex portions and the bottoms of the concave portions) was 0.25 mm. The stamper was used to create the irregularities using a hand press. The pressure was 3 MPa and the pressure holding time was 1 minute. The stamper was used to form the unevenness on each surface of the solid electrolyte layer green sheet. The first intermediate layer green sheet, the second intermediate layer green sheet, the first electrode green sheet, and the second electrode green sheet were also formed with the unevenness on each surface. The laminate thus formed with projections and recesses was punched out into a circle having a diameter of 20 mm.

[0084] (3) Preparation of precursor The circular punched laminate was heated to 600°C at a rate of 15°C / h in an air atmosphere, held at that temperature for 1 hour, and then cooled to room temperature. The temperature was then raised to 1600°C at a rate of 200°C / h and held at that temperature for 1 hour. This produced a precursor, a fired laminate.

[0085] (4) Manufacturing of electrode assemblies The raw material composition used to manufacture the second electrode is La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ 7 g of powder was weighed out. This powder was mixed with 31.57 g of a solution containing 21 g of isopropyl alcohol, 10.5 g of toluene, and 0.07 g of Marialim (trade name, manufactured by NOF Corporation) to prepare a slurry. This slurry was applied to the exposed surface of the second intermediate layer of the precursor to a thickness of 30 μm to form a coating. Next, the precursor together with this coating was fired, and a second electrode was formed from the coating, thereby obtaining an electrode assembly with the structure shown in FIG. 1. The firing conditions were 900°C in an air atmosphere for 1 hour. The thickness of the support layer in the obtained electrode assembly was 1300 μm, the thickness of the first electrode was 15 μm, the thickness of the first intermediate layer was 13 μm, the thickness of the solid electrolyte layer was 15 μm, the thickness of the second intermediate layer was 10 μm, and the thickness of the second electrode was 30 μm. The distance D from the top of the first convex portion to the bottom of the first concave portion in the solid electrolyte layer was 200 μm. The uneven shape was almost the same on each surface of the solid electrolyte layer. The T / D value in the solid electrolyte layer was 0.15. The coefficient of variation, defined as [standard deviation of thickness T / average thickness T], was 0.14.

[0086] Comparative Example 1 A flat electrode assembly without any irregularities was produced without using the stamper used in Example 1. Other than this, an electrode assembly was obtained in the same manner as in Example 1. The T / D value of the solid electrolyte layer of the obtained electrode assembly was 18.00.

[0087] 〔evaluation〕 The electrode assemblies obtained in the examples and comparative examples were measured for ohmic resistance R0 (Ω cm) in the measurement temperature range using the following method. 2 The results are shown in Table 1 below and Figure 15.

[0088] Ohmic resistance in the measurement temperature range R0 (Ω cm 2 ) evaluation At 700°C, 100 ccm of hydrogen was flowed as fuel gas to the fuel electrode (first electrode), and 80 ccm of nitrogen and 20 ccm of oxygen were flowed to the air electrode (second electrode). After running the battery for about half a day, during which the voltage was measured until the OCV between the electrodes stabilized, impedance measurements were performed at 100 mHz to 100 kHz.

[0089] [Table 1]

[0090] As is clear from the results shown in Table 1 and FIG. 15, the ohmic resistance R0 at the measurement temperature of 700°C was 0.28 (Ω cm) in Example 1. 2) in Comparative Example 1, while it was 0.51 (Ω·cm 2 ) and the ohmic resistance R0 of Example 1 was reduced by about 45% compared to Comparative Example 2. It can also be seen that the effect of reducing the ohmic resistance becomes more pronounced as the temperature decreases. [Explanation of symbols]

[0091] 10 Electrode assembly 11 1st electrode 13 First Middle Class 12 Second electrode 14 Second Middle Class 15 Solid electrolyte layer 15b Side 1 15a 2nd side 16 Support layer 17 Middle Class 18a First electrode side convex portion 18b First electrode side recess 19a Second electrode side convex portion 19b Second electrode side recess 20 laminate 21 Supporting Layer Green Sheet 22 First electrode green sheet 23 First Intermediate Layer Green Sheet 24 Solid electrolyte layer green sheet 25 Second Intermediate Green Sheet 30 Stamper 32 Precursors 35 Paint film

Claims

1. a first surface and a second surface located opposite the first surface; the first surface has an uneven shape including a plurality of first protrusions and a plurality of first recesses, A solid electrolyte layer made of an oxide solid electrolyte, a solid electrolyte layer, wherein a value of T / D is 0.45 or less, where D is the distance from the top of the first convex portion to the bottom of the first concave portion and T is the thickness of the solid electrolyte layer.

2. the first protrusion has a ridge shape extending along a first direction in the first surface, the first recess has a groove shape extending along a first direction in the first surface, The solid electrolyte layer according to claim 1 , wherein the first protrusions and the first recesses are arranged alternately.

3. The solid electrolyte layer according to claim 1 , wherein the first protrusions and the first recesses are alternately arranged along a first direction in the first plane and a second direction perpendicular to the first direction.

4. The solid electrolyte layer according to claim 1 , wherein the distance D is 1 μm or more and 2000 μm or less.

5. The solid electrolyte layer according to claim 1 , wherein the thickness T is 0.5 μm or more and 50 μm or less.

6. 2. The solid electrolyte layer according to claim 1, wherein a distance d from the top of a first protrusion to the top of another first protrusion adjacent to said first protrusion is 2000 μm or less.

7. The ohmic resistance of the solid electrolyte layer is R, The ohmic resistance of a flat control solid electrolyte layer made of the same material and composition as the solid electrolyte layer, having the same thickness, and not having any irregularities, is defined as R ｒｅｆ When R / R ｒｅｆ The solid electrolyte layer according to claim 1 , wherein the ratio of the ρ to the ρ is 3 / 4 or less.

8. 2. The solid electrolyte layer according to claim 1, wherein a coefficient of variation defined as [standard deviation of the thickness T / average value of the thickness T] is 0.50 or less.

9. 2. The solid electrolyte layer according to claim 1, wherein a value of D / d, which is a ratio of the distance D from the apex of a first protrusion to the distance d from the apex of another first protrusion adjacent to the first protrusion, is 1 / 100 or more.

10. The solid electrolyte layer according to claim 1 , wherein the second surface has an uneven shape having a plurality of second protrusions and a plurality of second recesses.

11. The solid electrolyte layer according to claim 10 , wherein the uneven shape of the first surface and the uneven shape of the second surface are complementary shapes.

12. An electrode assembly including a solid electrolyte layer made of an oxide solid electrolyte, and a first electrode and a second electrode respectively disposed on either side of the solid electrolyte layer, the solid electrolyte layer has a first surface and a second surface located on the opposite side thereof, the first surface having an uneven shape including a plurality of first protrusions and a plurality of first recesses, an electrode assembly, wherein a value of T / D is 0.45 or less, where D is the distance from the top of the first convex portion to the bottom of the first concave portion and T is the thickness of the solid electrolyte layer.

13. A fuel cell comprising the electrode assembly according to claim 12.

14. A steam electrolysis cell comprising the electrode assembly according to claim 12.

15. The method for producing an electrode assembly according to claim 12, a stamper is pressed against a laminate of the first electrode green sheet and the solid electrolyte layer green sheet from the side of the solid electrolyte layer green sheet to form projections and recesses on the solid electrolyte layer green sheet; The method for producing an electrode assembly includes firing the unevenly shaped laminate to obtain a fired body.

16. Applying a coating material for forming a second electrode to the uneven surface of the fired body; The method according to claim 15, further comprising baking the paint for forming the second electrode.

17. 16. The manufacturing method according to claim 15, wherein a stamper is pressed against the laminate of the first electrode green sheet, the solid electrolyte layer green sheet, and the second electrode green sheet from the side of the second electrode green sheet to impart projections and recesses to the solid electrolyte layer green sheet.

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